Solar Watts : Daily AH Consumption

[daletournier]

Hi John, two mths since I got them. You get what you can get, I was in the Seychelles at the time with limited options. The guys that sell them don't understand the damage that comes with long term PSOC. Also I don't have the luxury of plugging into a marina therefore solar and/or generator are my charging sources.

I've had a shunt issue, only got around putting a new one on a week ago, I'm now monitoring the batteries more carefully as I can be more certain the data is accurate. The new shunt was part of the bluesky IPN Pro that I've purchased, this allows me to adjust charging perimeters to assure proper charging.

I'll give them another week of more vigorous charging as you put it and see if the acceptance rate changes. Not overly concerned, cruisers full is OK and they are performing well, never below 12.6v at dawn.


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[john61ct]

Originally Posted by daletournier

Hi John, two mths since I got them. You get what you can get

Yes, first world standards don't apply elsewhere, sorry.

> I don't have the luxury of plugging into a marina therefore solar and/or generator are my charging sources.

Even say once a month? Doesn't need to be a marina, just a place you can plug into mains overnight?

If not, maybe do testing and maintenance protocols on just one 12V pair at a time?

> Bluesky IPN Pro

Great unit, should let you terminate directly off endAmps, **and** one of the very rare charge sources where you can disable Float and Just Stop.

> Not overly concerned

Correct, but in striving for optimum you should have both longer life, and perhaps enough predictability to buy the next replacement set in a better setting?

[daletournier]

No shore power of any kind until October.
I agree, I like that the IPN allows me to determine float based on end amps, accept I'm not hitting the end amps I want.
First world problem, no biggy.


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[Dsanduril]

Originally Posted by CatNewBee

...Most SMF, GEL or AGM die from overcharging (boiling) because of wrong settings or poor solar controller that do reconditioning or have no temp sensor to reduce voltage at hot conditions and not from not reaching 100% SOC.

I would like to see some research/evidence around this contention rather than anecdote. Just as many anecdotes about chronic undercharging killing the same batteries. Also some definition about what exactly is an overcharge vs. a full charge.

Originally Posted by daletournier

Regarding trailing amps, the number thrown around here is. 5%-1% of Ah capacity. How did this number come about? A quick Internet search comes up with a range anywhere between 1%-3%. 3% is alot different from .5%.

Here is what the Concorde SunXtender AGM manual has to say:

The second stage is often called the Absorption charging stage. The battery is fully charged when the current drops below 0.5% of the battery's rated capacity (0.5A for a 100Ah battery).

https://telcoantennas.com.au/site/si...cal-Manual.pdf

And this is Trojan on AGMs:

Phase 2: Constant voltage absorption charge
A constant voltage equal to 2.35-2.45 V/cell is applied as the current slowly declines. The absorption phase ends when the current stabilizes at a low value of approximately 0.005 x C20.

https://www.trojanbattery.com/pdf/Tr...UsersGuide.pdf

For their FLA Trojan does indeed say 1-3%, but then they recommend a constant current charge at that rate after the end of absorption until you reach equalization voltage and bubbling is observed:

Phase 2: Constant voltage absorption charge

A constant voltage equal to 2.35-2.45 V/cell is applied as the current slowly declines. The absorption phase ends when the current falls to the finish current.

Phase 3: Constant current finish charge

A constant current equal to 1-3% of C20 is applied as the voltage increases [ed. note - this voltage increase is over and above the 2.35-2.45V/cell absorption voltage. The graph on the next page indicates that this constant current charge is terminated when the voltage just reaches the equalization voltage of 2.70V/cell]. The finish phase ends when the battery is fully charged. Flooded batteries will gas (bubble) toward the end of the finish phase to ensure proper mixing of electrolyte.

https://www.trojanbattery.com/pdf/Tr...UsersGuide.pdf

I don't know anyone who charges their T105s that way, but would be interested to hear if anyone does.

[sailorboy1]

You guys are making it so complex. They’re batteries, they are going to need to be replaced. Treat them”reasonable” and stop worrying so much.

[a64pilot]

Originally Posted by john61ct

I just wanted to emphasize that the goal is not "going to Float", at whatever time,

unless the owner has ensured the charge source is calibrated for her unique (and likely changing) usage patterns,

so that it does **not** go to Float until endAmps is reached.

Given normal deep cycling and lots of amps available for the early stages,

most banks still require **at least** 4 more hours to finish the long tail after they get to say 85-90%.

