OK - the max charge current on that Multipus is 120A @ 14.4V so the max charge wattage 1.7kW so a 2000W generator is not going to be any slower than your 4400W generator. The first thing I’d eliminate is the generator itself. Check that the AC voltage isn’t spiking up too high as the Multiplus will automatically start to taper current as part of it’s anti islanding protection. Check the generator with someone else who has a similar Victron system and see if it exhibits the same problems.
If the Multiplus were the problem then you would not be able to charge off shore power (ie a grid connection) - I don’t know if you’ve tested that?
If it is the battery BMS then you’d expect similar problems with your solar controller.
The only other thing I can think of is that the generator has a bonded neutral and the Multiplus when connected to shore/grid power has a switch which will flick the ground straight through from the AC supply. When there is no AC input it bonds neutral and ground internally via a relay. However, I’d expect more AC problems if there was a ground problem, like tripping breakers.
One easy test you could try is to disconnect the battery and see if the genny behaves normally when not trying to charge the battery - ie just supplying normal loads in the van via the Victron passthrough.
Hi, @Mondotv
@MHillger mentions in this post that he has tried shore power and changed generator and the results he got then: Generator Charging Surge - #15 by MHillger
Could you please disable your ‘Power Assist’ checkbox under the ‘Inverter’ tab to off (unchecked), then could you re-enable ‘Power Assist’ and set your ‘Power Assist’ → ‘Assist Current Boost Factor’ to 0.5, and then to 1.0. On each occasion of the change in setting, run your generator and report the results back here.
So 3 results, off, on(0.5) and on (1.0)
I see from your original post that it is set to 2.0 in the images provided.
Oh yes, I misread that as he connected the genny to the shore power input. It certainly narrows it down to either the Multiplus or the battery.
I went back and re-read the original post closely. You state “it appears” the battery voltage is spiking up to 16V which forces the BMS to shutdown charging causing the surging. It would be great if you could confirm this with a multimeter. If that is actually happening then the answer is simple. The battery should never reach 16Vdc. One thing I noticed from the screenshots is you haven’t enabled the Victron’s internal BMS. You should do this immediately as that protects the battery. It’s the last section on the General tab. People think it’s only if you have a Victron battery but that is incorrect. It’s for any battery. Victron explains why in this video at about 10:30 in
OK, I got back to working on my charging problems today. After setting for a week with the invertor off, Battery Voltage was 13.1 . I tried charging with the Power Assist box unchecked, then at .5 , then 1.0, then 1.5, the 2.0, 2.5. With charging rate at 18 amps, there was no difference in any setting. Both generators would surge and watts on my Victron BMV would bounce back and forth. The same on shore power…I went back to the Power assist on 2 the set the input charge current to 10 and walked it up 1 amp at a time. It charged steady up to 15 amps with battery voltage steady at 13.6v. Soon as I bumped it to 16amps, it started surging. Same on shore power…I will try to find someone with a lithium charger and see how the battery charges with it, although I dont know anybody that has one. I may have to buy one to find out…I did enable the Victron Battery Monitor on the General tab, thanks John Mitchell.
Hi @MHillger,
Thanks for getting back with that info, and I appreciate that may have been time consuming.
Given the results across the two generators and shore power, whilst not being able to totally rule out an issue with the MP, I think it is highly unlikely to be related to the MP.
I’m starting to come down on the side of the battery being the issue.
As has been hinted at by @owenb79, @Mondotv and myself, this could be related to the battery, and more specifically the battery BMS raising some kind of protection disconnect.
The fact the battery has no BT connectivity feature makes this hard to observe.
The most likely culprits:
Cell over voltage protection.
Charge over current protection.
Possibly an NTC sensor (temp sensor - over temperature in this case, but the least likely).
Next steps:
I would personally see if I could borrow a high output (>150A @ 13.8v) LiFePO4 battery charger.
This will enable you to rule out the MP completely. Charge with the battery disconnected from the electrical system. This would be a zero cost diagnostic (except the electricty cost).
