Battery Diagnosis

[gaetano.sciacovelli]

Hi everyone,

we are developing a BMS that use Smart Battery System. So we are able to read a lot of data coming from the battery (single cell voltage, temperature and so on) " http://www.sbs-forum.org/specs/ " .

What I need to understand is what are the most common problems in Li-ion battery, and what type of information or tools are needed to perform a good diagnosis of the battery. In such a way I can use my BMS as a tool for a better diagnosis.

Thanks.

Gaetano

 

[amberwolf]

There's lots of battery troubleshooting threads (and some info on the wiki) that have the information you're after. Some searching and reading should help you find that info.

 

[gaetano.sciacovelli]

What I know it is that in most cases, even if only one cell is dead, it is preferable to change the whole battery, because it is difficult to change the single cell.

I cannot find information regarding what kind of info (single cell voltage, temperature, how many time the single cell has been overcharged and so on) I need to have a complete view of the status of the battery.

Thanks.

 

[gaetano.sciacovelli]

For example is it important single cell impedance for a fault diagnosis ?

 

[dogman dan]

I think it should be made easier to charge a single cell myself. To achieve that, I put a second set of balance plugs on my pingbattery. One set still goes to the bms, the second set is where I can read voltages, and apply 2 amps or less of current to charge a single cell if I need to.

Re features to add to your bms, low voltage notification might be real nice.

A beep or beep and light that lets you know when approximately 80% discharged voltage is reached might be real nice. Then some real shreiking when you are about to hit LVC.

A beep or beep and light that lets you know when one or more cells is significantly out of balance with the others would also be cool. Harder to do that of course, but it would be good to know. That can be done in your head of course, if you have display of all cells individual voltages.

 

[amberwolf]

I cannot find information regarding what kind of info (single cell voltage, temperature, how many time the single cell has been overcharged and so on) I need to have a complete view of the status of the battery.

If you want it to be "complete" then you would need to track all parameters of all cells all the time.

Otherwise, you will need to choose which things are important to you and what you intend to have your system do something about, and monitor those. Each battery/cell manufacturer should have a list of specifications that shouldn't be exceeded, and you could use those as a starting point, but each cell brand/type is going to be different.

 

[gaetano.sciacovelli]

I am not a battery expert yet.... .. I am trying to become ... Considering the most typical problems that happen to a Li-ion electric bike battery, I would like to know what kind of parameters could be useful for a technician to do a diagnosis....

We are trying to implement two kind of diagnosis : a rapid diagnosis that could give a first overview of the problem, and after that a more accurate analysis that colud give all the information to understand the problem.

Thanks for your help.

 

[Ykick]

Best way to learn about battery packs is to use them. Get yourself some Hobby King stuff and a bike and have at it. you'll learn much more doing than talking.

 

[wesnewell]

Most common problem with all battery packs are stupid, ignorant, lazy users that don't pay attention to what they are doing. I've shorted packs a few times by getting in a hurry and not paying enough attention. But I've never neglected a pack. I think that's the major problem. I've never gone more than a few days either using or checking it. Properly maintained, even an rclipo pack will last years, Neglect it, over discharge it and it could be ready for for the recycle bin in hours.