Charging battery

Is it better to charge a battery 2 amps for 12 hours, or 6 amps for 12 hours? Thanks, Stan

If you're charging a conventional lead acid, conventional wisdom says slow is better than fast.

its best to get a trickle charger that knows when the batt. is charged and quits charging it till it drops off again most modern chargers do this.

An automatic charger at any reasonable charging rate (like 20 amps or less) will taper the charge to a trickle as it charges. Heat and over charging are the bad guys. So a 6 amp charge for 12 hours can overcharge a battery. so can 2 amps if the battery was charged already. A near dead battery (like group 24 size) will fully charge at 2 amps in 12 hours.
Use automatic chargers and stop worrying. Jim

Slow is better than fast, unless the battery is dead. Then it will take a GOOD charger to get it started, then slow charge it all the way up. DOUG

Most anyone will tell you slow is the best with either of the two Schumacher chargers shown, cost $30.oo at Lowes ,auto zone and some others. Charge at 1.5 and two amp. Auto select 6 or 12 volt. Shut down when full and go into a maintain function afterwards. I must have ten of these all over two places hooked to stuff. Work great. A low battery can take up two days of charging before ready. These Scumacher units are great. Make sure you read the box! Charger, auto select, and maintainer. There are a couple of models.

Depends if that's all you got to charge with I take the big number...
I am not all in on Slooooooooow charge'N I have real chargers and throw all its got at'em... Time is money...

Ok slow charger NuttZ yer alternator puts the hammer down if slows good then get a smaller alternator and see how that works out fer'ya...

I do prefer low charge rates on small battery's big'Ns get a hale marry throw at'em...

A lot depends on how much the battery is run down. Back when I had these stupid smart chargers if the battery was really dead the charger said it was sulfated and refused to charge. I had to put it on a float charger and charge the batteries for many hours before I could use the charger. Now I just use the float charger only. It often takes all night to charge a battery but it doesn't tell me to go to H.

Well, you have plenty of answers to choose from. I might as well add some more. Your battery will be at least a 70 ampere hour battery. Not 70 amp, but ampere hour. Theory wise, that would mean it would take 70 hours at one amp charge to recharge if it was totally dead. Of course a battery is never l00 percent efficient so it actually takes longer.

Throwing a quick charge will get it up to where you can use it but that does not mean it is full charge by any means. Something like putting a pint of water into a five gallon pail. That would give you enough for a cup of coffee but it won't fill a couple of pots. Now, leaving that pail partially full won't hurt the pail , but the battery in that stage will suffer because the inactive parts of the plates will harden, sulfate, and then are useless.

If dead and you jump start vehicle, the alternator will throw a heavy charge in for a while but pushing a heavy charge in takes higher voltage than slow charge so it soon tapers off to a low charge rate. It never quits charging though. It is always pushing in a small charge of up to two or three amps. So, if you are driving across country, 24 hours straight, that battery is always getting a small charge. Does it harm the battery. Only if charging voltage is too high which will push more than an acceptable couple amps of charge.

So, put a slow charger on and leave it on until the voltage reaches normal charging voltage of right close to 14.5 volts. Automatic charges normally quit charging before full charge is reached. If you can open the cell caps and look in, every cell should and needs to be bubbling just slightly at a low rate of charge near that 14.5 volts.

Now, you are really confused and I don't blame you. BUT, TOO darn many batteries are ruined by not bringing them up to a full charge condition while doing it at a low, slow proper voltage rate.

strange.... that a lot of commercial battery chargers use 3 phases of charging to maintain batteries. BULK charge is the very first phase.


trickle chargers will not fix weaker cells and other better cells can and will take on the over charge, eventually rendering the battery useless. Bulk charging fixes this and keeps all cells working. "Equalizing" is an extreme example of this. :roll:

"Auto select 6 or 12 volts" ........ does that mean the charger itself adjusts itself to what battery voltage it's hooked up to?

Positively. Just hook it up, plug it in, it goes click, and a little indicator lites up. Several hours latter the bigger green light comes on and it goes into the desulfate mode. This is supposed to be a very fast pulsing of 19 volts that will slowly clear the plates of sulfate. Takes several weeks for a really gunked up battery. Love these chargers.