Problems with renogy 170ah batteries

[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

 

[meerkatmag]

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

Yeah, that's what i've done. It works well. But you also need to top balance each cell with a bench top power supply. I'm making a youtube video with some tips on how to do it, including opening the case without messing it up. I'll post it here if it's helpful.

 

[Dktk]

Yeah, that's what i've done. It works well. But you also need to top balance each cell with a bench top power supply. I'm making a youtube video with some tips on how to do it, including opening the case without messing it up. I'll post it here if it's helpful.

yes that would be great if you posted that here ,also part numbers?

 

[fumpel]

Hi everybody,

I just registered to add my name to the list of "victims"...

I have been using two of the 170 AH Renogy batteries in my diy camper van for about a year now. First they were "good enough" (charging to about 13.3 V). Now after a winter of sitting in my driveway they won't charge to more than 12.9v.

After reading this thread, I just opened the first battery and found the same situation. The first three cells sit at 3.29V, the last one at 3.41V. I'm now charging the first three cells simultaneously to 10.23V with my dc workshop power supply at about 9 amps.
Will do the same thing to the other battery afterwards. Hopefully the cells will be more balanced after this and give me more capacity.
I will keep you posted...

As I need the car next week, this will have to do for now. I'll see during the next few month, wether they will get unbalanced again.

This thread has been tremendously helpful! Thanks so much!

 

[Whinny]

I would suggest not doing that, if you want to charge individually to 3.5 or so that is fine, but not in a group of 3. 1 group will most certainly go out of balance and overcharge causing damage. Remember you have no protection in place while doing this.

 

[740GLE]

I second take the time and shove only 10a into one cell at a time. Set your voltage to 3.5v then connect the leads.

Or better yet just rip out the junk BMS and install a better one and be done with it.

I kinda want to pick up one of these junk units and rehab it if I could score them for cents on the dollar.

 

[fumpel]

I would suggest not doing that, if you want to charge individually to 3.5 or so that is fine, but not in a group of 3. 1 group will most certainly go out of balance and overcharge causing damage. Remember you have no protection in place while doing this.

Thanks a lot for the warning... I'm very careful and check the voltages of each group regularly. They are almost identical (+- 0.01 v).
But I think my PSU is lying about it's current. It's taking far too long for 10 amps.

 

[fumpel]

I second take the time and shove only 10a into one cell at a time. Set your voltage to 3.5v then connect the leads.

Or better yet just rip out the junk BMS and install a better one and be done with it.

I kinda want to pick up one of these junk units and rehab it if I could score them for cents on the dollar.

I will definitely get a new BMS to get rid of the problem. For now I just need a quick fix, because the van needs to survive 3 days of winter camping next week and I need the capacity.

 

[meerkatmag]

I will definitely get a new BMS to get rid of the problem. For now I just need a quick fix, because the van needs to survive 3 days of winter camping next week and I need the capacity.

Hi,
definitely be careful charging multiple cells at once while bypassing BMS. It will look fine at lower SOC but if any cells are out of balance they can become overcharged very quickly. Cell at a time is best.

I have fixed mine with a balancer, I found that the BMS in these batteries isn't creating the issue, it's just not fixing it. So you can just fit a balancer and top balance and then they will be ok.

If you fit the JK BMS it will sort it out but it's a tight fit in that case. Also it's a lot more expensive.

 

[meerkatmag]

Here's my video about fixing these batteries, hope it's useful for someone:

 

[Alkaline]

Here's my video about fixing these batteries, hope it's useful for someone:

Very good, I have helped almost a dozen people fix their batteries using the same method, in my case I did not find a big difference on keeping the balancer on or off so I just kept it running on. I think it may drain the batteries a bit faster but nothing noticeable. This has helped me correct 4 SOK batteries and some other batteries that required opening them up (just like the renogy).

I would recommend you perform a capacity test to see what you have now that the batteries have been fixed.

 

[meerkatmag]

Very good, I have helped almost a dozen people fix their batteries using the same method, in my case I did not find a big difference on keeping the balancer on or off so I just kept it running on. I think it may drain the batteries a bit faster but nothing noticeable. This has helped me correct 4 SOK batteries and some other batteries that required opening them up (just like the renogy).

I would recommend you perform a capacity test to see what you have now that the batteries have been fixed.

I thanks for the feedback. That's interesting about the balancer being on all the time. So did you bother with a switch? Its certainly a pain having the wire that in.

My old batteries were tested before this and they provided around 80ah in total. After balancing they are pretty much as advertised, around the 170ah. I haven't Discharged them below 12.9v so it's an estimation. It definitely helped a lot.

One of my original batteries has suffered some damage from being so out of balance for so long. It seems to loose charge very quickly and settles to 13.2v after a few days of sitting. It still works well but I think they cells have had a rough time. I'm not going to use this one but the others are all now perfect so I have 4 in my van. More power than I will ever need!