A friend of mine has an electric wheelchair, it's a cheap Chinese one and i
t has two lead acid batteries.
He seems to want to buy some more batteries for it and I'm convinced he doe
sn't need to as we only got some a couple of years ago.
He only uses it twice a week to go about 500 metres on each occasion.
His wanting new batteries is prompted by the fact that the lights indicatin
g the level of charge go into the amber zone and he thinks it's about to ru
n out of power. I reckon it should go a lot further then he fears and then
there's the question of charging the thing - how long does it need?
I'm planning to take the thing for a run and see actually how far it will g
o after an 8 hour charge but I wonder if anyone has any experience of these
On Sun, 11 Dec 2016 07:24:02 -0800 (PST), Murmansk
How far it will go depends upon his weight and the degree of incline.
The manufacturers/sellers estimates are for a plastic garden gnome as
occupier and a perfect level surface and even then are wildly
Lead acid batteries discharge gradually until the voltage start to
fall and then go quickly. See
for an example. His concern over being left stranded if the charge
indicator is amber may be justified. Unfortunately there is no
particular standard for the calibration of the devices.
Sealed Lead Acid are also delicate little flowers and do not tolerate
total discharge at all well. Given that he may have let it discharge
significantly in the past a service life of 2 years isn't at all
unreasonable and replacement may be sensible. Getting batteries from
the wheelchair supplier isn't necessary and is usually significantly
more expensive than getting them from an on-line or local battery
specialist. Batteries specified for deep discharge give some extra
protection against battery failure due to over discharging them, but
Charging time depends upon the charger type. For most leaving the
charger plugged in when the chair is not in use at home seems to give
the best results. From half to full charge usually takes 8-12 hours
but there is a lot of variability between chargers. The smaller and
lighter the charger the longer it is likely to take.
On Sun, 11 Dec 2016 16:25:12 +0000, Peter Parry wrote:
Depends on the charger/battery combo. The very first electric wheelchair
SWMBO was issued from LA stock could not support a permanently connected
charger. The end result was it was never used, as the batteries were
always being overcharged.
I don't know the answer!
It seems a reasonable idea to take it for a run to test the battery
life. As others have said, the distance it will go will depend on the
weight of the occupant and the gradient - and probably the type of
surface. I imagine that the battery will get used up faster on loose
gravel than on smooth concrete.
I would suggest choosing a route which is typical of that used by the
owner, and noting how much further you can go once the battery indicator
enters the amber zone.
A route which circled your house may be better - finding out how far
the battery will go by ending up a mile or so out with no electricity
isn't wise, most electric wheelchairs do a good imitation of an
immovable (or at least movable only a very short distance) object once
the batteries fully discharge. Full discharge also knackers Sealed
Lead Acid batteries.
Don't over look a poor meter. It is quite difficult to get an accurate
estimate of remaining charge simply from terminal voltage anyway and add
to that a cheap/nasty meter and the result could well be pessimistic.
Take a volt meter with you on the test run and see what voltage
corresponds to which meter reading.
What size? They vary from 12Ah to 120Ah. What is the battery type number?
Cheap batteries can have a much lower Ah capacity than stated, and often
don't last long.
o as we only got some a couple of years ago.
Whatever you do don't get batteries from a disability shop. Look at
battery suppliers on the internet.
A small chair with two 16Ah batteries will go four miles assuming
1. The surface is smooth (grass or rough surfaces reduce the range by
half or more)
2. The route does not involve much climbing
3. The person is not extremely heavy.
4. The person doesn't keep speeding up and slowing down all the time (as
some nervous people do).
5. The chair is in good working order. Check the front wheels to make
sure they turn freely. Check the steering pivots; if stiff they reduce
range. Check the brakes aren't binding. Inflatable tyres should be
A large chair with two 100Ah batteries will go 20 miles if the same
parameters are obeyed.
harge go into the amber zone and he thinks it's about to run out of power.
It means nothing. Some chairs go to amber when the on-load voltage is
still 23.7V or more.
lot further then he fears and then there's the question of charging
the thing - how long does it need?
It depends on the charger. A cheapo charger will never charge the
battery optimally. It might under- or -over charge.
A general point is that even when the machine says it's fully charged
what it actually means is 'useable'. For this and other reasons the
machine should be on charge every moment that it isn't actually in use.
