BMV 700H as current and voltage transducer for PV

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per-erik asked Mar 17, '19

BMV 700H as current and voltage transducer for PV

We are trying to use a BMV 700H as current and voltage transducer for a PV system directly powering air conditioners, i.e. in a system without batteries. Someone told me that would work together with a CCGX for remote monitoring of that system, which sounded feasible. But for some reason, the BMV does not power up and do not provide any signals. Is there a fundamental difference between connecting them to a battery system and a direct PV system respectively?

The PV array is a series connected array with 8 pcs 275W panels connected in series, delivering a voltage in the range of 240-275VDC and a maximum current in this application of approximately 4-5ADC.

BMV Battery Monitor dc system

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Answer 1 · 2019-03-17T06:47:59Z

Paul B answered · Mar 17, 2019 at 06:47 AM

presuming that the air con inverters are always connected. so maybe try putting a rectifier bank coming off the incoming PV maybe there is a large AC feeding back from the Air con inverter units.

Total guess here

Have you tried with completely O/C panels nothing else but the BMV connected and does it work

and are you sure its a BMV700H unit

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per-erik commented · Mar 17, 2019 at 07:06 AM

Thx Paul. Maybe you've hit a point there. The is actually some back-feed from the air conditioner (but only from one out of three I think). The aircons are hybrids that can be fed both with DC directly from the PV panels and AC from grid - in this case a generator grid. And I did note the back-feed on the one that is connected also ro generator power. However, the two other aircons are only connected to PV so it shouldn't be the case there, I think.

With O/C panels - do you mean not connecting the aircon? (sorry that I'm very much of an expert....)

Finally, yes I'm sure they are 700H - although I'm remotely guiding our electrician in Haiti now and can't double check myself.

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Paul B per-erik commented · Mar 17, 2019 at 07:15 AM

yes with NOTHING ELSE BUT the BMV connected to the panels. (for test only)

If it works then you have a issue with feedback, just put a rectifier across the PV leads and then conect the + and - to the BMV yes you may loose 1 volt of accuracy due top some Volt drop across the Rectifier diodes but for what you are doing I think thats a NON issue.

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per-erik Paul B commented · Mar 17, 2019 at 07:30 AM

Great - will instruct to test that on Monday

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per-erik Paul B commented · Mar 17, 2019 at 08:02 PM

Turned out to be very simple. They checked the fuses today…. Sorry that I posted the question before checking better.

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