{Chrysler 300} Generators and alternators and batteries

Since the subject has come up, a word of caution on the subject.

In the early 2000’s when we purchased the 1947 Desoto and started using it as our daily driver, I got rid of the regular battery and switched to an Optima 6V.

We started to have problems in the charging system. We would get a slow, over a month or so, increase in AMP draw showing up on the AMP gauge. It would get to the point where I was running around trying to figure out where the power was going. It would also cause a generator to burn up.

We changed generators and alternators. We also killed batteries. Nothing stopped the problem.

I will not bore you with the entire story of all the detail work we tried to run the issue down.

This is before Optima was sold. Their engineers sent me a couple of batteries and had me ship the old ones directly to them. What we figured out was going on was that since the resistance in an Optima battery is lower than a lead acid battery, the mechanical regulators would think they were not fully charged. So, they would supply a slow but steady trickle overcharge to the battery causing the plates to melt and then they short which causes a current draw that one sees on the AMP gauge and can kill the alternator as well.

Now is the interesting part. On cars that sit a lot, the natural discharge rate will drain the battery then one drives it, and it charges it back to “normal” then it gets parked and drains back down. That is why people who do not use their cars all the time may not see the issue. Use it daily and it can happen. Use a battery tender and it can happen.

Now this problem can show up on SOME but not all mechanical generators. No real way to tell which ones. Internally regulated alternators do not exhibit the issues, nor do digital external regulators.

I switched to an internal regulated alternator and the problem never came back. Interesting in that about a year later there was an article in one of my flying magazines about this same issues. A lot of people with vintage aircraft were switching over at that time to sealed batteries and they had old mechanical voltage regulators and had issues. They traced the same problem down as I did, and the FAA issued a directive on the subject. Use a sealed battery and you must switch to a digital regulator.

So, if any of you with generators or alternators with mechanical regulators experience anything odd on the charging system and are using a sealed battery, keep the above in mind.

James