The **vast majority** of real-life setups are going to Float many hours too early, and fooling the owner with blinky lights, an LCD bar chart or even false numeric info, into thinking the bank is Full.

The **only** way to know whether or not that aspect is configured properly, is to periodically verify - with a known-accurate ammeter at the bank - that the controller is putting out Absorb voltage until endAmps is reached.

So without specifically stating that is the case, IMO the default response to "I'm usually done charging by noon" should be (a polite version of) "dog's bollocks you are".

Brother, you can preach all day and some are just not going to listen.

If you Read Maine Sails direction on how to set up a Balmar 614, he makes the point that he has observed 2 AGM banks over the years that have died from overcharging, only two, and apparently both of those were connected directly to Solar panels and left on moorings, not discharging appreciably over night, and being hit hard with excessive voltage, day after day.
He says this to make a point that your not going to damage your AGM bank by leaving the dock with them at 100% SOC and the alternator running at absorption voltage for 5 hours.
Just for kicks I turned my charger off and back on the other day when the bank is at 100% SOC. After a very few minutes my 660 AH bank was accepting .5 amps, that is 1/2 an amp, al little over 7 Watts.
I’m going to boil out my several hundred pound bank of 6 batteries with 7 Watts of power?

No, you kill them by letting them go to much higher than absorption voltage and staying there, day after day.

If you don’t believe me, try it yourself on a bank that your certain is truly, fully 100% SOC, Kick it to absorption voltage and see how many amps the bank is accepting, not how many the charger is making, but how many are actually going into the bank.
My bank is 100% SOC when acceptance is 3 amps, or about 45 Watts.
Just tried it again for kicks, bank is accepting .2 amps at 14.3 VDC.
Now I’m sitting in a marina and have been in float for a long time, so bank is really, fully 100% SOC.
If I keep it in absorption voltage, it’s full at 3 amps at absorption, but if I keep throwing absorption voltage at it, the acceptance continues to drop, apparently to .2 amps, but your not getting enough heat with single digit amps to hurt anything.
I’m not abdicating leaving your bank at absorption voltage while your in a marina for long periods of time, but your not going to hurt your bank if it stays in absorption for an hour or two every now and again.
Or if you believe Maine Sail, even for five hours, every now and again.

[john61ct]

Yes, no disagreement here about any of that.

[daletournier]

Originally Posted by sailorboy1

You guys are making it so complex. They’re batteries, they are going to need to be replaced. Treat them”reasonable” and stop worrying so much.

Hmmm.. I went back through the archives recently regarding batteries, you pop up now and then asking things "like efficiency settings", not sure we're complicating things anymore than a question like that.

Anyway it's a good discussion that helps us understand one of our main systems.

From everything I can see the argument of staying in absorption mode if cruising is correct purely because our batteries rarely get full from solar alone, I can see this clearly with mine, they just do not get below 2-3%C from solar, not going to happen therefore no need to flip into float because they aren't full. It's really that simple.

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[CatNewBee]

Originally Posted by Dsanduril

I would like to see some research/evidence around this contention rather than anecdote. Just as many anecdotes about chronic undercharging killing the same batteries. Also some definition about what exactly is an overcharge vs. a full charge.


....

Well this is embarassing, but this happened even to me as I bought my pre-owned Lagoon.
On board were 3 x 150Wp panels and a dirt cheap Stecca PWM controller retrofitted.

We bought the vessel late autumn and winterized it in France on the hard, all switches off, shore power, charger set to storage mode with lower float.

In the spring I was on board and checking the voltages, everything looked good so far, batteries at 13.6V, etc. Had some work to do and did not concentrate on the electric.

Then the alarm sounds Overvoltage, one GEL battery was hot as hell, of course not the one with the temp sensor attached to. 15.8V! Turned off shore power, still 15.8V. Reason was the Stecca. This is a PWM controller for wet open lead acid batteries. it does "smartly" recondition every 4 weeks, no settings for other battery types or turn off recond function, otherwise it yelds safe 14.3V absorption, 13.6V float - suitable for the GEL. If I was not on board at the right time, I barely would have noticed that issue.

Controller connected directly via a fuse to the battery, battery main switches had no effect on solar. So my bank was 6 times boiled for several hours during the winter without knowing it.
2 Excide equipment GEL 120Ah dead, the one was high resistance dead cell 9.6V, the other was cell short and boiling, smelling like rotten eggs, wel only for some hours every 4 weeks, but yes, **** happens. I throwed the crap controller out. Well, 2 GEL batteries survived the abuse. But it will be a matter of time when they will fail too.

