I know I've seen the formula but I can't seem to find it again.

I want to know how long my TM batt. will keep me out on the water. I have a 36lb TM that draws 32 amps at full speed.

My batt. is a deep cycle with 115 amp hr rating. If someone could let me know how to figure this out it would be great.

BR

you can roughly divide the amps into the amp hour capacity of the battery. There are several other factors that play into this so you won't get the total time you get when you divide this. If you tried to run on max for an extended period of time, with a 32 amp load, the amp hour capacity of the battery would reduce by as much as 25 percent. If you just eased around, only pulling 5 - 10 amps, then you would get closer to what the math said. The heavier the load on a battery, the lower the amp hour capacity, that's why a lot of companies us a 20 hour rating, that lets them post big Ah capacity numbers. For the novis, minutes of reserve capacity is actually better when comparing batteries, that is always based on the same load for all manufactors. A 115 Ah 20 hour rating will probably only be a 75 - 80 Ah battery at a 3 hour rating.

So, basically after all I said, if you plan to run on max, the whole time, plan on 2 hours unless you plan on running it down to nothing, then you might get 2 1/2. At a 10 amp load, figure on close to 10 hours.

I guess I should also mention, this is based on a new or very good battery.  As a battery ages, it looses capacity or if it's not properly charged and maintained.

Thanks, I'm not planing on running at full power the whole time I'm out. I will mostly be trolling at low speed.

I was just looking for a round about figure, so I can head back to the car before I kill my batt.

btw the TM is going on a personal pontoon, so at most it will be pushing/pulling 350lbs(and wind)

Thanks again,

BR

I hate to start a new topic with one reply to this one. I guess someone will let me know if I should. ;D

My batt. charger has a float/maintenance mode. After charging should I leave my batt. on the charger in this mode when not in use?

BR

Yes, you can leave it on the float mode indefinitely.

If you are running an outboard as well as the trolling motor you can use the alternator on it to charge the trolling battery as well as its starting battery.  This will extend your running time without increasing battery size.