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Charger for SLA 12V / 7Ah battery

Started by gm July 2, 2015
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

"gm" <notMyMail@mail.not> wrote in message 
news:mn479i$er8$1@l01news1.ot.hr...
> 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.
On Thursday, July 2, 2015 at 4:35:02 PM UTC-4, gm wrote:
> 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
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),
bloggs.fredbloggs.fred@gmail.com Gave us:

>On Thursday, July 2, 2015 at 4:35:02 PM UTC-4, gm wrote: >> 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 > >Slow charge is 0.1C, that's 700mA to you, even that will make the battery warm.
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. http://tinyurl.com/nm6pn3r
On 7/2/2015 3:34 PM, gm wrote:
> 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
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?
On 7/2/2015 10:18 PM, John S wrote:
> On 7/2/2015 3:34 PM, gm wrote: >> 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 > > 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 <notMyMail@mail.not> Gave us:

>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
You should have bought one of these... http://www.amazon.com/Prodeco-Outlaw-SS-V4-28MPH/dp/B00JZRO1IG All the pro gear on it is alone worth over $1.8k.
On Thu, 02 Jul 2015 22:21:43 -0500, John S <Sophi.2@invalid.org> Gave
us:

>On 7/2/2015 10:18 PM, John S wrote: >> On 7/2/2015 3:34 PM, gm wrote: >>> 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 >> >> 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? >
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)
On Thursday, July 2, 2015 at 4:35:02 PM UTC-4, gm wrote:
> 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
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.
On 07/03/2015 06:35 AM, dakupoto@gmail.com wrote:
> On Thursday, July 2, 2015 at 4:35:02 PM UTC-4, gm wrote: >> 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 > > 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