Is There a Point to Float with LA/Liveaboard/Solar

[a64pilot]

Originally Posted by Adelie

If the batteries haven’t gotten to end-amps then the controller shouldn’t be kicking into float voltage anyway and it should continue at absorption voltage until sundown.

That’s not how any of them work though, I’m sure there may be one out there, but is almost like looking for a Unicorn.
It’s the way it ought to work, I’d pay extra for it, but I don’t know if any that do work that way.
If you have the optional battery monitoring kit installed, my Magnum inverter / Charger can be set to, but my Sterling Pro charge Ultra can’t, by Balmar 614 can’t, and my Outback 80 can’t.
They all work off of essentially just a timer

[john61ct]

Originally Posted by Adelie

The OPs question asked whether ther was a problem leaving the charger at absorption voltage for several hours (2-5) after reaching 100% SOC?

Not how I read it.

Originally Posted by Dsanduril

On our own boat, with a fairly large solar array and fairly small daily usage we find that we can get to end-Amps between about 2 and 4 in the afternoon (as long as we've had good, sunny days). So, the question is, is there really any point to dropping back to float for an hour or two before the sun goes down?

And the key qualifier is, using what batteries?

> if you leave the boat unattended for a period it will be overcharging all day every day unless you remember to switch charging to float.

Yes, that's the Achilles heel, anything that requires good memory and mindfulness is IMO dangerous, unless the owner is diligent, running routines off checklists.


> If the batteries haven’t gotten to end-amps then the controller shouldn’t be kicking into float voltage anyway and it should continue at absorption voltage until sundown

Very few charge sources change state based on current amps measured by a shunt at the bank.

Upgrading to ones that do eliminates all these "eggtimer ballparking" issues.

[a64pilot]

Originally Posted by Dsanduril

As liveaboards we know there will be usage immediately after sunset, and even if we're away for a few days the fridge will run things down some overnight. Given that usage (where I know we won't be better than 90% SOC in the morning) is there really any point to float? Since the contention is that we don't reach 100% SOC as often as we should, are we better off 'floating' at absorption voltage for an extra hour or two (at the most) and making sure things are really up at 100% when we can get them there? Or would that irreparably harm the batteries?

Also it wasn’t 2 to 5 hours, it was an hour or two (at the most) which is a lot different than 5 hours. For it to be 5 hours, that would require 100% SOC before noon, which isn’t likely, or maybe being way North in Summer I guess?

[john61ct]

Originally Posted by a64pilot

That’s not how any of them work though, I’m sure there may be one out there, but is almost like looking for a Unicorn.

Overstating the case.

Your Magnum kit does, for shore / genny charging.

At least four solar controller+BM rigs do as well.

It would not be hard to rig a BM to cut off alt output either, but it's rare for dino juice to be burnt that long every day anyway.

[Adelie]

Originally Posted by a64pilot

That’s not how any of them work though, I’m sure there may be one out there, but is almost like looking for a Unicorn.
It’s the way it ought to work, I’d pay extra for it, but I don’t know if any that do work that way.
If you have the optional battery monitoring kit installed, my Magnum inverter / Charger can be set to, but my Sterling Pro charge Ultra can’t, by Balmar 614 can’t, and my Outback 80 can’t.
They all work off of essentially just a timer

The Sterling is an AC charger and the Balmar 614 is an alternator regulator which are both outside my area of interest and research.

The manual for the Outback Flexmax 60&80 indicates on Pg-49 (pg-51 of the PDF) how to set Absorbtion time limit (which can be as high as 24hr) and the end-amps for absorption.
http://www.outbackpower.com/download...ner_manual.pdf

If you have a non-Flexmax model let me know and I’ll try to find the manual for that.

[john61ct]

But unless there are no varying loads (a very rare case) the regulator just doesn't know how many trailing amps are being accepted by the bank.

Unless it's designed to coordinate with a shunt-based BM unit.

[Adelie]

Originally Posted by a64pilot

Also it wasn’t 2 to 5 hours, it was an hour or two (at the most) which is a lot different than 5 hours. For it to be 5 hours, that would require 100% SOC before noon, which isn’t likely, or maybe being way North in Summer I guess?

OP indicated reaching 100% at 2-4pm which is accurate if not precise. Indicating 1-2hr until sunset is more precise but likely very inaccurate unless sailing higher latitudes off season.

At the equator sunset is about 1800 year round. That’s 2-4hr past 100%.

I’m in San Diego where sunset is currently almost 2000. That would be 4-6hr past.

In Seattle sunset is about 2100, 5-7hr past.

