I run three 5s packs in series. Today one of the series connections between the packs broke and one of the battery packs died. I measured 3 of the series on the one pack and readings are good. Last two read zero. What would be the best way to repair the pack? New cells would not have same charge, discharge, IR as the old cells in the pack. Should I just start over and build three new 5s packs or 1 5s pack, or just repair the pack with close matching cells to what they read after I take it apart. For reference the packs are atleast 3 years old made from brand new Samsung 30Q cells.
Battery repair or start from scratch?
- Thread starter nalu808
- Start date
From-A-To-B
100 W
I’m not fully understanding the questions you posed at the end of your post, nor the exact details of your battery, so I’ll just give general advice.
In my opinion, it comes down to what you expect of your batteries and this repair/replace project.
30Q cells are known for self discharge issues and don’t have a great reputation in terms of cycle life. You could absolutely replace the bunk p-groups and get more life from those batteries. You’d have to stay on top of battery balancing, but that’s kinda the norm with a 30Q battery, anyway.
Total replacement is going to be a better plan if you’re looking for another 3 years of service from some batteries. And this time, I’d look into using a different cell.
Either will get you down the road. Depends on your needs and expectations.
In my opinion, it comes down to what you expect of your batteries and this repair/replace project.
30Q cells are known for self discharge issues and don’t have a great reputation in terms of cycle life. You could absolutely replace the bunk p-groups and get more life from those batteries. You’d have to stay on top of battery balancing, but that’s kinda the norm with a 30Q battery, anyway.
Total replacement is going to be a better plan if you’re looking for another 3 years of service from some batteries. And this time, I’d look into using a different cell.
Either will get you down the road. Depends on your needs and expectations.
The question is what is best practice for the 1 pack to repair it? Should I measure the cells
I know best practice would be to replace the whole thing. But what would be best practice for repair of the battery. Would i measure my current cells and try to matching cells to replace the 2 series groups that are dead. Or replace the 1 dead 5s pack with a similar capacity pack as my 2 good ones. Replacement of 1 5s pack or repair of the 2 dead S groups is more in my budget.
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As From-A-to-B said, it depends on what you need / expect the pack to still be able to do for you after the repair.
If you need a specific amount of capacity, for instance, then you'll need to make sure the remaining original cells all have enough.
If you need the pack to have a certain maximum amount of voltage sag, you'd need to make sure the remaining original cells are all at least that good.
If you need the pack to last a certain minimum amount of lifespan, you'd need to guesstimate if the remaining orginal cells are going to last that much longer before repairing the pack again.
If the remaining original cells can't do the job you need them to, then you have to replace those, too, meaning you are rebuilding the entire pack with new cells or replacing the whole pack wiht a completely different one (whichever way you want to do it).
Well, technically you could just add more new cells in parallel with the remaining originals to stiffen up their voltage under load and increase the capacity of those groups, but I don't know if you have the space for however many extra cells that will be.
If you need a specific amount of capacity, for instance, then you'll need to make sure the remaining original cells all have enough.
If you need the pack to have a certain maximum amount of voltage sag, you'd need to make sure the remaining original cells are all at least that good.
If you need the pack to last a certain minimum amount of lifespan, you'd need to guesstimate if the remaining orginal cells are going to last that much longer before repairing the pack again.
If the remaining original cells can't do the job you need them to, then you have to replace those, too, meaning you are rebuilding the entire pack with new cells or replacing the whole pack wiht a completely different one (whichever way you want to do it).
Well, technically you could just add more new cells in parallel with the remaining originals to stiffen up their voltage under load and increase the capacity of those groups, but I don't know if you have the space for however many extra cells that will be.
From-A-To-B
100 W
And in terms of the replacement project — I’m not the expert on batteries, just a practitioner, but I’d be reluctant to replace your two p groups with anything other than Samsung 30Q cells.
Mixing old with new cells introduces enough variability to manage. Mixing and matching new cell types into one battery is possible, sure, but seems like a headache to me.
I wouldn’t bother with measurement at your stage of the project. You know your original cells have degraded somewhat, and any fix is jus to prolong the life of a used battery. Save yourself the effort. It’s all caddy wampus from here out, until you choose to start over again with new cells and a new battery altogether.
My two cents.
Mixing old with new cells introduces enough variability to manage. Mixing and matching new cell types into one battery is possible, sure, but seems like a headache to me.
I wouldn’t bother with measurement at your stage of the project. You know your original cells have degraded somewhat, and any fix is jus to prolong the life of a used battery. Save yourself the effort. It’s all caddy wampus from here out, until you choose to start over again with new cells and a new battery altogether.
My two cents.
