andrew, to me it seems a little crude, and you have only created 60V strings
;]
the charging will be a hurdle.also what sort of current/amperage draw are
you going to need? will these batteries cope???
Message: 1
Date: Tue, 6 Mar 2007 17:18:24 -0700
From: "Andrew Wowk" <[EMAIL PROTECTED]>
Subject: [ElectricMotorcycles] How to build and use NiMH/NiCad ideas?
To: ElectricMotorcycles <[email protected]>
Message-ID:
<[EMAIL PROTECTED]>
Content-Type: text/plain; charset="iso-8859-1"
The best idea I can come up with at the moment is to buy lots of 6-Cell
sub
C RC hobby packs and construct a pack from them. Construct modules with
enough 6-cell RC packs in series for the desired voltage. Each "module"
will
need to be charged separately from the rest; this way you are only
charging
one string of cells at once to prevent some very bad balance problems.
Example for 72v system:
Module 1:
[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell
pack]---[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell
pack]---[6-cell pack]
Module 2 wired in parallel with module 1:
[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell
pack]---[6-cell pack]---[6-cell pack]---[6-cell pack]---[6-cell
pack]---[6-cell pack]
and so forth until you have desired capacity.
This way you can buy small high power connectors (not crappy stock Tamaya)
which will allow you to easily uncouple and measure each 6-cell pack for
maintenance. Constructing the pack in the first place will be easy.
You can charge them by using light dimmers (available from hardware
store),
along with a rectifier for each light dimmer. Additionally you will need
to
disconnect the modules from each other, which could be a big pain for each
charge. You may be able to get around this by charging only half of each
"module", but this will double the number of light dimmers needed. You
will
need a temperature sensor with each light dimmer to detect end-of-charge,
and some circuitry to cut power.
The best price I can find for RC packs is these:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=89 .
To construct a reasonable pack with 30.6 ah 72v pack you'd need to spend
about $1,300 plus shipping, plus 36 light dimmers (maybe you can get a
bulk
order from ebay).
The following load test data was from a not-so-similar 6-cell 3.0 ah NiMH
RC
pack from powerstream to give you an idea of power. It should be noted
that
the above NiCad packs use a sintered electrode, so they may even do
better.
Open circuit: 7.8
V. at 30 amps: 5.83
V. at 50 amps: 5.10
V. at 75 amps: 3.174
This was with the tamaya connector cut off, as it adds considerable
resistance.
Anyone else got any bright ideas?
Andrew
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