Need Advice On A Battery Fro My Trolling Motor For My Kayak

[squeak6969]

so i just got myself a little 18lb thrust watersnake for my kayak. setting it up today to take out tomorrow for a bit of a fish. can anyone give me advice on the battery size i willl need? i currently have a 40ah battery that i pulled out of my boat since its not going atm. how long will that give me on the water? should i invest in a bigger one?

thanks in advance for your help

[The Mad Hughesy]

1 hour ago, squeak6969 said:

so i just got myself a little 18lb thrust watersnake for my kayak. setting it up today to take out tomorrow for a bit of a fish. can anyone give me advice on the battery size i willl need? i currently have a 40ah battery that i pulled out of my boat since its not going atm. how long will that give me on the water? should i invest in a bigger one?

thanks in advance for your help

cant speak from experience, but id imagine itd depend on a few things, how hard you run the watersnake, how much charge on the battery etc. im pretty sre you can get a good few hours out of them

[squeak6969]

cheers, might be a trial and error thing i guess. i have it fully charged and im going to use low speed while trolliing so hopefully ill get some good time out of it. probably just gonna use max power fo getting out to where i wanna go...and drop the crab pots in.

[Doyley]

40ah battery = 20ah available until u start to effect the life of the battery.

18lb watersnake uses 15amps per hr flat out.  I reckon you have roughly 2hrs with varying speeds.  U will still have 50% left in the battery to get you out of trouble, but you will start to damage the battery. 

Will also depend on the condition of he battery and if you have it on a good charger to hit it with 14v to give it a full charge. 

[benno573]

tough one...

ideally with something drawing so much of the battery, you would have a decent capacity battery (eg 75ah or better) because as @Doyley pointed out, if you fully (or even more than half) discharge a battery it is really not good for them long term.  Of course the problem here in a yak becomes weight - and cost.  The best solution would be a lithium battery - you get the capacity without the weight and much more tolerant of being heavily discharged that lead acid/AGM etc - but these become very cost prohibitive.

I would be reluctant heading out with only a second-hand 40ah battery.  it is also likely not at full capacity any more unless you have been hitting it with a good quality charger regularly when the boat has not been in use.  Depending on the carrying capacity of your yak, I would look to parallel a second 40aH battery to your current 40aH one, or replace with a higher capacity unit if weight/budget allows. 

I guess the saving grace is that when the battery runs out you have an alternative method of propulsion at hand!