Battery Management system design for Lipo

[Flip101]

Hey, I am in charge of building a battery bank and charging system for a hybrid vehicle for school. We went with lithium polymer batteries

Each battery needs to be charged individually. There are systems out there called battery management systems which control the charging, and monitor the discharging as you drive. I will also need a special lipo charger that will balance the cells, which needs to be done periodically as maintenance. I will need to make one (BMS, and possibly balancing charger)..

I am wondering if you would beable to send a battery management system design that could be implemented with the GBS-LFMP40AH. The reason I am asking you this is because it is outlined in the operators manual that the BMS design should be verified with the manufacturer otherwise damage can be done to the batteries.

 

[Philistine]

I will let the experts chime in with the response, but Lipo BMS's are probably the most difficult BMS area, and in some ways the holy grail on this board. As far as I am aware noone on this forum agrees on a reliable effective out of the box large scale BMS for Lipo (as would be needed for a car EV lipo pack), but I could be wrong.

 

[nechaus]

I would not put kids in the car with lipo..

lifep04 yes..

 

[jonescg]

Seems the best option for LiPo 'management' is to simply have a high and low voltage warning circuit for each cell, and leave it at that. Always leave the option of balance charging as convenient and accessible as possible, and do it regularly if needed.

 

[amberwolf]

You might want to look around a bit (using google's site search) here on the forums for the various threads on attempts to develop BMS for various types of batteries. THere have also been BMS projects (some finished, some not) on DIY Electric Car forums, also with useful information in their threads.

From what I have seen watching the development of some of those, it is not easy to do, and there are quite a few problems you would never expect to have that may rear their heads in actual use that don't seem likely during planning.

Not many BMS projects seem to get very far along; I'd hope that yours can be finished, but you might consider using existing solutions at least as either a start or as modules of what you want to achieve.

One of the ones I know of directly is a simple HVC/LVC by Methods, available in the Online Marketplace section of the forums. Was designed specifically to be built into RC LiPo packs, to prevent overdischarge or overcharge.

Methods also has a full-fledged BMS developed and used on electric race motorcycles, but you'd need to contact him directly about that to see if it's currently avaialble, or details about it.

 

[bigmoose]

I second amber's recommendation for what you want. Contact ES member methods and talk to him about his LTC BMS availability. It will do what you need. It is a quite capable BMS based on the LTC 6802-2. Search the site for it, there are some screen shots posted of the labview GUI and the hardware modules.

Methods also has a full-fledged BMS developed and used on electric race motorcycles, but you'd need to contact him directly about that to see if it's currently avaialble, or details about it.

 

[pdf]

http://endless-sphere.com/forums/viewtopic.php?f=14&t=26554&start=570

 

[999zip999]

There are more bms systems for LIfepo4 and safer, school let you go with lipo ? High c-rate and a lot of other pluses.

 

[amigafan2003]

I would not put kids in the car with lipo..

lifep04 yes..

But you'll put them in a car with 18 gallons of highly explosive liquid fuel just behind the rear seats

 

[dequinox]

Puts new meaning in the term "firewall"... :lol:

 

[dnmun]

i don't understand why you decided you had to charge them individually. you can use a regular lipo BMS to charge and discharge the lipo pack through. it will balance the pack and provide output short circuit protection and protect from over discharge. so why does it have to be so hard?

do you know how big the battery will be and what cells you will use? what kinda discharge currents?

 

[friendly1uk]

You don't have the basic principles yet. Telling me you have not searched at all, or your not competent. It would be irresponsible of me to get involved.

From what you have said, you shouldn't take on this project. I know people here could do the whole thing for you, but that would make you our remote controlled robot, which is not how to build stuff like this for kids. We could even be seen as liable.

 

[wesnewell]

I really get a kick out of all these post. None of you have a clue as to what he's using even though he list the part number GBS-LFP40AH in his post. I would have thought thought the LFP in the number would have been a clue for some of you geniuses. I guess not. It's lifepo4, not LCO. For the original poster, you might want to consider this when taking advice from these people. Here's the battery he plans on using.
http://www.gbsystem.com/products-show-en.asp?id=40

 

[dogman dan]

Good catch Wes. You actually looked up the cell.

But lico or lifepo4, I do dispute his thinking that each cell needs to be charged individually. They can be, but its not a must be thing.

I think it might be easier to do though, to just have individual chargers than to have a huge bms.

Could he still use a smaller bms for monitoring? Have the bms lvc trip a larger contactor that shuts off the whole pack?

 

[amberwolf]

Sorry; I assumed from the OP's wording/etc that he was using LiCo type LiPo, and didnt' look up the cell itself; plus most of my advice was intended to point to sources for design help since the title implied he was going to design from ground up.

 

[wesnewell]

I got the impression he didn't have a clue as to what he's doing and wanted someone to do his work for school for him.

 

[parabellum]

Are you debating on old 2012 tread or I got something wrong?

P.S. OP has not posted for 2 years.

 

[agniusm]

He he, good one. Ze ghost thread