Can I Charge My Lithium Battery With an Alternator?

Unlike a lead-acid battery the internal resistance and corresponding voltage of a lithium battery does not rise until it is nearly 95% fully charged. This can cause alternators to run longer at full output which can cause alternator burnout. The length of a time a lithium battery can draw a constant current at or above the alternators max output can exceed the design parameters of the alternator. This can cause the alternator to over heat and burn-out. Alternators are internally cooled by a fan on its rotor. Lithium batteries will draw a high charge current at all times meaning alternators are prone to burn-out at low RPM when charging lithium batteries at high currents.

If you have a large alternator that can easily output more than the load the lithium battery(s) will request it may not be subject to burnout. Depending upon your lithium battery bank capacity, this may require a heavy duty alternator capable of running at a high output across various RPM all day and possibly for many days. If you have a large alternator that can easily output the draw a lithium battery will put on it, it must still be temperature compensated throughout its RPM range to avoid overheating and burnout. Even a heavy duty alternator may need current limiting as well temperature compensation to avoid premature failure.

For any other alternator it would be wise to consider some kind of current limiting to prevent it from self destructing when charging Lithium Batteries at high output for an extended time. Current limiting devices such as a DC-DC charger will limit the charge current that is supplied to your house batteries and will avoid overloading the alternator. These days most DC-DC chargers are now Lithium compatible. Checkout out our range of DC-DC chargers here! 

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