Car battery charging below float voltage?...

[legg]

On Thu, 12 Jan 2023 05:36:34 -0000, \"Commander Kinsey\"
<CK1@nospam.com> wrote:

On Wed, 11 Jan 2023 14:06:17 -0000, legg <legg@nospam.magma.ca> wrote:

On Tue, 10 Jan 2023 11:03:44 -0000, \"Commander Kinsey\"
CK1@nospam.com> wrote:

On Tue, 10 Jan 2023 10:28:18 -0000, Joe <joe@jretrading.com> wrote:

On Mon, 09 Jan 2023 23:21:44 -0000
\"Commander Kinsey\" <CK1@nospam.com> wrote:

I think I might add a fuse though, I looked it up and
a battery that big will give out 8000 amps if shorted with a big
enough spanner. The cable is rated at only 400 amps so I think some
flames would result. I\'ll have to check what the resistance of a
fuse is though, don\'t want to lose a couple of tenths of a volt.

Not just the fuse, but the type and quality of fuseholder. I
occasionally deal with portable 25Ah battery boxes, fused at 10A, and
I\'ve seen a couple of cases of part-melted fuseholders. The spring
contact of the panel-mount fuseholder just isn\'t up to maintaining a
low resistance with a high-ish current over long periods.

You\'ll want a high rupturing capacity fuse, and a fuseholder that grips
around the fuse end caps fairly tightly. Don\'t be tempted to buy the
cheapest.

I used a Henley fuse, the ones they put on incoming feeds to houses in the UK. No holder, hoseclipped on, like this:
https://www.dropbox.com/s/v0z0vq3x4j9jci9/Boinc%20battery%20fuse.jpg?dl=0

Get serious. Battery terminal clamps are not expensive.
Niether are CNL or ANL automotive/marine fuses.

Hose clips are precisely what you see in a car to attach a battery for the purpose of a few hundred amp starter motor etc.

Look again. The aim of a battery connector is to provide
maximum air-free contact to the round terminal\'s surface.

Fuses that interrupt DC are different animals.

Bollocks. The voltage matters, and I\'m giving it way less then the 240V it\'s rated at.

Read more. The I^2t rating of a fuse is good only in it\'s rated
application. AC current is self-interupting, by source reversal.
DC isn\'t and will arc, potentially with explosive results.

Your illustrated clamp has obviously not run at more
than few tens of amps. At 100A you\'d be able to measure
the voltage drop and probably be able to smell it.

The clamp isn\'t carrying the current.

With such modest terminal contact, the iron clamp will
be developing the same (increasing) voltage drop as the
terminal contact degrades. Measure it.

snip

As long as the battery\'s no actually doing anything, as your
app describes, you\'ll not have to worry about it.

Happy number crunching (WCG since Y2K on 3+ machines)

RL

 

[legg]

On Thu, 12 Jan 2023 05:36:34 -0000, \"Commander Kinsey\"
<CK1@nospam.com> wrote:

On Wed, 11 Jan 2023 14:06:17 -0000, legg <legg@nospam.magma.ca> wrote:

On Tue, 10 Jan 2023 11:03:44 -0000, \"Commander Kinsey\"
CK1@nospam.com> wrote:

On Tue, 10 Jan 2023 10:28:18 -0000, Joe <joe@jretrading.com> wrote:

On Mon, 09 Jan 2023 23:21:44 -0000
\"Commander Kinsey\" <CK1@nospam.com> wrote:

I think I might add a fuse though, I looked it up and
a battery that big will give out 8000 amps if shorted with a big
enough spanner. The cable is rated at only 400 amps so I think some
flames would result. I\'ll have to check what the resistance of a
fuse is though, don\'t want to lose a couple of tenths of a volt.

Not just the fuse, but the type and quality of fuseholder. I
occasionally deal with portable 25Ah battery boxes, fused at 10A, and
I\'ve seen a couple of cases of part-melted fuseholders. The spring
contact of the panel-mount fuseholder just isn\'t up to maintaining a
low resistance with a high-ish current over long periods.

You\'ll want a high rupturing capacity fuse, and a fuseholder that grips
around the fuse end caps fairly tightly. Don\'t be tempted to buy the
cheapest.

