Load Readings

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Load Readings

Postby FutureEnergy on Wed Sep 13, 2017 6:05 am

Can some one explain why on a day that there was no standby generator running in an Off grid system the load bar gives a total of 21 kWhrs for the day but the shunt from the battery reads 33 kWhrs for the day. I am sure the inverters are not that inefficient! I would have thought these two readings should have been the same (within the limits of efficiencies) The battery shunt agrees with the generation shunts from solar and wind. Can anyone advise on this please?
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Re: Load Readings

Postby JRHill on Wed Sep 13, 2017 10:03 am

As an example only, if you were to shut off the breaker to the batteries so the comparison was strictly watts in to the OB components and watts out from the inverter you would see that the OB stuff is quite efficient, assuming that wire, connections, etc are all in order.

What you are gritting your teeth over is the inefficiencies in charging a battery bank, the gradual loss while stored and then the loss during discharge and to usable energy. You already know what environmental impacts are on battery performance. All you can do to improve this is to maintain battery condition and operating environment. The rest is just physics/chemistry.

I may have over simplified but this is how I have reasoned through the same observation.

Best,
Jim
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Re: Load Readings

Postby FutureEnergy on Wed Sep 13, 2017 11:32 am

Thanks Jim although I do not think this is the case. The from battery shunt is actually between the DC bus and the inverter. Any inefficiencies in the battery would show up as a difference between the amount of charge and the from battery. Between the shunt to the inverter (which because there was no AC charging of the batteries was only measuring in one direction) and the output of the inverter (Load) there should only be the inefficiency of the inverter. This is currently working at only 60% efficiency and I would expect well into the 90s for the inverters. Any further comments? - Have I got something wrong here?
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