48V battery for an electric outboard motor?

[Pompel79]

Hi
Is there anyone who can help me with the choice of battery for an electric outboard motor.
I will be using this kit: http://www.evdrives.com/product_p/ck-0708.htm and are looking for a good battery. I need 30-60 minutes of driving time.
Would it work to use 4 car batteries to get 48V? How long runtime will I get if I use 4 x 100Ah batteries?
Are there any good lipo batteries that are not too expensive that I can use?
Hope someone can help me

 

[NeilP]

12 sereis lipo or LiFePO4 headway or 18650 size cells woudl be way way better than the car batteries. probalby a third of the weight and size.

Look at the Stickies at the top of this Battery tech sub forum and start reading the wiki.

or jsut go and buy a ready buitl 48-50 volt pack form the likes of headway or em3ev.

No way of telling how long it wil run for until you know the current draw of the motor.

A 100 Ah pack in lead acid car battteries woudl be stupidly heavy.

My pack here, at 42 volts and 20 Ah weighs 23 lbs, if that was lead acid it woudl probably weigh 80-100 lbs...total guess, possible more, and the lead acid would also have worse performance than the Lipo.

Need to know how much current your motor draws before any one can even hazard a wild guess as to how long it woudl last.

What you asked is rather like how far can I drvie on one gallon of petrol. Coudl be anything from 140 miles plus to barely a qarter mile dependign ont he fuel comsumption ( current draw)

 

[Pompel79]

Thanks for the answer
Here is the information I find on the engine:
This ME0708 is a Brush-Type, Permanent Magnet DC motor with very high efficiency. Capable of 4.8 KW continuous and 15 KW for 1 minute. For voltages from 12 to 48 VDC input and 100 amps continuous (300 amps for 1 minute).

 

[NeilP]

Ok, so that is what the motor can take maximum.

But very likely that the controller is not giving it any such sort of power. Your controlleer coudl give a maximum of 10 amps or 50 amps, or any figure in between

Ony way to tell for sure is to rig up a temporay pack on the boat along with an inline amp meter, or somethign like a Cycle Analyst, and run it in a fully laden boat for a few minutes at full throttle ans see what the maximum current draw is.

Imagine a car or truck motor.
take two identical motors. they are both capable of putting out a maximum of 100bhp continious or 250 for 5 minutes.
Now fitt one with a standard 'econmy' fuel inhjection system and another with a reved up chipped high spec fuel injection system.
one motor will put out 47 bhp and the other cputs out 250bhp

Same motor different fuel system

Same with your motor and controller. the controller is the fuel system.

go and see if there are any figures on the controller for maximum current

 

[TotalConfusion]

Ok, so that is what the motor can take maximum.

But very likely that the controller is not giving it any such sort of power. Your controlleer coudl give a maximum of 10 amps or 50 amps, or any figure in between

For 24 to 48 Volt System, Series with Permanent Magnet Motor. Controller set to 0-5K throttle unless you request differently.

This package includes:
Motenergy ME0708 Motor, 4.8 KW continuous and 15 KW for 1 minute
Your choice of controllers: Alltrax AXE4844, SPM-48300 at 300 amps or SPM-48400 at 400amps - with fuse
MZJ-200 solenoid to match your controller
3 amp Diode & 220 ohm Pre-charge Resistor
Five throttle options - Magura Twist Grip, Domino Twist Grip, Curtis PB-6, FP-6 or FP-2

 

[bikeelectric]

If you get lead acid batteries you should only use deep cycle type - not car batteries.
The best ones for extended cycling ( drawing them down and recharging ) would be to get 6v golf cart type batteries rated at around 200AH - maybe you could get by with 4 which would give you 24v since it said your motor will run on that. It could be that the higher voltage of 48v will give you more speed but then you would need more batteries.
The golf cart type batteries are probably around $100 each. There are also 12v deep cycle batteries out there that people buy for using on trolling motors rated at around 100AH and those probably cost around $100 each too.

Lithiums are better if you can afford them. Maybe check places that sell lithiums for electric cars so you make sure you get something with BMS and correct charger.

 

[jaunty]

Power a boat with an electric boat sounds like quite the undertaking.


based on the link you provided, that controller is capable of 300 amp... but that would maximum.

Lets just suppose your batteries were providing 100 amps (depending on the size of the boat and thus the load of the motor). In this case a 100 Amp-hour battery theoretically provide 100 amps for an hour. That's theoretical! Now if that were a lead acid battery, you cant cycle that down to zero without ruining the battery. You could probably count on using 60% of that capacity. So in trying to be conservative (you dont want to break down in the ocean). 12V(4)= 48V. But guess what, you dont get to add AH and volts when in series! So at 48V you're stuck with that measly 60 amps for an hour even with 4, 100AH batteries...

Now, if you have $$$$...get some 48V - 100AH LIFEPO4 batteries. probably about 700 bucks each (that would be a good deal). You could cycle those down and get closer to the actual 100AH capability.


