Battery surgery replacing BMS wires

[OCD Garage]

I've got a 48 volt 20Ah 'duct tape' style battery from CDI. Every now and then my system shuts down completely, I disconnect, then reconnect the positive lead and the bike goes again. Last time this happened my BMS was at fault and I replaced it with exactly the same factory one from CDI. This time I'd like to install a heavy duty 50amp model I bought from Ping but the connectors for the circuit board are different. Do I need to solder the new connections directly onto the battery tabs? Does it matter if they go in exactly the same spot as the originals? Inside my pack looks like two banks of cells glued together with some of the BMS wires going in the middle, do I need to split these apart or can I splice the BMS wires onto the originals?

Thanks

 

[cassschr1]

Can you post pictures? What connections aren't the same? Just trying to help.

 

[dnmun]

we have no idea what kind of battery so you have to post up pictures of the battery and the BMS showing how you have it wired up and you need to put the battery on the charger and measure the individual cell voltages on the BMS pcb where the sense wire plug is soldered to the pcb.

 

[OCD Garage]

Thanks guys, will post pics soon. The plugs for the two different BMS boards are not the same; one has a single plug with 16 wires, the other has 2 plugs with 8 wires each and don't appear to interchange. Will post pics of the setup soon.

 

[dogman dan]

16 wires total, means your negative wire to cell number one is the main negative lead from the battery.
Connect each small positive wire to your new plugs one by one, keeping them in the same order as before.
Sounds like you will need two 8 pin plugs to make the connection now.

 

[dnmun]

yes, you can solder to the old wires if you cannot reach to the spot with the soldering iron.

keep the sense wires in order on the connector.

measure each pin on the plug before you connect it to the BMS to insure the voltage on each wire increases sequentially and is not reversed.

to measure the first cell on the ping BMS you measure between the B- spot and the first wire off the top of the first cell.

 

[OCD Garage]

Here's a few pics of the troublesome unit which, when working properly is a CI Power 48v 20ah LiFePo4 pack I've had for about 2.5 years.


I was surprised how much duct tape and cardboard were actually on this thing.


Here are the two BMS. You can see the 16 wire plug on the Ping one and 2x 8 wire on the CIP one. I think if you place the two 8 wire plugs next to each other they are laid out the same as the single Ping plug; one side connecting nearest the B+, the other nearest the B-.


There are only three clearly marked wires to solder on the circuit board, can I use this solder gun or do I need the lower watt iron type?


I'd appreciate any help or insights you could lend, the way I'm working you'd think I was trying to defuse a bomb! I'm definitely out of my comfort range but learning quickly.

 

[Gregory]

measure each pin on the plug before you connect it to the BMS to insure the voltage on each wire increases sequentially and is not reversed.

16 wires total, means your negative wire to cell number one is the main negative lead from the battery.

- measure it to check

I quote this because it's important, both excellent ideas.



Or another idea - assuming they are both JST-XH connectors can you use a small screw driver to back the original plugs out of their dual housings and slide them into the emptied ping plug? Keeping them in order, avoiding shorts and checking voltage as you go. Might save you lengthening all the Ping sense wires.

The soldering iron looks fine for the main pack leads.

 

[999zip999]

Yes maybe the pins are the same size and you can careful slide out the pins and fit them in the singalab plug. The pins on the battery side are hot so be careful and make sure you are careful with the lock pins and don't brake them. I would wait for some other's the chime in first on the other down sides of this opion. I always like an extra set of sense wires for checking cell voltage and for single cell charge balancing.

 

[dnmun]

there may not be anything wrong with the original BMS. before you change anything you should put the battery on the charger and measure the cell voltages on the BMS pcb.

you can measure the voltage between each pin on the spot where the sense wire socket is soldered to the pcb

measure while the battery is charging and list the voltages here on your thread.

after that, then we can get you to check to see if the mosfets are functional.

