Where to get Sealed Lead Acid (Absorbed Glass Matt type) batteries :
last updated
Sunday March 1st, 2009 ( missing pictures below I haven't transferred across
from old website as yet)
Its not a good idea to use gell type sealed lead acid batteries 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 ( I've heard some reports that newer types of gel
cells maybe ok but so far my experience has been they are not very suitable for
use on ebikes.
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).
I recommend strongly that if buying sla type batteries that you check the
voltage of the battery pack before buying it, if the voltage is 13volts, it
means the pack is new, anything less than about 12.8 or 12.9 volts means it has
been sitting on the shelf for some time. I wouldn't buy a pack that has a
voltage lower than 12.8volts
Some years ago I confirmed with one manufacturer of the jump
starter batteries (shunhong brand) that jump
starter batteries are Absorbed Glass Mat (agm) type.
If want to buy sla batteries from a local source I would suggest to
try Alco battery dealers in australia, fridge and solar in queensland also ship
at good prices, I try not to supply sla batteries as the freight costs
are high due to the weight of the batteries.
Deep Cycle Sealed Lead Acid Batteries are commonly available
nowadays a more correct term for the batteries is VRLA, valve regulated lead
acid batteries,
or commonly called sla ( sealed lead acid batteries). Valve regulated simply
means there is a rubber cap on each cell which keeps the cell gases under a
slight pressure but still allows gases to escape if pressure builds up. The
interesting thing is that the oxygen and hydrogen produced in the battery
recombine to form water, so that topping up with water is not necessary, and
hence the batteries dont have screw type filler caps on each cell, but you can
still refill them by prizing off the plastic cover to expose the rubber caps. If
you want to maximise the life of the batteries it is necessary to add
electrolyte ( or just pure water) but only after maybe a year or so, and only
the cells near the positive terminal which tend to loose more electrolyte by
gassing to the atmosphere. Slower charging will reduce electrolyte loss but most
ebike chargers will cause some gassing as recharge periods are too long if
charged slower. Ideally you want a very slow charge time, the chargers that come
with jump starters are very slow charing ( usually 500mA to 1amp), ebike
chargers use more amps, it can take a very long time if using the jump starter
charges, new batteries might take almost 24hrs to charge. Hence you can see why
ebike chargers are higher amp usually so that a recharge will occur in 3 to 4
hours.
The cheapest source of Sealed Lead Acid Deep Cycle batteries
is to buy three 12volt and put in series to give 36volt or two 12volt to give 24volt
, or 4 lots of 12volt in series to give 48volt pack.
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). Theres also usually a self
reseting fuse and a few other bits and pieces that can be handy. I would
recommend though to get an ebike charger for whatever voltage your running on as
it reduces the charging times, and are much simpler to set up, as they are made
for the specific voltage ( eg 24v, 36v or 48v)
Which Type of Jump Starter pack to get:
1.If the jump starter pack has 900amp written on it , it should contain 17ahr
battery size.
2.If the jump starter pack has 600amp written on it, it should 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/new
battery. If its been sitting around in storage the voltage will be lower, if the
voltage is less than about 1 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.
I've tried to take some measurements to work out exactly how old a battery is (
how long been sitting on the shelf) but its extrememly difficult to get an exact
age from battery voltage. Just as an example of some measurements I did:
One fully charged sla agm battery ( 13v) took 3 months to drop to 12.8volts
without use.
Another took 1 year to drop to 12.6volts.
The rate at which the voltage drops varies over time and it varies from battery
to battery, so pretty much impossible to give an exact age from voltage. Best
bet is to buy a pack that has 13volts, its very unlikely a retailer will charge
up jump starter packs, so that would ensure the pack is quite new. I would go as
low as 12.9volts but if lower I wouldn't buy them. Buying a jump starter pack
that has a low voltage will mean your buying a battery that wont last as long as
one that has a high voltage when purchased, the batteries have a shelf life
which is thought to be a couple of years if not charged during that time.
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
Supercheap autos does sell auxilliary battery switches similiar to the ones
found on jump starter packs and are rated for very high amp useage.
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 long do sla agm batteries last?
My experience is you will get 12 months before noticing significant drop in
range ( capacity), it does depend on how you treat the batteries also, slower
charging is better for them, also best not to leave them in undercharged state
for long periods. Keeping the batteries charged straight after each ride will
help with longevity.
If the batteries will not charge up to 13volts then they need some attention,
you can rejuvenate them quite easily. Simplest method is two deep cycles down to
10.5volts followed by immediate recharge, that knocks off the sulphate deposits
and they are good for another 3 months or more. You can also add water to cells
that have lost electrolyte, usually cells near the positive electrode will lack
some electrolyte after a year or so ( but only need to just cover the top of the
matting inside the cells). They are called sealed lead acid but you can take the
lids off ( careful though as asbestos is commonly the matting material).
Some expensive brands of sla will last much longer, some reports of about 5
years for a german brand ( name i forget off top of my head).
I've had some sla batteries I've used for well over 2 years which were from jump
starter units but I did rejuvenate them and add electrolyte, also used a
desulphator unit on them. Iron phosphate lithiums are probably the best
batteries to use though due to their lifespan and safety, but they are
expensive, so sealed lead acid are a good alternative but they do have a much
more limited life and are quite heavy compared to lithiums.
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.
Jump Starter Charging Boards
I've noticed that the chargers that come with jump starter units may not work
properly if you mix and match with other jump starter units, each jump starter
has a
small circuit board inside it information on them below:
Thanks to Jeff Pethybridge for supplying the following information on the cicuit
boards used in the jump starter units:
from jeff:
All three PCBs
are the same size with the red LED , the power input connector and the relay all
on the same place on the board so each will fit in any of the cases.
The 900ah diagram from a yellow case has a built in current limiter set at about
700ma.
The green LED comes on when there is a useful charge current of 500ma or more.
The red units use a resistor to limit the current but with too high an input
voltage the current can allow the power in the resistor to go well above its 2
or 3 watt limit.
Two of these units have the power resistor melted to the case of the relay. I
suggest that people move the resister to the back of the PCB in clear cooler air
away from the relay.
None of the three circuits will reconnect the battery to the charge voltage
without powering off the power pack for 20 seconds or so.
I can not see any of these three ever turning off due to a full battery ( > 14.6
to 15 volts) when connected to a car lighter lead as the auto voltage never gets
high enough to trip the over voltage/charged relay.
Below one project I did using lots of parts from jump starter packs, this
particular project was using 3 lots of 17ahr jump starter batts, the
project got a bit complex as I worked out a circuit which would give regen
braking from the brushed hub motor I was using, the circuit landed up being
probably way more complicated than
it had to be, but was an interesting exercise non the less. You can see the
small circuit boards from the jump starter packs, I pretty much made use of
whatever parts I could in this project, the high amp switches, the circuit
breakers ( restting type), I found the circuit breakers were temperature
dependent, they would disconnect the circuit if it was under high load for some
minutes ( from memory approx 20amps for a few minutes and they would click then
a few minutes for them to cool off and reset).
On the same project the voltmeters were used to monitor battery voltages. An el
cheapo multimeter was used as the amp display.
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