Introduction, details of battery balancer system

[ChrisBarron]

Hello,
Prompted by member QDos to start posting here, I would like to point out that I am about to start building a battery balancing/BMS system, the details of which can be found on my blog
http://journals.aol.co.uk/fixitsan/elec ... -building/

I didn't intend to make something so elaborate as that which I have planned, but to be honest I think if you have access to individual cells within a battery you are as well balancing on the individual cell level. Another benefit is that the hardware should be able to manage Lithium Ion and other flavours of battery. I should be posting a schematic in the next few days.

Hello again !
Chris
(Nr Edinburgh)

[qdos]

Great to see you aboard Chris I'm sure there's going to much interest in your postings here So a hearty WELCOME

[ChrisBarron]

Great to see you aboard Chris I'm sure there's going to much interest in your postings here So a hearty WELCOME

Thanks for the welcome, if anyone has any questions about what I'm up to just ask the question....the only silly questions are the ones we don't ask, as they say !

[ChrisB]

Hi Chris

Love the BMS and love the blog, I presume the chap who you have spoken to about installing them in a Bedford CF would be our very own "Green Machine" member then

ChrisB

[ChrisBarron]

Hi Chris

Love the BMS and love the blog, I presume the chap who you have spoken to about installing them in a Bedford CF would be our very own "Green Machine" member then

ChrisB

I'm not sure who it is, I spoke with them about a year ago, adn have had to install another hard drive since then whcih meant I lost all previous contacts, what a nightmare that can be !

All I recall was that the van ran well and that the owner got a good deal on their cells too. They're not designed for this purpose but their specs are very strong.

Chris

[EVguru]

You should take a look at;

http://www.geocities.com/sorefeets/balancerland/

[ChrisBarron]

You should take a look at;

http://www.geocities.com/sorefeets/balancerland/

Thanks, yes I was looking at it last week.
The idea I use is basically the same as Lee Hart's, except instead of using one DPDT relay for each battery, I use n+1 SPST relays, where n is the number of cells.

Lee's system is for balancing 12v batteries. I would use a 12V system if I did not have access to individual cells, but because most batteries end up being let down by just one particular cell I see some sense in giving each cell particular attention when you can access them individually.

I'm hoping I will also be able to adapt the topolgy for lithium and NiMH cells in the future, so gettting down to working at cell-level now may hopefully pay off later.

Chris

[ChrisBarron]

Just put a video on Youtube with details of my battery balancer prototype, at
http://www.youtube.com/watch?v=tlnbSwkpMcc

The project schematics are available at...
http://journals.aol.co.uk/fixitsan/elec ... -building/

More details and progress soon , hopefully !

Chris

[ChrisBarron]

Hi Chris

Love the BMS and love the blog,
ChrisB

I've just updated the blog with some pictures, trying to show that it needn't be a complicated system to build using off-the-shelf parts

There are also some details of possible new functions, which I would appreciate comments on.

The first is a remote control pager receiver type of device which would keep the user up to date with the progress of the BMS. It would only be a short range radio device because I'm not fully au-fait with bluetooth and so on. I think I might find it useful to have something inside my house which saves me having to go outside to see what the BMS is doing.

The second function is a graphic lcd display with 128 x 64 pixels, which would give a bargraph display of each cell's voltage, giving that all important 'at a glance' information.

I'm also considering moving up a scale to a DSP microcontroller which has a greater resolution of A/D, 12-bits instead of 10-bits. In short, that mean the possibility of getting a resolution of about 6mV when dealing with 6 lithium cells with a nominal voltage of 4.2V per cell, which in turn means that the BMS could detect the difference between cell voltages of 4.222V and 4.228V which I believe is good enough to be able to call it an accurate system where Lithium Ion ( /polymer etc) is concerned, and the cost would only be marginally more.

Just as a ballpark figure my current costs are up to about £3 per cell (includes some discounted special offer components)

I hope to get around to plugging this lot into a pack of 18 cells within the next two weeks, and I'll let speak more about it then. (!)

Chris

(Blog details are on the link in my signature)

[qdos]

sounds great stuff Chris how about writing up an article for Plugged In magazine?