RAC Portable Power Station, need DC adaptor spec

[Dave Plowman (News)]

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.

 

[David Nebenzahl]

[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.


--
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http://wikileaks.pl

And these IP addresses can be used:

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

 

[Dave Plowman (News)]

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.

 

[Dave Plowman (News)]

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.

 

[Dave Plowman (News)]

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.

 

[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)]

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.

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.

 

[Dave Plowman (News)]

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

I dunno how it actually achieves this, but in practice it's what it does.
And is pretty accurate if you check it against doing an actual discharge.
Nor does it need the battery to be fully charged to test it.

I've used it on many batteries of different capacities - and on known
good ones gives a readout within something like 5% of the stated capacity.
Unless the charge is too low for it to work.

For me, it's invaluable.

 

[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.

 

[Dave Plowman (News)]

You still use tungsten headlights in Europe? Halogen are standard in
the US. My truck uses 65 W:

You certainly show your ignorance with every post. 'Halogen' is the inert
gas used in some types of filament lamps. The filament is still likely
tungsten.

However, none of that makes a difference in this context. A 55 watt (EU
spec) headlight is a 55 watt headlight.

BTW, my car has HID units. Far more efficient than those ancient 'halogen'
lights. 35 watts produces more light than your 65 watt whatever. They're
pretty well the norm in the UK on new cars above base spec.

 

[William Sommerwerck]

BTW, my car has HID units. Far more efficient than those ancient

"halogen" lights. 35 watts produces more light than your 65 watt
whatever. They're pretty well the norm in the UK on new cars
above base spec.

Are these those blinding-blue bulbs that rip retinas with flesh-frying
force? (Note quadruple use of alliteration.)

 

[Dave Plowman (News)]

Are these those blinding-blue bulbs that rip retinas with flesh-frying
force? (Note quadruple use of alliteration.)

Dunno. Mine have a colour temperature quite close to filament lamps and a
very sharp cut-off beam pattern. The car also has self levelling
suspension. The earliest versions of them did appear quite 'blue'. Rather
like most 'white' LEDs. ;-)

 

[Dave Plowman (News)]

So? Just because they use that spec in a backwards, anti-engineering
country is no reason for anyone else to.

Crikey. Where did that come from? Hate just admitting your mistake?

Sigh. Still can't stick to what you post, can you? First you claim
55 W tungsten, then it's 35 W HID.

Crikey again. Do you actually think before posting?

No wonder you believe the hype about
your magic toy battery tester. The actual Ah rating is determined by
it's use. That 20 Ah rating is only one curve, of many. If you stuck
to it, you couldn't start the vehicle's engine with it. you couldn't use
most car radios without exceeding the proper discharge rate. You
dismiss the total starting circuit resistance as nothing.

More bollocks. Amp hour and the discharge rate are simply a standard way
of *measuring* that parameter. Other battery parameters are given
separately. For one who claims to be an engineer, this shouldn't need
explaining.

As far as HID lamps, they can be seen a lot further away, but most US
drivers don't like them. You get a brighter spot, but don't light the
sides of the road well enough to see animals or people along the side of
a road until it's too late. There are a lot of very long, and high
speed roads in the US where you need that extra illumination.

You've never experienced decent HID lamps. With proper reflector etc
design they can provide any beam pattern you want. Mine produce as even
illumination as you could possibly want - no high spots at all. They also
have a 'spike' at the nearside which illuminates the side of the road
rather further than the main part of the beam. They only provide the dip
beam - the high beam is by ordinary quartz halogen units, which are in
addition to the dips.

 

[William Sommerwerck]

You cannot take an "instantaneous" reading of a cell's Ah capacity.

I used to think that, but Google gave many hits like this
http://www.actmeters.com/nsi/33-Battery-Capacity-Tester.php

A fascinating product, but I still don't see how it works.

The only method "obvious" (to me) would be to short the cell for a fraction
of a second, and use the measured current to calculate the internal
resistance. * This, in turn, could be used to estimate the cell's Ah
capacity. But this assumes there's a direct correlation of the resistance
with the cell's capacity, regardless of its age or charge condition. Is
there?

* This is the way Microsoft Hardware tested mouse batteries -- but to see
whether they were primary or secondary, and whether the latter were
"defective". The capacity was of little concern.

 

[Dave Plowman (News)]

A fascinating product, but I still don't see how it works.

The only method "obvious" (to me) would be to short the cell for a
fraction of a second, and use the measured current to calculate the
internal resistance. * This, in turn, could be used to estimate the
cell's Ah capacity. But this assumes there's a direct correlation of the
resistance with the cell's capacity, regardless of its age or charge
condition. Is there?

