BMV 712 shunt not reading Alternator Amps

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robbieda123 asked Aug 7, '21

BMV 712 shunt not reading Alternator Amps

obHello,

i have been reading this site for quite awhile and seeing if anyone has had similar issues as me, however none are exactly the same so here's my My 1st post. thanks in advance.

I have been running 2 100amp DSC-Lithium batteries under bonnet, (please spare me from under bonnet lithium advice) linked in paralel. Both batteries earthed to chassis.Shunt, BP220, 2000w inverter, various camping equipment, all fused. 53m2 cable between batteries and to shunt and BP.

The entire system was running fantastically for 2.5 years with no issues other than me killing alternators driving through rivers and creeks and mud, so driver inflicted issue, i know....position of standard alternator is simply stupid, hower, i digress.

To fix the alternator killing issue i have installed a water cooled sealed Alternator. it is a 200amp rated unit, which charges the lithiums at 130 to 140 amps at idle which suits the need perfectly. they can charge at up to the rated 200amps with no issue.

From the moment i fitted the sealed alternator my BMV712 no longer measures amps. It refuses to read accurate in or out AMPs. I have tried calabating it, have tried re setting it but no.

The batteries have a bluetooth connected app that allows one to view the battery cells, balancing, amps and amps in and out in real time. So i am taking the battery readings as accurate, as they matched the victron within a couple of .01 of an amp. also if the BVM was correct I'd have 2 very dead batteries, by now, which i do not.alternator in the car now for 4 months and I'm till chasing the issue.

What can cause this, purely from the changing of the alternator? with the 500amp shunt it cant be too much for the shunt itself so i'm at a loss. Any help appreciated.

Cheers

Rob.

BMV Battery Monitor

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Paul B answered · Aug 07, 2021 at 07:49 AM

More than likely you have installed the shunt incorrectly or when you fitted the alternator you put the alternators negative wire directly to the battery and not to the load side of the shunt.,

Only ONE negative wire between the shunt and the BATTERY all others MUST go to the load site of the shunt inc the alternator negative . If this is not the case then please attach a wiring diagram and some installation pictures.

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Paul B answered · Aug 08, 2021 at 02:32 AM

cant suggest any more sugest you send a photo of the shunt installed and the battery so we can see the connections

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Paul B answered · Aug 08, 2021 at 05:37 AM

The shunt is NOT installed correctly, as I said before there is ONLY one wire thats conceded to the negative of the battery then to the shunt. no earths to be connected to the neg of the battery AT ALL only to the load side of the shunt and this includes the inverter Neg this must also go to the load side of the shunt as well

Original Diagram removed and changed to this diagram

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Paul B commented · Aug 08, 2021 at 06:20 AM

As another comment to your drawing and posiable system issues - you seem to have a Victron BP220 unit installed THESE ARE not bi-directional units they are fine for loads only or charge only but they cannot do both in the one circuit or they maybe damaged. and as this is a lithium battery and they are 2 x 100amp with internal BMS and a max allowed charge of 100 amps each - so a alternator running at 200 amps plus the solar will exceed these settings - and as I suspect that they will not be able to take the new alternators full charge power plus the solar and thus the batteries internal bms systems will turn the batteries off and this could give you a open circuited alternator and thus damage the alternator or do major damage to your electrical systems with high voltage spikes.

you really need to get this system professionally looked at before you do major damage.

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Answer 1 · 2021-08-07T09:39:43Z

robbieda123 answered · Aug 07, 2021 at 09:39 AM

Hey Paul,

Thanks for that. i believe shunt is wired in correctly as was working before. The new alternator does not have an negative wire. When i queried this with the manufacturer of the alternator, i was told that they are internally grounded and don't need or have a cable to connect it to the shunt / battery neg. this was what i thought the issue was initially.

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Answer 2 · 2021-08-08T03:37:20Z

robbieda123 answered · Aug 08, 2021 at 03:37 AM

Thanks again,

pictures probably wont make a lot of sense, hopefully this drawing will.

wire-diagram.jpg (657.8 KiB)

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Answer 3 · 2021-08-08T06:55:04Z

robbieda123 answered · Aug 08, 2021 at 06:55 AM

ok, Thanks Paul. will swap some cables around and report back. Much appreciated.

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Answer 4 · 2021-08-08T08:35:03Z

Paul B answered · Aug 08, 2021 at 08:35 AM

I changed my diagram as I misinterpreted one of you wiring connections

1628411693059.png (867.5 KiB)

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Answer 5 · 2021-08-08T09:34:16Z

robbieda123 answered · Aug 08, 2021 at 09:34 AM

Hey Paul,

managed to get the wires on the shunt changed over, have not removed battery earths yet....bloody dark. couple of photos of the gear im running.

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