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LiFePO4 vs LITHIUM ION

Posted on 4th Dec 2015 @ 10:44 AM

Many ask "Why LiFePO4?", To me the answer is simple. Double the Life Cycles!

A liFePO4 battery is expected to last twice as many life cycles as a Lithium Ion battery.

lifepo4-vs-li-ion-600w.jpg

 

Please note this may be a long read but well worth it if you are considering buying a battery pack as it is usually the most expensive component on your Ebike.

After many years of experience with batteries I have come to realize safety, reliability, life span and long term cost are what is most important to us. In this article I will address several things I feel that are important but rarely ever mentioned

LIFE CYCLES

There is always new technology with batteries coming forth and a lot of excitement about the latest in the 18650 Lithium cells. I welcome any battery advancement because without batteries we don't go anywhere. Most articles and reviews speak of the important things like voltage, watts, amps and amp hours. I do agree these topics are all very important but there is still one glaring hurdle that can't be overcome with Lithium Ion and I have yet to see it mentioned in any review or advertisement. That glaring omission is "Life Cycles". A liFePO4 battery is expected to last more than twice as many life cycles as a Lithium Ion battery. I could specify numbers here but instead I have provided links to Wikipedia specifically discussing these battery technologies. By providing these links it allows you to go read the details about each technology without leaving out any of the facts

Click here for the Lithium Ion Wiki - Read the section on Battery Life. 500 cycles

Click here for the LiFePO4 Wiki - In the Specifications section read the part on life cycles. 2000 + cycles

Click here for the Lithium battery Wiki - Comparison Chart - See "Cycle durability. 1000-2000 cycles

When researching batteries look for cell type and rating. If the vendor simply states it's a lithium battery, this means very little. There are many 18650 cells out there with various ratings from 1900ma to 3400ma. The higher the number the more distance you get from each cell. So these numbers make a huge difference as well as who is the maker. I do notice the latest Panasonic versions are estimated at 400-1000 charges and the Samsung at 300-700. Most vendors forget to mention these numbers. Especially on the larger more expensive packs.

So even with the best cells and the best warranty I still have great concern on the life cycles. Especially if the life cycle rating starts at 300 charges. You have to consider if you ride your bike everyday it could be well within the expected rating of the pack that you may need a new battery every year or two, instead of every 3 to 5 years with LiFePO4.

If you compare the cost of a LiFePO4 battery to the cost of a similar sized Lithium Ion battery the cost of the LiFePO4 battery is about 10-20 percent higher. So you have to ask yourself, is the 10 to 20 percent higher cost of LiFepo4 worth the battery lasting 100-200 percent longer? Considering the battery is the most expensive component in most Ebike builds it is something that deserves consideration.

WARRANTY

Look for a description of the warranty on the site. If the site does not say what the warranty is you should have a reason for concern. For something as expensive as a battery the warranty is very important. Some vendors don’t mention warranty at all, others say “Warrantied against manufacturers defect” with no time specified. What does that mean? Some websites bury their warranty statement so deep in their website you can not even find it. A simple google search of the vendor name and the word warranty will usually bring it up. Something like "goldenmotor.ca warranty" without the quotes works quite well just change the website name to the one you are considering buying from. If the batteries they are selling are as good as they say they are why is there such a limited warranty or no warranty at all. Some say to cut costs. Is the price that different from our longer lasting fully warrantied batteries?

SAFETY

Another thing you will find when reading about lithium is it is always stated as safer. But rarely is it mentioned safer than what? The fact is LiFePO4 is safer than Lithium Ion and is the safest of all current lithium battery technologies.

RELIABILITY

How about reliability? Our LiFePO4 cells are extremely reliable and have almost zero issues. The 48 volt 10 amp batteries have always come with a 30 amp BMS which everyone seems to be bragging about these days. Also you should consider how the packs are made. Most battery packs have rows of round cells machine soldered together. How would the average consumer ever repair a battery like that? Our LiFePO4 packs are made much different. Have a look at this picture to see how our packs are made and how easy cell replacement would be if you had to repair a battery. You can also click the picture to see a full thread on what is inside our batteries. You will not find any other batteries built this way.

48v10-inside.jpg

52 VOLTS?

A lot of people mention the new 52 volt packs. Manufacturers have added an additional cell to the 48 volt lithium packs stating this pack will now make you go faster than with a 48 volt pack. This may be true if you are comparing a 52 volt Lithium pack with a 48 volt lithium pack. The nominal voltage and max voltage of the 52 volt lithium pack is higher than the 48 volt lithium pack. Considering voltage is speed and amps equals distance you should go faster with a higher nominal voltage. What is not mentioned is when adding the extra cell to the pack the lithium pack is now at almost exactly the same max voltage as a 48 volt liFePO4 pack. But the nominal voltage is lower than the 48 volt LiFePO4 pack.

Look at these numbers. They are not made up and can be found all over the internet.

Lithium 52 volt pack is 14 cells in series or 14s.

Nominal voltage is 3.7 volts x 14 cells = 51.8 volts

Max voltage is 4.2 volts x 14 cells = 58.8 volts

LiFePO4 48 volt pack is 16 cells in series or 16s.

Nominal voltage is 3.3 volts x 16 cells = 52.8 volts

Max voltage is 3.65 volts x 16 cells = 58.4 volts

The nominal voltage is generally where the pack voltage drops to only after a few minutes of riding. It then stays right around that area until near the end of the charge and then drops off dramatically until the BMS kicks out the pack to protect the cells.

If people are going to call a lithium battery with a nominal voltage of 51.8 volts a 52 volt pack then the same logic could be applied to calling a liFePO4 pack with a nominal voltage of 52.8 volts a 53 volt pack. So let’s call our pack 53 volt LiFePO4 battery pack. Now which one would be faster?

HIGH ENERGY DRAIN

Although it may be true the newer lithium Ion packs can handle a much faster high energy drain then the LiFePO4 packs the reality is the rate of the drain from the battery is dependent on the motor controller not the battery. The battery does not shove power into the controller. The controller takes what it needs and nothing more. Unless you are building a High powered Ebike your motor will never be able to use that power. Even a 1000 watt off-road Ebike will never be able to take advantage of these high energy drain packs. On average a 1000 watt motor peaks around 1250 watts or 25 amps. Our packs are rated at 3C continuous and 5C peak. So for a 48V10AH battery that is 30 amps continuous and 50 peak. But with the default setting on our 1000 watt kits you will never need more than 25 amps of power. Keep in mind as well if you do a little research having an overpowered Ebike motor that does use the high energy drain on battery packs dramatically shortens the life cycles.

Also please note: If you intend to build an illegal Ebike for the street you are taking on a lot of risk. Everyone says the police have a lot more important things to do than check the power of their Ebikes. That may be true until the day you slam into a baby carriage. At that point everything changes. Think about what you are doing.

TO SUMMARIZE

I am not against the new battery technologies. I am excited about it and look forward to further improvements. I have seriously considered selling them and may do so in the future. I just feel there are a lot of things not being mentioned when it comes to the benefits and drawbacks of this new technology. If I do sell them in the future I will still leave this article up so people can read all the facts and understand the difference before they make their decision on lithium or liFePO4.

So a great price for this new technology is not what it seems to be. What I am hoping for is once these new cells become more main stream the cost will drop to half the price of LiFePO4. Then a battery that is rated to last less than half as long would make sense.

Gary Salo

Golden Motor Canada