Here in the UK, a battery retailer / wholesaler may well be prepared to charge / test it for a small charge, especially if you point out you only need to see if it disconnects above 135A.
Alternatively see if you could borrow a LiFePO4 to charge with your MP to see if the same happens at the surging threshold you identified. You’d only need to borrow it for as long as it takes to establish if the surging behaviour starts. If it does this would point to the MP being the issue. If not, we are back to the battery.
You could also see if someone were prepared to charge your battery with their system (above the surging threshold). See the previous paragraph above for the outcome indications.
If it’s the MP (my feeling is this is the least likely outcome), if still in warranty contact a distributor for next warranty steps. If it’s out of warranty, repair or replacement.
If it’s the battery, you can resolve yourself to only charge from the genny / shore at < 132A. Only generator charging would bother others (sound) and should only take <2.5hrs to recharge a totally flat battery (I’d probably choose this as the lowest cost option, using MP current limiting)
OR
Replace battery (LiFePO4 costs are falling all the time), get one with a BT BMS that has the ability to be fully configurable (normally if the manufacturer allows you to access settings they void any warranty though)
OR
Dismantle battery, test all cells, and replace cells / the BMS with a BT version (JKBMS maybe?) and remount into a new battery box, you’ll learn a lot about LiFePO4 (see @willprowse on youtube)
Do you have an original manual for the battery? Or know the BMS installed?
So, I depleted my battery to 12.5v and started charging from shore power at 10 amps. slowly increasing the charge current 1 amp at a time. I got up to 30 amps and I noticed the 12v LED lighting strips in the basement of my RV (where all my electrical equipment lives) flickered! The next time they flickered I saw on my voltmeter a spike. Not enough to stop the charging but just enough to make the charger back off for a split second. I played with it for several hours and the higher the charge voltage got the more I had to back off on the Charge Current…After calling around to all the RV dealers I just couldn’t find a stand alone Lipo charger I could use so I bought an AIMS 75 amp charger. Got it today and hooked it up. Same thing, voltage will spike…I believe now that I have an unbalanced cell in my battery. One of the cells may be hitting max volts causing the BMS to shut down that cell therefore causing the voltage to spike when all the voltage goes to the other 3 cells. I’m pretty dumb in these matters but have been watching lots of videos and a few on balancing unbalanced cells. I will cut open the battery and give it a shot…I don’t want to give up on the battery because I did a capacity test on the battery and it gave me 293 AH after being charged slowly to a resting voltage of 13.59v. It is rated at 300 AH but I suspect it may be a 280AH battery. This has been quit the science project and I suspect I’ll be buying new batteries and going to a 24v system.
..
Hi Mike,
That was a great update. Very methodical fault finding and info gathering. Great patience too. I’m confident you’ll be learning a lot at the same time too?
Could I ask / comment, that I’d like to see you charge the battery on it’s own (if you haven’t already), to rule out any other system issue, e.g an installed appliance, transient short being responsible for the issue (battery completely disconnected from everything else). Especially now you seem to have discovered how to emulate the problem. This would leave the battery 100% as the issue (and probably a faulty cell). On the up side it seems as if your Victron MP is off the hook!
Power Source → AIMS75 → Battery.
If you’ve been happy with your set-up to date, you could just add another 12v LiFePO4. Pricing on LiFePO is falling by the week. You’ll have a dual battery system (after any possible fix on the existing battery if required) then with a little redundancy and reduce your battery draw from a single battery, and increase you cycle count.
If you go the dismantling route, I’d do as previously suggested. Find the faulty cell(s) and replace, add BMS with BT (JKBMS?) put it all back in a nice battery box you purchase or make.
You could sell the AIMs to cover the new battery cost, OR be the go to guy for a battery test charger!!
Have you checked out @willprowse on Youtube for battery dis-mantling / building?
I will certainly charge the battery alone before opening it up, good idea. I watch Will Prowse all the time now! …I do have a question, If I get my current battery working (thinking about adding a cell active balancer if that is the problem) is it ok to add on another battery in series with new cells? I thought I had read somewhere that it wasn’t.
