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Hi all.

I have just installed 2x150w panels solar in parallel with a bn series mppt and mt 50 control panel. So far it has been ok, however, after running engine for a while this morning, in hot sun, the domestic alternator charge warning light came on bright. Thought the belt had broken to start with but it was ok. The light was going off and coming on sporadically. sometimes flashing. batteries were showing full-ish on the mt50. I disconnected the panels and all back to normal! so it appears some type of feed back? could it be a dodgy diode in the alternator? or something else? too much power from battery light feed to alternator because of Solar? Please, ideas anyone? The Alternator is wired in separately with a switch in the exciter/light feed  wire. alternator and solar charge cables feed to the same battery terminals. should I change to a different terminal? Help!!!

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I think it is just because the batteries are fully charged / solar controller is taking the battery voltage slightly above the alternator regulated voltage, the alternator regulator is fully shutting down. With some types of alternator this seems to bring on the warning light. So not necessarily an alternator fault. If you switch on a big load (tunnel light, unless it’s an LED, for instance) you will probably find the warning light goes off.

 

If it annoys you, either switch off the alternator exciter/light feed or disconnect the solar panels.

 

 

Edited by nicknorman

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I am seeing this reported a lot with more boaters fitting solar that it shuts the alternator down, I have not read of it causing any problems

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11 hours ago, ditchcrawler said:

I am seeing this reported a lot with more boaters fitting solar that it shuts the alternator down, I have not read of it causing any problems

Not here! But then the solar charge voltage is set just below the alternator voltage.

 

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It will cause no harm, if it worries you just lower the solar charge voltage by a few hundred millivolts using the MT50, the solar will then shut down when the engine is running and your alternator light will be out. You are of course losing the free electricity and replacing it with electricity generated using diesel, but as it will only happen on full batteries we are only talking tiny amounts of electricity.

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Interestingly my system does the opposite, the alternator gives 14.4 volts, and the float on the solar is at 13.6 so the solar just goes in to im fully charged mode, and the lights indicate this.

the alternator just merrily runs at 14.4 day and nightover riding the solar

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Thanks all. I will probably switch of the solar whilst cruising! luckily there is a breaker in both sides so easy to do. 

I thought they might have been duelling using lightning bolts Tree Monkey!

  • Greenie 1

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