BMS balance part come hot when charging and after

[General_Lee]

Hi guys, I built a new battery pack and I double check my wires to BMS, all is ok. When I start charging (5 amp) the BMS come hot, balance side I think.

When I plugged the BMS for the first time, the total pack it was 48v, the BMS it not be hot, but during the charge it come hot and after charging completed too, stay hot.

The probleme it is the cells? I checked each parallel branch and the higher voltage is 4.2 and lowers 4.18.

You can check the attachments.

Cells, Samsung 18650 30A
BMS: HCX-D166
Pack: 48v 13S 9P

charging with Cycle Satiator (54.6V at 5 amp)

 

[Grizzl-E]

It "balances" by burning off charge on high cells through a resistor. Thats what its supposed to do.


Sent from my iPhone using Tapatalk

 

[eva-michael]

Resistor bleeding BMS will consume the energy of higher voltage cell by heat emission via resistor.
Generally this process will stay for a while after finish charge, because BMS will still need some time to balance all cells to appropriate synchronous voltage.
If the resistor keep bleeding and always stay heat emission no matter charge or not charge, then you must double check the connection.

 

[General_Lee]

Resistor bleeding BMS will consume the energy of higher voltage cell by heat emission via resistor.
Generally this process will stay for a while after finish charge, because BMS will still need some time to balance all cells to appropriate synchronous voltage.
If the resistor keep bleeding and always stay heat emission no matter charge or not charge, then you must double check the connection.

Ok, you talk connection from little cables (balancer cable or the nickel welder between the battery?

 

[dogman dan]

A bms will get warm during charging, at the input fet. And it will also get warm at the bleed resistors, when they are draining high cells at the end of the charge, including after the charger stops.

This is normal. But if any of the bleeders get stuck, they stay warm longer than they should, draining that cell group till it kills them. This is why some call a BMS a battery murdering system. Because sometimes this can happen.

If your bms stops making heat with all the cells balanced, then it's functioning exactly as it's supposed to.

 

[General_Lee]

A bms will get warm during charging, at the input fet. And it will also get warm at the bleed resistors, when they are draining high cells at the end of the charge, including after the charger stops.

This is normal. But if any of the bleeders get stuck, they stay warm longer than they should, draining that cell group till it kills them. This is why some call a BMS a battery murdering system. Because sometimes this can happen.

If your bms stops making heat with all the cells balanced, then it's functioning exactly as it's supposed to.

how many time approximately the pack will come balanced and stay cold? for now I charged my pack yesterday and now it hot yet but less.

If I charge the pack at 5 amp, is it to high? maybe the BMS work better with lower amp?

 

[eva-michael]

Resistor bleeding BMS will consume the energy of higher voltage cell by heat emission via resistor.
Generally this process will stay for a while after finish charge, because BMS will still need some time to balance all cells to appropriate synchronous voltage.
If the resistor keep bleeding and always stay heat emission no matter charge or not charge, then you must double check the connection.

Ok, you talk connection from little cables (balancer cable or the nickel welder between the battery?

Connection from little cables(small balance wires).
Double check your wiring to make sure you have not made a mistake. Use a voltage meter and check the voltage between pin(pin from can connector of small balance wires). From the 1st pin to last pin, you will see the voltage increase in
almost equal increments. If you do not, you have made a mistake. Find the mistake and correct it.
Voltage between "little cables(small balance wires)" should be equal as that should be voltage of one cell.
BTW, does this bms have led light as a working signal when corresponding cell is balanced? If yes, that will be convenient to check.

 

[dogman dan]

A pack with a hot bms 12 hours after you unplug it from the charger, is a real problem. It's bms is murdering the battery.

If you made a mistake, you could have a circuit trying to discharge 2 cells that are at 8.4v down to 4.2v thinking it's one cell. Pictures of what you did could help a ton here, if it looks like you have real trouble brewing. Also readings of each cell group when full charged.

But if your charger is overcharging the pack, and you left it overnight with the charger plugged into both the wall and the pack, the bms would then continue to try to discharge the battery, while the charger might be periodically turning back on for a few seconds an hour, charging it back up. Or it's just trying to charge a 13s pack to 14s voltage, a totally mis matched charger and bms.

But those resistors on the bms should not make the bms hot, merely warm. Hot would be ouch when you touch it, warm, like a hot cup of coffee in your hand.

Bear in mind, a warm bms can be a good thing. It tells you the pack got a balancing charge. it's not stopping undercharged, and getting worse and worse unbalanced.

A 5 amps charge can definitely make the input fet hot, even hot enough to melt shrink sometimes. But it should not stay hot overnight, unplugged. A lower rate charger would heat up the input fet less.

