I often get asked if a car alternator can charge a LiFePO4?
Then I will tell them:
Yes and No
Let me explain.
Yes, you can charge a LiFePO4 battery from a car alternator, but you need a device to regulate the current.
This device is called a DC-to-DC charger.
Now, why do we need a DC-to-DC charger that can limit the current?
Lithium (LiFePO4) batteries have very low internal resistance. An alternator wants to deliver as much current as possible.
With a lead-acid battery, this will be ok because the internal resistance is higher than a lithium battery.
If you charge a lithium battery with a car alternator, the alternator will start to burn out or catch fire.
Victron did a great video about this:
Conclusion
When you want to use an alternator to charge a lithium battery you need a controller in between. This controller is a DC to DC converter.
Curious about what kind of DC-to-DC converter I recommend? Ready my article about the best DC to DC battery chargers.
FAQ
Do you need a special alternator for lithium batteries?
You don’t need a special converter to charge a lithium battery. The only component you need is a DC-to-DC charger.
Can I charge a lithium battery with a car charger?
Yes, this is the standard charger for lead-acid batteries. But you need a DC-to-DC charger in between the alternator and the battery to regulate the charging current.
Do you need an isolated or non-isolated charger?
I have written a comparison between these two. Read the article here.
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I’m an off-grid enthusiast. I created this website to give clear and straight-to-the-point advice about solar power. I’m also the author of the book ‘Off-grid solar power simplified‘. Read more about me on my about page, check out my Youtube channel, or send me a message.
THANK YOU for explaining that extremly well!
I “guess” that explains why LiFPO4 batteries have a batterie-management-system