Troubleshooting suggestions? duct-tape lifepo4s from ebay supplier

[rguy56]

OOO...I paid a fortune for these things. Two-48v. 20ah lifepo4s in a leap of faith. EBay...from a guy who claims he's located in a few different countries (It was not a long term seller, but the feedback was good).

It took them a looooonng time to show up, but now I have two fairly heavy, very very expensive, non functioning batteries. $1800!!

My 48v SLA batteries, with much lower amps, work very well with the setup I have, and they actrually have a greater voltage indicated by multimeter. but I didn't leave well enough alone, and bought the new batteries.

Is there anything that I can check before I try to get the seller to exchange them, or whatever? I'm not even sure that it's technically safe to ship these things in a charged state.

 

[mark2yahu]

I learned my lesson a long time ago, never to buy from out of the country except of course, Great Britain, Oz, and Canada.

 

[rguy56]

Unfortunately...

Suppliers on ebay have started to say they're located in "more legitimate" countries than the ones they're really from!!!

 

[mark2yahu]

Same with buyers. When I used to sell stuff on ebay, I didn't want the hassles involved with shipping overseas...and hassles with rude u.s. postal workers. I'd block the foreign buyers, but they'd sign up saying they live in the u.s. And then I find out I have to ship to some **** hole outside of the country. I stopped selling on ebay because ebay won't do anything about it.

 

[Peter]

$900 for a 48v20 ebay battery, ouch.

Define non functioning. Any voltage available on the battery leads. Charger voltage ? Do you have a pic of the battery and the BMS

Who was the seller, a link to another of their auctions would be really handy.

 

[rguy56]

Pictures of suspect batteries

I don't really want to damage the pouch the BMS system came in to photograph it. Can I just pull the multipin connector out of the side and slide the BMS out? I don't want to cut anything in case the seller claims I was messing with it...

The connections are straightforward and obvious. In addition each battery has an obvious charging connection. After lengthy charging, one battery shows 48.3v. and the other 51.3v. Somehow, they just don't function under load...Absolutely nothing... I looked through the yellow pages, and I don't even see anyone who seems to be expert on lifepo4.

I honestly don't want to link to his ebay auctions here because I don't want to drag his name through the mud in case he comes through for me... for good or ill, though the name the seller is using is JimmyWuu. I hope at the end of all this I can be praising him for coming through with service!

 

[Peter]

Have a look at gently sliding the BMS out after disconnecting the balance plug. I don't think you will get either of them out without damaging the heatshrink, so go easy on them.

The 51.3 seems right for voltage, the 48.3 seems a bit low especially after a day on charge. Have you checked the output voltage of the chargers ?

Where are you measuring the battery voltage ? From what I can see you have a separate pair of wires for both charge and discharge (A little unusual, but not a problem) Test the battery voltage across both charge and discharge.

To me, getting zero current from the discharge wires is pointing toward blown fets on the BMS though I am suprised you have the identical problem with both.

You really need to get in contact with Jimmy and let him know you are having problems. If he is unhelpful there are other places you can get replacement BMS's, but let's worry about that if the time comes.

You are unlikely to find anybody in the yellowpages who knows much about LifePo's and even less likely to find somebody who will work on a chinese battery that they did not design / build / sell .

 

[rguy56]

Thanks Peter. I had been testing the voltage from the charging connection, and it never occurred to me that it might be different from the power wires. It also didn't occur to me to check the output of the charger.

I agree that it's unusual to have problems with both batteries, especially since the two look different (from the same supplier). That makes me wonder if they are from two different builders. Seeing what I have, though, of Chinese quality control, I don't think the odds of two seperately bad batteries are nearly as small as winning a lottery, and people do win those... I'm sure the supplier feels the same way, as I've contacted him and so far have gotten nowhere. His statement is that if I get 48v., then the battery is good. That simple.

I'll check the things you suggest, and post a photo of the bms unveiled presuming I can extract it safely.

Thanks again for your suggestions.

Bob

 

[Peter]

I'm sure the supplier feels the same way, as I've contacted him and so far have gotten nowhere. His statement is that if I get 48v., then the battery is good. That simple.

That's carp, it is disappointing to hear of such lousy customer service. It sux for you but hopefully other people won't make the same mistake.

Having said that, at least now you know there probably isn't much in the way of real warranty support so we can get serious about troubleshooting.

For a bit of background info and apologies if this is suck eggs. The charge wires are usually connected directly to the battery terminals. Charger output voltage should be around 58 volts. The fine wires to the multi pin connector are connected to each of the +/- junctions. These wires are used to balance the cells during charging.

The + discharge wire is usually connected to the + battery terminal. The - discharge runs through a fet on the BMS. The FET is controlled by the protection circuitry of the BMS. Low voltage protection and usually over current protection. All the voltage sense wires must be connected otherwise the undervolt protection curcuitry thinks the disconnected junction is at 0 volts and will trigger the fet to open circuit to protect the battery

Unlike most of the other non lithium chemistries, LiFePO's _Will Not_ survive being over discharged (A123's are a special case, but they don't like it either)

 

[rguy56]

Thanks Peter. Now my brain hurts.

I think you're right about the warranty. The seller just keeps going round and round and round. I think I just have to accept that.

So, I'll have to try to make the most I can out of these paperweights...

Bob