PSOC vs. bank size vs. solar

[Adelie]

Originally Posted by OldManMirage

A question to those who have knowledge.

Concerning the PSOC issue, is it better to have a smaller bank and more solar or vice versa ?

Let's use a 220amp bank comprised of 2 6V 220AH batteries as an example. FLA or AGM, not lithiums. What would you want for solar ?

I know it would also depend on load so let's use the 50% capacity daily. As if we were cruising with a frig system, a couple of fans and other such things an average 30 footer would have.

AGMs really, really don’t like PSoC.
If you have decent access and think you can be good about checking water in them once every 1-2mo get FLAs. Golfcart batteries for preference since they will have better odds of really being deep cycle rather than hybrid or starter batteries with a “Deep Cycle” sticker plastered on on it.
If you don’t have access or forget to service regularly then get Gels.

220Ahr discharged to 50% daily means you are using 110Ahr per day.

Battery capacity vs panel nameplate wattage is a question whose answer depends on your fossil fuel charging sources and your willingness to use them.

If you have an inboard I assume it has a reasonably sized alternator, 40-60amps. That would be sufficient for a 200-400Ahr system discharged to 50%.

If you get a generator you will also need to get a charger to run off the generator’s AC power. Get at least a 60A/12v charger.

If you expect an overcast day run the engine or generator first thing in the morning and watch the voltage. When voltage gets to a bit over 14.0v the battery is up around 70% or so charge and will be voltage limited and amps will taper off. That’s the point where you should shut the engine or generator off and let the solar do the long slow charge to full.

Rule thumb in tropical and sub-tropical areas for panels when using MPPT controller is 1/3 of nameplate capacity in Watts is average daily output in Ahr. For PWM controller s1/4.

Using an MPPT controllers for 330W of panels will yield about 110Ahr/d.

Best practice is to use a small controller on each panel. This does 2 things;
A. Redundancy, a controller goes out, run 2 panels thru a single controller until you can replace the dead one. If you have one big controller and it dies you get nothing from the panels.
B. Shade resistance. If panels are wired together going to the controller, shade on one will drag output from both down.

If you have enough panels to provide 110Ahr per day the you need to run alternative charging source in the morning any day anticipate having a shortfall of sun. You shouldn’t wait to the end of the day to run the generator/main engine alternator because it will sit there for hours at low output because the batteries are already up to the absorption stage.

It is better to go a bit over overcapacity on both the battery and panels rather than a lot over capacity on one.
Let’s say you get 330Ahr of batteries and 500W of panels, you are 50% over on both.
330Ahr of batteries means you have 1.5d worth of power with no solar output at all.
With 500W of panels a fairly overcast day will result in 1/2 the normal output. Since you are overcapacity on watts that’s 75% of what you are using. Between the panel and battery overcapacity you are looking at about 2d of regular use and sometime on day 3 you get to 50% and need to run the generator.
A really dark day with lots of rain means that you will get 20-25% of normal output and battery hits 50% sometime late day 2 or early day 3.

If you go 440Ahr on battery capacity and have 330W of panels you have 2 full days capacity with no solar input and around 3 or so with some input but anycloudy day means having to run the generator to get the battery back to full, the panels will never catch up unless you conserve for several days.

If you get 220Ahr battery and 4x panel then you would they you would be making enough even on really low production days to keep up but that’s 1320W of panels and you need to find mounting space for all of that and pay for the mounting.

[OldManMirage]

Originally Posted by PaulCrawhorn

A good alternator setup with external adjustable VR will be what saves you on Extended cruises off grid.

Big investment, but then you don't need to mess up your boat's lines with too many panels.

The best battery value by far is Duracell (actually Deka/East Penn) FLA deep cycle golf cart batteries, 2x6V, around $200 per 200+AH @12V pair from BatteriesPlus or Sam's Club.

NAPA relabels it here: https://www.napaonline.com/en/p/NBP8144

Deka self-labeled also sold at Lowes.

If you don't worry too much about PSOC, and need to replace them every 2-3 years, is that so bad?

I agree, replacing every few years at that price point is not so bad. And who knows, maybe I would get more. At least I know they would be easily available. Golf carts are everywhere !

So my engine is 20hp Yanmar. Can someone suggest a reasonable upgrade for the alternator ? One with an external control ? I believe I'm somewhat limited by a single belt system, and I'd prefer to keep it the same.

[OldManMirage]

I can easily have a 220amp bank and somewhere between 300 and 400 watts of solar. I don't need to modify anything really, just upgrade my 2 100watt panels (which I want to do anyway) and change my batteries. I also plan to add one Group 31 batt as an engine start/backup using a b2b charger coming off the house bank, and I see no reason it can't be a deep cycle battery. Then I'll upgrade the alternator and be prepared to use it when needed.

Now I just have to figure out what type of frig unit to get, LOL.

