Where to get Sealed Lead Acid (Absorbed Glass Matt type) batteries : last updated
25th of October, 2006
Never use 'gell cells'!! There are two types of SLA (sealed lead acid
batteries): gel type (gell cells) and agm (absorbed glass matt type). Gell type
have a very large drop in voltage as soon as you accelerate and are all but
useless on electric bikes.
You need to use SLA AGM (absorbed glass matt) TYPE! This is the type
used in ebikes and fortunately they are readily available in car jump starter
units.
There are different types of glass fibres used in sla agm batteries so the
quality can vary but I've found car jump starter units to be as good as agm
batteries designed for ebikes in terms of how long they last (usually about
15months of useful life if used regularly).
Some new info on jump starter batteries: one manufacturer of the jump
starter batteries (shunhong brand) has confirmed that jump
starter batteries are Absorbed Glass Mat (agm) type. This is best
type of lead battery for electric bikes. Also because the jump
starters need to produce a high current their plates have a
larger than normal surface area or thicker plates . So it appears that jump starter batteries are
probably better than standard ebike sla agm batteries. Thats very good news
indeed as jump starter batteries are easy to find and prices are
reasonable (buying a good quality agm batteries from specialist
battery suppliers can be very expensive).
Deep Cycle Sealed Lead Acid Batteries are
commonly available nowadays (this is just a very recent
development as large stores are now stocking jump starter units and they seem to
becoming more widely available with some large chain stores now selling them).
The cheapest source of Sealed Lead Acid Deep Cycle batteries
is to buy three(36volt) or two(24volt)car jump starter units in
your local area. Jump starter units come with a charger which you
plug into your mains power. Some also come with a built in
battery voltage meter so you can see how discharged the inbuilt
battery is (the picture below shows this type).
Which Type of Jump Starter pack to get:
1.If the jump starter pack has 900amp written on it , it will contain 17ahr
battery size.
2.If the jump starter pack has 600amp written on it, it will contain 12ahr
battery size.
3.Take a voltmeter into the shop with you, test the jump starter pack to see
what voltage it reads (you can just put the voltmeter across the jumper leads
with the pack turned on). It should read about 13volts or over if its a good
battery. If its been sitting around in storage the voltage will be lower, if the
voltage is less than about 12.8volts or 12.9 volts dont buy that battery pack it
means its been sitting around for a long time undercharged, these batteries need
to be kept charged to get the maximum life out of them.
4. try and get a jump starter kit type that has a very large on/off switch on
it, they are very high amp rated switches and very useful for an on/off switch
on an ebike (quite expensive and hard to buy a switch like that by itself). Pic
of the switch below
5. Also the same jump starter pack that comes with the high amp switch has a
handy voltmeter (there is also a resetting circuit breaker in these type that
has a current rating suitable for ebike use (around 20amps).
Each car jump starter unit has one 12volt deep cycle battery
inside it. I take the battery out of the case and use on the ebike. I've also
taken out the charging circuit and installed on the ebike.
In Australia jump starters available at Dick
Smith Electronics, Super-Cheap Autos, BigW, Kmart, The Wharehouse. Look out for specials The Wharehouse sells 17amphr
for $60(sometimes on special for $50), Super Cheap Auto. The wharehouse chain of
stores tends to have the kits which have a large high amp switch on the pack,
very useful.
Try to buy a jump starter unit that has a voltmeter in it, you can use the
voltmeter on the ebike (some even have an air compressor to pump up the tyres
but are more expensive), a
jump starter case that has a voltmeter is best type to
get as they have an auto cut-off in the charger ciruit so you
cant over charge them. Shown below
are two types of jump starter units. The two left hand pictures show the best
type in my view. The one on the right doesn't have an auto-off charger.!
