Solar Effectiveness - Great Lakes

[ramblinrod]

Originally Posted by admiralslater

I will explain Ramblinrod. Our Pdq 36 was built with the usual comprises speed versus comfort etc. We chose speed, consequently many decisions went the direction of weight reduction. Including the charge system of 150 watts of solar going through an mppt to two 6 volt Trojans. We run the fridge from launch till haulout for about 100 amps in 24 hours. This of course is a poor set up. After learning more about batteries because of the Outremer I realized that an adjustment was needed. Since the LA will not accept high amps for very long straight solar was not going to work in this situation. However my thinking is that if I use batteries that c*n accept a big charge quickly I will be better off. I am thinking of either lifepo or the Firefly Carbon plate batteries. I installed 5 of the latter on the Outremer. The ability to recover from the PSOC that I will be operating in gives me the flexibility to keep the solar as it is. Putting on larger panels is doable but I would like to experiment with the other stuff first. My present batteries are shot and my 20 amp xantrex charger works fine but is to small and can't be programmed to meet modern battery profiles.

I don't understand this comment.

"Since the LA will not accept high amps for very long straight solar was not going to work in this situation."

What do you mean?

Here is my understanding of your system.

1. 100A-hr per day consumption.
2. 2 x 6Vdc golf cart batteries, 220 A-hrs of total capacity, 110 A-hrs of usable capacity (with a 50-100% SOC charge cycle).
3. 20 A shore power charging system. (A little light but acceptable, batteries can be charged from 50% to 100% in about 8 hours.)
4. 150W solar with MPPT, producing about 37 A-hrs on a sunny day.
5. Negligible alternator capacity.

So you have 3 issues:

1. Too little battery reserve capacity. (You have no reserve if you have no sun to charge them, and will have to go to shore power on any non sunny day.)

2. Too little solar charging capacity. (With no alternator, when on the hook, your solar is only capable of replenishing about 1/3 of what you are discharging, so you will discharge your batteries to deeply, even in bright sun, on the second day.)

3, Whether changing to LiFePo4s, or adding more golf cart batteries, you will need a higher output shore power charger.

To improve your reserve capacity you could:

a) change to LiFePO4s, with a similar total capacity, you will increase your usable capacity to ~ 170 A-hrs (20-100% SOC charge cycle). (About 1.5 day reserve).

b) add 2 more 6 Vdc golf cart batteries for 220 A-hrs usable capacity (50-100% SOC) or a 2 day reserve.
(This would add about 120 lbs.)

But with either option, you can still only charge 37 A-hrs a day with your current solar charger.

You will need about 400W of solar to recharge your batteries every day while at anchor. If you go with option option A) your can only tolerate 1.5 days of no sun. If you go with option B) you can tolerate 2 days of no sun.

Option B will be a fraction of the cost of option A). If you go with 4 x golf cart batteries, you will need to step your shore power charger up to 40 A.

I know cats are more sensitive to weight, but suspect you wouldn't notice any difference with the additional golf cart batteries (120 lbs) and solar panel weight will be close to a wash.

If you did notice a significant difference then you would need to go the marina every morning for pump-out and may as well hook up to shore power while there. ;-)

[ramblinrod]

Originally Posted by ramblinrod

I don't understand this comment.

"Since the LA will not accept high amps for very long straight solar was not going to work in this situation."

What do you mean?

Here is my understanding of your system.

1. 100A-hr per day consumption.
2. 2 x 6Vdc golf cart batteries, 220 A-hrs of total capacity, 110 A-hrs of usable capacity (with a 50-100% SOC charge cycle).
3. 20 A shore power charging system. (A little light but acceptable, batteries can be charged from 50% to 100% in about 8 hours.)
4. 150W solar with MPPT, producing about 37 A-hrs on a sunny day.
5. Negligible alternator capacity.

So you have 3 issues:

1. Too little battery reserve capacity. (You have no reserve if you have no sun to charge them, and will have to go to shore power on any non sunny day.)

2. Too little solar charging capacity. (With no alternator, when on the hook, your solar is only capable of replenishing about 1/3 of what you are discharging, so you will discharge your batteries to deeply, even in bright sun, on the second day.)

3, Whether changing to LiFePo4s, or adding more golf cart batteries, you will need a higher output shore power charger.

To improve your reserve capacity you could:

a) change to LiFePO4s, with a similar total capacity, you will increase your usable capacity to ~ 170 A-hrs (20-100% SOC charge cycle). (About 1.5 day reserve).

b) add 2 more 6 Vdc golf cart batteries for 220 A-hrs usable capacity (50-100% SOC) or a 2 day reserve.
(This would add about 120 lbs.)

But with either option, you can still only charge 37 A-hrs a day with your current solar charger.

You will need about 400W of solar to recharge your batteries every day while at anchor. If you go with option option A) your can only tolerate 1.5 days of no sun. If you go with option B) you can tolerate 2 days of no sun.

Option B will be a fraction of the cost of option A). If you go with 4 x golf cart batteries, you will need to step your shore power charger up to 40 A.

