Hi guys
What happens if I use a modern 12 volt charger on a 6 volt battery?
If I keep my eye on things, is it safe ?
Stanman

I'm not sure but owing to a faster charge there may be even more volatile gases about and a dangerous possibility for a battery explosion. I just wouldn't try it. Chipper?
Charlie

Not at all recommended.

Thanks
I hear you loud and clear.
Stanman

Charlie,
Since you asked, not a good idea. But you can connect two 6 volt batteries in series and use a 12 volt charger. Don't know if the automatic shut-off feature on a modern charger will work properly so it might be wise to watch them during charging if at a higher amperage rate than the minimum for the charger.

I don't even recommend the series set-up for charging. If the condition of one battery is different, it will provide a different load, which would not be equal to the other battery. To charge equally they must be in the exact same condition.

Parallel charging, a 2 or more 12-volt batteries being charged by a 12-volt charger, is an acceptable procedure.

Ray,
I must respectfully partially disagree with your recommendation against series charging two six volt batteries with a 12 volt charger. While it is far better to charge cells (each 6 volt has three and each 12 volt has six cells) that are equally charged or discharged, it can be done safely with careful monitoring of the process.

If all the cells are approximately equal then it is a no different than a 12 volt battery. It is when there is a major difference in the cells that can be a problem. That can be with either a single 12 volt (like with a bad cell) or two 6 volt batteries in series (negative on one battery to positive on the other and negative charger lead to free negative and positive lead to free positive post) where one has more of a charge than the other. The one with more charge will reach full charge before the other and exhibit greater water loss but with monitoring will not likely be a problem.

There are some RV installations and heavy equipment that use two series batteries to obtain higher output than is available with commonly available battery types or where battery size is a consideration. It is not common.

I agree purchasing a 6 volt battery charger is by far the best option.

I think it will work to hook 2 6 volt batteries in series as long as the batteries are in a similar condition, but as Chipper said the best way is use a 6 volt charger. There are a lot of inexpensive chargers with a 6 volt/12 volt switch.

Many heavy trucks of the 60's and 70's used six volt batteries connected in series with 12volt charging systems with no unusual charging problems. If all cells are equal it will be fine. A 12volt battery is six cells in series in one case and no different than 2 six volt batteries in series, other than the method of connecting.

I'm curious why it seems to take so long to charge a 6 volt battery with my (new) NAPA 6V/12V charger. It has a 10 amp setting for 6V. Neither my "show" Delco or the "daily" Optima batteries show a full charge even after more than 24 hours of charging. The 12 volt setting seems to work fine (on a 12V battery) showing a full charge.

I don't know how the NAPA determines % charge. It can be that the circuit that regulates charge tapers back the amperage rate before it actually reaches 100% or the charge rate and 100% are not set correctly. I have also found with some chargers that they actually reach 100% much before indicated. If you disconnect and then reconnect the charger it will show 100%. Best to check with specific gravity or alternately a volt meter to determine actual charge.

Here is what I found about Optima batteries from another site:
Just do not try to maintain Optima batteries with a Battery Tender, it will burn them out. Use the BatteryMindr made for the Optima. They do not like a sustained charging voltage greater than 13.8 VDC.

AND from the Optima Battery web site:

OPTIMA RedTop Charging Information
The following charging methods are recommended to insure a long battery life - always use a voltage-regulated charger, with voltage limits set as described below.

RedTop Type: 6V
These batteries are designed for engine starting applications. They are NOT recommended or warranted for use in deep cycle applications.

Recommended charging information:
Alternator:

■6.65 to 7.5 volts, no amperage limit.
Battery Charger:

■6.9 to 7.5 volts, 10 amps maximum, 6-12 hours approximate.
Rapid Recharge:

■Maximum voltage 7.8 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.
Float Charge:

■6.6 to 6.9 volts, 1 amp maximum current, time indefinite (at lower voltage).

Mr. Mack,

Thanks for the lengthy reply but I'm not sure I fully understand the numbers and symbols in your message.

The numbers [&#9632] are just part of the text codeing.

I'm curious to know how your 6V generators do in keeping a 6V Optima battery charged. Do you see any difference from a "regular" 6V battery? Mine is only few months old and the engine has not been ran much since November (surgery, weather) so I don't know what to expect. Thanks for any replies!

It is NOT safe to use a 12 volt charger on a 6 volt battery.

It will seriously damage the cells and render the battery none serviceable.

The bottom line is to BUY a 6 volt charger or a more useful combined 6V and 12V charger.

The cheap ones from China are total rubbish, buy a reputable brand, made in the USA is preferred, more expensive, but cheaper in the long run.

I have had to do just that very thing and I hope it lasts as long as me and my car.
Only the best for your Chevy mate, every time........

Peter

This charger is recommended for Optima batteries. http://www.batterymart.com/p-batteryminder-6v-1a-battery-charger.html