Will a small solar regulator actually charge a house battery

[hzcruiser]

Originally Posted by guyrj33

John, I think we're talking past each other, comparing apples to oranges.

I have FLA batteries and like NZ I see current flowing at 13.8v. Yes I'm using a Victron BM to count AH.

I'm not John, but anyway, yes, if you see a current flowing into the battery it will charge the battery, no doubt about that. Whether it will get to 100% SOC at some point would be another question, of course.

[john61ct]

Above is true.

Note it is completely normal for charge sources, even top quality very expensive ones, to drop to Float prematurely out of the box.

Again, user needs to be able to adjust the Hold Absorption Time settings until endAmps spec is achieved under that setup's usual charge/discharge patterns.

Originally Posted by john61ct

The actual setpoints vary from batt to batt, which is why charge sources need to be user adjustable.

Full is not defined by voltage.

And with the charger on Float connected, there is no separate "charging voltage" vs "battery voltage", there is one combined voltage, which at some point remains with no more current flow, due to batt resistance.

Turn the voltage up to Absorb and current now flows again, think voltage=pressure.

Until that current *at Float voltage* drops to .005C the bank's not yet Full.

Critical brain fart in that last sentence, sorry, here is the correction:

Until that current *at Absorb voltage* drops to .005C, the bank's not yet Full.

To be clear, for a 100AH bank, that endAmps spec is half an amp.

The same standard can be used to help tweak the BM's charge efficiency and/or Peukert factor settings to try to improve its accuracy, in this case preventing it from showing 100% Full too early.

But all this is secondary to getting higher current charge sources in place, ideally before installing the replacement bank.

.2C is IMO a target minimum, 20A per 100AH capacity. Higher for AGM if practical.

[TheThunderbird]

The VOLTAGE provides the charge, in A amounts.

E.g. 200A on a 0,5V gross differential do not charge.

Your V is way low from solar.

Put TWO panels is series on an MPPT.

[TheThunderbird]

The truth?

Trojan PRETENDS 14,7V - NO LESS
DEKA wants 14,4-14,7V

NOW, consider my STUPID QUICK CHARGER (680EUR 2014)

It charges 14,1 -14,4V
I have no f...g comment to add, or I'll get banned. Enough for stupid Makers
Then, check Victron Skylla (not Centaur, nor Phoenix)
...

yes, they want to avoid gassing, ... F.. Their hell

[guyrj33]

Originally Posted by hzcruiser

I'm not John, but anyway, yes, if you see a current flowing into the battery it will charge the battery, no doubt about that. Whether it will get to 100% SOC at some point would be another question, of course.

My apologies to both John and hzcruiser.
I do think it's important to discuss FLA and Lithium in distinct threads, the chemistry and control of FLA is very different than LFP.

I think some of the discussion about absorption and float set points for a MPPT controller on a small solar panel like I have (23W solobain with builtin MPPT) are irrelevant. The panel will supply whatever current it can with a max of about 1.5Amps, the voltage seen across the battery will be determined by the internal resistance of the battery and the current available to charge it.

When I get back to the mooring after a day sail my engine has been running for 20 minutes which is enough to get the batteries past bulk charge.
When I get back to the boat a couple of days later the panel has supplied enough power to finish charging my house bank. The numbers from my small 23W panel look something like this 7AH per day * 5 days = 35AH which is enough to bring my relatively small 225AH FLA house bank back to full charge and keep up with the occasional cycling of the bilge pump.

[john61ct]

Originally Posted by guyrj33

I do think it's important to discuss FLA and Lithium in distinct threads, the chemistry and control of FLA is very different than LFP.

Maybe I missed it, I certainly was not thinking about LFP in my comments, as they have no need to ever get to 100% Full.

Originally Posted by guyrj33

voltage seen across the battery will be determined by the internal resistance of the battery and the current available to charge it.

I agree with a small enough current it may not in practice matter much, but in general it is important - if proper care of your bank matters - that voltage is regulated to not exceed mfg specs.

Originally Posted by guyrj33

The numbers from my small 23W panel look something like this 7AH per day * 5 days = 35AH which is enough to bring my relatively small 225AH FLA house bank back to full charge and keep up with the occasional cycling of the bilge pump.

In real life panels never average putting out their rated power.

Each setup's conditions are unique, and - again, if proper care of your bank matters, then - whether your bank is regularly getting back to true 100% Full needs to actually be hands-on verified as discussed above.

Relying on calculated specs or even an expensive BM is not enough.

