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

[a64pilot]

Originally Posted by john61ct

Starter batts are not cycled, normal cranking does not come close to DoD of 1%

And I know for myself, 5 years is considered a long lifespan, while I'm shooting for much more than that from my expensive deep-cycling banks.

Depending on location, alts in many modern very efficient vehicles are rarely putting out high voltages.

That is exactly correct they are not cycled, yet they stay at 14 V and don’t die, if they were cycled then the higher voltage would make more sense, yet again, the don’t die.
Five years is common for a Walmart battery, I usually get about twice that out of my red top Optima’s, Yellow top in our Prius.

What has location have to do with it? I don’t think most automobiles chargers are temperature compensated.
Measure your voltage at the battery terminals at much above idle my Miata and our GM automobiles both are right at 14V. It or were less than 13.8, I’d be troubleshooting why.

However the question of how are you killing a 660 AH bank with .2 amps hasn’t been addressed yet.
Again I’m not abdicating holding in my case 14.3 V forever, but from what I have seen, it wouldn’t kill a bank if I did. I would certainly expect it to reduce the life somewhat or Lifeline would simply state hold 14.3 B continuously, but they don’t, so it must not be optimal to do so, but an extra hour or so every now and again vs prematurely dropping to float day after day? I’ll take the extra hour or two every now and again.
It’s what I have been doing, whenever we run our generator, we end up with an extra hour or two in absorption, if we have a good Solar day, when we don’t run our generator we don’t quite get to 100% SOC.

[a64pilot]

It takes Maine Sail a bit over 6 hours at .2c to charge an AGM bank, and he states over 7 for a sulphated bank. Most of our banks are at least partially sulphated. This is from 50% SOC, but cutting it down to 75% SOC doesn’t even come close to cutting the time in half.
https://marinehowto.com/how-fast-can...ry-be-charged/
Higher charge rates don’t appreciably reduce charge times, so it’s my opinion that it takes 7+ hours to charge the average bank if is been discharged very much at all largely due to the fact that you only hove a coup,e of hours of good Solar output, the rest it starts barely making any power and ends the same way.

How many of these locations do you see that have on average 7 hours of Solar a day, and then add say 2 hours to get to a 9 hour Solar day which would be required to get to holding absorption for two hours past 100% SOC?
http://www.longtermsolar.com/solar-sunlight-hours/

OK some of you with exceptionally low power consumption and overly large Solar arrays may actually get there, but I’m willing to bet that the average cruising Boat doesn’t have a problem with over charging their batteries with Solar, unless the boat is in storage, but if it’s being lived on and used, not many can overcharge.

[noelex 77]

Originally Posted by a64pilot

Really, you charge your bank in only an hour or two at absorption voltage?

Yes this this a very typical absorption time.

I suspect you are using a Victron controller and it is important to realise that this controller simply starts a timer when the bulk voltage is reached. So the reported “absorption” times are very long. There is no requirment for the absorption voltage to be maintained for the timer to countdown.

It is a weird anomaly of this controller.

[john61ct]

Originally Posted by a64pilot

it must not be optimal to do so, but an extra hour or so every now and again vs prematurely dropping to float day after day? I’ll take the extra hour or two every now and again.

Originally Posted by a64pilot

I’m willing to bet that the average cruising Boat doesn’t have a problem with over charging their batteries with Solar, unless the boat is in storage, but if it’s being lived on and used, not many can overcharge.

Yes, I'm not sure who you are arguing with, you are right about occasional and/or short duration overcharging.

But chronic and long periods is harmful to sealed batts, less so to well-watered FLA.

_____
re Euro-style cars, I mean the ones with regenerative braking etc, VR is actually the ECU, only go over 14 while excess energy is generated etc.

Very common in countries with much stricter fuel efficiency and emissions regs, USA is now way behind those curves among more developed countries.

[a64pilot]

Originally Posted by noelex 77

Yes this this a very typical absorption time.



