Inverted hot water on TomCat

[Captain Starbucks]

I installed a Victron 1200 watt inverter on my 2009 TomCat next to my 100 AH house battery (underneath the livewell) with 4ga cable. This inverted power runs through 10 ga cable to a SHORE-OFF-INVERTER switch. This way, I can use the inverted power to power my entire grid.

The catch was figuring out what heating element to choose. I couldn't find a 750 watt. Math dictates that would be the best choice for this install. So, I used a 240VAC 3,000 watt element (19.2 ohms driven by 120 VAC = 750 watts). The boat came with a 1,500 watt element.

The water heater in my boat accepts standard house size elements.

The run time calculator takes 6 gallons of 65 degree F water to 120F in 1 hour and 20 minutes.

I couldn't justify buying and bringing another generator when my boat already had 2x25 amp 150hp generators on it.

My boat has 1 lead start battery, 1x100ah house battery, and 3x65ah 12/36 volt (series/ parallel optioned) bank trolling batteries.

Another reason for the inverter i chose is my vacuum bagger uses about 1,000 watts.

The inverter talks to my Victron Cerbo GX brain which also precisely shows my fuel and water tank levels, as well as shows, alarms, and tracks my bilge pumps through a pair of optocouplers. This information is on display through a Victron dedicated display on the helm.

 

[thataway]

I am surprised that a single 100 amp hour battery is enough to run your inverter to heat the water, or any other similar use. You have the good istruments. Can you give us real world time / power measurements?

I had two 100 amp hour LiFePO4 batteries or a bank of 200 amp hours. I jointed this to the Victron Multiplus 150/80/50 with 2/0 cables at a distance of less than 24 inches. The 300 amp fuse was within 6" of the battery bank, and the switch was after the fuse. We changed out the water heater to a Bosch 2.5 gallon under the sink water heater which draws 12 amps @ 120 volts, figure about 120 amps 12 volts thru the inverter. One of the beauties of this set up is that you get ride of the "dead water space" between the water heater and sink/ shower. This prevents loss of water each time you want hot water at the sink. The 2.5 gallons was more than enough hot water for a shower. Heated water in a basin to soap up, then scrub and wrinse off--can be done in a couple of gallons of water. The Li batteries are much better for this type of load. They can be safely drawn down to 10 %. AGM batteries are only good to about 50% capacity.

When looking at alternator capacity output on outboard motors, one has to take into consideration the amount of current draw used by the outboard, and the house loads, including any MFD displays, Radar, Radios, etc. What's left over is good for the dedicated battery bank used on the inverter,

 

[Captain Starbucks]

My family of 4 just finished a 4 day trip overnighting on the boat each night with no hookups. I will say that the system I engineered and installed does indeed work, but I can certainly see the value of a generator. Quiet on demand inverter power is amazing though.

The run time to heat the water to 120 degrees is about an hour and 20 minutes @70 amps. The twin 150s put out 30 amps combined at idle and close to 45 at cruise (observed with full suite of 12" MFD, Victron guage cluster, autopilot, radar and the inverter on powering computers and water heater) The 100 AH house battery was never 100% charged after we left home. It was more of a constant power management of heating the water enough for hot showers, while still arriving at our destination with enough battery so my wife can run her computers while on conference calls while the kids and I hiked and chased crabs around with wetsuits.

I would definitely do this installation again for the reasons I needed, but those reasons generally involve lots of trolling (15 amps)and long runs to black cod and halibut habitat (45 amps). For short runs, there's no way my outboards would supply enough juice to do everything.