Iron Phosphate Lithium Batteries:
( will use PO4 as abbreviation in text below)
( please note that lithium packs/cells are ordered from manufacturer as needed, delivery time should be within 4 weeks for 2009)

Cell size recommended: 10ahr
Size of a 10ahr cell:

24v 10ahr pack with balancing charger
 $425aud and $80aud freight
Pack consists of 8 cells in series ( note wires for balancing charger
not shown on this pic) Weight 2.6kg dimensions: 111mm * 84mm*168mm ( H* L* W)


24volt 10ahr can come in a case with connections in place for balancing charger
Case shown below ( balancing charger connector not shown)

Pic of the case installed in an ebike:

36volt 10ahr PO4 pack with balancing charger:
 $635aud and $95aud freight

Pack consists of 12 cells in series ( note wires for balancing charger
not shown on this pic)

Can come installed in a case ( note cells arranged differently inside case to the
picture above)

How cells are arranged when inside a case:

Comes with balancing type charger:
Each cell has an led on the charger, when that cell is charged the led turns on.

Balancing connector on 36v 10ahr case

48volt 10ahr
 $845aud and $120aud freight

Consists of 16 cells arranged in series. Total weight of cells: 5.2kg
Cases not available from battery factory but I can organise a case to suit
( as shown below)
which the factory can install the cells and connectors into.


Balancing charger for 48v 10ahr case below:

Case shown installed in an ebike (organising this case may slow delivery time)

General and Technical Info on the batteries:

Lithium Iron Phosphate ( LiFePO4) type Lithium batteries although slightly heavier and slightly less energy dense than Lithium Manganese Oxide or Cobalt Oxide Lithium are thought to be a much safer type of lithium battery as the oxygen molecules in PO4 lithiums have strong bonds which require high temperatures to liberate the oxygen which is necessary for burning to occur. Cell phones and laptops in the past have been almost entirely of the cobalt or manganese oxide type, but after some fires in particular some laptop fires, some laptop manufacturers are also going with iron phosphate type lithium cells.

I think it wont be too long in the future and PO4 cells will be available in supermarkets like nicads or nimh are today.

I would strongly advise against using cobalt oxide or manganese oxide cells due to the large number of fires I'm aware of that have occurred in the past on ebikes using this type of cell. I did supply some cobalt oxide packs in the past and fortunately the packs had very good bms( battery monitory system) boards so no fires have occurred in the packs I have supplied. Though I am aware of many fires that have occurred in cobalt oxide packs that were using very poorly designed bms boards.

I have been fortunate to have been able to have access to quite a few cells from different companies over the last couple of years, and been able to try and work out which cells will be good quality but not too expensive, though PO4 cells are basically still very expensive. There are quite cheap cells available now but the quality is a big issue.

Iron Phosphate Lithium technology continues to develop and many new manufacturers are popping up all the time but the quality of iron phosphate cells varies from factory to factory. In particular I think its quite appealing that iron phosphate lithiums can be used without a bms  board ( battery monitoring system). Though I can supply with bms boards if required. My view is keep it simple, and bms boards add more complexity to a system that can be kept very simple.
To get an idea of the variations in quality of cells from brand to brand please see some excellent testing results done by Zeva in Australia: zeva.com.au/tech/LiFePO4.php

The functions of bms boards are:
1. low voltage cut off to protect cells from overdischarge
2. over amp protection
3. some bms boards I believe can have some balancing function when cells are being charged

All of the above functions can be taken care of without a bms board.
1. low voltage protection is built into ebike controllers which will shut off controller power the batteries reach a given voltage , although ebike controllers are set for sealed lead acid batteries the low voltage cut off is quite suitable for use with iron phosphate lithiums. Low voltage cut off of ebike controllers are :

24volt system: 21volts
36volt system: 31.5volts
48volt system: 42volts

The reason these cut off voltages are used is that sealed lead acid batteries are believed to be permanently damaged if they go below 10.5volts for each battery pack. Iron phosphate lithium cells have a working voltage of around 3.2 , fully charged the cells maybe slightly higher . 3.7volts is the maximum voltage you would want to charge up a single PO4 cell up to ( over this the cell will be damaged, expansion of the cell may occur, as I learned by experience). Cobalt oxide and manganese oxide cells have a working voltage of around 3.7volts, and fully charged can reach  over 4volts up to about 4.2volts.

