Battery for C
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=137680
Printed Date: 08 Nov 2025 at 7:50pm
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Topic: Battery for C
Posted By: Runamuck
Subject: Battery for C
Date Posted: 23 Apr 2017 at 9:41am
Battery in my '48 C has gone kaput. Currently has an 8 volt battery and checking voltage it charges at 9v+ on low and about 10.4 on high. Has someone adjusted the cut out to work with this battery or do they just work this way? Is an 8 volt bad for the system or is it fine to replace it with another? Can't spend any more than necessary so if 8v is safe I'll just do that this time around. Too many machines to fix right now to do a conversion.
Thanks, Bill.
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Replies:
Posted By: DougS
Date Posted: 23 Apr 2017 at 9:53am
The cutout has little or no effect on the charging voltage. Put another 8 volt battery in if you wish, but a 6 volt battery should work if you have big fat cables and clean connections.
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Posted By: Gerald J.
Date Posted: 23 Apr 2017 at 12:29pm
The 8 volt battery is a cobble for 6 volt systems to allow neglecting starter cable connection maintenance. Battery posts and connectors need cleaning at 6 month intervals with the 6 volt battery.
The generator that charges the 6 or 8 volt batteries has no voltage regulator and is dependent on the tractor operator to use the light switch to turn down the charging current to cut back on overcharging. There is current regulation by the effects of the third brush in the generator and the resistance in the field circuit that is set by the light switch. The main sign of overcharging is loss of water from the battery electrolyte. Batteries need regular checking and refilling of that water when they are used with a three brush generator without voltage regulation.
The regulators used with two brush generators are better on battery life but the solid state regulators like in the 10-SI alternator are much better at protecting batteries from overcharging and getting the batteries fully charged. I built a transistor regulator for VW generator about 1968 and it really did improve battery life.
Gerald J.
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