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Old 03-12-2015, 05:31 AM   #1 (permalink)
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Join Date: Aug 2010
Location: Oregon
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Acura TSX - '06 Acura TSX
90 day: 28.24 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 57.64 mpg (US)

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Need a new LiFePO4 Battery

I'm an idiot.

I swapped out the OEM 45Ah 12v battery in the Prius with a 4.2Ah LiFePO4 battery to test the charge/discharge efficiency vs the stock battery and see if it's a suitable replacement. Then I decided to explore Techstream (Toyota diagnostic and service tool) with the car on acc mode (accessories on, but power off). I spent half an hour with the door open and the radio on while looking at the various settings I could change. I turned the annoying seat-belt warning for the passenger seat off.

Then suddenly the radio cut out. I was confused for a moment, and then realized I had probably drained the small battery too much. I hit the power button to turn the car on and begin charging the 12v battery, but it was too late. There wasn't enough juice to turn the car on.

By the time I got to the battery and disconnected it, it was very warm and puffy. The meters I had connected to it showed 6 volts; not good!

After attempting to balance charge, one of the cells won't come up to proper voltage. The other 3 cells appear to be fine, but cell 1 appears to be fatally wounded.

Now I'm looking at replacement options, and I'm pretty sure I want to go with a modular design, such as prismatic cells, so that I can replace weak cells. I'd be interested in anything from 4Ah to about 20Ah.

Any recommendations on where to get the best price per Ah? I realize I'm not going to get any discounts by purchasing only 4 cells, but I figure someone on here would know of a good place to buy.

So far I'm leaning towards 20Ah prismatic cells from batteryspace.

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