This is when people safe money on the wrong end, The stuff was semi-professionally installed - I guess by an amateur electrician in the yard with no idea about solar and battery chemistries, the boat was in charter for several years, no one really cared a about it so far.

Also the starter battery of the Gen was dead discharged and could not be reviwed, it was by manufacturer design not hooked up to any charge source on board. So dead from deep discharge.

That led me to review and refit all the electric systems, and also going for lithium and the right automatic monitoring of all batteries on board.

[sailorboy1]

I have 290W solar with 460AH T105s.

I have my solar controller set to stay in absorption, 14.8V, for 4 hours or 2 amps. It wouldn't drop to the 2 amps unless the refrigerator shuts off and that never happens. I have seen the system go into float a few times if the day started at -50AH.

I don't worry if the batteries get to 0.5% C acceptance everyday and just try to get to that level of charge once a week or so. Maybe my batteries will less 1-2 year less than they could by doing this, but the cost of the batteries lost by 1-2 years of their life is so low in the big picture than sanity is more important.

BTW - my past question about what people were using for their charge efficiency wasn't a complex thing, till experts decided to argue about it. Forums like to "debate" things, but real life rarely matches theory.

[noelex 77]

Positive grid corrosion is the biggest concern when charging at absorption voltage beyond the end amps.

“Killing the battery” needs substantial under charging or gross overcharging. I agree it is much more likely to happen with undercharging. If you leave a lead acid battery at a low SOC for a reasonable period of time, it is fair to say you have indeed “killed the battery”. It is much harder to do this with overcharging, although not impossible.

To avoid “killing” a lead acid battery is not difficult, but is unfortunately inevitable that every discharge and every charge cycle is causing some damage to the battery and shortening its life. The key to a long battery life is to minimise the damage.

Both undercharging and overcharging cause more damage than charging the battery in the recommended way. I don’t believe that charging the battery at the absorption voltage past the recommended end amps is consistent with best practice, or consistent with extending the life of the battery.

To get the most charge into your battery as quickly as possible, the most important check is voltage setpoints. The default categories have to cover a large number of batteries and the setting are usually on the conservative side.
Setting these to recommended settings for your battery (don't forget temperature compensation) is the best adjustment you can make.


I would also encourage checking the end amp near the termination of the absorption time. By all means increase the time if it is needed, but the defaults (usually around 2 hours) in my experience are usually generous and some need to be decreased especially if your normal charging rate is low, which given the limited room for solar on a boat is common.

[Pelagic]

[QUOTE=noelex 77;2651651]

To get the most charge into your battery as quickly as possible, the most important check is voltage setpoints. The default categories have to cover a large number of batteries and the setting are usually on the conservative side.
Setting these to recommended settings for your battery (don't forget temperature compensation) is the best adjustment you can make.
QUOTE]

Thanks Nolex.....Trying to put all the suggestions into my own layman's game plan and charging profile using Solar and Alternator/Generator bulk charging to maximize the lifespan of my AGM Batteries.

1. Be satisfied with default set points (temp compensated) for your batteries. Tweaking defaults runs the risks of overcharging issues when boat is unattended and/or out of service.

2. I consume approx 10% of house bank ar anchor conditions in 24hrs. If I allow 8 hrs Solar production, then net loss of SOC in 24hrs is about 6%

3 Now at Dinner Time, with new Induction Hob inside and Weber BBQ outside, if I used Generator and the 70 + 50 amp Victron Chargers to bulk up batteries from 74-80% SOC (say about 1.5hrs) + cooking, making water, heating water, freezing Eutectic Mix. I have batteries at 80% going to sleep.

Then with morning SOC @ 74%, that should allow Solar to reach absorbtion stage, especially if we are off the boat during the day.

Before Solar, I ran my Gen in the morning to 80% for 2-3 hrs, but now it seems that Generator make-up (if needed) makes more sense. around dinner time?

Is that what experienced Solar users find?

[a64pilot]

Originally Posted by Pelagic

Before Solar, I ran my Gen in the morning to 80% for 2-3 hrs, but now it seems that Generator make-up (if needed) makes more sense. around dinner time?

Is that what experienced Solar users find?

