For long LiFePo4 battery life, you should be mindful of the following:
- In order of importance follow these steps
- Keep the battery temperature under 45 Centigrade (under 30C if possible) – This is by far the most important!!
- Keep charge and discharge currents under 0.5C (0.2C preferred)
- Keep battery temperature above 0 Centigrade and below 30C when charging & discharging – This, and everything below, is nowhere near as important as the first two
- Do not cycle below 10% – 15% SOC unless you really need to
- Do not float the battery at 100% SOC if possible (it causes bloating in as little as 6-12months)
- Do not charge 100% SOC if you do not need it
- Clamp your battery cells together to prohibit bloating. Especially for batteries that see a lot of use.
That is it! Now you too can find happiness with your LiFePO4 batteries!
Are the Cells new?
We sell mostly new cells, Currently, EVE, Ganfeng are two of our new cell suppliers. And that is because they are the only ones that can be obtained in Automotive Grade. We sometimes make the decision to supply the much cheaper Storage/B-grade cells for some applications especially camping and off grid purposes, but we are upfront about this, and we do guarantee the cells with a warranty. We will never misrepresent our cells. And it’s likely we will be cheaper than other sellers in Australia in that case.
You may think you are buying new Automotive Grade A cells from Alibaba and AliExpress and other sellers even in Australia, but it’s almost 100% you are buying Storage and B grade or in some cases, ex Bus or UPS cells that may have been used and dismantled and then rewrapped. Especially CATL, as they most often appear as used cells, but it can be any cells.
If you use the internet, you can find almost anything, and the chances are that cheap cells are bad cells.
IMPORTANT NOTE for camping batteries.
If you are using the cells for camping purposes. You will probably only use a few cycles each time you go camping. This type of battery does not need to be rated for 6000 cycles, even if you go camping for 60 days a year, you might only do 30 cycles. At that rate, it would take you several lifetimes, to use the cells to a point where they still output 80% of their original capacity, and calendar aging will eventually kill them anyway.
An example of this is that I have been using my 200ah cells on a daily cycle for almost 2 years, and they still have only done about 200 complete cycles. They likely have another 10+ years in them. They have 1C or 200amps pulled through them about 20 times a day for a coffee machine. They still have 95% stated original capacity.
B grade cells may already have degraded to 85% by this stage, and remember it only takes one weak cell, to pull the whole pack down. That is the biggest issue with battery packs in series, the more cells in the series eg, 16 cells, only a single cell needs to be degraded for you to loose that same capacity x 15 for the other remaining cells.
If you don’t want the hassle and you are a serious camper, then by all means get an automotive grade, but for 12v it can also be ok to choose the far cheaper option of B-grade cells. the higher the voltage of your battery, the more you should want to get only the best cells. Because only 1 bad cell pulls the rest down, and can kill a battery.
I would imagine many campers, may only use 20-50 cycles over 5 years or even more. But the best thing about LiFePo4 is that they are much happier to sit without a full charge for 12 months or more, than a Lead Acid equivalent.
They have a much better shelf life than any Lead-based batteries and they are much lighter in weight too.
One of my favorite things about LiFePo4 is that it takes about 98% of the power from the solar charge controller, whereas, Lead-based can need a lot of absorption, many times they need twice as much solar to stay within the usability range of the very heavy lead acid with only 50% usability of the AH rating of that battery.
What happens if you draw more amps than a cell is rated for?
Exceeding the battery’s rated discharge can lead to an increased heat generation, too much heat in a cell will decrease capacity by a significant amount.
Using the example on a 280ah EVE cell, it would expected 30-50w of heat would be generated internally at 0.5c-1C draw. This is significant.
Here is a report funded by the National High Technology Research and Development Program (863 Program) of China (No. 2012AA110203) and the National Natural Science Foundation of China (No. 51634003).
IN SUMMARY – Yes you will damage and degrade the battery life, by how much depends on all the things you would expect, the C rating, the timeframe, and the temperature, and some cells are designed for 0.5C and some for 5C so its all relative.
How do I safely charge a LiFePo4 cell
A LiFePo4 cell needs to be charged above its nominal voltage of 3.2V, anywhere from 12-15% above would be considered safe and appropriate. LiFePo4 has a low internal resistance, meaning it will accept the charge, more easily and quickly compared to an SLA or Lead Acid. Lifepo4 chemistry does not need an absorption stage, but it can be floated at 100% SOC, between 13.6v-13.8v. However, it will see more degradation than if it was between 30-70% SOC
The best charge voltage for 12v (13.2v) 24v (25.6v) and 48v (51.2v). Multiply 3.65 x the number of cells
1. 12v (13.2v) 14.6v
2. 24v (25.6v) 29.2v
3. 48v (51.2v) 58.4v
As all LiFePo4 batteries are controlled by a BMS, usually with minimal balancing, It is recommended to charge the Battery slower if possible, especially when nearing the 100% SOC. Most LiFePo4 cells are rated for a maximum of 0.5C charge.
If you are unsure what C charge means, you can think of 0.5C as 50% of the capacity of the cell.
What Brand are the Cells?
