Battery Charger

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Arrann1

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I hope someone can help. I put a one of my boats 12v 80ah batteries on charge today at 3:30 pm using a 120 a 12v/6v charger (Clarke cc120).

I put the hi/lo swich to hi but am now thinking if this was right. I'm at home and I cant find the instuctions and was wondering if I should go down now and check it or put it to the lo setting... I know it has a thermal overload swich but thats all.

Has anyone with a bit more knowledge than me got any advice??
 
I wonder about the charging circuit in the Clarke's. If it doesn't regulate (modify) the rate to a float charge (which it doesn't seem to do /forums/images/graemlins/frown.gif ), you could be putting 12 amps into an 80 Ah battery overnight. If the battery is even half charged to start with, it is likely to be overcharged in the morning.

Lots of IFs, but I'd be tempted to go down and switch it off. The thermal cutout is for the charger, not the battery.
 
I'd say it'll be OK. It's actually only an 8.5A charger, and that's its maximum output - it won't push 8.5A into a battery for ever.
 
OK, 8.5 amps input into an 80 Ah battery for 12 hours. Equals a theoretical 100Ah. Hmmm. Seems like a recipe for a cooked battery - and that's for a really flat batt.

You need a multi stage charger so that the battery can be really fully charged, as when it becomes saturated, the charging <u>current</u> needs to drop while the voltage remains constant.

I don't think this simple charger from Clarke's does that. At best you'll get some outgassing and loss of the electrolyte; at worst grid corrosion on the+ plate, if it's a simple battery. If it's sealed.....
 
Isn't it dependent on the state of charge? At 11.5volts it may push out 8.5amps but if the battery is at 13.5volts it won't be doing anything like that - that's irrespective of whether it's a smart charger. I have a very basic Silverline 20amp charger that drops down on fast charge to less than 2 amps when the battery is fullish. When it's at 50% charge the Silverline does do nearly 20amps.
 
It won't keep pumping 8.5A into the battery, that's the maximum current it's capable of supplying. The charger's output will be voltage limited. As the battery approaches full charge, the current will reduce.
 
but I can spell Peukert /forums/images/graemlins/grin.gif

If it is a "simple" charger, its output will NOT change either over time or the state of charge of the battery. If that's the case, the battery will be fecked in the morning.

And in the morning I shall still be able to discuss memory effect, sulphation, and delta-V.
 
[ QUOTE ]

You need a multi stage charger so that the battery can be really fully charged, as when it becomes saturated, the charging <u>current</u> needs to drop while the voltage remains constant

[/ QUOTE ]

Not strickly true.

Back in the 1980's when I was making multistage chargers, I did a lot of test work, with a correctly rated charger, once the top end voltage was reached, the current falls with a couple of minutes. All you do with extended running at top end voltage is gassing, and inprove the sale of distilled water. This phase only comes about when you try and charge the battery fast, and you do not get complete conversion of the active material.

We ended up leaving out this stage totally, and indroducing a new system, this gave a better charge, with vertually no gassing.

Buts thats another story.

Brianh
 
Thanks guys (and girls?) for your advice. I actually went down and swiched the charger off at about 9.00 p.m as I wasn't sure...better to be safe than sorry.
 
Battery had 11.50v (by multimeter). But was still drawing in excess of 5 Amps. But it was on rapid charge.

I should have put it on Low (trickle charge). On the low setting I have subsequently found out the the worst case scenario is that when the battery is full it will just draw a minimal 1a or so which will be dissipated as heat...
 
Looking back at the posts It went on charge at 3:30pm and was taken off at 9:00pm so that's 5½ hours.

Assuming it was running at 5 amps all the time, although it may have initially been higher., that's 27 and a bit Ah . It really ought to have got even a dead flat 80Ah battery up to a rested reading a bit in excess of 12volts in that time.

I reckon the battery is cream crackered but its worth leaving on for longer. At least another 12 hours at 5 amps to see if it shows any sign of recovery. You are looking for a rested voltage of at least 12.6 preferably 12.7

sorry reply really intened for the OP
 
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