At the equinoxes sunset in both San Diego and Seattle are both around 1900 which is 3-5hr past 100% on a sunny day.

2-5hr overcharging at absorption voltages is the more accurate expectation than 1-2hr.

[a64pilot]

Originally Posted by Adelie

The Sterling is an AC charger and the Balmar 614 is an alternator regulator which are both outside my area of interest and research.

The manual for the Outback Flexmax 60&80 indicates on Pg-49 (pg-51 of the PDF) how to set Absorbtion time limit (which can be as high as 24hr) and the end-amps for absorption.
http://www.outbackpower.com/download...ner_manual.pdf

If you have a non-Flexmax model let me know and I’ll try to find the manual for that.

That is total amps, not acceptance amps. If you set it at say 8 amps cause your fridge normally draws 5 and you want it to go to float when. Acceptance is 3, then 15 sec after your fridge turns off, you go into float, prematurely.
Yes, it will work if electrical load is static, but it’s not. The same with the timer approach, throw in one variable and it doesn’t work.
Only thing that does work to my knowledge is if you have a shunt that can measure how much power is going into the bank, and if your charge source can connect to this shunt and then if it can be programmed to go into float when the absorption limit is reached.
The other method is to have a shunt and manually watch it to see when to select float.

Due to too many variables, you cannot accurately use either timer or total amp method and be accurate, too much variation in Solar output and bank usage for either method to be effective.
This why I believe Maine Sail recommends leaving it in absorption, my experience concurs with his recommendation, but I have an AGM bank that is especially susceptible to short cycling

[a64pilot]

You don’t get usable power until sunset, especially if like most boats your panels are flat, you may get 12 hours of sunlight, but are doing good to get 8 hours of appreciable Solar output, and I’m being optimistic.
I want to think Maine Sails measurement is closer to 5 hours a day, but that is from memory.

[a64pilot]

Understand I am not saying leave a boat that is in storage at absorption, Im saying a boat that is being lived aboard and cruised leave in absorption, specifically this case as was presented in the first post, leave in absorption.
In my opinion

[a64pilot]

This insolation map can give you an idea.
It’s worst month, but it’s also optimally tilted, one may well wash the other.
http://www.solardirect.com/outdoor-l...ation-map.html

[a64pilot]

Only plausible data I could get for flat amounted panels, I’m sure there is better data, but your doing good to get 6 hours

Actually it seems I may have been wrong, the panels are tilted for best angle for location, just they are flat panels, I interpreted it to mean they had no tilt.
Flat mounted panels of course are worse.

[Adelie]

Originally Posted by a64pilot

That is total amps, not acceptance amps. If you set it at say 8 amps cause your fridge normally draws 5 and you want it to go to float when. Acceptance is 3, then 15 sec after your fridge turns off, you go into float, prematurely.
Yes, it will work if electrical load is static, but it’s not. The same with the timer approach, throw in one variable and it doesn’t work.
Only thing that does work to my knowledge is if you have a shunt that can measure how much power is going into the bank, and if your charge source can connect to this shunt and then if it can be programmed to go into float when the absorption limit is reached.
The other method is to have a shunt and manually watch it to see when to select float.

Due to too many variables, you cannot accurately use either timer or total amp method and be accurate, too much variation in Solar output and bank usage for either method to be effective.
This why I believe Maine Sail recommends leaving it in absorption, my experience concurs with his recommendation, but I have an AGM bank that is especially susceptible to short cycling

Do you have a link to MS’s recommendation?

[a64pilot]

Originally Posted by Adelie

Do you have a link to MS’s recommendation?

No, I looked quickly, my Google ** sux.
He has made that recommendation on this forum a few times though. He is why I leave mine in absorption, I have a tendency to listen to him. I sometimes seems to disagree, but have yet to find fault in his testing methodology.
Like the fuel tank condensation, I’ve been taught all my life to leave tanks full so they don’t, his testing seems to indicate it’s a myth though, just hard for me to go against a lifetimes teaching is all.

[daletournier]

Originally Posted by a64pilot

No, I looked quickly, my Google ** sux.
He has made that recommendation on this forum a few times though. He is why I leave mine in absorption, I have a tendency to listen to him. I sometimes seems to disagree, but have yet to find fault in his testing methodology.
Like the fuel tank condensation, I’ve been taught all my life to leave tanks full so they don’t, his testing seems to indicate it’s a myth though, just hard for me to go against a lifetimes teaching is all.

I also leave mine in absorption, do on this boat and did for several years on my last. I fairly certain it was after reading one of mainsails posts some years back.