RAC Portable Power Station, need DC adaptor spec

[Dave Plowman (News)]

In article <4cfb0d79$0$2411$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:

I'm surprised nobody has mentioned this yet in this thread, but aren't
those claims for how much current these things will deliver a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.

They vary quite a bit in price. At the cheaper end I've found they will
deliver enough current (when new) to start a car with a flat battery - but
no more than a handful of times. No lead acid battery likes having what is
efficitively (at that size) a dead short across it. And as is common with
so many of these things the battery costs more to replace than the entire
unit.

The one I have is many years old. It won't deliver enough current to start
a car, but still is ok as a self contained compressor for the tyres. And
as a convenient portable 12 volt source for testing things - it will still
supply much more current than my bench PS. And only cost 20 quid...

--
*He loves nature in spite of what it did to him.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

David Nebenzahl wrote:

On 12/5/2010 2:49 AM Dave Plowman (News) spake thus:

In article <4cfb0d79$0$2411$822641b3@news.adtechcomputers.com>, David
Nebenzahl <nobody@but.us.chickens> wrote:

I'm surprised nobody has mentioned this yet in this thread, but
aren't those claims for how much current these things will deliver
a lot of BS?

I first saw one of these power units a couple weeks ago, when my
neighbor used his to get my van started after he borrowed it and the
battery started going dead. He used it twice, successfully, to
jump-start my half-dead battery. So they do work, apparently. But his
was similarly marked (I think 300 amps). Is there any way that such a
small lead-acid battery could deliver this much juice? I'm skeptical.

They vary quite a bit in price. At the cheaper end I've found they will
deliver enough current (when new) to start a car with a flat battery - but
no more than a handful of times.

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?

Too many variables. What is the amp hour rating of the battery?
What is the internal resistance of the switch? The resistance of the
cables? The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[Dave Plowman (News)]

In article <P8SdnUBQ2eqr92HRnZ2dnUVZ_vidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm˛ cables. The resistance of the alligator clamps is more
likely the limiting factor.

The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum output.

--
*When you've seen one shopping centre you've seen a mall*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <P8SdnUBQ2eqr92HRnZ2dnUVZ_vidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

Really? My jump packs have 17 Ah batteries.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57


My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88


So, it has 24% of the rating of the truck battery which isn't
'tiny'. It is intended to start a vehicle with a run down battery, not
one with mechanical problems. The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm˛ cables. The resistance of the alligator clamps is more
likely the limiting factor.

No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.

The resistance of the starter motor? The temperature? How
clean are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum output.

BS. They all matter, if you aren't an ignorant troll.

What do you think the short circuit current of a fully charged 12V
car battery is?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[Andy Burns]

Dave Plowman (News) wrote:

Michael A. Terrell <mike.terrell@earthlink.net> wrote:

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.

Yeah, but how many minutes would your 70Ah crank for, and how many
seconds does it need to crank for (assuming there's no other problem
with the engine)?

 

[Dave Plowman (News)]

In article <o9adnUNjide7i2DRnZ2dnUVZ_s-dnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <P8SdnUBQ2eqr92HRnZ2dnUVZ_vidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

Really? My jump packs have 17 Ah batteries.

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57

My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88

So, it has 24% of the rating of the truck battery which isn't
'tiny'.

Err, you don't appear to have given the amp.hr capacity - the very thing
you mentioned.

It is intended to start a vehicle with a run down battery, not
one with mechanical problems.
The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.

Batteries? Parallel them and they become like a larger one.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm˛ cables. The resistance of the alligator clamps is more
likely the limiting factor.

No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.

The resistance of the starter motor? The temperature? How clean
are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum
output.

BS. They all matter, if you aren't an ignorant troll.

What do you think the short circuit current of a fully charged 12V
car battery is?

Are you trolling? The maker of the jump start pack claims a maximum
current. Since they can't possibly know exactly what the starter motor etc
draw is, just how is it relevant?

My point is (with experience of several jump start packs including
expensive ones) is that they will not do lots of starts of a vehicle with
a flat battery without permanent damage to the SLA. Somewhere round a
dozen or so seems to be it.

