Battery charging?

fpappal · Jan 22, 2020

If I have two deep cycle 6V batteries connected in series, can they be charged with a 12V charger? Or would I be better off charging them individually with a 6V charger? These batteries came from a floor cleaner at work. A friend is interested in using them in a little hunting trailer and using them to power some lights and a fan. The thought was to use a solar panel to charge them. Any suggestions?

old · Jan 22, 2020

Yes you can charge them in series but if one is weaker then the other they may not charge well

Janicholson · Jan 22, 2020

If they have cell caps, use a hydrometer to assess each cell for specific gravity. If some cells are divergent from other cells by more than 10%, they may be unusable. If they are charged (at 7 volts, or 14 volts (series, or individually) do not leave them alone. It is worth the time to make sure they are not over heating, boiling, or gassing out of any cell. Filling with distilled water is also needed to the level mark/ring. Trust nothing to be OK to leave alone. Fires and explosions are not fun. Jim

Geo-TH,In · Jan 22, 2020

Charging batteries in series is done all the time 36v golf cart are six 6v batteries
Electric wheelchairs use two 12v in series.

Where you get in trouble, one battery ages faster than the other. So when the bad battery has lost all it's charge and you continue using it, The weak battery takes on a reverse polarity.

When that happens its recommend you replace both batteries at the same time.

So yes you can charge two health batteries in series.
George

JMOR · Jan 22, 2020

when you charge a 6v batttery, you are charging 3 each 2.1v cells in series & likewise with 12v battery, 6 each 2.1v cells in series.

Russ from MN · Jan 22, 2020

If your going to use them in series I would charge them in series. But I would check the voltage on them individually after charging to check condition.

Tracy Brown · Jan 22, 2020

You can but I would not. If one battery is stronger than the other, the charger can burn the strong one out trying to build the weak up.

guido · Jan 22, 2020

Hello Fpappal,

Wether you charge them in series or in parallel, they will not both receive a full charge.
Charge them INDIVIDUALL. they WILL them the most charge that they can take.

Again, do charge them individually for the best charging results regardless of how they are charged.

Solar charging will work, of course, charge rate would have to be adequate for the amount of amp draw.

Guido.

mdm1 · Jan 22, 2020

If you do use a solar setup make sure you have a charge controller as part of the system. Takes care of over charging as well as under charging.

glennster · Jan 22, 2020

i agree with charging them separately. my boom truck uses 2 1k amp 12 v batteries, i leave a maintainer on each battery all the time. i picked up some battery chargers/maintainers/desulfate units from home depot , they are 8 amp, 6 or 12v all automatic. about 39 dollars a copy, i alsogot some if the 2 amp units too, they work good. here is a link.
battery chargers

da.bees · Jan 22, 2020

I suggest charging each individually to begin with. Once charged,test voltage of each. They should be within 10% of equal. If they are within 10% they can be charged in series going forward. Otherwise they need should be charged individually then joined for use( which will be more trouble than it's worth).
Fully charged 6v battery= 6.37v
Fully charged 12v battery=12.73v

OldFarmTractor · Jan 23, 2020

Interesting reading about charging these two batteries when in series.

Consider this.... isn't a 12V battery just 2 6V batteries in series? The 2 6V batteries just happen to be in the same box. Actually, the 12V battery is 6 2V batteries in series.

Me, I would charge them together if they are close to the same age and specs.

Blackhole49 · Jan 23, 2020

All 36 and 48 volt golf carts are 6,8 or 12 volt batteries in series and charged with one charger. My truck is 48 volt. My first set of 8 6 volt batteries lasted 10 years and my second set is 4 years old and going strong. I do replace them as a set.

jeffcat · Jan 23, 2020

Absolutely....would you change only one battery in a two battery flashlite??? Always as a set because you will end Up with a lazy battery. BTDT.

BarnyardEngineering · Jan 23, 2020

(quoted from post at 17:44:55 01/22/20) You can but I would not. If one battery is stronger than the other, the charger can burn the strong one out trying to build the weak up.

That is what happens in a PARALLEL setup. In a series setup, this is not correct.

If anything, the exact OPPOSITE will happen. The weaker battery will not take a charge, while the stronger battery becomes overcharged, and damaged.

Here's how I handle it:

If I do not know the condition of the batteries, or I know that both batteries are not in roughly the same state of discharge, I charge separately.

If I know that both batteries are good and in roughly the same state of discharge, I charge them together in series.

Battery charging?

fpappal

Member

old

Well-known Member

Janicholson

Well-known Member

Geo-TH,In

Well-known Member

JMOR

Well-known Member

Russ from MN

Well-known Member

Tracy Brown

Member

guido

Well-known Member

mdm1

Member

glennster

Well-known Member

da.bees

Well-known Member

OldFarmTractor

Member

Blackhole49

Well-known Member

jeffcat

Well-known Member

BarnyardEngineering

Well-known Member

Similar threads