The Stovebolt Site Forums The Shop Area The Electrical Bay 8 volt battery questions

Thought I would start a thread based on another posting and want to know more about 8 volt batteries.

I understand that the generator will work harder to keep an 8 Volt battery charged. Can a shop modify a generator to charge an 8 volt battery? I’m assuming that “working harder” means that it:

1. May not fully charge an 8V? Or can fully charge the battery but it will take longer?
2. Can charge an 8V but it strains the windings or creates additional heat?

How is the Regulator adjusted to 9.5 volts? Why 9.5V?

8V on 6 volt bulbs:

I understand they (6V) will burn brighter on 8V but, what is the downside?
Do they burn hotter and shorten the lifespan? Is there such a thing as 8V bulbs?

Dumb question here but will ask for the sake of posterity:

Will a 12V bulb burn dimmer on 8V? Or not work at all?

Will an 8V battery risk damaging my NOS 1946 GMC 6V gauges? They took some effort to acquire. Same goes for 6V heater motor.

What is required to run an 8V battery to avoid the issues of over voltage on 6V gauges and accessories?

I see online that there are 8V battery chargers and trickle chargers.

I’m sure I will have more questions... I would like to learn more about this because my 12V brain runs dim when I feel like I am running on less information voltage. Thank you. Tom

There is nothing good about using an 8V battery! 6V systems with the proper sized cables and good clean grounds mitigates any need to use an 8V battery.

Tom, you ask quite a series of questions, so here goes:

"Can a shop modify a generator to charge an 8 volt battery? I’m assuming that “working harder” means that it:

"1. May not fully charge an 8V? Or can fully charge the battery but it will take longer?"

The generator does not require modification, but the voltage regulator needs to be reset in order to charge an 8V battery. It will stress the generator a bit more.

A generator and its companion voltage regulator set for a 6V system will not charge an 8V battery, since the nominal setting of the regulator is below battery voltage. The 6V system voltage regulator is typically set to 7.5V, plus or minus just a few tenths (minimum 6.9V per old Delco info - see first image, p.6 of Delco 1R-116A, dated 8-1-60). An "8V" battery is actually at 8.4V when fully charged, similar to a "6V battery" being at 6.3V when fully charged. The voltage regulator would need to be adjusted to greater than about 9V, in order to fully charge the 8V battery.

"2. Can charge an 8V but it strains the windings or creates additional heat?"

Yes, the generator can support charging an 8V battery once the voltage regulator is adjusted to set the system voltage higher than the battery voltage. That may be a bit more stress on the generator, and probably produces more heat in its windings.

"How is the Regulator adjusted to 9.5 volts? Why 9.5V?"

The relays in the regulator can be adjusted to set the voltage higher, and 9.5-9.6 is sufficient to charge an 8V battery. It's a bit fiddly, and takes some test equipment to do the adjustment correctly. The procedures are in the old Delco literature on how to properly set a V/R (Second attachment, full copy of Delco 1R-116A in .pdf format). The charging voltage, about 9.5V, is chosen so that the system voltage is greater than the battery voltage (at full charge of 8.4V), and high enough so that the charging rate is reasonable. A battery only charges if the voltage applied to it is higher than what it produces.

"8V on 6 volt bulbs: I understand they (6V) will burn brighter on 8V but, what is the downside?
Do they burn hotter and shorten the lifespan? Is there such a thing as 8V bulbs?"

The downside of running a "6V" bulb is shorter bulb life. The incandescent bulbs spec'ed for the 6V systems are actually rated for 7.5V or thereabout, since they need to tolerate the higher system voltage set by the V/R. They are fine at 8V. But at the higher system voltage (about 9.5V), if set to properly charge an 8V battery, they will be brighter, but they will have shorter life (considerably hotter filament). An "8V" bulb would need to be rated 9.5-10V for reasonable life in the system. I'm sure there are such things, but I've never researched for socket-compatible bulbs.

"Will a 12V bulb burn dimmer on 8V? Or not work at all?"

Nominal 12V incandescent bulbs could be used, but they will be much dimmer than if properly powered. It's possible that some 12V LED bulbs would work, since they typically have a wider voltage range tolerance. That's something else that would need to be researched, and is probably specific to individual LED bulb brands.

"Will an 8V battery risk damaging my NOS 1946 GMC 6V gauges? They took some effort to acquire. Same goes for 6V heater motor.
"What is required to run an 8V battery to avoid the issues of over voltage on 6V gauges and accessories?"

There is some risk, mostly to the fuel gauge, if the gauges are the same as the Chevy gauges (temp and oil pressure mechanical, so system voltage doesn't matter, and an ammeter measures current, and doesn't "care" what the voltage is set to). To be safe, it seems a true Runtz resistor setup could be used with the fuel gauge, similar to what is done for 12V conversion. Having said that, I know quite a few who have run 8V batteries (usually not set to properly charge), without damage to the gauges.
Not sure with the heater motor, it may be OK, but will run faster, and the heater speed switch, if so equipped, could overheat. Probably safer to put in an appropriate voltage reducer. YMMV.

"I see online that there are 8V battery chargers and trickle chargers."

