Re: Starter from 24V to 12V

Posted by Texasmark1 on May 17, 2015 at 05:20:19 from (184.20.54.10):

In Reply to: Starter from 24V to 12V posted by Traditional Farmer on May 17, 2015 at 03:02:10:

This is textbook material as there is too much to it for a response here.

Starters are usually of the series wound type which means current controls the rpm for a given load. If you can get enough current to the starter at 12v you ought to be able to do the job in my guesstimation!!!!!

Question is the DC resistance of the starter windings. Since the current would have to double with the voltage halved, you might not be able to obtain adequate current even increasing the size of your interconnecting wires between the batteries and the starter due to that problem, and doubling the amperage capacity of your batteries by hooking 2 12v batteries in parallel (+ to + and - to -). Course if you are running 24v now with 2 12v batteries in series, you can just hook them up in parallel and the battery part of the problem is solved.

Going to guess that your engine won't spin fast, but strong. By strong I mean that the starter will whir whir whir like when you have a partially discharged battery in a normal system, but unlike that situation it will continue for a longer period.

One thought that just occurred to me is that in starting a Diesel, especially in cold weather, you have to spin it up fast enough to generate enough compression heat in the combustion chamber to get it to light off and that might not occur with a slower spinning starter. Course you could use a heater or starting aid to solve that problem.

What will it cost you to try? A voltmeter and 1 new interconnect cable initially if you are currently using 2 12v batteries in series.

Obtain 1ea. 0 size wire with suitable terminals to jumper between the batteries. Then remove the wire that currently connects between your two series batteries and connect it to the same polarity post on the other battery rather than the opposite polarity post as it is currently. Place the new jumper between the remaining two posts on the batteries......+ to + and - to -. You now have 12v (batteries in parallel) but twice the current capacity from the batteries.......the rest of the circuit is the question.

Get a voltmeter and setup to 20v DC (lowest DC scale on my meter but anything above 12v). Place the leads across the starter, hot lead to starter case (usually). Ensure that your batteries are in good order (not sulphated up internally) and fully charged. Spin the engine and while doing so, measure the voltage at the points mentioned on the starter.....hot terminal to starter case. If you have less than 10v your battery to starter wiring needs to be upgraded. I use size 00 for that on my 100 hp diesel.

If you do, how does it work?

Using a 6 v starter on a 12v system is a no brainer. Spins like crazy and only thing that keeps the starter from burning up is that you are only on it for a few seconds. This is a different situation.

Good luck,
Mark

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