I used a Henley fuse, the ones they put on incoming feeds to houses in the UK. No holder, hoseclipped on, like this:
https://www.dropbox.com/s/v0z0vq3x4j9jci9/Boinc%20battery%20fuse.jpg?dl=0

Get serious. Battery terminal clamps are not expensive.
Niether are CNL or ANL automotive/marine fuses.

Hose clips are precisely what you see in a car to attach a battery for the purpose of a few hundred amp starter motor etc.

Look again. The aim of a battery connector is to provide
maximum air-free contact to the round terminal\'s surface.

Fuses that interrupt DC are different animals.

Bollocks. The voltage matters, and I\'m giving it way less then the 240V it\'s rated at.

Read more. The I^2t rating of a fuse is good only in it\'s rated
application. AC current is self-interupting, by source reversal.
DC isn\'t and will arc, potentially with explosive results.

Your illustrated clamp has obviously not run at more
than few tens of amps. At 100A you\'d be able to measure
the voltage drop and probably be able to smell it.

The clamp isn\'t carrying the current.

With such modest terminal contact, the iron clamp will
be developing the same (increasing) voltage drop as the
terminal contact degrades. Measure it.

snip

As long as the battery\'s no actually doing anything, as your
app describes, you\'ll not have to worry about it.

Happy number crunching (WCG since Y2K on 3+ machines)

RL

 

[legg]

On Thu, 12 Jan 2023 05:36:34 -0000, \"Commander Kinsey\"
<CK1@nospam.com> wrote:

On Wed, 11 Jan 2023 14:06:17 -0000, legg <legg@nospam.magma.ca> wrote:

On Tue, 10 Jan 2023 11:03:44 -0000, \"Commander Kinsey\"
CK1@nospam.com> wrote:

On Tue, 10 Jan 2023 10:28:18 -0000, Joe <joe@jretrading.com> wrote:

On Mon, 09 Jan 2023 23:21:44 -0000
\"Commander Kinsey\" <CK1@nospam.com> wrote:

I think I might add a fuse though, I looked it up and
a battery that big will give out 8000 amps if shorted with a big
enough spanner. The cable is rated at only 400 amps so I think some
flames would result. I\'ll have to check what the resistance of a
fuse is though, don\'t want to lose a couple of tenths of a volt.

Not just the fuse, but the type and quality of fuseholder. I
occasionally deal with portable 25Ah battery boxes, fused at 10A, and
I\'ve seen a couple of cases of part-melted fuseholders. The spring
contact of the panel-mount fuseholder just isn\'t up to maintaining a
low resistance with a high-ish current over long periods.

You\'ll want a high rupturing capacity fuse, and a fuseholder that grips
around the fuse end caps fairly tightly. Don\'t be tempted to buy the
cheapest.

I used a Henley fuse, the ones they put on incoming feeds to houses in the UK. No holder, hoseclipped on, like this:
https://www.dropbox.com/s/v0z0vq3x4j9jci9/Boinc%20battery%20fuse.jpg?dl=0

Get serious. Battery terminal clamps are not expensive.
Niether are CNL or ANL automotive/marine fuses.

Hose clips are precisely what you see in a car to attach a battery for the purpose of a few hundred amp starter motor etc.

Look again. The aim of a battery connector is to provide
maximum air-free contact to the round terminal\'s surface.

Fuses that interrupt DC are different animals.

Bollocks. The voltage matters, and I\'m giving it way less then the 240V it\'s rated at.

Read more. The I^2t rating of a fuse is good only in it\'s rated
application. AC current is self-interupting, by source reversal.
DC isn\'t and will arc, potentially with explosive results.

Your illustrated clamp has obviously not run at more
than few tens of amps. At 100A you\'d be able to measure
the voltage drop and probably be able to smell it.

The clamp isn\'t carrying the current.

With such modest terminal contact, the iron clamp will
be developing the same (increasing) voltage drop as the
terminal contact degrades. Measure it.

snip

As long as the battery\'s no actually doing anything, as your
app describes, you\'ll not have to worry about it.

