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1) The use of a portable Alternating Current gasoline generator will have its own separate receptacles for plugging in an AC battery charger if you are looking for a solution to charge the batteries. An Inverter inverts a DC output and converts it to AC, thus no need for an Inverter since any portable gasoline generator will have built-in receptacles. To power a DC load such as the 24VDC motor on the winch, a rectifier converts Alternating Current to Direct Current. An Inverter does just the opposite, as it converts Direct Current to Alternating Current. I am aware of some portable AC generators that can provide a 12 VDC output as well as the traditional AC outputs, but I am not aware of any that provide a 24 VDC output.
2) Automobile batteries are rated in CCA (Cold Cranking Amps). CCA's are required to provide a high amount of current for a short period of time in order to start an automobile engine. For example a starter on an automobile requires a high amount current to turn an engine over. Most automobiles use 12 VDC batteries that are rated a minimum of 500 CCA's and usually well into the 700 or 800 CCA levels. A 125 CCA battery is too small and will discharge quickly.
3) You can easily connect (2) two 12 VDC batteries in series with each other to provide the 24 VDC output. 24 VDC batteries are not commonly sold in automotive stores. Connect the positive from battery "A" to the negative of Battery "B". You will then end up with a negative on Battery "A" and a positive on Battery "B" to connect to the winch 24 VDC winch.
Yes, you are correct if additional amps are required, then the (2) two 12 VDC batteries that were wired in series (string) can be connected in parallel with (2) two other 12 VDC batteries wired in series. If all 4 batteries are the same amps, then you will double the amp output due to connecting 2 series strings in parallel. Connecting batteries in this fashion is called a battery bank.
4) Yes, you will either need a separate AC portable charger to charge 12 VDC and a separate switch to isolate the (2) two 12 VDC batteries from one another or you can leave the 2 batteries in series and purchase a 24 VDC battery charger. I would also suggest installing 12 VDC voltmeters or a 24 VDC voltmeter for monitoring purposes. Run time will be determined as to how much charge the batteries have. Once a 12 VDC battery goes below 12 VDC, it needs to be re-charged. A fully charged 12 VDC battery is approximately 13.5 to almost 14 VDC. Since these batteries provide high current outputs, there is no way to determine the actual run time due to them being rated in CCA's.
The only batteries that can be calculated in an approximated run time are true deep cycle batteries and these are rated in amp-hours and not CCA's. A typical deep cycle battery application provides shorter amounts of current over a longer time period and are meant to be re-charged. However, a Deep Cycle battery can also provide a high amount of current but a much shorter run time. Deep Cycle batteries are pretty much opposite than a automobile battery. However, they are very costly. For example a 12 VDC Deep Cycle battery that is commonly used in solar panel installations and rated @ 198 amp-hours costs around $500 per battery. The higher the amp-hour rating in a Deep Cycle battery, the higher the cost.
5) Since the 24 VDC Winch is an electric motor, it is possible that the 250 amp load is the Full Load Current (FLA) or the in-rush current when the winch is initially turned ON. That is a huge current draw. More than likely, once the winch is running, the current draw will be smaller than 250 amps. It is possible that the winch has a nameplate rating that will provide the FLA and running current spec's. If no nameplate, I would ask the winch manufacturer if they can provide these to you.
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