A Question Regarding Excess Charge....

[ArtM]

This is an extremely interesting question. From a basic point of view, it seems pretty reasonable. Yet, I believe that under analysis it breaks down.

First, there is the question of whether you are really collecting "excess power"... or are you actually collecting a deficit of power in an uneven way, and trying to figure out how to reduce wastage in order to come closer to meeting your needs?

If you are truly collecting excess power, then the system you describe would soon be generating excess heated water, and excess fresh water, and soon thereafter would be again dumping excess electricity. In this case, you will never be able to use "all" the power, you will simply have a larger reservoir for that power - that is, you are using water tanks as additional energy storage units. Based on this analysis, you would achieve the exact same effect by adding one or more storage batteries, then using that additional storage at your convenience, or by use of some other timing method to heat water and desalinate.

If you are not collecting enough power, and need to spread your load out a bit, then again an additional battery would partially, but not fully fill that gap.
Since the period of excess charge is generally predictable - i.e. between 12pm and 2pm, for example, perhaps it would make sense to put on a simple timer that runs your desal or water heater at these times. This would be a very inexpensive hardware item.

So, if I've thought this through correctly, I think you could achieve your goal either with an additional battery, or a 110v timer, or both.

[noelex 77]

It is common for solar systems to be producing more energy than is used, particularly during the better months.
More batteries do not make any difference after a few cycles because there is still an excess of power. Solar regulators will turn off the panels for short periods so the solar output matches the usage with no overcharging of the batteries, but it's nice to be able to do something useful with it. This requires an increas in consumption not an increase in storage.
Most boats do this in a non automated way.

For example today my solar panels will produce about a 175-20 Ahrs. This is much more power than I need or normally use. Rather than just regulate and throw that power away I have my chartplotter and radar running. These not needed, but it's blowing 30K gusting to 40K and the radar shows the exact distance of catamaran that is anchored just in front of me. I know the cat is very unlikely to drag as their Rocna anchor is completely burried and on a good scope. The radar is not needed, but the power to run it is free so why not have it on?

[S/V Alchemy]

Originally Posted by Lagoon4us

Agree with some of your points however when we are not on the boat the systems are always reduced to a minimum.
To fall in line with your suggestion what read-out do you reccomend that accurately tells me that we have reached 90% charge so confidently we can startup the inverter?
We have a MorningStar RM1 and that gives only max and min voltages and voltage status along with battery temps. Cheers Frank

If I were leaving the boat at anchor for a day or so, I too would shut all the seacocks, and everything except the pumps and the fridge. That might include the panels (and wind gen) themselves.

It's part-paranoia and partly a desire for simplicity.

My bank would be sufficient to handle the fridge for several days alone, and the peace of mind about not dumping loads of current unmonitored into
(first) batteries, (then) echo-charger for the start, (then) the inverter and (then) the hot water...well, I can discern several issues.

Leave the banks fully charged, shut off 90% of the boat (maybe a darkness-activated anchor light stays on? An LED in the cabin to suggest occupancy?) and go ashore knowing you aren't relying on several fuses, relays and shunts to stay unburnt.

If I am aboard to even casually monitor processes, certainly I want to make use of that extra charge when desirable. My whole plan for long-term cruising is predicated on independence from shore and energy management that does not require switching on the diesel to make amps...although I am happy to make amps when motoring, primarily to make ice and RO water.

[S/V Alchemy]

Originally Posted by noelex 77

It is common for solar systems to be producing more energy than is used, particularly during the better months.
More batteries do not make any difference after a few cycles because there is still an excess of power. Solar regulators will turn off the panels for short periods so the solar output matches the usage with no overcharging of the batteries, but it's nice to be able to do something useful with it. This requires an increas in consumption not an increase in storage.
Most boats do this in a non automated way.

For example today my solar panels will produce about a 175-20 Ahrs. This is much more power than I need or normally use. Rather than just regulate and throw that power away I have my chartplotter and radar running. These not needed, but it's blowing 30K gusting to 40K and the radar shows the exact distance of catamaran that is anchored just in front of me. I know the cat is very unlikely to drag as their Rocna anchor is completely burried and on a good scope. The radar is not needed, but the power to run it is free so why not have it on?

