999zip999
100 TW
Hang in there dnmun.
yesa battery, 2009 doc test subject
- Thread starter friedwires
- Start date
friedwires
100 W
thanks for your patience Dnmun, i havent had a chance to take those readings yet.i've been dealing with a few curve balls this week. i should be able to get to it this weekend
dnmun
1 PW
no problem, we just can't do anything to help until we have an idea what is going on. i am expecting one cell to read really high which shuts off the BMS. we need to find it.
friedwires
100 W
ok i have some voltage readings for you taken while manually charging
1 3.32v
2 3.98v
3 3.78v
4 3.76v
5 3.39v
6 3.86v
7 3.89v
8 3.54v
9, 10 ,11,12 ,13, 14, 15, were not seeing voltage on the low side, in this case i checked the low side on the individual cells to at least make sure the ballance wires were good.
16 3.30v
i only charged for a few minutes, the voltage was rapidly climbing and i didn't want to do any damage. Right after i disconnected the charger i noticed the top pcb on the bms was warm on the 8-16 cell end, so i decided to check voltage on the charge and discharge plugs and sure as shit i can read pack voltage on both plugs, right around 53v
i dont know what i did but it turned on. i also hooked some bulbs to it for a minute and it does discharge. i also measured 10.9 accross each of the 5 discharge fets,and read 7.09 on what i believe is the charge fet. i noticed after that the whole top board had gotten warm.
1 3.32v
2 3.98v
3 3.78v
4 3.76v
5 3.39v
6 3.86v
7 3.89v
8 3.54v
9, 10 ,11,12 ,13, 14, 15, were not seeing voltage on the low side, in this case i checked the low side on the individual cells to at least make sure the ballance wires were good.
16 3.30v
i only charged for a few minutes, the voltage was rapidly climbing and i didn't want to do any damage. Right after i disconnected the charger i noticed the top pcb on the bms was warm on the 8-16 cell end, so i decided to check voltage on the charge and discharge plugs and sure as shit i can read pack voltage on both plugs, right around 53v
i dont know what i did but it turned on. i also hooked some bulbs to it for a minute and it does discharge. i also measured 10.9 accross each of the 5 discharge fets,and read 7.09 on what i believe is the charge fet. i noticed after that the whole top board had gotten warm.dnmun
1 PW
ok, you have a buncha high cells which is turning off the BMS and that is keeping the pack from charging.
in your picture, you can see the black wire going to the negative terminal of the pack and the drain of the mosfet is connected through the tab of the mosfet to that wire. on the other side that black wire from the motor goes to the source leg of the mosfet, so when the gate voltage between the gate and source is positive, it will cause the mosfet to be turned on, and when the gate drops to 0v then the mosfet is turned off and the current will not flow from the motor through the mosfet to the negative terminal. that's how it works. that's what a BMS does. it shuts down discharge when any cell drops too low or if the current demand is too high for battery to handle.
to charge, the charging mosfet has to be turned on so the current can flow through that mosfet to charge the pack and when the voltages on any cell goes above the 3.65V set point then charge current is redirected around the cell through those resistors on the surface, (surface mount resistors), and they get hot. so everything is working as it should. except i don't understand what you meant about the others. but #16 is way out of balance and needs to be charged up to the same voltage as the others. for that you can use a single cell charger to charge just that one or you can drain the charge off the other cells with a power resistor, so they will lose enuff charge to allow the BMS to turn back on so you can continue charging #16 up. by draining the charge off the cells, the voltage on that cell will drop below the comparator setpoint and the BMS will turn the charging mosfet back on. make sense?
in your picture, you can see the black wire going to the negative terminal of the pack and the drain of the mosfet is connected through the tab of the mosfet to that wire. on the other side that black wire from the motor goes to the source leg of the mosfet, so when the gate voltage between the gate and source is positive, it will cause the mosfet to be turned on, and when the gate drops to 0v then the mosfet is turned off and the current will not flow from the motor through the mosfet to the negative terminal. that's how it works. that's what a BMS does. it shuts down discharge when any cell drops too low or if the current demand is too high for battery to handle.
to charge, the charging mosfet has to be turned on so the current can flow through that mosfet to charge the pack and when the voltages on any cell goes above the 3.65V set point then charge current is redirected around the cell through those resistors on the surface, (surface mount resistors), and they get hot. so everything is working as it should. except i don't understand what you meant about the others. but #16 is way out of balance and needs to be charged up to the same voltage as the others. for that you can use a single cell charger to charge just that one or you can drain the charge off the other cells with a power resistor, so they will lose enuff charge to allow the BMS to turn back on so you can continue charging #16 up. by draining the charge off the cells, the voltage on that cell will drop below the comparator setpoint and the BMS will turn the charging mosfet back on. make sense?
friedwires
100 W
its slowly starting to sink in :lol: but you have me a bit confused where you said that black wire from the "motor", and also current will not flow from the "motor"
"the others" meaning cells 9-15 ? i couldnt get any reading from these points, all i got was a jumpy pulsing from 0 to maybe 1.4v and all i did was check to make sure it wasnt a ballance wire issue.
