Battery for an outboard

[heynow9991]

Hi
I just bought a Briggs and Stratton Etek outboard on eBay. I don't have it yet but I want to get a head start on how I might power it. I have searched the internet for a manual but can't find anything. All I know is that it is 48v and draws about 80amps at full power. I assume it was originally set up to work with lead acid batteries.
I have 8 x 16000mah 4s lipo rc batteries. I think 3 of those in series would not be high enough voltage as they would output 48-36~ volts.
Any thoughts on putting 4 in series for a high of 60v? I could make a pack that would be 16s2p that would give me 32000mah@60v. The xt90 connectors can handle 90 amps so that shouldn't be a problem. I will be careful to not run it flat out for a long time.
Also any idea how much runtime that pack would give?

Thanks

 

[Voltron]

The answers to a lot of your questions depend on what controller you're going to run it with.

 

[fechter]

Hopefully the outboard has a controller built into it already. You will want to see what the ratings of the controller are.
32000mAh @ 80A would last 24 minutes if nothing melts. If you run it slower, it will go longer. I would not recommend 60V as this might overheat and damage the motor.

 

[heynow9991]

I just bought a Briggs and Stratton 3 hp electric outboard on ebay. It is about 10 years old and has an Etek motor and Sevcon Millipak controller. It is 48v x 3hp = 2223 watts/48v = 46 amps. Lets call it 50 amps. I have several batteries, and I am trying to figure out what would be the best battery to use with it. The first problem I see is that it draws a lot of power so any battery will have to be able to provide it, and it wont last long unless its huge. My other problem is that I know I will only use this on vacation a few times a year so I wont spend thousands on a battery. Im not buying 4 lead acid batteries that will die in 3 years from neglect, and I want a battery that is a lot lighter and more portable.

Battery 1. I have 8 x 6000 mah 4s lipo batteries. I could make a 4s2p pack that would give me 12ah@60v.

Battery 2. I just bought a Luna Cycle 48v Panasonic 11.5ah Bottle Battery. Good for 30 amps. I could get another one and parallel them together. $400, and I could use it on an ebike so I would be able to use it for several different apllications

Battery 3. I have ~160 fairly good Konion batteries from Makita drill packs. 1500mah each. I tried building a few packs but they were not good quality. I feel I have learned enough that I could make a 14s12p pack, that would be maybe 15ah, because the cells are a bit older now and I have abused them a bit. I could also get more cells and make a bigger pack. I have a spot welder, just need a few more supplies like nickel strip..

Thanks for reading all that, I would be happy if for any comments, especially about what voltage I can run with that controller. I dont want to fry it the first outing.

 

[fechter]

A 48v controller is generally rated for a max of 60v. If you go to the Sevcon web site, you can find the datasheet for that particular model.

You should be fine with a 13s or 14s Li-ion if you decide to go that route. Definitely don't do lead-acid, you're right they will die quickly.

50A is asking a lot. Battery specifications are sometimes exaggerated or peak ratings. For a boat motor, it stays pretty constant, so you need a battery with enough capacity so you can get the required amps without overheating the battery.

I have a Li-ion battery I built that's 14s 9p, which works out to about 20Ahr. It can run 40A for pretty long stretches without getting too hot. At 60A, it gets hot in about 10 minutes. Ideally, you'd want about twice this or more, but it gets expensive.

 

[dogman dan]

Buy additional packs, in 2s, to make up a 14s pack. They don't have to be identical, but just similar in rated c rate. Multiple packs if needed in parallel, to get to 16000 mha or close to that. It is possible to rewire one of the extra packs to 2s.

The motor draw should be no problem for that size ah lipo pack. 80 amps would only be 5c draw on them.

Lets call it 30 ah, x 50v that would be about 1500 watt hours. so at a 40 amps draw, 2000w, you'd have .75 hours of run time. 45 minutes more or less.

So that's a bit small, for full speed running on a big lake. You'll want to at least double your pack size when you can afford it. Spring is a good time to buy in the USA, when the stocks are new and fresh, just after Chinese new year.

You will be able to troll at 100 watts draw for a long time though, like 15 hours. Adding a watt meter between the battery and the motor will greatly help you know when to turn for the dock. A weather change though, yer blowing to the other side of the lake. Ocean, you need an emergency gas motor.