12 Volt Battery Charging

Agree with ↑

Replace the defective battery!

Check that there isn't another load on the 12 volt battery that has low voltage. It's not uncommon to find that a piece of 12 volt equipment has been connected to one battery. If not, just replace the the bad battery.

X2 on TCM, if you discover that one battery is bad, (sounds like 1 cell) replace both batteries.

The 12V battery is low. The 10V is empty. Charge the darn things individually. When unsccesful in keeping them charged, throw them out, as uncounted people before me told you. A dead battery = is a dead battery, end of discussion.

Either the 10 Volt battery is well discharged or it has a shorted cell.

Also your 12.5V battery does not seem to be fully charged - I would expect a higher float voltage, specially if it was just disconnected from a charger or alternator.....

Hi All, I have a similar problem with my golf buggy. 4 off 12volt batteries in series to give 48 vdc. One battery is down at 11 volts whilst three are at 13+. From what you guys are saying it will be necessary to replace all four batteries and not just the one that is low.Can one of you please be kind enough to confirm this for me as I do not want to just replace the one and find I have still got a problem.

Many thanks

Oliver Dunthorne (Hydraulic engineer "not electrical!"

This is a fairly common problem with golf carts. They usually run the lights off from one of the 12 volt batteries. That battery doesn't get fully charged , as the charging is from a 48 volt charger. They get away with that because the lights are infrequently used on a golf course. The problem surfaces in golf cart communities where the carts are often used at night. The best solution is to buy and install a 48 to 12 volt converter for the lights.

The main reason for such problems (assuming for the moment that both batteries are the same age type and make) is a badly designed/cheapo charger.

Where more than one 12 volt battery is in use, its actually best to use a separate 12 volt charger for each battery. A charger that does not float or over charge. One that does not gas or overheat the batteries.....

Another good trick is to buy larger batteries than you need, say for example 50% larger and to only charge them to around 70% of capacity (to around 13.2 volts only), then stop charging. Restart charging when the get down to 12.6 volts.

They will never gas, get hot and they will last years and years......

Used SLA versions if in an enclosed area, even though gassing should never happen as any battery gas is explosive. Follow the laws for where you live.

not exactly to the topic Additives to Boost Flooded Lead Acid

(if the 10V one is OK has lowwer internal resistance ... blah blah blah ...)

26 VDC voltage from a no load battery charger is a little low. If that is how you took the voltage. And yes starting the generator from the charger may cause it harm. Unless you have one that has a motor starting function.

About replacing batteries in series it is aways a good idea to replace both when one goes bad. As batteries age the internal resistance in the cells change. The lead plates break down, lose surface area which increase resistance. This some time causes one battery or batteries depended upon how many connected in series to over charge. The new one being under charged. This lead to a circle of replacing a battery periodically and not getting the full life from them.

Of course it is easiest to just replace the batteries, but that may not be necessary. When the battery companies came out with the no maintenance battery, The art of maintaining the lead acid battery faded away. A no maintenance battery just has cell caps which are more difficult to open. Check the electrolyte in each cell. Use distilled water to top off the cells to the indicator. Do not overfill.

After the battery is charged you can use a Hydrometer to check the charge of each cell. And here is a trick: Without access to the terminals to the individual cells you can still measure the voltage of each cell. The voltage of the center cells are measured, with the cell caps off, by simply touching the volt meter probes to the electrolyte of adjacent cells.

Rule of thumb: Old battery below 9.6v for more than a day will not be recoverable. Below 12.0v and above 9.6v indicates a discharge that can probably be recovered.

From the original post:

"If we continue this method any problem will be created to battery charger or to the good conditional battery ?"

OP realizes one battery is bad. He is asking about the consequence of leaving it in place and continuing operation.

The consequence of this choice will be system failure. The resolution, as has been said, is to replace defective components before failure.

Agreed - I was offering a third option because the OP is apparently reluctant to spend the money for new batteries.

Option 1: Keep using with 12.5V & 10V batteries. Risk of system not performing intended purpose & risk of damaging charger. Lowest initial cost, but potentially the highest cost if system or charger are damaged.

Option 2: Replace batteries. Lowest technical risk. High cost.

Option 3: Restore operation of low battery. Low technical risk. Low cost.

Okay, Snave, I'm with ya. However, from the OP: "In my ship to start one generator we are using 2 no of 12 volt batteries..." A ship? Sea vessel? Sorry, I believe this is a poor place to economize on batteries.

GA

Makes sense...

Try swapping the position of the two batteries, if the low voltage follows the battery, then you likely have a bad battery. If the low voltage does not follow the battery, you have a problem with your charging system or there is a drain on the low battery.