Lifepo4 fully discharged... can it be revived?

Batteries, Chargers, and Battery Management Systems.
Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 10 2017 9:52pm

Hi All,

Apologies up front for a basic question....

I have Lifepo4 48V EBay special that powers my home made ebike.

6 months ago I stopped using the bike and now I went to charge it at its nominal 60V and it is not retaining its charge at all.
I read somewhere that if the cells fall below 2.6v then it's not wise to try and recover the battery cells.

The battery has been connected to the bike for all this time draining. Yes I know this is a stupid rookie mistake but I guess I am wondering if there is a recommended fix. There is a built in BMS and I am looking for guidance before I start to break into the blue shrink wrap.

Any advice would be appreciated even if it is 'go but a new one'.

Thanks in advance Chris.

User avatar
amberwolf   100 GW

100 GW
Posts: 25097
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Lifepo4 fully discharged... can it be revived?

Post by amberwolf » Feb 11 2017 1:21am

This particular chemistry in general is "less likely" to burst into flame because of the problem you've got, but none are immune to it, so be aware of that first.

Next, it is possible (likely) that whichever cells went too low will have either (or both) lower capacity than before, and less current delivery capability (more voltage sag under load), compared to how they were before.


If you're willing to accept that, and still want to try reviving it, you'll need to open it up far enough to reach the BMS and it's wires that run to each cell. At the connector on the BMS you can measure with a voltmeter from the main negative output to the first pin on that multiwire connector, then from that first pin to the next one, and so on until you get to the last pin, and measure from that to the main positive output wire.

Write down all those voltages in that order, and you'll have a list of the cells in the pack.

Probably it's just whichever cells are used to power the BMS (usualy the first few), so you can then manually charge each of those, slowly, until they match the other cells.

This can be done with a "lab PSU", which has both adjsutable voltage, and adjustable current limit. This is an easy way to be able to charge single cells of any chemistry, or even the whole pack if you get a PSU that has a maximum voltage high enough to do that. It can also be used for troubleshooting other electrical things, including ebike stuff like hall sensors or throttles, etc.

Or you can use a single-cell LiFePO4 charger, but most of the ones I ahve seen arent' adjustable, so those will simply fully charge a single cell as fast as they can. If you want to be gentle to the cells that are too low, this probably wont' do that.


There's other ways, too, if you look around at posts that mention single cell charging or charger.



Once youve got all the cells about the same voltage, and above whatever the BMS cutoff is, you can then just run the regular charger to fill up the pack, and then test it to see if it still does what you need it to do.

If it doesn't, you could replace the cells that were run too low, and probably fix it, or you can replace the whole pack.

Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Re: Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 11 2017 2:11am

Hi Amberwolf,

Thanks for the reply. I don't have a lab PSU but I know what you mean.

I appreciate the info, I will attempt a revival based on your post.

User avatar
Sunder   100 MW

100 MW
Posts: 2646
Joined: Sep 06 2011 11:24pm
Location: Sydney, Australia

Re: Lifepo4 fully discharged... can it be revived?

Post by Sunder » Feb 11 2017 3:57am

If you don't have a lab PSU, but have a computer PSU, there's three voltage "rails" you can draw off inside - 12, 5v, and 3.3v. The 12v rail is always yellow, the 5v rail is always red, and the 3.3v rail is always orange. Doesn't matter which ground (black) you use, they're all common.

You can use the 3.3v rail to bring each individual cell up to the "right" voltage. The 3.3v rail typically has a lot of current behind it, so you can quickly charge even fairly large capacity cells.

If you're real brave, once the current starts dropping, you could even use the 5v rail to bring the cell voltage to 3.7v. Just make sure you don't leave that unattended. While LiFePo4 can cop some over-voltage, 5v is way too much, and you're already dealing with compromised cells.
eBike: Q100H on 16S with Phaserunner FOC Controller
eMotorscooter: Vectrix VX-1 on 36S
eCar: Mitsubishi Outlander PHEV... Waiting for warranty to expire
eHouse: Still on grid, but with LTO batteries and 3kw LF inverter...

