A way To Save Charging Time

[Kenomac]

Originally Posted by capitangiorg

Ken, on Creuza I had a very similar setting.
I had to run the genset 2-3 hours por day, then I installed 520 W of Enecom (4x130W) flexible solar panel on the bimini.
After the installation 1 hour por day running the genset while we were producing water and hot water was enough and some day I didn't need to run the genset.
In my experience the flexible panel are less efficient that the rigid one though they are nicer and easy to install on a bimini.
So if you in any case are going to run the gen for breakfast and supper 450W should be enough for refrigeration, lights and for topping up the batteries.

Thanks, this is exactly what I need to know. From the other posts, it looks like 100Ah back into the battery bank is realistic.

[mrm]

Originally Posted by Fuss

No it's not hard, the certainty is that properly installed 450w of solar in the med in summer will put on average 100 ah back into your 24v battery bank over 24 hrs.

Let's not get complicated here, the guy wants to know roughly what goes back into his battery bank in the med when he has 450 watts of solar. And the answer is 100ah. Let's leave it uncomplicated and not over discussed... it's the problem with these forums, things get over discussed on here until no one can tell what's right and wrong any more.

While I like simple, oversimplification is not good. How can you be sure of your answer without knowing what the continuous drain on the bank is? Knowing the panel wattage and location gives an approximate answer to how much energy is produced daily, but how much will be stored in the bank (if any at all)? How can you tell without knowing the energy budget of that particular boat?

[Fuss]

Originally Posted by Kenomac

Will 250w of solar be enough to top things off? I don't want to purchase more than is necessary, but I only want to do this once and get it right the first time.

There will be some shading at times.

No, it won't top things off, nor will 450w.

I would suggest you stop thinking in terms of topping off. Its not important in your case.

Topping off, is important to people with huge arrays or people who draw very little current during the day. This is not who you are, ignore their advice.
If you keep with the topping off thoughts your boat is going to look horrible. (1 step away from having a washing machine installed on deck)

The 450w solar will do the following for you.....
1 - shorten your generator run times.
2 - allow you to remain more days in anchorages without running the generator.
3 - Depending on how much motoring you do, 450w might lessen the amount of daily generator runs.

If your batteries were not damaged as you wrote, I would suggest an equalisation once a month roughly.

You say you have damaged batteries so there is going to be more resistance making more heat, making charging less efficient. Something that should be fixed.
The first question is to fix the problem that caused the damage, then look at replacing them. Damaged batteries can be dangerous and at the moment you are modifying your charging systems based on parameters that include damaged batteries. This is never good.

[Kenomac]

Fuss,

Should I then be looking more at a 225w array on top of the bimini which will basically be invisible from the water and come in priced at under €2000? Just to help decrease the daily generator run time and provide some redundancy backup.

The 450w array would also be invisible since it'll be mounted to the top of the bimini with zippers. Not able to be seen unless the boat is heeling.

The Solbian SP flex panels are relatively small, with the 225w array costing €2000 and the 450w array coming in at €3000 here in Italy.

[Fuss]

Originally Posted by Kenomac

Fuss,

Should I then be looking more at a 225w array on top of the bimini which will basically be invisible from the water and come in priced at under €2000? Just to help decrease the daily generator run time and provide some redundancy backup.

The 450w array would also be invisible since it'll be mounted to the top of the bimini with zippers. Not able to be seen unless the boat is heeling.

The Solbian SP flex panels are relatively small, with the 225w array costing €2000 and the 450w array coming in at €3000 here in Italy.

Well as its going to be nearly invisible, I would go with the 450w as 450w will make your life much better.

However, I see a big problem with mounting on top of the bimini, the boom is going to make alot of shading which means my calculation of 100ah daily contribution is not going to happen with the boom shading.

I have no experience with panels mounted under the boom but I would guess that my figure of 100ah contribution, if we assume that only one panel is shaded by the boom at a time, will become 60-80ah and maybe worse unless part of your daily activity is keeping the boom shadow off the panels, which is not a nice thing to have to think about each day.

[noelex 77]

Originally Posted by Fuss

I would suggest you stop thinking in terms of topping off. Its not important in your case.

By "topping off" the batteries, I think Ken is referring to achieving 100% SOC or at least close to that.

The biggest factor in determining the life of a lead acid battery is depth of discharge, both the lowest SOC and the time spent at low states of charge. However, there are many other factors that influence lead acid battery life. Periodically getting the batteries to 100% full helps. This is especially important for AGM batteries.

It is difficult for a boat without wind, solar or regular access to shore power to reach 100% SOC. Charging via a generator is usually stopped around 80%. Solar can fill this gap allowing the batteries to get close to 100%. As well, the slower all day charging produced by solar means the batteries lowest SOC will not be as severe. Combined with reduced run time for the generator, there are lots of positive benefits.

However, the real beauty of solar is when the noise, heat, and unreliability of generator can be dispensed with entirely. This is not possible on Ken's boat with his requirements. He needs to be careful that he does not fit a token amount of solar that has little practical impact. On the other hand even a large solar array will not allow him to dispense with the generator, so I think this would also be a mistake in his case.

