Mppt 150/70 grounding issue

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gunnadoo asked Nov 1, '18

Mppt 150/70 grounding issue

I have an mppt 150/70 connected with bmv700 , Phoenix 24/12 converter and Phoenix multiplus 24/3000 Recently had cable melting issues on the 12v side and rewired everything.

All 12v accessories ground to the Orion Not the chassis

The 24v house battery bank is also not grounded to the chassis . If I connect the 12v or the 24v black wire to the chassis it goes up to 17v and wires get warm And the Mppt 150/70 reads 0v on the Pv side if I keep the 12or 24v floating (not grounded to chassis all is ok and the POV voltage shows again charges etc

I have a smaller mppt on the 24v starter batteries which also has a 24/12v converter for audio system but these appear to be fine and have no influence even though they are grounded to the chassis of the bus.

It seems that only the mppt 150/70 has issues and therefore anything 12v inside the bus cannot use a earth to chassis anymore hence the rewiring.

Although it all appears to work properly now it has me scratching my head any thoughts?

John

MPPT Controllers

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gunnadoo commented · Nov 02, 2018 at 03:25 AM

Addendum : When I disconnect the charging side of the mppt I can ground 12 and 24v to chassis with no problems. It’s when I reconnect the mppt to batteries it introduces an extra 5 v causing issues and PV output shows 0v so I think there’s an issue with the mppt which is my main concern the current workaround is ok but it’s what the mppt does

That’s the issue

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markus answered · Nov 02, 2018 at 08:58 AM

It sounds a bit like there is a short circuit between the pv connection and the chassis.

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gunnadoo commented · Nov 02, 2018 at 09:03 AM

Exactly that’s what I’m trying to work out as I have eliminated everything else by recabling everything using floating ground method

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markus ♦♦ gunnadoo commented · Nov 02, 2018 at 09:05 AM

Do the problems stay the same when you disconnect the panels connection from the MPPT?

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gunnadoo markus ♦♦ commented · Nov 03, 2018 at 12:32 AM

Doing my head in when I check volts Orion pos 12v out to chassis it shows -16.4 when I disconnect charger side of Pv shows 13.2v

Disconnected panels 1 by one until no panels connected and the mppt stay on showing 25.2v on batt side BUT Pv display shows 23.3v with no panels and theBMV shows a 4 v charging

Must be a faulty mppt ? Thinking of using my 75/15 to connect 1 x 24v 195w panel to see what happens as I just need a maintenance charge at present when I travel I only use 45ah/day hope someone from VICTRON sees all this

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gunnadoo gunnadoo commented · Nov 03, 2018 at 02:12 AM

I connected the mppt 75/15 to 1 panel and it’s currently charging about 3 amps BUT checking voltage from Orion 12 out to chassis it still shows - 16.5v even after disconnecting all 12v links so I will disconnect multiplus and check again then start from scratch as far as I can see the Orion and multiplus and shunt are all connected correctly as it all works this is just getting weirder

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gunnadoo gunnadoo commented · Nov 03, 2018 at 02:27 AM

Trial by elimination disconnected pos and neg on starter batteries no change still shows as minus 16.5 v maybe it’s the Orion if I try to add a chassis earth it gives huge sparks

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gunnadoo answered · Nov 03, 2018 at 05:01 AM

Confirmed everything reconnected and all works as intended amazing one missing ground lead caused over 30hrs of rewiring and testing etc . At least I now know where everything goes and what it does and I have added extra fuses and breakers along the way

VICTRON is still king of the hill in my books

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Answer 1 · 2018-11-02T02:16:21Z

markus answered · Nov 02, 2018 at 02:16 AM

Hi,

to help you in this matter, I think you have to provide more accurate information on what exactly you would like to connect.

Maybe you can make a drawing of your installation.

As I read this, I hope you use good and quick fuses.

Markus

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gunnadoo commented · Nov 02, 2018 at 03:27 AM

I’ll do a drawing as well pls see my additional note

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Answer 2 · 2018-11-02T08:11:26Z

markus answered · Nov 02, 2018 at 08:11 AM

There are 2 versions of the Orion converters. Isolated one and non-isolated one.

The non-isolated one share the same minus.

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gunnadoo commented · Nov 02, 2018 at 08:49 AM

Correct I have non isolated one

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Answer 3 · 2018-11-03T03:03:06Z

gunnadoo answered · Nov 03, 2018 at 03:03 AM

Problem solved ??? I isolated a pv so the frame did not contact the chassis no change still -16.5v

I then connected another earth (black) lead from the Orion’s common shared earth terminal to the chassis and all is ok showing 13.2v now instead of -16.5 the mppt 75/15 is still charging so I’ll reconnect all the panels to the mppt 150/70 go figure.....

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