Happy number crunching (WCG since Y2K on 3+ machines)

RL

 

[a a]

On Monday, 9 January 2023 at 19:20:04 UTC+1, a a wrote:

On Monday, 9 January 2023 at 10:46:23 UTC+1, Fredxx wrote:
On 09/01/2023 04:37, Commander Kinsey wrote:
I have 8 computers with 15 graphics cards running science projects. The
graphics cards run from 12 volts, adding up to a lot of current between
them. I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range. Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily. The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full. If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it? Or does it require a float voltage
of 13.2 volts or more?
If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.
you are wrong
read caption at battery:

Charging voltage

Standby use: 13.5V - 13.8 V
Cycle use: 14.4V - 15.0V
Charging current 5,40 A max ( 18Ah gel battery)

--you are wrong
---read caption at battery:

--Charging voltage

--Standby use: 13.5V - 13.8 V
--Cycle use: 14.4V - 15.0V
--Charging current 5,40 A max ( 18Ah gel battery)

never delete the right answer

 

[a a]

On Monday, 9 January 2023 at 19:20:04 UTC+1, a a wrote:

On Monday, 9 January 2023 at 10:46:23 UTC+1, Fredxx wrote:
On 09/01/2023 04:37, Commander Kinsey wrote:
I have 8 computers with 15 graphics cards running science projects. The
graphics cards run from 12 volts, adding up to a lot of current between
them. I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range. Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily. The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full. If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it? Or does it require a float voltage
of 13.2 volts or more?
If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.
you are wrong
read caption at battery:

Charging voltage

Standby use: 13.5V - 13.8 V
Cycle use: 14.4V - 15.0V
Charging current 5,40 A max ( 18Ah gel battery)

--you are wrong
---read caption at battery:

--Charging voltage

--Standby use: 13.5V - 13.8 V
--Cycle use: 14.4V - 15.0V
--Charging current 5,40 A max ( 18Ah gel battery)

never delete the right answer

 

[a a]

On Monday, 9 January 2023 at 19:20:04 UTC+1, a a wrote:

On Monday, 9 January 2023 at 10:46:23 UTC+1, Fredxx wrote:
On 09/01/2023 04:37, Commander Kinsey wrote:
I have 8 computers with 15 graphics cards running science projects. The
graphics cards run from 12 volts, adding up to a lot of current between
them. I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range. Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily. The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full. If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it? Or does it require a float voltage
of 13.2 volts or more?
If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.
you are wrong
read caption at battery:

Charging voltage

Standby use: 13.5V - 13.8 V
Cycle use: 14.4V - 15.0V
Charging current 5,40 A max ( 18Ah gel battery)

--you are wrong
---read caption at battery:

--Charging voltage

--Standby use: 13.5V - 13.8 V
--Cycle use: 14.4V - 15.0V
--Charging current 5,40 A max ( 18Ah gel battery)

never delete the right answer

 

[Peeler]

On Thu, 12 Jan 2023 11:17:37 -0500, legg, another brain dead troll-feeding
senile ASSHOLE, babbled:


> Look again.

You mean, \"troll some more\", you brain dead troll-feeding senile ASSHOLE!

 

[Peeler]

On Thu, 12 Jan 2023 11:17:37 -0500, legg, another brain dead troll-feeding
senile ASSHOLE, babbled:


> Look again.

You mean, \"troll some more\", you brain dead troll-feeding senile ASSHOLE!

 

[Peeler]

On Thu, 12 Jan 2023 11:17:37 -0500, legg, another brain dead troll-feeding
senile ASSHOLE, babbled:


> Look again.

You mean, \"troll some more\", you brain dead troll-feeding senile ASSHOLE!

 

[Fredxx]

On 09/01/2023 04:37, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects.  The
graphics cards run from 12 volts, adding up to a lot of current between
them.  I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range.  Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily.  The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full.  If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it?  Or does it require a float voltage
of 13.2 volts or more?

If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.

 

[Fredxx]

On 09/01/2023 04:37, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects.  The
graphics cards run from 12 volts, adding up to a lot of current between
them.  I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range.  Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily.  The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full.  If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it?  Or does it require a float voltage
of 13.2 volts or more?

If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.

