Ugh... problems with a charger from china

[phorbin]

I purchased a duct tape 48V LiFePO4 20Ah battery from Cammy CC on eBay. I had some initial charger problems and she replaced the charger several times. I had a working charger and I was loving it. My electric bike was powering me up these steep hills in Pennsylvania. Then it rained for a week so I didn't ride and I left my battery off the charger. When then rain stopped I plugged back in the battery and it got a good 24 hour charge. When I plugged it into my bike the light on my controller came on for a second then went right out. I emailed Cammy and she told me to check the voltage of the battery and the charger. The battery was a steady 50 volts after a 24 hour charge and the charger was a steady 55 volts. She told me the charger should read 60 volts and the battery when fully charged should read just over 60 then drop down to 53 when fully charged. So it appears my charger isn't charging my battery fully. Is there anyway I can fix my charger or does anyone know where I can get a good charger for cheap? I have several of these lame-duck chargers and they all test at 55 volts. I need something that can put out the juice. These hills are killing me without the powered assist. Thanks.

 

[dnmun]

you need to measure the cell voltages from 1-16 first.

 

[recumbent]

Your charger should be out-puting at least 58 volts. Even at your 55V charge cycle your batteries should read higher, I think your batteries might need balancing.
However your batteries should rest (overnight off charger) at 53+ volts min, if charged properly.

Instead of always sending the charger back, open the sucker up and turn the adjusting screw clockwise a notch, check with volt meter until you get about 58 volts.

The folks that send batteries and chargers overseas are not all electricaly saavy.

If you don't know which adjusting screw to turn, just take a picture a we will help you f*ck it up

 

[317537]

Does this problem ring a bell?

Another member has the same problem and it is almost the same if not exactly the same as this members.

The charger wont go into full mode charge because the battery or BMS wont trip it, the battery seems to have some capacity but wont go very far and LVC is cutting out.


A well discharged 16 celll lifepo should read in the mid 40's volt area. What the hell is going on here.

 

[dnmun]

i think the pack is so far out of balance it won't charge because of the high cell shutting down the charge. if he will measure the cells we should be able to see how bad it is.

 

[317537]

This could be true.

However My SlA'S did this once a few month back when I switched to 48v and stuck a new battery into an old series. And the opposite happened. The charger didnt shut off and I woke up with one very hot battery. With my 48v SLA's, when one gets over charge its goes over the rated charge voltage then gets hot, works like a resistor in in the series and drops in voltage below 14v, then the string wont balance. The others sit at 15v and seem to not mind too much and conduct little power from the charger, however because the hot battery isnt getting over 14v the charger doesnt shut off.

Its both the BMS and cells then. The BMS wont balance, screws a couple of cells and the others start to follow suit because they over charge to keep charger happy in float mode.

If these were lipo's there would be a fire by now.

You're right. A full cell test is is in order and a repair of the BMS. This is even if there is a BMS. I think when I go Lifepo i will build my own pack so I can access the cells to test them. This problem should be rectified ASAP as the other cells are over charging now to compensate for the runt cells/s.

Adjusting the charger to put more volts into the pack could make things a lot worse. Half the cells could be still fine.

 

[phorbin]

Ok, I just got back from class and snapped a photo of my charger innards and tested the battery's voltage.
The battery has been off the charger for two days and it reads just under 50 volts. I have an analog multi-meter and the needle sits just under 50. It was reading exactly at 50 volts two days ago.
I'd rather not cut open my battery to measure the individual cells if I don't have to.
My charger is the same as Subfightr's. That post got really confusing and didn't seem to come to a conclusion.
Maybe I can have a more positive outcome because these steep hills are killing me.

 

[317537]

Nothing stands out to be wrong with this charger, it looks pretty solid to me. Looks can decieve. However if there is something wrong with it, it should show as at least one part that looks burnt or over heated.

Can you test your cells?

Can you show a picture of your pack so the experienced members here can instruct you as to how to test them?

 

[BLUESTREAK]

HI : If you need a good charger go to ( RECHARGEABLELITHIUMPOWER.COM) both my cammycc 48 volt chargers quit.

 

[Russell]

A well discharged 16 celll lifepo should read in the mid 40's volt area. What the hell is going on here.

The lowest resting voltage I've recorded for my 16 cell LiFePO4 48V battery has been 51.52V after I used 90% of the rated 10Ah capacity. The battery hit a Vmin of 43.31V under a 20A load near the end of that ride but the resting voltage remained high (unlike LiPo/LiMn).