--
*Corduroy pillows are making headlines.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <o9adnUNjide7i2DRnZ2dnUVZ_s-dnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

"Dave Plowman (News)" wrote:

In article <P8SdnUBQ2eqr92HRnZ2dnUVZ_vidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.

Really? My jump packs have 17 Ah batteries.

I suppose it depends on your definition of tiny, but 17 amp.hr is a lot
smaller than any battery in any car I've owned or seen. Both my current
ones have 70 Ah types.

Gee, that's damn close to the 24% figure isn't it? 17/.24 = 70.83

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57

My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88

So, it has 24% of the rating of the truck battery which isn't
'tiny'.

Err, you don't appear to have given the amp.hr capacity - the very thing
you mentioned.

Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit. If you look at the given
spces you can get an idea though.

It is intended to start a vehicle with a run down battery, not
one with mechanical problems.
The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

I've seen someone use 12V alarm batteries to jump start a service
truck. They were rated at 7 Ah.

Batteries? Parallel them and they become like a larger one.

What is the internal resistance of the switch?

Dunno

The resistance of the
cables?

Mine has 16mm˛ cables. The resistance of the alligator clamps is more
likely the limiting factor.

No, all of it is important. If the resistance of the clamps is as
high as the leads, they will overheat since all the resistance is at the
same spot rather than distributed along the length of the cables.

The resistance of the starter motor? The temperature? How clean
are the battery clamps, and what is the resistance of the battery
cables? The resistance of the starter solenoid?

Non of which matters since the power pack makers claim a maximum
output.

BS. They all matter, if you aren't an ignorant troll.

What do you think the short circuit current of a fully charged 12V
car battery is?

Are you trolling? The maker of the jump start pack claims a maximum
current. Since they can't possibly know exactly what the starter motor etc
draw is, just how is it relevant?

It is very relevant, if you stop and think about it.

My point is (with experience of several jump start packs including
expensive ones) is that they will not do lots of starts of a vehicle with
a flat battery without permanent damage to the SLA. Somewhere round a
dozen or so seems to be it.

You keep changing the subject.
--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[David Nebenzahl]

On 12/6/2010 8:58 AM Michael A. Terrell spake thus:

"Dave Plowman (News)" wrote:

In article <P8SdnUBQ2eqr92HRnZ2dnUVZ_vidnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

[I wrote:]

So how much current do you think they're actually capable of
delivering--say with the little battery fairly fresh and fully
charged?

Too many variables. What is the amp hour rating of the battery?

Tiny in automotive terms.


Really? My jump packs have 17 Ah batteries.

Product ID: BSL1117
Cold Cranking Amps: 240
Voltage: 12
Termination: NUT & BOLT
Chemistry: SLA OR VRLA VALVE REGULATED S
Weight: 13.3
Width: 2.99
Length: 7.13
Height: 6.57


My truck uses a size 27 battery with these specs:

Product ID: MTP-27
Amps: 1000
Cranking Amps: 1000
Cold Cranking Amps: 810
Voltage: 12
Termination: A
Pro-rata Warranty: 85
Weight: 47.4
Width: 6.81
Length: 12.06
Height: 8.88


So, it has 24% of the rating of the truck battery which isn't
'tiny'. It is intended to start a vehicle with a run down battery, not
one with mechanical problems. The portable pack is designed with a
different type of battery, as well. The available current is determined
by the plate area and thickness.

OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.


--
How To Access Wikileaks

These sites are still up as of 12/3/10:

http://wikileaks.de
http://wikileaks.fi
http://wikileaks.nl
http://wikileaks.eu
http://wikileaks.pl

And these IP addresses can be used:

http://213.251.145.96/
http://88.80.13.160/

 

[Dave Plowman (News)]

In article <Cdidndz4V7nN6WDRnZ2dnUVZ_judnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

You keep changing the subject.

Think you should re-read my posts. Perhaps you addressed your questions to
the wrong person.