 

[Fredxx]

On 09/01/2023 04:37, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects.  The
graphics cards run from 12 volts, adding up to a lot of current between
them.  I have three 1kW power supplies connected to a big bus bar and
have set those power supplies to 12.6 volts, as the graphics cards
expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest
voltage drop not to make it fall outside that range.  Currently I\'m
close to the limit of the power supplies, and since the current draw of
the graphics cards is uneven, I thought it would be a good idea to add a
car battery (actually a 130 Ah leisure battery) to the bus bars, to help
out if there was too much current draw momentarily.  The power supplies
are current limited so don\'t mind if I try to draw too much, they will
just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is
the voltage the battery sits at with nothing connected to it when it\'s
95% full.  If the battery were to supply a fair amount of current for a
while and become a little discharged, would it manage to charge back up
with only 12.6 volts supplied to it?  Or does it require a float voltage
of 13.2 volts or more?

If you do your homework, you will discover that 13.6-13.8V is considered
a float charging voltage.

A voltage of 13V is considered a charge maintenance voltage.

Anything less than 13V won\'t supply any charge.

You might like to rethink this.

 

[Fred Bloggs]

On Sunday, January 8, 2023 at 11:37:13 PM UTC-5, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects. The graphics cards run from 12 volts, adding up to a lot of current between them.. I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range. Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily. The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is the voltage the battery sits at with nothing connected to it when it\'s 95% full. If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12..6 volts supplied to it? Or does it require a float voltage of 13.2 volts or more?

How do you intend to disconnect the battery from the graphics cards when the system is shut down?

 

[Fred Bloggs]

On Sunday, January 8, 2023 at 11:37:13 PM UTC-5, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects. The graphics cards run from 12 volts, adding up to a lot of current between them.. I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range. Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily. The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is the voltage the battery sits at with nothing connected to it when it\'s 95% full. If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12..6 volts supplied to it? Or does it require a float voltage of 13.2 volts or more?

How do you intend to disconnect the battery from the graphics cards when the system is shut down?

 

[Fred Bloggs]

On Sunday, January 8, 2023 at 11:37:13 PM UTC-5, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects. The graphics cards run from 12 volts, adding up to a lot of current between them.. I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range. Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily. The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts? This is the voltage the battery sits at with nothing connected to it when it\'s 95% full. If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12..6 volts supplied to it? Or does it require a float voltage of 13.2 volts or more?

How do you intend to disconnect the battery from the graphics cards when the system is shut down?

 

[Paul]

On 1/10/2023 11:52 PM, Commander Kinsey wrote:

On Wed, 11 Jan 2023 04:10:27 -0000, Jasen Betts <usenet@revmaps.no-ip.org> wrote:

On 2023-01-09, Commander Kinsey <CK1@nospam.com> wrote:
I have 8 computers with 15 graphics cards running science projects.  The graphics cards run from 12 volts, adding up to a lot of current between them.  I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range.  Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily.  The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is the voltage the battery sits at with nothing connected to it when it\'s 95% full.  If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12.6 volts supplied to it?  Or does it require a float voltage of 13.2 volts or more?

the voltage is too low for a 6 cell lead-acid battery, and too high
for a 5 cell battery.  maybe try supercapacitors instead.

Why is it too low?  12.6V means it\'s almost full.

You have to read this very carefully. One reading, is not enough.

https://batteryuniversity.com/article/bu-403-charging-lead-acid

Lead acid batteries can sulphate or they can suffer plate corrosion.

They are quite sensitive to how they are treated, over long
periods of time.

My APC 650 battery lasted for 11 years, the first one.
At changeover, I verified the float was 13.5V .

The replacement RBC4, with an APC sticker on it, wore out
in only three years. Three of six cells were shorted, so
only half of the normal voltage was evident. When this
happens, the chassis of the UPS gets warm, which is your
warning that something bad is happening.

Obviously, the characteristics of that \"new\" battery are not
a match for the control settings on the APC 650 circuit board.
But if the battery does not admit to not being an RBC4,
it is pretty hard to guess at what setting would make a
new battery last 11 years.

When the 11 year battery failed, it had full terminal voltage,
but little amp-hour capacity left.