-------
Pic 1: jumpstarter with meter ----Pic 2: voltmeter closeup
-----------------pic 3: other model: no voltmeter no auto cut off in charge
system
How to use the Battery in the Jump Starter Kits
(before doing any changes to the jump starter cases check they charge up to over
13volts, if they dont charge to over 13volts they are no good and have lost
storage capacity).
Undo case. Firstly remove the plastic covering on the
terminals.
Undo the bolts securing wires to each terminal. Remove battery.
This part is important: Using the nut/bolt which you've just
undone, re-connect the wires
together as shown below. The black wires which all connected to
the negative of the battery
should be joined back together with the nut/bolt. Any wires which
went to the positive terminal (red) should
also similarly be joined back together.Use electricians tape to
cover the nut/bolts so that there is
no chance of shorts.
For charging plug in the 240volt adapter that comes with the
jump starters.
as shown below (different brands will plug in different places)
To charge your battery hook up the red jump start lead to the
red terminal of the battery.
Similarly hook up the black lead from the jump starter to the
black terminal of the battery.
Be careful not to put the leads in reverse as you may damage the
jump starter electronics.
Plug the 240v adapter into the mains power and the batteries will
begin to charge.
In the case of the jump starter below a red light will be alight
when charging, when the battery is fully charged
the light will go out. (other models may have a red light on when
charging, and a green light when charged).
You will have to devise your own method to secure the
batteries to your bike. In my case I have
3 jump starter batteries(17amphr) in series in the rear of my
home-made trike.
IMPORTANT:
Never leave the batteries in a discharged state. When you go for
a ride make sure you put the batteries
on the charger as soon as possible after your bike ride. They
should never be left for more than a few hours
in a discharged state as this will reduce the lifetime and
capacity of the battery.
I always remove my batteries straight after a ride and put on
the charger. Depending on how much of the battery charge
you have used and what size batteries it may take 12 hours or
more to recharge the batteries. Typically the mains voltage
chargers only put 500mA of current into the batteries, faster
charging rates can be achieved by acquiring higher current
adapters (for example a 17amphr battery may be charged at up to
4amps, this would mean an 8 fold reduction in charging time). I
prefer to leave charging overnight at a slow rate as its probably better for the
life of the battery to charge it up slowly.
The
nice thing about the jump starter batteries is that they are
designed for high current draw, draw as much current as you like
and it wont damage them. Also you will probably find that buying
batteries from a specialised battery supplier will be ALOT
more expensive than buying a jump starter unit for an equivalent
size battery. Also they may sell you gell type cells instead of the correct
ones...agm type.
NOTE: THE BATTERIES LIFE IS MAXIMISED BY ALWAYS KEEPING THE
BATTERIES CHARGED,
RECHARGE IMMEDIATELY AFTER A BIKE RIDE
If its not possible to recharge the batteries immediately
because your at the beach or work or whatever, I suggest a solar
trickle charge unit be used ($30aud from supercheap autos), the
batteries will have to be in parallel when using the solar
charger. There will only be a very tiny current going into the
batteries but it will assist in prolonging the battery life.
Couple of figures the battery manufacturer gave me (Shunhong
Electric Co.): Do not discharge below 12.3 volts.
Maximum voltage of the charger is between 14.6 or 14.9 volts.
A Method for Charging Batteries onboard Bike using
Minimum Parts of Jump Starter Units
Recently I was instaling a hub motor kit for Peter
Ravensborough of Brisbane Australia. We came up with a simple
charging circuit thats uses a minimum of jump start components
and allows the batteries to be charged without removal from the
bike.
This is how we did it:
Firstly we cut out the section shown in
dotted lines, this is a bit tricky as you have to be careful that
you dont cut any wires in the back of this section.
Then Peter has made up a neat little
box which holds two voltmeters (for a 24volt motor i.e. one for
each battery) from the jumpstarter units and all the wiring that
is found in the jumpstarter units which is connected to the rear
of the section we cut out from the jumpstarter units.
In the rear of the jumpstarter units there are wires going to a
car cigarette lighter, these can be removed as they are not
needed.
