stacking cheap chargers to gain amperage. Cheap, frugal, or stupid?
what maladies am I getting into by stacking 3 48 volt 2.5 amp chargers wired parallel to give me 7.5 amps charging 4 22ah universal sla batteries? This is probably a dumb question, but I really appreciate the help.
It's my understanding that chemical betteries like a slow discharge and charge best, but sometimes an enthusiast will want a fast charge, regardless of the need to manage possible problems.
The general rule of thumb I have "dog-eared" is a lead-acid battery doesn't like to be charged faster than 1/10 the total capacity. For instance a 10 A/h battery should be charged at rate of one-amp or less. I hear in FLA's it boils away the fluid due to electrolysis, but in a SLA I can only imagine that one problem will be excessive heat.
Anyone else with experience in SLA "fast charging"?
From what I have heard a short burst of higher current can be good for blasting off sulfites, or just getting a really dead battery awake enough to take a normal charge. But for regular charging, slow is better for more cycles before the battery dies. I wouldn't think much more than 4 amps would be a good idea. One way to do that would be 4 cheap 4 amp 12v chargers, and then charge each battery individualy. Lots of people with car conversions swear by that method for better balancing. Monsterscooterparts and Electricscooterparts both have a decent deal on such a 4 amp charger.
If a fast charge is more important to you than battery lifespan, batteryspace has a cheap 10 amp 12v charger. Two chargers doing two paralell connected batterys each? 5 amps per battery and half as many chargers.
The spec sheets for most SLA's specify a maximum charging rate of 1/3 C or 7.33 amps in your case. So you are only a little bit over the maximum charging rate.
Wether there is a benefit at charging at the low end of the permissible range, I don't know.
Thanks for all the info. It helped out a lot. I was fairly apprehensive the way I kabobed them together. I plugged it in and it seemed to work ok. The triple decker got warm rather quickly, but the oversize fan I installed did,t come on. Is there an approximate temperature that the fans kick in or are they all over the board?. They cost a wopping $16.00 a piece on ebay so I'm somewhat surprised they worked at all. I really appreciate your help.
Cool, I didn't realise you had em already. Keep us posted on how it goes, chargers are pricy and hard to find in the 6 to 10 amp range for 36 and 48 volts.