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Re: (ET) Time for a NiMH Elec-trak - Amp hours



Actually the cheapest way to charge NiMH is to just charge at .1 C for 15 hours. That's apparently low enough to not boil the batteries, yet enough to charge a long string.

If one wants to charge faster, one needs to use either the saddle method or a good temp sensor to detect fully charged. I think the Prius uses the second method, and that's what I'm probably going to go with. It should be a snap to take a Basic-Plus STAMP computer and wire it to 100 temp sensors, one per battery well (prismatic batteries include a dimple in the top for the install of a temp sensor. Nice of them)

Plus most NiMH batteries are made in China to the lowest bidder specification (ie: garbage). These batteries apparently are better.

We'll see what happens.

Chris



Tim Humphrey wrote:
I may be mistaken, but I think that the temp sensor in Nickel chemistry 
batteries is there because it's the easiest,
cheapest way to tell the charger when to shut off.

What they do is assume that if the battery is heating up then it must be 
full, so they shut off the charger. That's
why you don't get very many cycles from your cordless tools batteries. 
Constantly overcharging Nickel cells shorten
their life. But a proper charge algorithm would add cost to the tools, and 
we Americans are generally penny wise and
pound foolish and would gladly pay less up front and replace the battery 
pack three times as often.

Everthing I've read, generally "sums up" that Nickel or even Lithium 
chemistries want to be left in a state of
discharge for maximum cycle life, just the opposite of lead chemistries.