RAC Portable Power Station, need DC adaptor spec

If the internal lead acid battery was very flat, this is what happens. The internal resistance goes high. As it charges, it comes down to where it should be. FWIW the SLAs used on these won't supply starting current very often. Perhaps a half dozen times or so before they no longer manage the full amount. But can limp on as just a portable 12v DC supply for quite some time.

My Lidl one has a 1000 mA wall wart. I can look at its spec if you want.

Adrian C expressed precisely :

That is the usual behaviour of a completely flat lead acid battery, rather than any built in intelligence. My (not RAC) unit has an automatic charger built in, which cuts it off once the fully charged voltage is reached, but yours might not do that (look for an LED marked charged)- so it might need to be carefully matched in voltage output. It lights up as soon as powered, then goes out once fully charged and stays out until powed down and up again.

It's charger suggests it is 18v 0.75amp DC. If yours lacks the charge control built in, you need a voltage controlled PSU of around 13.8 to

It's actually marked 12 volt DC 1000mA. So must be a very nominal 12 volts. ;-)

Thanks for checking.

Something unregulated rated at anything past 12V rated at an amp or more might just fit the task, and be easier to find in the junk pile than something unregulated and small with specifically 16V stamped on it.

He'll go for that :-)

Adrian C has brought this to us :

These days battery chargers are very sophisticated things in how they treat batteries. If your friend has more than one battery to care for, an Optimate or Accumate charger might be a good idea, but they aren't cheap.

TF

A biggish transformer marked 12v lightly loaded will be supplying that and more easily. Got no worries about that (and as I said easier for me to find).

Cheers

No need to pay silly prices for a sophisticated battery charger. Lidl and Aldi in the UK both do similar ones for about 14 gbp. They pulse charge a flat battery, change to a normal charge, then switch to a maintenance one. Get the same thing with a 'name' on it and you'll pay four times as much.

Or get a decent RC charger for silly money

My Silverline 38Ah Jump starter -- and yes, unlike an awful lot of these things, it actually works and will start a 2.5 litre diesel with a flat battery -- has a charger that's marked 15v 500mA.

As the battery in the appliance seemed to be a SLA, getting maximum life out of it demands using an appropriate charger rather than a random wall-wart. I use an Accumate to keep both a SLA and a motorcycle battery in good order - I don't have any experience of the Lidl or Aldi chargers.

TF

Of course. True SLA (gel) should be charged at constant voltage. They're not so tolerant as car batteries in this respect.

These things tend to have different brand names depending on who sells them - but most are simply a wall wart with a few pennies of extra components. Usually not worth the premium price.

=A0 London SW

The Lidl /Aldi offerings are good there is no doubt, but they are never there when you want them !! You have to be on their mailing list and make a judgement to buy when they are available - and then they sit around for ages ..... until that magic moment and hey presto they do the job. Just been there this afternoon to top up a spare car battery just in case, using one of these I bought probably a year ago. Serious cold now in Edinburgh and I can see some sluggish starting coming up.

They're cheap enough to build into the car. I've done this on my 'classic'. With a waterproof mains connector under the rear bumper.

I get emails from both Aldi and Lidl showing their offers of the week. With some of them you have to get there early.

My Aldi power station seems to use a basic unstabilised wall wart. However, it seems to charge up to a reasonable voltage, then cease charging (or go to a very low current) I've been using it to power some electronics, and I've been monitoring its voltage. It seems to cut out somewhere between 13.5 and

That's because bloody market traders are queuing at the door come opening time to snag all the best stuff!

Ron

On 12/2/2010 2:01 AM Adrian C spake thus:

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...

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

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