Suggested battery for a 46lbs outboard?

[LorenzoC]

Hi all, I need some help with an electric outboard motor that I bought used for my tender.
The specs says that has 46lbs of power, but I don't understand and I can't find a suggested battery capacity to match. 50Ah? 65Ah? I hope not 80/90Ah, it wiill be difficult to manage, because of the weight.
The aim is to go from the buoy's moored boat to land and back.
Any suggestion that isn't to sell the motor and buy a petrol one?

 

[Tranona]

46lbs is the thrust the motor will produce. It is not directly related to the capacity of the battery. The drawback of using this type of motor for a dinghy is the range in terms of time running and lead acid batteries do not have the energy density to run for long periods. Usually these motors are powered by the mother ship batteries - they are designed for low speed work on high powered boats but in a dinghy you need a dedicated battery. A 65Ah is a reasonable compromise for short runs to and from a mooring but you will need to take home and recharge after every use. The run time you get will depend on the power you use so running flat out with a loaded dinghy against the tide will flatten the battery quickly. lead acid batteries are best kept in an SOC above 50% for a reasonable life and a Lithium is worth consideration if you use the motor a lot because you can use more of its theoretical capacity and it is quicker to charge.

No such thing as a free lunch and if you want real usable performance in terms of power and range with electric power you need a "proper" lithium powered motor like a Torqeedo or e propulsion. However the "cheap" alternative is suitable if you make low demands on it.

 

[LorenzoC]

46lbs is the thrust the motor will produce. It is not directly related to the capacity of the battery. The drawback of using this type of motor for a dinghy is the range in terms of time running and lead acid batteries do not have the energy density to run for long periods. Usually these motors are powered by the mother ship batteries - they are designed for low speed work on high powered boats but in a dinghy you need a dedicated battery. A 65Ah is a reasonable compromise for short runs to and from a mooring but you will need to take home and recharge after every use. The run time you get will depend on the power you use so running flat out with a loaded dinghy against the tide will flatten the battery quickly. lead acid batteries are best kept in an SOC above 50% for a reasonable life and a Lithium is worth consideration if you use the motor a lot because you can use more of its theoretical capacity and it is quicker to charge.

No such thing as a free lunch and if you want real usable performance in terms of power and range with electric power you need a "proper" lithium powered motor like a Torqeedo or e propulsion. However the "cheap" alternative is suitable if you make low demands on it.

I'll buy a 65Ah and I'll take the rows with me
Next week we'll go in Croatia for a couple of weeks, I'll write here how will go

 

[neil_s]

My neighbour on the dinghy trots keeps his battery in one of the dinghy air tanks with a solar panel to charge it.

 

[LorenzoC]

My neighbour on the dinghy trots keeps his battery in one of the dinghy air tanks with a solar panel to charge it.

My dinghy is 2,3 meters, too small to have a tank

 

[sailoppopotamus]

I have a "Force" 46 lbs outboard that I use to get to shore. My 25ah Victron deep cycle is more than enough. My demands are low, just a trip of a few hundred meters and back, 2-4 times a day. I usually charge it in the morning using a charger I run off the inverter. For my limited use I haven't felt the need for a larger battery, the 25ah is easy to grab with one hand and move from the boat to the dinghy and vice versa.

 

[Kelpie]

Just to give you a point of reference, my Bison 68lb motor draws about 55A at full throttle. I use a 60Ah lithium battery for it so in theory have an hour of range.

I would guess your 46lb motor would draw much less, under 40A.

What kind of distance/time would you be looking at?

 

[Mister E]

I plug a 55ah leisure battery in to the boat main batteries when not in use on the dinghy.
It is in a battery box with a rope handle around the box.
I simply use Anderson plus on the motor and the boat.
I have wheels on the inflatable dinghy so don't have to carry them.
I also found that I don't need to charge very often when using it to get to the boat, about 500 yards. Certainly not every time I used it say once in 20 trips maybe more.

Faster than trying to row the inflatable and silent.

 

[LorenzoC]

Thank you all for the suggestion.
Next Sunday we'll leave for the Croatia with my used 60Ah and I'll try it taking aboard the rows
I hope the price of a lithium battery will drop, so I could use a lighter 40Ah

 

[Kelpie]

Thank you all for the suggestion.
Next Sunday we'll leave for the Croatia with my used 60Ah and I'll try it taking aboard the rows
I hope the price of a lithium battery will drop, so I could use a lighter 40Ah

If using a lithium battery, check the maximum continuous discharge current. Usually they can only manage 1C, so a 40Ah battery can do 40A. Which means that you need to buy an hour's range whether you need it or not.