This post applies to the batteries on the Rad 5 and other models using the same battery.
I just finished repairing a Rad battery by replacing its faulty BMS with an aftermarket one.
A Facebook member sent me a battery that had failed with less than 200 miles on it. He had opened it up and observed condensation (despite the battery not having gotten wet) and apparent damage to the BMS circuit board. I offered to take a look at it.
There was indeed damage on both the top and bottom surfaces of the BMS circuit board. The cells looked fine and all were nearly fully charged. This was not too surprising. Battery failures are much more likely to be due to bad connectors, wiring, or switch than bad cells. If you have a battery that has failed completely to work or charge, as opposed to working but with limited range, odds are the cells are fine. Especially one with so little use as this.
Rad does not sell components such as the BMS for their batteries. Fortunately, aftermarket BMSs are available. I found a suitable replacement at greenbikekit.com for $26 plus shipping. It is much more cost- and time-effective to replace a BMS rather than troubleshoot and repair a BMS, as BMS components are surface mount (very tiny solder connections) and some components (such as the BMS chip) difficult to source.
Repair involves removing the faulty BMS, reconnecting a handful of wires (some of which require extension) to the new BMS, and making connections to each individual group of cells. The Rad BMS circuit board spans the entire top of the cell holder, making clean connections to the individual cell groups. The aftermarket BMS does require several more wire connections than does the Rad BMS. I spent a couple three hours at this, and could probably do it faster if there is a next time.
I will run his battery through a few cycles to make sure it is working well before returning it, but so far so good.
I will be providing more details on this repair.
This is a more detailed description of how I replaced a bad BMS in a Standard Rad battery to repair it. It includes a description of what a BMS (Battery Management System) is, how it works, and the steps that I took to diagnose the problem and make the repair. It includes many photos and diagrams.
https://drive.google.com/file/d/1-9bUGDBFqdNPqgnswibiYNudZBWNLvUC/view?usp=sharing
edit: updated broken link
It could be me, or my cellphone, because we're camping in hinterlands. But the link doesn't work for me. The Google drive message says it's in the trash, and details about the file say the public can't download it...
Quote from: MikeC on January 01, 2022, 03:08:47 PM
It could be me, or my cellphone, because we're camping in hinterlands. But the link doesn't work for me. The Google drive message says it's in the trash, and details about the file say the public can't download it...
Sorry - try again; I updated the link.
That fixed it. Thanks for that and all the knowledge sharing you do.
Hi, my battery recently died and I wonder if I am also having a BMS failure issue. I was wondering how you went about finding the replacement BMS, because I cannot seem to find the same one in Switzerland. If the specs are the same (13s, 48v, 25 a, and assuming it is the same physical size or smaller), is that enough, or do I need to search for something else? I am searching Amazon France and Germany, by the way. Thanks!
Quote from: james2022Radwagon4 on November 11, 2022, 06:50:01 AM
Hi, my battery recently died and I wonder if I am also having a BMS failure issue. I was wondering how you went about finding the replacement BMS, because I cannot seem to find the same one in Switzerland. If the specs are the same (13s, 48v, 25 a, and assuming it is the same physical size or smaller), is that enough, or do I need to search for something else? I am searching Amazon France and Germany, by the way. Thanks!
According to the guide that DickB made, this is where he got the BMS. I have also gotten them from here:
https://www.greenbikekit.com/e-bike-lithium-battery/pcm-bms/48v-25a-13s-hailong-03-tigershark-new-polly-battery-bms.html
Quote from: james2022Radwagon4 on November 11, 2022, 06:50:01 AM
Hi, my battery recently died and I wonder if I am also having a BMS failure issue. I was wondering how you went about finding the replacement BMS, because I cannot seem to find the same one in Switzerland. If the specs are the same (13s, 48v, 25 a, and assuming it is the same physical size or smaller), is that enough, or do I need to search for something else? I am searching Amazon France and Germany, by the way. Thanks!
What are your symptoms? Have you checked all cell voltages?
Thanks so much for your awesome walk-thru on drive.
I believe I have a BMS issue described here: https://www.radowners.com/index.php/topic,9624.0.html#msg23799 described
I've just ordered the controller you mentioned from green bike kit..... wish me luck!
Quote from: satsujinsha on October 04, 2023, 07:23:28 PM
Thanks so much for your awesome walk-thru on drive.
I believe I have a BMS issue described here: https://www.radowners.com/index.php/topic,9624.0.html#msg23799 described
I've just ordered the controller you mentioned from green bike kit..... wish me luck!
A faulty cell can give the impression that the BMS is bad. You should measure the voltage of each cell group before replacing the BMS.
Finally getting around to poking at this. Looks like all the cell groups are registering zero (or, more accurately per attachment, between 30-1800mV) volts. I wonder if this is because I've left the key in the on/lock-engaged mode and the batteries might have trickled out?
The replacement BMS has arrived, but I'd like to dive into the battery-group voltage issue.
* Does anyone have any suggestions for troubleshooting zero voltage?
* Is there a way - or is it even wise - to charge the battery groups one-by-one and see if any of the cell groups are damaged? Would this introduce a threat of unbalanced groups?
