Solar question

[Wdeertz]

Ok I've read the forum and Nigel Calder's book and am about to bite the bullet and add solar power. The boat came with 3 100W panels on the Bimini when I purchased it 2 years ago but I removed these panels as I didn't like not being able to close the Bimini top in high winds. My current battery bank is 380Ahr and my daily usage is generally about 200Ahr. While at anchor we generally run the generator for 2 hrs for microwave, water heater and juicing the batteries with a 60amp battery charger. My goal is not to totally rely on solar for my power needs but reduce my generator run time.

My thought is if I start with 380Ahr and use 200Ahr I'll be at 180Ahr in the morning at which time I'll run the generator for 2 hrs (in the morning before peak sun intensity) at bulk charge of about 120Ahr so this will get me to 300Ahr in the battery. Looking at my limited spacing I think I can accommodate 2 x 175W panels and connect them to each of their own MPPT controller to maximize output.

Will 350W of solar be sufficient to top the flooded battery banks to 100% on a typical sunny day? On cloudy days my plan would be to only bulk charge up to 85% and then ensure I get back to 100% on the next sunny day. I spend the majority of my time in Florida so usually we never go more than 3 days without some decent sun. Appreciate any comments from the experts, thanks.

 

[DDW]

My experience with solar panels is that in a sunny climate you get about 50-60% of the rated power for about 6 hours a day as a good rule of thumb. You might do a little better in Florida if you can guarantee no shading. There are several reasons it is this low, one is that the ratings are done at "standard" - which is to say unrealistic - conditions. For example with the panel at 77 deg. If there is any sun the panel will be way too hot to touch, and that lowers output significantly. So I'd expect something like 80 AH from your two 175W panels (350W/14.4V charging voltage x 6 hours x 50% = 72 AH). Also you will be using some power during the day and that reduces what goes into the batteries. On my sailboat with 450W I get around 80AH, maybe 100 on a good day in Florida (but it suffers more from shading problems).

If you are going to continue to run your genset daily, you might consider replacing your AC charger. A good quality 380AH battery bank, if discharged 50%, will accept at least 150A for awhile, and will load your genset a bit more which is good. You would get much more charge for the genset run, and the solar would have less work to do.

 

[Ka_sea_ta]

If you have Lead acid batteries you might consider increasing the size of your battery bank by about 100 amp hours or more if you have room. LA batts don't like to be discharged less then 50% of their rated capacity.... I have found that solar is more geared toward the absorption / float charging cycles then bulk....

 

[Wdeertz]

Thanks for the inputs. Given my configuration its not really feasible for me to add any more capacity. I have 2 8D batteries and that's about all the space I have. I was thinking I could continue with the 2 8D flooded batteries, add the solar knowing I may not get full every day or run the generator a little more than 2 hrs per day. Or as suggested add additional charging capacity. I added a dedicated pro mariner 12v 60amp charger last year and that was the largest size they offered. This was an upgrade as the boat only had a 40amp charger shared amongst 3 banks (house, windlass/genset, and starter). It seems all the 100+ amp chargers are included with inverters and I don't really need an inverter. As a side question do you know if I can get another 60 amp battery charger and parallel them together for a total 120 amps of charging capacity?

I'd like to add carbon foam batteries which would allow me to run continually in the 20-85% range of SOC without worrying about sulfication. I could forgo the solar in this case and put the money towards upgraded batteries. Only problem is when I looked at the firefly the battery dimensions offered wouldn't fit in my existing 8D battery boxes. This is going on a tangent from my original question but are there any other manufacturers of carbon foam batteries that offer various sizes?

So many things to consider.

 

[Ventana]

Depending on the dimensions of your battery space, you may be able to fit six 6v golf cart batteries in the space of two 8d batteries. May be a cheaper option than the Firefly’s and would increase your capacity quite a bit.

 

[Comodave]

I would look into the 6 volt batteries too. Much easier to put in and take out. Also 8Ds generally are not deep cycle batteries.

 

[mvweebles]

For sizing, a very standard rule is 5x the panel rating for average daily power generation. Assumes no shading of course. More in summer, less in winter. Your two panels will produce around 1750 watts per day, or around 130ah (13.2v).

Your energy consumption is probably fairly constant with refrigeration consuming almost half. At 200 ah, you are probably consuming around 10a during the day when you're awake, maybe 6a at night. During daylight hours you will be effectively running off solar while putting excess into your batteries.

If you run your generator in the morning to top off (or probably just close to topped off), you should remain more or less 100% charged throughout the day - probably until 3pm - 4pm when your usage will become higher than the diminishing solar power generation.

