It was thought for many years that this
fast charging treatment was harmful to your batteries & will harm or
shorten the life of your batteries. Problem is that now all the so called "experts"
think they know that this is true! But it really isn't! Its much like the story about Ni-Cad
batteries developing a memory! Everyone KNOWS that its true. Well its just as
wrong. They don't. They never did. At least the only time it ever happened was under a specific set
of very hard to reproduce circumstances on a satellite by NASA in early days. And even
they had much trouble reproducing it. Its just a myth. The real reason for low
charge rates on lead based batteries is because in the early days accurate
voltage control, and fancy 3 stage charging profiles common to almost all new
chargers today didn't exist. So charging at a slow speed minimised the problems
caused by incorrect voltages.
Heat over 50 centigrade during charge can cause
damage and is caused by high internal battery resistance (nasty cheap
deep cycle batteries or an "old" used up battery) or by OVER
CHARGING (too high voltage) a "recombinant" type battery such as most sealed
power wheelchair batteries. But charging at a very high rate but at fixed safe
voltage does NOT overcharge a battery and so is perfectly safe.
My own 30 amp powerchair charger. And some connecting leads.
than the original equipment 5 amp one!
Since quality deep cycle batteries with much lower
internal resistance are now the norm (the main source of the heat at high charge rates)
then this is no longer a valid reason not to fast charge them. The advantages to
the user are huge, and battery longevity resulting from regular top up during
the day is vastly improved. Due to the lower average depth of discharge.
Another source of heat in sealed batteries is the chemical
recombination of hydrogen and oxygen caused by overcharging. (Too
high voltage!) But since we now have very accurate logic controlled chargers
this is no longer a
valid reason not to fast charge them. In the past charging a 70 Ah battery
with say a 8 amp charger meant that even if the charger charged at too high a
voltage no external gassing would occur since the recombination capability in
sealed batteries would be able
to re-absorb the gasses easily. So no external gassing would occur. In other
words its far less critical to get the charge voltage right at a slow charge
rate and so its "recommended" by many battery companies. They don't want
batteries back under warranty! So recommending low charge Amp rates is
a crappy charger is used! But we don't have crappy chargers any longer!
Well I don't anyway... All switch mode multi stage chargers should be safe
provided you select the correct type for the batteries you use.
Now, knowing that
actually suggest a "no current limit" and fast charging as a preferred charging
method (such as some AGM batteries: Hawker Odyssey and Optima
and many others) and
no current limit may involve hundreds of amps, then you will soon
see that using say a 25 or 30 amp logic controlled 3 stage charger on a
powerchair with big 70Ah batteries is not only sensible, its actually really
extremely cautious! And far from the hundred Amps plus that a cars alternator
would charge them at.
If a PowerChair battery can produce
hundreds or even thousands of amps as some quality AGM deep cycle
batteries can, then charging them at 30 amps is actually a very conservative
approach. After all charging is exactly the same reaction as
starting a car. In reverse. The only time
that limiting the current while charging a Deep Cycle battery becomes important
is if that battery has a high internal resistance as some cheap nasty ones do.
Does it harm them? No,
Contrary to what ill informed wheelchair manufacturers may tell you it does
just the opposite. Many studies on deep cycle battery powered machines such as
airport floor cleaning machines, etc have shown that fast charging deep cycle
batteries actually helps them live
longer especially when used as regular opportunistic charge system. It appears to actually be
very good for them.
The only thing that damages them is either over charging them
(going above say 14.1v or 14.4 volts per battery for a typical battery (see your batteries spec sheet).
Or continually undercharging them. Undercharging, or really deep
cycle use, heavy discharge, or not doing a complete charge often enough are the
things that damage your expensive batteries.
Fast charging only replaces typically 95 percent of your charge due to
something called acid stratification and plate surface charge. A reverse Peukert effect. You
STILL NEED an overnight charge and long soak with your slow charger as well.
night if possible or at least every few days if that's not possible.
all of your two batteries cells equalised and properly balanced and sulphation
free. Otherwise they can get
out of step. Which is very important for
battery longevity. Depending on the charger you use this fast charging will only
replace about 90 to 95 percent of the capacity. in about an hour. Its intended to let you charge
or top up in the middle of the day or before going out in the evening.
