Can anyone identify what might be wrong with my batteries?

kchxaz · July 12, 2020, 12:42am

I know this is a long question but the circumstances warrant it, I figure the more details (some probably even unnecessary) the more someone might be able to help March 2019 I bought two 12s5p batteries from Matrix. They use Samsung 30Q I believe (if not that 30C?). Had the dimensions custom spec’d into: battery one is completely flat with the BMS at one end making the battery a whopping 640mm long was originally intended for a drop down but that deck snapped, so I only put like 15 cycles on it before shelving it for 9mo and only using it three of four times in that times frame. BTW, don’t ever get a pack that long, it is near impossible to find a deck that it will fit under and even then your VESC needs to go elsewhere. Battery two is a nested double stack with the BMS at one end as with the first. That pack I used many, many times over the past 9mo, couldn’t even tell you the number of cycles but you can tell it’s aging as it doesn’t get the range it used to.

Both batteries had issues within the first month, both having gone “dead” due to a wire deep in the pack coming loose from the solder spot. So I soldered the wire back on and sealed it back up with heat shrink. USed the one battery , as I said, many times, and the other not so much. After breaking down my old board which was cracking I moved everything to a new deck and at the same time upgraded the motors. Along with the very inconsistent FlipShit VESC I have the setup ran fine for a couple days, then day before yesterday (while using battery 1 - the one not used very much and fresh off a charge) the damn thing just goes dead with no warning what so ever. Usually the board would start to lag power and get sluggish is how I could tell it was dying but I could count on one hands how many times that happened as I usually kept track of miles traveled and would charge it when the time drew close, trying my best to err on the side of caution - except those handful of times.

The following applies to both batteries currently, with only very slight variation, which is weird for them both to have the same problem when one is very heavily used and the other is brand new in comparison. Now when the board died suddenly the remote was flashing at me as if it lost contact, so I assume the VESC shut off - which didn’t make sense, the battery was pretty fresh. Now, the same thing happened with battery number two the night before but I never looked into it, I assumed it was because the battery was older so without thinking I replaced it with the other newer battery. Then after only one miles it died also. When I start troubleshooting it I find that the xt90 plugs have voltage. The charging leads have the same voltage. Now here is the strange shit I don’t get AT ALL. Battery 1, when I measured the voltage last night it was at ~47V. Later on after I tried to to power on the VESC which did nothing in response, not even an LED lit up. However I know the VESC works because I hooked up a 12V lead acid and the VESC powered on. Satisfied I immediately turned it off.

Ok, the battery voltage was 47V why didn’t it power on? I recheck the voltage and it reads~32V WTF!? In 10 minutes time and having tried to power on the VESC for less than 10 seconds the voltage now reads ~32V at the xt90 AND at the charging leads. When I try to charge with either a 1.5A or a 3.0A charger, nothing happens, the chargers will not turn on, they act as if it’s full or not plugged in. At this point I am pissed beyond belief and give up for the night lest I trash everything in reach.

This morning/afternoon, I check the voltages. Voltage is back up to ~44V. WTF? I check the other older battery, it is only at 37V, it hasn’t changed significantly but then again I haven’t been messing with that battery much. Immediately feeling the frustration returning I try the 1.5A charger: Battery one will not charge at all. Battery two will charge with a “teeter-totter” effect. That is, it will charge for three or fours seconds and turn off for one second. It will repeat this for about 15-30 minutes and then turn off completely, and I know sure as shit the battery isn’t anywhere close to charged. It still will not turn on the VESC, nor charge. In case it wasn’t clear, the newer battery charged fine the day before (1.5A charger) but then after it died suddenly it no longer charges at all.

Now I don’t even know what to do or where to turn. I’m considering trashing the motherfucker and getting out of esk8. I have loved the hobby intensely the past 2.5 years and still do but this is really getting fucking old… I’m so fucking mad with the problems with the FlipShit VESC and now this with the batteries. Does everything that comes out of China eat shit like this? Why have I been able to build four boards now successfully and now I can’t troubleshoot a god damned thing to save my life?

Anyone have any ideas why I am having such intermittent issues on something that shouldn’t be an issue to begin with? If nothing else why won’t the fucking thing charge? Should I try charging through the xt90 plug? Do I need to tear the batteries apart again and look for broken wires - which makes no sense because the leads all show the same voltage, I mean - what the fuck, seriously…?

Sorry for the rant guys, it’s just I’m at my wits end and don’t want to throw in the towel just quite yet but I don’t want to destroy the fucking thing either which IS going to happen if I can’t keep my cool.

ZachTetra · July 12, 2020, 12:48am

Pics of the internals? Sounds like a nickel connection ate shit or the BMS died. I can try to salvage the cells and rebuild them if you need

J0ker · July 12, 2020, 12:50am

Can we get a TL:DR?

Flasher · July 12, 2020, 12:53am

2 battery packs with different ages and use cycles.
Only 2 common denominators

the bms is the same on both and has come from a bad batch
the battery builder cut corners or wasn’t attentive enough to every detail and did the same mistake on both

Check if changing the bms does anything. If not you have a weld/solder problem

kchxaz · July 12, 2020, 2:10am

@ZachTetra - I don’t have the batteries broken down at the moment. That’s a step I only want to undertake if I have too. Taking the shrink wrap and the cardboard (whatever that stuff is called) off always makes my butthole pucker. I’ve shorted a charge port checking voltage a while back and it scared the shit out of me, was not expecting that.