In the end, solar will provide around half your 200 ah energy budget - some will get wasted as the batteries will be full and cannot accept more charging because the batteries were topped off in the morning. If you run the generator late in evening, you may recover more solar. Your batteries therefore only need to provide 100-125ah of your budget - size of your battery bank (380 ah) is fine. As a matter of fact, anything larger is a waste though it would help on cloudy days.

The solar panels will reduce your generator run time, but the biggest effect will be battery health. Your batteries should rarely see 60% depth of discharge whereas you are now regularly running them down to 40%. Also, the solar setup will be more likely to get you charged to 100% than a charger running off a generator - your charge will go into float mode and will take hours to top off the final 5%-10% of charge. The solar energy is pretty good in this mode.

To Comodave"s point, not sure how young or strong you are, but 8D batteries went past me 15 years ago. 6v golf carts are better. If you plan to keep your boat, I personally believe there's a business case for lithium, but that's another thread

Good luck

Peter

 

[mvweebles]

Also, to your question on dual chargers. If your chargers are 3 or 4 stage chargers, I would think putting two together would cause confusion. The higher voltage from one would trick the other into float mode, and vice versa. You may want to call the OEM to verify. The old school ferro resonant chargers would be more likely to work in a gang, but I'm not sure on that either.

Question for OP: have you used the 60 amp charger at anchor yet? Assuming a 3 stage, wonder if you see a material difference in generator run time? I would think the 60a would get to float stage much faster that the 40a, but since there may not be a huge difference in the amps at float, curious to know if the 50% increase in charge rating results in anywhere close to 50% reduction in charge time.

Regardless, I think you're on the right track with solar vs focusing solely on batteries, though the system needs to be viewed as a whole. I think you'll be pretty happy with the solar system once installed.

 

[DavidM]

There is lots of information in the Library section of this forum on solar panel installation and upgrading from 8D batteries.

David

 

[firehoser75]

Wdeertz,
Some good advice so far. I will add my FREE suggestions, worth every penny, but I suggest verifying anything I say.
First, look very carefully at fixing your confessed issue of regularly running your battery bank down below 50% capacity and probably operating them often in a partial state of charge (PSOC). This will greatly reduce battery life and result in early replacement meaning $$ wasted. Fireflies are one option that will tolerate PSOC. They might require other changes as well, especially the equipment needed to properly recharge them. Not sure about that, but worth investigating.
If not Fireflies, then truly investigate moving to 6V golf cart batteries. Flooded are least expensive, but AGM may be a good choice if access to add water would be difficult. If you could "squeeze in" 6 golf carts your bank size would work much better for you. You may need new battery boxes, not a big deal in the scope of this project.
You need more charging ability than a single 60 amp (supplying 3 banks - 20 amps per bank?). If you don't want an inverter, then add another 60 amp (or larger) charger but split the chargers to separate banks. For sure use a dedicated charger for just the house bank, and use the second charger (most offer multi bank charging) with a separate leg for the other 2 banks. Also, you may be able to find another brand of charger with a higher output. I would suggest at least 100 amps for the house bank.
Solar. I have 570 watts of solar, and operate much further north than you. Most days, I reach 100% battery without running the generator. My main draws are fridge, separate portable freezer, lights, AIS anchor alarm, some TV, and misc. small draws. When it is very cloudy all day or worse yet foggy until late afternoon, my solar does not top up, but does meet the ongoing consumption during the day. My battery bank is 6 golf carts( 640 amp/hr). As far as the solar goes, I have never heard anyone say they put too much on. Do not go cheap on your controller. Get MPPT!!
DDW gave a "rule of thumb" for what you can expect from solar. It is a very good estimate and can be used as a starting point.

Hope at least some of that proves useful,

 

[Wdeertz]

Depending on the dimensions of your battery space, you may be able to fit six 6v golf cart batteries in the space of two 8d batteries. May be a cheaper option than the Firefly’s and would increase your capacity quite a bit.

Thanks, my 2 8D batteries are on opposite sides in the engine room so if I put 3 6v batteries in each box it wouldn't be easy to wire the 3rd battery in each box in series. Looking at the Trojan website I can get 4 6v batteries between the two battery boxes which would get me 450Ahr of capacity so an 18% or even 480Ahr if I go with the T-125 or a 26% increase.

 

[Wdeertz]

Question for OP: have you used the 60 amp charger at anchor yet? Assuming a 3 stage, wonder if you see a material difference in generator run time? I would think the 60a would get to float stage much faster that the 40a, but since there may not be a huge difference in the amps at float, curious to know if the 50% increase in charge rating results in anywhere close to 50% reduction in charge time.

