Jerry,
If the motor is a 48V system, then take a serious look at the eBike batteries. When I was looking, it was significantly less expensive buy a 50Ah eBike battery, than it was to try to put together a system of cells of that size.
If you want more than 50Ah, then you'll need to roll your own, though at least 12V assemblies are available, if you want to build up from that, instead of individual cells.
Obviously, much faster to build up with 12V banks than 3V cells.
One of the drawbacks of using the eBike battery is that I had concerns about putting two eBike batteries in parallel. Since I don't know what's inside, I can't be sure that tying eBike batteries is safe. The vendor recommends NOT tying in parallel.
One of the things that I really liked about the BTR eBike batteries is that they fit in standard battery boxes. So I can fit an entire 48V, 50Ah chunk in one group 31 battery box.
John
On Thursday, June 25, 2020, 11:50:01 AM CDT, shredderf16 <shredderf16@sbcglobal.net> wrote:
John,
It's a 48v motor. The prototype cat would plane with a 200 lb man with a 4 hp Yamaha gas. I'll probably end up with a lifepo4 pack that is self made due to the issues you identified. The bike packs intrigue me because I can carry them home for recharging versus having to put solar panels on the boat.
Jerry
On June 24, 2020, at 11:04 PM, "john via groups.io" <oak_box=yahoo.com@groups.io> wrote:
Jerry,
Unfortunately, the wiring on the batteries is small. Probably only good for 30A. I currently have a 30Amp breaker between the battery and the motor to prevent overheating the wires coming out of the battery.
I was hopeful I would get a chance to test cranking up the motor at the dock when the boat was back on the trailer - but a barge was taking up two of the 3 lanes, and a line was starting to form, so I didn't have a chance to test what power level (and how long) would trip the breaker.
If the Chinese motor will put out 2kw worth of power, you should be fine. I have tested a Catalina 22 with a Torqeedo 2T (2000W max). At 1000-1200W, the C22 went about 4mph. The C22 is a MUCH tougher shape to push than your catamaran, and MUCH heavier. As always, if you want to go much faster, you'll need a LOT more power.
Dramatically increasing the power will get you a little more speed - but it's not sustainable. Even if the battery wiring could handle 2500W (max rating of the battery - probably based on the wiring...) - it would exhaust the battery in under an hour. I want at least 2-3 hours of cruising time for a power boat to be considered practical. At 500-600W, I should be able to cruise at 3.5-4mph for 3-4 hours on a 50Ah battery. At 500W for 3 hours, I'll have a nice cruise without overly exhausting the battery.
Do you have a place to mount a single motor (between the two pontoons?)
You may also be challenged to find 24V eBike motors.
For my boat - the sweet spot for cruising seems to be around 600W - hitting around 4mph. At that power level, a single 50Ah, 48V eBike battery should give me around 2 hours of cruising. And then, if "something bad happens", I have the 20Ah backup battery that should give me around an hour of "get home" cruising.
On Wednesday, June 24, 2020, 10:38:16 PM CDT, shredderf16 <shredderf16@sbcglobal.net> wrote:
John,
Please cranky uppy to 4k watts and let us know results. I got a 2.3 kw chinese motor and building 12' catamaran dinghy. I think I can get by with the one motor but may need two. Thinking bike batteries like you did.
Jerry Barth
On June 24, 2020, at 3:45 PM, "john via groups.io" <oak_box=yahoo.com@groups.io> wrote:
On Monday, 6/22/20, I conducted my first on the water Lake trial with my electric conversion, "Mischief".
Mischief is a home built plywood runabout, currently powered with a Torqeedo 4R outboard. Specs are below:
LOA: 13' 4" (without motor)
Beam: 5'9"
Weight: about 300-400#
Draft: approximately 6-7", with motor up.
Theoretical Hull Speed: 4.9mph
Motor: Torqeedo 4R electric outboard (with remote steering)
48V, max 4000W input
Battery:
Main battery bank: 48V 50Ah eBike battery system from BTR (ordered on Amazon) (approx $900)
Backup / get home battery: 48V 20Ah eBike Battery system from BTR (under $500)
Both battery systems were bench tested. For each test, the battery was fully charged, and then connected to sets of #9006 12V halogen light bulbs (4 bulbs in series gives a 48V load at about 4A). Time and voltage were recorded periodically until the battery BMS shut down the voltage output from the battery. Tests were conducted with 4, 8, and 16 bulbs (max was 4 parallel sets of 4 bulbs, approximately 800-900W). I have the data on these tests, if anyone is interested.
At the lake!!
First test was a static test of running the boat at the boat ramp (the motor needs to be in the water when running). The motor was run at 1000W, and ran for approximately 45 min before the BMS dropped out, on the 20Ah battery. The BMS dropped out at about 48V. (The BMS on the 50Ah battery drops out at around 40V.)
The first "on the water" test lasted for approximately an hour, and used approximately 30-50% of the capacity of the 50Ah battery bank.
Performance of the boat consistently met expectations. Handling was great. As long as you're ok with a walking speed cruise - the boat performed very well.
Volts Amps Watts MPH
58.2 5.15 300 3
57.0 6.5 370 3.5
56.8 8.80 500 3.9
57.7 10.4 600 4
56.0 15.71 880 4.9
57 17.54 1000 5
56 26.79 1500 5.7
If anyone would like more details, feel free to contact me.
John
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