"the others" meaning cells 9-15 ? i couldnt get any reading from these points, all i got was a jumpy pulsing from 0 to maybe 1.4v and all i did was check to make sure it wasnt a ballance wire issue.
dnmun
1 PW
ok, the black wire to the motor is the black wire to the controller. you don't have it set up in the bike yet so no controller either.
you measured all the cells first and they were around 3.3V by themselves, so why doesn't that voltage make it to the BMS?
those cell voltages need to be present on the BMS at those pins on the BMS.
you are measuring where there are the little plated through holes numbered 1-8 and 9-16 on the lower side of the BMS?
measure the voltage of cell #1 with the black probe on the black wire to the pack, the one that is attached to the drains of the mosfets, and the red probe on the hole labeled 1. that is cell #1, then measure between 1 and 2 for cell #2 and so on up to #16.
is the charger light switching on and off with the pulsing voltage?
do you have another voltmeter you can use to measure current from the charger while you are testing?
this is where having the right tools helps make it easier to work. if you could see what the current is if it is pulsing on and off that is informative too. but first gotta see if you can get the cell voltages to appear on the BMS as they are on the cells themselves. you don't have to have it on the charger for that since we already know why the charger is shutting off. once those cell voltages are present on the BMS then we can figure what's what.
you measured all the cells first and they were around 3.3V by themselves, so why doesn't that voltage make it to the BMS?
those cell voltages need to be present on the BMS at those pins on the BMS.
you are measuring where there are the little plated through holes numbered 1-8 and 9-16 on the lower side of the BMS?
measure the voltage of cell #1 with the black probe on the black wire to the pack, the one that is attached to the drains of the mosfets, and the red probe on the hole labeled 1. that is cell #1, then measure between 1 and 2 for cell #2 and so on up to #16.
is the charger light switching on and off with the pulsing voltage?
do you have another voltmeter you can use to measure current from the charger while you are testing?
this is where having the right tools helps make it easier to work. if you could see what the current is if it is pulsing on and off that is informative too. but first gotta see if you can get the cell voltages to appear on the BMS as they are on the cells themselves. you don't have to have it on the charger for that since we already know why the charger is shutting off. once those cell voltages are present on the BMS then we can figure what's what.
friedwires
100 W
ok so the black wire to motor would be the discharge wire, and yup im measuring at the numbered holes ,and no the charger didnt pulse on and off. i'll take those readings and report back. i also noticed today after the pack rested overnight that the resistor board is still hot all the way accross. and since the pack is made up of two strings of 8 cells i decided to measure them that way. measuring from the battery terminals for cells 1-8 i get 26.4 volts and for 9-16 im only getting 25.3v i'll se if i can get on of my old meters up and running. thanks again for your patience dnmun.
dnmun
1 PW
all rows of surface mount resistors were warm or just some of them?
the pulsing is curious, but focus on getting the cell voltage measurement right on the BMS for each cell now. then watch them to see if they drop over time. and how fast. and if one or more is dropping faster than the others.
the pulsing is curious, but focus on getting the cell voltage measurement right on the BMS for each cell now. then watch them to see if they drop over time. and how fast. and if one or more is dropping faster than the others.
friedwires
100 W
yeah dnmun, the four original suspect cells are just falling on their ass, cells 5,8,9,16 charging themk individually brings them up but they just fall right off. couldnt i just yank these 4 cells out of the pack and reconfigure for a 12s pack? and will i also need a 12s bms?
dnmun
1 PW
you may be able to find some identical prismatic cells too, but yes, it could be reconfigured to 12S.
i am not familiar with that BMS, but on the ping signalab, you just jumper over the opto isolators for the missing cells so they don't create an open in the opto series that goes to the comparator. that way the BMS never knows the cells are missing.
other doc, docnjoc, did that on his ping. but you need a 12S charger then too.
those 10Ah prismatics should be available somewhere.
i am not familiar with that BMS, but on the ping signalab, you just jumper over the opto isolators for the missing cells so they don't create an open in the opto series that goes to the comparator. that way the BMS never knows the cells are missing.
other doc, docnjoc, did that on his ping. but you need a 12S charger then too.
those 10Ah prismatics should be available somewhere.
friedwires said:
You could just go "bareback", after you test how many AH you get out of each of the 12 cells (under whatever amps you normally pull) and just use the pack until .5Ah left of the smallest one.
It's easy to be your own BMS when it's only 12 cells and you know the limits of them.
Have you tested all the cells to see what their individual capacity is yet?
