Comparison between Lithium and Lead-Acid Battery

I. Lighter and smaller

Compared to the lead-acid battery, the LiFePO4 battery is 1/3~1/4 in weight and volume but 5 times more efficient. On top of that, it is portable due to its light weight and has a lifetime 5-10 times longer than that of the lead-acid battery.

Battery

Lead-Acid (SLA)

Lithium (LiFePO4)

Capacity

10AH(36V)

10AH(36V)

volume

6.12dm3

1.66dm3

Mass

Approx. 13KG

Approx. 3.8KG

Capacity density

80-100 WH/L

350-400 WH/L

Mass density

30 WH/KG

150 WH/KG

 II. Long life

A typical lithium can be charger more than 1500 times (100%DOD) and retain more than 60% of the original cell capacity. A lead-acid cell, however, can only be charged 300-500 times before its capacity drops to 60% (100%DOD). We choose the Lithium battery mainly because of three reasons:

    1. The material is superior but much more expensive. However, we expect that the cost shall be cut in half in three years. 

    2. Each Lithium cell carries a higher voltage with greater consistency.

    3. There is no loss of acidic steam.

 III. Low internal resistance

The internal resistance of one LiFePO4 cell is less than 6mΩ and that of a whole battery set is less than 80mΩ. Therefore, the Lithium battery set can provide much more power when heavy power is needed, such as initiating and climbing. For a whole set of  lead-acid batteries, however, the internal resistance reaches, on average, 200mΩ upon 10A current discharge. On the other hand, a lithium battery can provide 12W with the same conditions, thus the lithium battery provides more power for quicker initiating, climbing and acceleration.

 IV. High voltage

The working voltage of a LiFePO4 cell is 3.7V, but that of a lead-acid cell is 2V. There are several cells combined in a roll under tandem so as to better ensure consistency. Therefore, when a Lithium battery is being assembled, it has a greater capacity and a longer life cycle than that of a Lead Acid battery. 

 V. Low temperature resistance

Lithium batteries can discharge soundly at -20℃ (According to tests, they can discharge over 95% of its capacity at -20℃ and even 90% at -40℃). Lead-acid batteries, however, can only discharge less than 60% at 0℃.

VI. Heavy Electric-Current discharge

A lithium battery can discharge up to 25A without affecting its life cycle, but a lead-acid battery can only discharge 15A. Most power boards in the market place nowadays take more than 30A to function well which potentially shortens their battery life. It only take around 8A or less to run our power boards on a flat surface.

VII. Low self-discharge

The self discharge of a lithium battery is 6-8% a month and that of a lead-acid battery is 15-20% a month. Therefore, after being fully charged, it can be stored longer than a lead-acid battery.

VIII. No memory

Lithium batteries can be charged any time, absolutely free of charge memory.

IX. Environmentally friendly

Lithium batteries are free of leakage, pollution and from harmful heavy metals, such as cadmium, lead and mercury. There is no contamination during the course of production and application. According to the Eco-Mark Authentication Center, the lithium battery is currently in position to be recognized as a green and ecologically friendly product. The lead-acid battery, however, is not recommended as an environmentally friendly battery product.  

X. Quick charging rate (being developed- proposal of Xinri Company expected)

The newest lithium battery can be charged at 10A/Sec. Now, a quicker charger is under development, which could charge a Lithium battery in 2 hours or less.

 

I've got a different brand of board to the ones shown on the greenskate site - can i convert mine to use a lithium (LiFePO4) battery pack ?

 

Absolutely! Any electric skateboard type or brand can run on LiFePO4 cells ... the motor controller isn't picky, it just expects 36+ volts and plenty of current.

The battery only needs to be able to put out 45Amps constantly for the 800watt board (generally once up to speed the motor is drawing 20-25Amps)...and for the new brushless motor boards, even less current is required :)

The reason why some manufacturers make statements like "the Lipo battery needs to be able to put out 80 amps to work with our boards", is because alot of manufacturers originally put 10AH LiFePO4 packs (made up built from the small 26650 type 3.2V 3Amp cells) on their boards, and those packs struggled to deliver the 45Amps constant and would burn out the controlling BMS (on the battery) frequently and deliver erratic performance, also the voltage would drop below the cutoff for the motor controller which would stop the board.

We trialed the small cells a few years back, realised straight away they were too small and went to large Headway cells (10AH rating, with the ability to discharge at 100Amps!) which work VERY well.... to date, no other suppliers offer Headway cells (or even 20AH packs) as an option - most still build their packs based on small cells.

Then for people who want even better performance we started offering 20AH packs which are pretty much perfect for an 800watt board - they have no trouble delivering the high current (they can discharge quite happily with no drop-off in performance at 60Amps constant).