I suspect you are using a Victron controller and it is important to realise that this controller simply starts a timer when the bulk voltage is reached. So the reported “absorption” times are very long. It is a weird anomaly of this controller.

No, I have four charge sources.
Balmar 614 on a 165 amp alternator stays in bulk for maybe 15 min, spends hours in absorption.
Sterling pro charge Ultra 60 amp, May spend half hour in bulk, then 5 or more hours in absorption.
Magnum MS 2812 125 amp charger, up to 20 min in bulk, then 5 or six hours in absorption.
Outback 80 with 1000 W of panels, may spend most of the day in bulk then rest of day in absorption.

Remember all bulk means charge source is current limited, you exit bulk the moment when your charge source can make absorption voltage, in my case I exit bulk and enter absorption when my voltage is 14.3 plus or minus .1V.
Bulk time is determined by charge source size, a tiny charger will stay in bulk all day, a big charger maybe only a few minutes.
Limiting absorption time is very, very hit and miss, reason is Solar output is very variable, cloudy days and I may never see absorption, a strong cloudless day where my boat just happens to be oriented correctly on the anchor due to wind, it may get to absorption much more quickly.

Now if we have a charge source that you could set to return a percentage of removed amps and it return 105% of used amps, or one that would track acceptance rate and terminate at a set rate, then you’ve got something that you can set and it will vary with one day to the next.

But a timer? Only if you have no variables, and even the way my Boat is oriented and whether or not my mast shadows the panels makes a big difference in output, to say nothing about clouds etc.
A timer is a shotgun at best, in my opinion.
Timer doesn’t work on shorepower chargers, and then charge rate in known and doesn’t vary, with Solar it does, it you can’t meet it work on shorepower, what chance do you have on Solar?

[CatNewBee]

Yes, that is true, the start-stop batteries and the alternators are now actively managed, to increase fuel efficiency by sacrificing battery / starter life.

About Victron, they have a "smart" algorhythm, that sets absorption timer based on charged energy during float, so the absorbtion is shortened on shallower discharge cycles.

[john61ct]

The best timer algorithm is based on a percentage of the time it took to get from start to Bulk.

I believe that's the Victron option you mean.

[a64pilot]

Originally Posted by john61ct

The best timer algorithm is based on a percentage of the time it took to get from start to Bulk.

I believe that's the Victron option you mean.

No, that won’t work with Solar.
Th reason is Solar is a variable output, it’s constantly changing.
You would have to track either amps returned to the bank or the acceptance rate, either way would require a shunt, I think.

I don’t have a Victron, never have.

On edit, Due to the variation of Solar, I don’t think you can make a timer work.

[CatNewBee]

You just need the right gear. A good solar charge controller is aware of the radiation and incomming power versus outgoing current, it sees if the battery swallows all the energy and the voltage, it can estimate when it has to reduce the output and change to the next step, it also monitors the energy and time for bulk and can deduct the necessary time for absorption, it has several variables to evaluate, one is the timer for MAXIMUM absorption time, then tail current etc. Sophisticated charger have different timer settings according the chemistry, they know the battery capacity or can estimate it and they variate the absorbtion time if necessary. If the battery was nearly full when starting bulk, you do not need the full absorption time, because it will just meaningless fry your battery.

This is nothing you can do manualy, because of the variable radiation. The controller is aware of it and in the right position to do the educated decission.

One small problem are the variable loads during charging in absorption that make the tail current calculation difficult especially if the controller does not talk to the shunt. But it is not that bad either, he experience a higher current and will stay longer in absorption. if the load is higher, the voltage will drop below absorption, the controller cannot provide the energy used, so it will continue full power charging and cannot reduce the juice. It then stays in bulk, and this is also ok.

[Catapault]

Originally Posted by a64pilot

starts and ends trickle charging, unlike charging off of a generator or alternator, Solar doesn’t give high amps when high amps can be accepted.

