Aurimas Bukauskas avatar image
Aurimas Bukauskas asked

SmartSolar MPPT 100/20 Normal Voltage but No Current

Hi, would love some help debugging a recurring / intermittent problem with my SmartSolar MPPT 100/20.

Sometimes I get what looks like normal charging behavior (I have 2x 210 W panels wired in series, so around noon on sunny days I get 20 Amps out of the SmartSolar MPPT as expected).

I have two recurring problems, which may or may not be independent of one another:

1. Sometimes (more often than not for about 2 weeks now), I get normal voltage from the panels (~38 V), but apparently no current in or out of the MPPT. Sometimes I get very low current (about 0.1-0.2A). I would expect much more power from the panels, because this does happen when unshaded on sunny days near noon when I would normally expect close to 20 A or 280 W from the panels.

2. Sometimes (but not always) the battery voltage in the SmartSolar interface appears incorrect when compared to my BMV-712 (usually higher than the BMV, sometimes 14+ when the BMV shows 13-13.5), resulting in the incorrect charging state being selected (for example absorption when bulk would be appropriate). However, sometimes the battery voltage is identical to the BMV reading. Both devices are on a shared VE.Smart Network.

In these instances:

A multimeter voltage check across the battery terminals agrees with the BMV.

A multimeter voltage check across the battery-side wires into the SmartSolar shows fluctuating, and sometimes very high voltage, occasionally >16 V.

My specs:

- 100Ah Battleborn heated Lithium battery

- BMV 712 Smart Battery Monitor

- 100/20 Smart Solar MPPT

- Orion DC Smart Isolated 18 A

- 500 VA Phoenix Inverter

- 30 A Blue Smart Charger

- All connected using a Lynx Distributor, 40 A fuses for Smart Solar, Orion, Phoenix, (yes, I'm aware 40 A is a a bit oversized for the Smart Solar - would love to find MEGA fuses around 30 A).

Could this be a grounding issue? My ground cable from my Phoenix inverter doesn't fit onto the ground stud of the Lynx distributor, so I attached it to the negative / black outer terminal of the Lynx distributor, assuming that this is "close" enough to the ground of the Lynx distributor on the negative bus bar that this wouldn't cause any issues. Could this be causing voltage issues from the perspective of the Smart Solar?

Thanks a lot in advance for your help.

MPPT Controllersbattery chargingbattery system voltage
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1 Answer
Mike Dorsett avatar image
Mike Dorsett answered ·

from your multimeter readings, I would look for a cable fault (positive or negative) between the smart solar and the battery, including looking for loose or partially blown fuses. This may be a loose connection, fractured cable, loose crimp or similar. you can check to see which side it may be by measuring voltage from the smart solar battery connections to the same pole of the battery (+to+, - to -). This test should give consistently low readings - of the order of 10's of mV.

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