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Topic: Battery Pack, individual cell voltage measurement (Read 4 times) previous topic - next topic

retrolefty


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op-amp that has a very high common mode voltage rejection rating


I thought about something like that, but it requires much more circuitry [45 opAmps,
plus etc] than the other approaches. But would be very good for a few sample points
only.


Or just one with a 2 pole 45 throw switch ahead of the opamp. This could just be 45 DPST relays that you select one at a time to route the selected cells terminals to the single opamp.

Lefty

oric_dan

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45 DPST relays


On the other thread you mentioned old style CMOS chips. There was also a time
between vacuum tubes and transistors that they used relays for computer logic gates.
I imagine your 45 relay design would sound something like one of those computers,
:-). The reptiles might go crazy, LOL.

Graynomad

#17
Dec 02, 2012, 12:30 am Last Edit: Dec 02, 2012, 12:44 am by Graynomad Reason: 1
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Check out the linked pdf doc.

Wow, +-250V CMRR. That's impressive.

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separate Arduino processors, powered at different points in the battery chain, and each reading 6 A/D channels,

I also was thinking about this overnight. I thought that my above design could be modified to handle either 6 batteries (although 6x15v is getting too high for good resolution) or maybe "12 volts"  where that is made up of various combinations, 6x2v, 3x4v, 2x6v or 1x12v.

You would then hang boards at various location on the battery string as required. In the case of this thread's application that would mean 3 batteries per board or 15 boards, maybe as few as 8 if you up the range per board.

Another option it to incorporate a special monitor chip like the 12-channel MAX11068, they can only handle 5v per cell which is no good for me but would work here. Also there's the LTC6802.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

mauried

The off the shelf battery management system that is failing, is it a balancer type system or just a battery monitor.
A balancer type does more than just measure individual cell voltage.

PaulS

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Or just one with a 2 pole 45 throw switch ahead of the opamp.

Can you get those at Radio Shack?

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