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ASSEMBLING PACKS
When you order your cells, it pays to get an extra one, and an
extra plastic building block and a couple of extra bus bars. You may break or
damage a part or may get a bad cell. Its unlikely but not unknown.
MATCHING CELLS
The very first thing you need to do when these new lithium cells
are received, is to fully charge them in parallel, (with + ends connected
together, and - connected together) in groups of say 5 or 10 or whatever is easy
to manage. Charge all the cells, as soon as possible, as per below, and then
immediately disconnect them after removal from the charger so that each
individual cell is loose.
How? Charge the groups set to LIFE 3.600v as a big single cell
with the Hyperion and then allow them to stay connected AFTER charge for say 2
further hours. The charger continues to charge AFTER the end point slowly. The
reason for this is that we need to be sure that they are "soaked" at this 3.600
VOLT and FULLY charged. The charger maintains the voltage after the charge ends
for a long time and it allows them to fully soak up the last few percent of
charge. Then immediately disconnect every one and put them all in a big
box, put it away somewhere for as long as possible, but at LEAST 2 weeks. 6 is
better!
We are trying to ascertain which cells SELF DISCHARGE the most.
This is the single most important thing that screws up cell balance. Use
(discharging) doesn't. Charging doesn't. Self discharge does dramatically...
We need to be patient and wait as long as practicable. At LEAST 14 days!!!
Longer is better.
Then, with the Hyperion charger connected to a PC, Set to 12Ah,
3.600 volts, charge every separate cell individually until the charger says
done! Read off the EXACT mAh RETURNED to the cell, and using a marker pen add a
cell number and the figure. So say: 1 and 0.677mAh. Next cell 2 and 0.456mAh
etc, etc,...
We then need to assemble the cells into 8 groups of 9 cells (for
the group 24 sized battery) with the same AVERAGE discharge rate. This is easy!
Just add up all the Ah and make sure that you have low ones, and high ones in
each group that add up to the same amount! As closely as possible. Being good at
maths helps. Lots of trial and error with a calculator and sheet of paper works
too... My way!
Don't mix these up! You want to end up with 8 boxes with 9 cells
in each. Each box should add up to the same (or close) figure...
IMAGES TO BE ADDED...
BUILDING THE PACK.
The building blocks are sort of self explanatory. You need to
make 2 sides with 6 cells high, 6 cells long for each 12v battery. Or 5 cells
high and 6 cells long, with some missing on the top for the smaller group 34
sized pack. See the images at the top of the page. The best way to do this is on
a solid surface with a small hammer and a cloth to protect the plastic. They are
a very tight fit!
Don't add the actual cells yet!
Study the drawings at the top. You need to make sure you fit them
the correct way around, and in the groups that you have already separated them
into (above in 8 groups). assemble these laid flat, with the cells stood
upright. Again you will need to add all the cells, then tap the side on with a
hammer and cloth. DO NOT add the bus bars yet!
TO BE CONTINUED
In a month or so I will add more to this page, as I intend to do
exactly this and build two batteries for a stock powerchair and will photograph
every detail as I go along. A picture is worth a thousand words and all that.
But really its simple.
For more info right now, go to the
Message
Board
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GUIDE
TO CONVERT A POWER WHEELCHAIR TO LITHIUM BATTERIES
BUILD
BATTERIES
The same thing with the smaller
(lower) battery below: