Mischief Torqeedo

Mischief Goes Electric 10/4/2016

I *FINALLY* got a chance to do something I've been wanting to do a very long time....

Back in the summer, I sold the Nissan 30HP motor, since we weren't taking the boat out, and had the Regal in a slip on the lake. I was really curious to see what Mischief would run like with a Torqeedo on her.

Well, I finally got around to it!

Below are a couple of pictures taken of Mischief after we had completed the first test run on Lake Austin, on 10/4/2016.

The motor is powered by 4 Deka 8A31 AGM batteries. The first test run was just a test, so things weren't set up for peak efficiency. Two of the batteries were placed in the front, between the seats and the bulkhead. (Note - the two 65 pound concrete filled 6 gal tanks in the front were removed. The other two batteries were placed in the rear, just inside the transom. A section of ~16' jumper cable wire was used to connect the two sets of batteries (significant drop, due to length and gauge of wire?). A 48V charger was placed on the battery set. The 12V devices on the boat (depth finder, lights, bilge pump) were all picked off the lowest battery in the string (also not optimal). And finally, the trim tabs were left in place. Given the performance of the boat, they are most likely absolutely unnecessary.

Note: The stated weight of a 4-stroke Nissan 30hp motor with tilt and trim is about 170 pounds. Then there's the starting battery (about 30-50 pounds), and a 6 gal. gas tank, plus spare reserve tank (about 6 gal. total - approximately 50 pounds). Total is about 260 pounds.

The Torqeedo 4R weighs in at about 37.5 pounds. However, the AGM batteries are 70 pounds EACH. Total weight is about 320 pounds. Total weight of the entire boat with passengers, batteries, motor, etc. was probably around 800-1000 pounds. Note that since two of the batteries replaced the concrete ballast in the front of the boat, the weight of re-powering with electric basically washed out vs. the heavy gas engine, or got slightly better - and was certainly much better distributed.

While heavy, the boat handled very well. I was disappointed that top speed wasn't higher - but the 48V Torqeedo simply won't generate enough horsepower to get this hull shape with this much weight up on plane. Tracking was great. Operationally, she did fine - just not very fast. At low speed, she can cruise slowly very well, and probably for a very long time.

Here's the data from our trip:

Launched at about 1:56pm. Very little traffic on Lake Austin (as it was a Tues. afternoon, early fall - school in session). Fairly strong breeze blowing - possibly 10mph. Slight chop from the wind at times. Occasional boat wake from other ski boats. Resting voltage was possibly around 51V (didn't specifically log it - should have...).

Watts Volts Speed Direction

2270 46.7 5.6mph upwind Leaving boat ramp - 1:56pm

1000 48.5 4.4mph upwind

960 48.6 4.6mph downwind

500 49.2 3.8mph downwind

300 49.7 3.2mph downwind

2800 46 5.6mph downwind WOT (should be around 4KW)

1000 48.5 4.3mph upwind

620 48.9 4.2mph downwind - Entering Bull Creek - protected from much of the wind. 2:09pm

625 48.8 3.9mph upwind

645 48.8 3.7mph upwind 2:18 (probably about to leave Bull Creek, back into main body of the lake/river.)

1000 48.4 4.7mph downwind

Note - Hull speed for a length of 13' is about 4.8mph.

Back on trailer at 2:37 - About 30 min. total running time. Resting voltage: 50.5V

3:45pm - Home with boat back in the garage.

5/2/20

Purchased E-bike LiFePO4 battery for more experiments and proof of concept (POC) work.

Battery: BtrPower $429 / Amazon

Nominal: 48V Rated @ 20Ah

Charging voltage: 58.4V

Cut off voltage: 40V (Advertised) - Actual BMS cutoff voltage around 48-49V

Charged, resting voltage: 55.4V

Max discharge: 100A

Rated discharge: 50A

Literature claims 14 cells in series, 1 parallel.

Battery came with 5A charger, and 2 x 50A/600V Anderson plugs.

5.75" x 5.75" x 10.5"(tall) - Fits in standard (group 24) battery box - no extra room on long dimension..

Weight: 19 pounds, 2 oz

NOTE - similar current offering on Amazon (5/2/20) shows charging voltage of 54.6V, 16 cells in series, dimensions of 10.6 x 6.9 x 3.7" (should still easily fit in group 24 battery box). NewEnergy - $388 for 20Ah battery

Battery was wired into boat, and tested in a "garbage can trial" on 4/30/20. Could only run up to 100W, due to water circulation in the garbage can - but all seemed fine.

Ordered additional 120A Anderson plugs to fit Torqeedo wiring harness.

Plan:

Would be nice to wire battery through 40A - 50A breaker, to battery switch, then Anderson plug to motor.

If single battery works well, would be nice to order 2nd backup battery for "get home".

If batteries exceed expectations, then 2 wired in parallel should provide 1.5+ hours at 20A, 960W for 4+mph, or close to 3 hours at 12.5A, 600W.

20Ah battery should provide 1.5+ hours at 10A, 480W - about 3.5mph. Or, 1.25 hours at 12.5A, 600W - about 4mph.

Editorial thoughts:

I like the form factor of the E-bike batteries. It's nice to get a 48V package. The 20Ah packs are a reasonable size and weight to work with. If money was no object, 4 of them in parallel would provide 3500W for about an hour, which would allow a reasonable "max running" throttle for the Torqeedo, though the speed increase would be only slightly more than hull speed. Two batteries in parallel would probably give hull speed for around an hour, with a third battery as a backup for slow speed cruising.

The concerns are in how the battery packs and their built in BMS's are wired. There are no details on the operation of the BMS. For example - there is no mention of whether the BMS will self-reset if it trips on high or low power limit. No idea if will blow an internal fuse or FET, and "brick" itself.

The manufacturer also states that the batteries should ONLY be charged as single units (not in parallel), ONLY through the charging port (which electrically appears to be wired to the discharge wires?), with the provided charger - so switching the batteries in parallel would have to be done such that they can easily be disconnected for individual charging. Since the packs are already at 48V, this could be done with individual on-off switches on each battery to allow parallel combining at will. Then, the primary concern would be how to ensure that power was evenly pulled from each paralleled battery. This could be done with shunts on the battery to monitor the current usage from each.

Below are the results of battery tests. The first battery test was conducted using the Torqueedo, at a setting of 1000W, at Lake Austin, under the 360 bridge.

BTR E-Bike Li-Ion battery - Rated 48V, 50Ah

First bench test - 6/13/20

Resting Voltage (full charger output): 58.5V

Weight: 29.5#

Dimensions: 13.25" x 6.25" x 6"

Garage Bench Test 50_01:

Load: 16 x #9006 headlight bulbs (4 parallel sets of 4 in series - 4s4p) ~ 17A

Resting voltage: 58.8

BMS cutout voltage: 40.6

Duration of test: 3 hours

Approximate AH: 51

Garage Bench Test 50_02

Same as above - 16 headlamp bulbs (#9006), arranged with 4 in series (to get 48 Volts), then 4 groups in parallel to get about 16-17A.

Second test again ran to almost exactly 3 hours before the BMS disconnected the battery internally.

Approximate AH: 50.1

Observation - Voltage and current dropping off as battery discharges with (presumed constant - same bulbs) load.

Garage Bench Test 50_03

Very similar to above test results. 16 bulbs, battery ran for right at 3 hours before shutting down at about 40V.

LAKE TEST - 6/22/20!!!

Date: 6/22/20

Time: 8:51am

Weather: 83F, overcast but no rain, slight breeze out of the south.

Boat: 13'4" LOA, 5'9" Beam, 300-500 pounds - plywood construction. Bottom covered in xynol and epoxy.

Motor: Torqeedo 4R, 48V system, 4000W max input.

Battery: BTR eBike battery, 48V system, 50Ah rating

Starting Battery voltage was 58.4V resting. At end of test, resting voltage was 54.8V. Approximately 30-50% of the battery capacity was used during the test.

Duration of the test was approximately an hour. Launched at the 360 bridge ("Pennybacker Bridge") boat ramp in Austin, Texas.

The boat was taken out and run at several power throttle settings, with time, wattage, battery voltage, and speed recorded. Performance was very good. Boat handled extremely well, with good tracking and turning characteristics.

The boat was taken south on the lake, and up into Bull Creek, then returned north, past the boat ramp, and finally returned.

Below is a table of some of the data points recorded during the test. (data points are not in time sequence)