Well, there's the thought that the moving components of the radome are subject to wear, but generally that's sound thinking.

As I said in my last post, I'm outfitting from the premise that I never want to require shore power. That means I have to understand my energy budget fairly well and account for debits and credits down to the amp.

I have told my family that "movie night" at anchor is going to be based on logging amps made and amps used. That's part and parcel of watermaking, hot showers, ice cubes, microwave popcorn and other amp-intensive operations, including lots of SSB transmission, perhaps, or charging every damn gadget on the boat at once.

My solution is to have a bigger bank, which is impractical and/or undesirable for most people, and to keep said bank generally in a narrow range of cycling, like between 75% to 100% SOC, acknowledging that I have only 40% or so of that entire charge to play with.

The numbers fall in line for wind and sun after that is considered. One makes water while the sun shines.

[noelex 77]

Originally Posted by S/V Alchemy

My solution is to have a bigger bank, which is impractical and/or undesirable for most people, and to keep said bank generally in a narrow range of cycling, like between 75% to 100% SOC, acknowledging that I have only 40% or so of that entire charge to play with.

It sounds like you are thinking carefully about your energy budget, which is most of battle.
Don't forget batteries do not produce any power, they only store it. No matter how big your battery bank is your energy budget still needs to be balanced.
Concentrate on maximising the energy producers and minimising the energy consumed.
Large battery banks are of great help for those boats using generator power where the larger capacity gives more rapid charging, minimising the generator run times. If using solar and wind power a large bank with very shallow discharge will cost more to run per year.

[monte]

I would like to do the same...convert excess solar to heat the HWS. Today the 700Ah bank was full at noon, but no hot water for a shower. I didnt realise I could plug the HWS into the inverter, but Ill try that first and see what it takes to heat the HWS.
Should I be concerned about large fast loads on my wet cell batteries? possible gassing or damaging them?
Automated would be nice as well...
I just plugged in the 1200w HWS to the 1600A Inverter and its showing 132 A out on my victron monitor and SOC is dropping fast.
I wonder how long it takes to heat the water...

The solar controller is a tristar 60A Mppt..does this have load diversion options?

[Lagoon4us]

Originally Posted by ArtM

This is an extremely interesting question. From a basic point of view, it seems pretty reasonable. Yet, I believe that under analysis it breaks down.

First, there is the question of whether you are really collecting "excess power"... or are you actually collecting a deficit of power in an uneven way, and trying to figure out how to reduce wastage in order to come closer to meeting your needs?

If you are truly collecting excess power, then the system you describe would soon be generating excess heated water, and excess fresh water, and soon thereafter would be again dumping excess electricity. In this case, you will never be able to use "all" the power, you will simply have a larger reservoir for that power - that is, you are using water tanks as additional energy storage units. Based on this analysis, you would achieve the exact same effect by adding one or more storage batteries, then using that additional storage at your convenience, or by use of some other timing method to heat water and desalinate.

If you are not collecting enough power, and need to spread your load out a bit, then again an additional battery would partially, but not fully fill that gap.
Since the period of excess charge is generally predictable - i.e. between 12pm and 2pm, for example, perhaps it would make sense to put on a simple timer that runs your desal or water heater at these times. This would be a very inexpensive hardware item.

So, if I've thought this through correctly, I think you could achieve your goal either with an additional battery, or a 110v timer, or both.

My thinking is that once water has been heated, tanks are full and batteries charged then my charging system has functioned in the most efficient way it could so our return on our investment is 100% given our needs.
Cheers Frank

[Lagoon4us]

Originally Posted by monte

I would like to do the same...convert excess solar to heat the HWS. Today the 700Ah bank was full at noon, but no hot water for a shower. I didnt realise I could plug the HWS into the inverter, but Ill try that first and see what it takes to heat the HWS.
Should I be concerned about large fast loads on my wet cell batteries? possible gassing or damaging them?
Automated would be nice as well...
I just plugged in the 1200w HWS to the 1600A Inverter and its showing 132 A out on my victron monitor and SOC is dropping fast.
I wonder how long it takes to heat the water...

