MPPT solar controller: Morningstar Prostar v Tristar

[SO49]

Originally Posted by mitiempo

With very rare exceptions running an inverter to heat water or air does not work.

Best to run the engine (if it has a cooling loop through the water heater) for 20 minutes. Or the generator if it is so plumbed.

It would probably be more efficient to do what we usually do - that is, run the generator in the morning to generate electricity to heat water, make coffee and charge batteries. Once you turn on the generator it's best to load it up.

The engine uses twice as much fuel per hour and running it at low speed just to heat water (and maybe charge batteries) is not good for longevity.

I'm going to have to study the issue of using the inverter for large AC loads like the water heater. Inverter efficiency runs about 90% these days and we may have an abundance of excess solar power at some times of the day - much more than battery charging can use. Why let it go to waste.

I see that many trawlers now use inverters left on full time to power refrigerators, TV's and other appliances and 120AC loads.

Jeff

[mitiempo]

Originally Posted by SO49

It would probably be more efficient to do what we usually do - that is, run the generator in the morning to generate electricity to heat water, make coffee and charge batteries. Once you turn on the generator it's best to load it up.

The engine uses twice as much fuel per hour and running it at low speed just to heat water (and maybe charge batteries) is not good for longevity.

I'm going to have to study the issue of using the inverter for large AC loads like the water heater. Inverter efficiency runs about 90% these days and we may have an abundance of excess solar power at some times of the day - much more than battery charging can use. Why let it go to waste.

I see that many trawlers now use inverters left on full time to power refrigerators, TV's and other appliances and 120AC loads.

Jeff

Inverters can power many items, but at a cost. A 1500 watt water heater element consumes about 150 amps DC through an inverter. Depends on solar charging current and battery bank size. I have a customer currently in the Pacific somewhere who uses his inverter to make hot water regularly - however he has a large LiFePo4 battery bank and a very large solar array on his cat. He gets several hundreds of AH per day. He is the rare exception though.

A better solution, if running the generator for charging anyway, is to plumb the gen's cooling loop through the water heater. This way the gen output can be used close to max for charging. Might make sense to add a second high output AC charger to take advantage of this extra gen current and bulk charge faster.

How large is your house bank? What type of batteries?

[SO49]

Originally Posted by mitiempo

Inverters can power many items, but at a cost. A 1500 watt water heater element consumes about 150 amps DC through an inverter. Depends on solar charging current and battery bank size. I have a customer currently in the Pacific somewhere who uses his inverter to make hot water regularly - however he has a large LiFePo4 battery bank and a very large solar array on his cat. He gets several hundreds of AH per day. He is the rare exception though.

A better solution, if running the generator for charging anyway, is to plumb the gen's cooling loop through the water heater. This way the gen output can be used close to max for charging. Might make sense to add a second high output AC charger to take advantage of this extra gen current and bulk charge faster.

How large is your house bank? What type of batteries?

We presently have 400AH of MasterVolt AGM's. We're putting on 800 watts of solar panels for this season and then take that up to 1000 watts. We should be able to harvest around 270AH on a decent solar day and peak at 56 Amps going into the batteries. We have a six gallon water heater/heat exchanger that draws 1200 watts (10 amps at 120V).

[mitiempo]

Originally Posted by SO49

We presently have 400AH of MasterVolt AGM's. We're putting on 800 watts of solar panels for this season and then take that up to 1000 watts. We should be able to harvest around 270AH on a decent solar day and peak at 56 Amps going into the batteries. We have a six gallon water heater/heat exchanger that draws 1200 watts (10 amps at 120V).

Assuming over 50 amps from the current 800 watts of solar on a full sun day and battery bank at 50% SOC the bank should be at absorption by mid day. This gives you extra current for other uses in the afternoon. The problem as I see it is if you consume 60 AH to heat water (120 amp draw for 30 minutes) as well as other draws the batteries will once again drop below absorption level and at the time you will be running out of full sun. This could easily leave the battery bank at some level below full charge which can be fatal for AGM batteries.

If on the other hand the water is heated in another way such as a loop from the generator this problem doesn't come up and the batteries should be fully charged on many sunny days.

400AH does strike me as a pretty small bank for a larger boat with many systems. It doesn't give you much reserve for non charging days. 800 watts of solar is plenty when the sun shines. If you are willing to use the gen often it isn't much of a problem though. And with a coolant loop from the gen through the water heater you would probably have all the hot water you wanted.

What is your daily consumption in AH?

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[SO49]

Originally Posted by mitiempo

Assuming over 50 amps from the current 800 watts of solar on a full sun day and battery bank at 50% SOC the bank should be at absorption by mid day. This gives you extra current for other uses in the afternoon. The problem as I see it is if you consume 60 AH to heat water (120 amp draw for 30 minutes) as well as other draws the batteries will once again drop below absorption level and at the time you will be running out of full sun. This could easily leave the battery bank at some level below full charge which can be fatal for AGM batteries.

If on the other hand the water is heated in another way such as a loop from the generator this problem doesn't come up and the batteries should be fully charged on many sunny days.

400AH does strike me as a pretty small bank for a larger boat with many systems. It doesn't give you much reserve for non charging days. 800 watts of solar is plenty when the sun shines. If you are willing to use the gen often it isn't much of a problem though. And with a coolant loop from the gen through the water heater you would probably have all the hot water you wanted.

What is your daily consumption in AH?

Hard to say, but I see your point. Either I get another 800 watts of solar and additional batteries or break down and run the generator in the AM. (We have a heat exchanger loop on the main engine and I'm really not inclined to start a new plumbing project - sorry).

I do thank you for taking the time to help me with my thinking process. This thread has been great in answering a lot of the questions I've had in my solar project. I'll report back as we go.

Right now my canvas shop is working on the solar panel and wiring harness install for the top of the bimini. He's had a bit of experience and likes to sew zippers on the forward and aft sides of the panels with protective flaps over the zippers. The panels will lie athwartships on both sides of the centerline with a wiring harness down the middle of the top of the bimini exiting down the hole for the starboard backstay. He's installing belt loops so the wiring harness can be secured with cable ties and will also have a velcro'ed canvas cover.

My plan for the harness is to use MC4 connectors to connect each panel to the harness and additional MC4 connectors at the end of the harness where the wiring enters the boat.

It will be tricky getting the panels on the bimini. Probably do one section at a time as the bimini is being installed. Then raise the section and do the next. We'll see how it goes.