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Almost "any" batteries will work
to a degree in most applications but which batteries do
I really want, which are best for which job and why?
Well for reasons that will
become clear later you actually really want a GOOD deep cycle battery on your
mobility vehicle as well as on your Powerchair or Scooter. Nothing else
will do. We don't do simplified dummed down
answers on this site,
There is actually a HUGE
difference between all those
different battery types.
3 major sealed types of battery
in powerchairs... This describes them all.
Sonnenschein + MK gel
= same thing. MK bought the rights to use the
technology. Both are good and give exceptional service
life in un demanding powerchairs, that don't pull many
amps. for older people, low amp controllers, or mushy
programming where you cant tell the difference anyway.
So anything from Pride or similar then! They use starved
acid by VOLUME to protect plates from deep discharge
damage, so start ok when charged then go pretty "weak"
(higher resistance) when discharging. They need a full
8+ hours, up to 12 hours at 14.1v MAXIMUM to FULLY
recharge and return all the deep plate sulphate crystals
to the acid. 14.1 is safe, more like 14.4 puts voids in
the gel and you lose capacity as well as gain
resistance, and it doesn't recover. Or they will not
give full service life. Since mobility chargers seldom
do this they have a shorter life than they should!
Mostly they get too many volts, and cut off way too
early before charge is really complete. Some mobility
chargers (good ones!) are 3 stage. So go on to "float"
after main charge is complete. So they should be left
connected as long as possible AFTER charge to try and
top up the missing couple of percent.
Odyssey and other pure lead
plate batteries (Odyssey, Stinger, Exide,
etc) can use stronger acid and so are lower resistance
because they do not need to protect the pure lead plates
(no added zinc, carbon, calcium etc for strength) as
there's less corrosion deterioration on deep cycling. So
these offer better performance, lower resistance even
when discharged, less Peukert, so more of the actual Ah
is available for use. And they naturally charge much
faster. And they will start a truck in mid winter when
half flat... They need 14.7v CC/CV until 100thC and high
float for a few hours, or CV to 1000th C to get 450 to
500 cycles. Or they too will have a short life. These
kind of batteries are easy to recognise by the huge CCA,
CA, 14.7v charge voltage, cost, figures!
Deep cycle cheap batteries,
there are loads, like the Full River, and Haze, Power
Batteries etc are all usually AGM, are high
resistance. Because they have to use a weaker acid as
they use calcium or other metals alloyed into the lead
plates for strength and cost reasons. Stronger acid
causes them electrolytic corrosion when deeply cycled.
So these are usually higher capacity, (more but thinner
plates because of the zinc/calcium strength) but high
resistance with low CCA figures (or none as they cant)
because of the weaker acid and only suitable for low
current or constant current operation. Or my grandma.
They don't last as long either. 300 to 400 cycles max.
14.4v charge max usually. Or the alloyed metals cause
gassing and venting.
In ALL cases fit the BIGGEST battery you can. Often you cant fit bigger
though without serious modification. You cant do much about this limitation other
than fit the biggest battery you can in the space provided. Sometimes in a car
or van that's easy as the battery fitted may be pretty small compared to the
battery mounting tray size. In a scooter or powerchair that isn't often the case
so your stuck.
(Well you actually can change
this but its not easy!)
So what do you look for?
Read the batteries technical info sheets!
Not available? Buy a different battery...
It will read something like this (Example
data here is for the
Deep Cycle & Starter battery shown):
Minimum weight (kg):
Cranking Amps (SAE):
Capacity (C/20 rate):
55 Ah (Amp Hours)
400 @ 80% Depth Of Discharge (D.O.D) at 20 Hour rate.
There may be more information
available but this
is what we actually need.
Detail below -- what it means to us:
- Ah (Amp Hour) Rating.
"Amp" is a measure of current. An Ah rating is a
measure of the batteries ability to deliver this current over time.
In other words a 50Ah battery can theoretically deliver either 50 Amps for 1
Hour or say 1 Amp for 50 Hours. Or 25 amps for 2 hours etc. Its a measure of
the size of the "fuel tank". Don't worry too much about a few amp hours
difference when choosing a battery as long as its a sensibly close figure.
There are some other more important considerations. The capacity
Optima batteries I use in both my powerchairs and in
my van are 55Ah although these expensive batteries are not the best solution for most people.
For pure engine starting duties capacity alone is pretty much irrelevant and
all that really matters is CA (Cranking Amps) or CCA (Cold Cranking Amps)
where more is always better. For for average powerchairs that actually use
this store of energy Amp Hours are more important.
