Will a small solar regulator actually charge a house battery

[hellosailor]

dave-
Genasun made many devices, it might help to know exactly which one this is, and what the ratings and intent of it are. And of course whether it was custom-set to match the battery in any way.
Then it would help to get a reasonably accurate picture of the battery's real condition. When you think it has been charged to whatever is "usual", disconnect everything for a couple of hours, overnight if possible, and THEN measure the battery voltage with a calibrated voltmeter. That gives a pretty good idea of the real battery condition. Not perfect--but good enough so that most battery makers will go by it.
The meter must be calibrated or "known good" because with every 1/10th of a volt goes 10% of the battery capacity, and I've seen meters off by 0.4 volts (40% capacity error) new out of the box. Or, off by 0.2 volts (20% capacity) simply after they had aged ten years in normal use.
And of course, what the battery maker calls normal for that battery. Some chemistries are 12.6 when fully charged, others are 12.8, you need to know what this one is rated at.

[FionaJC]

What everyone said here but you will need a controller. I had a PWM which was useless, my batteries would drop to 0V over winter. I have now changed to an EPISOLAR MPPT and that is the only way to go. I have 200W of solar on the deckhouse and on dull days it gives 16V and 1Amp of charge, The old PWM did nothing. I have 220 A House and 110 Start. I have an 80A alternator going through n Adverc regulator and a Voltage sensitive relay which I have added a diode to make it one way. I use a NASA BM1 battery monitor and I can charge through shore power 40A or a 2KVA generator. Its perfect. I also have a standby 110Ah battery that I can switch in and out manually as an extra to the start or house battery. Its all cross switchable and monitored. When I am away I have essential summer switch for Navtex, bilges and Gas detection monitored through a raspberry pi based web monitor which give me environmental with alarms too. In winter I just run the bilge pumps as essential..

[Colin A]

Originally Posted by daveNZ

Guy(?),
I had hoped my (ex 40Watt) panel would do the same. My question is ‘why does the solar regulator not go to absorption mode’. One opinion is that there is not enough power from the panel. So Assuming my battery is not fully charged, why does it charge at 13.5 (can’t remember exactly) float voltage, and 1 to 2 amps? Should it not be trying to charge at 14.x at least, even if that means .5 A. (VOC - Open circuit V for my panel is over 20V)
Does your Solbian panel change at absorption level?

Looking up the specs on your MPPT. It looks like absorption is time based at 2 hours then it shifts to float. It sounds like it's never putting enough to even get to float which looks like it's 13.8 based on the web. The current going in means it is charging the battery, It just may not be enough to either over come parasitic loads or the battery is cooked.

[guyrj33]

Originally Posted by daveNZ

Guy(?),
I had hoped my (ex 40Watt) panel would do the same. My question is ‘why does the solar regulator not go to absorption mode’. One opinion is that there is not enough power from the panel. So Assuming my battery is not fully charged, why does it charge at 13.5 (can’t remember exactly) float voltage, and 1 to 2 amps? Should it not be trying to charge at 14.x at least, even if that means .5 A. (VOC - Open circuit V for my panel is over 20V)
Does your Solbian panel change at absorption level?

I don't really know the answer to your question about absorption voltage, I can tell you the panel puts up to 1.5 amps into the battery under ideal conditions and that my battery voltage is around 13.8v (panel still connected) when I come back to the boat.

[FionaJC]

13.5V to 20V @1Amp = an MPPT charger will charge if the batteries need it at around 1- 1.4A. A PWM will delivere 1A at 13.5V The MPPT is more efficient. If your battery doesnt need charging then it wiont charge, solar will only give what it can. The MPPT will convert higher voltages into more current charge.

[john61ct]

A 100% Full battery

which is required most cycles for longevity

is best defined generically as

holding Absorb until current falls to .005C.

Letting voltage drop to Float before that point means the batt will **never** get Full, even connected for weeks.

To test this, wait until current stops flowing at Float (or at least the tiny amps level doesn't change for hours).

Then apply higher Absorb voltage, and observe the current is now higher than .005C, IOW the bank is not yet full.

As I mentioned an easy workaround with underpowered solar is just change the Float voltage to equal what you have set for Absorb.