--
*I couldn't repair your brakes, so I made your horn louder *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <Cdidndz4V7nN6WDRnZ2dnUVZ_judnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit.

Great. So never used with the engine stopped? All car batteries in the UK
have the amp.hour marked on them. As well as max current, etc.

I have an electronic battery tester - an expensive device. This gives a
instantaneous readout of the capacity in amp.hours. If you don't know what
it should be it is fairly useless.

--
*I brake for no apparent reason.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Wild_Bill]

In the case of the Schumacher IP-55 model (12V 4Ah battery) the descriptive
term that's not been mentioned so far, is 400A Peak, for this model.

Manufacturers know that Peak is a (multi)million dollar word, whether it's
used with watts, HP, or amps.. because Peak distorts actual specifications.
Consumers love big numbers, and manufacturers know it.

With a properly rated current shunt, and a peak-reading amp meter attached,
one could determine the peak current available from such a small battery.

As Dave P points out, the number of times that a small battery can deliver
the somewhat severe duty discharge rates, is going to be a very limited
number of times.

I didn't purchase this Schumacher power pack as an emergency car battery
jump pack, but instead, only as a portable power supply.

--
Cheers,
WB
..............


"David Nebenzahl" <nobody@but.us.chickens> wrote in message
news:4cfd8cab$0$2403$822641b3@news.adtechcomputers.com...

OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

 

[Dave Plowman (News)]

In article <FNlLo.214187$zE6.76279@en-nntp-03.dc1.easynews.com>,
Wild_Bill <wb_wildbill@XSPAMyahoo.com> wrote:

As Dave P points out, the number of times that a small battery can
deliver the somewhat severe duty discharge rates, is going to be a very
limited number of times.

That was really the only point I was trying to make. The output from my
cheap one was enough to start a car on a few occasions - then not. What
the actual peak power is/was didn't much concern me.

I didn't purchase this Schumacher power pack as an emergency car battery
jump pack, but instead, only as a portable power supply.

Mine - despite being quite a few years old - is still fine for this, with
the battery holding its charge well. It also has a built in compressor, so
gets used for tyres. Slow, but does it.

It was remarkable value. Any cordless power tool of its age would have had
a dead battery long since.

--
* I like you. You remind me of when I was young and stupid

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Dave Plowman (News)]

In article <4cfd8cab$0$2403$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:

OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

I used to work in a TV production facility where some of the prog was made
in the 'studio' - some on location. So there was a fleet of small trucks
used just for this location work. That location might only be a few
minutes drive away. And the trucks left unused at other times. So by
nature many suffered from flat batteries just when needed.

The availability of cheap jump start packs was very appealing. Easy to
store and carry. But in practice, even with the low cost, weren't reliable
enough. So units were made up using a sack trolley and car battery with a
charger attached. So the same sort of idea only larger.

--
*Also too, never, ever use repetitive redundancies *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <Cdidndz4V7nN6WDRnZ2dnUVZ_judnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
Very few car batteries are given an amp our rating in the US since
they are not used without a charging circuit.

Great. So never used with the engine stopped?

Sure, but vehicles that are used that way on a regular basis can have
a dual battery system so the starter is on a separate battery. I first
installed some on a pair of large paddle boats at an amusement park in
the early '70s so they could run cart machines for the music while the
283 CID V8 engines were shut down.

All car batteries in the UK
have the amp.hour marked on them. As well as max current, etc.

What good does that do the average owner? Do they stand around bars
playing 'My dick is bigger' over car batteries?

I have an electronic battery tester - an expensive device. This gives a
instantaneous readout of the capacity in amp.hours. If you don't know what
it should be it is fairly useless.

Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic. Does your car battery tell you the discharge
rate to achieve the marked Ah rating?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <4cfd8cab$0$2403$822641b3@news.adtechcomputers.com>,
David Nebenzahl <nobody@but.us.chickens> wrote:
OK, your impeccable documentation has won me over. I withdraw my
objection; the current claims on those jump-packs (300 amps, 400 amps)
must be believable after all. I'm a little surprised, though.