A decent charger will never overcharge.
Google Numax 24V mobility chargers. I've had a few of these and they are
good. When you tell me the battery type and size I'll tell you which one
charge but I wonder if anyone has any experience of these chairs.
No, put it on charge for 20 hours and then try it. Ideally check the
off-load voltage after an hour's rest after a full charge. It should be
no lower than 26.5V.
My partners chair was little used, when she passed away it was around
12 months old. I have made use of it occaisionaly in the 18 months
since then, for trips where I would normally walk, but where some
weight needs to be carried - just to avoid getting the car out. One of
those trips is a mile downhill and a mile back up carrying 2x 17kg bags
of dog feed.
I pop it on charge after use and it replaces the used charge in < an
hour. The charger is switch mode type and it cuts off at full charge,
so no point in leaving it connected permanently. Every month or so I
give it a boost, which takes just a few minutes to cutting off.
The remaining charge meter is almost useless. It seems to be just a
volt meter and the voltage goes up when off load, way down when
climbing a hill and under a heavy load.
No, what the charger does (or should do) is switch to a safe slow
charge, to avoid overcharging. It will continue to charge for many hours
until eventually the charge rate becomes just a few mA. At the point
when the charger switches the battery is probably only 70 to 80% charged.
If you really are fully charging the battery after a one mile uphill run
in less than an hour the charge rate must be extremely high.
Since your journey is downhill for the first mile the chair will be
charging the battery regeneratively in that time unless it's a cheap or
Unless the charger is a crap one it's much better for the battery to
give it 24 hours at least, and 24 hours every month.
No, leave it on if it's a good modern charger. It will just be providing
a few mA.
In fact I'll just go and have a look at the motorhome batteries. One
says 0.003, the other says 0.012. The second one was used briefly two
days ago. The batteries are 90Ah deep discharge types. The chargers are
16A. After deep discharge the charger starts at 17A and tapers over 36
hours to about 1A. Eventually the charger switches to 'float'.
I can't easily get at the other one but when I checked it the float
charge was 1mA. That's a 33Ah battery on an 8A charger.
I haven't checked the charge rates on the big chair (110Ah) since we got
it and I can't remember the figures, but when deeply discharged it takes
14 hours on an 8A charger for the green light to come on, and at that
point it is not fully charged. We found out the hard way. It needs half
a day further charge to be full.
We also have a small chair on a 4A charger. That starts at 4.6A and
after the green 'full' light comes on it continues at around 300mA,
tapering down to less than 1mA after a week.
Was meaning it should do that itself. Even my pretty ancient and
inexpensive Lidl car starter pack which contains an SLA battery switches
off the charger when fully charged.
If it's only providing a few mA, that's going to be neither here nor there
to the state of charge - except over a long time. Normally called a
maintenance or float charge to keep a battery that isn't actually in use
Most leisure batteries are wet types. Don't wheelchairs have SLA (gel)
types because they might get overturned?
Sound like a poor charger. I'd say it would be a requirement to charge the
batteries overnight. Not effectively a full day. Think about it. ;-)
I'm sure there are all sorts of tricks to get the last 1% or whatever of
charge. But if that is crucial, just fit a larger battery?
*Just give me chocolate and nobody gets hurt
Dave Plowman email@example.com London SW
On Mon, 12 Dec 2016 11:37:25 +0000, Dave Plowman (News) wrote:
Not just that, but there are differences in profiles (or something). I
managed to fit some SLA UPS batteries to a scooter, which lasted 6
months. I was going to complain when I discovered I had ordered UPS
batteries - which were cheaper than scooter (golf buggy) batteries. I
think scooter/buggy batteries are designed to deep-cycle, whereas UPS
Not sure this applies to gel types in quite the same way as it does to wet.
What make were they?
Depending on where you are, a UPS could get quite a pounding. Do they say
batteries for this use will only stand a few cycles?
I've not seen a good make SLA like Yuasa marked for actual usage.
*If a pig loses its voice, is it disgruntled?
Dave Plowman firstname.lastname@example.org London SW
A common mistake. The other common mistake is buying cheap brands, you get
less capacity and half the life. Yuasa are good - obviously you need the go
lf buggy or disability scooter rated ones. If the machine is ever to go on
an airplane they need to be disability scooter rated. IIRC the relevant Yua
sa types are REC and YPC.
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