Make sure you use the 20 Hour rate though to compare (there are others like 10, and 30
etc) because the faster you try to get the power out the smaller the amp
hour rating and the opposite is also true. All because of the next important
Internal Resistance or impedance. This is VERY important. It
controls the amount of voltage drop under load. Its rated in Ohms. It can be found in the manufacturers
specifications. The optima shown above is
2,8 mOhm which is very low. That's good! We want low! 3.0
mOhm is worse... mOhm is Milli Ohm. (The wiring also has some
resistance as does the controller itself too.) This figure is very important.
if either resistance figures or engine starting figures are not available I
would look elsewhere as it (the battery) may not like big currents and you cannot know...
Decent batteries will have a figure. It will only relate to the fully charged
state though and it gets worse (bigger number) as the battery is discharged
during the day...
Where the above "Ah"
rating tells you the size of the fuel tank, the Internal
Resistance tells you the size of the fuel line!
It tells us how much power we can get out and how fast you can
get it. But
its a little more complicated. The internal resistance gets worse as the
battery charge decreases during use. In other words your engine may
"sag" more being starved of fuel before your tank is anywhere near empty.
Obviously then for engine starting duties you NEED a very low internal
resistance to provide the literally hundreds of amps required to fire up your car!
Especially a disabled converted car with many extra electrical devices like
ramps, doors, extra lights, on board computers etc. The battery has a very hard
time. You may be starting your car up with a half used up battery on a regular
basis and a half used battery is even less able to deliver the big currents
needed for engine starting...
On a Scooter or powerchair "Some" types of 50Ah rated
batteries will take you further than some 75Ah batteries
will. For the simple reason that depending on
the batteries internal resistance (which actually increases as it becomes discharged and used up) then
the actual "usable or accessible" capacity may not always be available
at the high loads that powerchairs and scooters demand at difficult times. The
internal resistance of my favourite Optima batteries is a very very low
That's low enough that it can deliver
HUGE currents with almost
no voltage sag. Even when almost flat. They use these Optima's to start big
trucks in cold climates and also its a true deep cycle battery as well...
Most deep cycle batteries can't be used for serious starting duties because
they just cannot supply the amps. With a few exceptions. (Hawker Odyssey,
and others) But this is all way over the top for most power wheelchairs and
wheelchair users. There are better solutions with a slightly larger capacity
and adequate current capability as well as "more 80 percent deep cycles"
before the rubbish pile claims them. I do have one on my van
here and I often use them in MY OWN powerchairs too because I use
bigger controllers and taller gearing than most and get sick of "normal" wheelchair
gel batteries failing me. But that's me I am not an average user.
The relatively high loads
a scooter or powerchair puts on the battery at times demand a battery that has a low internal resistance or it may not
deliver enough power (voltage falls) under load just when you need it most
on a ramp say, as your battery becomes more discharged.
In other words the battery "feels" run down and your scooter or powerchair
it will be "sluggish" even though there is a fair bit of energy actually
left in the battery. But its not "accessible" energy when high currents are
Its just that to use what's left in it you need to be able to take a smaller
steady current out of it for longer periods of time as in a UPS system or
similar use. Or if its easier to understand it may that with some battery
types that the voltage falls very low under load early on in the discharge
cycle. Now a battery that has a very low internal resistance will keep
on going and will still provide large currents on demand without much
voltage drop even when almost exhausted. In this way a smaller battery
can give greater range and performance than a larger one. This equates to
more usable range on your powerchair and a Motor Vehicle that will still
start even after repeated use of suspension lowering and ramp and door
operating mechanisms and extra time with lights left on etc.
One more huge advantage of the really low internal resistance batteries (like
the Optima, Hawker Odyssey ranges is that as well as being able to deliver huge
currents they can quite safely be recharged at a much higher rate than normal
deep cycle batteries. I fast charge my wheelchair for example at 30 amps from 50
to 70 percent discharged to 95 percent charged in around an hour every day
without any problems. The recommended rate for normal deep cycle batteries is
about 20 percent or their capacity or less. The reason this is possible is
because the low internal resistance means almost no heating and wasted energy.
Fast Charging -- about half way down!
Size -- Length, Width, Height is is all
pretty obvious, it must be able to fit the space provided.
Weight -- Heavier usually means more lead.
Deep Cycle Batteries and combined Deep Cycle and Starter batteries all NEED
thick heavy plates. Weight is a good indicator of quality. Thicker plates are
required in most Deep Cycle Batteries to prevent distortion and survive deep
Voltage -- Almost all Lead Acid batteries
are 12 Volts. There are some 2, 6, 8 Volt variations and the odd 16 Volt
specialist batteries available used in motorsports but these are for unusual
specialist applications. The batteries in your Powerchair or scooter are 12v
They are connected together in most cases in series to give a working voltage of
24v. Your car or van is 12v. If it has two batteries then they are
usually connected together in parallel so that you have double the starting
current but still only 12v total.
