Battery Questions

Matt_Colie wrote:
OK Juju,

We have some problems here.
- The motor (Minn Kota® Endura C2-30) is specified to draw 30Amps, but no rate down for less than full speed is given.
- If you run at full rate from a 40AH battery, you won't get an hour plus. You will be lucky to get 3/4 before it studders to a halt, and an even an half an hour at flank will probably be damaging to the battery.
=> They get nasty when you ask them for more than 50% of their C/20 rate.
=> Then there is the Peukert exponent that says if you pull power out at greater than C/20, you won't get all of it.
- Only a true sealed battery should be put in such service. An AGM or GelCel will not dissolve your pants when things go wrong. Any battery with removable caps has that potential. (But, you may be so good you never flip a kayak - Right!)

I did a lot of fancy electrics on performance cruisers before the depression shut me down. I can tell you have an interesting plan, but I think you may have to wait for LiPo to get affordable.

Matt

I sent an email to Minn Kota and this was their response.

SPEED AMP DRAW THRUST
1 - 8 AMPS 4 POUNDS OF THRUST
2 - 10 AMPS 6 POUNDS OF THRUST
3 - 14 AMPS 10 POUNDS OF THRUST
4 - 20 AMPS 15 POUNDS OF THRUST
5 - 30 AMPS 30 POUNDS OF THRUST
To figure how long a battery will last you will use the following formula:
Battery amp hours X .85% divided by motor amp draw = approx. running time.

If I understand correctly, on speeds 1 and 2 I could expect 3 hours maximum. This would work ok for me as at least half the time we are in shallow water with a lot of current and paddleing is not bad. I just need some help in the calm water when I have to paddle for a half mile or more.

Problem is I am adding 50 lbs of weight with the battery and motor so that will just slow me down more. I have lost about 20 lbs since last kayak season so I guess I could lose a little more and even it out.