google overkill solar, its a better fork of the software. it should be one of the slide bars in there on the top.
cool, I didn’t know of a different app. This seems to work too, charge button is enabled… wondering what does “FET software locked” means…
i have no clue about this, im not that much of an electronics guy hahahha sorry to dissapoint. it seems like your discharge is locked though, possibly due to your temp sensor not being connected?
Yeah, having the temp sensors connected is one thing.
That FET locked is just from having charge and/or discharge functions disabled.
I think I figured it out. The stupid charge port has 3 pins and I think I connected the wrong negative when I made an adapter. Re-doing it now. Stand by
2 Likes
If you use some epoxy to cover the metal of the loopkey then it shouldn’t be an issue when rocks hit it. Honestly, I don’t think an uncoated loopkey will be at risk if a rock hit it, but better to add an extra layer of protection just to be safe.
I added epoxy to my loop key to make it easier to grab and pull out and also to hold a magnet in pace so I can attach the loop key to other surfaces to make sure I can’t loose it easily. I didn’t add a string to the loop key to make it easier to pull out since doing that would look bad and I didn’t add the loop key as an emergency fail safe anyway.
That is always the worst and it isn’t helped by the fact that some parts are made while disregarding the common convention of black being the negative side and red being the positive end
1 Like
It’s alive! For real this time 
Just had to swap the negative pins on the charge port.
Let’s see how long it takes. I’d assume the BMS since it’s LiFePo4, knows at what voltage will end charging.
Do these values look ok?
Is 3.5v really enough to call a cell charged? Shouldn’t this be a bit higher?
1 Like
They’re all within 0.1 v of each other so you should be good in terms of balancing. Although I’m not sure why the 3.343 group is red but then the 3.334 group is yellow 
Hopefully someone else with that same BMS can explain why. The voltage levels alone look perfectly fine to me though
The nominal voltage for that cell type is 3.2 volts but I have no idea what the fully charge voltage should be since I’ve not used them before. (The nominal voltage is always lower than the fully charged voltage. For 18650 LiIon batteries nominal is 3.6v but full charge is 4.2 v as an example )
3.65v should be the fully charged voltage for lifepo4. We’ll, I’ll leave this charging to see what it does when it get’s there.
We’ll prepare to move on to the ESC/motors and TX connection. Hopefully wheels spinning soon!
2 Likes
I’m glad you already know the fully charged voltage. I hope you can get everything working properly so it is usable again.
1 Like
Strangest thing… one cell group started getting charged faster and faster until it reached the overcharge limit protection and the BMS stopped charging. Good to know that works, but why the hecc did it do this. Haven’t touched it, didn’t even go near the thing for the past 30 mins…
1 Like
check if you didnt forget welds on a cell in that group maybe?
1 Like
It’s definitely not pure nickel, that is iron oxide imho and would explain why it welds better too as the steel has a higher resistance and therefore gets hotter at the same settings than the 99% nickel. I would re test the suspect strip but prep a little differently so make sure it is just a lower percentage and not plated. Take a piece and lay it over an edge and use a file or sander to cut it in half by thinning it out - this way when it corrodes it will indicate if it has layers of different material better and you can judge it accordingly. Heavily salt the water to speed things up. Hopefully it’ll just be impure and you can just lower your vesc settings 
This is a bad sign unfortunately, seems like one of the cells in a p group isn’t in the circuit 
seems like it charged twice as fast as the others? Definitely need to check which means opening up your beautifully wrapped pack imho.
A silver lining though is that the nickel that was so hard to weld can be stacked alternating with the higher iron content (or even if it is plated) to get better welds. Clean everything with 99% iso and have well washed hands when you’re assembling it and you can make sure it has the nice low resistance connections you are designing for.
This isn’t good news, from someone who has rebuilt the same pack 5 times to another i feel your pain. Imho redoing the series connections isn’t optional with these indicators, especially if you get strong indications of oxidation like in your pic or you find layering in a second test.
5 Likes
Indeed this was the obvious first conclusion but sadly it may be something else.
Did some localized surgery on the p-group in question.
- The group is the correct one for sure, it measures over 3.5v while the others are a bit lower.
- The parallel connection is solid. I wedged a plastic pry tool and started pulling on the strips. Nothing moving, no strip unstuck.
- Measured connectivity between the cell ends and it’s also good.
- Made a point to measure with sharp probes right on the cell body, not on the strips… still connection is good. Did this on both ends.
