Update (~2.5yrs) - 1100ah Xuba

[captNordy]

I wanted to post an update plus some questions. I purchased 1100ah from Xuba on July 20, 2020 after finding this forum and have been living with these batteries full time on our live aboard sailboat. Overall I have had ZERO issues with these batteries, have done ZERO maintenance and I'm very pleased considering their price point.

Brief overview of system:
BMS = REC-BMS
Charger = Victron MultiPlus being externally controlled by the REC-BMS (100% run from generator since we haven't stopped in a marina)
Alternator = Balmar 140amp with their programmable regulator
Solar = ~1000w with 5 MPPT Controllers

Brief overview of usage pattern:
We need to run our watermaker every 5 days, so initial system was designed so that we could live off of solar until the 5th day, then run generator to make water and top off batteries. This has worked in the dry/summer months, but in the winter and rainy seasons we can only go about 3-4 days before needing to charge. I typically charge when we get in the 35-45% remaining range, but I have gone down as low as 25% on occasion.

Observations/Questions:

1. One thing I've noticed is w/ the 140amp alternator, the REC-BMS cannot keep up with balancing, so the first pack always hits 3.6v while the others are in the 3.5v or 3.4v range.

1. When the packs were new, I could get to 14.2 at 100%. After year one, I was at ~13.8 and 96%, today I'm at ~13.6 and 92%. These voltages are hit by the Victron Multiplus charger (externally controlled by the REC-BMS), when it start to hit these voltages, it goes from putting in its normal amperage down to ~10ams/hr. Basically it seems to drop in to float (or is it absorbtion). When I shut down the generator, the solar panels will continue charging and can bring the final percent up a couple more (so from 92% to 94%).

Any guidance on what maintenance I can do to get these cells back up to 14.2 and 100%
Should I pull them all and do a top-balance?
Should I rebuild the packs to change up the cells since pack 1 has seen more 3.6v than the other cells?

I've added images of the individual voltage readings at each cell after one pack started hitting 3.6v as well as an image from the REC-BMS readout.

Thanks for any help and let me know if anyone has any questions about my setup or would like more info!

[CaptainRivet]

Originally Posted by captNordy

I wanted to post an update plus some questions. I purchased 1100ah from Xuba on July 20, 2020 after finding this forum and have been living with these batteries full time on our live aboard sailboat. Overall I have had ZERO issues with these batteries, have done ZERO maintenance and I'm very pleased considering their price point.

Brief overview of system:
BMS = REC-BMS
Charger = Victron MultiPlus being externally controlled by the REC-BMS (100% run from generator since we haven't stopped in a marina)
Alternator = Balmar 140amp with their programmable regulator
Solar = ~1000w with 5 MPPT Controllers

Brief overview of usage pattern:
We need to run our watermaker every 5 days, so initial system was designed so that we could live off of solar until the 5th day, then run generator to make water and top off batteries. This has worked in the dry/summer months, but in the winter and rainy seasons we can only go about 3-4 days before needing to charge. I typically charge when we get in the 35-45% remaining range, but I have gone down as low as 25% on occasion.

Observations/Questions:

1. One thing I've noticed is w/ the 140amp alternator, the REC-BMS cannot keep up with balancing, so the first pack always hits 3.6v while the others are in the 3.5v or 3.4v range.

1. When the packs were new, I could get to 14.2 at 100%. After year one, I was at ~13.8 and 96%, today I'm at ~13.6 and 92%. These voltages are hit by the Victron Multiplus charger (externally controlled by the REC-BMS), when it start to hit these voltages, it goes from putting in its normal amperage down to ~10ams/hr. Basically it seems to drop in to float (or is it absorbtion). When I shut down the generator, the solar panels will continue charging and can bring the final percent up a couple more (so from 92% to 94%).

Any guidance on what maintenance I can do to get these cells back up to 14.2 and 100%
Should I pull them all and do a top-balance?
Should I rebuild the packs to change up the cells since pack 1 has seen more 3.6v than the other cells?

