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Do I need a second battery for a electric motor


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Hey

 

Ok so on my 4.3m tinny, I have one battery stored at stern that powers the nav lights, sounder and bilge pump. My 40hp 2 stroke yammy outboard is a pull start so it doesn't require any power to start. There's an alternator that charges the battery.

 

I'm getting a electric motor on the bow and am torn about where to put the secondary battery. My question is - given my outboard doesn't need power to start, can I get away with using a single battery to charge the motor + all the above mentioned electronics? Not sure what my current battery is, it's a few years old now so I'd be happy to replace it with something with lots of juice.

 

Cheers,

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I would suggest you purchase a deep cycle battery of between 95-135 amp hour to run the electric, if you have a weight issue you could reduce the size of your current battery to a 20 amp hour which are tiny in comparison but would still give plenty of power to run the low amperage items.

It's pretty important you run deep cycle for the electric.

Frank

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What frankS said and best to locate your electric motor battery somewhere up the front close to the motor.

I don't understand electrics too well, but believe if your cables are too long you need to beef them up. I'm sure someone with a better understanding will chime in in this regard.

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So it wouldnt be very often you use the leccy motor and your lights unless you do after hours plastics sessions.

Normal batteries are fine and will run the leccy, however, they are not completely designed to be discharged and charged over and over and over.  The result will be a dead battery quicker.

100% for the deep cycle to run your electric motor only......I would never use anything other than a minimum 100ah for an electric motor.  A decent battery charger to keep it charged and maintained also.  I use a Ctek. 

Perhaps a smaller "normal" battery for your other electronics/electrics charging off your running pull start outboard.  My Ctek also charges and maintains my standard battery.

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6 hours ago, ryannnnnnn said:

Hey

 

Ok so on my 4.3m tinny, I have one battery stored at stern that powers the nav lights, sounder and bilge pump. My 40hp 2 stroke yammy outboard is a pull start so it doesn't require any power to start. There's an alternator that charges the battery.

 

I'm getting a electric motor on the bow and am torn about where to put the secondary battery. My question is - given my outboard doesn't need power to start, can I get away with using a single battery to charge the motor + all the above mentioned electronics? Not sure what my current battery is, it's a few years old now so I'd be happy to replace it with something with lots of juice.

 

Cheers,

If I was in your situation I would get one large deep cycle battery to power everything rather than muck around with 2 separate batteries. 

Im guessing your electric motor would be not bigger than 54lb. I would get a deep cycle battery 140ah minimum. Bigger is even better. 

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I reckon you’ll be able to get away with one good 100 amp hour battery. I have a 54lbs thrust leccy on same size boat and keep it charged with a multi staged charger. Used the leccy all day and not depleted more than 25% of charge.

if it doesn’t work you can always wire in a second running battery later on.

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You need to know your total draw of all the things being used to calculate not only the amount of amp hour battery you would need as well as the discharge rate.

There are calculators that can help you find the answer to this but you need to find out how many watts/amps the different items use-

https://www.centurybatteries.com.au/products/deep-cycle/deep-cycle-power-calculator

 

Personally I would be leaving the existing set up alone if it works, put the 2nd battery(AGM) in the bow.

 

There are other options like you suggest by putting the single battery to replace the other but the bigger the amp/h needed the bigger & heavier they are, you could also run the existing & the 2nd together with an isolator & use them separately or together.

If you have a look via the search tab you can see what others have done, like these threads.

 

 

 

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Once you start to use your electric motor you will get addicted to it and a normal battery will not cut it and may leave you stranded.

Keep your battery as close to the electric as possible to also save amps.  

Do yourself a favour and invest in a deep cycle 100 amp or better and only use it for the electric that way you have a solid back up if your main battery goes down.

With me if you are going to set up a boat with the bells and whistles do not skimp the pennies on the important items. 

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