After 5 builds, the best advice I can give, is start with high quality products. I prefer http://www.ebikes.ca

Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Re: Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 11 2017 6:03am

Thanks Sunder. I think I have a computer PSU somewhere. Otherwise it's $75 for a bench PSU that would be handy to have around.

I am wondering if the battery pack is worth reviving as it's very heavy at 4.5kg. The bike handles poorly with that weight on the back. I realise it's always a compromise between weight and power.

I upgraded my controller to peak at 40A output. I was thinking I could get a smaller capacity cylinder type battery that mounts on the bike frame not pannier.

You mention the battery cells are already compromised so I guess I won't be achieving high current at maximum voltage?

Thanks for your input.

User avatar
kneedeep   100 W

100 W
Posts: 236
Joined: Jan 24 2017 1:59am
Location: Ontario Canada

Re: Lifepo4 fully discharged... can it be revived?

Post by kneedeep » Feb 11 2017 10:17am

These are a great investment in EV life, under $40 on ebay. I have used NiCd setting to revive cells then switch to the balance charge LiFe.
Attachments
IMG_5025.JPG
IMG_5025.JPG (62.45 KiB) Viewed 1361 times
Chinese Ebay build in progress https://endless-sphere.com/forums/viewt ... 12&t=86149 , been through half a dozen scooter ebikes..No More of those.

I like to build it better than I can buy it. I like to think outside the box...Come to think of it where is that box?

User avatar
amberwolf   100 GW

100 GW
Posts: 25097
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Lifepo4 fully discharged... can it be revived?

Post by amberwolf » Feb 11 2017 3:05pm

One thing to keep in mind about any of the charging methods that don't let you reduce the current to something low (in the 100-200mA range probably) is that the (much) higher charging currents could be beyond what the compromised cells can handle, resulting in further problems (or worse).

Some of them (like teh computer PSUs) can often provide currents (far) beyond what even a normal cell is spec'd to be charged at.

As for weight and handling, the best bet is to not put that weight on teh tail, but put it in the middle of the bike (triangle, etc), or move it to a side pannier, even if it is all on one side, then if it is down low around the axle it is still easier to ride with than up high over the rear wheel.

Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Re: Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 11 2017 8:32pm

Thanks again guys, all good information.
This is my first and only ebike.(so far) It's a mid drive mounted on a Giant NRS X3 full suspension bike. The battery is so big and heavy the rear rack was the only option.
I thought if I build my own battery I can design the arrangement to fit within the limited triangle space and hence lower on the frame and part of the bike.

I looked on eBay for a generic cylinder type battery, I am looking at around A$300 for a 48v 10aH.

Still not 100% sure about attempting a revival as it's cost of trickle charger / bench supply, time, compromised cells and a potential fire risk hazard vs A$300 or whatever the cost and time to build my own pack.

Thanks again for your support.

999zip999   100 GW

100 GW
Posts: 8345
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Lifepo4 fully discharged... can it be revived?

Post by 999zip999 » Feb 11 2017 10:05pm

Get to the cells and write down first. Free to look.
1. 2.85v
2. 3.25v
3. 2.98v


16. Xxx volt
I have 4 voltpheks lifepo4 single cell that stop at 3.65v @ 2amp which is to high a charge rate if below 2.8v a cell phone charger can work. But even thou printed on side says 5v 200mah TEST as it could be 7volt. Seat and watch if going to the bathroom unplug. Only seat and watch.
When you look for a small battery for a 40amp controller you most buy name brand and the quality ones. Samsung 25r or ? Get ones over rated for your needs. Lots of crap out there. Ask first.
Last edited by 999zip999 on Feb 12 2017 12:24am, edited 2 times in total.

User avatar
fechter   100 GW

100 GW
Posts: 12886
Joined: Dec 31 2006 3:23pm
Location: California Bay Area, USA

Re: Lifepo4 fully discharged... can it be revived?

