Review DALY BMS - Beware when buying!!! - 13S 48V 40A - See Images

MSG76

Pedelecer
Jun 29, 2020
30
6
Hi all,

bought a DALY BMS 13S, 48V, 40A, in May 2022. This is supposed to be shock proff and waterprooof. Installed it carefully on top of my pack, secure with velco and Kapton tape on all terminals. The Silverfish case it's sealed with Low Modules Neutral cure black silicone. All the details were carefully thought and calculated. Still, after 2 months the BMS has completely died.
See images for confirmation.
 

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Woosh

Trade Member
May 19, 2012
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I can see that your pack is carefully built, but without knowing the story behind it (was it a replacement, which controller you use) and whether the BMS has a soft switch, reverse current protection, charging current protection etc, it's difficult to guess why your BMS died. It could be overheating, problem with the charger etc. BTW, I don't know the maker so can't comment on their products but in general, BMSes are simple circuits, there is usually an explanation. For home build kits, it's best to have BMS with fuses, easier to fault find.
 

MSG76

Pedelecer
Jun 29, 2020
30
6
Hi, yes I understand your point. It's a new DiY battery build. For the cells used Molicel M35A which are very similar to the Samsung M35. Nickel strips were tested for pure nickel and doubled to allow 15A discharge all across. M35A's max discharge is 10A. Also, use a 48v charger rated at 1.5A
Processor is a KT17A with an AKM Q128C. Both front and rear lights add less than 1A draw. I have another post with the pcb light modification to allow both light to run from KTLCD3.
For the BMS I chose a separate charging port with temperature sensor to prevent overheat. No soft swicth. Specs are here: https://www.aliexpress.com/item/4000812224182.html?spm=a2g0o.order_list.0.0.4ce71802jWdUYq.
The charge/discharge cycles were very steady and reliable. I cycle about 20 miles, 5x a week, rain or shine. Charge on daily basis and do a 3 month full discharge/charge cycle regularly.
The P- port is fine. You can see it's the B- circuit that failed. It actually would come back to life once in a while and then fail again. It happened twice lat week while I was cycling and then one day half way throughout my commute just stopped and would turn on again. Last Friday, was able to get it to run for about 1km once I tried to switch bat on, while waiting on a red light. It turned on again, I was so happy! 1km after it died and then I started troubleshooting.
Checked every single point of the circuit for continuity, voltage and current. Even tested every little connector on Julet 1T5 cable for continuity. I though it could have been rain from previous KTLCD3 failure. But even that one I was able to ressurect with a hair dryer. Ever since I always keep working spares at home and always insulate PCB's with electrical insulating varnish.
I do these projects for the money saving, but mostly for the learning process and onwership of the gear. I know exactly what's running under the hood and why. And it's usually really cheap to source and replace if needed! I get a kick from streamline engineering and getting the most bang for the buck :D
Sometimes, there are disapointments of course... like this one
 
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Nealh

Esteemed Pedelecer
Aug 7, 2014
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I use Daly BMS and thus far not an issue, I have two 12s ones at the mo for my HG2 & P42a celled packs.
Like any BMS there is a likelihood of any small component part failing, might just be a bad batch.
 
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MSG76

Pedelecer
Jun 29, 2020
30
6
Yes, I think that may have been it. I was really looking forward for it to be super solid taking in account all the images of a test unit submerged in water and everything. I'm still going to plug an ISDT BAttAir plugin to the balance leads to see what info can I get from the cells. This will completely discard any doubts of cell failure causing it.