Part of the issue is that it is not as if the fridge is turned off and the battery allowed to accept the full available current of the Limited solar panel wattage
And it is the hottest part of the day when the fridge runs the most and consumes most of the solar's current in its sweet spot for power generation. So 5 aqmpa generation at noon, well say a conservative 25% duty cycle on the fridge, 15 minutes per hour total the fridge will be sucking up most of that solar current with little or none getting into the battery.
The result is the solar panel never gets the battery to 14.8v and/or does not hold it there for the required time. The battery sulfates, loses capacity, and becomes harder to fully recharge to the maximum of its remaining capacity each recharge cycle where it does not get to the 100% range.
If it does get it to 14.8v, when the fridge compressor kicks back on, the solar cannot maintain 14.8v and the absorption stage is continuously interrupted for long enough that when the sun starts going down, the battery is still far from fully charged.
Some strategies can help.
If driving in the morning and one's house battery is hooked to alternator, crank fridge ALL the way up. Recharge all portable devices when engine is running. If one has another fan, Aim it at the intake vent on the fridge's cooling unit. If one's vehicle has AC, crank it to the maximum. Turn fridge back down, or perhaps off when engine is turned off.
Increase fridge insulation, turn fridge way down or off after breakfast.
or
Turn fridge off and keep door closed until the battery is only in the latter half of the absorption stage and amps accepted by it at absorption voltage are much lower, then turn it back on.
Decrease vehicle's internal temperature by reflectix or insulation in windows on sunny side, and/or more ventilation. exchanging inside air for outside air. 10 degrees more F over 75 can double compressor duty cycle. A fridge sitting in a locked 95 degree vehicle will consume huge amounts of electricity, not only because of the temperature difference, but because the condenser will have that much harder of time venting the heat removed from the box to the atmosphere.
Generally keeping the fridge full will reduce duty cycle if door is opened often.
Make sure the vents on the fridge's cooling unit are not obstructed at all, meaning several inches space around them. The importance of this cannot be overstated. A fridge does not force things cold, it removes heat from them. This heat must be transferred to atmosphere as efficiently as possible, so if these vents are obstructed, the fridge compressor will have to run much longer to perform the same task. The compressor itself also generates heat and even after it cycles off, without good ventilation this heat will soak into the condenser, making it harder for the fan to do its job the next time the fridge cycles on. Also this is a heat source right next to the part one is trying to keep cold. Manufacturers did not really insulate this area as well as possible so ensuring it is no hotter than it needs to be makes a BIG difference in overall power consumption.
In this regard, DIY tinkerers might be able to slip some reflectix between compressor/condenser and fridge box. to reflect compressor condenser heat away from cold box.
The computer Fans also provided with these fridges are also not very efficient, and if designed to pull air through the condenser, instead of Push it through condenser( that thing that looks like a radiator), become even less effective. A 120MM fan like a Noctua NF-f12 consumes very little current(0.05 amps) and is very quiet when pushing air through a resistance, and has a very high static pressure rating for its CFM. When I replaced the 0.12amp 72cfm puller fan provided with my fridge, with the Noctua NF-f12 pushing, there was an instant improvement in duty cycle, and the quieter fan's amp draw was decreased by 60% at the same time. Win win.
One could add a second fan over grille on exterior of chest fridge to help improve airflow, again the Noctua NF-f12's 0.05 amp draw is so little that overloading the fan circuit is highly unlikely. It will more than make up for the slight increase in in amp draw Fridges with Danfoss compressors can handle powering 0.5 amps of fans which switch on and off with compressor.
The cooling units on these fridges basically act like vehicle air filters, trapping dust and lint and limiting airflow. Keeping out the lint and dust or blowing/brushing it out makes a huge difference when condenser and fan blades are occluded. The dust is not only a cause of poor fridge performance, they can cause its failure, or cause it to occur much earlier than it otherwise would.
Only refill the fridge with warm items in the coolest part of the early morning, make sure any warm items placed within are not baking hot when interred within.
If one does find their solar controller in Absorption stage and the fridge compressor does not draw voltage down below 14.8 volts, then turn up the fridge colder, until later afternoon when the sun cannot hold it at absorption voltage. Afterwards the fridge will not run or consume as much battery power. This can really significantly reduce duty cycle for the next several hours and take a big dent out of overnight Ah consumption from battery.
