I would check with the manufacturer first before trying anything. I do not know of any PWM controllers which are able to limit the current in the way a MPPT controller can - but even then, there are limits to what even a MPPT type controller can do. Its similar to what happens if you disconnect a running alternator from a battery - the current flowing "flys back" becoming very high voltage. The fast on-off of the PWM controller causes the voltage of the alternator to spike up to hundreds of volts. I have 400A of Winston LiFePO4 batteries and charge them at 13.9v and float them at 13.2v.ĭo not use a PWM type solar controller with an alternator - it will not work AND it will either damage the alternator or the controller. Remember, you will likely be driving for some time, so even with a lower charge output the batteries should still get fully charged. I would suggest limiting the charger to a maximum of 60% of the alternator capacity, but lower would be better. For this reason there needs to be some current limiting built into the charger, or you will likely run your alternator at 100% capacity and seriously reduce it lifespan. When a LiFePO4 battery bank is at a low state of charge it will take whatever power it can get out of a charge source. I strongly believe that the float voltage should be set to a value below the resting voltage of the LiFePO4 batteries, effectively turning the charger off after the absorption phase. No one has been able to explain to me why this does not happen in the RV LiFePO4 battery charging market. When the battery is full the charger turns off. Take a mobile phone that uses lithium batteries as an example (yes, I know they are are a different chemistry, but the charging logic is the similar). What I will say at this time is that you should not believe everything that you read about the best charging voltage of LiFePO4 batteries.Įvery lithium charger that I have looked at has too high a charging voltage in my opinion and they all still "float" LiFePO4 batteries, which is not ideal. You did not mention what brand of LiFePO4 batteries you are using, so I will not guess and suggest an ideal voltage for your setup. Having a regulator that is programmable will allow you to set an optimal charging voltage for the batteries. With a 24V alternator (which will probably output over 28V) this is not an issue if you plan on charging a nominal 12V battery bank and it should work well. When charging LiFePO4 batteries from an alternator there are two things you need to control.Ī solar regulator requires a voltage differential between the input and output voltages in order to work. I believe that a PWM regulator would be cheaper and would do the job just as well, if not better. I do not think that I would use a MPPT regulator, as the benefits of that technology would be lost when using a constant power source, like an alternator. If I were in your situation I would definitely use a programmable solar regulator.
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