14.4V End of charge cycle on a fully charged battery.

12.6V The terminal voltage one day after a fully charged lead acid battery
is allowed to settle. In such a case, no bias is being applied to the
battery. You can\'t leave it sitting forever like this.

13.5V The float voltage used for battery maintenance (as measured on my UPS)
The UPS seems to be applying this all the time.

12.0V You have to decide when to stop discharging a lead-acid battery.
A leisure battery might be OK down to 11.0V, but then maybe
only one hundred charge/discharge cycles is the result. Automotive
batteries, you cannot be too greedy, during discharge, and stopping
at a higher value is advised.

When you start a car, the 12.6V battery drops to around 9.5V (at terminals)
while 150 amperes flows to the starter motor. Some battery chemistries
are stiffer than others. This is not a violation of anything (it does
not mean a cell is reverse biased necessarily), since the condition is
transient for the battery. If the battery was no longer stiff and had a
high impedance, the terminal voltage would be a lot lower and you would
not get the 150 amperes. It could not maintain such a load (150 amps)
for long anyway. The conditions in this example, were measured on my
car, using a clamp-on DC ammeter with peak hold, and a multimeter
on DC volts with peak hold. A healthy starter motor might have been
100 amps.

Paul

 

[Paul]

On 1/10/2023 11:52 PM, Commander Kinsey wrote:

On Wed, 11 Jan 2023 04:10:27 -0000, Jasen Betts <usenet@revmaps.no-ip.org> wrote:

On 2023-01-09, Commander Kinsey <CK1@nospam.com> wrote:
I have 8 computers with 15 graphics cards running science projects.  The graphics cards run from 12 volts, adding up to a lot of current between them.  I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range.  Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily.  The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is the voltage the battery sits at with nothing connected to it when it\'s 95% full.  If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12.6 volts supplied to it?  Or does it require a float voltage of 13.2 volts or more?

the voltage is too low for a 6 cell lead-acid battery, and too high
for a 5 cell battery.  maybe try supercapacitors instead.

Why is it too low?  12.6V means it\'s almost full.

You have to read this very carefully. One reading, is not enough.

https://batteryuniversity.com/article/bu-403-charging-lead-acid

Lead acid batteries can sulphate or they can suffer plate corrosion.

They are quite sensitive to how they are treated, over long
periods of time.

My APC 650 battery lasted for 11 years, the first one.
At changeover, I verified the float was 13.5V .

The replacement RBC4, with an APC sticker on it, wore out
in only three years. Three of six cells were shorted, so
only half of the normal voltage was evident. When this
happens, the chassis of the UPS gets warm, which is your
warning that something bad is happening.

Obviously, the characteristics of that \"new\" battery are not
a match for the control settings on the APC 650 circuit board.
But if the battery does not admit to not being an RBC4,
it is pretty hard to guess at what setting would make a
new battery last 11 years.

When the 11 year battery failed, it had full terminal voltage,
but little amp-hour capacity left.

14.4V End of charge cycle on a fully charged battery.

12.6V The terminal voltage one day after a fully charged lead acid battery
is allowed to settle. In such a case, no bias is being applied to the
battery. You can\'t leave it sitting forever like this.

13.5V The float voltage used for battery maintenance (as measured on my UPS)
The UPS seems to be applying this all the time.

12.0V You have to decide when to stop discharging a lead-acid battery.
A leisure battery might be OK down to 11.0V, but then maybe
only one hundred charge/discharge cycles is the result. Automotive
batteries, you cannot be too greedy, during discharge, and stopping
at a higher value is advised.

When you start a car, the 12.6V battery drops to around 9.5V (at terminals)
while 150 amperes flows to the starter motor. Some battery chemistries
are stiffer than others. This is not a violation of anything (it does
not mean a cell is reverse biased necessarily), since the condition is
transient for the battery. If the battery was no longer stiff and had a
high impedance, the terminal voltage would be a lot lower and you would
not get the 150 amperes. It could not maintain such a load (150 amps)
for long anyway. The conditions in this example, were measured on my
car, using a clamp-on DC ammeter with peak hold, and a multimeter
on DC volts with peak hold. A healthy starter motor might have been
100 amps.

