Power for the dingy

A 55 lb thrust electric motor $200,lipro battery $700,
6 horsepower gas motor $1,400 the advantages,disadvantage of each are:
Gas more power/much faster but more expensive, heavier and having to deal with Flammable gas when onboard the sailboat
Electric are lower sound level, cheaper to buy, and easer to handle.
My question is how good are the new lipro batteries has anybody tried them
In a real world setting.

 

It totally depends on how you treat your Lithium Lipo battery and what kind of make you have bought. There are probably some 40 different manufacturers, maybe more. Now you have instead of flammable liquid, lithium on board which, if not properly fused, could be equal as dangerous. For your 700 dollar I could buy Lipo hobbyist batteries, 5 or 6 x 10Ah at 22.6 Volt giving you approx. 1.3 KWh. place it in a water sealed container and I could be for years and years be happy. But I would charge the batteries differently then you. While if you buy a professional Lipo battery, you pay for the name and profit margins and you would probably have 1/2 in power. I have 40 LiFePo4 batteries and am happy for the last 6 years. In those batteries I can hit a nail into it and nothing will happen, but if I short circuit the terminals without a proper fuse, I will also not have a boat anymore. I am a electrical/electronic lover, other people are fond of smelly diesel and gasoline. What voltage are you using 12 Volt? What is the power for your 55lb trust electric motor. For how long do you want to power your boat from the battery? How are you planning to charge your battery/ies? Bert

 

Power to the dingy

Thanks for the response
It would be used for getting off the sail boat
Not sure of the power of the motor just a normal trolling typ
The batteries are the "Smart" brand. the add refers to them as drop in
Short and overload protected treat them like normal batteries
An aside to the benefits is that it would act as a standby if for some reason
The house group went dead

 

It means most likely a 12 Volt system.
Searching the internet, most of the batteries offered with the 55lb trolling motors are 105 Ah battery. i.e. 1,3 Kwh. i.e. estimated up to 6 hours slowly and up to 2 hours at full blast.
We cannot judge without all detailed information like the advert source, but the world is going slowly in the electrical direction. Electric cars, bikes, bicycles, even aero planes. Thus going electrics is a good choice for getting off and on your sailing boat. As long it is good quality, you cannot go wrong. Bert

 

Just to answer your question concerning how good the Lipo batteries are, ask any RC plane/car hobbyist or go onto their website. They are using them worldwide in the 10.000's. It truly depends on quality of the manufacturer. How well they have the casing protected from your use on a boat. But Lithium is lithium and the differences are mainly in the quality cathode used. Some do 500 charging/discharging cycles and some does 5000. Bert

 

,lipro battery $700,

And a std LA batt is about $100 and easier to charge , or replace when the big buck item goes for a walk.

Use a LA and then decide of you actually require the range of the big buck unit.

 

Power to the dingy

Thanks for the response both practical technical
Very cool
It helps

 

It's not really fair to compaired a 55 pounds of thrust trolling motor (about 3/4's a single HP) to a gas outboard that developes 8 times as much power, is it?

I think going LiPo is crazy on a 3/4 HP motor, given the costs. 55 pounds of thrust trolling motors are 12 VDC. An AGM group 31 DC will offer good range, simple charging and a fraction of the price of a LiPo battery. Once you count the weight of a charger, battery and the trolling motor itself, you'll find a 2 HP outboard, with it's included fuel tank easily rivals any perceived weight savings, plus you'll have 2.6 times as much power available.

In the end, you have to ask yourself how much range and speed do you really need, versus cost and weight.

 

746 Wats Per H.p.
1300 * 746 =1.74 H.p.

 

http://www.rapidtables.com/convert/power/watt-to-hp.htm#calculator

 

I'm not sure of your math Jim, where did you get 1,300?

Generally about 1/3 of a pound per amp will get you close enough. This has been discussed many times previously, try:
http://www.boatdesign.net/forums/outboards/how-many-lbs-thrust-equal-1-hp-24964.html

 

PAR, I think he got if from my rough calculation of having 1,3 Kwh (refer #4) All the calculations are totally unimportant. We don't know the size of the boat to get on shore, nor under what conditions he like to get on shore, Gail winds or flat sea. It is all very artificial. Also his assumption not to include a lipo charger. He cannot charge a lipo with a normal charger. Thus the cost goes up. I still think electric for a small boat is not bad. But we have deviate from his question. How do we rate an unknown 700 dollar Lipo battery. My answer is : I don't know. He should just buy a 120 dollar HobbyKing 16000 mAh 22.8 Volt battery and a suitable charger from them. (www.HobbyKing.com ) Place it in a nice water tight box and experiment with electrics.

Nothing wrong with that and he probably will be happy. Bert

 

Sorry I assumed he has a 12 Volt trolling motor, but it may also be a 24 Volt. If it is a 12 Volt, he should buy a 4 cell Lipo battery 16000 mAh battery or a 4 cell other 2 batteries and place them parallel for 100 dollar, included a small charger. Bert

 

I've never seen a 24 VDC - 55 pounds of thrust trolling motor, only 12 VDC, in my limited amount of experence.

 

Nor me, but.....
There are 24 Volt trolling motors on the market , VariMAX 24-Volt Freshwater Hand/Pontoon Mount Trolling Motor per example. It make sense, because if somebody thinks that with a 55lb motor at 12 Volt will do 1,5 hours with a 105Ah leads acid battery, he is getting a big surprise. If he can do 1 hour, he must be lucky. they draw 60 to 70 Ampere and we all know that lead acid batteries reduces drastically its ability. The 20 hour rule applies. However Lithium can do maximum currents, some of them at 12 Volt 200Ampere till the last drop. Taken the weight and the last reason into consideration, Lithium, if one has the money, is the way to go. Just a personal opinion.
Bert