No, the generator assuming you have a large charger can really shove power into the bank in the morning, in the afternoon a bank will only accept a trickle charge, so continue to run the generator in the morning.

The myth if you will of being able to obtain 1/3 or panel rating in AH assumes the bank will accept it, which if your going to get near to 100% SOC, it will not, with lead acid batteries, LFP is different.
On an average Winter day in Fl, I can get to 100% SOC with a one hour generator run, however when I do run the generator it’s for more than an hour so I’m assured to get to 100 % SOC.

[john61ct]

And forget default settings, that is almost guaranteed to result in never getting to Full, very harmful especially for AGM.

The first thing to check is that your voltage setpoint is within the range specified by the batt mfg, usually at the high end is better than low.

Next most important is to adjust Absorb Hold Time to ensure you're getting to 100% Full, as defined by endAmps spec'd by the batt mfg.

If you are using a cheap non-adjustable SC then you have no control.

But if your SC is adjustable, take advantage, it's really not hard to get at least as close as you can to optimum.

[sailinglegend]

Originally Posted by a64pilot

.....Just for kicks I turned my charger off and back on the other day when the bank is at 100% SOC. After a very few minutes my 660 AH bank was accepting .5 amps, that is 1/2 an amp, al little over 7 Watts.
I’m going to boil out my several hundred pound bank of 6 batteries with 7 Watts of power?

No, you kill them by letting them go to much higher than absorption voltage and staying there, day after day.....

Originally Posted by john61ct

Yes, no disagreement here about any of that.

Well Im afraid I have to disagree with both of you.

It's not the current that does the damage - yes 7 Watts into a large bank is not going to do any harm, but you are right it is the voltage that does the damage. But, and this is the big BUT, is it doesn't have to be 'much higher' than the absorption voltage to do some damage, which is why all battery manufactures say batteries must be dropped to a float voltage when they are full.

So what actually happens at the 'absorption voltage'?

Batteries need to reach this "absorption Voltage" to start to gas slightly in order to charge properly. This stirs up the electrolyte in FLA batteries to stop stratification, which is where the acid concentration falls to the bottom which can cause damage to the plates, and the gassing helps to burn off the Lead Sulfate crystals that form as a natural consequence of the discharge process. This is 'Sulfation' which will become permanent and reduce the capacity of the battery if left too long without getting to 100% fully charged - this means all the lead sulphate crystals have been converted back to Lead Oxide and Sulfuric Acid. Equalisation at higher voltages may help to remove these crystals after a week or two when they have started to harden.

During the absorption phase of charging the battery can sit at its gassing voltage of 14.4 volts for many hours with no problems, there will be small amounts of gassing but the electrical energy from the current is charging the batteries. It is only when the batteries are fully charged, and still sitting at the gassing voltage, that this voltage will causes the batteries to gas much more heavily. This leads to loss of water which is fatal for sealed leisure batteries. The more expensive sealed batteries may use different metals which helps the hydrogen gas, H2, and oxygen gas O, recombine inside the battery to put water - H20 - back into the electrolyte. This will extend their life and stop them drying out too quickly.

By reducing the charge voltage from 14.4v to a float of 13.8v or less gassing will stop. It is worth noting that gassing voltages and therefore the correct absorption charging voltage are based on battery temperature, 14.4v of 25ºC, 14.2v at 30ºC, 13.98v at 40ºC.

This is why it is so important to have multi-stage regulators on ALL charging sources that will drop down to float mode when they 'THINK' the batteries are fully charged.


One more thought on 'overcharging' with solar controllers.

Solar panels, even small ones, can easily keep the batteries full charged with low loads, but if left connected for 6 months when all loads on the boat are switched off they can “overcharge” and “boil” batteries even with a quality solar controller. This happens because every night solar provides no power and switches off, when they sun is up the controller switches on and goes straight into bulk mode. Because the batteries are almost 100% full they very quickly reach absorption which takes the battery up to the gassing voltage. But even smart controllers are pretty dumb, most don't know the battery is really almost fully charged so when it automatically kicks into absorption it may stay there for the pre-programmed time period of say 3 hours before it drops to float. The battery won’t be taking any current when it is full but it’s the voltage that does the damage, especially if applied for three hours everyday for 6 months to already fully charged batteries! I've seen many batteries bolted dry at the start of the season due to solar panels fully exposed all winter.

I have just installed two new Victron SmartSolar charge controllers and the 'Drop to Float' feature at 1 amp is fantastic and will stop overcharging over winter.