So its quite easy to tell what type of lithium cell is by its working voltage: 3.2-3.4volts is P04 type, 3.7volts is cobalt or manganese oxide type.

2. over amp protection: a simple fuse will do the job

3. the packs I supply come with balancing chargers so no need for a bms board to balance the cells during charging. ( link; cell balancing )

PO4 Lithium cells can come in many sizes ranging from 18650 size ( 18mm dia 65mm long cylinder about 1.1ahr as used by A123 brand and valence) up to very large 200ahr rectangular shape cells (58mm*220mm*330mm)

For ebike use a 10ahr cell is a suitable size for a range of less than 25 to 30km ( range depends on many factors)
a 24volt PO4 pack using 10ahr size cells will consist of 8 cells: working voltage 3.2*8= 25.6volts
a 36volt PO4 pack using 10ahr size cells will consist of 12 cells working voltage 3.2v*12=38.4volts
a 48v PO4 pack using 10ahr size cells will consist of 16 cells working voltage 16v*3.2=51.2volts

Iron phosphate cells it seems 2.5volt per cell is accepted as the lowest voltage you would want to go down to without damaging the cells you can go lower ( maybe down to 2v or so) though its a safe voltage so as not to over discharge the cells ( though you will notice a very large dropoff in power before the cells reach this voltage. Lithiums tend to hold a fairly constant voltage until just before they they are exhausted and the voltage then drops off rapidly, so its necessary if not using a correct low voltage cut off to make sure as soon as a drop in power is noticed to not use the batteries further but to recharge it.

So acceptable low voltage cut off are:24v system: 2.5v*8 = 20v (compare with sealed lead acid batteries low voltage cut off is 21.5v)
36v sytem 2.5v*12 = 30v (cf sla lvc 31.5v)
48v system: 2.5v * 16 = 40v (cf sla lvc 42volts)

This means generally an ebikes controller will hit its low voltage cut off just a little higher than you could set it for iron phosphate batteries, hence protecting the batteries from over discharge scenarios.

Quality variations in PO4 packs from manufacturer to manufacturer:

Its seems the best PO4 cells on the market today are made by A123 company, followed by Valence company, both of which charge a very high price for their cells.
The A123 brand cells can be found in dewault power packs used in dewault hand held power tools, which is one source for high quality cells, though the packs used in dewault power tools are 36v and quite low ahr capacity.
A123 cells in particular can handle quite high discharge rates without overheating. One battery research company estimated that you can predict the life cycle characteristics of cells by the maximum temperature they reach. This info ithey worked out using A123 cells but I'll assume it will also be similar for other good brand cells. There results were:
60degree celcius ( 140F) is the maximum temperature a cell should go to without decreasing its life span, for each degree over 60deg  lifespan will decrease approximately 12 cycles ( data from one company ( FMA in usa) who researched into a123 cells). So this is for the best cells on the market, you could expect higher loss of lifespan for lower quality cells if cell temperature reaches over 60degC.

So Temperature plays an extremely important role in the lifespan of a PO4 pack or cell. Basically 60degrees should not be exceeded to get the maximum lifespan from a battery pack. The temperature a pack reaches is dependent on the discharge rate of the ebike ( set by the ebike controller). The higher the discharge rate the higher the temperature a cell will reach. Discharge rates are generally given as a 'C' value, where 1C  for a 10ahr size pack would be 10amp, 2C for a 10ahr pack would be 20amps discharge rate, 1C for a 5ahr pack would be 5amps, 2C for a 5ahr pack would be 10amps etc. In the past I've used a rough rule of thumb of using 2C as a safe working discharge rate for  lithiums which also applies for cobalt oxide and manganese oxide packs. A 2C discharge rate will keep the temperature of the cells quite low and give a long life of the batteries.

As it seems common that PO4 retailers think that if they advertise their cells as high rate discharge cells that it will mean they are high quality cells but  it really means very little as all PO4 cells can be used for high rate discharge, but the effect will be lowering the lifespan of the cells if their temperature reaches over 60degC . Really to assess the quality of a cell its required that temperature graphs are produced showing the temperature of a cell during discharging at different rates ( C rates ). So if a maker suggests that with  their cells you can go to 20C discharge rate, its most likely true you could do that, but certainly the lifespan of the cells will be  reduced depending on what temperature the cells reach.  It would be thought that if a cell can handle a high discharge rate it will be good quality, but its really a meaningless bit of information unless temperature curves can also be given.
Most PO4 cells will handle high discharge rates for brief periods without issue, but prolonged periods of high discharge are probably going to have an effect on the longevity of the cells.