The solar controller is a tristar 60A Mppt..does this have load diversion options?

There are lots of load diverters available ex landbased isolated solar systems, and also as has been noted elsewhere in this thread using ex windgen controllers.
It has to be auto or you'll drain those stored amps!

[hummingway]

Originally Posted by monte

I would like to do the same...convert excess solar to heat the HWS. Today the 700Ah bank was full at noon, but no hot water for a shower. I didnt realise I could plug the HWS into the inverter, but Ill try that first and see what it takes to heat the HWS.
Should I be concerned about large fast loads on my wet cell batteries? possible gassing or damaging them?
Automated would be nice as well...
I just plugged in the 1200w HWS to the 1600A Inverter and its showing 132 A out on my victron monitor and SOC is dropping fast.
I wonder how long it takes to heat the water...

The solar controller is a tristar 60A Mppt..does this have load diversion options?

It takes me 1/2 hour to heat water on mine. I alwys run the gen and wouldn't use the batteries unless you have a 12v element. It'll be too hard on your batteries.

[Lagoon4us]

Originally Posted by hummingway

It takes me 1/2 hour to heat water on mine. I alwys run the gen and wouldn't use the batteries unless you have a 12v element. It'll be too hard on your batteries.

I think the land based solar setups simply divert the excess into a 12volt (as you say) element same as the windgen using it as a load, i don't think they go through the battery circuit?
? Frank

[noelex 77]

Originally Posted by monte

I would like to do the same...convert excess solar to heat the HWS. Today the 700Ah bank was full at noon, but no hot water for a shower. I didnt realise I could plug the HWS into the inverter, but Ill try that first and see what it takes to heat the HWS.
Should I be concerned about large fast loads on my wet cell batteries? possible gassing or damaging them?
Automated would be nice as well...
I just plugged in the 1200w HWS to the 1600A Inverter and its showing 132 A out on my victron monitor and SOC is dropping fast.
I wonder how long it takes to heat the water...

The solar controller is a tristar 60A Mppt..does this have load diversion options?

Heating water takes a lot of energy and it's generally not practical to produce much effect from a boats solar system.
How many solar watts have you got?
How many AHrs do you think are excess on a good day?

Automating the process is difficult due to the high power demand. For example if set the regulator to heat the water when the batteries hit float the 130A demand will almost imediatly drop the batteries out of float.

If you do have enough solar power to make it worthwhile their are some 12v heating elements available for some hot water systems or a homemade low wattage element (say 100w) to very slowly heat the water will be easier to control.

If you can spread some black pipes on deck a small water pump could produce a lot of hot water but this is not easy to incorporate on most boats.

[monte]

I just tried it and it heated the HWS in 30 mins, took about 75Ah from my battery bank but I was concerned about the fast discharge rate damaging my batteries. Voltage dropped to about 12.6V. I would prefer a slower discharge so Ill look into the 12v element , maybe I can add one in addition to the existing 240 one? Also is this the unit I need to use the excess automatically?
Morningstar TriStar Controller Relay Driver, RD-1

Noelex, I have 540w panels plus a wind gen. At anchor im lucky to use 100amps and today the panels were producing 30amps for about 8 hrs, so there should be ample reserve to heat the water.

Im not after hot water on tap every day, but it would be nice for me (and my friends) if I could have a shower occasionally!

The boiler is a Quick 25l 220v1200w unit. Would it just be a case of replacing the element with one of these
Water Heating Element for 12V or 24V DC
and adding the above relay to the existing solar controller?
How does the HWS heat when I am on shore power then? through the batteries and then they recharge through the shore power?

[Lagoon4us]

As far as i've found out our elements are interchangeable, when on shore power your solar is still there doing the same things?

[Lagoon4us]

Can't you use the HWS as the load for the wind-gen when batteries are charged instead of resistor bank or however it's set up?

[hummingway]

Originally Posted by Lagoon4us

I think the land based solar setups simply divert the excess into a 12volt (as you say) element same as the windgen using it as a load, i don't think they go through the battery circuit?
? Frank

Absolutely. Monte's unit though is 240v so he's got to use the inverter as it is.