Inverter water heating

[kevin123]

FAir play Kenbo you have got a valid point I will have to be quick in the shower but I just want to get hot water without running the engine or destroying the batteries

[kevin123]

Thanks to everyone for their replies
Kind Regards
Dave

[Pete7]

Originally Posted by kevin123

Thanks Kenbo I was under the assumption that I can generate 300 amp hours each day with 800 watts of solar and 2 wind turbines am I missing something?

Yes probably and a bit more with luck. Are you in the UK? if so then you get more during the summer and nowt during the winter that's worth measuring. However, this is good news as you get lots of solar power when we are on holiday

A portable black shower bag with 15L of water also works.

Pete

[CharlieJ]

Your 900Ahr bank is the C20 (20 hour rate). 900Ahr/20hr = 45A. If you exceed this draw, the battery bank will not yield its full capacity. And speaking of full capacity, lead acid batteries generally are not discharged to a SOC < 50% so you have 450Ahr available.

1500W will require 125A @ 12VDC assuming a perfectly efficient inverter. 125A is almost 3 times the C20 rate. Your bank's voltage will drop down below 11.0VDC fairly quickly and, depending how your inverter is programmed, it will shut down on low voltage and you will quickly damage your house bank.

This is not the best idea I have heard.

[Lepke]

I can heat water with a large 120/240 inverter, but rarely do it. I run a generator every 2-3 days when anchored to make water, laundry, dishwasher, recharge bank, etc. And I have a large 48v bank.
I super insulated my 50 gallon water heater with 2" foam all around, top and bottom. All water lines are insulated, even cold so it doesn't draw heat out of the tank. Hot water will last 2-3 days depending on use.
Insulating your hot water tank and the lines will make it easier for your wind and solar to heat water and it will stay hot longer.

[noelex 77]

You should not have any problems. We have much the same battery and solar capacities and in reasonable weather heat all our shower water electrically via solar. We have a slightly different system that does not use a calorifier, but that should not make much practical difference.

Check your inverter is capable of 1500w continuous in hotter ambient temperatures. Most good quality 2000w inverters will do this, but not all. Fortunately, water heating has a power factor of close to one so watts are almost the same as VA (inverters list VA rather than watts). If your inverter cannot cope, you can exchange the element for a lower wattage unit.

In poor solar areas/seasons such as winter in higher lattitudes, we switch to heating our water with a diesel heater, and if you plan cruising areas with poor solar insolation you will need a similar alternative method.

[dougweibel]

Originally Posted by CharlieJ

1500W will require 125A @ 12VDC assuming a perfectly efficient inverter. 125A is almost 3 times the C20 rate. Your bank's voltage will drop down below 11.0VDC fairly quickly and, depending how your inverter is programmed, it will shut down on low voltage and you will quickly damage your house bank.

This is likely inaccurate. The OP does not specify what type of battery bank he has, only the size. For my AGM bank the battery manufacturer's data sheet clearly shows that the batteries will perform fine at a C5 rate, and even higher discharge rates. My batteries will hold above 11.8 volts for at least an hour and above 11.5 for three hours at a C5 discharge rate. The battery manufacturer gives no indication of reduced life at C5 discharge rates so long as state of charge is not drawn down below normal levels.

[LoudMusic]

Originally Posted by kenbo

If you use solar to make electricity why not consider using solar to make hot water directly. Much more efficient. https://heliatos-solar.myshopify.com/

Because then I can't use it to make electricity, which is much more useful than hot water. And I've seen reports that say it's not much more efficient anyway.

I have considered some kind of water loop under the panels where it gets quite hot and a little pump to circulate it. But that also adds considerable weight and plumbing to maintain.

[sailorboy1]

I rewired my electrical last year to allow the HW heater off the inverter. I only do it for the 20 minutes it take to make warm enough water for 2 showers. The solar makes up for the load during the day as it has more capacity than my normal use and I try to remember to make the water at mid day with good sun, But I bet I could probably run longer or maybe even leave it one.

I have 461 AH batteries and 640W of solar.