# Using weak 12V Battery in 6V system



## mac293 (Nov 8, 2019)

I have an Optima Yellow Top 12V battery that I have had for years and now will not start my car. It has about 10V. I put it in my Ford Work Master tractor and it works great. However I am wondering if it is too high a voltage and will burn up something. I think the regulator puts out about 10 volts anyway. Any ideas or suggestions on this?


----------



## Hoodoo Valley (Nov 14, 2006)

I know it'll have little effect on your starter. As for everything else, I'd imagine in time it'd wear / burn things out


----------



## Hacke (Feb 22, 2011)

I do not know what harm you may cause the system, but you should not be able to use the battery for a longer time. You need a minimum of 2.3 Volt per cell to charge an acid-lead battery. That means that the generator/alternator needs to hold charge at minimum 13.8 Volt, which it does not in a 6 Volt system.

A 12 Volt battery with 10 Volt voltage is a dead battery, concerning a 12 Volt system. You have some remaining energy stored which you can use for 6 Volt applications for a while, but since the charging is not working, the battery will be drained.

There is one interesting thing about this though. I do not know if it is possible, but if some cells are shorted, maybe it could work as a battery with lower voltage (x*2.3V)?

What voltage do you have across the battery poles when the engine is running?
Have you used the tractor like this for a long time, how many starts?


----------



## mac293 (Nov 8, 2019)

Hacke said:


> I do not know what harm you may cause the system, but you should not be able to use the battery for a longer time. You need a minimum of 2.3 Volt per cell to charge an acid-lead battery. That means that the generator/alternator needs to hold charge at minimum 13.8 Volt, which it does not in a 6 Volt system.
> 
> A 12 Volt battery with 10 Volt voltage is a dead battery, concerning a 12 Volt system. You have some remaining energy stored which you can use for 6 Volt applications for a while, but since the charging is not working, the battery will be drained.
> 
> ...


Thanks for the response: Battery measures about 10 Volts running. I don't need 12 volts so if it would charge to 7 volts it should be fine plus I have lots of battery chargers. My main concern is the electrical system. I was thinking I might be able to reduce the voltage somehow to make it closer to the 6-7v system if necessary. There is a built in resistor that I might be able to change out to reduce the voltage slightly? I don't know if the resistor is before the points or not.


----------



## Hacke (Feb 22, 2011)

That battery is bad and it will not get better. Get a proper 6V battery that you can rely on.


----------



## GreenerDays (Apr 3, 2020)

I don't think you'll hurt anything on it if you don't have delicate electronics on it, maybe fry a thin wire if it runs to a gauge or something over time.. 

I don't know the machine or the specs but if it surpasses the capacity on the diode on the alternator - don't know if that's a problem with returning current.

As Hacke said, I would just get the six volt and be done with it and peace of mind.

I have a couple of dead batteries around and just use them for testing.


----------