Regardless, I think you're on the right track with solar vs focusing solely on batteries, though the system needs to be viewed as a whole. I think you'll be pretty happy with the solar system once installed.

Both the 40amp and 60amp chargers are 3 stage "smart" chargers. With the original 40 amp charger it was split between 3 different battery banks (starter, windlass/genset start, and house). Granted the starter and windlass batteries were charged pretty quickly giving full capacity to the house I did notice a significant reduction in bulk charge time between the 40amp and 60amp charger. In either case there isn't much you can do about absorption time which is why the solar panels would be ideal.

 

[Wdeertz]

Thanks for all the inputs. A lot of valuable information being shared. I acknowledge the 8D batteries aren't ideal but that's what the PO installed so I'm stuck with them until replacement. While inadequate they meet my current needs, at least barely. I see my choices between three broad options. Putting cost aside Lithium is not an option for me as there is no practical option for storage outside the engine room and the heat would quickly proof this expensive endeavor worthless.

As such I see my broad choices as follows:

1) status quo - continue with the inadequate 8D batteries and run the generator for 2-3 hrs in the morning and 2-3 hrs in the evening. Putting aside generator maintenance cost the operating cost are minor at 0.5gph and diesel at a little over $2/gallon. The accountant in me likes this option but not sure it will keep my wife happy and I'm not sure how to factor in the cost of a potential divorce <g>. So say $7.50/day for fuel cost at about 60 days/yr anchoring or $450/yr. This ignores the intangible cost of the extra noise.

2) Replace 8D batteries with 6V golf cart batteries to increase house bank capacity. (about $1k for 450Ahr of capacity). Add 350W solar (about $1k with all hardware and wiring). I could do the solar project first and continue with my 8D batteries until they prove totally inadequate but in total this option is around $2k in total. Generator run time say 2hr/day $150/yr in fuel cost.

3) Replace 8D batteries with 464Ahr of Firefly or similar manufacture (are there other mfg that produce carbon foam batteries?) and operate for long periods in PSOC of 20-85%. (say about $2500 in total cost) With this option I see little incremental advantage to adding solar. Generally we'll be at a slip at least once every 30 days so can plug in to top up the batteries to 100% which is suggested on their website. With this option I could potentially add another charger or upgrade to a larger charger but this would add say another $1k to the project. Generator run time 2-3hrs/day or about $225/yr in fuel cost.

I recognize this is a crude analysis but is the high level way I see my options. I'm leaning towards option #3 but am concerned that the hype on these batteries won't live up to expectations. Any all and feedback appreciated. I recognize that my original question has taken a tangent but I guess that's the nature of these sorts of matter.

 

[firehoser75]

A couple of years ago, I attended a talk given by Nigel Calder at the Seattle Yacht Club and he talked about some testing of the Firefly battery he had conducted. He stated that he "abused them as best he could" for a year (very deep discharges coupled with PSOC operation for long periods), and then tested them and found them to perform (test) as if they were new. He stated that this result surprised him pleasantly and based on his results they looked very promising. However, he also said that being as they are so new, the jury is still out on their longer overall lifespan claims.
If they meet or come close to meeting their claims, they may turn out to be the best value in marine batteries out there???? Higher initial cost, but lower overall cost due to the longer lifetime??? They haven't been in use long enough to say 100% for sure, but I have not heard complaints about early failures either.

 

[FF]

Only solar (or the dock) is on long enough to bring most batts from 85% to 100% .

However there is a plan B.

"Your energy consumption is probably fairly constant with refrigeration consuming almost half."

A better fridge system Sun Frost or similar might cut the power use by 50% .

Most RV or "boat" fridges are created to have maximum internal dimensions with insulation ability a distant second.

The alt energy folks are willing to trade volume for efficiency , a search there might be worth the effort.

 

[Wdeertz]

A couple of years ago, I attended a talk given by Nigel Calder at the Seattle Yacht Club and he talked about some testing of the Firefly battery he had conducted. He stated that he "abused them as best he could" for a year (very deep discharges coupled with PSOC operation for long periods), and then tested them and found them to perform (test) as if they were new. He stated that this result surprised him pleasantly and based on his results they looked very promising. However, he also said that being as they are so new, the jury is still out on their longer overall lifespan claims.
If they meet or come close to meeting their claims, they may turn out to be the best value in marine batteries out there???? Higher initial cost, but lower overall cost due to the longer lifetime??? They haven't been in use long enough to say 100% for sure, but I have not heard complaints about early failures either.