Post by fechter » Feb 11 2017 10:12pm

You don't have much to lose by taking apart the pack and see if you can measure the individual cell voltages. If any cell is too low, the BMS will prevent any output. You might just have one low cell that's tripping the BMS.

Even if you get a new pack, it's nice to have a spare one that works.
"One test is worth a thousand opinions"

Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Re: Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 12 2017 4:18am

Yes nothing to lose but some danger.

New development. I attached some SLA's that I was given and found that any load over 20A throws the drive chain on my mid drive. It has done this since I upgraded my controller and the drive cog became loose. I tightened it but it still throws the chain??

It's pointless having a battery if the bike regularly throws the chain.
1st priority, fix the chain and utilise the SLA's

2nd revive the LifePo even if used as a spare.

I will keep you posted, thanks for your advice.

User avatar
izzzzzz6   100 µW

100 µW
Posts: 8
Joined: May 29 2009 8:50am

Re: Lifepo4 fully discharged... can it be revived?

Post by izzzzzz6 » Feb 12 2017 4:30am

Sometimes cells can be revived but once they drop below the saftey voltage you must revive them with very low amounts of power until they reach the safety voltage. So you need a way to limit the current until this voltage is reached. A BMS helps to balance the cells and you might find one in the battery but they can also be bought seperatly online. They are also in balance chargers but most chargers don't balance above 8S perhaps 10S. Some do only 4S balancing. By buying a BMS of your choice, with a little skill you can build cells up into a battery with a voltage of your choice.
As to weather the old battery can hold it's voltage or be any good at storing power? You will just have to test it. There might be some good cells inside worth salvaging. If you have lots of time you can build up a collection of similar good cells and use them in future projects. Lead Acid are heavy and don't suit that many E-Bike enthusiasts. But i know a few people who use them, ok in trikes and the like.

User avatar
amberwolf   100 GW

100 GW
Posts: 25097
Joined: Aug 17 2009 6:43am
Location: Phoenix, AZ, USA, Earth, Sol, Local Bubble, Orion Arm, Milky Way, Local Group
Contact:

Re: Lifepo4 fully discharged... can it be revived?

Post by amberwolf » Feb 12 2017 1:02pm

Charlie_Echo_Foxtrot wrote: any load over 20A throws the drive chain on my mid drive. It has done this since I upgraded my controller and the drive cog became loose. I tightened it but it still throws the chain??
Perhaps you should post up your build and details, so the builders with experience in such things can help you with that, too. ;)

User avatar
kneedeep   100 W

100 W
Posts: 236
Joined: Jan 24 2017 1:59am
Location: Ontario Canada

Re: Lifepo4 fully discharged... can it be revived?

Post by kneedeep » Feb 14 2017 12:19pm

If you do go back to working on the battery buy a digital volt meter from local hardware or auto parts $20 or less, valuable tool and check each bms lead for specific pack voltage. Your thread reminded me of a pack I had go bad so I worked on it on my build thread and it will be revived. as for your chain please post lots of detailed pics and give us a better idea of your situation. More details = more help.
Chinese Ebay build in progress https://endless-sphere.com/forums/viewt ... 12&t=86149 , been through half a dozen scooter ebikes..No More of those.

I like to build it better than I can buy it. I like to think outside the box...Come to think of it where is that box?

Charlie_Echo_Foxtrot   10 µW

10 µW
Posts: 6
Joined: Jun 22 2015 3:58am

Re: Lifepo4 fully discharged... can it be revived?

Post by Charlie_Echo_Foxtrot » Feb 17 2017 8:44am

Thanks Kneedeep.
I am sure someone will have a chain shedding issue with their EBay belt drive system.

I will post pictures......

User avatar
edrift.eu   1 W

1 W
Posts: 59
Joined: Sep 16 2013 1:04pm

Re: Lifepo4 fully discharged... can it be revived?