 

[OCD Garage]

Thanks for the suggestions guys. I will charge again and list the battery voltages at the plug in about 24 hours (time to go mountain biking tonight). I had the same problem about a year ago, BMS problem burned one of the sensor plug wires, that wire looked a bit questionable so I replaced the entire (8 pin) plug but the bike still shut down randomly so at least I know the plug wasn't the problem. Will post battery voltages before changing anything else. I just thought as I had the Ping BMS it may be a safer bet in the long run as the quality and capacity are likely much better than the CIP one. Is it possible that my 1000+watt Golden motor is drawing more current than the CIP BMS can deliver? When I run this motor it is generally full throttle from my house to whatever destination I'm travelling, nothing seems to get hot, I assume the BMS has to be matched to the current draw of the motor, and I have no specs on what I was sold to replace my first one. Anyway one step at a time.

 

[OCD Garage]

Left the battery pack on the charger overnight, today while showing the green light = 60.1 volts across (+) and (-) leads, testing with a probe on the circuit board, lower plug; 3.7, 7.5, 11.2, 15.0, 18.7, 22.5, 26.3, 30.0. Upper plug; 33.7, 37.5, 41.2, 45.0, 48.8, 52.2, 58.3, 60.1. All the cells appear to be 3.7 - 3.8 different from each other. What's next to test?

I have little doubt the Ping BMS is far superior to the CDI board which appears to have less than 50% as many electronic components and about 90% less solder build up. Would a higher output BMS like the Ping one give me increased power at the wheel, or just increased reliability in the long run? I managed to get a free BMS from CDI last time I had trouble and so didn't use the Ping one which I think is rated at 50a.

Thanks

 

[999zip999]

Please post cell voltage like this.

1. 3.55v
2. 3.45v
3.3.65v



11. 3.55v
12. 3.65v



16. 3.60v

ect.
Easy reading. Thanks

 

[999zip999]

You have a Ping singalab 5 fet. or the big one 10 fet. ?
First follow Dmumn's teaching in his steps. Dmumn does know so if you follow he's advise is best. I just add color.
As for your first post yes each sense wire is in other and MUST be in order as 1 thru 16. yes don't mix up the order. As building a battery in series the bms is in series to build the voltage from 3,6 to 57.6v. ect.
Cell #1
1. 3.6v
2. 7.2v



16. 57.6v.
Now this is for the bms state of pack charge and not the cell voltage I ask for early.
As
1. 3.6v
2. 3.5v





16. 3.6v. each cell voltage for state of balance.

What is the demand in amps of your controller and how do you ride many hills ? Do you ride around hills or teat ride up and down the same hill to test you ride ? Plus you need to tell us where you live. Plus your pounds.

 

[OCD Garage]

I hope I got this right; here's the voltages as measured at the pins of the plug with the battery charger on, green light showing fully charged.

1. 3.7v
2. 7.5v
3. 11.2v
4. 15.0v
5. 18.7v
6. 22.5v
7. 26.3v
8. 30.0v

9. 33.7v
10. 37.5v
11. 41.2v
12. 45.0v
13. 48.8v
14. 52.2v
15. 58.3
16. 60.1

These are the differences between the cells

1. 3.8v
2. 3.7v
3. 3.8v
4. 3.7v
5. 3.8v
6. 3.8v
7. 3.7v
8. 3.8v
9. 3.7v
10. 3.8v
11. 3.7v
12. 3.8v
13. 3.7v
14. 3.7v

The kit I bought on ebay from a seller named SunThing. It was advertised as a 1000 watt kit and appears to use a Golden Motor Magic Pie 1st Gen hub motor, I do not know the exact amperage of the controller but as the bike does 55-60km/hr it's likely 30amp? I weight 175lbs (79kg), live on the west coast of Canada in a fairly hilly city near the oceanside. I have been using the kit to commute to work (20 min each way) on a poor quality mountain bike for approximately 2.5 years and had this exact same symptom about a year ago, which replacing the BMS solved. The Ping BMS appears to have 12 fets and 32 other transistors. Should I just solder the Ping board in place and run with it? :wink:

Here's what the bike looked like before going to LiFePo4, nothing special, but good, cheap, reliable, short distance transportation

 

[999zip999]

You have the high discharge signalab bms from Ping. It has a higher cutoff current. I do believe you have a 30 amp controller that can see spikes of 38 amps this is just a guess without a meter. This is the max or maybe a little hard on your. Like if you test ride up and down a steep hill. That's what I did at first and the bms keep cutting out. I unplugged and plug the battery resetting the bms and killing a cell test rideing up a hill. I'm 220lbs. so it was hard on the setup.
The second set of numbers is easier to see each cell voltage but you are missing 15 and 16 cell. The cell voltage is at the point that the bms kicks in to bring down the cells. You did this without the bms hooked up ? What is your charger voltage ?
Please give voltage on 15 and 16. If at 3.65 to 3.8v fine I would install the new bms. I think Dmumn had some test for the old bms. But it does have a lower cutoff than the Ping bms. It is also harded on the battery as the cutoff is higher.

