Battery cutting out at

Samsung 25R (2500mAh) is the most popular (20amp rating) name brand reasonably priced 2500mAh cell (green wrap). Your pink wrap cells are no name brand Chinese cells. There are no popular name brand 18650 2500mAh cells that have a pink label wrap. Doubtful the seller will call back. He may not even know the cell manufacturer. Even if he does there is no way knowing if ALL the cells are truly A-grade quality.

To find out if the problem is cell related or BMS ... you could buy a new replacement BMS. Could be an inexpensive fix before you spend $100-$150 on an AliExpress 13s5p(or 6p) flat scooter battery with no name brand cells (questionable A-grade quality).

If you have the know how you could measure the voltage of each of the 13s 5p groups at the BMS connector. That will tell you if you have weak/dead cell(s) in one (or more) of the thirteen parallel groups (e.g. only 3v or less) that is causing the BMS to shut off the power to the motor. Even if only one of the thirteen 5p parallel groups is under performing the BMS should shut off power to the motor.

eMark said:

Samsung 25R (2500mAh) is the most popular (20amp rating) name brand reasonably priced 2500mAh cell (green wrap). Your pink wrap cells are no name brand Chinese cells. There are no popular name brand 18650 2500mAh cells that have a pink label wrap. Doubtful the seller will call back. He may not even know the cell manufacturer. Even if he does there is no way knowing if ALL the cells are truly A-grade quality.

To find out if the problem is cell related or BMS ... you could buy a new replacement BMS. Could be an inexpensive fix before you spend $100-$150 on an AliExpress 13s5p(or 6p) flat scooter battery with no name brand cells (questionable A-grade quality).

If you have the know how you could measure the voltage of each of the 13s 5p groups at the BMS connector. That will tell you if you have weak/dead cell(s) in one (or more) of the thirteen parallel groups (e.g. only 3v or less) that is causing the BMS to shut off the power to the motor. Even if only one of the thirteen 5p parallel groups is under performing the BMS should shut off power to the motor.

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I will have to take apart after a full charge and do what you've said..Take the battery out and test what cells are bad .I will upload a pic in the next few days .and if it's possible..someone can yell me wear to put probes ....I will add a pic it's pretty much identical.but pink cells

Pager880 said:

I will have to take apart after a full charge and do what you've said..Take the battery out and test what cells are bad .I will upload a pic in the next few days .and if it's possible..someone can yell me wear to put probes ....I will add a pic it's pretty much identical.but pink cells

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Take voltage readings of each parallel group to see which groups are close to the same voltage and which ones are suspect. You can do this at the BMS connector using your dc meter voltage probes. That way you don't need to remove all of the shrink wrap from your 13s5p flat scooter battery.

If possible will upload photo tomorrow showing how the 13 voltage parallel group readings are taken on BMS connector. Care is a must so you don't cause a short as the pin spacing on BMS connector is close. If in doubt remove battery shrink wrap for testing at the parallel groups. If it looks like there are weak/bad cell(s) it's best to buy a new battery instead of trying to fix.your old 15s5p. Then buy a good 15s6p flat scooter battery.

Record parallel group voltage readings before charging as that will better show which parallel group(s) are weak/bad. You don't need to fully charge to determine what parallel group(s) are weak/bad (likely less than 3V) having less voltage than the other good parallel groups (e.g. 3.7V)

eMark said:

Take voltage readings of each parallel group to see which groups are close to the same voltage and which ones are suspect. You can do this at the BMS connector using your dc meter voltage probes. That way you don't need to remove all of the shrink wrap from your 13s5p flat scooter battery.

If possible will upload photo tomorrow showing how the 13 voltage parallel group readings are taken on BMS connector. Care is a must so you don't cause a short as the pin spacing on BMS connector is close. If in doubt remove battery shrink wrap for testing at the parallel groups. If it looks like there are weak/bad cell(s) it's best to buy a new battery instead of trying to fix.your old 15s5p. Then buy a good 15s6p flat scooter battery.