We use, sell and recommend these Brands
EVE, GANFENG, BYD, WINSTON, CALB, HITHIUM, CATL, SVOLT, GOTION and many more, there are at least 20 more manufacturers in China. Usually considered Tier 2.
When Australia and other countries begin to Manufacture good quality batteries, we will of course sell those.
What Brand is the BMS?
We use, sell and recommend, JBD, JK BMS, REC, Daly, HelTec, Chargery, SEPLOS, PACE and others because sometimes it depends on the use.
How to TOP balance LiFePo4
- Hook up the LiFePO4 cells in parallel – that means connecting all the positives together and the same for the negatives
- Charge to 3.45 volts with a regulated DC power supply with overvoltage protection. This part takes a long time! And your power supply should be large enough to cater to your needs. This 30amp Lab supply is voltage and current limited here.
- Once it hits 3.45v, then adjust the target voltage to 3.65v, keep an eye on the cells during this stage, the voltage will rise very rapidly and it’s good not to rely solely on the overvoltage protection feature of the power supply. Check with a multimeter very regularly.
- Once you hit 3.65v, turn off the power and leave for an hour or more. Check to see if it’s still over 3.5v. If not, charge it up to 3.65v again and leave it for another hour. Repeat until it does.
- Once done, reassemble the pack into your desired battery Voltage eg. 12v or 24v, and discharge
- Storing at a high level of charge is not good for the LiFePO4 cells. If storing for a long time, discharge down to 30-50%. If possible, keep the battery below 90% SOC and above 10% SOC. It will increase the lifespan of the cells. And definitely help with cell bloat.
Congratulations you have successfully manually top balanced.
An alternative (not recommended) way to top balance a battery pack with a BMS, such as the JBD BMS is to connect the battery cells in series, and slowly, incrementally increase the pack voltage inside the Bluetooth app. (occasionally this will not work if the cells are at different SOC, please be aware, it could take weeks to balance if that were the case, and therefore it’s not usually recommended unless you don’t have any access to an appropriate voltage limited Lab supply)
1. Wire up the Battery in series. Eg, connect the 4 cells (positive to negative) Which will create a battery of about 13.2V for a 4s LiFePo4 Battery.
2. Charge with a charger between 14v and 14.6v. Slower is better
3. Inside the JBD Bluetooth app (XiaoXiang), set the fully charged voltage to 3.45v, and a total pack voltage of 13.8v and charge it until the BMS stops. Inside the app turn off the charge balancing feature and leave until all the cells are balanced.
4. The following day or more inside the BMS Bluetooth app settings increase the pack voltage to 14.4v (3.6v per cell) or 14.6v (3.65v) and ensure the balance on charge is turned off. The battery will then go and top balance itself. Leave here until balanced
What are P- C- and B- on a BMS
B- is where you connect the main Battery negative of the pack of cells, so you have to use that for that purpose, and only that purpose, if you want the BMS to be able to protect your cells.
C- is where you connect the charger to Charge the battery.
P- is where you connect the controller to Power it from the battery.
If the BMS has a common charge/discharge (charger/controller) port, then you only need to use whichever single wire / pad goes to that port for the Charge input and Power output connections. This may be either C- or P- or it may have a completely different designation and not even have a C- / P-; the manufacturer instructions for that specific BMS must be followed. You still have to use the B- for the Battery negative of the pack of cells.
If the charge and discharge ports are separate, then you must use the correct port for the correct input or output connection.
If you do not do it this way, then your cells are not protected against overcharge and/or overdischarge, depending on how you miswire it.
Here is a pdf file you can download to choose your optimal cell configuration
After building any battery pack
Remember! that about a week after the battery pack is installed, it is necessary to double-check that all battery terminals and the busbars are still tightened, because once loose, there is a risk of causing high resistance connections, which can reduce the performance of the battery pack. At the same time, there are also some risks of electrical fire, and specifically undesired heat.
Warranty on cells – Our warranty varies based on the grade of cells, but all warranties are pro-rata.
That means that the warranty amount is based on the age and usage of the cells.
As Lifepo4 cells have maximum and standard charge current rates, no warranty will be valid if you exceed the maximum rates.
In order to be eligible for a warranty, you must have planned and used the cells according to the specifications sheet for that cell.
You must understand rechargeable batteries have a service life, and as such, they will degrade over time and usage, they are likely to change shape and bloat over time, and this is more likely without compression, this is not grounds for a warranty claim, as you yourself will have created this scenario. Even with compression LFP cells will bloat with age and usage with discharge and charge rates over 0.2C. We aim to be fair with the warranty, that is the intention, and we are very happy to sort out any issues early in the process, as this is when the cells are less likely to have been used. As the cells age, there is a much smaller chance of a warranty claim being approved, as you have already been in the use of the cells for a period of time, and as each cells is unable to show how you used it, we can simply refuse a claim on the grounds they are a consumable item, and that we cannot know if the cell is used in accordance with the specifications sheet.
Example of Charge Ratings based on Temperature of LFP Cells.
BE WARNED This is an example taken from a popular 100ah 3.2v Prismatic cell, you can see from the table that temperature plays an enormous role in what charge rate a LFP cell should be charged with.
News and Blog Articles
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