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)
Introduction, details of battery balancer system
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- Posts: 244
- Joined: Tue Dec 11, 2007 11:26 pm
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- Posts: 244
- Joined: Tue Dec 11, 2007 11:26 pm
ChrisB wrote: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
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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
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Battery Balncer Prototype
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
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
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- Posts: 244
- Joined: Tue Dec 11, 2007 11:26 pm
ChrisB wrote: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)
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