-R

 

[recumbent]

i think the pack is so far out of balance it won't charge because of the high cell shutting down the charge. if he will measure the cells we should be able to see how bad it is.

Yep, that's most likely the problem, and it's easier to fix than you think.

First of all, your picture of the charger is perfect, but cannot see an adjustment for the voltage unfortunately.

"Bluestreak" is giving excellent info on purchasing a good charger from a great supplier (Andy) who knows his stuff around electronics at http://www.rechargeablelithiumpower.com

I got a charger from him called "Highpower" and works great and has two adjustment screws inside if needed (which you won't cause Andy will set it properly to begin with) Costs about $65 or so and is worth every penny. Order it today because winter is just around the corner.

I used to charge my 48V pack with a 55V charger for a couple weeks and worked fine, BTW.

You should ballance your cells before you damage them, all you need is a cell phone charger of 4-5 volts to boost the low cells, or drain the high cell that is tripping the BMS too soon, show us a pic of your pack.

 

[dnmun]

HI : If you need a good charger go to ( RECHARGEABLELITHIUMPOWER.COM) both my cammycc 48 volt chargers quit.

what happened to your chargers? did they function for awhile and then die or was it dead all along and never worked?

phorbin, you can measure the cell voltages on the sense wire plug in the BMS. don't short anything and get a decent voltmeter before you try. you can get digital voltmeters at harbor freight on their specials for $3.

 

[dogman dan]

I agree, you need to find the low cell group, by checking voltage along the bms sensor wires. Not sure which end you start at, but one voltmeter lead stays put on the end, and the others read each wire one by one. The voltage will add up, so you do some math to get the individual cell voltages. Find the low cell group and charge with a 3.5 or 4 volt power supply manualy. Then try the charger again.

Soneil sells 48v chargers that usually have the adjustable pot, but nowdays there are good charger suppliers.

Opening the pack is still a good idea though, you might have a bunch of popped spot welds in there. Continuing to ride with some cells out of the circuit will cause the whole cell group to get overdischarged to death.

 

[dnmun]

shorted out my voltmeter last night. i had two on the table and one was set up to measure the current out of the charger to the battery, and i also was measuring voltage, the leads are identical laying int he tangle of wires, so i picked up the wrong leads and put my ammeter across 40V of SLA. it did make a tiny noise and i wonderd why the voltage did not appear on the display of the voltmeter i was watching, the smell lingered.

and shorted the charging input on my e-bikekit.com lifepo4 pack when i tried to stuff the braided end of the charger output into the hole, just a quickie, did not even blow the 3A fuse but i got religon real fast when i thought of how expensive that could be. at least the voltmeter is only $3.

if you can't measure the voltages on all 16 cells with a digital voltmeter, not much we can do, BOL.

 

[phorbin]

The charger seemed to work at one time. The green led would go orange and the pack would power my bike. So I dunno what the deal is. Here are some pictures of my pack and BMS.
I can take more pics if needed just let me know what you need to see.
I dunno when I can make it out to Harbor Freight to pick up the cheap digital multi-meter. I wish I would have thought to go there before buying this cheap analog one from home depot.
I'm thinking I'll order that charger from www.rechargeablelithiumpower.com for $75 if you think that would help.

 

[dnmun]

i don't think it is a charger problem, said that initially. looks like your BMS has let teh pack go outa balance, we just don't know how bad it is. i think i have seen the BMS before because jim had a vpower battery, there are threads on the vpower problems, you can go read them.

if you can take the sense wire plug off the BMS you can measure the cell voltages, the cheap little digital voltmeters make it fast and easy to read. you can never have too many voltmeters because they all get ruined or lost.

 

[phorbin]

What do you mean sense wire? Can you point it out in my pictures. I'm kinda lost on exactly what I should be testing to check the cells voltage. I gotta head out to class now but I can try all this later tonight maybe. Thanks again. This board always comes through with the best advice!

 

[recumbent]

i don't think it is a charger problem, looks like your BMS has let teh pack go outa balance, we just don't know how bad it is.

if you can take the sense wire plug off the BMS you can measure the cell voltages, the cheap little digital voltmeters make it fast and easy to read.

Good point "dnmun", definately try testing the cells through the small senser wires instead of taking apart the battery pack, i never thought of that because my batteries are open to test.

