BMS's i get sick of it too understand what the problem is

Joost · Mar 31, 2017

Dear forum friends,

As the topic say I'm get sick off the BMS problems that shutdown the battery!!!!!

Is there some kind of information or book where I can learn about bms's??
I'm not a electronic guy but want and need to learn solving problems.

Where Can I find it?

I'm not the only one with this problem???

Joost

Matador · Mar 31, 2017

My guess is one of your battery string might not be well balanced. Maybe one string is way below average cell voltage. So when that weak group hits LVC it triggers down the whole BMS to shut down in order to protect the battery from over-discharging some cells. That's my guess but maybe more details as to how it happens may help in the diagnosis process.

Joost · Apr 2, 2017

Thank you for your answer.

The battery pack holds 2x 13s8p li-ion cells.
Every part has its own BMS. Too charge the battery pack I connected both BMS on one charge input.
The problem came after I charged every group on both parts. After finishing it I took a drive around 15Km. Then I hook it on the charger 54,4V 2A. It starts charging without problems.
The next day I disconnected it and want too make a test drive. I could drive 1Km and shuts down.

With your suggestion in mind i think it is a balancing issue.
On YouTube is saws a video about bottom balancing.

Are here people who have experienced with bottom balancing?

999zip999 · Apr 2, 2017

You start by knowing the state of charge your battery. So write on paper the voltage of each cell like this.
1. 3.85v
2. 3.99v
3. 4.02v

13. Xxx volt
This is where to start. Post here.

Joost · Apr 10, 2017

The problem is unbalanced cells. Li-ion charged at 4,2v

neptronix · Apr 11, 2017

Much like a car, it's hard to fix a problem without knowing what could cause it.
A properly designed BMS will shut down pack output when one cell has hit too high or too low a voltage.

A pack that cannot handle the load will cut off early.

What are your per cell measurements when the pack has shut down, and how far does the voltage drop between the time you have the throttle at 0% and the bike is at full load ( IE climbing a hill or accelerating ) ?

amberwolf · Apr 11, 2017

Joost said:
The problem is unbalanced cells.

If you already know the problem is unbalanced cells, then you should fix that, because the BMS is just doing it's job of protecting the cells against overdischarge or overcharge.

Either let the BMS balance the cells or manually do so, then check under a load (acceleration or hill climbing, or simulated load (see "load tester" in various threads around ES, including things like "heater coils", lights, etc).

Then replace the cells that wont' stay balanced, or that sag more than others under that load.

That will fix the problem of cutting out under load.

For more understanding about the problem you are having, look around at the dozens (hundreds?) of battery troubleshooting threads.

Ykick · Apr 11, 2017

Folks who wanna learn more about these sorts of battery systems often find RC planes, heli’s, cars, boats a great way to have fun while learning key basic fundamentals.

I’d find a model type you might like then outfit with RC balance charger and Lipo packs. Dig in and have fun while you get an education about manually managing series cell groups. Aided with a little equipment you become the BMS which is the best way IMO to learn how BMS are supposed to work...

neptronix · Apr 11, 2017

No kidding. Watching the cells do their thing on an iCharger 1010b+ using logview on my PC taught me half of what i know about batteries. Simply an amazing teaching tool.

A BMS is basically the opposite. It's a circuit board with some wires coming out of it that tells you nothing about what decisions it's making or why it's making them.

neptronix · Apr 11, 2017

neptronix said:
No kidding. Watching the cells do their thing on an iCharger 1010b+ using logview on my PC taught me half of what i know about batteries. Simply an amazing teaching tool.

A BMS is basically the opposite. It's a circuit board with some wires coming out of it that tells you nothing about what decisions it's making or why it's making them.

At least getting some measurements of voltage sag and amp hours delivered from a turnigy watt meter or equivalent device is a start on figuring out what the hell is going on with a BMSed battery.

k-harvey · Apr 15, 2017

My first troubles with lithium batteries were BMS being the cheapest was only for low current & needed a higher current BMS . I've replaced heaps because of this.

Joost · Apr 21, 2017

Hello again,

After many tries too read and write too the smart BMS with many different dongles I bought the expansive smartBMS own sub O2Micro i2c dongle.

I tried:

RUSB3410
Pikkit icd 2
Profilic 23xx
Ftdi rs232
Rfduino

Nothing worked. All of the dongles has not the good vid id. Is there a way to manipulate drivers under Windows too fake the cowboy oz890 program?

Joost · Apr 28, 2017

Solved!!!

It's the Smart BMS.... I have another one but I'm scared too use it. I don't want to loose another one.....

BMS's i get sick of it too understand what the problem is

Joost

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Matador

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Joost

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999zip999

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neptronix

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amberwolf

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Ykick

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neptronix

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neptronix

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k-harvey

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