Paul

 

[Paul]

On 1/10/2023 11:52 PM, Commander Kinsey wrote:

On Wed, 11 Jan 2023 04:10:27 -0000, Jasen Betts <usenet@revmaps.no-ip.org> wrote:

On 2023-01-09, Commander Kinsey <CK1@nospam.com> wrote:
I have 8 computers with 15 graphics cards running science projects.  The graphics cards run from 12 volts, adding up to a lot of current between them.  I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range.  Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily.  The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is the voltage the battery sits at with nothing connected to it when it\'s 95% full.  If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12.6 volts supplied to it?  Or does it require a float voltage of 13.2 volts or more?

the voltage is too low for a 6 cell lead-acid battery, and too high
for a 5 cell battery.  maybe try supercapacitors instead.

Why is it too low?  12.6V means it\'s almost full.

You have to read this very carefully. One reading, is not enough.

https://batteryuniversity.com/article/bu-403-charging-lead-acid

Lead acid batteries can sulphate or they can suffer plate corrosion.

They are quite sensitive to how they are treated, over long
periods of time.

My APC 650 battery lasted for 11 years, the first one.
At changeover, I verified the float was 13.5V .

The replacement RBC4, with an APC sticker on it, wore out
in only three years. Three of six cells were shorted, so
only half of the normal voltage was evident. When this
happens, the chassis of the UPS gets warm, which is your
warning that something bad is happening.

Obviously, the characteristics of that \"new\" battery are not
a match for the control settings on the APC 650 circuit board.
But if the battery does not admit to not being an RBC4,
it is pretty hard to guess at what setting would make a
new battery last 11 years.

When the 11 year battery failed, it had full terminal voltage,
but little amp-hour capacity left.

14.4V End of charge cycle on a fully charged battery.

12.6V The terminal voltage one day after a fully charged lead acid battery
is allowed to settle. In such a case, no bias is being applied to the
battery. You can\'t leave it sitting forever like this.

13.5V The float voltage used for battery maintenance (as measured on my UPS)
The UPS seems to be applying this all the time.

12.0V You have to decide when to stop discharging a lead-acid battery.
A leisure battery might be OK down to 11.0V, but then maybe
only one hundred charge/discharge cycles is the result. Automotive
batteries, you cannot be too greedy, during discharge, and stopping
at a higher value is advised.

When you start a car, the 12.6V battery drops to around 9.5V (at terminals)
while 150 amperes flows to the starter motor. Some battery chemistries
are stiffer than others. This is not a violation of anything (it does
not mean a cell is reverse biased necessarily), since the condition is
transient for the battery. If the battery was no longer stiff and had a
high impedance, the terminal voltage would be a lot lower and you would
not get the 150 amperes. It could not maintain such a load (150 amps)
for long anyway. The conditions in this example, were measured on my
car, using a clamp-on DC ammeter with peak hold, and a multimeter
on DC volts with peak hold. A healthy starter motor might have been
100 amps.

Paul

 

[Paul]

On 1/8/2023 11:37 PM, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects.  The graphics cards run from 12 volts, adding up to a lot of current between them.  I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range.  Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily.  The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is the voltage the battery sits at with nothing connected to it when it\'s 95% full.  If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12.6 volts supplied to it?  Or does it require a float voltage of 13.2 volts or more?

Power outages, have statistics.

Here, a power outage is 1 second. Or a power outage is 2+ hours.
In fact, the long power outages have been lengthening in time,
in the last decade. One lasted a day. The last one was two days plus.
The power company is on a safety kick, where power repair trucks
sit idle on the street, with staff sitting on their hands.

As such, a single leisure battery and three 80 ampere loads, that\'s
a huge load. And the 130 Ah leisure battery, you\'re not really supposed
to be running those flat. This means you have well-less than an
hour of capacity. How many BOINC units can you do in half an hour ?
Is it worth XXX pounds currency, for the privilege of doing
so few units ?

With a UPS, the objective is to allow clean shutdown of all
computers. You could buy a consumer UPS for each 1kW supply.
Maybe this would give you 8 minutes holdup time, or 4 minutes
holdup time. You would need to send the shutdown signal,
to all the computers, so they would begin shutting down.

