This item is brand new. It's been sitting and collecting dust. It's been installed for a mock up but never powered up other than to test to make sure it works.
Retail is $399+

The Stealth 1 Charging 36V Marine Battery Charger is a waterproof battery charger designed for “charge on the run” which means it charges while your outboard is running. It works like a typical battery charger. However it gets it’s input energy from the 12V system in the boat instead of a 110VAC wall outlet.
 
It converts this 12V energy into 36V energy and properly charges 36V batteries.  This system weighs 4.5 lbs and the system permanently mounts in the boat between the 12V and 36V battery(ies) and connects to each. The 12V ground and 36V ground are tied together for a common ground. The 12V positive terminal provides input to the Stealth 1 Charging Marine Battery Charger and the output from the Stealth 1 Charging Marine Battery Charger goes to the 36V positive terminal.
 
This unit is completely automatic in operation.  Anytime the outboard is running OR anytime a 12V charger is connected to the 12V side of the  boat, this unit is simultaneously charging the 36V battery(ies). Don’t worry, it prioritizes the 12V battery and insures it is at 80% State of  Charge before it starts charging the 36V battery(ies) so you’re always  good to go.
 
What is the advantage? A lot! This system allows the outboard’s charging system to recharge the 12V battery AND the 36V battery(ies) at the same time. Every time the outboard starts and runs both the starting and trolling battery(ies) are recharging. Go further with less  battery weight by generating charging power on the run! Never run out of trolling power again. Simply start your outboard and you’re recharging!
 
Depending the balance of outboard run time vs. trolling time, you may  not have to plug your boat in at all. It’s common for in-shore saltwater anglers to go for months between battery charges with this  system. Freshwater anglers typically still plug in the boat at night because they typically run the outboard less. When you are back to the  cabin at night, plug in the 12V on-board charger and this Stealth 1 Charging 36VDC  Marine Battery Charger automatically tops off you trolling battery(ies) before morning.