Cyclic Battery Chargers

There is nothing magical about a battery float charger that can be left permanently connected, and all the ones on offer are *extremely* poor value for money, given that with all such things the cost is in the low voltage power supply (transformer, etc) rather than the electronics.

If they cost 10 quid or so, that would be plenty.

Far better to buy a decent general purpose charger that offers float charging - or a maintenance charge - as well. It will cost about the same. You might have to add a suitable plug to it, and a matching one to the vehicle to make it more convenient to use, though.

Any idea where to get one for a decent price? A relative has a camper van that's laid up most of (all of?) the time and has to keep buying new batteries. His idea of maintenance would be starting it and letting it idle for an half hour. I've managed to convince him thatt's not a good idea at least.

Well, the major makers like Sealey etc should be worth a look - or even Halfords.

Personally, I'd just use a good charger on a timeswitch for a couple of hours a week. Lead acid batteries are very tolerant - they just don't like being fully discharged.

I've never seen such a thing for less than an insane price.

I made one of these years ago. Basically recycled battery charger parts for case, transformer and rectifier, it had half-a-dozen separate outputs to float a whole shelf of batteries and each channel used a simple 2 or 3 transistor circuit from an Elektor article. It was even temperature compensated.

-- Die Gotterspammerung - Junkmail of the Gods

I believe last month's Volksworld magazine had a solar powered one in their new gizzmo section.

-- athomik

Unless it's very large it's unlikely to produce a useful output in a UK winter. I seem to remember someone calculating something about the size of a car sunroof would be needed to produce enough to replace the current taken by a car alarm and radio memory etc. Those dash top thingies haven't a chance.

I've got one of the Draper ones (Battery Master) - see

Best Regards John McCabe

To reply by email replace 'nospam' with 'assen'

Hmmmm, not much good in a garage, in winter...

J.

You could always leave the lights on.

Only 12 volts though, some classics and before are still on 6 volts.......

Pezzack

You don't still have the circuit do you Andy? I've just blown up my charger (and battery - forgot it was there on charge while grinding :-( - but I do have some juicy transformers in a cupboard...

Yes.

Finding it is quite another matter !

I don't even have the infamous gadget - it's at my dad's. I'd like to make another one myself, but it's that awkward "finding" thing.

I imagine a bit of Google and a couple of op-amps would provide a less elegant, but equally effective, circuit.

-- Die Gotterspammerung - Junkmail of the Gods

A fair point.

Best Regards John McCabe

To reply by email replace 'nospam' with 'assen'

Well, perhaps. I have pretty useful (if rusty) skills in electronics, but I need an idea of the principle that was used. I remember circuits in my old electronics mags, but they're over 20 years old, and there must be better solutions around these days!

In article , Andy Dingley writes (re. float chargers for lead-acid batteries)

I build 13.8-volt constant-voltage float chargers using LM317T or LM338K three-terminal regulators, plus a few peripheral parts. The circuits are those which were published by RS Components for the devices. I mainly use them for charging sealed gel-electrolyte lead-acid batteries which I use to power amateur radio equipment. They also work fine on car batteries, and keep them from sulphating due to being left partly- charged.

For faster charging of car batteries, I use larger (15-amps plus) constant-voltage power supplies designed to feed 'nominal-12-volt' electronic equipment. They are set to 13.8 volts off-load, before connecting the battery. When the battery is fully-charged, the current drops to a minimal value and no overcharging takes place.

Regards, Andrew.

Just constant voltage, except that it has a slight temperature dependence. Your battery datasheet (if it's a non-car UPS battery farm) wil tell you, or there's probably something Googleable.

-- Die Gotterspammerung - Junkmail of the Gods