Depends on your array. I agree they start by trickle charging as the sun comes up, but its 9:30am here, and my Solar Array is putting out ~100A into the system right now, of which 60A is charging the batteries. (was higher before I turned on the inverter).

This is probably A-typical though, in array size. (Though seems to becoming more common on cruising cats)

Mornings my biggest issues is shading, depending how we are swinging at anchor.


Regards

Mark.

[daletournier]

Originally Posted by noelex 77

Yes this this a very typical absorption time.

I suspect you are using a Victron controller and it is important to realise that this controller simply starts a timer when the bulk voltage is reached. So the reported “absorption” times are very long. There is no requirment for the absorption voltage to be maintained for the timer to countdown.

It is a weird anomaly of this controller.

When you say "this a typical absorption time" are you talking about your set up or others?

I don't believe this is a typical absorption time, your system may go into float but your batteries or at least mine will accept alot more. My experience with fla is that the regs are very conservative regarding voltage settings and premature switching into float. There is no doubt in my mind that PSOC is a much greater concern than over charging, at least when it comes to fla deep cycle, as long as you keep an eye on the electrolyte level.

A very large array is required (depending on battery bank size) for there to be any concern with over charging from solar when living aboard, it's just not going to happen. Theoretically maybe, realistically not going to happen.

[daletournier]

Originally Posted by Catapault

Depends on your array. I agree they start by trickle charging as the sun comes up, but its 9:30am here, and my Solar Array is putting out ~100A into the system right now, of which 60A is charging the batteries. (was higher before I turned on the inverter).

This is probably A-typical though, in array size. (Though seems to becoming more common on cruising cats)

Mornings my biggest issues is shading, depending how we are swinging at anchor.


Regards

Mark.

Very, very few boats have solar that can generate 100a let alone at 9am. As you said very atypical. I'm jealous, not that I'd know what to do with that sort of power production. At 9am I'm putting in 15a..lol.

[noelex 77]

Originally Posted by daletournier

When you say "this a typical absorption time" are you talking about your set up or others?

I was talking about a typical system rather than my own.

The solar controller on my last boat was one of the few that would terminate the absorption cycle based on end amps. So every cycle was terminated at the ideal point automatically.

On my last boat the absorption times were shorter than the times mentioned above, but I frequently started devices such as the fuel polishing and the water-maker when the controller was close to the absorption voltage. This avoided wasting any power and made maximum use of the solar output, but if you use this technique the absorption time can be very short. 15min or so was not unusual, but this was handled automatically by the controller.

My new system uses Victron controllers and these do not have a normal absorption time. I have not used the system long enough to reach any firm conclusions, but it is very hard to equate the Victron controllers absorption time with other charge controllers.

The Victrons need a much longer “maximum absorption time” setting to achieve a reasonable true absorption time. My absorption time on the Victron is currently set at 24 hours, but this probably equates to only an hour or so of real absorption time on my system. It is early days, however, and I have not seen enough cycles to fine tune the system.

[john61ct]

Originally Posted by john61ct

The best timer algorithm is based on a percentage of the time it took to get from start to Bulk.

I believe that's the Victron option you mean.

Originally Posted by a64pilot

No, that won’t work with Solar.
Th reason is Solar is a variable output, it’s constantly changing.
…
Due to the variation of Solar, I don’t think you can make a timer work.

Well 99.99999% of modern solar systems work that way.

The remainder are worse.

Those that work properly/ideally off a BM / shunt are not statistically significant.

And solar has been ahead of all other charge source types.

The Victron algorithm is better than most.

https://www.google.com/search?q=victron+"Absorption+time+multiplier"+algo rithm

[john61ct]

Originally Posted by a64pilot

You would have to track either amps returned to the bank or the acceptance rate, either way would require a shunt, I think.

Those are the same measurement, and only a small handful of rarely used BM/SC do it that way.

I agree that is optimal, but discussion here is about timer-based algorithms.

And how to guesstimate-calibrate them to optimize approximating getting to endAmps without overcharging.