Cranking Amps (CA) and Cold Cranking Amps (CCA).
This is the number of Amps the battery can supply while the voltage stays above
a pre defined level for a few seconds It simulates the best your battery
can do while trying to start an engine. This typically takes hundreds of amps
and is very punishing to a battery. Standard car or truck Starter batteries have
many thin plates with just a lead "sponge" coating.
This gives a huge surface area allowing equally huge starting currents but they
cannot be deeply discharged without damage. Normally a Deep Cycle battery wont
have this information on it or in any documentation because it both isn't
intended to be used for this sort of duty and most couldn't do it anyway. If you
try then you could actually damage the battery permanently. Much of this
isn't really relevant to your Deep Cycle PowerChair batteries since most
powerchairs and users don't need these huge current capabilities.
There are one or two that do though and they know who they are! Usually big
hotted up reprogrammed powerchairs with heavy users that have noticed the
batteries "sagging" when asked for more acceleration, or while climbing curbs
and ramps. Fortunately for use they make batteries like the Hawker Odyssey
and the Optima "yellow top" batteries. Both of these are true Deep Cycle as well
as excellent high current Starter Batteries You don't have to choose one
or the other
Deep Cycle, Starting only (actually called SLI for Starting Light &
Ignition), Deep Cycle and Starter Battery.
What is the difference?
Starter batteries are designed ONLY to fire up your cars engine. This
typically takes hundreds of amps 500 or more Amps in winter to start a big
engine is normal. It starts in a few seconds and your battery then has only
been discharged by a few percent. Five percent or ten maximum for a very
hard start in winter, Its then charged right back up again by your cars
charging system very quickly. Used in this way your Starter battery
will last many years and many thousands of starts.
- Starter batteries.
A starter battery is great at delivering big currents for a few seconds
only. If you discharge it deeply as you would say in a Powerchair on a daily
basis (or if you leave your cars lights on accidentally a few times) it will
die a horrible death and last weeks only. All lead acid batteries
suffer when discharged. In the case of Starter batteries which use a lead
"sponge" coating on the plates to increase surface area -- it literally
falls to the bottom of the battery and the weak thin plates warp and deform.
They love to be charged at 100 percent and seldom discharged much!
Deep Cycle batteries.
Deep Cycle batteries generally wont / may not start a car and trying to do
so actually can damage some types. They have higher internal electrical
resistance. You wont find a CCA or CA figure on them. They are designed not
to suffer as much as most lead acid type batteries when discharged very
deeply on a regular basis. A GOOD Deep Cycle Battery can be discharged say
500 times at an 80 percent discharge level. A starter ONLY battery as fitted
to your car would typically give you 20 to 50 cycles under the same
circumstances. So why the difference?
GOOD Deep cycle batteries use solid thick pure lead plates. This means that
unlike the starter battery above it cant shed its Lead Sponge Coating. And
its plates don't warp. But it has less surface area in contact with
the (slightly weaker) acid and so its electrical internal resistance is greater.
That's why it cant easily start a car or is bad at high currents. Which is a shame because modern
cars and disabled converted vehicles with all the hoists, ramps, lowering
suspension, on board computers and other equipment really need a battery
than can be discharged like a Deep Cycle Battery can. So if you have any
sense and you drive a modern car full of electronics, especially if its got
ramps, lowering suspension etc then you really need a Deep Cycle and
Starting battery. One that combines both of the above and there are a few at
Deep Cycle and Starter.
These unsurprisingly are a combination of the two! A very clever trick
pulled of by very few batteries. The Optima battery is an example of these.
It is a true Deep Cycle battery (400 Cycles - some pure Deep Cycle batteries can do 500).
But because of its odd unique spiral cells that are made from thin pure lead
rolled up very tightly it can start a truck too!
Instead of using thick lead plates for its anti distortion strength, it uses
the fact that its rolled up tight. Because the lead can be much thinner
there is masses more surface area. This means it can have a very low
internal resistance and high Starting Amps (CA, CCA) without needing to
resort to lead sponge coatings... It also spill proof, and can be charged at
high rates. Its for this reason I have them in my powerchair because
unlike most users I actually need the big amps they can deliver and as a
starter battery in my
Van because I understand the benefits in such a vehicle.
Cycle Life of a GOOD quality Deep
(for use in a Power Wheelchair or Scooter is displayed below). You will not
match this with a "cheap and cheerful" Deep Cycle battery. This graph is for the
likes of the Sonnenschein A500 or similar high quality battery as fitted by the
manufacturers. Remember this is under ideal conditions and temperatures with a
very carefully tailored multi stage charger and exactly the same discharge level
every time. In REAL usage conditions this will never actually be achieved.