Record parallel group voltage readings before charging as that will better show which parallel group(s) are weak/bad. You don't need to fully charge to determine what parallel group(s) are weak/bad (likely less than 3V) having less voltage than the other good parallel groups (e.g. 3.7V)

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Ok I will try do that over the weekend..as I am Verry busy ..will upload results THANKS for the detailed.reply very appreciated

CAUTION: To prevent a short by probes accidentally touching each other while taking parallel group voltage readings.

Keep the negative probe on the first negative pin for all 13 parallel group readings. Then move down the line with the + probe recording voltage readings for the 13 5p groups. It's safer this way as the two probes are only the closest when taking your first B1 reading. Then as you progress down the line with the + probe the voltage readings keep adding with the 13th reading being the total battery voltage. Then you have to subtract to get the voltage of each parallel group.

As example: B1-3.7v, B2-7.4v(3.7v) B3-11.1v(3.0v), B4-14.8v(3.7v) ... etc, etc. Hopefully, you will get voltage readings from all 13 connector pins. That's assuming there is no loose or broken solder connection with any of the BMS sensing lead wires.

Just be careful when taking the first (B1) reading so the two probes don't accidentally touch each other (being so close) and accidentally fry a tiny sensing wire. If that would happen then you'd have to run a new BMS 13s connector with sensing leads soldered to each parallel group.

eMark said:

CAUTION: To prevent a short by probes accidentally touching each other while taking parallel group voltage readings.

Keep the negative probe on the first negative pin for all 13 parallel group readings. Then move down the line with the + probe recording voltage readings for the 13 5p groups. It's safer this way as the two probes are only the closest when taking your first B1 reading. Then as you progress down the line with the + probe the voltage readings keep adding with the 13th reading being the total battery voltage. Then you have to subtract to get the voltage of each parallel group.

As example: B1-3.7v, B2-7.4v(3.7v) B3-11.1v(3.0v), B4-14.8v(3.7v) ... etc, etc. Hopefully, you will get voltage readings from all 13 connector pins. That's assuming there is no loose or broken solder connection with any of the BMS sensing lead wires.

Just be careful when taking the first (B1) reading so the two probes don't accidentally touch each other (being so close) and accidentally fry a tiny sensing wire. If that would happen then you'd have to run a new BMS 13s connector with sensing leads soldered to each parallel group.

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Well ..did what you suggested with multimeter..did it in garden in natural light ...and think I blew up the BMS ....as touched 2 pins together with probs ..and was getting no reading's from BMS ....so just perchesed a new 1 ..with leads .only thing is the red and the black wires are on opposite ends to original one ..is that a problem...and as soon as that happened I stoped as .didn't want to get blown up

First objective was to determine the voltages of the thirteen 5p groups using the BMS connector (not the BMS). See 1st paragraph of post #28. My mistake in not being more specific ... thought you would figure it out.

You were to disconnect the BMS from its connector in order to get the voltage readings from each of the 13 parallel groups. There's no reason for needing the BMS connected in order to record each of the thirteen 5p voltages? Obvious from your Left & Right photo that you did not disconnect BMS from it's connector before recording voltages of all thirteen 5p groups.

The idea is that doing it via the BMS connector you don't need to remove more protective wrap and possibly a partial disassembly of pack in order to measure voltage at each of the thirteen 5p groups. Your left and right photo doesn't show that you first disconnected the BMS from its connector before attempting to record the 5p voltage of all 13 parallel groups.

You may have already caused a short that fried one of the tiny sensing lead wires of the BMS connector (and damaged that BMS 5p circuit(?). A short will happen if the two probes accidentally touched each other while attempting to measure voltage of one of the 5p groups via the tiny sensing wire connection at the BMS connector

... "and think I blew up the BMS" ... now you understand why the BMS should've been disconnected as you don't need the BMS connected when recording voltages of the thirteen 5p groups. Besides damaging the BMS one of the tiny sensing wires was fried where it's attached in the BMS connector.

"only thing is the red and the black wires are on opposite ends to original one ..is that a problem...and as soon as that happened I stoped as .didn't want to get blown up " ...