Thanks for the info. Agree if the batteries live up to half of their claimed properties they are a game changer. To be able to operate in a partial state of charge over a long period is key for me. I just wish they offered the firefly in a few different battery dimensions.

 

[Wdeertz]

Only solar (or the dock) is on long enough to bring most batts from 85% to 100% .

However there is a plan B.

"Your energy consumption is probably fairly constant with refrigeration consuming almost half."

A better fridge system Sun Frost or similar might cut the power use by 50% .

Most RV or "boat" fridges are created to have maximum internal dimensions with insulation ability a distant second.

The alt energy folks are willing to trade volume for efficiency , a search there might be worth the effort.

You bring up a valid point. I've measured my loads and between my primary and secondary refrigerator/freezers they are easily 50% of my energy usage. I checked out the Sun Frost website and the model RF12 is similar in size to what I currently have and the energy usage was about on par with my current usage. While all in favor of energy efficiently I'm not sure there is enough to be gained to make up my shortfall.

 

[PMF1984]

Regarding the batteries, the T-125 gives you more punch. Since you have two slots for batteries, is it possible to hook 3 up parallel on each side, then join them?

Whatever you do, hot water heater will require genset.

 

[Wdeertz]

Regarding the batteries, the T-125 gives you more punch. Since you have two slots for batteries, is it possible to hook 3 up parallel on each side, then join them?

Whatever you do, hot water heater will require genset.

Duh, do I feel stupid. I had a mental block thinking 2 6V batteries needed to be wired in parallel and then these subsequently wired in parallel. But as you pointed out there is no logical reason why the 3 6V batteries can't be wired in parallel and then the two tied together in series. I went back and looked at the various dimensions of the Trojan 6V batteries and I couldn't find a size that would allow me to fit 3 inside a 8D battery box measuring 21"x11.8X10.3". If I could get 6 6v golf cart batteries as my house bank that would go a long way to solving my power needs.

 

[firehoser75]

New or different battery boxes??? Unless they are "shoe horned" into a tight spot with absolutely no room for a different configuration, then you may have no options. Otherwise, new boxes They would probably be the least expensive part of a new battery project.

 

[DDW]

Firefly is the only manufacturer of carbon foam batteries. They do make a 2/4V battery which offers a different shape to consider. Reports on them are very good, however they seem to be the highest cost in AH delivered over their life of any of the available technologies (flooded, AGM, lithium).

The Lifeline 6V footprint is 10.28 x 7.06. 3 might fit in your 8D boxes? If they do and you have height, you could use the 6CT or L16 version, same foot print but taller, and higher capacity. Being AGM, they will not outgas like the flooded ones so the lid may not be necessary. Both Victron and Mastervolt make 100A chargers

 

[Wdeertz]

New or different battery boxes??? Unless they are "shoe horned" into a tight spot with absolutely no room for a different configuration, then you may have no options. Otherwise, new boxes They would probably be the least expensive part of a new battery project.

Not worried about the cost of ordering new battery boxes, its just that in my current configuration the manufacturer built in fiberglass humps (can't think of a better word to describe) that will hold the 8D battery box, anything larger would require a rework and this would be a PITA.

 

[Barrie]

Hello: Solar is a life style change if you can do it both physically and mentally.
We had no generator to start with and no room to put it on our 35 footer. We started with 6 6volt golf cart batteries and then installed 520 watts of solar in two panels sitting on their own rack above the rear Bimini. Total cost $1000.00 Cdn dollars. Result, we run the fridge, ice maker, lights, head, toaster, coffee maker, radio and anything else 12 volt. No air conditioning or hot water for shower. Batteries never go below 80% and by 11am we are up to full power.

But the nice thing................IT IS QUIET AT NIGHT WHILE AT ANCHOR!

Love Barrie

 

[Wdeertz]

Hello: Solar is a life style change if you can do it both physically and mentally.
We had no generator to start with and no room to put it on our 35 footer. We started with 6 6volt golf cart batteries and then installed 520 watts of solar in two panels sitting on their own rack above the rear Bimini. Total cost $1000.00 Cdn dollars. Result, we run the fridge, ice maker, lights, head, toaster, coffee maker, radio and anything else 12 volt. No air conditioning or hot water for shower. Batteries never go below 80% and by 11am we are up to full power.

But the nice thing................IT IS QUIET AT NIGHT WHILE AT ANCHOR!

Love Barrie

Thanks for the input. I broke down and ordered 350w of solar to lessen my generator run time. Would be nice to add more but just don’t have the space without sacrificing the boat look. Hopefully the 350w will handle my absorption.