- After all this I plugged the charger back in and it’s the same, the voltage on this particular p-group immediately start going up fast. Dammit!
Can one of these two cells just be …bad?
Is there anything else that could make one group charge so fast?
Clearly I’ll have to take this half apart but if the strip connections are good, I’ll try not to break the whole thing apart, just to remove these two cells…
The more pain now, the more satisfaction when I finally get this damned thing right 
It could be one of the cells is bad but it just seems unlikely to me but I don’t know exactly why - just a hunch that it’s the nickel. Take the nickel off one side before disassembling the whole pack and check voltage again. Do you have any way to test the cell internal resistance? A known resistor and a multimeter that uses a 9v battery for power is better than one that only uses Aaa batteries.
You could charge/discharge the suspect p group cells individually and that would let you know if one or both of those cells is an outlier. I have to do discharge testing capacity and IR on all my cells before they go into a pack now because i use used/repurposed cells for my personal setups - no other way around it I’ve found that doesn’t involve headaches/heartaches lol
Good idea. I do have a smart balance charger I use with LiPos for RC stuff that measures internal IR while charging. For a quick check, I can connect it to half of the pack (it’s 6S max). I’ll do this shortly. On the other hand, this will connect through the nickel to the cells so I don’t know how relevant it will be.
Btw, I left the LLT balancer on overnight to keep doing its thing and now all the groups are at the same level again, around 3.30v
Yes, after the first check with the charger I will have to cut the strips off and check the cells in this p-group individually.
What’s a good way to discharge safely one single cell? Also, when do I stop, at what voltage I can consider it fully empty so I can note how much mAh goes back in?
Strange, it’s been charging for about 5 mins now and the voltages are still behaving.
IR also seems fine, A123 tech data shows 6mΩ and it’s close to what we’re seeing:
If it won’t start running away with this charger, could the LLT balancer be bad? I guess we can test, I can disable balancing, charge it up again with the boosted brick and monitor the cells.
No.2 is the p-group which was running fast.
Does your smart charger have a discharge mode? Should be able to jumper it in to the one p group with some alligator clips or something. Otherwise you could use a high watt resistor, i think i would use a 5w 3ohm would probably keep the current near an amp. Look up the cell spec sheet and use the lower current limit stated: Boosted Board V1 Revival - Battery Rebuild - #102 by Pecos. Maybe, and I only suggest this because the cells are lifepo, get a ride in to discharge again then check to see if the same thing happens on the next charge cycle?
How long did it take to fix that huge delta? might have jumped the gun if it is acting normally now. Definitely keep an eye on it and run some stress testing. Intermittent problems are the hardest to fix, hopefully it’s not the bms - it happens sometimes but isn’t often ime with the smart bms, I usually break them before they fail… unless its dally then i have a poison touch lol
It does have a discharge mode but I won’t get anywhere near 1 amp. It’s discharge capability is 8W max. Should be fine for testing now…
I don’t know how long it took to fix the large delta, I turned on the LLT balancer last night before going to bed and by morning all the cell groups were at the same voltage. Then I hooked up this charger in the morning and it charged them all up to 3.60v.
Nothing weird this time with group #2. It charged up in line with almost all the rest.
I say almost all because now I noticed something maybe strange with group #5. It got up in line with the others up to about 3.45 and then it stayed there. When the rest of the cells were at 3.6, group #5 was still around 3.4 and then the charger slowly balanced it up to 3.6v as well. As soon as it stopped charging, group #5 pretty quickly (within a couple mins) got down to 3.50. Should this be concerning or still “within spec”?
These are all the cells right after charging was complete:
At 0.3A a 6S pack will take around forever to discharge. I’ll stop it eventually, I have to leave from home later.
Setteling down a few hundredths of a volt is normal and expected. Make an adapter to plug in just the suspect p group via the balance leads if you don’t want to test the other p groups. The balance wires can easily take that kind of load
Check this discharge setup out, lol
The pack lead goes into a converter box I use for another purpose, it outputs 13v constant which goes through a power meter which goes to a 110v inverter which goes to a light for now. The pack balance lead goes into the little charger just so I can monitor the cells.
It’s drawing only 10W now mainly because I can’t find a bigger light or something else to plug in.
The plan is to discharge both 6S packs to 2.9v and then charge them up to see how much goes in and if all cells are behaving.
3 Likes