This is a very short post. You might visit this post because you are searching for a solution to your problem: your LiFePo4 batteries aren’t charging. The problem might have a root in a super simple cause. I’m sure that if you are a “pro”, you might be able to handle it properly, but if you are a first-time DIYer like me, your thousand bucks batteries aren’t charging could freak you out a bit, as it did to me.
It all started one cold winter morning. The outside temperature was minus 4 °C (24 °F). I plugged the shore powering line into my car from last night, intending to charge the LFP4 batteries to full. But, to my surprise, my battery banks weren’t charged. It depleted instead. I thought there was a problem with the power so I plugged in another device in order to test it. I still have power.
Then I thought there were faults between the CEE adapter and the charger-inverter, the charger-inverter was defective, or a loose connection somewhere. Everything is perfect. That’s when I freaked out. Were my thousand bucks batteries dead? Sh*t, I didn’t even use it for a long trip and now wasted more than a thousand! I was hopeless.
I plugged the shore power line again and left the house, hoping for a miracle. A few hours later, I returned home to see no miracle at all. Now that’s the funny part. It was freaking cold when I was busy checking for the problem. So I started the engine to get some heat. After some 10 minutes of checking around, I suddenly heard a BEEP tone from the inverter-charger, and my batteries were charging again.
Oh yes, I read a lot about LFP4 batteries before, but my head seemed to stop thinking when I freaked out. The LiFePo4 batteries have a popular weak point: they don’t charge very well or not charging at all when the temperature is low. It is advised that one should never attempt to charge the batteries if the temperature falls below 0 °C (32 °F). In my case, my batteries’ internal BMS (Battery Management System) stopped the charging process to protect the cells.
So, if the outside temperature is very low, under freezing point, don’t panic as I did. Try to warm up the batteries using a safe method (blow warm air, or wrap the batteries with a thermal blanket). Sometimes because of the cover, the inside cells might not be able to warm up as quickly as you expect. If you can read the batteries’ information from the manufacturer’s app or an integrated/external display, ensure the cell temperature is warm enough before charging again.
Remember, the proper charging temperature for LiFePo4 batteries is between 0 °C to 45 °C (32 °F to 113 °F). Too low or too high will damage your batteries’ cells, or if BMS is available, it might not let you charge the batteries. I hope this short article might help if you have the same problem. If your batteries still won’t charge after trying, you might need to look for other problems/solutions.
P/S: This problem only happened after I’ve done with the conversion of my first version T6 camper. I did consider that the batteries won’t function properly at low temperatures. Still, I also thought the batteries radiate heat when in operation, enough to heat themselves when the weather is cold. So I didn’t put insulation on the walls behind them, instead of designing a proper heating/cooling system. That’s what I need to change for the next version.
Luckily, my 200 Ah batteries come with BMS, but without a self-heating function. You should check the user manuals or with your manufacturer if your batteries have such a function. Consider what I hadn’t thought about when I did my camper conversion to save yourself time from fixing similar problems, especially when you are on a winter trip and need the most from your batteries.
