6volt alt with a 8 volt battery

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Schweck1914
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6volt alt with a 8 volt battery

Post by Schweck1914 » Thu Jan 08, 2026 10:24 am

Will a 6 volt alternator putting out 40 amps charge a 8 volt battery...
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TXGOAT2
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Re: 6volt alt with a 8 volt battery

Post by TXGOAT2 » Thu Jan 08, 2026 10:38 am

Probably not, or not very well. The regulator on a modern 6 volt alternator would probably sense the 8.5 volts at the battery and assume the battery was fully charged whether it was or not. A Model T generator will charge an 8 volt battery, since the T generator has no automatic voltage regulation, though it's not a very good idea. A modern 6 volt system will provide about 7.5 volts, and a modern system designed for an 8 volt battery will provide up to 9.5 to 10 volts. (If one exists) The best solution is to use a good 6 volt battery and a stock T generator with a modern voltage regulator added. If your starter is bad, fix it.
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Jeff
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Re: 6volt alt with a 8 volt battery

Post by Jeff » Sun Jan 11, 2026 1:35 pm

Everything Pat said is accurate. Its not the current that matters - its the battery voltage the alternator "thinks" its trying to charge, in your case 6v. Alternators are not adjustable.

FYI, my 6v Model T Voltage Regulator can be adjusted to charge an 8V battery to 100% full- I've done the mod for half a dozen folks with great success. But you need to use a Model T generator for it to work.

Jeff
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Original Smith
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Re: 6volt alt with a 8 volt battery

Post by Original Smith » Mon Jan 12, 2026 5:26 pm

Keep it original! A good 6volt system is hard to beat if you have good wiring, and a good battery
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J1MGOLDEN
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Re: 6volt alt with a 8 volt battery

Post by J1MGOLDEN » Tue Jan 13, 2026 4:03 pm

No one thinks of the Wattage a generator can produce and neither the voltage or current is the limit alone.

You can safely double or halve the generator output, although very few people do that change.

So, for 48 Watts, a 6.4 volt battery can charge at 7.5 amps from the generator.

Wit a 12.8 Volts fully charged battery, you can adjust the generator to a 3.75 Amp output and it will last forever.

The charge will increase to 5.6 Amps with an 8 Volt battery and never cause any problems.
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