Even though LEDS do not draw much electricity, if one dims them to ~85% brightess, they can consume way less than half the amount of current as they do at full 100% brightness.
https://www.amazon.com/LEDwholesale...qid=1475467019&sr=8-2&keywords=pwm+led+dimmer
They are worth it just for the ambiance factor.
Strategies can also be developed to retrieve food and return food items to the fridge box as quickly as possible. Many people love to leave the door open while they pour milk or something, and this is unnecessary and insures more battery consumption. Break oneself from stick and brick habits.
Some people might leave something cold on the counter for 15 minutes after they dispensed the item within, and only then return it. More heat the unit must then remove. Return cold items back into fridge ASAP with as few door openings as possible.
The easiest solution, is simply more solar, if possible.
When the battery is most depleted, is when battery charging is most efficient, which is why I recommend a well wired alternator, and driving in the morning when battery is most depleted, if one has to drive. If later morning, then the solar will have replenished some of the battery and it will not accept as many amps from the alternator as it otherwise would.
I do not recommend idling, unmoving to recharge unless one knows their alternator is not approaching 220F. This can happen quickly on some vehicle platforms when recharging depleted batteries which ask for everything the alternator can make.
I have found even moving slowly( 15 to 25mph) at low engine rpms spikes my alternator temperature when it is producing more than half its rated output. Highway speeds, no issues maxed out.
No sense in destroying an expensive alternator trying to extend the life of the battery.
The goal is really to get the depleted house battery to absorption voltage as early in the day as possible to allow the battery to spend as much time as it needs each day to get to 100% charged. Once absorption voltage is achieved, the amount of amps required to maintain it keep dropping, and these extra amps can then be used to charge portable device batteries, or charge the fridge, by making it colder when there is the solar surplus.
When a battery goes several days being worked hard and not quite fully recharged, or perhaps not even close, it gets punch drunk, and becomes much harder to sober it up. When punch drunk, The absorption stage of holding 14.8v, will need to be held for much much longer for it to recover and actually reach full charge. Often longer than the day is long.
If at this point of punch drunkedness ,it still is not recharged to its maximum possible remaining capacity, and cycling begins again, that possible capacity regained from the true full recharge, is gone, forever, and it will become harder and harder to recharge the battery to whatever diminished capacity it now has remaining.
It is like a balloon whose skin gets crusty and less elastic and more full of pinholes unless it is regularly stretched out to its maximum size.
With this diminished capacity, and without using less electricity from it overnight, it is being cycled deeper each time, which reduces capacity even faster, and the problem compounds until "my battery no longer accepts a charge" WTF? Argggggghhhhh!
The battery is still taking a charge, but it simply has no room left to store it, and small loads and the voltage tanks and things stop working.
This is the big issue with lead acid batteries, and why the 100% recharge is so important. Does the 100% recharge need to happen each and every recharge, of course not, but it is better if it does. Much better. One can get several hundred worry free cycles if it does. if it does not one is lucky to get 150 cycles before "WTF!!!!!! ArrrrrggggggggggGhhhhhhhhhhhh!!!!!!"
And if one knows they have gone several days without the true full recharge, efforts to achieve it should be pursued, or one should expect to kiss some capacity good bye, forever. the longer one goes the harder it is to not only recharge the battery but the more likely it is that the capacity is unrecoverable.
Being able to plug in overnight not only allows a true full charge to occur, it gives the battery a rest.
Equalization charges of 16v applied only after a regular extended absorption charge, can restore some capacity that might appear to be gone forever, but these are fairly labor intensive and results are NOT guaranteed. 16 volts should not be allowed to reach 12v devices, and 16 volts is not so easy to achieve without proper equipment.
One does not have to obsess to get maximum lifespan from a lead acid battery, but neither should they expect it to just recharge to its maximum capacity at any point after it has been worked hard and chronically undercharged.
So, in Summary, Seek and Hold 14.8 volts should be a goal daily. How long to hold depends on what time of day the solar gets it there. If at 2PM the fridge compressor kicking on pulls it below 14.4v, consider turning off fridge for a little while.
