Will a small solar regulator actually charge a house battery

[OceanPlanet]

Originally Posted by 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.

To clarify...the Genasun bulk/absorption cycle is to continue to charge as fast as it can, until the bulk/abs voltage is reached, BEFORE starting the 2hr timer for absorption. So, several hours are spent just trying to get to the target voltage, when nearly there but not quite. So the batteries DO wind up quite fully charged before the controller goes to the Float voltage.

[guyrj33]

Originally Posted by OceanPlanet

To clarify...the Genasun bulk/absorption cycle is to continue to charge as fast as it can, until the bulk/abs voltage is reached, BEFORE starting the 2hr timer for absorption. So, several hours are spent just trying to get to the target voltage, when nearly there but not quite. So the batteries DO wind up quite fully charged before the controller goes to the Float voltage.

Thank You

[john61ct]

"Quite fully charged" is imprecise, as is any eggtimer based Hold Absorb time.

I've worked with many banks that need 3-4 hours Absorption time.

And of course concurrent loads can sap the amps rate into the bank.

Really the Hold time. should be adjustable based on your unique (and often changing) usage patterns, so you can ensure *actual 100%* Full, as per trailing amps, at least a few times a week.

[OceanPlanet]

Originally Posted by john61ct

"Quite fully charged" is imprecise, as is any eggtimer based Hold Absorb time.

I've worked with many banks that need 3-4 hours Absorption time.

And of course concurrent loads can sap the amps rate into the bank.

Really the Hold time. should be adjustable based on your unique (and often changing) usage patterns, so you can ensure *actual 100%* Full, as per trailing amps, at least a few times a week.

All true. Although note that at the typically slow solar charging rate, the batteries will spend a fair amount of time near the abs voltage, while the solar tries & tries to get it there. Could be only an hour (if batteries were nearly full to start with) or if some light load could be all day long >14V without ever actually kicking back to Float.

[john61ct]

Which would be a good thing right?

Premature infloatulation being much more common. . .

[OceanPlanet]

Originally Posted by john61ct

Which would be a good thing right?

Premature infloatulation being much more common. . .

;-) Yes indeed.

The slower the charging, the more time is (effectively) spent at abs, as it already took so long to get there at the low current. If charging Pb with big alternators, the target voltage could be reached almost immediately, and the current could still be significant even after 2hrs.

[daveNZ]

Today I finally saw the Genasun charging at about 14V and 1.5A. It was sunny, and I had engine charged for 30 mins at 14.3-14.4V. No loads. I think the real problem is a 20W panel can’t provide enough power for the Genasun to magically push the battery to 14.4V even though the panel side voltage is about 18V. I think I assumed it would, if the battery was fully charged. (i.e. for the nominal 2 hours of absorption)

I have a Victron BVM 700 (wish I’d gone for the 702). Is a Victron mppt controller the obvious controller to upgrade to if I add say, 200W of solar? I might have two x 45W fridge&freezer. (Please don’t add comments re batteries. I’m well aware of what I should have, and there are plenty of threads on this.)

[GTom]

Fridge+Freezer running 24h, autopilot, etc could keep even 500W solar busy. These things don't run even near their maximum power whole day. They're mostly sitting at a non-ideal angle, partially shaded. On top of that, on the tropics (=lots of sun) efficiency goes down because of higher temps, at higher latitudes you have more clouds.

[john61ct]

Plenty of folk run a portable fridge at beer temps off 200w even in high ambient temps.

But freezer usage is a **much** higher load, double easy depending how "food safe".

wrt SC brand, there's 8-10 very reputable vendors that make great products, efficient and featureful.

But Victron gives you all that plus marine robustness and fantastic warranty, for a ~200w setup in the 75/15 for around $100!

$20 more gets you the full dongle adjustability built-in, future ready for LFP one day.

Best panel match would be higher voltage, gives the MPP functionality more headroom, nominal 24V is around 40Voc, but could safely go all the way to 65V, many great choices at low $/W in bigger house system grid-tie sizes.

Maximum charging power output is 220W or so, but overpanelling to ~250 (or even 300 if you got a great deal on a big panel) would increase average output overall in suboptimal conditions. (Double that for a 24V bank)

But even for just 200W in a 12V nominal panel (~20Voc), well worth $100.

Another nice thing small cheap SC does, is allow for low panel:SC ratio, even 1:1, which is ideal for handling partial shading.