chris-brown avatar image
chris-brown asked

Smart battery monitor under voltage

I recently installed the Bluetooth battery monitor in my travel trailer that is using two 100 ah lead acid batteries. I’ve found the aH counting to be fairly accurate but for some reason the voltage shown on the monitor and app are much lower than true voltage. The victron solar charger I have shows the correct 13.8-14.2v when plugged in and charged but the battery monitor shows 11.04 this morning and down to 9v during the same timing as checking the solar charger. Any ideas how to remedy? I’ve replaced the fuse with a new waterproof fuse holder

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1 Answer
wkirby avatar image
wkirby answered ·

All what you describe points to a shady connection between the battery positive and the shunt. Are you sure your connections are all sound?
Check your wiring to the fuse holder and check that the fuse is making good contact within.
What current rating of fuse did you fit in your new fuse holder?
Also worth checking that the grey cable between the shunt and the BMV is connected well.

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I've tried a couple different sized fuses, they're making good contact (brand new waterproof Blue Sea blade fuse holder) and I'm currently using a 10amp to see if there was resistance in the fuse, but no changes yet. I wonder if removing the positive (red) wire from the shunt and reinserting, there could have developed some corrosion? I've reconnected the grey cable on reconnecting on both ends, no change. The monitor worked properly when first installed back in the fall, but now it is showing low voltage, which leads me to think it could be corrosion.
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Probably is corrosion. A fuse won't cause any significant voltage drop, there's not enough current. Bad connections will.
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chris-brown avatar image chris-brown kevgermany ♦♦ ·
Thanks, I'm going to try to remove the small red wire post from the shunt and clean it and then reinstall.
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