Jakiper battery lost capacity?

[ArkRob]

One of my Jakiper batteries now indicates 93.0 amp hours instead of 102.9 on the LCD display.

I have not checked any further than this.

Did I really lose ~10 amp hours - or do I need to do a reset, or something else?

There are 10 cycle on the battery at this point.

 

[sunshine_eggo]

can you tell if the battery in question has been triggering cell over voltage protection? It's very common for an imbalanced battery to register less capacity because only one cell is getting fully charged.

 

[ArkRob]

can you tell if the battery in question has been triggering cell over voltage protection? It's very common for an imbalanced battery to register less capacity because only one cell is getting fully charged.

It has recorded over-voltage protection, but they all have. I thought that was from balancing? I have looked but not noticed an extreme voltage when nearing the top of the charge.

Chargers include a Victron MultiPlus set for LiFePo4 batteries and the signature Solar charger.

I THINK I saw the display indicate 100% state of charge while the 4th state of charge LED was still blinking indicating charge being taken.

All the cells are very close in voltage (currently 3330Mv to 3331Mv currently)

Yet, the display on this one still indicates 93.0Ah while the others indicate 102.9Ah

 

[sunshine_eggo]

It has recorded over-voltage protection, but they all have. I thought that was from balancing? I have looked but not noticed an extreme voltage when nearing the top of the charge.

Over voltage means a cell hit max, and the battery cut the charge circuit off.

Balancing generally only occurs when the charge circuit is active.

Chargers include a Victron MultiPlus set for LiFePo4 batteries and the signature Solar charger.

I THINK I saw the display indicate 100% state of charge while the 4th state of charge LED was still blinking indicating charge being taken.

All the cells are very close in voltage (currently 3330Mv to 3331Mv currently)

They always are in that range. Resting LFP and LFP in the operating range deviate very little due to the flat voltage curve. Same voltage does not indicate balance. Balance refers to state of charge. The only places you can truly balance is 0% and 100%.

What are the cell measurements when the battery is at peak voltage?

Yet, the display on this one still indicates 93.0Ah while the others indicate 102.9Ah

This could be simply due to imbalance. A Battleborn user had just over 50% of rated capacity due to imbalance. After charging and holding at 14.2V+ for like a week, it returned to > 90% capacity. He used it for an extended period of time never taking it above 14.2V, and the BB batteries don't balance below 14.2V.

The goal here is to establish if cell imbalance is contributing to capacity loss.

If you can establish cell imbalance exists, you can likely deal with it to recover that lost capacity. You can lower absorption a little, increase absorption time and increase your float voltage to improve balance over days/weeks and still use the vast majority of your battery capacity.

 

[ArkRob]

Thank you for your help.


I will get them fully charged and look at the voltages.

The Multiplus is currently set to Victron defaults - 56.8V absorption, 54.0V float and 1 hour absorption time every 7 days.

Assuming they are different, do you have suggestions for absorption/float voltage and absorption time? The Jakiper manual states balancing voltage is >54.4 or 3.4V/Cell. Is that voltage a good place to start, or 54.5 to give it some room?

Or, leave the absorption alone (56.8) and set the float to the 54.4 balance level instead of the 54.0 default?

 

[sunshine_eggo]

Thank you for your help.


I will get them fully charged and look at the voltages.

The Multiplus is currently set to Victron defaults - 56.8V absorption, 54.0V float and 1 hour absorption time every 7 days.

If you find that it's actually triggering over-voltage, reduce absorption by 0.1V until it stops. Extend absorption to a fixed 2 hours.

Assuming they are different, do you have suggestions for absorption/float voltage and absorption time? The Jakiper manual states balancing voltage is >54.4 or 3.4V/Cell. Is that voltage a good place to start, or 54.5 to give it some room?

I would put float at 3.45V/cell or 55.2.

 

[ArkRob]

Thank you again for your help.

 

[ArkRob]

There was a large spread at peak voltage. 3364Mv to 3515Mv.

I have set the absorption and float as suggested and will update after a couple of weeks if I can remember to do so.

 

[sunshine_eggo]

A single cell spiked to 3515 with the others < 3.4V? If that's the case, then you definitely have an imbalance issue.

Worth noting that you can easily get LFP to 98%+ charge at 3.45V/cell, but it will take a longer absorption period... which is very good for balancing.

If you can't get the BMS to stop tripping by 0.1V decrements, the extreme solution is a float of 54.7 and an absorption of 55.2 for 6 hours.

 

[ArkRob]

It's balancing away now.

You were absolutely correct.

Closer study found that one cell would trigger the over voltage protection even at conservative overall charge voltages, so the extreme settings were needed to slowly reach the BMS balancing voltage without overwhelming it.

I think my usage threw everything out of whack with lots of partial discharge and partial recharges.

I built a "profile" saved as "Balance" in Victron Configure that I can use for extreme case like this, and will modify my usage to have more full charges to hopefully keep it balanced better anyway.

I guess the biggest takeaway is that the cells are individual, so looking at the battery as one unit is bad practice.

I cannot thank you enough for your help.

 

[sunshine_eggo]

Glad to hear things are moving in the right direction!