My wheelchair batteries are on charge here. This is a Clamp Ammeter. It started off
when first connected reading 30 amps. It always does if the batteries are pretty
When first plugged in the batteries "suck up" as much
as the charger will let them. If its a 30 amp "capable" charger like this one is
then it will deliver 30 amps in its first charge "stage" (of 4)
It is, like most modern chargers, a
fixed regulated voltage (28.8v in this case for two AGM batteries) for as long as the battery sucks up the 30 amps
that the charger is capable of delivering. If it was a 60 or 100 amp charger
then that would be fine too. And it would then be able to raise the batteries
voltage to 14.4 (28.8v for two) even faster! And that's quite safe for the
batteries. The current (amps) gradually tail off once the battery achieves the
set 14.4 (28.8) volts...
In this case above the charger is 30 amps. So that's what the
batteries greedily take. That's because the charger is basically a fixed voltage
power supply with a current supply that is limited. Just like your standard 5 or
8 amp powerchair charger is limited to just 5 or 8 amps...
Once the battery "achieves" the set voltage then the
current starts to fall away from the maximum the charger can do, and that is the
end of the so called "stage 1" and stage 2 begins. Nothing actually changes
other than the current drops to keep the battery from exceeding the set FIXED voltage.
So this continues until the current falls NATURALLY to a very low level. That signifies
the end of "stage two" on your 3 or 4 stage charger.
The next stage is simply a
permanent lower voltage "float" that goes on forever. This stops your battery
from deteriorating over the long term. Stage 3 then never ends... In fact in a
powerchair only two stages are really needed. And if you are unplugging it after the
green "ready light" illuminates then you don't use the third float stage anyway.
It happens AFTER the ready light.
I also have a 100 amp charger (a 12v one) and this
charges single loose batteries quite safely too. As long as your batteries
manufacturer specifies no inrush current limit then its not a problem no matter what other so called "experts" may tell you.
However, the faster you charge a lead acid battery the lower the amount of
charge you actually put back. This is due to the acid having no time to level
out its state of charge and the charge is mostly at the plate surface.. The
"deeper" charge takes time to penetrate the battery plates. This is the reverse
The name for this is charge stratification. So a fast
charge in a good quality low resistance battery may only really be 90 percent
charged. So a slow charge at 1/10th the batteries capacity (your stock slow
wheelchair charger) is recommended either every night or at least every few days
to fully equalise all the cells and keep your batteries in balance and healthy.
I use both of these 30 and 100 amp chargers on all my
batteries over the last few years without any problems whatsoever. In fact they
now last longer due to the lower average discharge levels that a fast top up in the
afternoon gives them. Ready to go out again and a green ready light (90 to 95 percent)
usually well under an hour...
After around 10 to 20 mins depending on discharge level it falls
slowly (to 21 amps here), as the battery becomes charged up and it own voltage is closer to
the supplied 14.4v (28.8v) voltage from the charger. This part where the battery
no longer pulls the full 30 amps from the charger is the "second stage" of a two
stage charger. And so far it didn't do anything apart from supply a fixed
voltage and a maximum current of (in this case) 30 amps... So we get duped. A
two stage charger is really that simple.
As charging nears completion and the battery voltage slowly rises less current
The current keeps on falling. When it reaches around half an amp in this
case above (depending on rate of fall etc) and your battery is just sat at
14.4 volts and needing little power to hold it there the charger says done!
That's the end of the stage 2.
It then switches to "float"
mode which is in this case is 13.4v per battery (26.8 volts.) measured. Ad it
will hold your battery there for ever. Float charging isn't really "charging" at
all. It just prevents the batteries natural internal discharge from happening. So its
quite safe to leave connected for very long periods or just overnight.
can go from pretty much discharged after shopping to 95 percent plus charged in
under an hour ready to go out for the evening. Most normal 3 stage chargers are
now finished whether fast chargers or slow. See? They are really pretty simple.
Using THIS plug (Anderson plugs and sockets) fitted to
my powerchair and connected directly to the battery terminals I fast charge my
power wheelchair most days. Don't try this fast charging via your wheelchairs
charge socket! It will melt something expensive!
