Overcharge protection

[andsarkit]

I think you should be quite clear about what you are trying to achieve here.
Battery isolator switches that don't isolate the battery are not your best friend when the smoke starts coming out.

The diodes only prevent energy leaving the battery. Is it likely that another energy source such as the alternator, battery charger or solar panels would cause smoke in the battery and then not be able to be stopped at source?
Most people seem happy to parallel batteries without individual isolation when a shorted cell in one could be damaged by energy flow from the next battery.
I agree that modern alternators are very rugged and most car ones will happily last 10 or 15 years . Semiconductor technology has improved greatly and the diodes will take a lot of abuse. I'm not sure the problem still exists although perhaps some boats have very ancient engines with equally old alternators.

 

[William_H]

Bogus devices and fake video. Quite a bold claim.

Yes I am aware that Sterling products have a good reputation and I am brave to call out the apparent inconsistencies with the video. Perhaps a bit embarrassed.
But the inconsistencies are still glaring especially the breaking 150 amps. This would normally produce a small arc welder.
Regarding the fact that he did not demonstrate that the alternator would fail without the protector that is perhaps understandable. I think the fact is the diodes in the alternator might or might not fail with having the load disconnected.
Diodes are pretty robust. They fail from excess forward current generally from overheating either rapid high current short term or long temr overheating with inadequate heat sink. I don't think this is how an alternator diode would fail. Diodes also have a max PIV peak inverse voltage. Thsi is the voltage which will break down the semiconductor due to too much voltage backwards. It can result in the diode becoming a short circuit or completely melted to open circuit. I think this is the mode of diode failure with no load on the alternator.
In answer to ansarkit any of the six diodes connected to the stator windings could fail from back EMF from the inductance of the windings with load disconnected when the blocking ability of the diode is exceeded.
Now I don't have specifications for the PIV rating of diodes used in alternators. My suspicion is that PIV rating will improve on didoes over years so that an old design alternator might use diodes more marginal than those using more modern diodes.
Maintaining the load seems to be the best answer. As in not breaking the load. I suspect may be wrong that in trying to catch and supress spikes at the output you will not protect the diodes so well inside. (up steam) ol'will