Battery chargers should not drain back. The diodes / diode bridge that convert the AC to DC for the battery should prevent it. Lead acid batteries should be kept on a maintainer when not in use foran extended time because of their self discharge and sulfation problems when sitting at less than full charge. Most new battery chargers have a maintainer function once the battery is fully charged but they should not be left connecte4d and plugged in as they could possibly end up overcharging the battery .. LiFePO4 batteries are much different then Lead/acid ones.They can be discharged to their cut off voltage and left sit without damage.. a O4 100Ah LiFePO4 battery can be drawn down the full 100 Ah without hurting it ... A Lead/ acid battery can only be drawn down about half way before hurting it and must be fully recharged as soon as possible to avoid the sulfation problem. In other words, a 100Ah LiFePO4 battery can deliver the full 100 Ah without harm while a lead/acid battery rated 100 Ah can only deliver 50 Ah's before beginning to damage it. There's a world of differences between the 2 technologies.. Lead /acid shines in high draw applications like starting batteries and operating/ charging in sub freezing use.. LiFePO4 batteries shine in low draw over longer times as "house" batteries in RV's and off grid applications. LiFePO4 batteries are almost 1/2 the weight of a similarly rated Lead/acid battery too.

I used a dc to dc converter designed to be used in a truck / SUV to make a charger that can be plugged into an accessory socket in a vehicle , or as the MPPT charge controller to charge from solar panels. I also have wall chargers designed specifically to charge LiFePO4 batteries. I can charge my home built Power Station ( box) either from home with the wall charger, from vehicle via accessory socket or from solar panels. Most Power Stations can be charged the same way.. The big advantage of my homemade one is I have 12v DC output from it up to 100 A max draw to run things like an electric outboard motor. I have not seen a commercial Power Station with more than 10 t0 15A output via accessory socket.`` I used a battery box with the USB outlets, accessory socket and battery volt meter built in to build my Power Station.. Those boxes are originally designed for marine use to power The motor starting battery and accessories like depth sounders and electric trolling motors.. I have also built a power Station ( box) using a plain plastic marine battery box housing a 100Ah LiFePO4 battery.. I put two Accessory sockets on it and wired on both a 120A and 50 A Anderson plugs. I also put the DC to DC converter on it so I could charge it from an accessory socket or solar panels. USB out for it is by an accessory socket USB adapter. There is no volt meter on it and there is no 120v inverter attached to it like the commercial box I used to build the one in the picture.. Box was just a plain plastic marine battery box I added the outlets to.

The sprag is like a one way bearing.. The rollers in it are nor round ,, Spun in one direction the stay laid down and the assembly spins freely.. Change the rotation and the rollers cam against the race and lock up the assembly.. When starting the rollers cam to lock the assembly and start the engine.. When the engine starts the assembly rotates faster than the starter drives it so the rollers release. The starter and assembly are then effectively disconnected .. It works much more simply than it is easy to explain. When you install a new sprag be sure to install iit in the right direction. If it is backwards the starter will not engage to start the engine. It is an easily done mistake.