To get some really detailed information on the more common cells on the market at the moment ( note that new makers are popping up all the time which aren't included on this link) please go to zeva.com.au/tech/LiFePO4.php where there are extremely detailed test results for the common brands. Note that some test results are for small cell sizes ( 18650) and some later testing was for larger cell sizes and its almost impossible to compare discharge graphs of a very small cell to a large cell, they have quite different characteristics.
One interesting thing but somewhat ( it would seem to me) countertuitive, is that smaller cell sizes can generally withstand higher discharge currents better, I would have thought the other way around, that a very large cell would handle very large discharge currents better, but its not the case. The smaller the cell size the more suitable for high C rate discharge. ( I have no idea why that is the case!! maybe something to do with surface are of the material in the cells and ability to transfer heat???)

I was fortunate enough to have zeva test some cells for me, and the results are shown below.   Its very hard to compare to the other cells on the zeva site as the cells tested for me were 8ahr,10ahr and 11ahr size, and the cells tested from A123 ( and others )were 1.1ahr size ( 18650) or 22660 size. But I'm quite happy with the test results which confirm that the cells are indeed quite good quality. The Headway cells tested on zeva site are similar ahr size, comparisons to those graphs these cells seem somewhat better.

Another interesting thing can be noticed from the test results. The prismatic type cells ( prismatic simply means that the outward appearance of the cells is rectangular in shape) have lower internal resistance then the cylinder type cells, and gave better results then the cylinder type cells during testing. The reason for the difference between the prismatic cells and the cylinder type cells ( although the material used in both is identical) is the way the sheets are connected inside the cells. The prismatic cells there are a number of what you could, I guess, call smaller cells inside them joined in parallel. With the  cylinder cells the company has not developed, as yet, techniques to  make multiple parallel connections inside the cell, perhaps due to it being more difficult being spiral wound in shape. Cylinder shape cells are also called Spiral cells, as the sheets inside are in a long spiral configuration and leading to higher internal resistance.

But..........after opening up some prismatic type cells to look at the structure inside, I note that in rectangular type cells the sheets inside are bent over onto themselves, which gives rise to a fold line in the sheets. Its my worry that lifespan of the cells maybe reduced by these foldines which may develop high resistances overtime, I have no data to back up this 'guess', just a concern that I have. The cells are completely sealed from the air, when the inner material is exposed to air, the fold lines fracture and become weak very quickly. So assuming that no air gets into a cell it may well be that the fold lines have no effect on longevity but i'm cautiously predicting some effect. The cylinder cells being spiral wound dont have this issue. So I've decided to go for supplying the cylinder cells although resistance is somewhat higher, if used below 3C discharge rate there is no significant difference between the rectangular or cylinder type cells in my view. I wouldn't recommend using the cells over 3C rate though as the lifespan maybe reduced due to the temperature the cells reach (as will apply to any PO4 brand of battery).

For higher discharge applications I am looking into some other PO4 cells which should have very similar discharge properties to those of A123 cells, but  I need to have some tests done on those cells before will put them up for sale on this website. So the cells I have for sale are not as good as A123 ( working on finding some cells that will match A123.......but not as expensive...........not an easy task!!) but I'm confident the cells/packs I'm supplying at the moment are of high quality.

I can supply A123 cells if requested, there are two different cylindrical type cells ( both are the same size 26650 i.e. 26mm dia and 65mm length)
Cells are 3.2volt and 2.3ahr nominal.
White cells are $10usd each, and black M1 cells are $12usd each. It would require the customer to make up the packs themselves from the cells.
Balancing chargers can also be supplied: 24v to 48v.
You would have to check with me on availability as it depends on suppliers stocks.

Some reasons for variations in quality from different manufacturers:

1. raw materials used
2. mixture/blend of the raw materials
3. apparatus used to deposit the materials onto the base materials
4. baking ( oven ) process
5. curing time
6. packing of sheets into cases/connections
7. quality control : charge/discharge cycles to test cells before being leaving factory

Structure of PO4 cells:

PO4 cells are really two thin sheets of metal: copper and aluminium ( these sheets are very similar in thickness to aluminium foil you buy in the supermarket, probably slightly thicker)
There is a very thin ( measured in microns) layer deposited o