How to properly charge lead-acid batteries in series?

Question

Say I had four 12-volt lead-acid batteries connected in series as a battery pack.

Could I buy a 48-volt rated charging unit that would charge them all at the same time?

I have heard of issues with other battery chemistries where one battery happens to become under-charged in a series string (due to slight internal resistance differences, etc).

Would it be better to disassemble the pack and charge the batteries individually with an appropriate 12-volt charger?

Please advise. Thanks!

Answer 1

If each of the batteries has the same capacity, then yes, you may connect them in series and use the (nominal) 48 volt charger. (it should have an unloaded voltage of about 55.)

The matter of unequal voltages etc, mentioned in a previous post, refers to every cell in a battery. There's nothing you can do about this unless you have access to the individual cell's terminals. And if you did, it entails a lot of buggering about to correct the problem.

Just make sure that each battery is discharged to the same point before charging them in series.

The state of charge is evaluated from the specific gravity of the electrolyte. Around 1120 for a fully discharged cell, around 1220 for a fully charged one.

If you want to be pedantic, search the manufacturer's web sites for variations with, and compensation for, temperature.

Answer 2

You are right, charging and using batteries in series has to be done carefully. Your problem is actually one of the individual cell voltage. Submarines use big lead-acid cells in series. They have a way of monitoring each individual cell. They use two indicators, the individual cell voltage and specific gravity of the electrolyte to determine the state of the cell. I do not remember the exact numbers, but there was a specific way to charge the battery called an equalizing charge, which fixes the one low cell problem. In essence, you charge the cells in a normal manner until it appears fully charged, and then continue to overcharge at a low rate. The cells which are already at full charge electrolyze out hydrogen and oxygen while the cells which are not fully charged continue to take on more current. They continue until they have applied 110% of what they calculate the full charge should be. This is a dangerous thing to do because the H2 and O2 given off is an explosive mixture right out of the box. One spark, and bang.. You have to keep an eye on the cell electrolyte level as you are intentionally overcharging some cells and losing water. In a submarine, they have devices specifically there to burn H2 out of the air. You do not have to disassemble the series string to charge the batteries. It would be better if you got individual wet cells than use car batteries or a battery with exposed intercell connectors. You can not get the individual cell voltages in a car battery. Don't try this with "maintenance free" batteries. If they are the gel electrolyte kind, you can not replace the water the cells lose if overcharged which is why a gel cell is really BAD (short lived) to use in a car, which overcharge the battery most if not all of the time. If you are very careful, with good ventilation to prevent the buildup of H2 and O2, you can just charge the battery and watch for bubbles in the electrolyte. Cells that start to bubble are charged. Cells which are not bubbling are still taking on charge. It is sort of a go-no go test. This is dangerous! Charge at a slow rate, maybe an amp or less, and watch the levels, adding distilled water as necessary to keep the levels up.

Answer 3

Microwave radio sites use 48 volt battery systems. Periodically they are given an "equalizer" charge, which is a high current at much more than 48 volts. Obviously the radio equipment cannot be attached to the battery bank during the equalizer charge period, which is about an hour if i remember correctly. A normal battery charge is maintained between equalizer charges which is done about every 2 months or so.

you should be able to buy commercial 48 volt chargers with the equalizer function built in.

Answer 4

It probably would be better to charge each battery by itself , but it is not necessary . Golf cart batteries connected in series are charged that way on a daily basis with no ill effects. As the batteries charge their internal resistance is lowered. Of course the internal resistance of a battery never reaches zero even when fully charged.

Answer 5

Yes, you can charge them in series at 48. And yes, if they are not all in the same condition, then one may overcharge and another undercharge.
Better answer: why not charge all 4 in parallel on a regular 12 volt charger, if the charger will handle 4 times the current of one battery?
Parallel means connect all the positive leads together and put them to the charger positive terminal. And all the negatives together to the negative terminal. Then you can combine big ones, little ones, live ones, dead ones, etc.

Answer 6

i do no longer understand your question. The fee controller kills the burden till battery fee reaches 12.6. ???? Being a mechanic and having to handle charging structures, i understand you like a minimum of 13.8 volts in case you will get a battery to cost completely. you placed a volt meter on a vehicle battery and notice what it reads after working awhile then turn the engine off and verify it an hour later. that is going to study greater suitable than 12 volts. If the voltage coming from the photograph voltaic panel isn't above the battery voltage you are able to throw a hundred amps at it and it won't fee. Volts is stress and amps is modern. If the stress in the battery equals the stress coming from the controller no modern will pass. i could have theory the controller would desire to administration the pass of amps so the battery would not boil too long. wish you may get it taken care of by way of fact on the 2d it sort of feels to me that an hours drain on the batteries and that is going to likely be days of wonderful sunlight gentle to get it lower back lower back.