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dhays asked

Smart Solar MPPT 100/30 not using VE Network voltage from Smart Solar Battery sense voltage

I have a Smart Solar MPPT 100/30 controller that charges a nominal 780ah battery bank. The bank has a Smart Solar Sense battery sensor connected to it. A Bluetooth VE Network was setup from the controller and the battery sensor was added to it. Both can see the other on the network and the Smart Battery Sense shows that is is supplying battery voltage and temperature data to the network, and the MPPT controller says that it is receiving the same data from the network.

However, the battery voltage that appears on the controller is much higher than that which is being given from the battery sensor. I can understand if the controller is displaying the voltage at the battery-out terminal of the controller, since the controller is 30' from the battery bank. However, the behavior of the charging output seems to be based on the controller's battery voltage display instead of the battery voltage given by the sensor.

It looks as if the controller is going to absorb charging before the battery actually reaches the absorb voltage as programed into the controller.

MPPT SmartSolarSmart Battery SenseVE.Smart Network
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klim8skeptic answered ·

@Dhays the controller is 30' from the battery bank

Why??

That length of cable is going to introduce a large voltage drop.

A large enough voltage drop as monitored by both the mppt and SBS will cause the mppt to default to the voltage reading at the mppt battery terminals.

Move the Mppt closer to the battery and SBS (and BT range).

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dhays avatar image dhays commented ·
Doesn't that kind of negate having a Bluetooth remote sensor? If I was able to practically move the MPPT closer to the batteries I would have done so.


So you are saying that if the if the voltage reading between the MPPT and the battery sensor are different then the MPPT ignores the sensor voltage? How much voltage difference the two before the MPPT reverts to its local reading instead of the sensor's voltage? I don't recall reading about this in the installation instructions.

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klim8skeptic avatar image klim8skeptic ♦ dhays commented ·

@Dhays So you are saying that if the if the voltage reading between the MPPT and the battery sensor are different then the MPPT ignores the sensor voltage?

Thinkaboutit. A 1v drop @ 30a = 30watts of heat. That's potentially bad if that is in 1 spot. (bad connection / fuse / etc)

How much voltage difference the two before the MPPT reverts to its local reading instead of the sensor's voltage?

1v, I think.

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dhays avatar image dhays klim8skeptic ♦ commented ·
Thank you. I guess I can understand the potential issues with a large voltage drop due to a poor connection resulting in the controller kicking out more amps.


The voltage difference I was seeing between the the controller and the battery as the controller was sending 14amps was .36v. The controller was showing 13.64v and the battery sensor was showing 13.28v. So this would be well under a 1v delta between the two.

I think when I get back to the boat, I will sit down and review the last two weeks of charge cycles. Currently I have no shore power at my slip so the shore power charger isn't in the picture and the only charge source is the solar panel. I will be looking to see what the voltage is at the battery when the controller moves from bulk to absorb.

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