Most cost effective 12v highest a/h lithium battery setup.

[awol]

Chuck that 3 amp power supply and make one out of an old PC supply:

Cut off the connectors;
Join all the yellows for the 12v;
Join all the blacks except one for 0v;
Join the orange to a grey;
Join the green to the remaining black. You can make this the on/off switch;

That's it - a 300w power supply that can give 10 amps. Cost: £1 from a car boot sale or zero if you have an old PC.

It's very satisfying when you recycle something like that too. You get a real sense of achievement.

If you want to be really clever, you can use the reds for a 5v supply/charger, and the oranges for 3.3v

Genius tip !!
I'm going to have to give it a go.

 

[eHomer]

Genius tip !!
I'm going to have to give it a go.

It was indeed. I should have followed Dave's advice sooner.

Even my "spare" used PC PSUs were quite powerful and efficient switched mode. 22 amps at 12v with built in fans etc..

I've now tidied up the connections with single runs of pos and neg using 12 awg silicon wire. The Hobbyking Turnigy charger sits neatly on top, as though it was made for it.

I tested the outboard in the tank at full throttle and it ran for 1 hour 55 minutes to run down from full charge to 3.6v per cell.

Now that the "Chk time" parameter has been increased from 10 to 60 minutes, it's stopped cancelling with the error message. It did stop after 300 minutes though, another parameter, which I've now turned off. (it had put 16 amps in to the pack by then though).

The charger is now set to parallel charge my six pack of 4s 5amp batteries, but if I ever charge anything smaller, I'll switch the chk time back to 10 mins, and the max charge back to 300 mins.

By the way Dave, this is what the back of the Hobbyking parallel board looks like. The main power tracks look quite meaty, and easy to reinforce if necessary.

My waterproof lunch box has turned out quite neat now, I added a 4s extension lead to the balance lead breakout connector to reach the charger easily, and then plug the lipo alarm in when the battery is in use. The cover is then clipped on, making the box watertight, but the leds show through, as do the fuse leds, and the beeper sounds quite loudly through the box. I think I'll keep the individual pack fuses at 30 amps, they should give some protection against a melt down, and they won't blow unless really necessary, and they'll add the least shunt resistance, ( I think ).

I'll tie it in the canoe too, via the hand strap, and it even floats, displacing 4.5 litres of air. I'll give it another run test tomorrow, on normal speed, and I expect it will last for 4 hours or so.

I'm very pleased with the result now, thanks for all the guidance and patience with the numerous questions.

 

[Deleted member 4366]

Excellent result. Those tracks look OK. If you have a spare minute or so, you could drizzle some solder on just to make sure.

Which motor is that?

 

[eHomer]

Its an SBM18, most commonly branded as Sevylor.

They're very small and light, even by Minn Kota standards.

They're ideal for small canoes because they only weigh two or three kilos.

I've modified that one a bit though, fitting a twin clamp Minn Kota bracket in place of the flimsy single clamp.

Funny thing though, when I googled the name, a US boating forum popped up where someone was asking about lithium batteries for them !

http://forums.iboats.com/forum/general-boating-outdoors-activities/inflatables-and-ribs/542730-lithium-battery-for-sevylor-sbm-18-electric-motor

http://www.google.com/webhp?client=tablet-unknown&source=android-home#q=sbm18 motor

 

[Geebee]

Its an SBM18, most commonly branded as Sevylor.

They're very small and light, even by Minn Kota standards.

They're ideal for small canoes because they only weigh two or three kilos.

I've modified that one a bit though, fitting a twin clamp Minn Kota bracket in place of the flimsy single clamp.

Funny thing though, when I googled the name, a US boating forum popped up where someone was asking about lithium batteries for them !

http://forums.iboats.com/forum/general-boating-outdoors-activities/inflatables-and-ribs/542730-lithium-battery-for-sevylor-sbm-18-electric-motor

http://www.google.com/webhp?client=tablet-unknown&source=android-home#q=sbm18 motor

I had one on a canoe years ago, I put an extra cell on mine from 12 to 14v and it made a lot of difference to top speed and never caused a problem.

 

[eHomer]

You and Dave have suggested upping the voltage from 12v, and it certainly seems to give the motor lot's more oomph on the 4S at 15 to 16v.

My tank testing has been dual purpose really, to check the run time with the 30 amps and also see if the motor's ok with the slightly higher voltage.

It stood the two hours at full throttle ok, and of course there's no warming with the motor immersed in a tank of water, (the ultimate in cooling !)

It is a very good combination for my small canoe, weighing just under 4 kilos, it's half the weight of my previous two 14 amp sla batteries, with more volts and twice the current capacity.

 

[drsolly]

I see the big + and - bolts. Is there any possibility that a metal object could touch both of those at the same time? Because that would be very bad.

 

[eHomer]

It certainly would be with most batteries !

I incorporated fuses in the pack though, just in case.

There's a 30 amp for each pack and a 30 ampf for the combined load as well.

The bolts make it very convenient to just use the ROC clips on the outboard motor.