My 36V vpower battery does not charge.

[dnmun]

you can test the charging mosfet to see if it is turned on.

there is a picture of the bottom of the BMS where you can see the underside where the mosfets are soldered into the pcb.

in the lower right corner there is one mosfet by itself that has that orange rectangle that has just one leg of the mosfet in the corner. that leg is the gate leg of the charging mosfet. the leg on the other side of the mosfet, far left in that picture is the source leg. put the black probe on the source leg and the red probe on the gate leg and measure the voltage using the 20V DC scale.

 

[anders8899]

Can you still return the battery or get your money back??

No, I actually bought it used from a "craigslist" guy :/

you can test the charging mosfet to see if it is turned on.

there is a picture of the bottom of the BMS where you can see the underside where the mosfets are soldered into the pcb.

in the lower right corner there is one mosfet by itself that has that orange rectangle that has just one leg of the mosfet in the corner. that leg is the gate leg of the charging mosfet. the leg on the other side of the mosfet, far left in that picture is the source leg. put the black probe on the source leg and the red probe on the gate leg and measure the voltage using the 20V DC scale.

Thanks for the tips Jason! The measurement shows 15.46V while charging, and the other mosfets measured in the same fashion show around the same voltage, (decreasing slightly to 15.1V).

This is how I measured:

 

[skeetab5780]

I remember when I had one of those batteries, I replaced my SLA with a 48v 10ah Vpower and thought it was the best thing in the world. It didn't take long to wear it out though, It seems like the BMS just sucks and the cells are always out of balance, even if u left it plugged in forever charging.

If I had one of those today I would remove the BMS and add some new balance leads to the 18650's and charge with a balance charger.

be ready to get covered in cardboard/duct tape and hot glue if you tear it apart

 

[dnmun]

since the mosfet has voltage on the gate, it should be turned on so the pack should charge. so now it is a problem of finding the open wire in the charging circuit.

somewhere between the inside of the charger over to the positive terminal of the battery for the red wire, and from the charger to the source leg of that charging mosfet, either one of those wires is open.

it could be the plug where you soldered the wire back onto the pin. the pin and plug may not make good contact inside when pushed together so the current path is open.

you can check that by plugging the charger plug into the socket and measure continuity from the spot on the socket where you soldered over to the charger wires inside the charger, which is the only place the wire is exposed. don't power up the charger to test this. it is just the plug from the charger to the battery we are interested in.

so take off the cover of the charger and look for the spot where the wires are soldered onto the pcb. when you find those spots we can measure the continuity from the charger to the back side of the socket where you soldered it together.

but you have to be sure you are measuring continuity on the same wire. if you make a mistake and try to measure continuity with the ohmeter across the full pack voltage it will damage the meter so you first have to check with the voltmeter to be sure you are on the same wire.

so use the voltmeter first, measure the voltage between the + spot on the pcb and the place on that socket that goes to the positive terminal of the battery. if it is the same wire it will measure 0V. so when you know there is no voltage, measure the resistance across the contact with the ohmeter. that is called checking continuity and you are just establishing whether there is a good electrical contact across the plug.

do that for both wires, check voltage first then continuity across the plug. which is where i think the open circuit is. but there may be a break in the wire somewhere else too.

 

[anders8899]

I remember when I had one of those batteries, I replaced my SLA with a 48v 10ah Vpower and thought it was the best thing in the world. It didn't take long to wear it out though, It seems like the BMS just sucks and the cells are always out of balance, even if u left it plugged in forever charging.

If I had one of those today I would remove the BMS and add some new balance leads to the 18650's and charge with a balance charger.

be ready to get covered in cardboard/duct tape and hot glue if you tear it apart

I will try to look at that alternative if I conclude that my current setup is irreparable and if I can afford it. But having a lot of 18650's would complicate charging, since I will commute and therefore need very easy setup at my charger at home.

since the mosfet has voltage on the gate, it should be turned on so the pack should charge. so now it is a problem of finding the open wire in the charging circuit.

somewhere between the inside of the charger over to the positive terminal of the battery for the red wire, and from the charger to the source leg of that charging mosfet, either one of those wires is open.

