Car battery charger

[Dave Plowman (News)]

If it's an older car, could have a quite marginal alternator. I changed the original 65 amp one on my SD1 for a current design 100 amp unit. Needed a bit of fiddling to fit it, but nothing I couldn't manage. Got it off Ebay new for about 1/4 the cost of a new battery. ;-)

You need to set it to current (amps) remove one battery terminal and insert the meter in series, with everything on the car that can be switched off. Best to short across the *meter* in some way when re-connecting the battery as the switch on surge could be quite high and damage the DVM, or blow its fuse. Once the battery has been re-connected for a few seconds, remove the short.

You should see a reading of no more than 20-40 mA. (0.02-0.04 amps)

[Dave Plowman (News)]

A non regulated charger will certainly damage an SLA - far more than a wet lead acid. Same really as they'll damage Ni-Cads, etc, if left on after fully charged.

[thirty-six]

Part of the problem I had, car used similarly, could have been attributed to grease in the battery terminals and a corroded earthing wire to chassis. I cleaned up the terminals with a bit of cloth but have on other vehicles used a toothbrush and hot water. The chassis grounding lead was cut back and the new crimp connection was made with the wire scraped bright. Those crimp rings are quite tough and I used a blunt cold chisel and a fat hammer in the end to get the crimp secure. As there has been no doubt about the reliability of the system I've judged it too cold to bother with checking for volt drop over every joint and wire to ensure an optimal system. There was also part of the wiring loom which had been stretched around the engine, it's unlikely this was part of the cause of the failure to maintain battery charge but the rerouting to prevent the wire coming under tension was performed, the problem may have contributed to difficulty in starting with a marginal battery if say the temp sensor wire was shorted on the engine block (quite possible).

[David WE Roberts]

Thanks - my digital meter showed virtually nothing but I whipped my analogue meter away quickly as it went off the scale. Will try the shorting trick. I was trying to work out if the voltage of the system made a difference to the amperage shown. Both meters only measure milli-amps - analogue goes up to 250 mA. Load should be for maintaining the radio and computer but not much else.

I have just seen that Lidl are offering a battery/alternator tester for £2.99. I assume that this just measures voltage across the battery when resting and when the alternator is running, but it could be worth a punt.

The car is a Volvo 850 so I assume the alternator is good for charging unless it is getting 'tired' - we have had the car about 5 years now and had no problems before. At P reg it is now about 16 years old so various bits may be reaching the end of their service life.

Cheers

Dave R

[Chris J Dixon]

No, it wasn't that - he reckons the internal battery is actually of much lower capacity than it is labelled.

Chris

[thirty-six]

[e-mail]...

I got one years ago from Tandy for about =A35 , It saved me needing to risk damage to multimeters which were part of my tools for employment. The one I have is a go/no go device for the different conditions and show from an unservicable condition to an overcharge condition. There are 5 LEDs . Works in the dark too.

I don't remember how long ago Tandy were last trading, at =A33 it is tremendous value for the important measurements in a charging system.

Suspect the wires themselves.

[Dave Plowman (News)]

Sorry - can't access utube easily on this computer so didn't look. But the capacity of an SLA doesn't make much difference to a proper charger. It should be regulated to 13.8 volts max.

[Andy Dingley]

My Aldi is fine - it has a "charge it even if very flat" button. It doesn't do 6V at all.

[Jules Richardson]

Our elderly Toyota's terrible for battery terminal corrosion - it seems that they have something of a reputation for it. I've got a wire brush widget for cleaning things up; one fits inside the clamps and the other fits over the terminals.

We finally retired the original factory-supplied battery at the end of last year - it had done an impressive 14 years, so no complaints there!

cheers

Jules

[Dave Plowman (News)]

Most modern low maintenance types these days have a small vent for the gasses to which a plastic tube can be attached, to route them somewhere where they can't do any damage. (I'm assuming it contains a small amount of acid)

I'm assuming that caused your corrosion problem? You did apply some Vaseline after cleaning them up?

[Andrew Gabriel]

About 7Ah instead of the 17Ah labeled, and much lighter weight than it should be.

On taking the battery apart, the cells are bulked up with plastic to make them fill the case, and have only 3 much smaller lead electrodes than the 4 standard sized ones found in genuine 17Ah batteries.

I have a similar unit I bought from CPC, probably 5 years ago. It had a "Long Way" 17Ah battery in it, which is the right weight for a genuine 17Ah battery. It died suddenly this year, but as the unit was rather well made compared with the ones you can buy today, I treated it to a new 17Ah deep discharge battery.