Help: is my lifepo4 battery dead?

[luvxu]

Hi all,
A couple of years ago, I bought a 48V 10Ah lifepo4 battery like this one http://www.alibaba.com/product-gs/56710 ... _10Ah.html . I use it once in a while to run my boat's trolling motor. It was working fine the last time that I used it. Then I stored it away for about 6 months over the winter . Now it is completely dead and I have no idea why/how. It show 0V on the voltmeter and I cannot charge it at all. There is no light, no indication that it is still alive. I have been reading a fair bit about this lithium battery technology over the last few days and I wonder if there is any way that I could tell if the batter is completely dead or that I just need to replace some parts, e.g., the BMS?

Thank you for any pointer that you can give.

PS.I am able to verify that the charger is working fine on another battery so the problem is with the battery itself, not the charger.

[dogman]

That eliminates the usual problem, simply a broken plug on the charger. But there is still the possiblity of the plug broken on the battery side.

Most likely the long term storage without disconnecting the bms or recharging the battery regularly has led to the bms discharging one or two cells. The BMS runs on less than pack voltage, and over a few months can discharge the cells it runs on.

You will need to acess the battery before the bms, and get voltmeter readings on each cell. Usually you can do that by unplugging the bms, and then probing at the plug contacts. Move the probes down the row, getting a voltage on each of the cells.

Likely you will have to replace the dead cells to fix it. But you can try to use a cell phone power supply to bring the low cells up, if they are not at zero. Once up to 3v or so, the bms may then allow the battery to charge.

[neptronix]

Probably overdischarged itself. I bet the shitty China seller didn't warn you about that did they?

[Ykick]

Reputable sellers of these batteries will warn leaving the battery sitting for more than a month or so can/will damage the pack. I've got 2qty similar packs and I always hit em with a charger once a month without fail. If not, as DM described, the BMS will drain the cells to nothing and leave little chance of recovery after much effort opening the pack to gain access to cells, etc.

[luvxu]

I have learned so much about battery lately. Never know that leaving a battery out for a long time would kill it. I used to think that the less you use it the better it would be

I opened the metal container and it seems that all the cells are glued to the aluminum case by silicon. That will make it so hard to get them out intact.

[dnmun]

actually the lifepo4 cells will hold their charge for years. but you left the BMS connected while uncharged and the BMS has drained all the charge out of the pack.

can you take pictures of the BMS and where the sense wire plugs in? you want to measure voltages while it is on the charger.

[luvxu]

I thought that these batteries (http://www.alibaba.com/product-gs/56710 ... _10Ah.html) has a build in BMS. Wouldn't it? I do not have a separate BMS to use with these batteries. All that I have is a charger that would connect to a charging port on the battery. The battery also have a status check button where it would display a line of led light to signify the battery strength.

Again, I don't have to use a separate BMS to charge or discharge the battery.

[Ykick]

I thought that these batteries (http://www.alibaba.com/product-gs/56710 ... _10Ah.html) has a build in BMS. Wouldn't it? I do not have a separate BMS to use with these batteries. All that I have is a charger that would connect to a charging port on the battery. The battery also have a status check button where it would display a line of led light to signify the battery strength.

Again, I don't have to use a separate BMS to charge or discharge the battery.

The BMS is built-in and always ON which is the problem. If opening up the pack and disconnecting the BMS is too much trouble for storage longer than 30 days then you must charge every month or so. If not, you will most likely kill the cells.

My packs are 2 years old and still deliver 90% original capacity but I've charged them every 30 days whether used or not.

[dogman]

Very unfortunate that nobody seems to warn the buyers that the bms they build into the battery will ruin the battery if stored for very long. They may have stated that the battery should be charged if stored long, but never said why. This knowledge will become common some day, but at the price of lots of people learning it the hard way as you just did.

Very difficult to dissasemble those metal boxed batteries enough to diagnose them too. Like lots of modern stuff, "no user servicable parts inside". Could have been before they went crazy with the hot glue.

At this point though, you have two options, trash can or have a go at finding the bms and the wires to the battery cells buried in all that glue. Chances are, replacemet cells will be difficult to obtain, your time is worth money, etc. Unless you dig taking stuff apart like we do, just getting out the credit card and buying a new pack might be your best bet.

[t3sla]

Bet you $5 there is a sticker on there that says charge once every three months.

[SamTexas]

I just revived a lifepo4 battery similar to yours. It was a "relatively" simple task. No glue. Just 8 screws, a large blue shrinkwrap tube, and a thin layer of clear scotch tape. "Relatively" simple because I'm experienced and knew what I was looking for.

In my case, the battery was left alone long enough to create an imbalance large enough to prevent the BMS from rebalancing it. But not long enough to leave any permanent damage. So all I had to do after opening it up was to individually bring up the low voltage cells. That made the BMS happy and everything was back to "normal" (BMSs, as currently designed, are the most poorly conceived/designed circuit in my opinion).