it could be the plug where you soldered the wire back onto the pin. the pin and plug may not make good contact inside when pushed together so the current path is open.

you can check that by plugging the charger plug into the socket and measure continuity from the spot on the socket where you soldered over to the charger wires inside the charger, which is the only place the wire is exposed. don't power up the charger to test this. it is just the plug from the charger to the battery we are interested in.

so take off the cover of the charger and look for the spot where the wires are soldered onto the pcb. when you find those spots we can measure the continuity from the charger to the back side of the socket where you soldered it together.

but you have to be sure you are measuring continuity on the same wire. if you make a mistake and try to measure continuity with the ohmeter across the full pack voltage it will damage the meter so you first have to check with the voltmeter to be sure you are on the same wire.

so use the voltmeter first, measure the voltage between the + spot on the pcb and the place on that socket that goes to the positive terminal of the battery. if it is the same wire it will measure 0V. so when you know there is no voltage, measure the resistance across the contact with the ohmeter. that is called checking continuity and you are just establishing whether there is a good electrical contact across the plug.

do that for both wires, check voltage first then continuity across the plug. which is where i think the open circuit is. but there may be a break in the wire somewhere else too.

How can the circuit be open if I can get the bike running as long as the charger is connected?
And I have also tried to connect the charger to the battery directly, verifying that there is a charge.

What has happened twice is that I charged the battery and when I turn on the bike, then the backlight just momentarily switches on before the battery dies and no more power is given. This indicates that every charging attempt charges the battery a tiny bit, which shows that the circuits are not open but rather that there is something wrong with the battery.

My next step is to take the battery to a friend's workshop and go over each cell, and the charger with a lot more tools than I have at my apartment at the moment, I will measure voltage and current on each cell and also put some load on the stuff.

Regards,

 

[agniusm]

Whats rhe voltage on individual cells like?

 

[anders8899]

Hello again,

Its spring time here up in the northern europe and I have been working on the bike to see whats wrong.

I disassembled the pack and saw that there was a short-circut on a row of cells and one cell with a bad/loosened welding. I also confirmed that one of the rows do not take any current from the charger.

Counting up and measuring I counted that I would need 20 new cells. What I would need help with is to know which type it is, and where I can buy some that preferably ships to Europe? Spotwelding is too expensive so I will try to use a soldering gun and the help of a soldering-expert friend to get the new cells back on.

Here are some pics from the day's operation.
View attachment 4View attachment 2View attachment 1

 

[skeetab5780]

losing a cell group like that is very common. Especially since the builders used 2 wide of a tab/strip and no insulator between it and the cells prior to tab welding. I've had it happen to a pack that I build myself also... One little blob of solder in the wrong spot and all it takes is time. And of course because the entire group of cells are in parallel... They are all equally drained to 0 volts.

Replacing the bad cell group can be done, but can also be problematic. You will be replacing old worn out high resistance cells with those that are new/ discharge better/faster and will cause your BMS system to work even harder than it already has to as it is. I'm sure Dnum will chime in with more info for you.

On the side of the cells it should say the model/capacity to help get an idea of what you need.

 

[dnmun]

you may be able to just hack it down to 11S and use that until you get another battery. but you lost the second row also? i have piles of those on my table here from another old Vpower pack. too far to send.

maybe you can track down a dead Vpower pack there in europe and take them both apart and salvage enuff cells to go to 16S or even up to 20S if you find another one with only one or two dead rows. then use a 20S BMS and a new charger or your charger on top of a meanwell power supply to get up to the 73V DC from your current 44V charger.

but this shorting is why i consider these Vpower packs a fire hazard. miles had a thread of a german guy with a big Vpower pack under his cargo bed on his cargo bike. it shorted out and caught his bike on fire on a public street. cute seeing the picture of the german police just standing around watching it.

but i temper my comments now because looking at the picture i can see that they have now started using cells with a white insulating plastic ring around the anode on top of the case and under the shrink wrap so the risk of shorting on these is dramatically reduced from what it once was.

when you take it apart, be careful about how you proceed. it is hard to unfold it in the right way to be able to get the scissors in between the rows to cut through the serial connection straps. you have to open it like a book and cut like you are cutting through the binding.

if you have a metal cutting blade for your angle grinder you can make the parallel width narrower by cutting off a few selectively from the ends and then using those to rebuild the missing rows, or cut it so you can convert it to 16S -20S. you cannot cut them that way without using a grinder since they don't unfold and allow you to use scissors then.