Fitting Anderson connectors to your powerchair for fast charge and connecting
I use this 30 amp fast charger. 4 Stage logic
controlled 30 amp switch mode efficient device. I have 3
actually, one in my van just in case and one as a spare! It can be used to
charge up my powerchair (2x 70 ah batteries) to 95 percent+ fully charged in
around 1.5 hour ready for an evening out! That's if your batteries are
pretty beat up. If you are only about a third or half discharged then its faster
still to a green ready light! See also
Fast Charging Your Powerchair
Switch mode 30 amp, 1 hour fast charger.
Fully digitally controlled 4 stage safe fast charging. Designed for
Good AGM batteries like the Optima and Hawker
Odyssey ones that I use. You do not need this specific charger ANY
24v HI AMP MULTI STAGE CHARGER FROM 10 TO 100 AMP WORKS GREAT. The bigger the
better. (Faster) Mine came from eBay as a caravan/leisure charger. It can
also charge 12v, 24v, 36v, or 48v as well. About 100 UK Pounds. So I bought 3.
Full slow overnight charging with your standard 5 or 8 amp charger is still
required at least every second day or so however (to equalise and "even up" all
the cells properly and to prevent long term sulphation) but opportunity charging
during the day, say 5PM while you check your email, is both advantageous to the
user (its invaluable since you go out again "topped up" and ready for
anything the world may throw at you) and it makes your batteries last longer due to
a lower average depth of discharge.
Charging the batteries at 30 amps (or much
higher) opportunistically as often as you get chance is perfectly within the batteries specifications and capability
AND helps them live a longer life..
I use this charger above although there are plenty to choose from. Google and eBay
list of bigger faster chargers RECOMMENDED and sold by the hawker
Soneil multi stage switch mode chargers - find a dealer! All will work and be
safe with AGM or Gel batteries the 30 amp one is the most suitable for 70ah
batteries and maybe 20 amp for 40ah batteries. 12 amp for small 25 or 30ah
2424SR - 12 amp
2430SR - 15 amp
2440SR - 20 amp
2450SR - 25 amp
2460SR - 30 amp
http://www.soneil.com/24_volt_high.html All are on this page.
internet is full of
suitable chargers like this Gel and AGM safe one
for AGM only batteries
(slightly higher voltage for faster charge rate to suite AGM chemistry.
Personally I find eBay easier.
Or 24v and 25 amp charger
12 amp one here that does 12v or 24v
This one is especially interesting as it is actually two isolated 12v
chargers built into one case that are completely electrically isolated.
Available as 8 amp or 20 amp power outputs. So you can charge both your 12v
batteries in your powerchair at once but separately. Rather than in a
series "string" configuration. This has the advantage that its never
possible to have one battery in a higher state of charge than the other. Both
your batteries will always be charged to exactly the correct level which has
many benefits over the stock charge method.
You will need to fit TWO charge connectors to your chair
Fitting Anderson connectors to your powerchair for fast charge and connecting
Expensive and similar to the above in that it charges your batteries
individually (which is superior) and can do three at once! I plan on adding an
extra battery so that I can use 36v instead of 24 in the future with a different
Personally I have started looking at Lithium Phosphate
batteries. These can also be fast charged, are about 4x better at energy storage
and cannot explode like Lithium Ion or Lithium Polymer batteries. Imagine
the speed or range that that will allow! And the weight saving. They are
expensive, but they can do 1500 80 percent discharge cycles compared to 400 to
500 of GOOD lead acid batteries... WHY ARE THE MANUFACTURERS NOT ALREADY USING
THESE THINGS? I know they will have hundreds of excuses but the real reason is
they don't care and cannot be bothered to learn what's possible and do any
Lithium Ion Batteries for
Powerchairs and Scooters
Powerchair directly from a vehicle. via the same Anderson connectors
Anderson Style connectors
and why you need them
Fast Charge YOUR Powerchair
in Around 1 Hour
Inverters & Chargers
Batteries for Both Vans & Power Wheelchairs
Batteries to Buy
Very Flexible Charger!
Lithium Ion Batteries for
Powerchairs and Scooters
My Power Wheelchair or Scooter Will Not Charge
BCI Battery Sizes, Group 22, 24, 34, 27 etc
Drive Your Powerchair by Radio Control
Superior Powerchair overnight charger
How to organise yourself for every eventuality!
Powerchair Battery State of Charge
MORE: Detailed PowerChair Only Menu
Hyperion charger can
charge almost any battery. Including your wheelchair from your car or the other