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Hi,
Customer chose to have 2x 100ah Lithium Batteries with built-in BMS (Not Victron Units) to be installed alongside his Victron Multi-Plus 12-2000/80. When initially powering up, the Lithium's simply keep shutting down even without a sizable draw, is there a setting that needs to be altered on the Mutli-plus to give a softer start, or should I be going back to the client saying that his Lithium Batteries have faulty BMS's.
That’s not quite enough info to be able to pinpoint the problem. We need to ensure that the batteries are charged, and when powering up, do it with no loads connected to the AC out. Have you changed the charging set points yet, and also the inverter battery low shutdown parameters?
its not necessarily faulty BMS, it could be a system integration issue - sounds very similar to another recent thread:
Ignore the content about undersizing at the end of the thread since you've got 2x 100AH already, but the content around precharge, and the failure symptoms, might be useful for you.
ok, plot thickens!!
Installation Specs:
Batteries were fully charged before install and Motorhome 3 days on EHU (including 8 hours drive time) before coming "Off Grid" and noticing problems. Multi-plus programmed to LiFePO4 profile and specs of Batteries, DC-DC charger with LiFePO4 also installed and BMV at 100%.
Connecting batteries with a 60a load individually to the Multi-Plus and both work fine. Connect both to Parallel and increase the load using a Hair Dryer (drawing 120A), still no issues there. Using a Baby Bottle Warmer/Prep Machine (950W) or use the Microwave (1312w) and the Multi-Plus goes to low battery and then all 12v lost as the BMS in the batteries have engaged.
50mm single or dual cables? How long of a run? I have had issues with undersized cables on some installs. On paper it penciled out, but had issues tripping BMS. I then oversized the cables and it solved the problem.
Have you tried both batteries in parallel with the a smaller load? I would try to nail it down to a specific amp load that trips the BMS. Start small and increase till it pops.
Some clarification questions to make sure we're on the same page -
1) there is no problem starting up with zero load?
2) there is no manual on/off switch on the DC line between battery and multiplus?
3) hairdryer at 120A DC = 1.5-1.6 kW (accounting for inefficiency etc) does not trip the batteries
4) bottle warmer at 950W causes both BMS cut out when switched on at AC socket?
5) microwave at 1312W causes both BMS cut out when switched on at AC socket?
6) the batteries connected in parallel can support 200A draw - can you verify that directly with some testing?
7) when the multiplus shows low battery, is there a delay between that and the BMS cutting out, or does it happen pretty much at the same time?
I've got a couple of theories right now
1) surge/startup power of the bottle warmer/microwave exceeds the aggregate 200A DC continuous limit. In this case you'd be running pretty close to the MP limit as well. Do you have a AC clamp meter w/ an inrush measurement function? Use that with the loads in question at a workshop wall socket to check out the actual peak demand.
2) the wiring of the batteries caused uneven loading across the bank. The battery that handled the bulk of the load tripped, causing the other battery to take all the load, which then caused that one to trip. A DC clamp meter could be used to identify this scenario.
Did you ever find a solution? I am experiencing a similar issue.
Do you happen to have a battery switch in between the battery and the inverter?
trick can be to first start the inverter on AC input power, so the DC bus gets charged.
Yes, and I have been using my generator to get the system started. Also hoping that my solar might also be able to get it going but waiting for better weather to test that. Ultimately, I'm hoping to find a solution that doesn't require the Gen or solar. Thanks for the reply.
I am trying to find detailed info on how to make a precharge device using wire, switch, and a resistor. Haven't yes found the details and its some that is above my skill level without assistance.
Best to ask an electrician to help you with that (so it is sized properly)
But basically it's just a momentary switch with a big (say 10 Ohm / 100W) resistor in series with it. and this you connect in parallel with the battery switch.
