Thread: Upright Compressor Fridge - Solar

Originally Posted by Graeme

I've just hooked-up my panel to a partly discharged battery. When not connected to the battery the panels are outputting 19.6V on a heavily overcast afternoon but the panel voltage drops to 13.25V and MPPT o/p to 13.08V when connected to the battery. This suggests to me that the MPPT controller might be doing a reasonable job of converting panel energy to charging energy.

Your experience is almost exactly the same as mine but when you look at amps it is very low - overall it is all about amp hours in vs amp hours out and my MPPT covers daytime OK but doesn't put enough oomph back into the battery for night time use. The result is that even on full sun days the battery will be slowly discharged over time.

I am using a small 34ah battery for my current tests so that the discharge will be more noticeable than the 100 ah batteries I have in my 101 and camper - last night the battery was at 13v and this morning was at 12v - now if the battery goes back up to 13v tonite that will be great - as it should now as I forced charged it directly from the panels but tomorrow I will leave it on the Mppt and see what the voltage is at sundown.

All I know is that the original cheap crappy solar regulator seems to be better at getting the battery back up to capacity for night time use than the MPPT.

Cheers

Garry

Garry, that's interesting. I take it you have the fridge connected direct to the battery? In light of the info posted above, connecting it to the "load" terminals might fix the issue?

I'm not sure if I've missed something in the discussion, but I understand you are looking at replacing the 3-way fridge in the camper?


Just thought I'd add in the following. We know the heat exchange type fridges struggle a bit when things get warm. I have similar experience a long time back when in Darwin and the caravan fridge just wasn't doing the job. (You can imagine Darwin heat and humidity!)


Anyway, took it out and dropped into the Darwin fridge mechanic. He cleaned and drilled out the gas burner. Worked like a treat after that!(Probably then used more gas than originally intended!?) So maybe, if you are happy to run on gas, something to investigate?


Add to this I've run a SCA (Yep!) 12 volt compressor fridge-freezer in the back of the 4WD since 2005. I did have to upgrade the 12 volt connection from the crappy cigarette lighter fitting to something 'serious', but it sure works well 9 years on


Cheers!

Originally Posted by Judo

connecting it to the "load" terminals might fix the issue?

Night time fridge operation?

I'll check charging current and voltage drop across the charger in good sunshine in a day or 2.

Originally Posted by Judo

Garry, that's interesting. I take it you have the fridge connected direct to the battery? In light of the info posted above, connecting it to the "load" terminals might fix the issue?

As Graeme indicated - yes is an option but not practical as if there is not enough power from the panels the fridge stops.

It just seems to me that the MPPT is not doing what it is supposed to do which is maximise charge to the battery and I don't want to fork out for another one (a better one and more expensive one) only to find the same issue.

Garry

So by using the load output of the reg , once the sun goes down there will be no output if i'm reading that correctly ?

Originally Posted by loanrangie

So by using the load output of the reg , once the sun goes down there will be no output if i'm reading that correctly ?

Yes - and even when a big cloud goes over.

Got up this morning and battery voltage is down to 11.8 v so the battery is well down - in poor sun the MPPT is only putting in .5amps when it should be on full charge as the battery is down.

Disconnected the MPPT and connected the battery straight to the panels - in the same amount of sunlight all of a sudden I have 5 amps going to the battery.

So I think the MPPT regulator is not suitable or is not working correctly and is not providing the right amount of power - might be good charging a battery over a long period of time but not to recoup power used overnight.

Does anyone have a recommendation on a MPPT controller that they know works.

Cheers

Garry

Edit - I just reconnected the cheap controller and in overcast light I did see 6.5amps when the fridge compressor was on and is averaging around 4.5 amps where MPPT was down around .5 - 1 amp.

That sort of seals it - a new MPPT is needed and I will keep the old cheapy as a spare.