Hi,
Can you connect a battery (eg 24v lead acid ) or other power source (eg alternator) to the input of a MPPT charge controller rather than solar panels?
No.
The reasons are several, but the short version is that the controller can short the PV input for various reasons. PV panels are fine when that happens. A battery or other source is not.
The exception to this is IF you control the Maximum current of the MPPT, and set it to a value below the unit maximum, and also include a smaller fuse in series (less that than 50% of the unit’s rated maximum input current). This should stop the unit doing power sweeps that raise the units input current above the max permitted value.
Alternators Must have either a lead battery as a load OR a smart regulator, the potential stored energy in a spinning alternator is very high. However, a current controlled ‘MPPT’ unit can be used to step down the voltage from the Alternator / battery combination under limited circumstances.
Many thanks. Will try today and see how we get on
Just be aware that you’re in wholly unsupported territory there, and any damage to the controller caused by unsupported usage such as this won’t be covered by warranty - personally, I strongly suggest instead using the proper component for the use-case, such as a DC-DC charger.