I've added images of the individual voltage readings at each cell after one pack started hitting 3.6v as well as an image from the REC-BMS readout.

Thanks for any help and let me know if anyone has any questions about my setup or would like more info!

You have issues, not Zero.
It looks your cells have very different internal resistance, maybe even different Capacity. With 1100AH you need to pull 400A constant to get above a 0.3C which is considered to be a moderate high load that start to challenge the cells that they start to differ.
Actions:
1)Yes take them apart and top balance each cell individually(best in the morning after REC brought them already close), your bank is out of balance.
2) after top balance you know how each cell is performing, number them 1 best 16 weakest. Now group 1 and 2 with 15 and 16, 3 and 4 with 13 and 14…put the 2 better cells outside and weaker in the middle of the 4p pack
3) I would add an active balancer minimum 4A to your setup. 4 paralleled cells need a lot of amps to be balanced, the internal REC balancer is too small for that
You can see that at cell 1 peaking to 3,7V while another is at 3,4 and 120A or 140A is not much charge for a 1100A bank…0.13C is nothing…

From my experience 3 cell parallel is max so you see if a cell gets a problem. After that I split them up into 2 banks with 2 BMS. That’s one reason why I use Electrodacus, cheap so it’s easy to add a 2nd BMS or have one as spare.
Maybe go 24V, a lot of advantages and costs are not very high to swap. Nearly all can be done with boost and buck converters which are cheap.

[CaptainRivet]

Sorry could not edit after 30min, so reposted with corrections, forget the above post.
Bad news you have several issues, not Zero.
It looks your cells have very different internal resistance, maybe even different Capacity. With 1100AH you need to pull 400A constant to get above a 0.3C which is considered to be a moderate high load that start to challenge the cells that they start to differ.

One cell block at 3,721V, that should never happen. You maybe damaged cell 1 block already…
Your charge cut-off should be at max 3,65V, better 3,6 or conservative 3,55V what I recommend.
Change that immediately and go through all of your charge cut off scenarios to make sure you tackle all of them.
Actions:
1)Yes take them apart and top balance each cell individually(best in the morning after REC brought them already close), your bank is out of balance.
2) after top balance you know how each cell is performing, number them 1 best 16 weakest. Now group 1 and 2 with 15 and 16, 3 and 4 with 13 and 14…put the 2 better cells outside and weaker in the middle of the 4p pack
3) I would add an active balancer minimum 4A to your setup. 4 paralleled cells need a lot of amps to be balanced, the internal REC balancer is too small for that PN catnewbee he has a REC with 1000AH Winston cells and added active balancers that work well. Ask him which ones to get.
4) check busbar to cell post connection that they all have the same Resistance, sand with 800grid wet, clean the pole and immediately put noAlox or similar on the pole directly, so pole and busbar have a very Good electrical connection. Are all nuts tight with the same NM so connection is well? I use flange nuts without washer and secure them with a drop of nail lacquer, just use the one your wife/girlfriend…uses or get the cheapest one at the supermarket…handy as cheap and soft loctide, use that since 30years on all my race cars on every nut and screw. You can also see if you forgot to tight down if you unscrewed it.
You can see that at cell 1 peaking to 3,7V while another is at 3,4 and 120A or 140A is not much charge for a 1100A bank…0.13C is nothing…

From my experience 3 cell parallel is max so you see if a cell gets a problem. After that I split them up into 2 banks with 2 BMS. That’s one reason why I use Electrodacus, cheap so it’s easy to add a 2nd BMS or have one as spare.
Maybe go 24V, a lot of advantages and costs are not very high to swap. Nearly all can be done with boost and buck converters which are cheap.

[captNordy]

CptRivet,

Thanks so much, I'll reach out to Catnewbee and see what balancer they have working for them.

I'm using the flange nuts now and nothing has come loose. When I haul out in Feb I'll top-balance and investigate each cell and rebuild the packs as you suggested including the wet sand!

Thanks again!