Quote from: satsujinsha on October 22, 2023, 02:48:52 PM
Finally getting around to poking at this. Looks like all the cell groups are registering zero (or, more accurately per attachment, between 30-1800mV) volts. I wonder if this is because I've left the key in the on/lock-engaged mode and the batteries might have trickled out?
The replacement BMS has arrived, but I'd like to dive into the battery-group voltage issue.
* Does anyone have any suggestions for troubleshooting zero voltage?
* Is there a way - or is it even wise - to charge the battery groups one-by-one and see if any of the cell groups are damaged? Would this introduce a threat of unbalanced groups?
First, does the battery not charge?
check youtube for testing cell and charging. there are some good videos there.
DickB: Correct, the battery will not charge - with the charger, through the charging port. I tried some other troubleshooting steps as well and posted it here: https://www.radowners.com/index.php/topic,9624.0.html#msg23799. Sorry for hijacking this thread - happy to continue here or in the other (and grateful for all ur thoughts!)
Inoxa - I've spent some time on youtube: This is the closest I've got -https://www.youtube.com/watch?v=hv1DXRRmqB8. He is testing through a BMS connector cable. Attached is me performing - what I believe to be - the same test for the RAD BMS. As I mentioned there is ~0volts when measured at the tabs. Somehow my google-fu is failing me (there's a lot of videos out there, struggling to piece together enough tidbits from the different videos. Sifted through 100 videos of 'change the fuse' etc :P) ----Really hate to ask, but if you have any links describing testing the cells (in some way other than I have done at the top tabs) *and any links that show how to try bypassing the BMS to charge (if that is what you are suggesting I might try) I would be super grateful.
Thanks again folks - I obviously have alot to learn and really appreciate your time/thoughts :-)
Since I have the new BMS I may just go ahead and replace it. See if I can then use the charge port.
I can't find anything on bypassing BMS to charge battery pack cell groups (or individual cells) - seems like to do that I'd have to disconnect the tabs anyway.
With the cells that low, I don't know if a BMS is going to allow charging. You can try trickle charging individual cell groups through the tabs. Using the Rad charger and a 1K ohm resistor would charge a cell group at about 50 mA.
Quote from: satsujinsha on October 25, 2023, 04:31:04 AM
Since I have the new BMS I may just go ahead and replace it. See if I can then use the charge port.
I can't find anything on bypassing BMS to charge battery pack cell groups (or individual cells) - seems like to do that I'd have to disconnect the tabs anyway.
That's what I understand to test the cells individually you have to remove them and try to charge them on a special charger. Sorry I don't have specific videos. I have been down several youtube trips. When you find one then you have a hard time finding it again.
Inoxa - ahhh thx gotit. Now that I understand you were suggesting to tear it down far enough to remove individual battery cells, I'm sure I can find something (with some searching). First, Im going to try DickB's suggestion to charge at the tabs.
DickB - I ordered some parts - a female 5.5 x 2.1mm DC charging port and a 1k ohm resister. Once that arrives I'll piece it together. Once assembled I'll post a pic of both the charging circuit with the resister *and a pic of the tabs across which I believe I should charge. If you'd help validate my plan at that time (before I do anything stupid) I'd be grateful. Prolly be a cpl days.
Really cannot overstate my appreciation. Thanks again to you both!
Quote from: satsujinsha on October 26, 2023, 07:00:31 PM
Inoxa - ahhh thx gotit. Now that I understand you were suggesting to tear it down far enough to remove individual battery cells, I'm sure I can find something (with some searching). First, Im going to try DickB's suggestion to charge at the tabs.
DickB - I ordered some parts - a female 5.5 x 2.1mm DC charging port and a 1k ohm resister. Once that arrives I'll piece it together. Once assembled I'll post a pic of both the charging circuit with the resister *and a pic of the tabs across which I believe I should charge. If you'd help validate my plan at that time (before I do anything stupid) I'd be grateful. Prolly be a cpl days.
Really cannot overstate my appreciation. Thanks again to you both!
Just be sure to get the polarity right. Monitor voltage on the individual cell groups when charging. At trickle charge it will take quite a while to charge. If you don't see an increase in voltage after 15 minutes, one or more cells in the group is likely bad. If you see an immediate jump to 3V or more, one or more cells in the group is likely bad. I would stop trickle charging at about 3V and move on to the next cell group. Accidently shorting a charged cell group will yield bad results, so take care. Take advice on this at your own risk.
Sorry for the delayed update - life keeps interfering with my goal of messin' around with this battery. I have installed the new BMS and it is a little warm (in the area highlighted in attached screenshot). Is this something I should be concerned about?
TL;DR
I Trickle charged the cells from the tabs - they seemed to be fine - and so I installed the new BMI. The new BMI is a bit warm still, after 12+ hours. My initial thought was that the BMI might be balancing the batteries - so I waited ~12hrs thinking it might complete the balance and cool down. Alas, the BMI is still warm, hence the question.
Any thoughts on why the BMI would be warm without any load and no charger plugged in?
Also, Any suggestions as to next steps? I'm thinking I will:
1. Let it sit for another 24 hours and see if it's still warm.
2. try charging after 24 hours - see what happens.
3. test output voltage ---see if the same problem (~21 volts instead of 48) presents.
....i meant to attach a .png to previous comment, but it appears I cannot delete or modify the comment. I've attached the screenshot with a highlight outlining the warm area.