I used to work in a TV production facility where some of the prog was made
in the 'studio' - some on location. So there was a fleet of small trucks
used just for this location work. That location might only be a few
minutes drive away. And the trucks left unused at other times. So by
nature many suffered from flat batteries just when needed.

The availability of cheap jump start packs was very appealing. Easy to
store and carry. But in practice, even with the low cost, weren't reliable
enough. So units were made up using a sack trolley and car battery with a
charger attached. So the same sort of idea only larger.

In the US you can find a combination battery charger & large lead
acid battery built to jump start vehicles. Garages use them, and I've
seen them at large malls. The charge can put out enough current to
start a typical vehicle but if no AC is available they use the battery.


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[Dave Plowman (News)]

In article <BsWdnYXxd-xFz2PRnZ2dnUVZ_g2dnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

I have an electronic battery tester - an expensive device. This gives
a instantaneous readout of the capacity in amp.hours. If you don't
know what it should be it is fairly useless.

Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic.

You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.

Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.

--
*Wedding dress for sale. Worn once by mistake.*

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Michael A. Terrell]

"Dave Plowman (News)" wrote:

In article <BsWdnYXxd-xFz2PRnZ2dnUVZ_g2dnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
I have an electronic battery tester - an expensive device. This gives
a instantaneous readout of the capacity in amp.hours. If you don't
know what it should be it is fairly useless.

Instantaneous? Right. It gives an WAG. Battery testers have been
around for generations. Just because they add a little electronics
doesn't make them magic.

You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.

Then explain how it can determine the Ah rating. it sounds like it
tests the battery's ESR and guesses the Ah rating.

Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.

So you can leave your headlights on for 20 hours with no problems?


--
For the last time: I am not a mad scientist, I'm just a very ticked off
scientist!!!

 

[William Sommerwerck]

I have an electronic battery tester -- an expensive device.
This gives a instantaneous readout of the capacity in Ah.
If you don't know what it should be it is fairly useless.

You cannot take an "instantaneous" reading of a cell's Ah capacity. Such a
measurement requires actually draining the battery.

 

[Dave Plowman (News)]

In article <dICdneSAm4Z_u2LRnZ2dnUVZ_qWdnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:

You don't half talk rubbish. Battery testers used to be large devices.
This is the size of a DVM. And gives an accurate readout of the overall
battery condition. Not just its voltage or how much current it can
deliver. It's invaluable for quick testing of a lead acid battery.

Then explain how it can determine the Ah rating. it sounds like it
tests the battery's ESR and guesses the Ah rating.

It doesn't 'guess' anything. It gives a pretty accurate reading. I'd
suggest you find out for yourself how they work.

Does your car battery tell you the discharge
rate to achieve the marked Ah rating?

It's also a standard in the UK. 20 hour rate.

So you can leave your headlights on for 20 hours with no problems?

So you've no clue *either* about how battery capacity is measured?

Hint. Headlights on dip (and the other lights which will be on with them)
amount to around a 12 amp load. That's with 55 watt tungsten headlights.
At a 20 hour rate that would suggest a 240 amp.hour battery just for them
still to be sort of working. But not without problems. Please try it on
your car.

--
*Succeed, in spite of management *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[William Sommerwerck]

While we're on batteries...

Yesterday whiel doing a perfunctory cleanup I came across the Canon 580EX II
flash I'd packed in a carrying case (when visiting a friend) almost a year
ago. The 2700 mAh NiMH PowerEx (MAHA) cells had not been charged since then.
When I turned the flash on, it came to full charge in less than three
seconds.

The cells measured 1.274V, 1.283V, 1.285V, and 1.286V, all higher than the
nominal 1.25V of a NiMH cell. (NiMHs generally come out of a full charge at
around 1.4V.) That's pretty good performance for a cell that's supposed to
"drop dead" within a few weeks of its last charge.

So I ask... Where did this belief that NiMH cells rapidly self-discharge
come from? I never believed it, and here's strong evidence it just isn't
true.