Problems with renogy 170ah batteries

[meerkatmag]

Quick update. Leaving the batteries to balance themselves for several days has not worked! They are worse now than before. My previous pretty good batteries now won't charge up as much.

Also, more worrying. I've tried to count the cells in the one with the open case. I don't think it has 53 cells in each bank. It's hard to count exactly without removing them, but I'm pretty sure there's not 212 in total. Looking at yzman's photos I can see already that he has more cells than mine.

What's more, I have weighed my batteries and they are not all the same. They range between 19.5kg and 19.9kg.

The advertised weight is 22kg by the way...

 

[Aussieguy]

I wish it was easier to open the case, I practically destroyed mine trying to get at the cells. Agree once you can get in it could be easily rectified.

ever removed the top off a soda can with a grinder.... you just grind off the joint
easy and clean

same thing could be done to a battery hold the 4 inch grinder FLAT and lightly grind off the edge of the battery
no chance to damage components inside

flap disk from harbor freight is better than a hard metal grinding wheel... don't be tempted to use a thin cut-off wheel and plunge cut into the case.

Sorry Will....
no place for a oscillating saw if you want neat cuts.
and yes you DID NOT hit that wire it was pinched by the case

 

[meerkatmag]

Another update.

The bms isn't the only problem with mine. It was heavily unbalanced but with a new jk bms installed and the cells totally balanced now I still have issues with charging.

It seems cell 4 charges to a higher voltage than the other cells and charges and discharges at a different rate.

Cells 1,2+3 won't charge up to any higher than 3.378v. I've tried charging individual cells and they refuse ro go any higher. All three identical. Whereas cell 4 goes up to 3.6v.

However doing a stress test all 4 cells seem to produce power and the battery is actually able to supply around its rated ah. During discharge Cell 4 volts stay higher to start with then after a while all 4 cells end up around same amount. When it starts to get low cell 4 volts drops lower than the other cells. When charging back up it does the same in reverse.

If I charge it to 13.6v at low current (7ah)
It actually stays in balance all the way up (helped a bit by the 2a active balancing). And all the cells end up around 3.340v. If you continue to charge up to 14.4v then only cell 4 continues to charge the other cells stay the same and the battery becomes extremely unbalanced.

Even in my newer batteries after a few light charges and discharges the battery won't charge up as much so I think the same thing is happening.

Perhaps these cells are not performing as they should? I wonder if they are not happy being charged up to 3.6v and they would prefer a lighter charge to 3.4v.

Something weird going on and its across all of my batteries. Not sure how cell 4 gets affected differently to the others. Perhaps as it is connected directly to the positive terminal this has some effect?

It uses 26650 cylindrical cells not the usual square box style.

 

[Hardergamer1]

Another update.

The bms isn't the only problem with mine. It was heavily unbalanced but with a new jk bms installed and the cells totally balanced now I still have issues with charging.

It seems cell 4 charges to a higher voltage than the other cells and charges and discharges at a different rate.

Cells 1,2+3 won't charge up to any higher than 3.378v. I've tried charging individual cells and they refuse ro go any higher. All three identical. Whereas cell 4 goes up to 3.6v.

However doing a stress test all 4 cells seem to produce power and the battery is actually able to supply around its rated ah. During discharge Cell 4 volts stay higher to start with then after a while all 4 cells end up around same amount. When it starts to get low cell 4 volts drops lower than the other cells. When charging back up it does the same in reverse.

If I charge it to 13.6v at low current (7ah)
It actually stays in balance all the way up (helped a bit by the 2a active balancing). And all the cells end up around 3.340v. If you continue to charge up to 14.4v then only cell 4 continues to charge the other cells stay the same and the battery becomes extremely unbalanced.

Even in my newer batteries after a few light charges and discharges the battery won't charge up as much so I think the same thing is happening.

Perhaps these cells are not performing as they should? I wonder if they are not happy being charged up to 3.6v and they would prefer a lighter charge to 3.4v.

Something weird going on and its across all of my batteries. Not sure how cell 4 gets affected differently to the others. Perhaps as it is connected directly to the positive terminal this has some effect?

It uses 26650 cylindrical cells not the usual square box style.

