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Discussion Starter · #1 ·
On eBay, I found this: Battery Voltage Monitor
Which is a single, 3 colour LED driven by a PIC microcontroller which changes colour and flashes according to the voltage it's seeing.

His web site is not quite operational yet - but says it will be soon: http://www.sparkbright.co.uk/

On the ebay shop, it says he is happy to re-program the controller a little if the customer wants - which set me thinking!

I emailed the guy who runs the shop, Andrew Ferguson, to ask if there were any spare pins on the chip and if he could program one to go high when the voltage exceeds 14.7v and the other for 14.6v (two most common SLA charge voltages).

OK, the outputs would need to be amplified a bit to drive a relay / power transistor to then drive a shunt across the battery - but that at least is simple to build.

I thought it would be nice to have 15 LED's on my dash showing individual battery status - but also act as a top balancing system.

He says the chip will operate down to 2v - making it similarly suitable for Lithiums. Likewise he was happy to program it accordingly.

My Volt-Blochers have worked very well and now have 300 charge cycles on them. It's only a shame that they are no longer available. OK they are simple to build yourself - but if you build everything yourself, your EV will never be finished!

I don't know what the thermal voltage stability will be like (how good the on board reference is) but it's got to be better than the variable resistor used in a Blocher!

His email address is on his web site / ebay shop. PM me if you can't find it.

I have no connection with these, other than being a potential customer!

Si
 

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This idea seems good to me. They are expensive though, maybe not ideal for Li, when you have so many cells. I would like to read about those "blochers", have never heard of them!

Can you BOTH drive a relay/FET and show the voltage of the battery at the same time?

EDIT: Just read about the blochers!
 

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Discussion Starter · #3 ·
It seems you can have, in addition to the LED, another two lines which can be programmed with whatever behaviour you want!

I was impressed at how small the board is, about the same size as the LED!

Si
 
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