Solar while driving confusing alternator sensor. Not gen light on

neoneddy · March 25, 2018, 01:43:46 PM

This was my first big trip after adding solar and having a couple's DC system to help charge from alternator.

So this morning pulling out of Rochester MN I noticed my not gen light was on , I saw the system voltage at 29.2 or so.

My batteries were almost full but the mppt (victron) I have set to hit 29.6 before moving from bulk to absorbsion . I found the specs on the deka battery site saying how to charge etc, so I set it up that way. Anyway I noticed it would never go above 29.4v and sometimes would dip to 28.9, as soon as it did the light would go out. I could kick on the heat fan and that would bring the voltage down in the 28s, and it's smooth sailing so long as I kept the fan on, but I was getting cooked out.

I think the no gen sensor is looking for a power flowing from the alternator, since it outputs up to 29v if the system voltage is higher it thinks nothing is flowing.

I'm thinking of stopping the bulk voltage at 28.9 or something, problem is I don't hit 85% SOC (victron BMV) at that voltage.

Anyone else encountered this?

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buswarrior · March 25, 2018, 02:18:14 PM

Sometimes, with full batteries, a busnut would see a no-gen light.

Turning on the headlights would work in that case.

Basically, no matter how youdo it, if the alternator stops charging, broken or topped up or 2nd charging source... the no-gen lightis doing its job by coming on.

Happy coaching!
Buswarrior

bobofthenorth · March 25, 2018, 02:45:32 PM

Don't worry about it. And definitely don't mess with the charge voltage. Its a minor annoyance but it confirms that everything is working. Now if your tach was taking its signal off the alternator that would be a problem. As it is, if it bothers you, do like Ewen said - turn the lights on.

neoneddy · March 25, 2018, 03:31:21 PM

Great to hear it's no big deal and everything is working normally.

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TomC · March 25, 2018, 03:59:24 PM

I know AGM batteries are supposed to be no higher than 28.2 volts. I had to disconnect my tiny alternator on the generator because it was messing with the giant 50DN alternator. The voltage regulators are sensitive. I also run down the road with my headlights on. Good Luck, TomC

Geoff · March 25, 2018, 07:12:23 PM

I took the "no gen" lightbulb out and just look at my voltage meters.

richard5933 · March 26, 2018, 02:51:22 AM

Are you running the solar into a battery bank that is also being charged by the bus's alternator? If so, that seems like a good way to confuse the bus voltage regulator. I've read about a similar problem with the 4106 setup. If the bus alternator is feeding the same battery bank, then do you need to have the solar connected at the same time?

bevans6 · March 26, 2018, 05:29:26 AM

The no-gen light is driven from the relay terminal of the big old bus alternator. If the no-gen light is on it just means that the alternator has turned off and is no longer producing power. It turns off because the voltage regulator senses the battery voltage is higher than it's set point so it stops energizing the alternator field coil. 29.6 seems high to me before going to absorption, but at least one of my smart charges goes even higher than that, so it's probably OK.