 

[dnmun]

i just noticed your comment about the sense wire burned up. that most likely was the result of shorts between different levels of the battery so that BMS could be damaged if the current during the short was able to damage the little transistor that shunts the current around the cell when it is full. that is hard to test on the BMS with the big aluminum heat sink on top.

that big BMS with the 12 mosfets is the same one that both sun-thing guy and mr ping both use for their high current BMS.

it does look like your pack is balanced ok, you can measure the cell voltages right on the base of the pins for the sense wire plug where it is soldered into the pcb. the charger is set to 60V like ping does also. i used to think that was ok but w9bk guy has got me worried about the 'plating' from overcharging above 3.60-3.65V/cell so if you wanna reduce the charger voltage down to 58.4V or so we can walk you through that too.

you should be getting the full amount of capacity from the cells on discharge. if you have a watt meter we can do a discharge of the battery to see how much capacity is in the cells and which ones may be draining down first and how much capacity the lowest ones have. that is the weak link in the chain. the cells with the lowest capacity limit the entire battery to that cell's capacity.

ok, just saw the picture of the controller, looks like 18 fets, so it may be causing the BMS to shut down for over current. this is where having a cycle analyst or even a watt meter is really helpful. except a watt meter cannot save the peak current that shuts down the BMS like the cycle analyst does.

 

[OCD Garage]

This morning I successfully soldered the Ping BMS to the CDI battery and had about 45 minutes of good riding and then the same thing happened, the whole system shut down. I was able to disconnect and then reconnect the battery lead and ride half way home, when the system shut down again. I have been riding this system for about two years mostly trouble free, is there something in the battery I could be missing that would account for this? The draw from the controller and my riding style have never been a problem before. I do not have a cycle analyst or other watt meter, sorry.

 

[999zip999]

You did charge and let it balance before your ride ? How about the voltage on 15 and 16, These are important things first.

 

[OCD Garage]

Before changing the BMS I had charged the battery until the green light was on the charger (60.0v), however, the cells may not have been balanced. After changing the BMS to the Ping unit I rode the bike for about 1.5 hours until in a similar manner to the previous times, it shut down (although I didn't check pack voltage at that time). After putting the battery on charge overnight to balance/charge I saw 60.0 volts on my multimeter again this morning and managed to ride to/from work without incident. I was very cautious on the amps (acceleration/hills) but I am fairly confident the problem is not over yet. I did realize through this that I may have not tested the individual cells properly. I basicly measured each BMS wire and subtracted one from the next to get the numbers as posted (3.8, 3.7, etc) is there a better way to determine the voltage of each cell individually? That's why I only got 14 values for the 16 cells. Also about this overcharging battery charger, you say it should only top out at 58 volts? Now how to adjust, is there a potentiometer inside I can tweek? Could a constant charge to 60v shorten the life of the pack?

Thanks

 

[OCD Garage]

I've been giving the ebike a bit of a face lift for summer fun during this, mostly made from things I already had. It still needs some finishing and paint. Sure rides and stops better than the old death trap and it's undampened, v-braked fork. The Ping BMS is quite a bit longer and doesn't fit in the old box. Does the BMS need much air space around it? I've seen them raw, shrink wrapped right in with the battery, is that okay or is it important for it to breath?

Thanks

 

[999zip999]

What ? Put the battery on the charger so the bms can balance all cells. No do not think it's right because you want to go for a ride. let the bms have time on the charger for the battery pack to balance. Then take a short ride 5- 10min at the most charge and let it sit on the charger to balance. Take a short ride and charge till the leds come on all leds. Do not do long test rides to trip the bms and unbalance the battery. No you do not have to find the lvc of the pack. You are triing to balance the pack first.