For work I run my laptop off an inverter a lot, which means lots of discharge/recharge cycles which really take a toll on the regular battery. It's been a year and I'm about to replace the stock battery after having it run down so many times (I jump the car maybe 4 times a month when I forget to turn off the inverter).

Can anyone recommend any deep cycle batteries for the Fit, or some other kind of solution that will allow me to power my laptop while the car is off, and then recharge that power source when I'm driving, without affecting the longevity of the power source and/or my car battery.

 

Battery relocation.

Put it in the trunk with a Braille Endurance battery. 1520CA and 155 minute reserve. Weighs 58lbs lol

 

maybe adding a capacitor?

 

AGM « XS Power

I run the D975 as a replacement for my stock battery. It's AGM, so it can be drained and charged 100's of times, and is also about 2x as good as the stock in terms of capacity.

 

A capacitor is like putting a band-aide on a huge wound. For the OP dilemma it won't help.