Analysis of my Main Battery Pack

Used to get quite a bit of distance, current formation was getting 22km which was alright.
10S10P 36V and 16Ah(new) cells are Sony 18650-V which are 1.6Ah.
575Wh should net me 26km at 22Wh/km when new, 375lbs, never pedal
Pack is not new but is a 2 year old pack. Used every day! Charged multiple times a day and been a real champ for me.
The 3.41 and 3.62 voltages were dragging the entire pack down. Distances were pathetic!
Understandably so!

Perhaps this go around, I will wire in balance leads, we will see!

I will balance charge strings B, C, D to exact voltages and pair them together into its own pack.
Moistness does not feel that bad inside the pack, on the wood or on the tabs.
It was taped up with Gorilla tape and used 1/8" mdf board.

The came too loose too easily is just a statement of fact that when I was opening up the pack and peeling back the Gorilla tape, taking the 1/8" mdf wood off, a series connection can loose too easily from a ~2" fall onto a glass topped desk, my office desk.

Here are the measured voltages.

Can you post a picture of the pack?

Having 5 parallel strings of 10s is an unusual pack configuration. Normally the parallel connections are made at every series cell, which forces the cells in each parallel group to be balanced.

Were the cells ever balanced during the 2 years?

fechter said:

Can you post a picture of the pack?

Having 5 parallel strings of 10s is an unusual pack configuration. Normally the parallel connections are made at every series cell, which forces the cells in each parallel group to be balanced.


Were the cells ever balanced during the 2 years?

Click to expand...

No BMS, not even balance leads to use 80W balance charger, However I do balance them when I get them, let sit, make note of chages

I am just lazy is all, I received 5S2P packs, I open them up, discard pcb and housing

My phone is somewhere around, if I had it here, I'd snap some pics, but I will explain it all better for you

The battery pack has been through a handful of different changes, from 48V 13S, 36V 10S, different Ah combo's.
The battery "bricks" as I like to call them are 5S2P, arranged in a desired format, as discussed^^^^
Some end up not living due to situations like we have here.
So healthy sections are taken out and reused.
While unhealthy sections are "helped along" to use as a bicycle light, stored or responsibly discarded (fire station)

BTW I did edit my previous post, new picture of spreadsheet.
All in all its a pretty easy fix.

I should open it and inspect more frequently.

I should solder in balance leads to each 2P, bulk charge to 4.00V then balance charge to 4.20V. Saves time especially when all I got are them cheesy ass 80W rc chargers, wishing for an iCharger, Satiator, and a Grinspector.

I should use the mini voltage meters to keep a closer eye on things.

For a clearer image of the situation:
What I have now is five "strings" of 10S2P on pieces of computer paper with their voltages written down.
They are 5S2P "bricks" with tab welds on them. I then used solid copper wire to solder a series connection.
Visualize this:
I have one "string" that has two 5S2P soldered in series. 5S2P + 5S2P = 10S2P
I have another one that is the same as above. 5S2P + 5S2P = 10S2P
Then I have 4S2P + 4S2P + 2S2P and 5S2P + 4S2P + 1S2P and 5S2P + 3S2P + 2S2P
As seen in the spreadsheet.
Obviously I tie each positive and negative together from the ends of each 10S2P, to make a complete pack.
So yes maybe that is strange, not having a fully parallel wire across every 18650.

So the 5S2P can be sectioned out and made into various states from 1S2P, to 2S2P, to 3S2P, to 4S2P.

This is what I did originally, I charged each 5S2P "brick" to 3.75V and stored them in the office closet and I let sit for months and months. Periodically I would measure the voltages of everything, and see where the changes were happening. Overall everything was very good, a few bricks had to be split into smaller sections.

Hope that helps!

Got a plan layed out, easy fix. Nothing major.
One thing I forgot to mention in the "I should", yes yes yes a BMS I know I know.

OK comments please, I am ready for it!
Be easy on me.

Main pack, picture shown below.
Previous to this work...









So, it maybe awhile or not before I get this Main Battery Pack back together. I say "or not" because I need to do business taxes this weekend, have to clear up the desk.

It looks like you could gain a good amount of capacity by balancing the cells. You could do individual bricks with a RC balance charger.