If you follow the cigarette lighter wires you will notice one
goes into a small white plastic box. Inside this box is a circuit
breaker which is used on the cigarette lighter plug circuit. The circuit breaker
is self resetting. It works on temperature and is very simple, if you exceed
about 20amps for a period of time it will disconnect the circuit. I have used
one on a bike and it was just about ideal current rating for ebike use. After a
minute or two it resets itself . The wires going to the circuit breaker can be
removed as can the wires going to the light (if appropriate some
jump starter units have no light).
The circuit breaker is a spring type steel and will reset
itself after it cools (maybe a minute or two to reset itself).
dont remove the charger board it will sit at the back of the part of
the plastic case to be mounted on the bike
Next the thick jump starter high current wires are removed (
the jump starter unit will now only be used for charging which is
a very low current approx. 500mA).
Then there will be two wires left, a thin black wire and a
thin red wire. The black wire goes to the negative terminal of a
battery and the red wire goes to the positive terminal of the
same battery. A thin wire can be used to connect to the battery
as only a small current will be flowing to the batteries when you
are charging the battery(s).
Finally the whole circuit can be put together as shown below.
A switch and fuse should be placed on the main wire going from
batteries to PWM (pulse width modulation) controller box. When
charging switch off battery connection to PWM. Place the 240v
adapters into the sockets on the voltmeters and batteries should
begin charging.
It will
suffice as a circuit breaker in electric bike applications, if
any can test exact current to trip it would be much appreciated.
IMPROVED JUMP STARTER BATTERYBOX
January 10th 2006: Just finished a new (improved) jump starter set up. Quite
a bit of work involved but a nice result if I say so myself. Below some pics.
Below: Most parts of the jump starter boxes are reused to make one big
batterybox.
The controller and some heavy duty switches (that come with the jump starters
are also used). There are 3 lots of 17ahr batteries (making 36volts) in the
box. A custom made box would be alot smaller as there is quite a bit of room
inbetween batteries in this box, but almost all of the plastic cases the jump
starter batteries come in are used.
Below: Batteries are not very visible but they are in series connected by heavy
duty wire and heavy duty switches.
Below: The jump starter autocutoff units are used on board the battery box. When
I come home from a ride I just plug in the power units and when its finished
charging the autocutoff units turn off the charger unit (the 240v plug that
supplies the power is not shut off from the mains but uses only a minute amount of power when
not charging).
Below: The black box is a circuit breaker (auto resetting type) that comes in
the jump starter units, fortuitously the circuit breaker only seems to open when
I've been going up a long hill for some time, seems to suit the ebike well. Two
of these in parallel might be a better option but suits the motor i'm using at
the moment.
The two black horizontal wires are part of a shunt, available from jaycar for
$10aud. They allow you to measure amps (current) using an el-cheapo multimeter.
Below: The three power packs (adapters from 240v) are visible in the background
at
centre-left of picture. I plug them into the plugs located on the autocutoff
boards. Led lights come on and when batteries are charged they go out. It would
be possible to carry the 240v adapters with the bike and charge up at the
destination.
Below: The basic circuit. SH= shunt (used to measure current with an
el-cheapo
multimeter). CB=circuit breaker from jump starter unit.
Below: The layout positioning of the battery box components.
Next to come: how to wire up the ammeter (using el-cheapo multimeter and
shunt) and voltmeters from jump starter kits. This is the easy bit! Will make
for a nice dashboard for the bike: individual voltmeter for each battery and
ammeter to measure amps (current): not many(if any)commercial ebikes have that!!!!
Voltmeter and Ammeter Setup
I've used the voltmeters from the jump starter boxes and the cheapest digital
multimeter I could find ($8aud from dicksmith: well they had two for $16aud on
special) (measures the amps via the
shunt).
The pictures below show the setup on the handlebars, I'm made a waterproof case
for them out of some plastic/foam/cable ties/ waterproof tape.
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