# [EVDL] Latest EV stuff on www.HackADay.com



## EVDL List (Jul 27, 2007)

What I understood from others (that did use Prius packs in a 
full EV like US Electricar S10 truck) is that NiMH can be
parallelled for discharge safely, but not for charging.

Trouble during charging of ANY battery, especially when they
are so physically separate like independent Prius packs, is
that the battery which is full first will start to warm up
from converting current to heat.
If charge voltage drops with temperature, then the hottest
battery will get the most current because it is lowest in
voltage, *even* if it is already completely charged.

This process can escalate with enough charge current and
destroy the pack that is hottest, the process is called
thermal runaway.

Charging with low current (less than 1A per string) and
good ventilation (so all stay close together in temp) can
avoid the runaway and still allow an overnight charge,
because the Prius packs are only 6.5 Ah.

Hope this clarifies,

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Steven Ciciora
Sent: Thursday, May 08, 2008 5:03 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Latest EV stuff on www.HackADay.com

Hack-A-Day is my favorite web site I try not to read... ('cause I get sucked in for hours). Today they had a few interesting EV related hacks. Here is a link to some electric motorcycles that were at the latest Make faire:

http://www.hackaday.com/2008/05/07/maker-faire-2008-electric-motorcycles/

Here is a link on how a guy took 3 more stock Prius packs and put it in his Prius, and made a controller that goes between all 4 packs and the car for a plug in prius conversion:

http://www.hackaday.com/2008/05/07/hack-your-prius-with-prius-batteries/

He says that "(And yes, like Lithium, these prismatic NiMH cells take well to parallel operation, unlike many others.)" Which is news to me. Anyone else hear this before?

- Steven Ciciora


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