Powerchair Battery State of Charge
As you can see the average depth of
discharge GREATLY effects the number of cycles a Wheelchair or
Scooter battery can survive. Expect to get only 10 months out of a
Powerchair / Scooter battery if its used every day and used a lot.
I get typically 10 months (300 days) use only
because I actually use 80 percent of my batteries charge every day,
through shopping, dog walking, and going out in the evening etc.
If you don't go too far live somewhere flat and don't use
many steep ramps etc and average 50 percent discharge daily then expect 1000
days use or nearly three years.
If you are one of the masses of not very active users or are
sat in an old peoples home watching the TV all day expect a much greater
battery life up to 5 or 7 years. For these people a cheaper low
quality deep cycle battery makes some sense.
In addition to the above also consider
Pure Quality branded Deep
Cycle batteries like the Sonnenschein batteries will typically give up to
500 Cycles at a discharge level of 80 percent. (as above chart)
Cheaper pure Deep Cycle
only batteries usually give around 400 Cycles (check the figures!)
Dual Purpose batteries
like the Optima, Hawker Odyssey batteries will give around 400 Cycles but
also can make huge currents so no voltage drop under load and can be used in
your car or truck with many advantages too. And they can safely be
fast charged which I find
essential (nr. bottom of page)
Leisure batteries labelled
deep cycle are very cheap but will give about 90 to 150 Cycles.
Car starter batteries will
give you about 30 deep cycles depending on quality. That's not their
intended use! And its really false economy.
With batteries you really do
GET WHAT YOU PAY FOR!
(a motor vehicle battery).
your disabled modified vehicle is driven daily then there is no need.
The cars alternator charges at 14.4v (or close) as soon as you start it and
charges the battery fast. The danger is if its left unused for say a week or
longer. All modern cars have such things as immobilisers, remote locking, engine
management computers, alarms, various radio memory and other electronics that
drain the battery as the car just sits there. With extra electronics such
as remote start, or say the computer in the boot of my minivan that controls the
ramp, electric doors, suspension lowering, the battery has double the drain on
it while sat unused!
Plus every time you
switch off and get out, the ramp and suspension lowering as well as
the door opening and closing motors all use a lot of power. Your battery is then
in a slightly discharged condition. Batteries store well fully charged. But sulphate internally if left in even a slightly discharged
that's now happening...
the fact that all those electrical systems mentioned above are gradually taking
more power out. So if you leave your car/van for more than a few days or a week
its a good idea to charge it. It doesn't actually need a full charge (although
that wont hurt) but it needs a maintenance charger like this Optimate or similar
connecting and leaving connected while you are not regularly using it.
It may well still start
if you don't bother but your battery is suffering and will sooner or
later let you down. Another alternative is a good solar charger of 2 to 5 watts.
It wont "charge" your battery but it will keep it topped up and prevent it going
flat or sulphating. Less than 2 watts is a waste of time unless you live in
Arizona! I leave one plugged into the cigarette lighter socket sat on my
dashboard when I am not using my van. It keeps my battery fully charged and
Remember ALL lead acid
batteries HATE BEING DISCHARGED!
Charging a PowerChair or scooter battery.
All Powerchairs and Scooters use Deep Cycle Batteries. These despite their name
DO NOT LIKE BEING DISCHARGED!
With this in mind its best to ALWAYS charge them every
single night with the manufacturers charger or something equivalent
with the correct profile. Even if you only used the mobility device for ten minutes. Every
night. Don't Forget! even if you fast
charge them during the day. If you have not used it at all then charge it once
every week over night. Once a week will help prevent the batteries becoming
discharged which ultimately is what kills them. Never discharge Lead Acid Deep
Cycle batteries on purpose to get rid of any memory effect! They don't have a
memory effect! Even the original rumour that NiCad batteries has a "memory" was
not actually true. All deep discharge does is damage your batteries.
If you get chance during the day it IS BENEFICIAL
to plug in the charger to lower the average daily discharge level. This is
called opportunity charging. Contrary to what you may read elsewhere it is
beneficial. Anything that lowers the average discharge level helps your
batteries live longer. It still needs
the full overnight charge however every night just the same.
Are you fed up with waiting hours for your chair or scooter to charge? Well
depending on your battery type you CAN fast charge them. I use Optima Deep Cycle
and starting batteries partly because it allows me to charge them up in the
middle of the day to 90 percent + in just one hour. See
It still needs the full overnight
charge from the normal slow (8 amp or 20 percent of battery capacity) charger
however every night just the same or your batteries never get properly charged
and will become unbalanced.
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