(Obviously without the BMS)
dnmun
1 PW
the only people who go bareback are those too lazy to figure out what is wrong with the pack to cause the BMS to shut down.
a BMS is required to keep the pack balanced and prevent you from overcharging or overdischarging the pack while in operation or charging.
it does seem like that BMS is functioning normally, there are bad cells that cause it shut off, imo. you don't even have to find identical cells to those prismatics to use as a replacement in the 16S series. i just think those would be most convenient to use since you have the connectors for them already.
i think those cells are all about 2C rated so if you could find another four lifepo4 cells of the same rated capacity, 10Ah, and 2C rated, then you could swap them out and use the same 16S BMS, and the 48V charger. that would cost about the same as buying a 36V charger and 12S BMS. and you would have 33% more power for the same money added to the project. jmho.
or you could double down, buy 20 new 10A cells and wire the new set in parallel with the current 12S plus 4S new, and then have a 48V20Ah pack using that 16S BMS, that would be more along the lines a scooter needs. jmho.
a BMS is required to keep the pack balanced and prevent you from overcharging or overdischarging the pack while in operation or charging.
it does seem like that BMS is functioning normally, there are bad cells that cause it shut off, imo. you don't even have to find identical cells to those prismatics to use as a replacement in the 16S series. i just think those would be most convenient to use since you have the connectors for them already.
i think those cells are all about 2C rated so if you could find another four lifepo4 cells of the same rated capacity, 10Ah, and 2C rated, then you could swap them out and use the same 16S BMS, and the 48V charger. that would cost about the same as buying a 36V charger and 12S BMS. and you would have 33% more power for the same money added to the project. jmho.
or you could double down, buy 20 new 10A cells and wire the new set in parallel with the current 12S plus 4S new, and then have a 48V20Ah pack using that 16S BMS, that would be more along the lines a scooter needs. jmho.
I thought they were 15Ah cells? No?
Depends on what his needs are...
If he only needs the pack to go 15 miles round trip and the cells are 15Ah.. That should give him some wiggle room and should give the cells just enough usage to stay balanced...
The whole point was be paid $100 for it..
If it works as a 36v 15Ah battery for $100 then he's way ahead of the game..
That's, of course, if he already has a 36v charger...
I don't believe this pack came with a charger, either.
Going out and buying 4 new 15Ah cells would still be a little problematic as those would be new and the others old. (e.g. IRs would be way different)
Let's find out what the OP actually wants to use the pack for and go from there..
Depends on what his needs are...
If he only needs the pack to go 15 miles round trip and the cells are 15Ah.. That should give him some wiggle room and should give the cells just enough usage to stay balanced...
The whole point was be paid $100 for it..
If it works as a 36v 15Ah battery for $100 then he's way ahead of the game..
That's, of course, if he already has a 36v charger...
I don't believe this pack came with a charger, either.
Going out and buying 4 new 15Ah cells would still be a little problematic as those would be new and the others old. (e.g. IRs would be way different)
Let's find out what the OP actually wants to use the pack for and go from there..
friedwires
100 W
these are 15ah cells and i think 3c and no charger.i was planning to use it for a scooter at 48v. but at 12s the pack could be narrow enough for ebike use. i also live in flatlands so 12ah of lead will get me over 15mi.. 15ah lifepo4 should get me over 20mi no problem. i'm sure i could handle being the bms but plug and play would be best.so i'll need a new bms and charger. if i do decide to go bareback it would have nothing to do with laziness. i have two jobs,two kids,an old house, and a budding ebike business. theres is no time for laziness. where can i find a bms and charger?
docnjoj
1 GW
Actually I ended up making a 36 volt split battery from the 48 volt Ping and bought a new 36 volt Signalab BMS from Ping. It has been running fine and in balance for about 2 years. The old BMS failed at the XH JST connector. I originally jumped the optos but it was a bad connector that actually caused the original failure. Dnmun really was helpful and walked me through it!
otherDoc
otherDoc
The only issue is that the cells are old (and used) to begin with..
IMO, I personally wouldn't add more (new) cells to the old....
It's "bad kharma"...
Problem also is, a new BMS is gonna cost some bucks as well as a charger and you still haven't tested the capacity of the cells yet, if I'm correct.
First order of business is to test the cells...
On small format prismatics, I use a 100w auto bulb (or two)..
Two in parallel would draw 16 or so amps and would give you a basic idea of how the cells are..
1C test is usually crucial...
Gives you a baseline for .5C and 2C. (will give more at .5C and even less at 2-3C.)
You could do 4 at a time and the MOST it would take is 3 hours.
I used to just take cells and 4 at a time watch the voltages.. When a cell would drop, I would mark it's AH down and replace that cell and start over again, one at a time, switching cells out and recording AH..
