Amps reading out 100 amps too high in EMON II

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Amps reading out 100 amps too high in EMON II

Postby Kip Hansen on Thu May 27, 2010 12:32 pm

Dear Technical guys....

My EMON II is giving a reading on B1 AMPS, on my house battery bank, of "1 117.4A". Note, no minus sign. This seems unlikely that I am using this amount of power with only a very small refrigeration unit and one or two lights and various controls.

As I turn additional power usage on, it goes up the right amounts (a new light adds .3 amps, for example.) If I shut down everything, all the 12 VDC circuit breakers, turn off the inverter, etc, I can get it down to about 111.3.

In desperation, I have disconnected all positive cables from the batteries, one at a time, and all positive cables from the distribution bus (except the power to the EMON itself), one at a time, and nothing gets rid of the 'spurious' (I hope) 'extra' 100 amps of usage. I have also disconnected the 4 Winds wind generator, with the same 'non-result'. (I did the same with the connections to the starting batteries -- catamaran, so two batteries -- same non-result.)

When I put on the Gen Set and fire up the 90 amp charger, the Amps reading goes to 128-135 (no minus sign, of course).

Something is obviously wacky!

Is there any explanation other than "send it in?". For instance, could a bad shunt produce this behavior?
Kip Hansen
 
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Re: Amps reading out 100 amps too high in EMON II

Postby Coulomb on Thu May 27, 2010 4:05 pm

We've never seen a bad shunt except ones destroyed from shorted batteries.

Discharges read minus.

It sounds like something wrong with the sense wiring between the shunt and the Emon. Corrosion?
Coulomb
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Re: Amps reading out 100 amps too high in EMON II

Postby Kip Hansen on Fri May 28, 2010 6:25 am

Thanks for the fast reply.

I will replace the sensing wires in their entirety - new ring terminals, new marine-grade wire. It is only a two foot run.

Do I need to disconnect power to the unit before doing so?

Kip
Kip Hansen
 
Posts: 3
Joined: Thu May 27, 2010 9:20 am

Re: Amps reading out 100 amps too high in EMON II

Postby Kip Hansen on Fri May 28, 2010 7:01 am

The EMON II installation instructions call for

"twisted. shielded pair for the shunt sense wires. Terminate the shield lead at the shunt."

I take it to mean that the shield and one wire connect to one point on the shunt, and the other wire to the other terminal on the shunt. Is this correct? Does it matter which one?

If I can't find marine-grade twisted, shield pair, what should/could I use as a reasonable substitute?

Thanx,

Kip
Kip Hansen
 
Posts: 3
Joined: Thu May 27, 2010 9:20 am

Re: Amps reading out 100 amps too high in EMON II

Postby Coulomb on Fri May 28, 2010 2:27 pm

A run of 2 feet should be OK without shielding -- unless you have a ham/ssb radio nearby without a good antenna tuner.
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