help troubleshooting molicel battery pack - Page 1
Forum section: electronics / beginners

author: Ehaze
author_rank: Contributor
timestamp: January 28, 2022, 04:57:58 am
content: I have two of thesehttps://jag35.com/collections/new-arrivals/products/new-power-cells-battery-pack-14-4v-4-1ahr-59whr-li-ionand I wanted to use them to power a bike light . I woke one up and it seemed to work just fine , read 15 ish volts and plugged into my light turned it on .Next day it was was reading only 1v , I tried to charge with a12v wall charger with no luck .Could anyone lend me some tips to fix it , there isnt much info to search and I still struggle with thesecracked it open and tested cells are reading normal volts !The pack seems good , b+ and b- tabs read 15.8 ish volts but the leads out only read 1.0 volts

author: Faringdon
author_rank: Super Contributor
timestamp: January 30, 2022, 12:53:32 am
content: Is this what you mean?.....On no load, the battery terminals read 15v, but the end of the loeads (which are presumably connected to the terminals) read 1v?That doesnt make sense, and if its the case, then there must be some current flowing through the leads and dropping the 14v....so there must be a closed circuit.Or are you saying that when you put the cells on load they read 1v?......if so, then i am afraid the cells are dead.

author: jerryk
author_rank: Regular Contributor
timestamp: January 30, 2022, 05:03:51 am
content: The four mosfets that you see in the video connect the ground terminal of the battery cells to the output teminals of the BMS. A flaw in the BMS is not activating those mosfets more than likely. A clear picture of the BMS board could be helpful. In the mean time start with gates of your power mosfets. Then work backwards to what drives them. Another failure point that I have seen on other BMS boards is failure in any liner regulators that supply the control circuitry scheme.Jerry

author: Ehaze
author_rank: Contributor
timestamp: January 31, 2022, 04:53:13 am
content: the B+ and B- tabs read 15. something volts , but the red and black leads out only read 1. .. Thing is all i really did was it up and it seemed to work like normal , its sold new and used and was reading 15v all the way , but next day it was only reading 1v at the leads out . I really dont even know where to turn , I could just break it down into cells , but I really wanted a cheap and easy battery pack

author: Ehaze
author_rank: Contributor
timestamp: January 31, 2022, 05:07:13 am
content: Im not sure how to check mosfets but Ill google it !

author: Ehaze
author_rank: Contributor
timestamp: January 31, 2022, 05:33:48 am
content: Ok I think 2 are shorted I get beeps on 2 but not the other two .

author: jerryk
author_rank: Regular Contributor
timestamp: January 31, 2022, 06:55:11 pm
content: Check F1 for continuity. It's a fuse of some type. Any repair is going to have it's difficulty and I'm not sure where you stand on that part. I doubt if your mosfets are shorted but if they are can you replace them?A clear understanding of how the mosfet gates are connected is important. Your photos do not show component numbers clearly but I'm sure you can see them. U1, Q4, Q5, and F1 components datasheets should be looked at to see how they are powered. It looks possible that there is conformal coating to contend with so make sure that's not an issue when you try to trace things. Be careful testing this under power. Test continuity by checking resistance and not with the continuity tester.If you are careful you should be able to find where the problem lies. Repairing it will depend on your experience. Finally when working and probing battery packs I like this keep in mind if you short things it can get ugly fast. I keep an ash bucket and fireproof gloves handy and have a "what if" plan in my mind.Best of luck.Jerry

author: Ehaze
author_rank: Contributor
timestamp: February 03, 2022, 02:22:20 am
content: ok thanks ... I checked it with my MM in diode mode ....... I think I may have damaged it when I tried to use my IFLY rc charger , I figured it would be OK , but it smoked and popped , and is now dead , maybe thats what damaged the BMS ?I barely have a soldering iron so I dont know if i can replace them .This pack was like 8 bucks from jag35 website, I have another one i can try, I was going to charge them with the smart charger that has a nice display, all i have now is a 12v wall charger !

author: Ehaze
author_rank: Contributor
timestamp: February 03, 2022, 04:24:19 am
content: also I really want to use these as packs , and not just break them down to make another pack , was wondering if you can recommend a BMS to just replace it ?

author: Ehaze
author_rank: Contributor
timestamp: February 04, 2022, 07:16:23 am
content: I think Im starting to get it lol , I need to hook up the charge cables to another plugs DOOH LOLOL!!!!