You cannot buy the lowest tier of UPS either, if you
really plan on handling a full kW load. There are some
really awful UPS that will smoke if you do that.

A commercial UPS, a double conversion rack mount, might have the
power rating to run your entire computer room. But, you will
be charged a commercial rate for such a beast. In your IT days,
you might have had such rackmount UPS in the server room. They
seem to be quite common. As double conversion, they have a
cooling fan that runs constantly (unlike a consumer SPS which
runs cool until it flips to battery).

Buying three UPS, would be an intermediate solution, compared to
buying a Tesla Powerwall (price has gone up 2x since introduction),
or some of the less well thought out consumer \"battery bank\" thingies.
There is one product, which does not even work as well as a
double conversion UPS, which would be cheaper than a powerwall,
and they\'re about 1kWh each.

*******

The video card uses 3.3V and 12V

The motherboard uses 3.3,5,12,-12,+5VSB.

The leisure battery only has one voltage, not
six or seven voltages.

You need to pick the logically correct point for
backup powering this mess.

Your plan right now, is just plain wrong.

Paul

 

[Paul]

On 1/8/2023 11:37 PM, Commander Kinsey wrote:

I have 8 computers with 15 graphics cards running science projects.  The graphics cards run from 12 volts, adding up to a lot of current between them.  I have three 1kW power supplies connected to a big bus bar and have set those power supplies to 12.6 volts, as the graphics cards expect 11.4 to 12.6 volts, so I\'m playing safe and allowing the biggest voltage drop not to make it fall outside that range.  Currently I\'m close to the limit of the power supplies, and since the current draw of the graphics cards is uneven, I thought it would be a good idea to add a car battery (actually a 130 Ah leisure battery) to the bus bars, to help out if there was too much current draw momentarily.  The power supplies are current limited so don\'t mind if I try to draw too much, they will just limit the current.

My question is, is it ok to have the battery sat at 12.6 volts?  This is the voltage the battery sits at with nothing connected to it when it\'s 95% full.  If the battery were to supply a fair amount of current for a while and become a little discharged, would it manage to charge back up with only 12.6 volts supplied to it?  Or does it require a float voltage of 13.2 volts or more?

Power outages, have statistics.

Here, a power outage is 1 second. Or a power outage is 2+ hours.
In fact, the long power outages have been lengthening in time,
in the last decade. One lasted a day. The last one was two days plus.
The power company is on a safety kick, where power repair trucks
sit idle on the street, with staff sitting on their hands.

As such, a single leisure battery and three 80 ampere loads, that\'s
a huge load. And the 130 Ah leisure battery, you\'re not really supposed
to be running those flat. This means you have well-less than an
hour of capacity. How many BOINC units can you do in half an hour ?
Is it worth XXX pounds currency, for the privilege of doing
so few units ?

With a UPS, the objective is to allow clean shutdown of all
computers. You could buy a consumer UPS for each 1kW supply.
Maybe this would give you 8 minutes holdup time, or 4 minutes
holdup time. You would need to send the shutdown signal,
to all the computers, so they would begin shutting down.

You cannot buy the lowest tier of UPS either, if you
really plan on handling a full kW load. There are some
really awful UPS that will smoke if you do that.

A commercial UPS, a double conversion rack mount, might have the
power rating to run your entire computer room. But, you will
be charged a commercial rate for such a beast. In your IT days,
you might have had such rackmount UPS in the server room. They
seem to be quite common. As double conversion, they have a
cooling fan that runs constantly (unlike a consumer SPS which
runs cool until it flips to battery).

Buying three UPS, would be an intermediate solution, compared to
buying a Tesla Powerwall (price has gone up 2x since introduction),
or some of the less well thought out consumer \"battery bank\" thingies.
There is one product, which does not even work as well as a
double conversion UPS, which would be cheaper than a powerwall,
and they\'re about 1kWh each.

*******

The video card uses 3.3V and 12V

The motherboard uses 3.3,5,12,-12,+5VSB.

The leisure battery only has one voltage, not
six or seven voltages.

You need to pick the logically correct point for
backup powering this mess.

Your plan right now, is just plain wrong.

Paul