But like the other users suggested, try and figure out the actual current draw (load) of that motor and determine how much capacity you will really need.


according to this guy
https://www.youtube.com/watch?v=72yjTyagy2w

He can cruise at 1kW. So at 48V we use P=IV, I=1000/48= 20 amps.

redoing the conservative math...60AH lead acid battery (100 AH rated) would allow you to "cruise" at 20 amps for 3 hours. that's with 4 batteries.

Not bad!

 

[Pompel79]

I have been offered to buy 13 pcs 6v 100Ah battery from an electric car.
SAFT NiCad STM 5-100MRE
http://www.e-m-w.com/manuals/SAFT_Tech_manual.pdf

Will it work well to use 8 pieces of these to get 48v 100AH?
Is it difficult to arrange charging for this battery pack?

 

[wesnewell]

100ah of 20C 12s rc lipo will weigh about 70 lbs. and would be rated for 2000A. Compare that to 100ah of ni-cad.

 

[Punx0r]

However, large-format Nicd can apparently be very long-lived. Although you have to wonder how old they already are. Definitely an interesting battery to be offered - they're not common. Hopefully there will be someone on here who knows about such batteries.

 

[dnmun]

use the 13 as 6S2P and save one as a spare and then use it as a 36V 200Ah pack and you can choose a controller for 36V so you don't have an LVC problem.

 

[wesnewell]

If you can live with a 230lb battery of that size, go for it. However, I would not expect as long a life as you think based on my limited experience with ni-cad batteries.

 

[dnmun]

some of us do have experience with nickel based chemistry and we can instruct you on procedures to recondition the nicad battery to restore capacity.

these packs are high end and have a port to add water and that is the primary failure and life cycle limiter for nicad and nimh batteries so they should provide a life time of service. the water in the KOH electrolyte is consumed over time so having the ability to add water to a nicad cell to restore molarity of the KOH and free up more hydrogen ions essentially extends the life of the pack far into the distant future and if you use them at 200Ah wide you should have more than enuff power to drive the boat at 36V.

 

[Pompel79]

Thanks for your answers
What charger do I need to charge a pack at 36v and 200Ah? Must be easy to connect and easy to use since it will be in a boat.

 

[dnmun]

depends on the power source for charging. will you be using a generator or dockside power at 240V?

charging nicad is different because the end point is hard to detect. i would recommend using coulomb counting in and out to develop knowledge of how much is needed in recharge to restore the battery after discharge. coulombic efficiency will decline with time and usage also.

so plan on using a cycle analyst or some kind of watt meter or ammeter to count coulombs on the way out and then you would turn the meter around and count them back in on the recharge and then learn how much to add during recharge to compensate for changes in coulombic efficiency.

you will have to learn by hands on experience and watching the drop in voltage when it reaches full charge and the charging current goes over to heating the cells. nicad shows a slight negative deltaV at full charge so that is what most generic nicad chargers use. normally the deltaV will appear when the voltage has climbed to about 1.43V/cell. i charge my 120 cell nimh pack to over 176V which is a little above that but i do it at low current so the power is shed as heat for the cells that are over the full charge level. that is how you balance the nimh packs and nicad too i would expect. charge rate has to be less than .1C at this point. i use .05C.

but you will not find a big 36V nicad charger so you will need to develop your own procedure to use these. but once you have it down then you should be able to estimate how much time to use on the timer and then let the charger run under the timer and observe the final pack voltage after charging. do not discharge below .9V/cell or 4.5V for those 5S packs.

 

[Punx0r]

Most RC chargers have a NiCd charging facility, but I'm not sure how many work at 36V.

 

[Pompel79]

I intend to charge the boat dockside with 240v. Can I mount a charger that is always connected to the battery pack so that I only need to connect to 240v to start charging?

 

[Punx0r]

Do you want the system to charge automatically and unsupervised?

 

[dnmun]

yep, that is something you need to do with a pack this large if you decide to go to 36V200Ah.

you could be trickle charging with a 1kW charger in your case. 200Ah is like huge. as in even bigger than almost anyone here.

but for a boat it would be small imo. you have the hydrodynamic resistance to overcome, ... jeremie had a thread on a lot of the calculations and how to design propellers and hull design.

i would expect the biggest hassle would be in getting the batteries initially conditioned so they were able to be balanced and then charging could be monitored to see if you can detect a negative deltaV. i suspect it could be hard to detect and would require some attention, but i think that would just be initially and once you had confidence in the SOC of the pack then after that, using coulomb counters, you should be able to estimate how long to run your charger to recover from the previous discharge.

this is where getting to people who have built batteries using these large nicads would make a lot of difference in formulating a solution.

but you always have to remember that the advice you get online like this is usually just opinions and not fact since most of these people operate on different principals and have no ambivalence about saying anything whether accurate or not.