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Old 10-17-2019, 07:48 PM   #1
Join Date: May 2017
Posts: 44
Question Battery Monitor Kit Questions

My rig was prewired for solar by SMB and is equipped with a 2000 W Magnum system with remote and the Zamp 30A solar controller.

After the advice that I received in this thread
I purchased the Magnum BMK and had SMB install it.

I've had it a week and have been checking the readings as we drove back home to learn what the BMK is telling me. I have noticed that when the engine is running, there is clearly charging going on, but the BMK doesn't indicate a +A number to show how many amps are going in to the battery. Today I connected it up to our solar panels for a first test and had the same result. Charging was clearly happening, but the meter showed a steady -0.2A (the 12V system was turned off).

My expectation from the Magnum manual is that I should be able to see the amount of amps going in or out in real time, as well as a net +/- reading.

SOC seems to be working okay, and I think things are working correctly when plugged in to a/c, but I'm wondering about these "onboard" charging systems. I've attached a photo of the displays when the solar panels were connected. showed that others had run into bad BMK systems as well as incorrect wiring. I've looked at the wiring and I think it is correct, but it's a real bowl of spaghetti under my bench seat so it's hard to tell. Before I go digging too much, I want to make sure I'm understanding what I should be seeing.
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Old 10-17-2019, 11:06 PM   #2
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Join Date: May 2007
Location: Beaverton, OR
Posts: 1,521
Have you checked that shunt is between the battery and all the charging sources, The current has to go through shunt to be read. If it is on the wrong side of the shunt it won't be seen.

Do you see positive amps when you are charging with the Magnum charger?

Note: In the above diagram all the paths from battery to charge source have to go through shunt.


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Old 10-18-2019, 12:43 PM   #3
Join Date: May 2017
Posts: 44
Hey Greg -

That diagram is incredibly helpful! I'll be double checking everything when I get back from a weekend away.

Yes, I see positive amps when plugged into "shore power" and charging from the Magnum. When I'm charging from the engine, I see -0.2 amps.

I suspect that both the feed from the alternator and the solar controller are on the wrong side of the shunt. Your diagram will help me trace that down. I'll update when I've checked.
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