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Old 17-05-2021, 16:42   #1
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Solar and Tach issue

Just installed 2 -75 watt Renogy panels and noticed today that my tachometer stopped working after motoring for a while. I think I need to turn off the panels charging when motoring but have no idea on how to do this?
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Old 17-05-2021, 16:43   #2
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Re: Solar and Tach issue

Or turn on a load.....or just ignore the tach
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Old 17-05-2021, 17:01   #3
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Re: Solar and Tach issue

The tach is most likely driven by the alternator on the engine. If the solar has got the batteries to the full point and it keeping the voltage above the alternator regulator's setpoint then the alternator will stop putting out power and the tach will stop reading (or read erratically).

As Sailmonkey says, you can turn on a load to pull down the voltage. Or ignore the tach, do you change throttle much once running? Or simply disconnect the solar (either on the panel side or on the battery side of any controller).
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Old 18-05-2021, 00:39   #4
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Re: Solar and Tach issue

Turn a few lights on.

Or set the solar voltage slightly below the alt voltage.
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Old 18-05-2021, 04:58   #5
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Re: Solar and Tach issue

Ok thanks for the response. I'll add a switch, since I might need to shut the panels off in the future also.
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Old 18-05-2021, 11:21   #6
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Re: Solar and Tach issue

Quote:
Originally Posted by bmm32005 View Post
Ok thanks for the response. I'll add a switch, since I might need to shut the panels off in the future also.

+1 on the switch. That’s what I did on my setup.
I find that i use it a lot.

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Old 18-05-2021, 16:48   #7
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Re: Solar and Tach issue

be carefull what you shut off. the controllers probably don't want to be shut off from the battery. probably best to shut off between panel and controller. check the manuals.

I would relay it with the ignition then otherwise you'll forget to turn it back on.
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Old 19-05-2021, 03:51   #8
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Re: Solar and Tach issue

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Originally Posted by Dsanduril View Post

As Sailmonkey says, you can turn on a load to pull down the voltage. Or ignore the tach, do you change throttle much once running? Or simply disconnect the solar (either on the panel side or on the battery side of any controller).


I wouldn’t discounted the controller from the battery, that’s akin to disconnecting the alternator from the battery.

If anything is getting disconnected, a switch between the panels and the controller is the way to go.
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