# Building your own battery management system?



## SciTech02 (Jun 21, 2008)

I was pondering that if you can build your own speed controller (microcontroller based or even with a 555 timer IC), should it be possible to create your own BMS as well? I've heard they can be quite expensive and are necessary when using multiple battery cells (such as Li-ion battery packs). If you had the technical know-how, it seems you could save a good deal of money. Has anyone here tried this?


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## TX_Dj (Jul 25, 2008)

That is more or less the origination of said devices. The first commercially available BMS I became aware of was designed by Rich Rudman several years back, they're called "Rudman Regs" or something like that.


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## aeroscott (Jan 5, 2008)

I'm trying to put parts together for bms


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## judebert (Apr 16, 2008)

Rudman regs are awesome, especially combined with a PFC charger. If you're truly going DIY, though, check out the Lee Hart Battery Balancer. It balances batteries while charging and while driving. Basically uses a DC/DC converter and some relays to charge the battery with the lowest voltage; checks the voltage of all batteries each configurable interval.


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## frodus (Apr 12, 2008)

judebert said:


> Rudman regs are awesome, especially combined with a PFC charger. If you're truly going DIY, though, check out the Lee Hart Battery Balancer. It balances batteries while charging and while driving. Basically uses a DC/DC converter and some relays to charge the battery with the lowest voltage; checks the voltage of all batteries each configurable interval.


its one of the best AND cheapest designes because it balances... no other series charging system does that. It also lets your batteries settle a little and cool off while charging, because each one is charged one at a time.

I'm working on a BMS right now, kinda like a mix of Lee Hart and a PFC frontend...still need to program it


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## aeroscott (Jan 5, 2008)

frodus said:


> its one of the best AND cheapest designes because it balances... no other series charging system does that. It also lets your batteries settle a little and cool off while charging, because each one is charged one at a time.
> 
> I'm working on a BMS right now, kinda like a mix of Lee Hart and a PFC frontend...still need to program it


A friend said that the cell balancing didn't work because of the small difference in voltage wouldn't create a charge . I hope he's wrong . anybody heard this ?


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## frodus (Apr 12, 2008)

clarify that?

why wouldn't it balance? It senses the bat voltage, and charges accordingly.


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