Sure, 8V batteries were commonly used in tractors, and some golf carts. When I was a teenager, my friends and I would "borrow" tractor batteries from one of our Dads or Uncles, to get our cars to start in the winter (upstate NY). We never bothered to worry about charging - we'd just swap for the next one when the cranking got slow. Risk to the system? Never gave it a thought. Dumb kids.

As a post-script of sorts, IMO, the 8V conversion is more problem than it solves. I'm running a 6V system on my '53, and with appropriate cables, grounding, and some maintenance, all is fine. If I were to convert, I wouldn't bother with 8V, but would make the jump to 12V. Conversion complexity is about the same, and 12V components are readily available. I just haven't seen the need to move from 6V for my purposes.

Cheers!

Doug

DrDoug: Thank you for the time to write and explain and I agree, Dunfire, I would prefer a well maintained 6V system. Oftentimes, when I meet someone who likes the old trucks, and they visit the shop, I tell them I am building this 46 GMC to stock condition including the 6V system. They invariably say that 8V is better than 6V.

But, I don’t know enough to respond or feel confident in having that discussion. So I listen and sort of understand. Up here in Maine there is an old saying: “Hard tellin not knowin.”

Thank you again, for taking the time to explain and write a well composed response. I understand now. I’m sure others now and in the future will appreciate the response as much as I do. Tom

In the mid-1950's my father ran one of the best independent auto shops in Nashville Tennessee. He was approached by a local battery manufacturer to develop an installation kit that would allow the guy's 8 volt batteries to work properly in 6V vehicles. By using resistors in several key circuits to control the excess current produced by resetting the voltage regulator, Dad was able to come up with a system that worked. The parts and labor cost was prohibitive, however, and the idea never got past the planning stages, mostly because the battery guy was not willing to accept the extra cost of selling a system that worked properly.
Jerry

They invariably are misinformed.

Another gimmick battery that I was actually involved in manufacturing for a time was the "6-12" battery. It was a 12 volt battery case with a Ford-type starter solenoid that replaced the cell connector in the middle of the six cell groups. It was essentially two 6V batteries wired in parallel for charging purposes, headlights, and such, and connected in series for starting by energizing the solenoid. I worked for a few months between college semesters on the assembly line at the same battery factory that sold the 8V batteries Dad developed the adapter kit for. Every few weeks we would make a limited run of the 6-12 batteries.
Jerry

Series/Parallel switches were used on heavy diesel trucks for many years. They required four, big, six-volt batteries. The most common electrical failure on these trucks was that switch. I used to carry a spare in the seat box. What I believe killed the switches was the "flyback current generated as the considerable magnetic field in the starter collapsed when the switch opened. In those days there were no solid state diodes to ground out the flyback, so the current arced across the switch contacts as they opened. They just have 12V starters nowadays and start just fine.

Later I worked for a farmer who had an I-H KB6 with a six-volt system. It had one of those series/parallel batteries Hotrod speaks of to get it to start when hot. Of course the reason I know all this is that it no longer worked and he asked me to fix it. The solenoid was not just a Ford starter solenoid but a specialty unit that was not available. So I suggested the 8-volt battery and the farmer said he'd done that and it hadn't worked. Then I suggested a rebuilt starter and he said he'd done that. So I dismantled the starter and checked it very carefully and found the armature shaft was bent; not much mind you only about 0.020 or so but that was enough for the armature to drag on the field poles when hot. These used a long shaft that stuck out of the windings about 8 or 10 inches before it was supported by a bearing. If the spark was advanced to the point where the engine would kick back against the starter it would bend the shaft. I had it straightened and the problem disappeared for as long as I worked there.

Another common problem with rebuilt starters, generators and alternators is that after the armature is rewound, the rebuilder sometimes chucks it in a lathe and takes a cut to ensure that the armature is concentric and won't contact the field shoes. Doing so opens up the internal air gap and reduces the output. Doing this on BMW air-head motorcycle alternators reduced the output from 20 to about 14 amps and the batteries would run down when the bikes were ridden in town with the lights on as required after 1975.

That air gap thing is also important on small engines with magnets in the flywheel to power up the magneto ignition. It's surprising how much better an old Briggs & Stratton engine starts and runs if a 3X5 inch index card is used to set the air gap between the flywheel magnets and the ignition coil pole shoes. I actually learned that trick from a kid who was competing in a high school technical skills contest that I was judging about 30 years ago!
Jerry

During the 70's, while owned by the previous owner who we knew well, my truck sat on the street all winter long in Minnesota so that Mr. Larson's new Torino could sit in the garage. Being a Ford, even in the garage the Torino would struggle to start when the mercury was down around -25. In that case, the kids got driven to school in the 53 pickup, which would always start, even on the street, buried under snow. 6 volt original system.
I have used an 8-volt battery a few years, without serious damage being done, but I am back on 6 volts. The truck has other problems, but it starts great. Karl

One can spend the money for a Petronics brand system but then you have the cost of the battery which is expensive. Regulator need to be set to no more than 9.4 volts and be cautious you don't buy a positive ground battery system. All in all it is a waste of time and money. Older six volt bulbs and motors can be damaged. Good six volt cables and polished double grounds will solve your problems. Organbuilder you are so right. A well maintained six volt system will start no matter the temp. Doc.