12v100ah for 55lb Thrust Trolling Motor?

[jplee3]

Hey all,

I recently picked up a 14' Bris boat (similar to Kaboat) and am now researching motors for it. At some point I'm going to throw an outboard gas motor on it but only after we find a home to settle into. Right now we're in an apartment so with the limited space, I think the most I can pull off is a 55lb thrust trolling motor. That said, I realize the *cheapest* way to power this is by getting a 12v100ah SLA battery. The problem is that I don't really want to be carrying around 75lbs worth of battery, as if I won't have enough stuff to be lugging around already. And my left wrist is not in good shape either (some form of tendonitis/RSI). That said, I started researching more and discovered LiFePO4. Expensive but I can probably justify it as a 'backup power source' for the car, house, etc especially if I add some extra ports (USB, DC, and a readout perhaps...)

All this in mind, would you guys suggest this size of battery (12v100ah~)for my needs? Should I size up? I may consider 'future-proofing' as far as capacity need is concerned, so the 200ah~ batteries do come to mind. I'm not sure if I'd really have a need for any higher voltage though. Basically, when I'm on the boat I'd primarily use this for the motor. Maybe I'd use it to emergency-charge my phone, other devices, etc and or *possibly* power a fish finder (but I'd be more inclined just to buy a separate battery to power all that stuff. Outside of the boat, I'd may use this for the car (are these batteries even safe to leave in the car btw? I'm guessing not?) and or around the house as a emergency/backup power system - one really thing that comes to mind as far as use on the road is running one of those Massimo refrigerated coolers of these while camping.
If it makes sense to do so, I may even want to consider adding an AC outlet to the side of the case to power a laptop and possibly other stuff.

Also, what (if any) are the options for recharging this while in the car on a road trip for instance? I'm assuming you can't really charge this, or at least efficiently, from the car cigarette lighter/battery. Do you go solar in that case?

 

[45North]

Bump.
To know what size battery is needed you first need to do an energy audit and itemize all the things you want to power and for how long each day.

 

[Supervstech]

First off, most 100Ah LFP shelf batteries limit output to 100AMPS, so if buying off the shelf, consider that. Most 55# trolling motors draw in the 30 to 55Amp range. So that shouldn’t be an issue, but if adding an inverter for ac loads, keep it in mind.
100Ah should give you 2 hours of constant thrust. But the battery will need a recharge to do anything else after that deep a drain, and cycle life will be impacted if regularly depleted that far down.
200Ah would generously handle the load for 4plus hours of thrust. Figure 13KG / 25lbs per 100Ah as a safe LFP ballpark weight wise.
the battery would be safe in the car, but heat degrades the battery quickly, so best not to leave it in days on end… 160F isn’t good at all for the chemistry.

 

[curt95658]

I use 12v 100ah on my 18' bass boat now. I run a MinKota 45lb and have a separate 12v lead acid battery for the motor, graphs ...etc... Typically it will last all day fishing because the electric motor is just for moving along the bank. If I put it on 10 it uses around 30 amps an hour. I figure if it becomes an issue I'll add an additional battery bank in parallel. If I had to do it over I would buy the cells off Alibaba and make my own.

 

[Opie91]

Where are you using this boat? Lake, river or ocean? Where you use it makes a huge difference.

It is highly unlikely you are going to motor 2 hours at full power. Most new trolling motors have warnings about using them at high power levels for long periods of time anyway. The motor can be damaged.

I calculated a pack built for my dad with the max amps and ended up with a battery that lasts 10 fishing trips on a charge. He has a Minkota Ulterra 80 24 Volt and fishes in 3+ knot currents in a Boston Whaler 17 Montauk. Way overkill and what I am trying to say here is you are likely to use way less power than you think. 100AH is likely to more than enough.