It’s about time we stop worrying about how long these (LiFePO4) batteries will last…
There’s a lot of interpretation that can go awry with that line, so let me explain. And also bear in mind that this in an opinion post (my opinion at that), and it’s based on what I know, what I expect, and what I read from others in the know.
LiFePO4 chemistry is normally rated to at least 2000 “cycles”. When they say cycles, that’s a cumulative 100% discharge and recharge of its capacity. So if you discharge 100%, then recharge 100%, that’s one “cycle”. Also if you discharge 40%, recharge 30%, discharge 40%, recharge 20%, discharge 20% then recharge 50%, that’s also one “cycle”. When manufacturers say “10000 cycles at 20% DOD”, it’s a misrepresentation of the term, it’s still 2000 REAL “cycles”. That bugs me, but the industry has latched onto that terminology.
The 2000 cycles is also a rating based on test conditions, so if you operate the batteries outside of their test conditions, that can affect the cycle count. Normally the test conditions are 20-25 deg C, and using 5 hour charge/discharge rates.
The other thing that can affect how many “cycles” you get, is where in the range you use the energy. For example, using from 75% down to 25%, will achieve better longevity than using from 100% down to 50%, or from 50% down to 0%. I’ve yet to find reliable and accurate data on how much effect this has though, so I won’t make assumptions on if it’s a 2% or 20% difference.
Providing you size your system correctly, und you use it correctly, your battery pack will very likely outlast the technology and your ownership of the vehicle it’s installed in. Here’s why…
If you have one (or multiples) of my Scout batteries, and you use 50% of its power every day, you will get about 2000 “cycles” (in fact it will be more than 2000 “cycles”). Because you’re using only 50% each day, you’re actually going to get more than 4000 days of use. That’s about 11 years of every day use. Most people will also not be using that much every day, in fact many people I speak to, are only using 10-20% each day. On top of that, in an RV type situation, there’s going to be a lot of time you’re plugged into mains, or the RV is parked not being used.
Ask yourself… how long have you owned your RV? Most people seem to change every few years, there are exceptions though. But even then, to have a battery last more than 10 years, is pretty much a lifetime battery.
In 10 years time, we will see battery tech become so much better, that people will laugh at us using LiFePO4, the same way as people laugh at people using Lead Acid or AGM now. And they will be so much cheaper, lighter, more efficient, etc for the same usable energy.
So when people ask about how long a warranty is, it’s kind of a moot point. If a battery is going to fail due to a manufacturing fault, it will fail within the first few days, or weeks of being used normally. If it’s borderline, it will fail after the first few heavy use events. But for a battery to suddenly fail after 3 years, something is being done wrong to have caused that.
We provide a 6 year warranty on our batteries. We also individually test every single battery at various stages throughout its build. All the cells get charged and top balanced during assembly. After the initial assembly it gets a high current load for fault checking and IR testing. Then it gets 2 full 5 hour discharges and charges to get the capacity we rate it at.
Most of the “off the shelf” batteries available, will have a small percentage of the batch tested, and even then they don’t seem to test at the extremes, which is exactly how they need to be tested. So if there’s a random manufacturing issue, or someone has made a slight design change without fully testing it, the Australian distributors may not see that. This is something I found on a recent battery test, the BMS wasn’t rated correctly, and the wiring was too small, yet the Oz distributor would have never known if this test was not done. But something like that, could be an issue when someone needs that full capacity.
