Yah. I don’t notice any sag even at lower voltage at the end of a ride. I also get even more real range than I should according to the calc.
I just want to make sure that I am not damaging the cells prematurely. If it is purely just a bottleneck of the NESE and it is not hurting anything, I am totally fine with it.
I’ll charge it up fully and post my results.
Thanks for your help with this, I appreciate it!
20A is a huge amount of current for an HE4 as you are at its rating. Those cells will get hot and there will be a lot of voltage sag. This isn’t just an HE4 issue. Any cell runs poorly when you are drawing current up near its rating.
The HE4 is a poor performer though compared to other cells using chemistries and construction that are years newer.
You can certainly use them at 20A but I’d recommend 10A-15A as a decent performing, long cell life discharge rate. Just my personal recommendation, no hard science for this.
Their temperature is the best way to check this. Anything more than “very warm” if you are firmly grabbing a single cell is too hot IMHO.
It’s not getting hot enough to misform PETG at all if that means anything. I think the glass transition for petg is 70c
Apologies, Sir. I did indeed misinterpret your findings. And I know others have similarly given thanks but I wanna say what a treat it is to have you on the forum. Sending virtual beers in your direction my good man 
Ah cool ok that’s good to know, I had been going off your old comments plus the claimed rating of 20A continuous 35A burst. But to be honest, I don’t intend to use the whole pack above 40A much at all.
As for the old tech, yeah I knew I was making some compromises but the cells were like €1.70 each from a reputable seller so very much worth it in the current climate IMO
If any cells got hot enough to deform PETG their performance would be the least of your problems. 
45°C is about what most people would call “pretty warm” if firmly grabbing a cell. That’s about as high as you want to go in regular use.
60°C is about as hot as a cell can be before you can’t grab it firmly for several seconds. IMO this is as hot as you ever want a cell to get. It starts aging a lot faster at temps this high and it’s only another 15°C or so before the electrolyte starts breaking down and the exothermic chemical reactions get started (that can eventually lead to thermal runaway).
Good to know.
It’s a bit tough to take their temp when they are in their nese. I will try to take a reading off of the nickel strip to see it if conducts the heat at all.
I have a temp probe from the BMS taped to the pack, and the hottest it has gotten is 33c (granted this is through petg.
Also just a question out of curiosity, How is it possible for a cell to have negative voltage? My brother had a BKB pack that is about 2 years old and it recently went bad. I believe the BMS nuked the cells based on what I saw. While I was troubleshooting, I checked the voltages of some cells after I took them out, and a few actually had negative voltage.
The thermal resistance of the connection to the strip and the strip itself is much too high. Your reading will be very low compared to the actual cell temp. You can judge cell temp pretty well by just using a couple of fingers on the cell for a few seconds.
You’re measuring temp through the NESE holder wall? That temp can be, and is probably, much lower than the actual cell temp. There is a huge break when measuring through a thick layer of such a good insulator. Thick being anything more than a couple thousandths of an inch.
There’s no way to tape the sensor to a cell, even temporarily? The sensors they use have lousy thermal coupling to the cell and a very long response time but they can give a rough idea of the cell’s temp.
A pack that has gone badly out of balance, very badly, can allow cells to drop to zero volts. If you keep using the pack, unbalancing them even further, the cell voltages will continue to drop. This means they must go negative.
This also means you are essentially charging them with reversed voltage…one of the worst things you can possibly do to a cell. It’s a great way to get one to explode if done hard enough.
Yah, I know it’s not great.
I don’t see how it would be possible. The module needs to be fully closed up to make sure all of the cells have good contact and for structural strength. I could always pop one open after a ride.
Well, I’m glad I got rid of that pack…
That can work. They won’t cool fast and if you can get in there quickly you can get a good idea of their temp.
Can’t you make a small hole in one of the holders?
Thats a good idea. Going to give that a try.
You can also get very thin, flat thermistors laminated in kapton (flex PCB type construction) that you could definitely fit inside a closed NESE module.
What do you plug thoes into?
The easiest would be a multimeter set to resistance. The resistance varies with temperature, and you can just look at a table to find the corresponding temp for a given value.
You can also get dedicated thermometer modules that will read a thermistor like this and give you a direct temperature readout.
Our vescs and smart BMSs also have the ability to read them - That’s how motor and mosfet temp readings are done.
I am using this one.
How is the accuracy compared to the stock one that it comes with?