I *think* that's the way it works. The crock clips have very sharp 'pins'
to ensure a good contact with the battery terminals.

But having used mine on a variety of sized batteries it really does seem
to give a good indication as to the condition rather than just the charge
state of a battery. In other words if it says a fully charged battery has
the capacity (in amp.hrs) as stated on the battery it is good. Works on
batteries from 1.8 - 200 Ah. If it gives a reading of less than 65% of
that figure, the battery should be replaced. The claim is it simulates a
20 hour test in 6 seconds.

It's no cheap DVM, though. Cost almost 200 gbp - and came with a hand
written calibration certificate. Most decent battery sellers will have
something similar. Even Halfords. ;-)

 

[Dave Plowman (News)]

The US finally adopted EU vehicle lighting standards after US lighting
engineers spent some 20 years pressuring to be able to use the safer,
more effective, and more modern EU standards in the US, against the
US car manufacturers who didn't want the expense of redesigning their
ancient lighting systems and didn't want competition from foreign
lighting manufacturers.

Older readers may remember Lucas spot light adverts from the '60s - 'are
too powerful for use in some US states'

By the prince of darkness. ;-)

 

[Meat Plow]

So, the Philips and Osram lamps are US made?

Who wrote this?

"You still use tungsten headlights in Europe? Halogen are standard in
the US. My truck uses 65 W:"

 

[William Sommerwerck]

The only method "obvious" (to me) would be to short the cell for a

I *think* that's the way it works. The crock clips have very sharp 'pins'
to ensure a good contact with the battery terminals.

But having used mine on a variety of sized batteries it really does seem
to give a good indication as to the condition rather than just the charge
state of a battery. In other words if it says a fully charged battery has
the capacity (in amp.hrs) as stated on the battery it is good. Works
on batteries from 1.8 - 200 Ah. If it gives a reading of less than 65% of
that figure, the battery should be replaced. The claim is it simulates a
20 hour test in 6 seconds.

Have you checked the results against something like the MAHA C9000, which
actually drains the cell?

 

[Dave Plowman (News)]

From the current 'Brit Engineering kaput!' thread on
where they are discussing why all
engineering in England has gone to crap. From the public's attitude
towards engineering, stupid HR staff and brain drain where people with
talent leave England to work elsewhere.

You really need to see what UK groups say about the US. ;-)

Or perhaps you feel it's not in some similar form of 'decline'? If so, get
your head out of your arse and look around you. At all the Chinese etc
made consumer goods. Same as here. GM bankrupt yet again - despite having
one of the largest markets on its doorstep. Etc.

I'm no 'my country right or wrong' type. I'll leave that to you.

Yes, unlike you. You keep comparing apples to crabapples.

Sigh. You're the one doing the comparing - and getting it wrong.

I know how the damn 'standard' works. It works even better if it has
a relevant base measurement. Starting a vehicle is a completely
different function from a standby power application. Other than
starting the vehicle, little current is drawn from a car's battery if
the charging system works properly. Therfore a '20 Ah rating' is not
the proper standard. That is why the US rates a car battery by CCA. A
worst case condition for starting in cold weather when an engine is
tight and the lubricants are stiff.

Who are you trying to educate? I'm well aware of the likely loading on a
car battery. UK batteries also give all that information - the Ah one is
in addition.

Your miracle tester won't find a
failing batery. I've had several show no signs of trouble that
developed an open internal connection when you hit the key. Your DMM
sized miracle box won't find that and give warning, but the old
controlled discharge testers will.

You really need to do some research before being so certain. Because
you're wrong. My tester will show up a faulty cell - either high impedance
or shorted. Your prehistoric 'controlled discharge' (just an ammeter)
won't - unless you also do other measurements. It also needs skill and
care to use. But perhaps you've never seen a battery blow apart when
having a high discharge test done? I have. My tester doesn't apply the
load until after it is connected.

Most of what I've seen are on imported cars. They tend to blind
oncoming traffic.

I have no idea of the construction and use regulations in the US. If they
are only fitted to imports, it shows just how far behind the times Detroit
is. FWIW badly set filament lights can dazzle too. Or ones with just plain
poor optical design. HID lamps are much more efficient. If they are
designed to the same light output as 'halogen' you benefit from less
energy use. If similar savings are made elsewhere in a car, you specify a
smaller alternator and cable sizes. Etc.

 

[Dave Plowman (News)]

Have you checked the results against something like the MAHA C9000, which
actually drains the cell?

No. I'm only really concerned if a battery is fit for further service.
With a quick check. Which this device does pretty well.