The cells that charge faster and then discharge faster have less capacity, either been damaged by overcharging or have been taken to a low state of charge, both by a bad BMS, or they could be B-grade cells with less capacity to start with and probably have high internal resistance, also the reason why one parallel group discharges more than the rest, normally the first or last in the series is it is used to power the BMS on cheaper units where the more expensive ones like ANT JK and Daly take there running power from the whole string.

To me, it sounds like the cells aren't matched for internal resistance which then gives different capacities.

 

[meerkatmag]

Before I abandoned this battery, I thought I'd have another go at charging each cell individually. It took ages, like hours and hours but in the end I did manage to get cell 1,2+3 up to 3.6v. Then I turned the JK balance on and let it balance all 4 cells at this fully charged state. And like magic the battery now works perfectly! See attached before and after pics.

Mistake I made previously was assuming if it was balanced at 13.3v then it was fine. However after reading a few amazing posts on this forum I realised that was not going to work with lfp cells. I can't say how brilliant this forum is by the way.

After all that it was just a top balance problem. I have since discharged it and then charged it up again and goes right up to 14.4v and does absorption perfectly fine.

So, in theory all we have to do is open the battery cases, charge each cell to 3.6v exactly and then they will charge and work properly. It might need rebalancing from time to time. I'm going to install one of those cheap 4s balancers to my batteries and try to get them all working.

 

[Quattrohead]

Have you ever seen a pack do this? This was the worst of the four 170ah Renogy batteries I had. I was able to use the pack in the past without issues, the battery sat for a few months and than it locked all charge and discharge fuctions due to the exterme low and high values.

I am unable to understand how it drifted into 3 cells empty and 1 cell overcharged? Thats why I think the BMS did it somehow, knowing the pack was usable in the past.

Cell 1 2.453 (Cell 09 on JK BMS)
Cell 2 2.495 (Cell 10 on JK BMS)
Cell 3 2.449 (Cell 11 on JK BMS)
Cell 4 3.800 (Cell 12 on JK BMS)

I also confirmed correct voltages on a seperate multimeter, weird right?

Look at those resistance readings, something totally up with that !!!

 

[sunshine_eggo]

Look at those resistance readings, something totally up with that !!!

What do you mean? Those aren't cell resistance values. They're sense wire resistance values. It's what the BMS uses to compensate for the voltage drop due to the balance current in the sense wires.

 

[Quattrohead]

What do you mean? Those aren't cell resistance values. They're sense wire resistance values. It's what the BMS uses to compensate for the voltage drop due to the balance current in the sense wires.

Yes and they are all over the place which suggests bad wiring to me. You're suggesting different cell resistance instead?

 

[sunshine_eggo]

Yes and they are all over the place which suggests bad wiring to me. You're suggesting different cell resistance instead?

Ah... I didn't realize you were quoting an older post.

It's my understanding those values are calculated and iterative and will stabilize over time.

@Yzman321 how do your resistance values look 20 days later?

 

[Yzman321]

Ah... I didn't realize you were quoting an older post.

It's my understanding those values are calculated and iterative and will stabilize over time.

@Yzman321 how do your resistance values look 20 days later?

The resistance is still all over the place with my pack, however I am able to pull full capacity.

Here is how they look today, see attached image.

 

[Yzman321]

Before I abandoned this battery, I thought I'd have another go at charging each cell individually. It took ages, like hours and hours but in the end I did manage to get cell 1,2+3 up to 3.6v. Then I turned the JK balance on and let it balance all 4 cells at this fully charged state. And like magic the battery now works perfectly! See attached before and after pics.

Mistake I made previously was assuming if it was balanced at 13.3v then it was fine. However after reading a few amazing posts on this forum I realised that was not going to work with lfp cells. I can't say how brilliant this forum is by the way.

After all that it was just a top balance problem. I have since discharged it and then charged it up again and goes right up to 14.4v and does absorption perfectly fine.

So, in theory all we have to do is open the battery cases, charge each cell to 3.6v exactly and then they will charge and work properly. It might need rebalancing from time to time. I'm going to install one of those cheap 4s balancers to my batteries and try to get them all working.

Happy to see you were able to get all cells to their upper limit. I needed to keep my pack on charge to get the active balancer to top balance due to LFP’s shallow voltage curve. It took a long time with my BMS balancing current of only 1 amp.