Post by edrift.eu » Mar 18 2017 1:12am

I have revived a few 100 LIFEPO4 cells. Measure them at millivolt to get more accurate info. In my opionion cells that are less then 0,5V are not worth reviving, But cells above 1V can often have 70-90% of its original capacity! USE them NIMH setting on the charger and charge up to 2V then switch to LIFE.

Raisedeyebrows   1 kW

1 kW
Posts: 390
Joined: May 13 2017 1:39pm
Location: Oregon/South Point Hawaii USA back and forth

Re: Lifepo4 fully discharged... can it be revived?

Post by Raisedeyebrows » Mar 10 2018 11:10pm

I have been reading some older threads pertaining to Lifepo4 batteries as I know next to nothing about them. I have a 36v 8ah battery in one of those Silverfish cans, the thing only wants to take a charge to about 38.7v, the pack is pretty old, 5+ yrs old, motor is supposedly 260 watt geared hubmotor is shutting down when riding up hills so I'll guess the pack can't put out enough amps any more to ride anything but flat ground. Rode it across town and back this afternoon and it shut down about mile 6-7 or so, even pedaling the whole time on flat ground. This is on a folding bike and due to it being a geared hub motor it rides real good with the motor off so getting back home was no problem, only walk of shame was a couple hills right below home base. Battery showed 36.1v when I got home.

I opened the case up in an attempt to pull things out, inspect things and maybe check the cell voltages, everything is packed in there beyond tightly, foam rubbery stuff holding the cells in really firmly so it's going to take some force to dislodge things. Curious if I should try to rebuild the pack using the BMS with new Lifepo4 cells adding some more capacity, what would my options be for doing that?

This isn't a performance bike, just want to be able to cruise with a light bit of assist and some help up the hills, the bike is my Clark Kent mild mannered normal ebiker bike, kind of fun to get on the bike path and ride alongside the Pedego People once in a while, nobody even notices me.
Yuba Mundo w/BBSHD
Specialized Hard Rock w/9c clone, statoraid, hubsink
Trek Fuel 90 w/BBSHD
Above all run on 14s4p 52v li-ion
Ecobike folder 36v
Currie Flyer scooter 24v on 24ah of SLA

Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

999zip999   100 GW

100 GW
Posts: 8345
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Lifepo4 fully discharged... can it be revived?

Post by 999zip999 » Mar 11 2018 12:58am

You need to know the state of charge of your battery. A 36 volt battery lifepo4 has 12 groups of cells . You start by knowing the voltage of each cell group 1 through 12. You need to write them down on a piece of paper this is a must like this.
1. 3.33v
2. 3.40v
3. 2.98v

12. Xxx volt
This can be checked at the sense wires going to the BMS starting at the negative end as number one. No need to take battery out of the case at this time. You do need a multimeter. Free at Harbor Freight with coupon if you buy zip ties for $2 or razor blades $1.

Raisedeyebrows   1 kW

1 kW
Posts: 390
Joined: May 13 2017 1:39pm
Location: Oregon/South Point Hawaii USA back and forth

Re: Lifepo4 fully discharged... can it be revived?

Post by Raisedeyebrows » Mar 11 2018 2:03am

999zip999 wrote:
Mar 11 2018 12:58am
You need to know the state of charge of your battery. A 36 volt battery lifepo4 has 12 groups of cells . You start by knowing the voltage of each cell group 1 through 12. You need to write them down on a piece of paper this is a must like this.
1. 3.33v
2. 3.40v
3. 2.98v

12. Xxx volt
This can be checked at the sense wires going to the BMS starting at the negative end as number one. No need to take battery out of the case at this time. You do need a multimeter. Free at Harbor Freight with coupon if you buy zip ties for $2 or razor blades $1.
Yes testing the individual cell voltages was my goal when I opened the case, I'll try to post a photo tomorrow of what it looks like, Seems like they did a pretty fair job of trying to prevent trying to repair it and I didn't want to get too rough trying to pop it open to access the wires to the BMS without seeking some guidance.
Yuba Mundo w/BBSHD
Specialized Hard Rock w/9c clone, statoraid, hubsink
Trek Fuel 90 w/BBSHD
Above all run on 14s4p 52v li-ion
Ecobike folder 36v
Currie Flyer scooter 24v on 24ah of SLA

Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

SlowCo   10 kW

10 kW
Posts: 912
Joined: Jan 05 2015 5:43pm
Location: The Netherlands

Re: Lifepo4 fully discharged... can it be revived?

