Aldidl charger with a capped battery.

[thirty-six]

The AutoXS battery charger has a charge rate of 14.7V / 3.8A for cold charging, as nothing was happening at the lower (14.4V) setting, and is connected to a 41Ah car battery. It has been on this setting for

24 hours and the charge voltage is at 13.1V . The disply is showing 60% charge but I doubt that even that has occurred at this voltage. So have I got a dud for a new battery (now 2 months old)? There seems to be a slight bulge at one end and I am unable to assess any plate activity because the cell caps are covered.

[NT]

The battery ought to charge fully at 14.4v. 41Ah/3.8A =3D about 11hrs, so nothing wrong there.

Whether the charger is giving you good info or not I've no idea, load test the battery and see. I cant imagine how it would determine a 60% charge anyway.

NT

[thirty-six]

That's what I was expecting, but it hasn't. It's been on the higher voltage setting for in excess of 24 hours and has just crept to a displayed 13.2V It certainlt read more on the other batteries I have and I'.. get a meter across to check the charger indicater has a semblemce of accuracy.

The battery is a Varta black powerframe, should anyone have specific experince with them. My guess is that the initial charging, before purchase, has been poorly performed resulting in the battery letting us down come the frost. It's surprising to me that this should occur with this brand and I'll be checking the charging system before taking the battery back to be tested.

The charger periodically drops the charging so I suppose it's a guess from the immediate off-charge battery voltage.

[John Williamson]

It's probably programmed to give a reading based on the curves shown here, or a similar one:-

curves are pretty similar for all lead-acid batteries apart from the new modified types, which have a similar shape, but with slightly increased voltages.

[thirty-six]

Looks like whatever curve they chose is well out, for some unbeknown reason the charge rate is predominantly at 2.4A . After I pullled the ammeter and reconnected the charger, next thing it is showing

14.3V charging voltage. I prayed, but it dropped back to 13.3V . The displayed voltages do tally (close enough) with my analogue voltmeter. I have some digital meters, but I doubt I'll learn any more. There also seems to be a heafty alternating current, enough voltage that I can feel and showing 30Vac on the meter.

[Andrew Gabriel]

If that's accurate, I would guess you have a shorted cell, with the remaining 5 having got overcharged. I would take it off charge and put a load such as car headlamps on it for 10 minutes, and see what the voltage does. 10-10.5V would confirm a shorted (dead) cell.

[thirty-six]

Made 12.6V today after 10 minutes with the 21W lamp. On reconnection it went straight back into trickle charge, settling back at 13.1V . I took off the surface charge again (to 12.7) and connected a 5W bulb in parallel in an attempt to force the charger in maintaining a proper charge voltage. It was still charging at ten minutes, will check in an hour. If it's maintained this last bit of charge, I'll be putting the battery on the car today and making the alternater voltage checks.