Can I use my blender or [insert favorite electrical appliance] on my boat?
So if you’re wondering (like me) if you can use your favorite household appliance on your boat – here’s what you need to do to figure it out.
Step one is to figure out how much electricity the appliance needs to operate. To do that turn over the appliance and find the power rating label - everything is required to have these I think. Here’s a photo of the label from my Vitamix blender.
The important information you’re looking for is the volts, amps or watts rating. From this label I know that the Vitamix uses 11.5 Amps at 120V.
Step 2 is to convert that power from 120V to 12V since Sargo’s power is coming from a DC battery bank. You do that by using the formula AMPS * VOLTS = WATTS. So multiplying 11.5 Amps * 120 volts = 1,380 watts.
Step 3 check your inverter rating. Most cruising boats have both DC and AC circuits. Household AC appliances run off the DC battery through the inverter. Since the Vitamix will run on Sargo’s AC 110 Circuit through an inverter I need to make sure the inverter is large enough. Right now Sargo’s inverter is rated to 1,000 watts. So nope – that’s not going to work. BUT, we are considering an upgrade to a 3,000 watt inverter in which case it will! It’s probably good to have extra room on the inverter vs. what the appliance needs.
Step 4 is to calculate how much stored battery power it will actually take to use the appliance. To do this I need to convert the watts back to amps at 12 volts. Using the formula above again and a little algebra AMPS = WATTS / VOLTS. In this case: 1,380 watts divided by 12 Volts = 115 amps. There is definitely some loss when converting from DC to AC so let’s round that up to 150 amps. To determine the “volume” of battery power used (expressed in Amp hours), I then would multiple the 150 amps by the amount of time in hours the blender would be used. Let’s say a heavy use blender day would look like breakfast smoothies, some food prep like hummus, and then evening frozen cocktails equating to maybe 5 minutes of total Vitamix run time? 5 minutes is only 5/60 or .083 hours. Rounding that up to say .1 hour. The “volume” of stored battery energy I would need is .1 * 150 = 15 amp hours . Since I have about 450 amp hours of usable energy in my battery that’s about 3.3% of what’s there. That’s not nothing, but seems doable to me.
STEP 5 is to figure out what it will take to “make back” that energy consumption? I’ve just drawn down by battery by 3% and I need to recharge it. Let’s just assume it’s a sunny day so my solar panels are working. One of our 330 Watt panels can put 100 amp hours into our battery over the course of a full day = so assuming a 12 hour day that’s an average of 8.3 amps per hour. Of course there will be hours around mid day that are much higher, and hours in the morning and evening that are much lower. But using 8.3 amp average – that means it will take TWO AVERAGE HOURS of charging from one of our HUGE solar panels to supply power to the Vitamix. YIKES!!!!!!! Most boats don’t have that sort of solar generating capabilities. A rule of thumb for how many amps a well functioning solar panel can put into a battery you can use is the following: For every 100 watts of solar = 6 amps per peak sun hour. As described above all hours of the day won’t be at peak - so use 5 as a multiplier for hours of sun and you get 6 amps * 5 hours = 30 amp hours generated by a 100 watt panel over the course of a day.
STEP 6 is to determine if the energy usage for that appliance is “worth it” to you. I’m not so sure anymore if my Vitamix is - that would be a considerable amount of charging time toward its use! Of course I could also regulate my Vitamix usage to times when the batteries are full and we are running the engine or generator and have lots of extra power coming in - but that’s no fun!