 

[eabyrd]

I am also having horrible imbalance issues with a Jakiper 1st Gen battery with Cell 13 tripping OVP while the other cells are still in the high 3.3 range, low 3.4 range. Since I don't have access to a victron rig (MPP LV6548) I've tried using a moderate float voltage (55.2 to 55.8) but the BMS keeps shutting down saying the battery is fully charged long before any progress is made on the imbalance.

Prior to 13, it was 12 that was the runner. 12 tripped UVP on the one occasion I did a deep discharge, and thirteen became the new "High" cell from that point on with 12 now being the constant laggard.

Any suggestions? Should I invest in a 16s Active Balancer? Currently the BMS is reporting a capacity of 94 AH (94% SOH) after only 45 cycles.

 

[ArkRob]

Test on discharge to see if one of the same runners becomes the first to nosedive. If so you likely have a bad cell.

Mine actually turned out to be a bad cell, and Jakiper sent me a replacement along with an individual cell charger to match the new to old state of charge. Something to keep in mind for others buying Jakiper - I didn't mind doing the changeout, but the warranty will include replacement parts for you to change. I was not charged for the cell, charger, or shipping.

Do the discharge test first to get that out of the way.

After that, if it is not a bad cell, the settings Sunshine_eggo posted helped me get a different pack back under control.

I would avoid an active balancer, but an individual cell charger is helpful in extreme cases. Discharge until one cell gets to ~2.8 volts, stop the discharge and add power to that cell. Repeat until another cell is slightly below the original problem cell when voltage is near ~2.8 volts.

This may not apply to you, but to maintain them, make SURE you regularly (daily if possible) charge into the upper knee of the voltage curve (>3.4 volts.) The BMS only dissipates cells above 3.4, so trying to extend the life of the batteries through moderate charges and discharges actually works against you by never having control over either the top or bottom of the charge, leading to nothing but a big-ole-mess (technical term) and reduced capacity because of ever growing imbalances.

 

[sunshine_eggo]

Tell us more about this single cell charger.... ?

 

[ArkRob]

Tell us more about this single cell charger.... ?

It is a "Lv yuan lian" charger.

110 plug on one side, small pos/neg alligator clips on the other.

Model#: H10980150W

Input: 110V-220V 50-60 Hz

Output: 3.65V/6A

I've never seen or heard of it before. I do not seem to have died or exploded anything from my limited use of it, but it isn't exactly hefty and I would not use it commercially.

 

[eabyrd]

see if one of the same runners becomes the first to nosedive.

Oh yeah, 12 is the weak sister

what is the advantage of doing a bottom balance over a top balance? Andy OGG seems to have extremely good success with top balancing using active balancers

i sent Jakiper the data file, we will see how they respond

 

[eabyrd]

(daily if possible) charge into the upper knee of the voltage curve (>3.4 volts.)

i run my bank between 80% to 40% generally. The EG4s and the BB Husky stay balanced,

 

[ArkRob]

Oh yeah, 12 is the weak sister

what is the advantage of doing a bottom balance over a top balance? Andy OGG seems to have extremely good success with top balancing using active balancers

i sent Jakiper the data file, we will see how they respond

It's situational - the only advantage of the bottom balance that I know of is that it is easier to add power than to get rid of it.

The charger I used sends 6 amps to the cell, I don't remember the dissipation for the Jakiper BMS, but I think it was 0.6 amp.

Having said that, if you have one cell at a higher state of charge than the rest, it wouldn't make sense to bottom balance the other 15 one at a time. In that case, I would look at building a resistor for that one cell rather than wait for the BMS to correct a state of charge imbalance.

I don't like the active balancers because of all the extra connections. All those extra connections inside a rack battery form factor multiplies the headaches and bad happenings chances.

 

[ArkRob]

i run my bank between 80% to 40% generally. The EG4s and the BB Husky stay balanced,

If they are actually balanced then I think you've been lucky, and I am not sure how much longer your luck will last with that.

Keep in mind that in the 40%-80% range, you are in the REALLY flat part of the voltage curve, and the cells can be considerably out of balance with very little difference in voltage. This difference will grow though, and then all of a sudden, (because it breaks out of the flat part of the voltage curve) you will be back to where one cell is a runaway or diver.

The only real control you have over the cells is at the top and at the bottom knees of the voltage range. If you never really enter those two extremes, the state of charge will shift between individual cells because of the resistance differences, and overall capacity will drop.

 

[eabyrd]

I think you've been lucky,

The Husky has been run that way for over 18 months, the EG-4 about 8 months. I fill em up on occaision and they both stay within 20MV all the way to 3.5 volts per cell. I never bother to push higher than that, I mean why all you're doing is shortening your cycle life?

I ran em all down to 20% and charged the group at 60 Amps until 56.2 volts. The Husky stood at 15MV deviation, the EG4 at 50ishMV and the Jakiper at 208MV (it was also shutdown due to OVP). It isn't luck, it's quality.

EG4 going forward. BB is just too expensive

 

[eabyrd]

dissipation for the Jakiper BMS, but I think it was 0.6 amp

passive balancing at that rate against a 6 amp charge current will never get you anywhere, especially with the tendency of that BMS to shutdown the process when it considers the battery to be "full". The fact it only balances at all when there is a positive charge current means it'll never bring down a runner by any meaningful amount.

 

[eabyrd]

look at building a resistor for that one cell

Why do that instead of attaching a good capacitive active balance to transfer the energy from the runner to the laggards