|
For loose cells and custom battery packs click here:
For a chart of the sizes and weights of cylindrical batteries click
here:
For more battery
engineering resources click here:
Custom design and manufacture of
state-of-the-art battery chargers, UPS, and power supplies for OEMs in a hurry! Pack Design
Considerations
"Ladder", linear, F
type, or radial
Note
that the electrodes will both come off the top when there are an even number of cells, and one
off the top, the other off the bottom when there is an odd number of cells. With a connector
and heat shrink wrap they look like this:
The size of
a linear pack is roughly calculated by the formulaD x nD x
H where D is the diameter of the cell,
n is the number of cells, and H is the height of the cells.
Multi-row cells
There are two
ways to start packing them. One could be called the cubic, and the other face centered cubic,
or nested.
Cubic packing is in neat rows. The size of such a pack
is nD x mD x H, where n is the number of cells in a row,
m is the number of rows, D is the cell diameter, and H is the cell height. 
Face centered
cubic packing is nested to take up less room. Calculating the size takes a little geometry.
The size is L x W x H where
L
= (n +½)D
W = [0.866(p-1)+1] D
H=H
p
is the number of rows wide.
If there are alternating long and short rows, such as the
3,4,3 ten cell pack, the formulas are
L = mD
W = [0.866(p-1)+1] D
H = H
Where m is the
number of cells in the longest layer, and p is the number
of layers. With heat shrink it looks like this:
For a 3 cell pack, you can put the cells in a tube
The diameter of the outer circle is
2.16 D.
For a four cell pack in a circular
tube
The diameter
of the circumscribed circle is 2.41 D.
Advantages:
 NiMH batteries are smaller and lighter than lead acid
batteries, making them a good choice for high performance bicycles and scooters.
Over 80% greater run time versus lead acid of the same
size.
Sustained operating voltage makes the scooter seem to have
a fresh charge over most of the operating time. Lead acid voltage sags continuously over the
discharge curve making the scooter slower through most of the run time.
Also available in custom voltages, sizes,
capacities, and configurations. This is PowerStream!
Low cost
compared with other NiMH manufacturers.
We set out to design a
drop-in replacement for lead acid in personal electric vehicles. This is a smaller, lighter,
better performing replacement, but with a premium cost.
Data:
The following comparison
tests were done with a 24 volt "Amplifier" electric scooter:
| |
Lead Acid |
NiMH |
Improvement |
| Battery Format |
2 x 12V SLA Batteries |
20 x 1.2 V D cells |
|
| Rated Capacity |
8 AH |
8.5 AH |
|
| Battery Mass |
5.5 kg (12 lb) |
3.4 kg (7.5 lb) |
40 % lighter |
| Battery Size |
12 x 2.6 x 3.7 in. |
10.2 x 2.4 x 3.6 in. |
24% less volume |
| Maximum operating current
(note 1)
|
29.8 Amps |
30.1 Amps |
|
| Average Operating Current
(note 1)
|
11.1 Amps |
10.6 Amps |
|
Total run time
(note 4)
|
27 minutes |
46 minutes |
70% longer |
Reduced Performance
(note 2)
|
21 minutes |
35 minutes |
66% longer |
| Loss Performance
(note 3)
|
24 minutes |
45 minutes |
88% longer |
| Test differences |
Multiple rest cycles |
One rest cycle |
|
| Test differences |
Total run time includes three loss of power events with rests
in between |
Test terminated upon the first loss of power |
|
Notes:
1)156 lb test engineer on residential/business
area test course, almost constant slopes up and down
.
2) Indicated time is the first instance of a
noticeable loss in performance
.
3)
Indicated time is the first instance of a complete loss of performance
4) Total run time is greater than the loss of
performance time because the scooter was run again after a rest without
recharging.
|
