Convert a Power Wheelchair to Lithium Ion
Phosphate Battery Power
Are you looking for "Lithium" batteries to
replace your existing 22NF or GROUP 24 Gel or AGM batteries?
It can be done properly with
HUGE benefits in range, charge speed + battery service life.
CONVERT YOUR POWERCHAIR TO LITHIUM
its NOT a simple swap from your old lead based
batteries to modern Lithium batteries.
If you are searching for "group 24" lithium monobloc batteries
that look like your familiar lead acid batteries, (for e.g.) it is very unlikely you
will find any of them suitable for a bunch of quite serious
reasons discussed later. Even though they are available as shown in the image
There are actually quite a few manufacturers trying to provide
a simple "swap" with standardised group 22, 24, 34, 27 batteries that is
familiar to users of old style lead batteries. But these are (as of Nov 2011)
not any real use in a hi end powerchair.
powerchairs for e.g. DO already use safe, Lithium
Ion Nano Phosphate batteries (But NOT monobloc batteries.) with MASSIVE
benefits. Not least of which is all day (or all week!) use, even with a
real world 45 mile range between charges! And a 10 year expected service life.
So, why not use today's Monobloc
"replacement" lithium group 24 or 22nf batteries?
cannot be done today in 2011 with a pair of "replacement"
12v group 24 lithium monobloc batteries as seen in the image above at top of
page. They either do not have enough Amp (C RATE
capability) or they lack the capacity that your battery compartment COULD hold.
In a car, this doesn't matter.
In a powerchair it seriously does! The battery area (volume) is limited by
the chairs length/width/seat height.
The image shown
here shows why 1/3rd of your battery compartment is filled with wasted space
rather than cells. Above the cells, and on all sides.
Because although a battery is a group 24 "size" it
now only has the same 70 Ah capacity of a cheap lead battery due to this wasted
space. So no real gain. And some can do only a limited amount of amp draw, a maximum of 50 Amps discharge rate
in some cases before its internal protection
circuitry disconnects it! We need 5x that! Be careful what you buy!
Another Monobloc Lithium. There are lots. Non are
really suited to getting the best range/performance from a powerchair, and are
aimed at people that want to fit lithium's without understanding much about
a) they have much wasted space, packing
in the cells, and the electronics, meaning reduced capacity compared to doing it
My OWN Lithium battery powerchair -- Remember the WHOLE POINT
of lithium batteries is to fit more Ah (Amp Hour Capacity) into the same space!
b) Lithium cells (or batteries) cannot be
used in "dumb" mode like lead, they have to be monitored during charge, and
discharge, and the individual cells have to be monitored and protected and
controlled to keep them "balanced". In a standard "Lithium group 24" battery
solution, this is BUILT IN to the battery case. (In most aftermarket solutions).
This costs space, and Ah capacity.
c) Lithium batteries come in many types
and capabilities. A Hi end power wheelchair with say a 120 Amp control system
can require 120 Amps PER MOTOR simultaneously, so an intermittent 240 Amp
battery draw is a regular occurrence. Many MONOBLOC battery solutions are
limited to 50 or maybe 100 Amps max! Its not enough for our needs.
d) Most monobloc batteries either need a
dumb charger, or one that integrates with the electronics inside the battery. So
the charging system becomes tied to whatever is inside the battery case.
The NON MONOBLOC batteries below, allows my
powerchair TO SIDESTEP all of these issues above. They are very high C rate
cells, that are able to deliver some huge currents, around 5 times more than
required at many hundreds of amps.
And because there is no built in electronics, or space wasted trying to fit them
into familiar shaped battery cases to please the uninitiated. So more capacity can
be fitted into the same battery Volume/space. So doing it this way allows about 30
percent extra battery capacity to be utilized.
72 such cells makes a PAIR of 12v batteries
that are physically the same size or less than two conventional group 24
batteries. Although there are actually 78 cells in this one big pack.
This battery below gives you:
- 10 YEAR minimum expected battery life!
- 2x the storage capacity at low rate use (5 hour rate)
- 3x the storage capacity at hi rate use (1 hour rate)
- 3x the usual "hi end" powerchairs typical range
(45+ real world miles)
- Very fast charging (can be as fast as 20 mins)
- Much lower internal resistance for more torque and power!
(1/4 that of lead)
- Charge much less often - average use, weekly.
- No sulphation
- HALF the weight
- Safe LiFePO4 technology
- No memory
- MUCH cheaper LONG TERM use
- Greater reliability
- Allows a 15mph powerchair speed with no loss of torque or
But while this has HUGE advantages its part of a "system" since there is no one
size fits all BMS system built into the pure simple battery.