[guyrj33]

Originally Posted by john61ct

Maybe I missed it, I certainly was not thinking about LFP in my comments, as they have no need to ever get to 100% Full.

hzcruiser, referenced a chart showing the charging characteristics of a system with an LFP battery.

I agree with a small enough current it may not in practice matter much, but in general it is important - if proper care of your bank matters - that voltage is regulated to not exceed mfg specs.



In real life panels never average putting out their rated power.

That's why I used 7AH per day for my guesstimate.

Each setup's conditions are unique, and - again, if proper care of your bank matters, then - whether your bank is regularly getting back to true 100% Full needs to actually be hands-on verified as discussed above.

I've verified full with a BM and a battery hydrometer.

Relying on calculated specs or even an expensive BM is not enough.
I agree.

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[kenbo]

To the OP, the simple answer to your original we question is yes, if all three components are in good condition.

You really need to identify if any of your components are bad. Fully charge the battery on shore power the draw around 20% of the capacity out. Then connect your solar panel directly to the battery bypassing the controller. Do this on a sunny day and observe the voltage on your battery terminals and amperage. This should give you enough info as to the health of your components. Disconnect the solar panel if the battery voltage exceeds 14.8v.

I suspect that your battery is very weak from your description. Can you check your specific gravity 12 hours after being fully charged?

[daveNZ]

I’m inclined to agree with you Guy. John’s comments also match what I understand about FLA behaviour and management. I would just like to believe that I’m still charging even at float voltage. Maybe the answer is down to the chemistry of the process, but I should be able to verify with a hydrometer.

So I also should be using a hydrometer to verify charging, and maybe doing (another) discharge test to see what the current battery capacity is. Also I plan in future to watch the Ah used more than the SOC figures.

[john61ct]

Hydrometer requires batteries to rest for a period just like voltage.

A decent ammeter is only $30-50, observe trailing amps falling at Absorb voltage is really The Standard for determining Full.

That is also how you help your BM stay accurate, do not depend on it as a primary source.

[john61ct]

Maine Sail's https://marinehowto.com/

Everything there is brilliant.

Search for "battery monitor" in the front page for three excellent in-depth articles.

[daveNZ]

Thanks John, I do have a Victron BVM 700, bought mainly for the ammeter. I watch the amps regularly, in and out; interesting how quickly the alternator output (battery acceptance!) reduces, and it is also useful to be able to reduce engine rpm if charging at anchor for an hour, as battery acceptance reduces. I reduce rpm then increase until charging amps no longer increase. Just less noise.

I’ve read all Mainsail papers. Fantastic, useful and clear for most part. I fully understand
all the reasons SoC has so much potential for error. I was pleased to see he recommends Genasun solar controllers for small panels. I’m just wondering if the caveat should be, ‘once the battery is fully charged’? I’m still not sure.

One further query, when people mention not going below 12.2V I assume that is resting V. I drop about .3V under fridge load, so 12.2 is a bit of a guess.

The 10.5V used for a C20 test end point I believe is the ‘with load’ voltage. I did try such a test, the voltage plummeted quickly past 10.5V, in between my checks. And I found my multimeter was rubbish so I have bought another! Need to repeat the test!

[john61ct]

Originally Posted by daveNZ

interesting how quickly the alternator output (battery acceptance!) reduces
…
I’m just wondering if the caveat should be, ‘once the battery is fully charged’? I’m still not sure.
…
One further query, when people mention not going below 12.2V I assume that is resting V

Just know most stock alt setups are pretty poor charge sources, so watch volts as well as trailing amps, don't bother using dino juice once either drops, that's what solar is for.

Caveat against what?

Once you're monitoring AH depletion, use that rather than depending on voltage guesstimates to avoid going much below 50%.

Yes the 10.5V "0% SoC" floor is while drawing .05C, or 5A per 100AH capacity, aka the 20-hour rate.

After the breaking in period, that should obviously only be done for load-testing purposes, IMO no more than quarterly toward EOL.

And immediately followed by a Full recharge, never allow just sitting more than a few minutes at such extreme low state.

[daveNZ]

Thanks John,
the caveat I meant was, “small Genasun might be good for float charging, BUT not for getting there from say 80% charged”.
My internal regulator goes to 14.4V, so I’m going to follow MaineSail’s advice for my type of boating....a smart regulator that goes to float might never get there, so don’t waste my money. I rarely motor for more than 4 hours. Usually 2 or 3, so I usually need to run motor at anchor to charge. (I need more solar, I know).

[john61ct]

Tiny quiet portable genset may give more flexibility.

And an LFP bank keeps accepting full current, and no need to ever get to Full.