Auto Chargers vs R/C chargers question

[HarryN]

Hi

I have some 12 V lead acid batteries that I picked up on ebay a few years ago. their original use was in a telecom power back up application. I am guessing without looking that they are around 4 - 500ah. They have been in a shed for several years, and very well might be dead. In any event, I would like to try to bring them back to life if feasible.

I don't currently own a car / marine battery charger, and started looking around sears, etc, as well as at some of the R/C pack chargers like a Triton. My reasoning was that if I was going to buy a charger, why not get one that can charge up R/C packs as well, in case I ever decide to do that with my son.

So far, it appears that chargers for car / marine batteries work off A/C, but the R/C chargers tend to charge off of the 12 V car batteries. This means I would have to add a power supply to the R/C charger price as well if I go that path, which is exactly what I don't want to do right now.

If I can, I would like to keep the purchase down to around $ 100 or so.

The charger will not be used to charge individual cells, I am set up for that already. Charging speed is not really an issue (overnight is fine) and if I can get in the general range of 90% or more of charge in the cells (compared to the premium chargers) that is fine as well.

I did a variety of attempts to search the threads, as well as the sticky threads, but I seemed to overload the system when I did that, so I stopped.

Suggestions ?

 

[poguy]

400-500 amp-hours is a decent size battery. I'd go for a large AC-powered
charger.

Question: How can a charger that runs off of 12 volts (probably a car
electrical system) charge a 12 volt battery? Unless it has a switching
supply to step up the voltage. That's going to be a big supply.

If you had other 12 volt stuff to run, get a 12 volt supply for radio use.
Most produce 13.5-13.8 volts. To charge batteries put a light bulb in
series with the output for some current limiting, especially if the battery
is dead. I have a 45 amp supply that works fine.

Look around for lead-acid battery faq's, too. Plenty of information out there.

 

[Fallingwater]

Question: How can a charger that runs off of 12 volts (probably a car
electrical system) charge a 12 volt battery? Unless it has a switching
supply to step up the voltage. That's going to be a big supply.

They do have step-up converters. They aren't the size of nightstands because they aren't supposed to charge very large batteries.

Most if not all RC chargers are inadequate for a 4/500ah flooded lead acid battery. They might charge it eventually, but you'll have grown a beard by then.

A suitably butch car charger should be adequate, but a marine or truck charger would probably be better.

 

[HarryN]

As it turns out, I was way off on my estimate of battery capacity - it is 50 A - Hr, not 500. I was thinking of cold cranking amps. They are also gel cells, not true lead acid.

Anyway, the R/C chargers seem to be designed to be recharged at the field off of the car battery, so I guess that is why they run off of 12 V inputs. Maybe I will just buy something at Sears.