Post by SlowCo » Mar 11 2018 5:46am

Subscribing for the info as I also have an old LiFePo4 pack.

999zip999   100 GW

100 GW
Posts: 8345
Joined: Jan 10 2010 1:40pm
Location: Dana Point So. Cal

Re: Lifepo4 fully discharged... can it be revived?

Post by 999zip999 » Mar 11 2018 11:38am

The bms is at one end usually with a white plug that have 12 or 13 wires depending on the BMS. If 13 wires the first wire is negative.

Raisedeyebrows   1 kW

1 kW
Posts: 390
Joined: May 13 2017 1:39pm
Location: Oregon/South Point Hawaii USA back and forth

Re: Lifepo4 fully discharged... can it be revived?

Post by Raisedeyebrows » Mar 11 2018 12:24pm

Reading after being on charger all night 38.9v
Image
Opened up case by removing screws and pulling plastic ends off, top end
Image
Bottom end
Image
Pulled insulating sheet back on bottom
Image
Yuba Mundo w/BBSHD
Specialized Hard Rock w/9c clone, statoraid, hubsink
Trek Fuel 90 w/BBSHD
Above all run on 14s4p 52v li-ion
Ecobike folder 36v
Currie Flyer scooter 24v on 24ah of SLA

Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

Raisedeyebrows   1 kW

1 kW
Posts: 390
Joined: May 13 2017 1:39pm
Location: Oregon/South Point Hawaii USA back and forth

Re: Lifepo4 fully discharged... can it be revived?

Post by Raisedeyebrows » Mar 11 2018 12:31pm

Pulling the insulating sheet back on the top end I see 3 screws holding what appears to be a BMS, will be loosening the screws next.
Image
Last edited by Raisedeyebrows on Mar 11 2018 1:39pm, edited 1 time in total.
Yuba Mundo w/BBSHD
Specialized Hard Rock w/9c clone, statoraid, hubsink
Trek Fuel 90 w/BBSHD
Above all run on 14s4p 52v li-ion
Ecobike folder 36v
Currie Flyer scooter 24v on 24ah of SLA

Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

ThierryGTLTS   100 mW

100 mW
Posts: 45
Joined: Jan 10 2017 8:10am

Re: Lifepo4 fully discharged... can it be revived?

Post by ThierryGTLTS » Mar 11 2018 12:41pm

edrift.eu wrote:
Mar 18 2017 1:12am
I have revived a few 100 LIFEPO4 cells. Measure them at millivolt to get more accurate info. In my opionion cells that are less then 0,5V are not worth reviving, But cells above 1V can often have 70-90% of its original capacity! USE them NIMH setting on the charger and charge up to 2V then switch to LIFE.
A123 says in one technical doc that 0.5V is the absolute minimum voltage for their LiFePO4.

So, what you say seems to be good.

Thierry

Raisedeyebrows   1 kW

1 kW
Posts: 390
Joined: May 13 2017 1:39pm
Location: Oregon/South Point Hawaii USA back and forth

Re: Lifepo4 fully discharged... can it be revived?

Post by Raisedeyebrows » Mar 11 2018 1:41pm

After screws were loosened I was able to pull the BMS forward disconnecting the pins. I count 12 pins on the plug.
Image
Yuba Mundo w/BBSHD
Specialized Hard Rock w/9c clone, statoraid, hubsink
Trek Fuel 90 w/BBSHD
Above all run on 14s4p 52v li-ion
Ecobike folder 36v
Currie Flyer scooter 24v on 24ah of SLA

Every trip made with electric bike is one less car trip, saves money, no toxic fumes, less noise, less impact on roads.

Post Reply