The subject says all :-) I connected 3 x 12V / 7Ah battery's is serial and start to charge them with my ebike 36V/1,2A charger. After cca 30 minutes battery pack was getting hot, so i disconnect the whole stuff.
What is the highest charging current for such battery's ?
The funny thing is that i use the same charger to recharge my 36V ebike battery pack, and there was no problems whatsoever. The charger was shipped with ebike and the ebike battery pack is also a lead acid pack...
GM
Charging 12 volt lead acid batteries needs a constant voltage of 13.8 to
14.0 volts per battery. And some current limiting is desired. Your three batteries need to be all the same capacity and the same age. It will take about 42 volts to charge them. As the batteries reach full charge, the current will drop to nearly nothing if the batteries are good.You might consider getting a cheap 12 volt battery tender from wally world and charge each battery alone.
A digital multimeter is a useful thing to have.
Slow charge is 0.1C, that's 700mA to you, even that will make the battery warm.
On Thu, 2 Jul 2015 14:40:37 -0700 (PDT), snipped-for-privacy@gmail.com Gave us:
Charge them individually too.
This Motorola dongle is a very nice unit, and makes 13.8V @ 0.9A max
It would not be hard to current limit what the battery gets pumped with.
It is a Motorola Model: 2580600E01 and is UL listed, which so many these days are not. Nice, heavy line out.
The right unit is only 16W in. The others are fake or respin models.
Keep the charging current below about 2 amps.
Were all three getting hot or just one of them? They usually only get hot when they are fully charged and are throwing away the excess. Are you sure they need charging?
For example, suppose one of them is essentially shorted. It will not get hot. The other two will try to charge to 36V even though they should charge to only 24V and they might get hot. Does this make sense?
On Thu, 02 Jul 2015 22:34:57 +0200, gm Gave us:
You should have bought one of these...
All the pro gear on it is alone worth over $1.8k.
On Thu, 02 Jul 2015 22:21:43 -0500, John S Gave us:
They should be charged individually. Ever heard of "memory effect" as it relates to battery pack assemblies? You essentially just described one scenario of it.
Does this make sense? (rhetorical question)
A simple rule of thumb is that the maximum charging current must be AH/10, where 'AH' is the rated Ampere hour. The maximum charger voltage should be alightly higher than the rated maximum voltage of the battery to be chargrd.
------------------------ Maybe this "memory effect" is the main problem. I charge them separately and they charge without a problem on 12V - 2/4/8A regulator.
They are used battery's and voltage of each battery was between 10 -
12V. I can connect them in parallel and charge them on this way. After charge i can reconnect them in serial connection.GM
C/10 is relatively safe for manually operated dumb chargers.
Fast chargers with the right algorithms and safeguards can do C/3 or much higher into modern SLA battery packs. Even prehistoric dumb as a rock car battery chargers offer to put ~6-8A into a 40Ah battery.
Some makers claim 1.5C as the practical upper limit - seems a bit high to me. Anyone with direct experience of this kit care to comment.
Overcharging is bad for them. The right terminal voltage/current profile is temperature sensitive. Charging them in series is asking for trouble since the weakest pack will put the others under stress.
It is a great way to ruin batteries in the longer term.
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Charging them in series is asking for trouble since the weakest pack will put the others under stress.
*** Of course, i agree with you, but how to make / test some 36 or 72V charger ? I got one 10A 72V Chinese charger that i used to charge 6x12V battery pack. The pack was charged OK but the charger was so hot that i need to wait cca 20 minutes until i could move him....
Yes. However, I was unaware that SLAs have a "memory effect" similar to NiCd, etc.
The elephant in the room is that a 12V SLA is actually 6 series-connected 2V cells in one box. You can't charge the cells individually and, in fact, they fail for the same reasons rendering the entire battery useless.
I agree that it is better to charge each 12V battery individually because there is a better chance that the cells are balanced and manufactured for this purpose.
** Stay unaware - it's nonsense.
.... Phil
On Fri, 03 Jul 2015 14:53:36 +0200, gm Gave us:
If you didn't assemble the pack, it may have had individual "watchdog" circuits on each cell element, making for an evenly balanced charging session management schema.
On Fri, 03 Jul 2015 08:40:32 -0500, John S Gave us:
Purchased "packs" (batteries were what they were once called) generally have individual cell management circuitry these days, negating such 'effects'. A hand assembled conglomeration typically does not, and almost certainly not when the assembler is asking here about charging methods.
Have you noticed the Subject line? It says SLA which is an acronym for Sealed Lead Acid. These are not "packs". They are still called batteries. Do a search.
Why do you insist on being always wrong, AlwaysWrong? Is it hereditary or did you manage it on your own?
On Fri, 03 Jul 2015 11:42:24 -0500, John S Gave us:
Are you daft?
I didn't need a primer, thanks.
When a person places an array of them together, the finished product is known as "a battery". Check your dictionary. Context is everything.
On Fri, 03 Jul 2015 11:42:24 -0500, John S Gave us:
Someone should come find you and upgrade your manners, idiot.
Remember, it was you that brought bullshit into this thread with this baby bullshit childish non-sense. Grow the f*ck up, child.
I don't think so. Why do you ask?
Apparently you do because of the following...
Can you read what I typed in the paragraph just above your last one? I say "batteries" and you say "a battery". I say tomato and you say tomato. Let's call the whole thing off. Take your meds.
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