If you're willing and patient, and if you possess some basic knowledge about DC voltage and current, you can probably fix it. You will certainly get all the help you need from this forum. It's not rocket science, but it does take a good amount of time especially if this is your first exposure/experience. Good luck.

[dogman]

Yes, and nothing to lose by trying at this point except time.

If you don't have a cell in there below 2v by much, it is likely to be able to be balanced and put back in service. But that is if you can get it out of the can without damage. Some have tried with other types of packs, and peeling the battery covers caused even more damage. Depends on how crazy they got with the hot glue.

But if you have the time, and get into it like we do, go for it.

[luvxu]

I will try to get all the eight screws out and see if I can remove the battery cells. I'll take pictures and post them so that other newbies who ran into similar situation will know what to do. I am electronically and mechanically inclined so I think I can give it a try. You are right, I have nothing to lose at this point.

[SamTexas]

These are the pictures I took when I opened up mine. Yours should be very similar.

Top end

Bottom end (1)

Bottom end (2) with the 4 screws holding power connectors removed

Slide battery toward the top end

Cut open the blue shrink tube wrap

Now you have full access to every cell and the BMS

[luvxu]

the pictures are so helpful. Thank you very much. Now I know what to look for. This is going to be my weekend project I think.

SamTexas: when your BMS didn't charge, was you able to detect any life from the battery at all? did you see any led light up when you check for the battery level? In my case I don't see anything at all. It was just like the battery is completely dead.

[SamTexas]

the pictures are so helpful. Thank you very much. Now I know what to look for. This is going to be my weekend project I think.

You are welcome. Good luck on your project. You'll have fun either way.

[dnmun]

it will only take 5 minutes to get it open, and measure the voltages on the cells. write down the voltages initially, then put it on the charger and record the voltages as it charges. you want to identify any cell that charges up faster than the others so pay attention and measure them all often and record the voltages as it charges. then you can graph the results and see which one charges up fastest.

[SamTexas]

it will only take 5 minutes to get it open, and measure the voltages on the cells.

Are you kidding? I took me 2 hours to do it. But I was extra careful and did not have any pictures to look at ahead of time.

[SamTexas]

SamTexas: when your BMS didn't charge, was you able to detect any life from the battery at all? did you see any led light up when you check for the battery level? In my case I don't see anything at all. It was just like the battery is completely dead.

There are 4 LEDs. Only the red LED lit up before the fix. After the fix, the three green LEDs lights up when full, and the red LED is not lit. Looks like (not 100% sure) that the red LED is lit only when the BMS thinks it's in trouble.

The pack voltage can always be measured from the 3 pin charging port (only 2 pins are used). Before the fix, the voltage at the charging port was 37V (max voltage is 42V for my 12s pack.)

[dnmun]

oh sam, i thought we finally got him to open it and you are spooking him, 2 hours and it will be solved.

really do not worry, you can take it apart and look inside without any problems.

it is easy really, get cordless screwdriver, set in reverse, 8 screws, zipzipzipzip , pull the end out and one end has to fold over to clear the inside of the tube, then slide the entire pack out the other end

flip it face down on the sense wires, take scissors and just run it up the blue shrink on the side facing up while the pack is laying on the carpet, from bottom to top, the sense wires are on the other side so no risk to the wires,

now unfold the sleeve, take off the plastic shields on the end where the terminal are exposed and put the voltmeter probes on each terminal of each cell, record and now you have got the info we need to figure out if it is dead.

[SamTexas]

oh sam, i thought we finally got him to open it ...

Sorry. My bad. Plus I was using a regular hand screwdriver

[dogman]

Good on ya for providing those pictures. You should get on the wiki and put them up there too. "how to diagnose a 36v 10 ah metal cased battery"

[SamTexas]

Good on ya for providing those pictures. You should get on the wiki and put them up there too. "how to diagnose a 36v 10 ah metal cased battery"

I can't. Mine is a 38.4V, 8.7Ah.

[dogman]

Well, just saying that was a great set of pics, and many could make use of them if they could be found again easily.

Many of us ES regulars haven't bought batteries of that type since we tend to be hot rodders. But we'll see more guys with one that is not working, just like we have with other types.

So whatever that pack is called, a wiki entry would be a good thing. Or just a thread with a title appropriate to making it easier to find in a search.

[SamTexas]

Well, just saying that was a great set of pics, and many could make use of them if they could be found again easily.

Many of us ES regulars haven't bought batteries of that type since we tend to be hot rodders. But we'll see more guys with one that is not working, just like we have with other types.

So whatever that pack is called, a wiki entry would be a good thing. Or just a thread with a title appropriate to making it easier to find in a search.

I know. Just pulling your legs.