Electric Power
Above is the link for my notes on putting a Torqeedo Cruise 4R, 48V electric outboard on Mischief.
Below are notes in reference to powering a C-22 with an electric engine.
Upon acquiring Sweet Pea, she was powered with a Torqeedo 4R, rated at 10 HP. The electric outboard is supplied by 4 deep cycle marine batteries in series to make up a 48V battery bank.
On an early test run, the following data was collected. Note that this data is very approximate, due to wind and significant boat wake on the lake that day.
Power Speed
160w 2mph
500w 3.3mph
800w 4.0mph
1000w 4.5mph
1500w 5.3mph
2000w 5.8mph
3000w 6.5mph
More motor data - Windy conditions for Lake Travis in the summer, but this was a Tues. evening, so at least the boat traffic was much less.
Torqeedo, 48V:
550W 3.4mph Driving into strong wind, small whitecaps forming
1000w 4.4mph
1500w 5.1mph
2000w 5.8mph
3300w 6.3mph (max throttle), wind milder, about 10mph?
500w 4.1mph downwind
3300w 6.6mph downwind, about 10mph wind
Minn Kota Traxxis 80, 24V, wind 10-12mph (wild estimate)
100% 3.2-3.4mph into wind
75% 3.0mph
50% 1.6mph
75% 2.5mph into ~15mph wind
100% 2.7mph into ~15mph wind
75% 3.5mph downwind at 10-15mph
100% 3.8mph downwind at 10mph
The 80# thrus Minn-Kota can definitely push the boat, and allow manuevering in the marina. But max speed tops out too low to be useful for getting anywhere very fast. I also noticed that the control head got very warm after 30-45 min. of constant driving at high power.
The Torqeedo 4R has PLENTY of power. But four batteries for a single bank seems to be an awful lot of weight! (and maint, and expense for anything that would be a sealed battery...).
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March 8, 2014 -
As an experiment, Ray and I (Ray just bought Night Breeze) mounted the Minn Kota Traxxis 80, 24V motor on the Catalina 30.
We tested on a cloudy day - no wind (at the time), and no waves.
The Traxxis 80 was able to back the boat out of the slip (again, no wind), and push the boat out of the marina, around, and back in.
Ray's cell phone reported top speed of about 2mph. Not very fast, and probably wouldn't run terribly long - but it does serve as a cost effective backup if the gas engine died and you needed to get back into the slip.
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The Torqeedo 2T finally arrived!!!
It took far too long to get the Torqeedo 4R moved back to the other boat, and both Torqeedo's wired up respectively. However, I finally had at least a few moments to test out the Torqeedo 2T on the Catalina 22:
Water was CALM (no boat wake, no waves, no current).
Wind was less than 5mph
Full speed with the Torqeedo 2T was 5.8mph into the wind, and 6.1mph going downwind.
The Torqeedo 2T went approximately 3mph at about half throttle.
I didn't have a chance to wire up a Shunt, so I have no idea what the real wattage consumption was - and am looking forward to determining that. At full speed, the Torqeedo pulled the battery bank down to 21V pretty quickly, but it seemed to stabilize there. I also noted that I had failed to actually PLUG IN the battery chargers. The bank is two form factor 31 deep cycle flooded lead acid batteries, with a rating of 160 reserve minutes (at 25A?). Once fully charged, I'll be anxious to get some current drain measurements and see how long the Torqeedo will run at full speed, 5mph, and 4mph.
Trip 2:
Additional data was gathered on 7/20/13. This data was collected on battery bank 1, which is comprised of two group 27 marine deep cycle flooded lead acid batteris (FLA). The batteries were rated for 160 reserve minutes. Initial starting voltage at the dock was 25.8V
Motoring through marina: 500W, 3.5mph. Other data collected:
NOTE: For run data below, results are posted for the following shunt:
200A @ 75mv
Basic Observations:
Torqeedo 2T:
At 4mph, battery life is about 1 hour.
To achieve speed 4mph in 5-10 mph light breeze, power is about 1000W / 50A @ 24V
Motor-sailing can add 1mph of speed to sailing speed at very low power levels.
After battery is run down at higher power levels, it will quickly recover a couple of volts if turned off for several minutes.
Battery life at low power is MUCH longer than at higher power levels.
Torqeedo 2T ~can~ achieve 4.5 to 5mph on the C-22, but it drains the battery bank too fast.
Running at about 4mph will give about 1 hour of cruising time. Speeds of 4.2-4.5 mph are max practical running speeds for shorter durations.
For longer duration trips, 3.0 to 3.5 mph max may be required.