Did you perform a capacity test? I was able to get 168 ah from mine however I wasn’t fully balanced at that point, so I might be able to get more now.

About the less cells in your packs versus mine? Did you confirm this after?

These packs should have 53 per string like you said and 3.4ah each, so theoretically 180ah.

 

[sunshine_eggo]

Some worse, some better.

I would be concerned that the sense leads are not installed consistently.

 

[meerkatmag]

Happy to see you were able to get all cells to their upper limit. I needed to keep my pack on charge to get the active balancer to top balance due to LFP’s shallow voltage curve. It took a long time with my BMS balancing current of only 1 amp.

Did you perform a capacity test? I was able to get 168 ah from mine however I wasn’t fully balanced at that point, so I might be able to get more now.

About the less cells in your packs versus mine? Did you confirm this after?

These packs should have 53 per string like you said and 3.4ah each, so theoretically 180ah.

Yeah I have tested that pack with approx 100amp draw for 80mins and it ended at 12.92v. Charging back up took 134ah. So assuming it was 20% capacity left at 12.9v this shows around 167.5ah capacity. Very similar to yours and I'm pretty happy with that.

I'm in the process of top balancing and adding an ebay 4s balancer to another pack just now, see attached stills. Hoping this will work as well as the jk. I added a switch in the top so I can turn the balancer on/off and it has an led to show when the thing is balancing. Some soldering needed but not a big deal.

In terms of cells, I strongly suspect there are fewer than 53 cells per bank however I don't want to deconstruct the case to get proper access to count them. The capacity is good so for now I'm going to let that slide.

 

[Yzman321]

Yeah I have tested that pack with approx 100amp draw for 80mins and it ended at 12.92v. Charging back up took 134ah. So assuming it was 20% capacity left at 12.9v this shows around 167.5ah capacity. Very similar to yours and I'm pretty happy with that.

I'm in the process of top balancing and adding an ebay 4s balancer to another pack just now, see attached stills. Hoping this will work as well as the jk. I added a switch in the top so I can turn the balancer on/off and it has an led to show when the thing is balancing. Some soldering needed but not a big deal.

In terms of cells, I strongly suspect there are fewer than 53 cells per bank however I don't want to deconstruct the case to get proper access to count them. The capacity is good so for now I'm going to let that slide.

Great idea on the adding the active balancer while using the original BMS. Seeing the recent price reduction in LFP batteries is astonishing, its hard to invest the money to swap out all BMS's for added value.

 

[meerkatmag]

Great idea on the adding the active balancer while using the original BMS. Seeing the recent price reduction in LFP batteries is astonishing, its hard to invest the money to swap out all BMS's for added value.

Yeah and also I couldn't get the jk to fit in the case easily. I did manage to squeeze it all in and screw the case closed in the end but it's tight and I don't like it. The balancer fits nicely and should make up for the inadequacies of the bms, hopefully! I'm getting quite good at opening these cases without damaging them. A heat gun is the answer!

 

[Yzman321]

View attachment 186602

Some worse, some better.

I would be concerned that the sense leads are not installed consistently.

Bingo! I checked over the sense wires and noted some deficiencies in my work. I didn’t strip some wires enough for the WAGO type connector I used. Enough to make connection however not all strands of the wire, good thing my active balancing was one 1 amp! The voltages remained the same, just the resistance after removing the bottle neck I unknowingly created.

 

[sunshine_eggo]

Bingo! I checked over the sense wires and noted some deficiencies in my work. I didn’t strip some wires enough for the WAGO type connector I used. Enough to make connection however not all strands of the wire, good thing my active balancing was one 1 amp! The voltages remained the same, just the resistance after removing the bottle neck I unknowingly created.

Good to hear. I'd be curious to see the resistance values and what happens when you set a higher balance current.

 

[Yzman321]

Good to hear. I'd be curious to see the resistance values and what happens when you set a higher balance current.

Thank you for the input here, I would have assumed it was the cells for sometime.

My JK BMS is limited to 1 amp unfortunately. It’s undersized for my pack however happy to have controllable active balancing versus only passive.

Note: I am top balancing the pack again, so disregard the huge cell differential of 0.258v between 7 and 16.

 

[sunshine_eggo]

.062-.083 are notably better!

 

[Dktk]

So on those 170 ah batteries could you connect a balancer to them some how and use the bms that came with them