MPII issues.. 4ga replaced with 2ot.. now not using solar. using invert mode turns off the MP.

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brucesterj asked Mar 16, '24

MPII issues.. 4ga replaced with 2ot.. now not using solar. using invert mode turns off the MP.

Help..! My solar electrician (14 yrs exp.) came out here yesterday and connected some 1ot wire replacing the 4ga. It's a 26' run from the MPII to the batteries up on the tongue. It was working, but had one problem upon startup.. when I had this pc set in the bios to restart when it detects AC power would cause too much surge and would turn off. I'm a OTR trucker and need it to restart. So after replacing the cable, I turned on the MPII and things were back to normal, but we didn't check it on the inverter mode. This was only an upgrade and nothing else was done.

So now the new issue is.. When I restart it.. the DC voltage goes up to 16.50. The four 12v BB lithiums are full. What could be causing the problem..?

Multiplus-II

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Alexandra ♦ commented · Mar 17 at 07:36 AM

@Brucesterj

It is very possible that the BMS on the batteries has shut down.

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brucesterj Alexandra ♦ commented · Mar 17 at 04:31 PM

Interesting. If they did, don't they auto reset..? I'll get out there with my battery load tester, I don't know what else to do. They look ok on the vrm. So I removed the cover on the lynx dist. I set my multimeter to check dc volts and they were the same as the display there on the bmv 712, BUT.. as the MPII is in the ON mode.. just touching the end of the pos and neg studs TRIGGERED the MP to restart. I pulled the cover to verify the fuses weren't blown, visually but can't see them. I tried making one of them jumper cords for this but realized the phone jack plug is too big. I think it's an RJ11 not RJ32 needed. Don't know where the factory cable that came with it went to. I do have more of them 12v to 5v converters but would rather just buy a ready made one. So... Could a fuse be blown..?

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brucesterj answered · Mar 18 at 08:45 PM

After talking with the victron dealer and my electrician.. I'm going to get a 48v 3000 MPII and will rewire my 4 BB lithiums from 12v to 48v and the 1 ot will stay. I don't have\use any real big loads in here.. and with the 4ga, it WAS working. PC, microwave, air fryer\hot plate and a mini split.

case closed. Thanx to those who replied.

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brucesterj answered · Mar 18 at 11:36 PM

DAMN IT..! I posted and now it's not here. Ugghh.. I said something like this:: After talking with the Inverters-R-Us dealer and my electrician, I'm going to switch to a 48v MPII. I should get a good price on this one from them. Will have to add some kind of stepdown converter to 12 for the exterior marker, tails and brake lights.. I think. So.. With the PC and mining software running.. I'm only pulling 589w.

That's my Drone shot over a local lake..

PS. Thanx to those who replied.. :)

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Answer 1 · 2024-03-17T17:29:33Z

brucesterj answered · Mar 17 at 05:29 PM

More troubleshooting. So while watching the VRM, I turned off both controllers.. and watched the voltage on the vrm slowly drop to normal 13.?? volts.. then turned on just one of the controllers and saw the voltage going back up. Is this normal..? did this test on each controller. Same results.

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Answer 2 · 2024-03-17T21:13:44Z

elvis answered · Mar 17 at 09:13 PM

@Brucesterj

If you correct the title of this post and briefly state your problem, you have a better chance at getting a quality reply

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brucesterj commented · Mar 17 at 09:20 PM

Changed. now wish me luck.. lol..

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Answer 3 · 2024-03-18T01:18:25Z

Chad Heiser answered · Mar 18 at 01:18 AM

I am still unclear as to how your MPII is wired. The MPII (with a 12 volt battery bank) needs two sets of 2/0 AWG wire at a minimum (that's four wires total, 2 positive and 2 negative). Most people run a single set of 4/0 AWG wire rather than two sets of 2/0 AWG. A 26 foot run from the batteries to the MP is going to result in some serious voltage drop on a 12 volt system even with the large cables. This means you need to add even more cable between the batteries and the MP. With that distance, I would be running two sets of 4/0 AWG cable. Even that could struggle to hold voltage under heavy inverter loads. Your solar electrician should know this, but anybody can plug in some basic numbers into a voltage drop calculator and see you are severely underwired for the distance between your batteries and MPII.

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