Lead acid battery charging.

[ericmark]

Well never took the 20 Ah off charge, disconnected the 7 Ah and it did not trip, it now charges on its own, 15th June to 10th September is a very long time, and like the others recovery was sudden, unfortunately by time it recovered the energy meter was being used else where.

 

[ban-all-sheds]

Has any one used one of the so called smart chargers, like the CTEK MXS 3.8 to revive a VRLA and what results did they get?

I've been trying with an MXS 5 on some VRLAs (6 in all) from some emergency lighting power units which have been on the shelf for some years. Not enough life in them for the charger to recognise that there's a battery there. The EM unit charging circuitry is delivering about 13v to them, but as soon as that is switched off the voltage drops rapidly to about 3, even with them disconnected, i.e. not trying to power anything. I don't want to parallel that charging with the CTEK, so I need to think how much I CBA to put a car battery in parallel, knowing that it's almost certainly academic, and that the old VRLAs are totally shot.

No way to monitor what's being used.

 

[ericmark]

The point I am making is it takes a long time, with nothing to show anything has happened. I had this battery with around 12.9 volt showing on the charger display for three months, it seemed the battery was completely dead. With the Lidi Charger

I could not use the charger without another battery in parallel as at 15 volt it auto switched off, although it seems good that it will charge 6 volt as well as 12 volt, it also means the battery voltage must be within the range 7.5 to 15 volt, under 7.5 it thinks it 6 volt. The sulphated battery must have been taking some charge, but so little the charger behaved as if the leads were disconnected. So only way was a battery in parallel.

Although instructions don't tell you, it has three charging rates which it will auto change between, the first two 3.8A and 3A it will never auto return to, so voltage raises to 14.4 volt with 0.8A charge, then it drops to 0.1A charge and battery voltage falls, if it drops to 12.8 volt then it returns to 0.8A charge, however if it continues to raise as it hits 14.4 volts the second time it switches completely off. At which point the battery voltage starts to fall, once it falls to 12.8 then whole process starts again. So in the main I would walk into the garage and it would show 12.9 volts.

I had given up, I really did not expect the battery to ever come up. We as I say are talking about 3 months on charge, the battery was on a wheel chair, it was given to me without a charger, and the first Lidi charger did not have a voltage display, and it would put enough into the battery for around 1/2 mile, but then the charger failed and wheel chair abandoned back in 2013. When the 7 Ah batteries fitted to my father-in-laws stair lift recovered I thought worth a go with the 20 Ah.

From what has happened with the other batteries, once batteries fully charged I expect to see voltage at 12.9 volt, at the moment 13.4 volt so clearly still taking charge, once fully charged the voltage will raise to 14.4 volt, charger will turn off, and within a minute or two it will drop to 12.9 volt then slowly it will lose that last volt then charger switches on for a minute or two volt go to 14.4 again, and yet again it drops quickly, so 9 times out of 10 when you look a good fully charged battery shows 12.9 volt.

Not a clue what the Ctek does, but would guess some thing similar. Next I need to test the battery, see how long it will light caravan lights.

 

[ban-all-sheds]

What the Ctek does is to shut down, as per normal-shut-down-if-left-disconnected feature, because it doesn't know there's a battery there.

 

[ericmark]

What the Ctek does is to shut down, as per normal-shut-down-if-left-disconnected feature, because it doesn't know there's a battery there.

The same as the Lidi.

I have tried a load, put it to work caravan, as I tried to turn on more and more lights you could see the voltage drop, however 5 lights ran for 30 minutes with voltage above 11 volt I would guess around a 3 to 4 amp load. I don't think it would be much good as it stands running the wheel chair, however it would run my FT290R transceiver for quite a long time.

What I want to do is fit a second battery to caravan, then I can keep the 75 Ah fully charged for motor mover, and use the 20 Ah for Lights, radio and central heating. Then it will not matter if we completely run down the 20 Ah battery, it will still motor up the drive into back garden.

Now charging again using a steady 13W which will relate to 0.8A. I am really chuffed, I never expected it to come up.

By Wednesday current dropped to 0.1A at 13.8 volt and by Thursday volt up to 14 volt, at 14.4 volt charger will auto switch off, at which point the charging is considered complete.

 

[ericmark]

A surprise again, I expected the charger once the battery had absorbed a bit more to drop to zero output, however it has started charging all over again, all I can assume is the cells are recovering one by one, which would explain the steady 11 volt under load, it shows it using 6 or 7 watt at the moment which is not really possible, the charger gives either 0.1A or 0.8A so 2W or 12W the refresh rate is too slow for energy meter to show this, what is happening is at 0.1A the voltage drops to 12.8 at which point it switches to 0.8A and the voltage raises to 14.4 at which point it switches to 0.1A again.