[noelex 77]

In the days before solar, it was common to routinely charge the lead acid house battery between 50-80 %. Charging above 80% or perhaps 85% was not practical due to the diminished charging rate.

100% SOC was rare for a cruising boat. PSOC was normal.

Typical battery life for simple flooded lead acid was around 5-6 years.

We seem to have gone backwards from these times.

AGM batteries seem to be particularly sensitive to PSOC problems I wonder why this technology is so popular?

[OldManMirage]

Lol, you may be right !

I'm looking at Sam's Club at the moment. Can anyone tell me if this Duracell...

https://www.samsclub.com/p/duracell-...=plp_product_3

...is actually better than this Duracell ?

https://www.samsclub.com/p/duracell-...=plp_product_1

The first one is 230AH vs. 215Ah but in reality is there a difference ? For the price difference I would certainly pay the $38 for the better battery.

[ranger58sb]

Originally Posted by noelex 77

AGM batteries seem to be particularly sensitive to PSOC problems I wonder why this technology is so popular?

You know this...

Ease of maintenance would be one reason. Extending that, batteries can be stuffed into spaces where access is more difficult... when getting there every month or two isn't as important.

And then bazillions of boats are plugged into shore power at the end of the day, or at least at the end of the weekend.

Probably several other reasons, too, not necessarily applicable to the unique audience in this and similar forums.

-Chris

[rslifkin]

Originally Posted by noelex 77

AGM batteries seem to be particularly sensitive to PSOC problems I wonder why this technology is so popular?

I've run AGMs over FLA (or gel) for a couple of reasons. My current house bank is L16s, so gel is out as a choice (haven't found any in that size, so I'd have to modify things to accomodate a bigger footprint). AGMs typically do better with large bursts of power draw for a given size bank. I run the windlass off the house bank, so for that and other reasons, that's an advantage.

But the big one is that the area my house batteries are located would require me to custom build a suitable tray / box setup for FLA battery containment (would be a challenge to build something suitable without making it hard to get batteries in/out) and I'd need to add more ventilation to that space for FLA batteries as well (it's got some now, but not enough that I'd be happy with FLA off-gassing).

So instead I just added a bunch of solar to help me minimize the days where the batteries don't get topped off. If you can fit enough solar, it's not too hard to avoid PSOC-ing an AGM to death (provided it's a good quality battery).

[PaulCrawhorn]

You can stick to single belt, but then 60-70A may be your ceiling output.

Going near 100A need to go serpentine Vee belts and yes gets expensive.

Maybe not worth it until you go LFP then, just see how you go first. Swap out the VR or use a DCDC to get more precise control over the charge profile.

...

FLA and GEL are just as susceptible to PSOC abuse.

They just last longer, and FLA has greater tolerances on other factors.

...

Those two Deka are equivalent quality, just a slightly different size.

[Stu Jackson]

Originally Posted by OldManMirage

.....

So my engine is 20hp Yanmar. Can someone suggest a reasonable upgrade for the alternator ? One with an external control ? I believe I'm somewhat limited by a single belt system, and I'd prefer to keep it the same.

Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. Any battery at any state of charge simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

http://forums.sbo.sailboatowners.com...d.php?t=125392

and these, too:

http://www.cruisersforum.com/forums/...on-125843.html


http://www.cruisersforum.com/forums/...or-142083.html


*****************************


Next you'll be asking how to wire this all up. You mentioned a b2b but that may not be necessary, any vsr like a Yandina combiner will do just fine.


You might be interested in the info in this link:


Electrical Systems 101 http://c34.org/bbs/index.php/topic,5977.0.html

[kmacdonald]

Originally Posted by noelex 77

In the days before solar, it was common to routinely charge the lead acid house battery between 50-80 %. Charging above 80% or perhaps 85% was not practical due to the diminished charging rate.

100% SOC was rare for a cruising boat. PSOC was normal.

Typical battery life for simple flooded lead acid was around 5-6 years.

We seem to have gone backwards from these times.

AGM batteries seem to be particularly sensitive to PSOC problems I wonder why this technology is so popular?

That is sooooooo true. People didn't really know they were doing that but they were. Expensive AGM created the need for exotic charging systems and hence profits.⁴

[Adelie]

Originally Posted by noelex 77

….

AGM batteries seem to be particularly sensitive to PSOC problems I wonder why this technology is so popular?

Marketing.

[Adelie]

Originally Posted by PaulCrawhorn

,,,,
...

FLA and GEL are just as susceptible to PSOC abuse.

….

Yes, FLAs and Gels are susceptible to PSoC use like AGMs, but not as much.

[PaulCrawhorn]

Originally Posted by Adelie

Marketing.

So true. "NEW" is powerful.

"No maintenance" BS

Only advantage is if you need to lie on their side or literally can't access the cells don't want to buy the waterer tubes