I know cats are more sensitive to weight, but suspect you wouldn't notice any difference with the additional golf cart batteries (120 lbs) and solar panel weight will be close to a wash.

If you did notice a significant difference then you would need to go the marina every morning for pump-out and may as well hook up to shore power while there. ;-)

BTW, sorting out the charging systems on your PDQ36 and Outremer, is definitely a first world problem I would love to have. ;-)

[ramblinrod]

Originally Posted by admiralslater

I will explain Ramblinrod. Our Pdq 36 was built with the usual comprises speed versus comfort etc. We chose speed, consequently many decisions went the direction of weight reduction. Including the charge system of 150 watts of solar going through an mppt to two 6 volt Trojans.

Sorry to ramble on, but I am RamblinRod after all. ;-)

One more thing, I would never recommend 2 x 6Vdc golf cart batteries as a house bank. If one battery goes down, it renders both unusable because vessel systems can't operate on only 6 Vdc.

Now you are limited to a running house loads off the start battery, until the defective 6Vdc battery can be replaced (and it is advisable to replace both if same age, as they should be).

Conversely, if you had 2 x 12Vdc Grp 27s, you would have almost the same capacity normally, but if one went down, you could just disconnect it, and still use the other one, albeit reducing capacity in half, WITHOUT using your start battery for house loads, until replacement is effected.

I'm not a big fan of 4 x 6Vdc instead of 4 x 12Vdc batteries for similar reason; with the former, if one goes down you lose two, with the latter, if one goes down, you lose just one, until repairs are effected.

I normally only recommend 6Vdc batteries when one gets up to a 6 battery house bank, as then, the impact on capacity is reduced sufficiently if one battery goes down and you lose 2.

I am skeptical that golf cart batteries are so much better than 12 Vdc batteries as so many claim. My belief is that treated properly, either will last about 5-8 years before requiring replacement.

I believe the perception that golf cart batteries last longer, is because when someone with 12 Vdc batteries kills them, and goes to the trouble to investigate golf cart batteries, at the same time they learn more about batteries, how to treat them better, and how to make them last longer. (ie. if they just replaced the 12 Vdc batteries and treated them with the proper care, they would last every bit as long as 6Vdc batteries, and wouldn't require new boxes and cabling.)

A quality golf cart battery and a quality Grp 27, has the same volume, weight, and close to the same W-hr capacity. Though the golf cart battery solution, apples to apples, has about 10% more capacity, the disadvantage of the capacity loss if one fails, and the installation change over cost, pretty much counters the benefit to change. If one is worried about the 10% W-hr loss, they can simply go up to Grp 31s.

The argument that golf cart batteries thicker plates and deeper plate shedding reservoir makes them better, needs to be proven. If 12Vdc batteries last the same in a real world application comparison, those are just design differences with no real world benefits. (PS, the deeper reservoir also makes them taller so they won't fit in Grp 27 boxes due to height. 4 x 6Vdc golf cart battery boxes = C$120 including tax, (if one can find them, whereas marine stores carry 12 Vdc battery boxes by the dozen) and the perfectly good (maybe) 12Vdc battery boxes changed out will likely go to the red bin.

Lastly, I keep hearing that in some cruising grounds, replacement 6 Vdc batteries are hard to find, whereas 12Vdc batteries are available anywhere. (This problem is even worse for the more exotic batteries by the way, (AGM, Gel, LiFePo4, what have you).

There is an advantage to using batteries that are used in cars; they are available everywhere. PS, a quality marine 12Vdc grp 27 is constructed differently than a car starting battery. A cheap tires store "marine battery" is most likely a car starting battery relabelled. Same with cheap 6 Vdc tractor starting batteries from the farm store (or relabelled); 50 year old technology. To compare apples to apples, compare the 6 Vdc and 12 Vdc models of the SAME manufacturer. Very little difference in longevity.

Comparing a Trojan 6Vdc to an Interstate 12 Vdc, is simply not a fair comparison.

Compare Trojan to Trojan, and you won't see a real improvement in life expectancy.

Compare a Rolls (formerly Surrette) 12Vdc to a Trojan 6 Vdc and see what happens (longevity as well as pocket book, but, that's kinda the point.) ;-)

[admiralslater]

Originally Posted by ramblinrod

BTW, sorting out the charging systems on your PDQ36 and Outremer, is definitely a first world problem I would love to have. ;-)

Amen to that ,
Generally I agree with your understanding of my issue. Today I purchased a 50amp sterling smart charger and a Dongle for my victron mppt controller. I do get to the dock once a week if not more so my plan is to augment my poorly balanced solar/battery system with much a more substantial shore powered abilities and use the anti solation qualities of the Fire fly batteries to keep me going. We shall see how it goes.
As for the holding tank only my wife and niece use that .
I am more sensitive to weight than the boat is .When we launched 13 years ago the scale on the crane read about 8000 lbs .It read the same this fall.
13 years ago I weighed 205 now it is 225 .
I can increase the capacity of both batteries and panels of course but we shall see.

[admiralslater]

In the picture you can see what a tidey installation the panels are