The Stovebolt Site Forums The Shop Area The Electrical Bay two 8 volt batteries?

Hello,
My GMC 453 fire truck just got delivered today. I am assessing what I will need to do to get it running. It has two 8 volt batteries, and enough wores on the generator to make me dizzy.
Photos can be seen here http://home.comcast.net/~chriseye/ft.html

Should I buy two new 8 volt batteries?

Has anyone ever seen batteries mounted on the floor like this?

Can I bypass all of this and install one 6 volt battery, just to get it running?
Thanks,
Chris

It was common to change to 8 volts if 6 volts did not seem to start an engine. The 8 volt batteries are probably in parallel which still only gives you 8 volts to the starter. Emergency equipment was often speced redundant. Only one battery is hooked up now. 6 volts will turn a 302 GMC if the starter is good. It probably had some kind of heavy duty charging system. The 8 volt charging would be achieved in the regulator. Are you trying to restore it to original or are you just wanting to make it drivable. If you just want it to run, one 6 volt battery will do. Get a 6 volt generator and regulator or switch it to 12 volts with a 12 volt gen and regulator or simply with a 1 wire 12 volt alternator.

PM sent.

I can't tell from your pictures, but the generator looks somewhat like an early Delco alternator, but it could also be a Leece-Neville alternator. Alternators were used on emergency vehicles that had high electrical loads, with Leece-Neville being a common supplier. The AC boxes in one of your pictures indicate use with a 6-volt alternator, which also indicates use of an alternator on the truck. If the truck has an alternator, look for one of two indicators: either a dry-plate rectifer assembly, a foot or so long, in front of the radiator, or six diodes in the rear frame of the generator. The diodes may look like thin hex bolts, 3/4" or so in size (I don't remember, specifically), that don't seem to hold anything in the end frame.

The dry-plate rectifier typically is an assembly of square plates, 3 or 4 inches square, that have either discs or smaller plates alternately located between the larger ones. The dry-plate rectifer will also have large wires attached to it from the generator- there may be three wires from the generator. If you can find the part number on the generator, I'm sure you can find information on it, but I wouldn't start changing anything until you find out what you have. You could end up with an unnecessary nightmare.

Harvester

I forgot to mention that a dry-plate rectifier will also have connections to one of the batteries.

Harvester

Thank you Harvester, Marty, and crenwelge,
I spent a little time cleaning the truck today. It has a 7 volt 100 Amp Leece Neville Regulator, it also has the dry plate rectifier in front of the radiator. Can I assume that this will work with both 6 volt and 8 volt batteries? Can I use the 6 volt battery from my one ton to get it running, and if I get it running should I buy 2 8 volt batteries?
Under/in front of the seat are two battery shut off switches, would one of the batteries be for the alternators, and one for the truck?
I have updated my fire truck page and added more photos.
On the side of one of the batteries is written by hand "Olden", might this truck have come from Olden Texas?
I can't wait to give it some gas and a spark!!!
Thanks,
Chris

The ignition is 6 volt. The 8 volts was for extra cranking power out of a 6 volt starter. If a 6 volt battery will turn the engine, it will run on 6 volts. Something I have done in the past to get old engines running is hook a 12 volt battery to the starter to make it spin fast. I then disconnect the wire going from the ignition switch to the coil and hook a 6 volt battery to the coil and ground. That way I get the 12 volt cranking power and a full 6 volts to the ignition. This is of course only to get it running because there will be nothing to charge either of the batteries.

Given the complexity of your electrical system, I would not boost the system with 12 volts for starting. Twelve volts on a 6-volt system normally doesn't hurt anything, but with your sytem, it is likely to cause unexpected trouble. At least you have identified your charging system as (probably) a Leece-Neville 100 amp, 6-volt system. Since the truck currently has 8-volt batteries in it, you could use either 6- or 8-volt replacements, but the voltage regulator is probably set for 8-volt operation, probably set for about 9.6 volts- I don't remember a typical voltage setting for 8-volt systems. Be careful with the dry-plate rectifier setup- I don't know if they are as tolerant of mistakes as are metal-case diodes- they might be more tolerant of mistakes. I've never burned up a high-power dry-plate rectifier, but in low-power systems, they will clear the room in a hurry if they burn up...

Harvester

PLEASE do not use 8-volt batteries in that system. All that will accomplish is damage the other components like the regulator and possibly the rectifier. The Leece-Neville alternator system is excellent quality, and there should be enough technical information available to get it back in good original working condition. To charge an 8 volt battery, the regulator voltage must be set to 9.5 volts or so, and that's rough on all the electrical accessories. It's a remote possibility your system has a series-parallel switch that routes 12 volts to the starter for cranking by connecting the two 6-volts in series, and then switches the batteries back into parallel, 6 volts for charging.

That's usually used on Diesel engines, but if your rig was sold in cold country, it might have been set up that way for reliable starting.
Jerry

I guess I did not make myself clear. I was only suggesting to put 12 volts to the starter. This can be accomplished by removing the cable from the starter to isolate the starter from everything else. My first choice would to be starting it with a 6 volt starter and a 6 volt starter should crank a 302. However, if the starter will not crank well with 6 volts, a 12 volt battery might. 8 volt batteries were usually installed when 6 volt batteries cranked too slow. I think Tam is trying to get the engine to running before he tackles any of the other stuff. Harvester, thanks for pointing out that I didn't make myself clear.