 

[999zip999]

It's a victpower from china. So shipping back and forth would be 250usd.
You will have keep on with the trouble shooting.
These victpower packs are badly put togethere and hard to get around it.

 

[dnmun]

you should never ship a battery back to china on an airplane if it has shown evidence of being shorted such as this one. that is tantamount to attempted murder.

you seem to have identified the problem already so i don't think there is much more diagnosis to engage in. you have one dead row because it shorted.

where is there evidence of a bad spot weld? is it on an end of the row?

which row is dead?

can you finish unwrapping the pack and lay it out so we can count the number of cells in a row? also <open> your picture file in the post so we don't have to go download your picture separately.

if you have 11 good rows, then you can cut each row down in length by 1/3 and then combine those 1/3 length sections together to make rows that are 2/3 wide to match the other rows you cut the 1/3 off of.

so then you would have 11 rows of 2/3 and 5 1/2 rows of 1/3 + 1/3 (or 2/3) the original length.

if you have 20 cans in each row as you imply then if you cut 7 cans off of the end of each row, you will have 11S of 13P, and 11S 7P.

if you can identify individual cans inside the pack from the beginning that you would like to remove, you can do your cutting so that eventually they can be removed from the finished rebuild. so you would cut so that the bad can is on the end of one of the sections you cut off so you could then cut it out of the parallel string. make sense?

so now you would have 11S of 13P, and from the two 7P sections you would remove one can from either section so you would have 6P and 7P to connect together in parallel to make another 13P row.

so that would allow you to build 5 rows of 13P you would add to the 11S of 13P to make the pack go to 16S 13P and you would have about 12 spare cans to use to repair any defective spots where there is a physically damaged can.

so then you can buy a 16S BMS and a new 48V lifepo4 charger and you could use the pack as a 48V 15Ah pack for a long time.

 

[anders8899]

Hello,

I decided to turn it over to my friend who could help me to cut the pack down to 80% of its former Ah ratio.

I didnt get time to inspect the broken details more thouroghly, but apparently two rows have cells with 0V and there are even some of the other rows considered okay that have ~1V on some/all cells.

It's too bad that the cells cannot be replaced, but what I heard is that that the battery consisted of 12S x9 rows, giving 12x3.6V = 43.2 V which would be 36V when the battery is in use. So the new configuration would be 7x8 + 5x7, which would give the same voltage but less bike usage.

It woudnt be a good idea to upgrade the voltage to more than 36V since I need not only a new BMS, charger but also the engine of the bike needs to be replaced.

 

[dogman dan]

With less cells, the battery will have even less ability to handle the amps an ebike will draw. It's a plan for a failure, IMO.

The original 10 ah was too small for your motor, now you want to make it smaller?

 

[anders8899]

With less cells, the battery will have even less ability to handle the amps an ebike will draw. It's a plan for a failure, IMO.

The original 10 ah was too small for your motor, now you want to make it smaller?

I actually have 15 Ah, so it should not be a problem since the vpower shop sells batteries at 10Ah.

 

[dogman dan]

In post one, you said you have a 10 A battery. Either I mis read, or thought you meant AH.

Not quite as bad then, but 15 ah is about the minimum size for a 1000w kit. Good luck, but try to keep those amp spikes when you leave a stop sign lower when you leave a stop sign.

Cruising, using less watts, should not be the problem.

 

[anders8899]

In post one, you said you have a 10 A battery. Either I mis read, or thought you meant AH.

Not quite as bad then, but 15 ah is about the minimum size for a 1000w kit. Good luck, but try to keep those amp spikes when you leave a stop sign lower when you leave a stop sign.

Cruising, using less watts, should not be the problem.

I know, that I linked to a product http://vpower.hk/product.php?id=18 that is 10Ah, but I got 15 im sure of that

Unfortunately ill have to live with this batterypack until the next one, and then im sure ill find a better and cheaper pack than my current one.