With more reasonably sized solar, you need to manually ensure you don't overcharge.

Really just much easier to get a controller that you can just set and forget, once you get the settings calibrated.

[guyrj33]

John
"Letting voltage drop to Float before that point means the batt will **never** get Full, even connected for weeks."
I'm having some trouble understanding this, perhaps you can offer more explanation for me.
If the charging voltage is higher than the 100% full level of the battery, won't energy be delivered to the battery?
I think I recall FLA absorption level being around 14.4v and float around 13.8v for a multi-stage voltage regulator/controller.
so yes, 13.8v means there would be less power V*I being delivered to the battery, but it would still be charging the battery and would eventually charge the battery.
I'm ignoring the case of a milli-amp trickle charger and assuming we have a 27W or larger solar panel supplying the charge.

Thanks

[hellosailor]

Fiona, your dead batteries had nothing to do with PWM versus MPPT. MPPT actually all is PWM, with a smarter microprocessor supplying and controlling the PWM charging.

Your PWM charger was either insufficient, or defective, that's all.

Here in the Colonies we all know that "NASA" are the folks that send rockets to the moon. It would be considered a deceptively clever scam to start a private company in a "scientific" area that duplicated the same name. But then again, the BBC seems to think that NASA should be spelled "Nasa". Which would make sense, if they called themselves the"Bbc".(G)

[hzcruiser]

Originally Posted by guyrj33

John

If the charging voltage is higher than the 100% full level of the battery, won't energy be delivered to the battery?
I think I recall FLA absorption level being around 14.4v and float around 13.8v for a multi-stage voltage regulator/controller.
so yes, 13.8v means there would be less power V*I being delivered to the battery, but it would still be charging the battery and would eventually charge the battery.


Thanks

You might think that even at 13.8V float there would be some charge going into the batts.

However, by looking at the voltage-current graph from a 100W panel into a 240Ah LFP bank using an MPPT controller (Votronic MPP165) it shows that the charge current immediately stops as soon as the voltage hits the set point of 14.2V. The charger would kick back in once the float voltage of 13.6V would be reached (which didn't happen before sunset):


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(Not sure why I get this extra snippet of meta info and html tags after the pic....)

[john61ct]

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

Originally Posted by guyrj33

John
"Letting voltage drop to Float before that point means the batt will **never** get Full, even connected for weeks."
I'm having some trouble understanding this, perhaps you can offer more explanation for me.
If the charging voltage is higher than the 100% full level of the battery, won't energy be delivered to the battery?

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.

[smac999]

what is the peak voltage of your panel? is it up around 20v or so? if it's lower then that it may just not be a good panel for a MTTP controller.

[daveNZ]

Next time on the boat I’ll measure panel side V and A (while connected to the Genasun GV-4 controller. 4A 50W).

[OceanPlanet]

If you discharge the battery to <12.5V, the Genasun will reset back to a bulk/absorption cycle.

[daveNZ]

Oceanplanet : your answer appeared in the email I received but not here?

But thankyou, that was one of the answers I was looking for. “If the battery is discharged to 12.5V the Genasun will reset to absorption mode.”

If this is true, and absorption mode stops after 2 hours (Genasun specs) then the GV-4 is pretty useless at topping up my battery, in the recommended way of charging g at absorption until .5%C. Unless.... charging at float voltage of 13.5V (approx) does eventually charge the battery???

Guy thinks his battery is charged, with a similar small panel and controller, based on a BM showing 100%, I assume.

I also see about 1 A going into my battery, at 13.5V, when the sun is out, if I am on the boat at the marina and the battery is turned off.

The state/performance of my battery tells me it has not been charged well over the last 2 years, even though it has always been connected to this solar panel. BM history is pretty tame, no extreme or regular deep discharges etc. I could post them if anyone shows interest.

[guyrj33]

John, I think we're talking past each other, comparing apples to oranges.
"However, by looking at the voltage-current graph from a 100W panel into a 240Ah LFP bank using an MPPT controller (Votronic MPP165) it shows that the charge current immediately stops as soon as the voltage hits the set point of 14.2V. The charger would kick back in once the float voltage of 13.6V would be reached (which didn't happen before sunset):"

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