The 100AHrs @ 24v is realistic in summer in Ken's location for 450W, but much of this power will be taken up using running his fridge/freezers and the other electronics. Will the remainder be enough to raise the SOC from 80% to 100% following a generator run. Without more information It is only a guess, but I think probably yes, although it definitely won't do this year around. A 250w array would still have some practical benefits, but I don't think it will fulfil Ken's aim of regularly achieving 100% SOC.

[daletournier]

Hi Ken, the idea is to get bulk and absorption out the way as early in the day as possible, this allows the rest of the day for the solar to trickle in. This is best for battery health.

Regardless of what your meter says it takes substantial time to get that last 20% of battery capacity fully up, in fact you actually are unlikely to ever get it to 100%.

If you run your generator first up in the morning for an hour or so you will get most of the absorption phase over, depending on battery bank size and charger size.. A huge array really dosent help after that as the batteries are limited as to how much current they will accept at this stage and the solar regulator will limit the amount of current going to the batteries due to soc.

Now if you arent going to run a generator then the bigger the solar array the better, as you will be able to make the most of the low early morning sun once again getting absorption out of the way early in the day. Very rarely to you get to utilize the current generating potential of your solar. The sun in the morning isnt high enough to get max out of your panels and by the time its directly over head your batteries are limited to what you can absorb due to their soc being higher. The idea of a larger array is although you may not see their max potential ,20% of 1000w at 8am is double the output of 20% of 500w, allowing more current to flow to the batteries early.

Without doing the numbers my opinion is this, if you want to limit generator use or not run it at all then add as much solar as possible, imho 750w and up. If your happy to use your generator daily 400w-500w will most likely be fine.

I have 480w and as long as the weather is good we do fine, but I don't have a dc watermaker. We aren't misers with power.

Cheers Dale.

[Kenomac]

To answer a couple of the prior posts, here's the nagging daily anchorage problem I'm looking to solve.

The first day out the batteries are charged to 100% and I have a full 377Ah and usable 188Ah. 50%

Day #2, the generator will only bring the batteries up to 95% despite 3-4hrs of run time on the previous 50Ah charging system.

Day #3, the genset can now only achieve 90%

Day #4 84%

Day #5 82%

Etc. etc. etc.

Until the end of week #2 when I'm eventually down to 75% or so max and using a very narrow battery capacity between 45-50% and 75-80% until I do a long motoring trasit or plug in to shore power.

Will solar solve this?

[Kenomac]

The other nagging problem I'm looking to solve is my wife's resistance to spending money on solar but at the same time complaining about the generator run time.

[StuM]

Originally Posted by daletournier

The sun in the morning isnt high enough to get max out of your panels and by the time its directly over head your batteries are limited to what you can absorb due to their soc being higher.

Don't fall into the mistake of only sizing the solar in terms of what is required to "top off" the batteries from the post generator run SOC.

Even if the batteries can't accept the total output of the panels, the additional output isn't all wasted. It will go into the fridge/freezer, electronics etc that would otherwise be pulling the batteries down during the day once the genset is turned off.

You should size the panels so that their is enough "juice" (that's a technical term used by formal sailors ) going into the batteries to reach 100% SOC in late afternoon plus what is required to meet your daytime energy needs.

[Kenomac]

Stu,

But at the same time, I don't want to turn the boat into a floating solar farm.

[Sailmonkey]

Originally Posted by Kenomac

Stu,

But at the same time, I don't want to turn the boat into a floating solar farm.

It's an easy thing then. Put as many panels onboard as you can without altering the lines of the boat. The more the better, but even less will offset consumption and reduce gen time.

How many AH do you consume during the day after running the generator?

[daletournier]

Originally Posted by StuM

Don't fall into the mistake of only sizing the solar in terms of what is required to "top off" the batteries from the post generator run SOC.

Even if the batteries can't accept the total output of the panels, the additional output isn't all wasted. It will go into the fridge/freezer, electronics etc that would otherwise be pulling the batteries down during the day once the genset is turned off.

You should size the panels so that their is enough "juice" (that's a technical term used by formal sailors ) going into the batteries to reach 100% SOC in late afternoon plus what is required to meet your daytime energy needs.

Stu , it was a very general response, I know you like exact.
400w array theoretically puts out 33amps......my point is 400-500w (without doing the numbers) most likely will top up his batteries ( assuming he runs his generator in the morning) and run his fridge etc. If it dosent he can add more later.

As I said I get by in 480w mostly without using a generator on a 47 foot boat. Im probably going to add 200w more for those not so sunny days.

Ken if you add solar and it dosent seem enough you can add more later. Buy a regulator that enables you to add more later or you can just fit an additional one at the time. I run two regulators now. Its not that hard. Start with 400w and see how you go. If you run the genny in the morning I think you'll be more than fine.

[Kenomac]

Dale,

I'm beginning to think along the lines of what you said. Maybe adding 225w this season then expanding next to 450w. Looks like with installation included, the Solbian quote for 450w just increased to €3800.

I don't mind paying an extra €1000 to have it done right and invisible.

[Kenomac]

Originally Posted by Sailmonkey

It's an easy thing then. Put as many panels onboard as you can without altering the lines of the boat. The more the better, but even less will offset consumption and reduce gen time.

How many AH do you consume during the day after running the generator?

My best guess is 80-100Ah during the day. I'll turn off the shore power first thing tomorrow morning after breakfast and have an answer tomorrow night. I'll have a six hour number for you in about... six hours.