Speed of 3.5mph => should be achievable with about 600-800W (~25A / 24V).
More Outings
7-30-13
7:48 24.3V 8mv 3.4mph Leaving Marina
7:55 25.4V 2mv 1.8mph Motor sailing, reaching toward Starnes Island
8:15 25.2V 2mv 2.6mph Motor sailing
8:30 25.3V 2mv 3.6mph Back side of Starnes Island. Nice breeze from lake channel, clear of Hudson's Bend
8:40 25.4V 1mv 3.7mph Reaching back from Starnes Is. Good wind not blanketed from Hudson Bend
8:46 24.3V 10mv 5.6mph Hit puff, then calmed - 4.5mph @ 11mV
Just sail - 2.6mph.
11mv - 4.0mph
8-7-13
Batt 1: 25.4V, Batt 2: 26.2V Switched 1+2, voltage settled to 25.8V
7:15 24.4V 10.2mv 3.6mph Motoring toward Starnes Is.
7:27 24.4V 10.2mv 4.1-4.3mph ~600W. Raised sail. Motor reduced to 9.6mv
7:40 23.8V 9mv 4.5mph Tacked back and forth in front of Starnes Is.
7:50 23.7V 10mV 3.8mph Tacking past U-Flote-M
8:07 23.7V 0mv - @AYC. Laser / Sunfish races going. Stopped motor. Voltage bounced back almost immediately to 24.7V 1.6mph sailing into wind.
8:11 2.0mph Sailing downwind.
8:16 23.9V 7.9mv 3.6mph Motorsailing reach / downwind
8:28 23.1V 15.5mV 4.4mph U-Flote-M. Sail dropped
8:51 22.4V 16mV 4.4mph
9:00 24.6 Recovered resting voltage. Tied up in slip.
C-30 Outing with Torqeedo 4.0, 48V
1-19-14, 3:40PM, clear skies, upper 60's, no wind (very light North breeze)
Resting starting voltage of 54V
Ran about an hour at ~700 to 780W (about 15A). This dropped the battery voltage to around 47V.
Boat was running about 3.1mph with no wind and no wake.
Briefly ran a few minutes at high power to check speed:
2000W -> 4.1mph
3500W (max power) -> 5mph
Back at dock about 4:40, charger plugged back in, resting voltage then at 50.7V
SHUNTS
In Feb. 2014, I ran some tests to validate a shunt I was using. I had read that the battery cable itself can be used as a shunt, so I included 3 short battery cables in my test. For the test, I used the 48V Torqeedo 4R, with a bank of 4 x AGM 12V Exide batteries with 98 reserve minutes. The motor was run at 250W, 500W, 1000W, 1500W, 2000W, and 2500W, and 3000W for the wires under test.
For each wattage rating, the displayed battery voltage and the voltage (in mV) across the shunt or cable was recorded.
The data was then summarized in a table, resistance values calculated, and then averaged.
Shunt: 75mV @ 200A rating. Average resistance: 3.827E-4 (.0003827) ohms
The expected resistance of the shunt, based on rating, is calculated at .000375 ohms.
Measured value for the resistance of the shunt was within about 2% of the rated value for the shunt.
Voltage drop ranged from 1.6mv @ 200W to 20.3mv @2500W
Cable 1: 24" cable, #4 wire. Average resistance: 9.077E-4 (.0009077) ohms
Voltage drop ranged from 4.5mv @ 250W to 57.7mv @3000W
Cable 2: 49" cable, #4 wire. Average resistance: 1.478E-3 (.001478) ohms
Voltage drop ranged from 7.5mv @250W to 95.1mv @3000W
Cable 3: 49" cable, #4 wire. Average resistance: 1.395E-3 (.001395) ohms
Voltage drop ranged from 7.2mv @250W to 90mv @3000W
Measurements were taken with a Harbor Freight digital multimeter.
In the various calculations, calculated resistance varied about 7% for the shunt, and between 2-6% for the battery cables.
Conclusion: If calibrated, the voltage drop across either a shunt or a battery cable can be used to indicate the approximate amperage consumed by the motor. I have noticed that between several meters, I get about a 5% difference in voltage readings. Since I don't have a "known good" voltage reference, trying to calibrate anything precisely is pointless.
The good news is that it's certainly feasible to use the battery cable itself as a shunt, rather than introducing additional voltage drop (even though it's small) in the motor circuit. Since the battery cable has a higher voltage drop, it might also be a slightly more accurate reference (once calibrated).
OTHER SHUNTS:
I also recently purchased (4) 200A @ 75mV shunts. It'll be interesting to test these against the Torqeedo and see how well the ratings compare.
