Car battery charging below float voltage?...

[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

 

[Peeler]

On Mon, 9 Jan 2023 09:46:15 +0000, Fredxx, the notorious, troll-feeding,
senile smartass, blathered again:


> If you do your homework, you will discover that 13.6-13.8V is considered

If you had done your homework you\'d have learnt that you shouldn\'t feed the
troll, notorious smartass!

 

[Peeler]

On Mon, 9 Jan 2023 09:46:15 +0000, Fredxx, the notorious, troll-feeding,
senile smartass, blathered again:


> If you do your homework, you will discover that 13.6-13.8V is considered

If you had done your homework you\'d have learnt that you shouldn\'t feed the
troll, notorious smartass!

 

[Peeler]

On Mon, 9 Jan 2023 09:46:15 +0000, Fredxx, the notorious, troll-feeding,
senile smartass, blathered again:


> If you do your homework, you will discover that 13.6-13.8V is considered

If you had done your homework you\'d have learnt that you shouldn\'t feed the
troll, notorious smartass!

 

[Ricky]

On Monday, January 9, 2023 at 8:57:38 PM UTC-5, Paul wrote:

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.

Why? Because it\'s safer to sit in an idling truck than to drive it somewhere??? I guess they screw up their courage to drive it back to the shop at quitting time.

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.

I don\'t think I\'ve seen anything about wanting to cover power failures. His stated objective is to handle loads that temporarily exceed the capacity of the power supplies. Even running them at 12.6V, he\'s looking to ruin a perfectly good battery that will very likely drop below his desired 11.4V if the power does fail. Being shut down and not able to calculate is very different from continuing to run, but at a voltage that produces erroneous results... without being flagged.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Monday, January 9, 2023 at 8:57:38 PM UTC-5, Paul wrote:

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.

Why? Because it\'s safer to sit in an idling truck than to drive it somewhere??? I guess they screw up their courage to drive it back to the shop at quitting time.

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.

I don\'t think I\'ve seen anything about wanting to cover power failures. His stated objective is to handle loads that temporarily exceed the capacity of the power supplies. Even running them at 12.6V, he\'s looking to ruin a perfectly good battery that will very likely drop below his desired 11.4V if the power does fail. Being shut down and not able to calculate is very different from continuing to run, but at a voltage that produces erroneous results... without being flagged.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Monday, January 9, 2023 at 8:57:38 PM UTC-5, Paul wrote:

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.

Why? Because it\'s safer to sit in an idling truck than to drive it somewhere??? I guess they screw up their courage to drive it back to the shop at quitting time.

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.

I don\'t think I\'ve seen anything about wanting to cover power failures. His stated objective is to handle loads that temporarily exceed the capacity of the power supplies. Even running them at 12.6V, he\'s looking to ruin a perfectly good battery that will very likely drop below his desired 11.4V if the power does fail. Being shut down and not able to calculate is very different from continuing to run, but at a voltage that produces erroneous results... without being flagged.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Joe]

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.

--
Joe

 

[Joe]

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.

--
Joe

 

[Joe]

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.

--
Joe

 

[Ricky]

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?

I would think a directly connected battery would be a poor choice for this arrangement. As you have indicated, the output of the battery will vary significantly with the current and the direction of the current. You seem to be worried about the battery charging, but the voltage would sag when current is being drawn.

3 kW at 12V is 250A. How much do you expect the battery to provide? I can\'t see this working very well without electronics to deal with the mismatch..

BTW, when the power supplies go into current limit mode, they are no longer regulating the voltage. You get to pick one, limit the current by letting the voltage sag, or maintain the voltage by supplying more current. You can\'t both limit the current and maintain the voltage, unless you can somehow talk the graphic cards into slowing down their calculations.

Why not add another supply? Power is not something you should skimp on if you want a reliable system.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Ricky]

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?

I would think a directly connected battery would be a poor choice for this arrangement. As you have indicated, the output of the battery will vary significantly with the current and the direction of the current. You seem to be worried about the battery charging, but the voltage would sag when current is being drawn.

