In our other article “How to make LiFePo4 12V Lithium Battery” we explained how to make your own powerful LiFePo4 battery for cheap using our Chinese friends at AliExpress. Of course, we need to charge this battery as well. We are EagleTastic so we like to do it right, without paying too much. That’s why this article is born. To teach everybody how to charge your LiFePo4 battery for cheap!
Assuming that this LiFePo4 battery will be used in a camper, RV or boat just like me there are roughly three options to charge your battery.
- Charge your LiFePo4 battery using solar power
- Charge your LiFePo4 battery using your existing dynamo from your car or boat (or other vehicles)
- Charge your LiFePo4 battery using mains power (230V or 110V)
Charging LiFePo4 batteries in colder areas
Before continuing, make note that the cells take irreversible damage if you charge them below 0°C (freezing point). In some cases the bms protect the cells and prevent the charging from happening. When you have the same bms as in our build here this is not the case. You have to manually check that the cells are not below freezing point. LiFePo4 batteries like to be stored without charging them. So I didn’t do anything to solve this. I manually switch the panels off when it’s cold and don’t use the van and batteries anyway. I also have LiFePo4 batteries on my motorcycle that sometimes charge below freezing point. I just accept that my battery takes some damage. I still haven’t noticed any big changes after two winters.
If you are in a situation where the batteries are often in a place below 0°C and they need to charge whilst at this temperature you have two options: reconsider using LiFePo4 as your desired battery. I’d go for a regular lead-acid battery or the more expensive Lithium Titanate batteries. Or you can keep your batteries warm using electrical heating (like this) in combination with a temperature switch (buy here). Although this solution requires electricity, so make sure what solution is best for your needs. It differs per situation!
Charge LiFePo4 Battery using Solar Power
I’m personally a huge fan of solar power. Mount it once and have free electricity for many years! For this solution you need:
Solar panels generate electricity from the power of the sun. How many watts depends on your power usage, how much sun there is where you live. And how big the batteries are. In most cases, it’s best to have as much as you can fit on your roof. So you have enough capacity. Even in winter times when days are shorter or other dark rainy days.
Solar panel mounting brackets. There are more ways to mount them. But this is convenient.
MPPT charge controller to convert the electricity from the solar panels into usable electricity for your battery. There are also cheaper devices available, but those are probably fake MPPT controllers. They convert the electricity inefficient so you get less power from the same panels.
Furthermore, you need some copper wires to connect everything (make sure it’s thick enough or even use 2×62 as recommended for the MPPT). You’ll need pliers to make all these connections just like where we made the battery. Also some fuses to keep it safe are recommended by the MPPT charge controller (I only put a fuse between my solar panels and MPPT). For the mounting part you probably need screws and caulk glue and more tools. Since the mounting installation can be different in every situation I keep it global and just tell you how to wire and install this setup.
Installing the MPPT controller
Always connect your battery first and your panels after. When Dissembling do it exactly reverse, so first panels and lastly the battery. Otherwise, you might damage the controller. The wiring itself is pretty straightforward
- BT- = negative wire(s) from the battery
- BT+ = positive wire(s) from the battery
- PV- = negative wire(s) from your panels
- PV+ = positive wire(s) from your panels
- OV- & OV+ = for your loads. I’d recommend to not use this since the load is limited. Grab loads directly from your battery.
Because we need to program this MPPT to work with LiFePo4 batteries we only connect the battery. (these are thin wires only used to program this machine. Use thicker wire for your actual setup)
Connect the wires to your battery. Don’t mess up the positive and negative wires
When you connected the wires properly your MPPT controller should give a sign of life. Now to program it press “PRG” and you see “d00”. This is the setting for the load output which we don’t use. So use the arrows to navigate to “d01”
d01 is the output voltage for float charging. LiFePo4 batteries have low discharge rates so they actually don’t need float charging. Hold “enter” until it start blinking and use the arrows to change this to anything below 13,6V. This is to avoid damage on your LiFePo4 battery. I went for 13,5V. Press “enter” to confirm.
d02 is the maximum charge voltage for your batteries. Again, hold “enter” till it blinks and use the arrows to change this to 14,6V. Press “enter” again to confirm
d03 is the lowest the battery may go. This is already 10V and can stay this way. There’s also a “d04”. That should say 01 now since 00 is the standard settings and we just change that. To confirm everything went correct. Disconnect the MPPT from the batteries and connect them again. Check if the settings are still like we just programmed. If they are: You have successfully programmed this MPPT charge controller and you’re ready to hook up those solar panels!
How to charge your LiFePo4 Battery using your vehicle’s Dynamo
When charging from the vehicle’s dynamo there’s only one small problem that might occur, especially with modern dynamo’s. And that is that there will flow too many amps into the battery and your dynamo can’t keep up. Resulting in overheating your dynamo. If you have an older vehicle with a simple dynamo: just hook it up and you’re good to go.
When you’re unsure, or have a modern dynamo you need a DC to DC charger to regulate the max amps drawn to this battery. Choose the 14,5V version for LiFePo4 batteries. Installing this is easy. It has input and outputs. The inputs are your wires that are usually connected to the standard battery, the outputs are for your LiFePo4 battery.
Charging it from the dynamo next to your regular battery
When you want to charge your LiFePo4 battery alongside your normal battery in your car you want to have the two batteries wired parallel. Meaning you connect the + with + and – with-. Although you only want this to happen when you are driving. Otherwise, the LiFePo4 battery would endlessly try to charge your regular battery resulting in an empty LiFePo4 battery. There are several ways to do this, one more expensive than the other. The easiest and cheapest way I achieve this is with this switch
You can choose to direct your current to battery 1, battery 2, none (don’t do this), or both. This is also how I manage my solar power to my regular batteries every once in a while. Connect the negatives from the batteries directly. Send the plus wires through this switch.
How to Charge your Battery using Mains Power
Charging your battery through mains power is easy. Just buy a charger for LiFePo4 battery’s and you’re good to go. Of course, you’ll want enough amps or you’ll be waiting for days until it’s full. I only found one charger in a normal price range. It loads with 20A. It could’ve been more but that was way more expensive. So I went for this option.