Emon II H1--Ghost Current

[Mark Fox]

We have the Emon II H1 that was installed in 2005 on our 38’ sailboat. We purchased the unit directly from Ample Power in Seattle. The serial # is 10584 8.3. We’ve sailed almost 20,000 miles since the install and it's worked wonderfully.
We are in the South Pacific and the problem is that a couple of nights ago, it suddenly started showing a high rate of amp hours being consumed, fluctuating between 25 to 50 amps when we think there is no actual draw. There could be some small amp draw from an unknown source but it can't be what Emon is reporting. The battery voltage, as monitored by Emon, our inverter, and the multimeter, is 12.7-13.3 depending on the time of day. When we run the generator, the battery voltage comes up as it should but the amp hours being consumed are still off by 25-50. The solar relay is working and the battery voltage increases as it should during the day. If we really did have such a large draw on the batteries, they would be completely dead by now.
We have disconnected all three house batteries and the start battery and load tested each, watching the voltage. We applied a small load of about 7 amps for a few minutes and all appeared to operate normally. No one battery acted different than another (start battery is smaller so voltage dropped a little faster but that was to be expected). Our multimeter will only read a current of 400 mA and so I can’t check across the negative shut, where Emon’s sensing wires are connected, to see what that independent reading is but again, there is no way we are using 25-50 amps each hour based on the voltage of the batteries.
We have checked all connections, everything on the boat seems to be working fine, and we’re not sure what to try next. Is it possible that something has gone wrong in the unit itself? Any ideas?

[Coulomb]

Testing for zero current is done by connecting both small shunt wires under one of the small shunt screws. The Emon should read zero or perhaps 1 digit.

[Mark Fox]

When I disconnected both wires at the shunt, Emon reads 0 amp hours being consumed, when I put both connectors under one screw, it gives the same 25-50 amp hours being consumed reading. Does this mean there is something wrong with the unit itself?

[Coulomb]

It could be in the unit, but first verify that both dgnd and refgnd are well connected. It could be that one of them is broken or corroded.

Sometimes when new batteries are installed, the shunt gets bypassed/mis-wired, so check this if applicable.

[Mark Fox]

No new batteries have been installed since we left Seattle 4 years ago and no wiring has been changed so I don't think that's what we're dealing with. I think what you suggested I check (dgnd and refgnd) were the grounds for Emon. They look fine, not broken and no corrosion. I've looked at all the connections from Emon through the whole system and can't see or feel that anything is lose or corroded. Anything additional suggestions?

[Coulomb]

It sounds like something internal.

If you send the unit in for repair, DO NOT remove the two external terminal blocks that were shipped with the unit.

Send products for repair to:

Ample Power Company, LLC.
6315 Seaview Avenue, NW
Seattle, WA 98107

[Mark Fox]

We have arrived in New Zealand and will be bringing the Emon back with us to Seattle around the first of the year for you to look at. Question, we need to have the solar panels charge the batteries while we are in the states (7 months +/-) and currently that is done through the Ample Power solar controller and Emon. If we pull Emon out, can we still use the controller for the solar panels or do we need to put in another controller until we can reinstall Emon?

Thanks,
Mark

[Coulomb]

You will need a separate controller.