Ok, so you've 'bricked' your ebike battery - now what ?

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Deleted member 4210

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This season it seems I've taken a few more calls than usual from ebike purchasers that have found their batteries completely dead. And unable to charge them. And maybe only a season or two old.

This can happen when a ebike battery is unwittingly left sitting for a few months with a low charge or even no charge, and then the battery for various reasons won't charge or work again. (I'm not going to get into the technical reasons for it occurring here, as there is much debate, as it sometimes involves the BMS).

What are your options ?

1. Buy a new battery from the OEM - (ouch, if it's only a year or two old)

2. Take a risk and buy one from China via the typical platforms that offer that choice. (Might be more 'expensive' in the long run if you dont know for sure they are same quality and grade A cells, or marketed as such but not what you get. And you can't verify it, bc they are very good at putting them in the same OEM wrappers.)

3. Find a reputable battery rebuilder, who does this for a living, and may be able to retain your cells, and possibly even install a better BMS, or higher Density batteries.

4. Investigate the possibility of replacing the BMS, which if you are electronically inclined and do a lot of research first of how to videos, which can explore how to do some superficial testing, to see if a new BMS will resolve the issue. (I've tried this on a couple bricked batteries, and got the BMS from the original seller, but it dIdnt work. It was worth a shot, before going the route of one the other 3 options, since I was able to persuade them to send one free, except for shipping. The downside was waiting a long time - 6 to 8 weeks)

Not a great feeling to have this occur, since the battery is usually the most expensive single component on an ebike.

So make sure before you take that '3 month winter vacay' to Florida or Arizona, you have your battery charged at least 50% (but not 100%), and you will likely avoid turning your precious ebike battery into a useless brick. ;)
 

harryS

Well-Known Member
I'm surprised Battery University even alluded to waking up batteries. Appears that this is common practice amongst some lawn care operators, and there's a post in Endless SPhere where a guy posted pictures of the blisters on his arm after a battery blew up on him.

I recently found I had a bricked battery too. Apparently, it hadn't been used since last Fall and the BMS discharged the cells that power it. Three of the ten cell groups were completely flat lined, making them too risky to recharge. I will dispose of it.
 

rich c

Well-Known Member
Right or wrong, the subject of waking up a Li-ion battery appears quite often on the Sondors Facebook owners page. Often just running a jumper from another battery. I can't show a mathematical statistical analysis, but I've read of zero fires or explosions.
 

FlatSix911

Well-Known Member
Region
USA
City
Silicon Valley

This is a generally accepted industry practice and can be done safely... Ravi is the SME and can also weigh in on this.

I have had success restoring bricked batteries on various bikes and tools... take it to an expert if you are unsure. ;)


BU-808a: How to Awaken a Sleeping Li-ion
Learn what you can do to prevent a Li-ion battery to fall asleep.

Li-ion batteries contain a protection circuit that shields the battery against abuse. This important safeguard also turns the battery off and makes it unusable if over-discharged. Slipping into sleep mode can happen when storing a Li-ion pack in a discharged state for any length of time as self-discharge would gradually deplete the remaining charge. Depending on the manufacturer, the protection circuit of a Li-ion cuts off between 2.2 and 2.9V/cell. (See BU-802b: Elevated Self-discharge)

Some battery chargers and analyzers (including Cadex), feature a wake-up feature or “boost” to reactivate and recharge batteries that have fallen asleep. Without this provision, a charger renders these batteries unserviceable and the packs would be discarded. Boost applies a small charge current to activate the protection circuit and if a correct cell voltage can be reached, the charger starts a normal charge. Figure 1 illustrates the “boost” function graphically.

Sleep mode of a lithium-ion battery
Figure 1: Sleep mode of a lithium-ion battery.
Some over-discharged batteries can be “boosted” to life again.
Discard the pack if the voltage does not rise to a normal level within a minute while on boost.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
I haven't had this happen to a bike battery yet, but I have had it happen to nearly identical cells used in radio control. Picture a plane stuck in the top of a tree with the radio receiver impossible to turn off for several days... while you arrange for a tree climber to fetch it for you!

I have tried the wake up methods, which appeared fine to start with, but those cells never come back to 100%. Packs will eventually end up with cells so mis-matched the chargers are not able to match them properly, even though the chargers are WAY more sophisticated than what we use on the bikes.
 

Browneye

Well-Known Member
^^This. In my experience, if you brick them, they’re history. You’ve ruined the cells - they don’t come back from that, chemical degradation.
 

harryS

Well-Known Member
Agree. Go outside the manufacturers volatge range (2.5V -4.2V), they don't promise you anything but potential disaster if you try to re-use the cells. That's why the safety circuits bricked them,
 

Sierratim

Well-Known Member
Ebike batteries have significantly more stored energy than the cell phone batteries that some online examples point to for 'unbricking' stats. Unless you're willing to take more than reasonable safety precautions and have someskills in dealing with battery cells I'd advise against trying to salavage a bricked battery. If you want to proceed, search for this topic on other forums like Endless Sphere, et al.

Good luck, and stay safe.
 

J.R.

Well-Known Member
Not entirely related, he does "boost" a cell. The result reminds me that inside a multi cell pack we don't know what's going on with each individual cell when we charge. A novice boosting a sleeping, bricked or dead pack could result in big problems. I have 4 big packs in the house. As a novice I try to maintain them with best practices🙏

 

Thomas Jaszewski

Well-Known Member
^^This. In my experience, if you brick them, they’re history. You’ve ruined the cells - they don’t come back from that, chemical degradation.
Can be tested and confirmed if internal resistance is at a level for rehab. NEVER something I'd do for a customer. This battery repair stuff isn't for play. Lots of "Kentucky Fried Fingers" over the years. Watchband and finger rings can cause huge oozing burns! Little bombs some putting out 30A. It's not practical having a BMS replaced due to hazmat and shipping charges. I've suggested numerous times, that adding a BMS to a battery order is cheap insurance. NO WAITING for a part replacement.
 

AHicks

Well-Known Member
Region
USA
City
Snow Bird - Summer S.E. Michigan, Winter Gulf Coast North Central Fl.
Thomas, my experience has been that even if a cell is "rehabbed", even cycled a few times afterward, they aren't going to be around long before you start seeing issues - starting with a change in fully charged voltage levels used to balance charge.

Bottom line, from my experience with them anyway, they are no longer trustworthy and are generally a huge waste of time.
 

Thomas Jaszewski

Well-Known Member
Thomas, my experience has been that even if a cell is "rehabbed", even cycled a few times afterward, they aren't going to be around long before you start seeing issues - starting with a change in fully charged voltage levels used to balance charge.

Bottom line, from my experience with them anyway, they are no longer trustworthy and are generally a huge waste of time.
I have a couple of aging batteries. Real saggers and well worn. But the fellow I gave them to seldom rides faster than 10-12MPH and those old batts are pushing him around after 6 years of abuse. But agreed. Most here want full speed ahead and high amp demand really exposes a battery weakness.