Stepping up to a 24V series bank, and combining a new and in-service battery is a judgement call really.
Why?:
In an ideal world you’d start with all like for like cells (batteries), you know the service history of all the cells ( to date), they have the same physical characteristics (internal resistance etc, etc).
A bit like the tyres on a car if you got a puncture (in an absolutely ideal world you’d change all 4, think Formula 1 (maybe for you NAS Car?)). But then there is reality. You’d change one, maybe the axle pair, and accept all the unlikely outcomes:
Oh it’ll affect surface adherence.
Changed vehicle characteristics.
and the list goes on, hopefully you get the point.
Everytime I drive a car (sometime different cars) I could crash and die. I weigh all the risks, mitigate as many as I can, and drive.
See how many people change an ENTIRE large series bank because a single battery fails, that would be madness, but your battery retailer would love it!
Ever heard a car main dealer tell you that ONLY genuine parts should ever be used (for some parts true, others not).
But you’d probably replace the battery with the same make/model.
The main hassle, would be that the individual batteries would most likely always need replacing at different times, out of sync, during the battery / bank service life meaning more offline time or hassle.
So, could you, Yes.
Would I, generally No.
Risk, Cost, Reward is what I always apply, YOU have to decide how they all balance.
Given you would be getting a new battery anyhow. Get 2 and series at that time, then when you replace in the future, do both, as they will be at the same service life point.
As for your current battery, I’d refurb’ and find another use for it (it’s a useful 300Ah one) or simply sell it on 2nd hand (I would NOT refurb it, just point out it probably has a cell charging issue), donate to a community project / friend.
Oh and I’d wait until I’d firmly established it’s the battery… lol.
OK, I have found the problem!..I opened up the battery case and removed the cells and set it on my bench. The battery looked good with no leakage or bulging and looked like a pretty well made battery. (I have watched all of Will Prowse’s tear down vids). Then I noticed some discoloration on the lug bolt of one of the cells!
Also a burned wire from the BMS attached to the same cell post.
Then I remembered something I did when I installed this battery several years ago! Laying on my belly in a pretzel position, reaching way back in the basement of my RV, blindly torquing the bolts down on my battery terminals, I short circuited the battery!!! The Lord was with me that day and the BMS only allowed a tiny spark and it killed the battery. I didnt think much of it that day but knowing what I know now about Lithium Batteries I was very lucky to be alive or at least not burning down my 5th wheel! When I turned on the shore power the battery woke up and I thought everything was ok but it wasn’t, in that split second that discolored terminal got hot and the white wire became disfunctional! Apparently, this would allow the multiplus to charge the battery but would cause the voltage to spike slightly. The MP Charger was probably surging all this time but I didnt notice it. The battery stayed close to 100% all the time anyway. Until I dry camped a couple times much later and noticed I couldn’t charge any faster than 200 watts without my generators starting to surge… I replaced the lugs on the cable and wire and hooked the charger up. I charged the battery all the way from 11.8v to 13.6 at 900 watts or 75 amps and the voltage never spiked once. I checked all four cells and all had 3.4 v. The terminals warmed a little touching with my fingers but didn’t get hot. I discharged the battery all the way down till the BMS shut it off then recharged again with no spikes or abnormal heating. Then I discharged it down again till the BMS shut it down. I reinstalled it in the case, sealed the case, and reinstalled it in my RV. I turned on the shore power and the battery woke up. I charged the battery with the MP at a rate of 1040 watts until the MP slowed down after 303 ah. During this time I swapped over to my 4400 watt and my 2000 watt generators and both ran perfect at 1040 watts, with no surging! I don’t plan on charging my battery near this fast as a general rule but I wanted to test it this time…I will cycle the battery a few times checking behaviors but I think I will use this battery as I always have without adding or modifying my setup for now. It has always been enough for us as the most demanding thing I use it for is my coffee pot in the mornings. I just wanted to be able to give it a boost with my generator on those cloudy days when my solar wont keep up. Thank you all for your help!