Car battery charger

[Steve Walker]

Our day to day car is never any trouble, but my wife was ill and didn't drive for many months at a time and I also have a kit-car, so I have have had to deal with numerous, very flat batteries. Modern intelligent chargers do refuse to charge them, but I have saved them by giving them a while on an old, basic charger, before switching them over to the intelligent one.

As an aside, the Aldi/Lidl ones are pretty good, allowing me to leave the charger on permanently to keep the kit-car battery healthy, but they have a nasty little design problem - if we have the RCD trip (too many items with input filters!) or there is a momentary drop-out or someone accidentally knocks the garage power off momentarily, they default to the off-state when power is restored. Weeks later I go into the garage and find a flat battery! I'm sure that they could either retain their state using a small amount of power from the battery or default to charging if they detect a battery when mains power is restored.

SteveW

[Newshound]

You might be better off with one of these then

starter

Even with a completely dead battery, leave it on high charge for a few minutes, then hit the boost switch and crank: will sort out even big diesels. Significantly less effort than jump leads as long as you have a mains socket handy.

Alternatively, it has enough "oomph" to charge a big battery overnight.

[thirty-six]

I cant remember, I think it was from Aldi, it is an automatic but that doesn't detract that it has difficulty getting charge into a cold battery, and I used a heat pad after the first few hours of nothingness. The battery was offf the vehicle and in the house the whole time it was connected to this device.

[Dave Plowman (News)]

When I've had this I just hook the jump start pack to the battery as well as the charger, and after a couple of minutes it can be removed.

I know what you mean, but since it has sort of logic controlled switching, might be difficult to achieve. I have one permanently fitted to the old car with a mains connector under the bumper. It would be nice if I didn't have to get at the charger after plugging in the mains, to switch it on.

[Dave Plowman (News)]

You must have a very cold house. I've not had a problem here with the car parked outside - but can't be certain about the lowest temperature it's been used at.

[Tim..]

Alas my Aldi one has just died :(

[thirty-six]

The kitchen is not usually heated and there is a slight draught through the wall, it's not ideal but we mostly get by with it. I don't believe one should have to provide special conditions to charge a battery, I'll probably leave it in the porch to charge should the problem re-occur.

-5degC and wouldn't click the solenoid.

[Steve Walker]

We don't have a jump start pack; we have three cars. Unless we really need to start one urgently, we'd just stick it on charge and use another!

The cost of discrete logic is high, so I think that many are controlled by a PIC microcontroller or equivalent. The price difference between one with a small amount of EEPROM or Flash memory that the program can access is tiny. Alternatively, the controller switching to sleep mode can drop the consumption to nA, so even a flat car battery will be able to keep the chargeing status ready for when power returns.

SteveW

[Dave Plowman (News)]

My jump start pack gets lots of use. It has a tyre compressor built in. And is much used where you just want a 12 volt supply for testing things.

[Rick]

check iStore ... probably an app for it ;-)

[David WE Roberts]

Had that happen to a friend the other week. It was, I think, a Lidl charger. I took round my trusty Tecmate AccuMate which is a slow charger and maintenance charger.

I first checked that the Lidl charger wasn't charging. I then connected the AccuMate to the battery for a minute or so to show that it would charge the battery. Tried the Lidl charger again and this time it sprang into life. The difference must have been marginal.

I have found the AccuMate very good at recovering batteries which were flat, but it does take a long time so it isn't a quick fix.

Cheers

Dave R

[Fred]

I bought one of the Maplin ones "just in case", after I read about them on usenet one winter. The advice at that time was that you had to charge them once every three months, otherwise you might find yourself in a situation where both the car and battery pack were flat at the same time! I think I read some posts that people keep them plugged into the cigar lighter socket to top them up every time they drive.

I was interested in your post about damaging the battery by charging. What is the best way to ensure the pack is ready for action without damaging it? Now the cold weather is here, I was thinking about topping-up the charge in mine, only I can't find the charger!

TIA

[Adrian Brentnall]

- well - you'll need to find the charger _first_

Having done that - plug it in to charge, but be aware that when the red light on the battery pack changes state (can't remember if it goes out or comes on..?) then the pack is charged, and it's relying on you to unplug it. Leave it connected and it'll just continue charging and destroy the battery...

Mine came with a built-in air compressor - I guess there might be some value in running the compressor to 'cycle' the battery before recharging..... but that's a long discussion (probably)

I had several of these packs, and used one for a while to run an inverter to demo my stained-glass lamps at the local open-air markets, but its capacity seemed to get lower and lower as time went on. Got the feeling that these aren't the best SLA's ever - and didn't like lots of charge / discharge cycles...

Adrian

[Bill Wright]

So what is the no-load voltage of the charger, that it can wreak such havoc?

Bill

[Adrian Brentnall]

No idea, Bill. Probably the same as the question about the Rolls Royce horsepower.... "sufficient" Just went out to look but can't find the wallwart/charger at the moment..

You'd think, that if it was specced properly, it could just 'float' the SLA 'forever' - or even, as the necessary circuitry was built in to turn a led on or off after charging then that could also operate a relay/transistor to save the battery....

Anyway - got three of the things that are all equally sickly - keep meaning to gut them to use the voltmeters on some other kit with proper chargers...

Adrian

[Dave Plowman (News)]

Assuming it has a decent battery, I doubt it would lose much in three months.

My Lidl one - ages old - switches off when charged.

[grimly4]

LAs don't, and a normal start/charge one would give you fewer than fifty cycles before it's buggered. A cheapy, less than that. I have one of the aforementioned packs and cooked the battery by accident after a few years of reliable use; however, it's a fairly decent quality one so I might replace the battery with one that will take a bit of neglect/abuse and only charge it from an Aldidl charger.

[Fred]

I don't know the Lidl one.

I bought mine from Maplin and put the manual somewhere safe where it would not get damp or oily but I can't remember where. I thought it might be easier to find a copy of the manual via google and found it here:

doesn't say that charging is automatic. In fact it has a table suggesting the number of hours of recharging based on the number of jump starts performed!

One of the other google results was this video. I didn't watch it all; it was ten minutes long and there is a second part which is another ten minutes, but the gentleman takes the unit apart and shows the charging "circuit". IIRC it is a diode and a resistor.

seems to have a collection of batteries and observes that the one fitted doesn't weigh as much as it ought but I stopped watching there.

[David WE Roberts]

I've resorted to having two batteries, and swapping them over when one gets low. Changing the battery takes a couple of minutes thanks to the battery tray design, and a slow charge takes a couple of days to get a marginal battery back up to full power.

I bought .a new battery because I thought the old one was failing but kept the old battery as backup. Now I am thinking that the old battery wasn't as bad as I thought but the way we use the car is to blame.

We only use the car for very short trips - bulk shopping and the like - or slightly longer trips to our daughter's house. In winter, with heated seats, heated screen etc. there is more load on the electrical system. So I don't think the car is having time to recharge the battery.

There may be some slow leak to earth (how do you check this with a cheap mulit-meter) or a loss of efficiency in the alternator (will have it checked on the next service) but quite probably it is just intermittent short trips which are to blame.

As we can't get the car close to the house to charge the battery in situ (it stays out on the road) then a second battery seems easier than removing the battery overnight every few weeks to top it up.

Cheers

Dave R

[Chris J Dixon]

There are further videos in the series, including comparative discharge tests, and ending up with the dismembering of a number of batteries and weighing of the contents.

I don't know where he gets his kit from, but his conclusions about the Maplin charger are hard to argue with.

Chris