Charging 6 and 12 volt batteries

I've charged a lot of car/boat 12 volt batteries with my battery charger but now need to charge a battery off a riding lawn mower/tractor and want to check on some things first. I guess I'm close enough to "home repair."
First, if there are 6 places to add water to the battery then it's a 12 volt? If 3 places, then a 6 volt? I thought lawn tractor batteries would be 6 volt, but this one has 6 places (cells?) to add water and yet it is smaller than the average car/boat 12 volt battery. So, which do I have?
Second, my battery charger will work on either 12 or 6 volt. I've always just selected the 12 volt setting for what I knew to be 12 volt batteries, connected the terminals then plugged into the AC and followed the specific gravity of the solution with one of those floating ball aspirators, when all 4 float, it's charge is OK. If I do have a 6 volt battery, can you use the floating ball thing to follow the charge or is the specific gravity different for 6 or 12 volt batteries?
Thirdly, when I set my charger on the 6 volt option, it doesn't come on until I turn a separate dial which clicks on and allows me to adjust the output of the charger from 0.2 to 1.2 amps. What amp output should I use to charge a 6 volt battery?
Thanks.
Chet
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CGB wrote:

Likely 12 volts. Why not put a volt meter on it and see.

Same specific gravity for 6 or 12 v

If you are going to watch it I would use 1.2. That is not very high. If you are planning to turn it on and go to bed I would suggest 0.2

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Joseph Meehan

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Assuming it has headlights, look up the voltage for the bulb type.

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CGB wrote:

It is 12 volt.

The same. Each cell is about 2 volts. A hydrometer is a better device to check the charge. They cost about $3.

That must be a very low current charger. More like a "trickle charger". Usually they are at least 12 amperes.
For more information on batteries and how to charge them try:
http://www.batteryfaq.org

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Right.
Why? I believe that all, reasonably modern, gas-powered, self-starting machines use a 12VDC system.

It's a 12-volt battery. It is probably in the same league as those found on most motorcycles.

You don't, so everything else is moot. Charge it at 12-volts.
If your charger is bigger than 10-amps, you would do well to get another, smaller one just for your lawn tractor's battery. More than 10-amps can boil-off the electrolyte, warp and crack plates and ensure that you'll soon be buying another battery - at a lawn tractor or motorcycle parts store.
Even at 10-amps, you should carefully watch the water level during charging. 10-amps may be too much for the size battery you are charging.
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JR

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On Sun, 12 Mar 2006 12:39:58 -0600, Jim Redelfs

I have a solar electric fence charger that puts out 12 volts to an internel 12 volt gel cell battery. I only use this fencer for emergencies when the power is out or I want to make a temporary corral for horses and it's too far from an outlet. The rest of the time, I ran a few wires out of the device, directly off the solar cell. I clip it to my mower battery and the battery is always trickle charged, It dont cost me a cent for electricity. My mower battery is 7 years old and still works fine.
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Thanks for the replies. All set.
Chet
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In that case, only add half as much water.

Darn, I was just goofing, but I was right.
12 volts.
The size doesn't have much relationship to the voltage. Just look at 9-volt batteries for transistor radios etc. They have 6 cells in them, stacked one on another. (Dry cells are 1 1/2 volts. Lead acid cells are 2.1 volts.)
One reason lawn mowers could get by on 6 volt batteries is that the grass doesn't grow when it is below freezing, or even below what, 40? So the 6-volts stays pretty close to 6 volts. My 6-volt '50 Olds started fine except one night when it was 0 degrees F, when the 6 volts was probably 3 volts. OTOH, riding lawn mower tractors are also used in the winter to plow snow and for racing.

That's not the most precise way to measure, but it's probably good enough, and yes, it's the same for 6 and 12. Because each cell is 2 volts and the chemistry is the same, including the weight of the solution.
BTW, they could make both dry and wet cells out of different materials, and get different voltages. But it's standardized. (Except for mercury batteries and who knows what else. I don't think they have any tractors that use mercury batteries.)

I consider a 1 amp charge slow, and have never heard of anything slower. but if you have time to wait, I think the slower the better. For both 6 and 12. IIRC a 12 volt battery takes about a day to charge with a 1 amp charger. I never measured how many amps a 1 amp charger puts out, but I'm going to figure it is 1. At .2 amps, it would take 5 days, although it might be enough to start the car earlier than that. It takes a lot less to start a lawnmower.

You're welcome.
David.
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If it has 6 holes, it's 12volt. Just figure 2 volts per cell. 2X6 or 2X3=6. Mower batteries as well as motorcycle ones are still all 2volts per cell the same as a car battery. Just lower amperage. The size of the cell determines the amps, the number of cells is the voltage.
By the way if it has 7 holes it's a 12volt FEMALE battery. :)
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