VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt 8 Volt Battery

22 months ago I pulled the engine out of my '32 coupe and had it completely rebuilt. I kept a tender on the battery and it appeared to keep it charged. We started the engine 2 days ago for the first time since August 2016. We had to recharge the battery. The next day the battery was dead again. I'm not really surprised that the battery needed replacing. I bought a new battery. I bought an 8-VOLT BATTERY. Everything seems to work better than the old 6-volt battery. The engine cranks over very strong. The lights are just a little brighter. The amp meter reads 7 to 12 amps. I'm looking for any other opinions about using an 8-volt battery - good or bad.

There have been many discussions here in the past regarding an 8 volt battery. You can do a search and probably come up with some of the previous discussions. Anyway, the overwhelming opinions in the past are not to use an 8 volt battery. One of the main concerns is the generator output for an 8 volt battery. I would suggest that you return the 8 volt battery and install a 6 volt battery with a minimum CCA of 600. Also install a 00 or a 0000 positive battery cable.

Question...............how does a generator that produces like 7 volts keep an 8 volt battery fully charged? A system with a voltage regulator could be adjusted for voltage but not a pre-volt regulator system.
Or for that matter a battery charger that is designed to charge a 6 volt and/or a 12 volt battery.

With an 8 volt battery the voltage regulator needs to be adjusted to charge more, this can be done if you know what your doing. The light are brighter because they are rated 6 to 8 volts, but you will burn bulbs a lot more. Don't crank the starter very long or it may get hot and fail some day. My 6 volt cars start and run like they should. My last battery lasted 10 years and never burned a bulb or replaced a starter or generator.

Toss the 8 volt and get a good quality 6 volt battery. The switch to a 8 volt merely masks the problem not remedy it.

A well cabled, tuned and adjusted engine designed to run off a 6 volt doesn't need no stinkin' 8 volt.

Just my opinion.

Charlie

I agree with Charlie! Surprised???

You are temporarily hiding the real problem that will catch up with you later. A good 6 volt battery, clean grounding, and proper size cables work great.

Going back to my question how does a 6 volt system generator charge an 8 volt battery on a car that does not have a voltage regulator. There are no adjustments that can be made.

"Olsarge" has a 1932 Chevrolet and if it has the stock charging system there is no voltage regulator......just a cut-out relay.

Mercy! Don't get me started.


Charlie, did you intend that as a pun?

I appreciate all the input. Did you ever ask a question kind of knowing in the back of your mind what the response would be? Well, i pretty much knew what you guys were going to say. That being said, I'm going to keep the 8-volt battery, at least for now. I was already aware of most your concerns. The only real issue I see is the lights may have a shorter life. That's not a major concern as the car is rarely driven at night. As far as the generator, the 6-volt generator with the cut-off switch will charge the battery just fine. Several Model A friends have been running 8-volt batteries for years without issue. The starter doesn't mind the 8-volts as long as you don't grind on it. I've jumped this car off with a 12-volt battery without a problem. The other item is the horn. Again, if you don't hold it down all is good. With the 6-volt battery with an excellent ground the lights were never very bright and were always kind of yellow just like every 6-volt car I've ever seen. Please don't get me wrong. I truly appreciate all your expert advice. That's why I asked and that's why I joined the VCCA over 10 years ago. I will keep you posted. If I suffer any negative consequences I'll surely let you know.

The headlights will be bright on 6 volts if the reflector has been replated. The best solution I have found is to have them nickle plated and then aluminum vacuum sealed. When I restored my car 18 years ago I had the reflectors polished. After a couple of years the silver on them had dulled again. A few years ago i did the above and now they are bright and no yellowing. I may be wrong but I believe the maximum voltage you will get out of a 6 volt generator is 7.8 volts .

I agree. With vacuum sealed aluminum reflectors the 6 volt headlights are as bright as sealed beams making an 8 volt battery totally unnecessary.

Well, I agree with Charlie on this subject ...... a well maintained 6 volt system works just fine.

This is 1 of only a few of Charlies posts that makes sense to me as well.
Tony

olsarge,
it would be very interesting and educational if you could tell us what the charging voltage is when it is running and what the voltage is with the engine not running.

I may have said "don't get me started" in another forum but I don't think so in this one. I'm not smart enough to come up with a decent original pun.

Charlie

Sorry I just saw your post. It's 8.5 volts with the engine not running. I haven't checked it when it's running. I'll try to do that and report back.

The 3 brush generator on open circuit will produce a high voltage depending on speed, at least 30 volts. this high voltage causes a higher current to flow thru the field coils producing an even higher voltage. Eventually something gives in and usually the field coils burn out, Early 3 brush electrical systems had a fuse in the field circuit to prevent this from happening, blown fuse no field current and no output voltage. A 3 brush can easily charge an 8 volt battery but would need a voltage regulator adjusted to 10 volts to reduce the current once the battery is fully charged. The limitation on the generator is the heat produced in the armature due to the charging current which is usually limited to 20 amps. The 6\8 volt headlamp globes have a life of only 100hours so running them at 8 volts will reduce their life even further.

Ok. I checked the system this morning. With the engine at an idle the voltage at the battery reads 8.5. I checked on either side of the cut out switch and it also reads 8.5 volts. The ammeter reads 8 amps at idle and about 12-14 amps under acceleration. I don't have a tach so I don't know the RPMs under acceleration.

I can guarantee that it is only a matter of time before 14 amp generator output will begin to melt the solder in the armature. Those generators do not have a vent or enough air flow to keep the temperature down at the higher outputs.

I totally agree! 14 amps on that generator is way too high. Should have a max. output of about 10 amps.

Thanks guys. I will adjust the third brush to give a max of 10 amps at speed. I'll update this post when I do.

Good move. 10 amps is plenty to take care of any requirements unless you have halogen replacement bulbs or another other high draw component.

No, the car has all original lights. I wired the cowl lights with the headlights but that's not an issue. I had the generator rebuilt two or three years ago. Then 22 months ago I pulled the engine for a complete rebuild. I was told to set the generator to 7 to 10 amps. It's 7 amps at idle. I'll set it for a max of 10 amps and disregard the idle amperage.

I set my generators for 6-8 amps at speed. Don't have a problem with battery running down unless I drive an extended period with lights on (which I occasionally do to keep for over charging the battery). Higher amperage boils the water out of the battery and reduces the battery life. If the underside of the cell caps is black then you are over charging.