One side (end) of the sensor (flat wire bundle) is ground, and all the rest are each of the batteries, you will know right away if one battery is too high (tripping your BMS too fast) or are too low causing it to trip the low voltage cut-out.

You might be able to drain, or charge the seperate cells through the same sensor wires also if you use low voltages. Good luck.

 

[dnmun]

the sense wires are tiny, if you discharge too much current they could get hot. or worse.

first we need to know the cell voltages, otherwise it is shooting in the dark. to evaluate we need to see each cell voltage, in sequence to guess about where to look and what could be going on.

 

[phorbin]

I think I know which wires are the sense wires but how do I test them. I labeled them as #1 in the picture. There are two sets of them each with their own plug. Is one set positive and the other negative or what is the deal?
Also with all this poking around I noticed that the wires going to the connector that connects the main red and black leads from the battery to the BMS were loose and just popped right out of the connector. I labeled that as #2. So I wonder if that was my problem all along that the connection was bad between the BMS and the battery. I got the connector apart but should I solder them back in to make sure it stays? Or just clamp it back it like it was? I don't have any classes tomorrow so I'm going to try to go out to Harbor Freight and get a digital multi-meter and solve this whole thing. I needs me some power!

 

[dnmun]

yes, 2 is bad, very bad. if you have a soldering iron and real 60/40 solder you can solder all the connectors, but not the sense wire plug. you can cut off that zip tie, and dig your BMS out of that tape too so we can look at it. but i bet you really only had a bad connection because the crimp was no good. they never are, you should always solder. in fact if it is permanent, solder all the connections except the main battery positive lead and put andersons on the positive lead for an emergency power disconnect.

get a soldering iron at harbor freight too if you don't have one, they may also have real 60/40 rosin core solder. zip ties, heat shrink, led lights, thick bike lock cables, but the voltmeters are normally like $4-5 and then on special they are always $2.99 or maybe $3.99 where you are. i just blew up another one in the period between my last post about how they get ruined. plus you need a real accurate and easy to read meter to maintain your ebike.

 

[recumbent]

Yep, Do what "Dnmun" says, might seem like lots of stuff and a big job at first, but it's all necesary and takes only a bit of time with great results.

We'll have you on the road shortly, and save your battery investment.

 

[dnmun]

the voltmeter i just blew up was new, it was just in the wrong place and i forgot that those leads were not the leads to my voltmeter. operator error, distracted driver.

well now i have an extra set of probe leads to replace the ones i cut off to mount the 3rd of my voltmeters on brandon's bike.

 

[phorbin]

Finally made it out to the store. About to start re-soldering the connections and hooking it all up right!

I took a picture of the BMS board where the sense wire plug connects to it. Let me know if you need some other angle or what. I need to know how to measure the individual cell voltage through the sense wire.
Cool.

 

[dnmun]

ok, i have seen these yellow BMS with the black potting compound on one of jim's packs. his was 12S, and i think it came from lau chan, or he is called 'gamershopping' now. i think they all buy their stuff from the same sources in china.

i thought the BMS looked well built and you can see how the shunts are laid out on the mother board. you have 2 of the 8S BMS in series mounted together to make it 16S.

you can measure the voltage on the end of those surface mount shunt resistors with the sense wires plugged in or just measure them on the sense wire plug. be careful not to short them out by allowing your voltmeter probes to contact each other while measuring the adjacent pins on the plug.

can you tell which one goes to the top of your battery and which goes to the bottom? just measure them and record the voltages. #1 is the lowest, #16 is the highest.

for your cables you can take the brass connector out of the plug by bending the little 'ear' that holds it in the plug back into the connector since it is soft. use a little screwdriver to reach all the way down to the ear. or if you have some tiny long nosed pliers then you can stick one edge of the pliers under the ear and bend it away from the plastic. don't break the ear because you have to bend it back out when you remount your connector into the plastic plug.

that wire may take more heat than your soldering iron can muster so you can help it with a cigarette lighter but don't get the cable all sooted up with the lighter, try heating the soldering iron below the tip along the neck of the iron with the lighter, maybe you need an extra set of hands too. hehe.

shoulda told you to get one of those 'helping hands' setups with the alligator clips and the magnifier. they are a good deal too $2.99 on special. but good solder makes all the difference, because it will flow at lower temperatures. and rosin core flux.