Rad battery BMS replacement

[DickB]

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.

[DickB]

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

[MikeC]

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...

[DickB]

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.

[MikeC]

That fixed it. Thanks for that and all the knowledge sharing you do.

[james2022Radwagon4]

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!

[Si1Dia]

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

[DickB]

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?

[satsujinsha]

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!

[DickB]

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.

[satsujinsha]

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?

[DickB]

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?

[inoxa]

check youtube for testing cell and charging.  there are some good videos there.

[satsujinsha]

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 ) ----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 :-)

[satsujinsha]

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.