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Originally Posted by 300TTto545
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Now as far as dV - that would seem to be pretty easy. If you use a standard "trickle" battery charger - do they typically have a dV sensor? I would think any good charger would have this - yes?
I know - getting to the right voltage, checking dV and tying into a temp sensor - will probably take enough time and money that I should wait for the manufacturers to do it.
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The NiMH batteries have a 5 mv, dV drop that needs to be detected but that is per cell. In the Prius, we have six cells per module so that means detecting 30 mv drop for a voltage that will be around 8.5 VDC at the peak. That means your voltage sensor has to detect going from say 8.50 to 8.47. This means a quality voltage measurement system, at least 3.5 digits but 4 would be better.
Also, you want to stop the charging for each individual module or series of cells when _THEY_ show the 30 mv drop. This of course assumes the six cells within the battery module are fairly balanced and that is a bad assumption when the battery module has lost a significant amount of water from the electrolyte.
The temperature probe is the backup system and it is critical in case the cells become unbalanced. The failing cell will increase the temperature and this higher rate than normal charging means _STOP_!
I'm not trying to be an alarmist but emphasize the importance of a good design that is as solid as possible. A weak design with significant noise would be unreliable and might result in "bad things."
Bob Wilson