(I actually did that with the first 17 (YESA) cells (first time I ever "played with" prismatic cells) that I bought from someone a few years ago off of craigslist. I still have 4 of those cells (1s/4p) running a battery operated beard trimmer! It's been running for 2 years now and I still haven't charged up the cells yet!)
LOL
IMO, I personally wouldn't add more (new) cells to the old....
It's "bad kharma"...
Problem also is, a new BMS is gonna cost some bucks as well as a charger and you still haven't tested the capacity of the cells yet, if I'm correct.
First order of business is to test the cells...
On small format prismatics, I use a 100w auto bulb (or two)..
Two in parallel would draw 16 or so amps and would give you a basic idea of how the cells are..
1C test is usually crucial...
Gives you a baseline for .5C and 2C. (will give more at .5C and even less at 2-3C.)
You could do 4 at a time and the MOST it would take is 3 hours.
I used to just take cells and 4 at a time watch the voltages.. When a cell would drop, I would mark it's AH down and replace that cell and start over again, one at a time, switching cells out and recording AH..
(I actually did that with the first 17 (YESA) cells (first time I ever "played with" prismatic cells) that I bought from someone a few years ago off of craigslist. I still have 4 of those cells (1s/4p) running a battery operated beard trimmer! It's been running for 2 years now and I still haven't charged up the cells yet!)
LOL
friedwires
100 W
my meter onl reads up to 10 amps so should i just test at .75c
I'm guessing you dont have a wattsup or Turnigy watt meter?
P.S. If you read the "warning" on any of the fluke-type basic meters, you will see not to hook it up for more than 10-15s every 30 min for amp readings..
If you have a $3 "harbor freight" crap-type meter, then I would suggest using that for amp measurements..
But you still will have to figure out When the batts are almost fully discharged by removing the load and changing the meter from Amp to voltage.. Just wait until the light gets really dim and then check voltages.
If you don't have one, buy a watt meter, will help out tremendously.
P.S. If you read the "warning" on any of the fluke-type basic meters, you will see not to hook it up for more than 10-15s every 30 min for amp readings..
If you have a $3 "harbor freight" crap-type meter, then I would suggest using that for amp measurements..
But you still will have to figure out When the batts are almost fully discharged by removing the load and changing the meter from Amp to voltage.. Just wait until the light gets really dim
and then check voltages. If you don't have one, buy a watt meter, will help out tremendously.
friedwires
100 W
i know it, i could use more than one too.
dnmun
1 PW
yes, you need more than one to test capacity. but you should not be discharging these cells if you cannot charge them up.
how do you charge the individual cells now and can you get them to 3.65V?
how do you charge the individual cells now and can you get them to 3.65V?
friedwires
100 W
i use three 5v 750ma wall warts paralelled.it gives me about 2.3a for charging. it takes a while but brings them right up there, been charging to 3.69v. i have a few misc power supplies laying around here, maybe i can rig up something faster
dnmun
1 PW
that's ok, just don't let them get much over 3.7V. that is fully charged and more charging can damage the cells if they go over 4-4.2V.
if they all hold voltage, then that is enuff for now, until you can get the BMS and charger figured out. try following the traces on the BMS to find which of the opto isolator strings goes to the charging FET and which goes to the IC that controls the output FETs. there should be tiny 5-6 legged ICs that function as comparators on the traces of each cell, with their output going to the optos.
this is where reading about the mosfets on wikipedia helps so you will know that the gate is what controls the mosfet. just takes time to learn this stuff. but learning it gives you the power to fix stuff too.
or wait and see if you can get another 4 cells like these.
if they all hold voltage, then that is enuff for now, until you can get the BMS and charger figured out. try following the traces on the BMS to find which of the opto isolator strings goes to the charging FET and which goes to the IC that controls the output FETs. there should be tiny 5-6 legged ICs that function as comparators on the traces of each cell, with their output going to the optos.
this is where reading about the mosfets on wikipedia helps so you will know that the gate is what controls the mosfet. just takes time to learn this stuff. but learning it gives you the power to fix stuff too.
or wait and see if you can get another 4 cells like these.
friedwires
100 W
i think this project will have to be put on the back burner for a while. I yave other projects that need my attention at the moment, and i also need to order a single cell charger. i'm already down to 12s and dont want to risk loosing any more cells.
dnmun
1 PW
i have 3 pings in process of getting repaired too. and 2 more in parts, other stuff to do all the time. like my house, still gutted and remodeling the upstairs, windows, more and double up insulation, all new bath with shower added, new flooring, sheetrock sheetrock sheetrock.
but something may come along in the meanwhile, maybe a 12S BMS will appear. or a charger.
i think it is sure electronics or one of the other chinese ebay sellers who have a 40W single cell charger for $19.99.
but something may come along in the meanwhile, maybe a 12S BMS will appear. or a charger.
i think it is sure electronics or one of the other chinese ebay sellers who have a 40W single cell charger for $19.99.
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