Re: Using 12 volts only for "starting" purposes

Posted by Tim Cole On 2009/10/21 17:01:01

Except for emergencies I would recommend checking the no-load voltage first and the cranking voltage second. For example, I had to cope with a situation of a car that was stuck up hill in a trailer with a dead battery. Now if you hook a 12 volt battery up to that thing and hit the starter, the voltage may only be 6.5 volts and the 12 volt battery is thus only dumping in boost amperes. The faster the starter is turning the less the current draw and thus the lower the likelyhood of damage to the starter. Six volt wiring is heavier to handle the higher current required to obtain a given level of power at lower voltage.

I dealt with one case where they were using a jump pack to start a 120 for years. And buying batteries by the wagon load. When I finally looked at the car I sent the regulator out for service because the ammeter was being pinned. I got a call that the unit was good (???) even after all that abuse. Next, I checked each wire and found that the reproduction harness was wrong and the generator was being full fielded all the time. After correcting the problem the charging system worked perfectly even after years of abuse. Although, I suspect low compression is hiding the true condition of the starting system.

I saw a film once of a brand new six volt car cranking over and it was really fast. Faster than any of these cars today, so I suspect that one day all these starters will finally die without new armatures and fields.