Author Topic: Enphase 5p Battery specs - What is AC round-trip and DC round-trip efficiency?  (Read 6912 times)

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Offline DougSpindlerTopic starter

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Just purchased and installed an Enphase 5p battery.  Could someone please explain what is meant by

AC round-trip efficiency 90%  (AC to the battery to AC at 50% power rating) 
DC round-trip efficiency 96%

The 5p only has AC terminals for charging and load so not sure why they list DC efficiency. (There is no way to DC charge.)

I'm guessing the RT AC efficiency means if 1kWhr is used to charge the battery I will only get 900 Whrs back when discharging.  (Provided the discharge load on the batteries is at 50% of the continuous capacity load 3.84 kWhr.)

Thanks

https://enphase.com/download/iq-battery-5p-data-sheet
 

Offline Siwastaja

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Yes, you got it right.

Quote
not sure why they list DC efficiency.
Just to offer more detailed information for those interested. Indeed it's not very relevant for end user if the only use case is through the AC inverter-charger. Battery chemistry and voltage ranges is similar extra information; just for reference.
 
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Offline DougSpindlerTopic starter

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Yes, you got it right.


Thank you so much.  I've learned a lot from the people in this forum.

So if my calculations are correct, Enphase configured the batteries to provide 8 amps during "normal" discharge cycle.
3,840Whrs / 240v =  16Ahrs.
Applying the 50% setting 8 amps per hr at 240 volt.  Or 16 amps at 120 volts.

It's a 5kWhr battery with a 15% reserve leaving 4,250Whrs useable. (Assume new battery, no degradation.)

So if I had a 1,500 watt 120 volt resistive heater, (assuming 100% duty cycle) current draw would be 12.5a.
Runtime (assuming 100% draw from the batteries and no additional heat loss from the higher current) would be 4,250/1500 = 2.83 hours.

Are my calculations correct? 






 

Offline 5U4GB

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Another thing you're going to run into is tare loss, which is the cost of keeping the electronics running.  There's a good Enphase-specific thread that covers this.
 

Offline DougSpindlerTopic starter

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Thanks for sharing. 

Still collecting data and trying to understand how to read Enphase’s software but I have noticed the batteries are periodically during the day drawing 100W.

I have the newer 5p battery and and trying to figure out how to get the parasitic loss from the batteries.

 

Offline 5U4GB

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The 100W figure sounds like the tare loss.  I've got 5Ps as well and that's the figure for the inverters and other electronics surrounding them.
 

Offline DougSpindlerTopic starter

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Would you please explain what tare loss is.
 

Offline 5U4GB

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Would you please explain what tare loss is.

See the link in this post, that explains it pretty well.
 
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Offline DougSpindlerTopic starter

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Thank you
 

Offline DougSpindlerTopic starter

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tare loss appears to be the same as a parasitic loss.
 


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