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8 volt battery in a Super M

P

Paul A Young

Member
Never tried this before but today I put a 8 volt battery in a Super M because I have always been told that they will start so much better.Well it does turn over faster and starts quicker. The problem is the amp gauge now shows discharge when running. I did not change anything else,do I need to change voltage regulator or generator ?? All is well when you put a 6 volt battery back in.I'm puzzled. Paul
 
Pull the regulator cover, and adjust the points till it works, or just rebuild the starter.
 
"Voltage regulator is not going to kick in and tell the generator to charge till the voltage goes below the 6 volts it was made for."

Actually, voltage regulators for "6 Volt" batteries are set at as much as 7.4 Volts.

With an 8 Volt battery, the regulator needs to be set up to about 9.8 Volts.
 
"Pull the regulator cover, and adjust the points till it works,"


504, that sounds like a recipe to "let all the smoke out"

What he needs to do is to SLIGHTLY increase spring tension on the voltage regulating relay on the VR.

NO "point adjustment" is needed.
 
Remember to polarize the gen and remember it is a positive gnd system. You dont need to change the reg ive worked on some tractors with 8v batts and they will charge the system just fine. The gen sees 8v when it runs and will charge just fine. Take a voltage reading when the system is running before you start adjusting stuff. 8v batts were common back in the 40s when stuff was hard to get because of the war sure made some old cars start in the winter ect. Your gen just mite need some refreshing with brushes ect.
 
You have run into the major disadvantage of an 8V battery:

Nothing is designed to charge an 8V battery.

Electrical systems are 6V or 12V. 6V won't charge it. 12V will ruin the battery.

I'm not sure you can even get a battery charger that will properly charge these batteries.

You can fiddle with the regulator as suggested and it MIGHT work, but then again your generator may only be capable of putting out about 7.5V.

Unfortunately 8V batteries are bandaids that only work until they run down.
 
I built my own 8 volt Electronic regulator which I use on the 8 volt battery from my old truck when the battery is out of the truck during the "off" season. Sort of a trickle charger!!

In the truck I have adjusted the "normal" regulator to where it charges well. The truck is an old 6 cylinder Chevy. Not a worker "bee", just a fun truck.
 
I installed a few 8 volt batteries for customers over the years. You first need to readjust the cutout relay to a higher engagement voltage. Then you adjust the regulated voltage above 8.8 volts, preferably about 9.2. I used a good Allen system analyzer to do this. I never liked the results we had with this system. Some worked ok, but most were not reliable and misunderstood when it came to battery charging, jump starting, lighting and other instruments. I personally would not bother with 8 volt system. I either stay with six and get it up to snuff or do a complete conversion to 12 volts.
 
most won't tell you but a 6 volt delco gen can produce 17 volts I have one with a 12 volt reg and know of a couple more set up the same way and they work o.k.,most will tell you that a 6 gen and starter can't handle the voltage, but they had to be able to stand the high resistance of a 6 volt system,one of the first ones I changed to 12 volts I still own it was done 35 years ago and still using the same 6 volt starter it was equipped with an alternator because at the time I wasn't aware of using a 12 volt reg
 
A 6 volt generator will develop a lot more than 17 volts. I have run them unregulated on a test stand and watched them turn over 30 volts. The problem though is that this higher voltage in turn sends a much higher amperage through the field coils. It is the regulators job to handle the current in the field coils to regulate the voltage output of the generator. A regulator cannot reliably handle more than about 2 or 3 amperes max without excess arcing and burning of the points. This is one of the main reasons todays regulators life is so short as the generator is not properly matched to the regulator or visversa.
We sold a new 706 gas and it had regulator problems immediately. Second regulator shortly failed so further testing showed field coils were actually 6 volt and too low of resistance. New field coils solved problem. Many old 3 brush generators with high, low charge controls have very low field coil resistance, thus high current flow through fields so when you team that generator with a voltage regulator, problems are imminent.
 
This is all well and good, but normal everyday people don't have an Allen System Analyzer in their shops, don't know someone who has one, and are not willing to spend the money on one to tune one tractor's charging system.

...and where are these "most" people who tell you that you can't run a 6 Volt starter on a higher voltage? It's one of the few things we generally agree on in this forum, that's for sure. A 6V starter works JUST FINE on 8V or 12V, as long as you don't crank the engine for long periods of time.
 
You need to crank the voltage regulator up to about 9.5 volts.

8V is a bandaid, either leave it 6V and make sure all connections and cables are good or convert it to 12V with an alternator and never work on it again.
 
Didn't say you need a Allen analyzing tool to set a regulator. Just noted I had one available at that period of time and used it. It makes for more accurate adjustments as you cam simulate a full charged battery which is what is really needed to adjust voltage regulation. Then you can place a load on system to check full current output. I don't own one either but dealer did. My point was that even doing things the supposedly correct way I still did not like 8 volt conversions. Sure some work out, most don't.
 
All you need to do is adjust the voltage regulator to charge the 8 volt properly. The nice part(compared to a 12 volt) is that you don't need a ballast for the ignition and your 6V lights will be a tad brighter too.
 
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