The single lone wire is negative (should be black). The thirteen positive wires should be red.

The problem is that you now need to remove existing: BMS connector, Unsolder lone negative black wire, Unsolder and remove the 13 lead wires at each 5p location. Then resolder black negative and 13 sensing wires from your new BMS connector to parallel group. Dot sure how specific to get as assume you can figure it out. Whether new or old the BMS' 13 sensing positive tiny wires should be red and lone negative tiny wire black.

Why did you think your BMS needed to be plugged into its connector (see left and right photo) in order to manually record voltages of the thirteen 5p groups using your dc meter probes? You can't check the condition of the BMS until you know for sure that all the cells in the thirteen 5p groups are OK/usable. Can you see why you may not have needed to do what now is necessary (assuming your BMS was AOK, which wasn't a given and now is no good). Perhaps it's better that you now have to measure and record the thirteen 5p voltages directly off of each 5p group. Thus enabling you to determine if the 13 5p groups are still OK (usable as is) or not worth repairing.

Sorry I'm new to testing batteries and faulty stuff that's why I'm on hear asking for IE help ...I'm sorry I didn't disconnect the BMS .I didn't know I had to...but we learn by are mistakes don't we ...

FYI - The new BMS

Pager880 said:

Sorry I'm new to testing batteries and faulty stuff that's why I'm on hear asking for IE help ...I'm sorry I didn't disconnect the BMS .I didn't know I had to...but we learn by are mistakes don't we ...

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Don’t worry about it. Every DIYer will make a mistake at some point. For some it might be with a $400 controller, so you’re fortunate it was a cheap battery. You’ll be a lot more careful in the future.

Diggs said:

FYI - The new BMS
View attachment 356182

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Pics of new BMS

Pager880 said:

Pics of new BMS

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I saw those earlier and fed one picture to Google's AI as I wanted to know what it said. I shared the result above. (Thought others may want to know.)

Pager880 said:

Sorry I'm new to testing batteries and faulty stuff that's why I'm on hear asking for IE help ...I'm sorry I didn't disconnect the BMS .I didn't know I had to...but we learn by are mistakes don't we ...

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Can see why it might seem easier measuring the 5p group voltages with the BMS connected and laying flat/secure to stabilize while taking readings (see photos). That way should be less chance of accidentally causing a short should the neg and plus probes briefly come in contact with each other while taking/recording 5p voltage readings (B1 through B13).

It shouldn't cause any harm with the BMS connected as long as there wasn't an accidental short while measuring any of the 5p group voltages. Because of the diameter of some DMM probes and, the closeness of BMS connector pins there's more risk that the two DMM probes could momentarily touch each other while measuring 5p voltages. Only takes a nanosec to short (melt and disconnect a tiny sensing wire from its BMS connector. Because it happens so quickly there is no chance of harm to the 5p cell group ... but could damage the BMS. That's why it's best to disconnect the BMS. However it now necessitates having to remove and replace with a new BMS connector with each of its sensing wires (in tact) soldered onto the appropriate 5p group.

Reedited for clarification (5:30 PM) ... Hoping you can figure it all out. Sometimes what works best for one DIYer doesn't work for another.

eMark said:

we, we

Magnifying your middle photo can see why it would be easier measuring the 5p group voltages with BMS connected and laying flat to stabilize while taking readings. That way should be less chance of accidentally causing a short if the neg and plus probe come in contact with each other while taking a voltage reading (B1 through B13).

Wouldn't think it should cause any harm with the BMS connected as long as there wasn't an accidental short while measuring any of the 5p group voltages. Because of the size of some DMM probes and the closeness of BMS connector there's more risk they could momentarily touch each other while measuring 5p voltages only taking a nanosec to melt and disconnect a tiny sensing wire at the BMS connector. Because it happens and is over so quickly there is no chance of harm to the 5p cell group, but you have to remove and replace the BMS connector and sensing wires.

Hoping you can figure it all out with the least amount of drama. Sometimes what works for one DIYer (me) doesn't work for (we).

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