@J0ker - Sorry, not as up to speed on abbreviations all that well, what is TL:DR?

@Flasher - I initially thought this too but the intermittent fact leaves me still puzzled. Is changing the BMS a difficult thing to do? I’m pretty good with soldering and understanding positive and negative as well as basic concepts but am by no means an electrical engineer. Could a semi-noob do this or is this something for like zach?

And to top it off and make me look like a complete effin retard, I flipped the older battery over and for shits and giggles plugged in the 3A charger (which I dislike because I’m not usually in a rush but more so the higher amps degrade the overall battery life significantly - but for one charge wtf, right?), and voila the battery is charging full steam ahead…knock on wood. I don’t dare touch it for the time being since who knows if it will begin to charge again…

ZachTetra · July 12, 2020, 2:18am

Gonna be honest my guy, there isn’t much we can do for you without more detailed information…i.e. pictures of the innards. If you don’t want to tear into it you can try and find someone local to take a peek, where are you located?

TL:DR stands for ‘too long, didn’t read’…basically your post has more text than us goldfish can slog through in a single go

If you have worked with batteries before than replacing the BMS isn’t hard, if you don’t understand them it can be very intimidating. The balance leads should be an easy swap as the connector is ‘standard’ but the B-, C-, and possibly P- leads are all soldered so you will need to fix them without letting them short out. There is a chance you can skip replacing the whole thing, there are 2 ways to wire a BMS; bypass lets current flow to the ESC without passing through the BMS, discharge routes all the power through the BMS via the negative line to regulate the battery. If the BMS is wired for discharge, you can redo it to be bypass by cutting the P- line and soldering it into the B- port

If the battery does not charge consistently I wouldn’t fuck with it…its a sign that something got busted and it could let out the magic smoke any second

Edit: looks like Kerry is an Arizonian…who else comes from that desert? Maybe you’re local to these guys?

kadeanderson
nomadic_myke
Gamer43

Flasher · July 12, 2020, 2:20am

Tldr is “too long, didn’t read” he wanted an abbreviated version of the story

Changing a bms is a noob level process. Just make sure you’re connecting the wires to the correct places and that the wires of the new bms go to the same connections.

EDIT: just thought of this. Try a charge/discharge with the bms bypassed. Solder 2 new leads on the battery and connect directly to the esc. That should tell you if the bms is the cause of all this

kchxaz · July 12, 2020, 7:44pm

I’ll give that a shot. BMS’s don’t appear to be too expensive from Amazon. Think I’ll pick on up before I begin surgery. Is there a brand or preferred model to look for when replacing one in our application (or one’s I should avoid)?

Soflo · July 12, 2020, 7:55pm

I’d guess you have a bad series connection

Flasher · July 12, 2020, 8:06pm

Try to look for those that have the balancing feature (some apparently don’t)
Personally, I swear only by LLT bms. It’s the original smart bms with a UART port connected to a Bluetooth module. You can connect your phone to it and see in realtime what’s happening with your battery.
It’s what helped me find out I had bad solder joints

kchxaz · July 12, 2020, 8:24pm

@Soflo - I actually had thought of that, the jumping from 47V to 42V to 37V up and down had pointed me that way. I didn’t want to mention that in my OP and then find out I was wrong, I mean it could be the BMS after all but the 5V jumping in voltage with no use in between was hinting at that I think. But, since I have to tear down the battery anyways I can check into that at the same time…

@Flasher - That’s a sweet looking app. Kinda like the VESC tool one but that one only measures overall voltage I believe. Hell, I think since I’m really left with no choice than to tear down the battery anyways, I’ll replace the BMS with one of those while I’m at it and at the same time look for any broken 12s cell leads (or any leads at all).

Batteries, for as critical and sensitive as they can be, are still fairly simple in concept and functionality. Not a great number of things that can go wrong with them, that’s within our control anyways. They either have sufficient potential energy stored in them for the task at hand or they do not and they are either connected to a completed circuit or they are not.

kchxaz · July 29, 2020, 10:33pm

@Flasher

Ok, so my LLT BMS showed up today

I count 11 white wires including the red positive lead to make the 12s config. I’m hoping it won’t be too difficult to just replace the wires one by one as I remove the old BMS.

On the left of the device there is a bundle of 4 wires terminating into what I assume to be the Bluetooth transmitter device. Then on the right side of the BMS there are two black wires that terminate into themselves. Are these thermocouple resistance leads to measure temperature, perhaps?

Lastly, there is the black box that I ordered with the BMS. I think this was for communicating with the PC maybe? I wasn’t sure if I needed it since I can use my phone to communicate through the app w the BMS but I went ahead and grabbed it anyways. Better to have it and not need it then need it and have to wait another three weeks and pay the shipping chargers all over again. You know how it is.

I should be able to get this swapped out fairly easily don’t you think?