Thread: Solar Reg Output

Originally Posted by garrycol

I found similar issues in a recent long term test I did. 120w panels in full sun, one 50l fridge as load and a MPPT controller - in 24 hours there was a few ah loss out of the system. During the day the panels put in more juice than was needed but not enough to cover night time load from the fridge - so over a week even with full sun the battery would slowly run down.

The MPPT charger seemed more interested in doing it thing in keeping the battery in good nick rather than getting as much power back into the batteries as quickly as possible - to me the software is all wrong as it is a solar charger and should take these matters into account.

I put the regulator on that came with the panels - not smart at all - just feeds power to the battery as it needs it and it certainly got more power back into the battery so its charge would last longer.

What I found worked best was at about 10 in the morning connecting the panels direct to the battery (no regulator) so a full 17v was going into the battery and also getting about 6 amps so getting nearly max watts into the battery. I was told that batteries can take this high voltage for shorter periods as long not left on permanently. I left the system like this for an hour or two and it really put the juice back into the system and then switched back to using a solar charger - this way in a 24 hour period the battery was fully charged by late afternoon and ready for the night time session.

I used Watts Meters on both input and output sides so had a good idea of what was going on.

The battery did not seem to suffer at all.

Garry

Just curious here, but would there be any electronics that would be exposed to the higher volts even though the ignition is off?? (Not sure what type of car u are doing this to)

No car involved - just a camper battery and stuff that runs off it, mainly the fridge that has a range of below 12v to just over 24v.

Originally Posted by spudboy

I have a related question, if I may.

We have a standard 12v truck battery powered by a huge array of solar cells (ex-rooftop solar - overkill but 'free') through a 30A MPPT charger.

It is powering an Engel 39L fridge that is 25 years old.

In the morning, the voltage shown on the battery can be as low as 11.8 or 11.9v, but generally 12.0 or 12.1. After an hour of sunlight, the voltage goes to 14.1 for an hour or two, then back to 13.4/13.5 for the rest of the day.

Is this damaging the battery to go down this low every day? I know that fully charged is 12.7v, but not sure what the lower limit on a lead-acid battery is when this is happening on a daily basis.

Is 11.anything volts doing damage?

Thanks - David

The short answer to your question is yes and no. The best way to answer this is; What you are doing should not kill the battery as such, but it will shorten its life. Even with deep cycle batteries, the more you discharge it regularly the shorter its life.

When I am camping with my solar panels I try to keep the voltage above 12.

Your old Engle will be pulling 4.5 amps, unlike the new ones which use 2.5.

Was about to say "don't all fridges have low voltage cuttoff" but then I reread as I typed and I see your fridge is old... maybe google your model fridge to see if it has the low voltage cuttoff.

All Engels certainly up to 2000 or so don't have low voltage cutouts and I think even the latest don't.
I just buy a Projecta ( lasted about 14 years) or ABR ( recently new but looks the same product) low voltage cutout and place it in the fridge wiring.
The battery going from 14.1 to 13.7 is the controller going from charge to float.
My 120watt cheapo panels , run in series, with 20 metre 12 gauge marine cable, into a GSL 12 amp MPPT controller next to the batteries gives 6.25 amps into batteries reading 12.7 at connection but soon go into float. I like to keep them as high as possible and connect the panels on the first morning.
Regards Philip A

I would have thought low voltage cuttoff was a standard thing on all fridges. We had a waeco YEARS ago that had it....