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Charger for SLA 12V / 7Ah battery

Started by gm July 2, 2015
On Sat, 04 Jul 2015 10:02:08 -0400, krw <krw@nowhere.com> Gave us:

>You didn't specify the limitations of your absolute statements, >AlwaysWrong.
The topic was and is the SLA devices the OP is using, idiot. Nice try though, child.
On Sat, 04 Jul 2015 11:05:23 -0400, DecadentLinuxUserNumeroUno
<DLU1@DecadentLinuxUser.org> wrote:

>On Sat, 04 Jul 2015 10:02:08 -0400, krw <krw@nowhere.com> Gave us: > >>You didn't specify the limitations of your absolute statements, >>AlwaysWrong. > > The topic was and is the SLA devices the OP is using, idiot. Nice try >though, child.
Though you didn't limit your absolutes to that, moron. You state that SLAs *were* batteries, which is *wrong*. You're *always* wrong, AlwaysWrong.
On Fri, 03 Jul 2015 13:17:59 +0100, Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

>On 03/07/2015 05:35, 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. > >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. > >http://www.powerstream.com/SLA-fast-charge.htm > >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.
Charge rate all "boils" down to battery temperature... If the battery doesn't get too hot, then go for it ! Here is one app-note that gives some good information. https://www.cdtechno.com/pdf/ref/41_2128_0212.pdf For instance, C&D says to limit temperature rise to 10 degrees C. C/1 is about the highest they show here. I have heard of VRLA batteries being able to be charged at MUCH higher rates. It comes down to internal resistance while charging. A lot of times, the user doesn't have e large enough charging source to hurt anything. If too high of current is pushed into the battery, it may quickly rise to the constant voltage stage anyway, and then the current will naturally reduce. Battery resistance while charging/discharging is the key of course. boB K7IQ