DEKA AGM Batteries
I purchased 4x12V 8A31DTM Deka AGM batteries at a cost of $200 ea (with $18 core charge and tax...).
These are rated at 210RC @ 25A. In a 48V bank, this should give 1200W for well over 2 hours! Which should also get me over 4.5mph for that 2 hours of continuous use!
The 48V bank was wired with #4 battery cable. I also added sense wires at each battery connection for both banks (Deka and Exide). Color codes for wires followed below list:
GND: Green
12V: Yellow
24V: Black
36V: Blue
48V: Red
TEST 1:
3/16/14 Resting charged voltage: ~52V (charger just unplugged)
2:41pm 1260W 48V
2:45 1280W 48.3V
3:00 1200W 48.4V
3:15 1290W 48.1V
3:30 1250W 47.9
3:45 1250W 47.5
4:00 1200W 47.2
4:15 1250W 46.7
4:30 1250W 46.3
4:45 1250W 45.8
5:00 1280W 45.3
5:15 1270W 44.6
Total test time was ~190min, at ~25A to go from fully charged down to ~44.6V.
Boat was at rest, tied in dock. 56F, high north wind (20-30mph).
Exide Battery Bank (bank 2)
Data collected 3/18/14. Wind started about 12mph out of the south, and died at sunset. Temp started close to 80F, and fell to about 72F after sunset.
Resting starting voltage about 50.6V
6:43 - Leaving Dock
6:45 1200W 48.5V 4.2mph down wind
7:00 1230W 48.2V 4.4mph across wind
7:12 Passed U-Float-M
7:15 1230W 47.5V 4.2mph into 10mph wind
7:24 Passed Austin Yacht Club, turned around
7:30 1200W 46.6V 4.5mph downwind
7:36 Passed U-Float-M
7:45 1280W 46.0V 4.4mph calm Rounding / Passing back side of Starnes Island
8:00 1280W 44.8V 4.4mph calm
8:04 1250W 44.5V Test Ended
Switched to bank 1 (Deka - fully charged) - collected following power / speed data in evening. CALM (no) wind, flat water
200W 2.4mph 4.1A
400W 3.0mph 8.3A
570W 3.4mph 12A
(1280W 4.4mph) 26A - data from previous run
2400W 5.4mph 50A
3360W 5.9mph 70A
3600W 6.1mph 75A (full throttle)
Deka battery test 2: 4/5/2014
Resting battery voltage 51.5V. 64F, wind N/NE, 10-12mph
5:16 Leaving Dock
5:19 2700W 47.3V 5.4mph Into wind
5:30 2730W 47.1V 5.3mph Into wind
5:41 Passed U-Float-M
5:45 2700W 46.4V 5.5mph Across wind
5:50 At AYC - Turning around
6:00 2780W 45.1V 5.9mph Across/down wind
6:04 Passing around back of Starnes Island
6:08 2760W 44.3V 5.9mph Down wind
6:10 2760W 44.0V 5.9mph Stopping test
Switched to battery bank 2 (Exide 98RC AGM) - 53.4V resting
6:12 1240W 48.3V 4.6mph Down wind
6:24 1280W 48.6V 4.6mph Down wind - At marina
Turned around, did 4.4mph into wind at same power
6:32 - tied up at dock.
Resting voltage for bank 2: 51.0V
Recovered resting voltage for bank 1: 48.4V
Summary of test 2:
Battery life of 2700W for 50min (.8333hr)
~61A at 46V >> about 51Ahr
Summary of test1:
Battery life of 1200W for 2.5hr
~26A at 46V >> about 65Ahr
PEUKERT
From the Electric boating group, I'll start with assuming the following Peukert constants for the various battery types:
FLA: 1.25
AGM: 1.10
Li: 1.03
Useful Peukert Formulas:
To get Time to discharge:
t = H * { ( C / (I * H) ) ^k }
Where:
t: Time to discharge
H: Rated Hours
C: Rated Capacity at rated hours
I: Actual Current drain
k: Peukert Constant
To get Amp Hours:
It = C * { ( C / (I * H) ) ^ [k-1] }
Note, to get the exponential value:
x = y ^ z
z = (log x) / (log y)
http://en.wikipedia.org/wiki/Peukert's_law
Torqeedo Prop
Due to a mishap at the dock during my absence, a small chunk was taken out of the Torqeedo 4.0 prop.
The Torqeedo 4.0 and 2.0 both take the same prop.
A replacement (Torqeedo number 1915) was ordered from Defender. (May 2014)