Circuit breaker
@trigger
On the 1000 you want to keep your primary battery voltage safely above 12v the "TRUE" ISO breaks the connection to the secondary if the primary's voltage is less than 12.7, it WORKS my secondary 55ahr Optima quickly dropped to low in the 10v range when winching someone out of a hole. A winch can draw 300 amps the stator can only put out 46amps at full output. Never be able to keep up, but it can recharge it once the primary hits 12.8 volts.
The 700/500 only have a 32amp output
On the 500 that won't make a difference, BUT the factory battery is not designed to be deep cycled, you drain it deep several times it's gonna die, did that on my 700 TWICE second time I put a yellowtop Optima under the seat which is designed for deep fast discharges like when winching, voltage would drop when winching but it'd quickly get a near full recharge with a half hour of riding.
Lithiums are not designed for deep cycles so while they are smaller and pack more power, can let it go faster, winching is not their designed use, no manufacturer will warranty them.
I have my battery tender hooked to my primary battery whenever it's parked, when it hits 12.8 it starts charging both batteries and they stay right at 13-13.2 v consistently with the motor off. Powersports batteries are such a small capacity a small
parasitic drain can fully discharge one in 4-5 days, causing permanent damage. At $100+ per battery you learn(my first battery on my 700 I killed with the memory drain from a crap radio in a week)
Optima is heavy and takes up room but, for how I use my machine it made sense. I can't put the Honda heater or the storage under there but I needed more juice, I use my winch. I'll get a heater and put it in the cab against the "fire....wall?" Only be a small child in the front middle so it shouldn't be in the way.
Doesn't fit everyone's needs but sometimes having all the info and taking into account your use, wants, needs, then weighting them out allows you to make the most educated decision(or in my case S.W.A.G.) you can.