 

[General_Lee]

OK guys thanks for your help, I said hot but is more warm, like a coffe cup in my hand
The mosfets stay cold, just resistance from balanced part come warm. When is fully charged.
The pack with around 47v or 48v (resistor) seem to stay cold.

I wiring the pack with this plan:

http://i1098.photobucket.com/albums/g378/lilianleung/13Slogo.jpg~original

 

[eva-michael]

OK guys thanks for your help, I said hot but is more warm, like a coffe cup in my hand
The mosfets stay cold, just resistance from balanced part come warm. When is fully charged.
The pack with around 47v or 48v (resistor) seem to stay cold.

I wiring the pack with this plan:

http://i1098.photobucket.com/albums/g378/lilianleung/13Slogo.jpg~original

static state should be cool. hot coffe means resistor is bleeding(keep eating energy from cells). How long have it stay? Check voltage of all cell and see if some of them are droping.
If yes, you probably have a BMS connection issue, your cells are coming to more unbalance. Diagnose as my advice asap.
Last time, a guys who mentioned similar issue. One of the BMS led indicator keeps light and resistor keeps bleeding one corresponding cell. And find he found a order connection issue of balance wires and the result is that BMS have eat 50% capacity of this cell and he only able to reach half of the distance and then power cut off. In this type of case, we suggest him to make a full charge of the whole battery pack and use a single cell charge to charge back the 50% capacity this cell has lost.
Check and solve the issue(if there is) asap, guy

 

[General_Lee]

I tested all connector pin from 1 to 13, between all pin rise equal, around 4v. Weird!.

 

[dogman dan]

If you leave one probe of your voltmeter on the big negative, then move your positive probe down the pins, you read 1 cell 4v, then 2cells 8v and so on.

You can read cell one on the big negative, and pin one, then move the probes to pin 1 and 2, to read just cell 2, and so on.

To me, it's sounding more and more like all is normal.

 

[eva-michael]

I tested all connector pin from 1 to 13, between all pin rise equal, around 4v. Weird!.

So now resistor is cool or warm? If warm, find out which resistor come warm first.

 

[General_Lee]

I tested all connector pin from 1 to 13, between all pin rise equal, around 4v. Weird!.

So now resistor is cool or warm? If warm, find out which resistor come warm first.

sunday I took a ride with my bike, when I reached around 48v I store it. This morning I checked the voltage and the pack do not drop, stay at 48v. I lose anything.

All resistors seem to come warm when I charge the pack

Internal resistance cells, this is possible causes?

 

[999zip999]

How did you build your pack. Did you put all cells in parallel to a set charge ? Meaning were of cells of same voltage so as not to over work a new bms. Yes start with a balance pack. Are these new real cells ? Watch pack and check cell voltage.
1. 3.98v
2. 3.99v
3. 4.09v

12. Xxx volt
Write it down on a piece of paper so you can remember and compare. Important.
You put all cells in parallel to make sure all are same voltage the charge to 4.0 v then hookup. You can get lucky and get all new cell close to same voltage.

 

[General_Lee]

How did you build your pack. Did you put all cells in parallel to a set charge ? Meaning were of cells of same voltage so as not to over work a new bms. Yes start with a balance pack. Are these new real cells ? Watch pack and check cell voltage.
1. 3.98v
2. 3.99v
3. 4.09v

12. Xxx volt
Write it down on a piece of paper so you can remember and compare. Important.

I built the 48v pack with a 72v pack, I just removed extra cells. I not charging all cells in parallel before. Maybe my error. I assumed they was already balanced or equal.

0.2v approximately, between higher and lower (sunday).

 

[999zip999]

The bms wil balance, but why work a new bms and pack. Medium discharge charge. Do the hand test. I put an extra set of sense wires to keep track of thinks, like two 6s sense wires. As I must know what's happening over time.

 

[dogman dan]

Always hard to know exactly what is happening. But it does sound to me like the pack may have started out poorly balanced, and it's doing a lot of bleeding down now each charge to get balanced.

The other thing that could be happening, is your charger is set just a tiny bit high. This means all your cells are charging to 4.22v rather than 4.2v. or whatever. This would cause all channels to start discharging once the cells read over 4.2v.

So for example, if you have 14 cells, .02v x14 would be about a volt and a half high. Check your charger voltage with a reliable voltmeter, One volt high would do er.

If all channels got hot, then the pack is balanced now. The best diagnostic is to check each cell groups voltage right when the charger shuts off, or better yet, actually watch it finish the charge. That's what the extra plug is for, so you can plug in two cellog 8's or similar device, and watch the bms do it's thing on each cell as it happens.

For a home built battery, I'd say it's darn near mandatory to put those extra jst balance plugs on the pack.