3 kW at 12V is 250A. How much do you expect the battery to provide? I can\'t see this working very well without electronics to deal with the mismatch..

BTW, when the power supplies go into current limit mode, they are no longer regulating the voltage. You get to pick one, limit the current by letting the voltage sag, or maintain the voltage by supplying more current. You can\'t both limit the current and maintain the voltage, unless you can somehow talk the graphic cards into slowing down their calculations.

Why not add another supply? Power is not something you should skimp on if you want a reliable system.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Ricky]

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?

I would think a directly connected battery would be a poor choice for this arrangement. As you have indicated, the output of the battery will vary significantly with the current and the direction of the current. You seem to be worried about the battery charging, but the voltage would sag when current is being drawn.

3 kW at 12V is 250A. How much do you expect the battery to provide? I can\'t see this working very well without electronics to deal with the mismatch..

BTW, when the power supplies go into current limit mode, they are no longer regulating the voltage. You get to pick one, limit the current by letting the voltage sag, or maintain the voltage by supplying more current. You can\'t both limit the current and maintain the voltage, unless you can somehow talk the graphic cards into slowing down their calculations.

Why not add another supply? Power is not something you should skimp on if you want a reliable system.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

 

[Brian Gaff]

In my experience it would be fine, of course if the extra current charging
the battery exceeded the load for everything on the psu, you would be back
to square one if you are not careful.
These must be very power hungry cards. I would not want you electricity
bill.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
\"Commander Kinsey\" <CK1@nospam.com> wrote in message
newsp.1yhlr2cemvhs6z@ryzen.home...

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?

 

[Brian Gaff]

In my experience it would be fine, of course if the extra current charging
the battery exceeded the load for everything on the psu, you would be back
to square one if you are not careful.
These must be very power hungry cards. I would not want you electricity
bill.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
\"Commander Kinsey\" <CK1@nospam.com> wrote in message
newsp.1yhlr2cemvhs6z@ryzen.home...

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?

 

[Brian Gaff]

In my experience it would be fine, of course if the extra current charging
the battery exceeded the load for everything on the psu, you would be back
to square one if you are not careful.
These must be very power hungry cards. I would not want you electricity
bill.
Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
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\"Commander Kinsey\" <CK1@nospam.com> wrote in message
newsp.1yhlr2cemvhs6z@ryzen.home...

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?

 

[charles]

In article <20230110102818.3218a502@jrenewsid.jretrading.com>,
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.

A great many years ago, we had problems with a low voltage power supply not
delivering the right voltage. It was eventually traced to a 5A glass
enclosed fuse which had a resistance of 1 Ohm. A whole bad batch!

--
from KT24 in Surrey, England - sent from my RISC OS 4té
\"I\'d rather die of exhaustion than die of boredom\" Thomas Carlyle

 

[charles]

In article <20230110102818.3218a502@jrenewsid.jretrading.com>,
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.

A great many years ago, we had problems with a low voltage power supply not
delivering the right voltage. It was eventually traced to a 5A glass
enclosed fuse which had a resistance of 1 Ohm. A whole bad batch!

--
from KT24 in Surrey, England - sent from my RISC OS 4té
\"I\'d rather die of exhaustion than die of boredom\" Thomas Carlyle

 

[charles]

In article <20230110102818.3218a502@jrenewsid.jretrading.com>,
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.

A great many years ago, we had problems with a low voltage power supply not
delivering the right voltage. It was eventually traced to a 5A glass
enclosed fuse which had a resistance of 1 Ohm. A whole bad batch!

--
from KT24 in Surrey, England - sent from my RISC OS 4té
\"I\'d rather die of exhaustion than die of boredom\" Thomas Carlyle

 

[Rod Speed]

On Tue, 10 Jan 2023 12:57:24 +1100, Paul <nospam@needed.invalid> wrote:

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.

Or you could get real radical and get a generator for the longer
times without power and use the car battery to give you time to
start it and switch over to it.

*******

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.

A UPS and generator would do that fine with
the car battery supplying the very high 12V
demand with his unusual config.

> Your plan right now, is just plain wrong.

Not if he never get long power failures.