Some calculations related to battery temperature and cooling

[Rush]

My understanding of how and when the fan turns on and off is very limited. I'm told that the fan comes on at about 104 C. Here in this AZ hot weather, when I get home I plug the fan into a 12v circuit and let it run an hr or so. 2 days ago the pack was at 110 C, ambient at 96 and it took about 2 hrs to cool the pack to ambient.

What about a differentialy controller where the if the input temp sensor is less than the output, the fan turns on until both are equal?

What happens if the fan leads are disconnected from the relays? Does that provide an error message?

If the fan is supplied 12vdc from the 12vdc battery while the car is in operation, does that send an error?

[IamIan]

Originally Posted by MN Driver

E27006, Most NiMh chargers implement a good deal of overcharge though,

I'll agree with this as well.
Of course some are better than others.

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Peukert is also worth keeping in mind.

The harder you push a battery the less you will get from it... although most of the lost Peukert capacity is not really lost ... it just takes some time for the chemical reactions in the battery to catch up ... which is why if allowed to rest for a little while a bit more can be pulled out later... Old time EVer call this 'Growing Amps'

Even if the Ah are not lost ... and even if the % of battery cycle efficiency was not reduced ... there will still be a delay ... due to the chemical reactions slower rate compared to that of the electronics.

For the same reason you can't just cook a turkey in 1/2 the time by using 2x the heat... you will get very different results from the chemical reactions the faster you push them.

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If you are considering a more 'maximized' fan usage system ... It might be a good idea to go with the hottest part of the pack as your sensor point ... that would be the worst case ... and it will also be worth keeping in mind that the pack will not cool evenly once you do turn the fan on.

best of luck.