Thread: Solar Reg Output

Originally Posted by d2dave

Absolutely. If you charge is 6 amps and the load is 2, the balance goes into your battery, in this case 4 amps.

Correct.. Now don't forget..

24 hours in a day.
2amps per hour x 24 = 48amps a day

And don't forget the sun sets but the fridge keeps running!

Now - without moving the panels to track the sun you will get around 6 hours of close to full output (let's assume 5ah to keep the maths simple)

6 x 5 = 30ah made that day.

30 (in) - 48 (out) = -18ah per 24hrs.

With a 100ah to 50% SOC that's just over 2.5 days before it runs out...

Originally Posted by Tombie

Correct.. Now don't forget..

24 hours in a day.
2amps per hour x 24 = 48amps a day

And don't forget the sun sets but the fridge keeps running!

Now - without moving the panels to track the sun you will get around 6 hours of close to full output (let's assume 5ah to keep the maths simple)

6 x 5 = 30ah made that day.

30 (in) - 48 (out) = -18ah per 24hrs.

With a 100ah to 50% SOC that's just over 2.5 days before it runs out...

Yes you probably would struggle without tracking the sun, but I do. Every year for about the last 8 years for a two week holiday, I had no problems running my 40 litre Engle on an N70z battery, providing the sun is shinning.

As for your maths of 2amps per hour x 24 = 48amps a day, this is correct, but a fridge does not run for 24 in 24.

Agree Dave.. Too many factors though...

Temp set at, fridge volume occupied, frequency of opening, ambient temp...

Panel position and angle, geographical location etc.

Engel fridge in normal use I always went 1ah as a guide in warm weather.

Here is someone's test using a shunt and their results confirm it - you can easily bring one down quickly...
http://www.campertrailers.org/fridge...onsumption.htm

Originally Posted by Tombie

Engel fridge in normal use I always went 1ah as a guide in warm weather.

Here is someone's test using a shunt and their results confirm it - you can easily bring one down quickly...
engel fridge power consumption

So working on 1 amp we only need to generate 24 amps per day which my 80 watt panel does easy.

However and I know this varies greatly depending on ambient temp, that on days with average temps around 36 degrees it uses a lot more than 1 amp per hour. Also how often it is opened and I do drink a lot of beer when on holidays.
Come to think of it I also do this when not on holidays.

My solar regulator has a 20 amp load terminal. I have my fridge connected to this. Now the reg at any time can tell me battery voltage, min and max voltage in previous 24 hours, current draw, total amps in and total amps out for the past 24 hours with a 30 day memory.

Now as my memory isn't what it used to be I can't remember the numbers from last holiday in Feb, but I do remember seeing many 24 hour consumptions in the 30's. I will record next February's findings and post them up.

The reg has other features such as state of charge of battery in %. This is calculated by inputting battery size and it then moniters current in and current out. It also tells me the open circuit voltage of the solar panels, usually 20 to 21 volts. It also tells me what time it goes into float mode if the battery obtains full charge.

Also by using a current shunt I have my alternator input also recorded which in the event I run the engine this is factored in to total amps input for state of charge.

Originally Posted by d2dave

So working on 1 amp we only need to generate 24 amps per day which my 80 watt panel does easy.

However and I know this varies greatly depending on ambient temp, that on days with average temps around 36 degrees it uses a lot more than 1 amp per hour. Also how often it is opened and I do drink a lot of beer when on holidays.
Come to think of it I also do this when not on holidays.

My solar regulator has a 20 amp load terminal. I have my fridge connected to this. Now the reg at any time can tell me battery voltage, min and max voltage in previous 24 hours, current draw, total amps in and total amps out for the past 24 hours with a 30 day memory.

Now as my memory isn't what it used to be I can't remember the numbers from last holiday in Feb, but I do remember seeing many 24 hour consumptions in the 30's. I will record next February's findings and post them up.

The reg has other features such as state of charge of battery in %. This is calculated by inputting battery size and it then moniters current in and current out. It also tells me the open circuit voltage of the solar panels, usually 20 to 21 volts. It also tells me what time it goes into float mode if the battery obtains full charge.

Also by using a current shunt I have my alternator input also recorded which in the event I run the engine this is factored in to total amps input for state of charge.

Wow, you must have shelled out for that unit. I got a cheap and cheerful one.... it has a led on the front Red=charging, green=floating. Done. lol. Thanks for the maths on this stuff guys I have never bothered to research all that stuff, I trusted that the solar panel dude I bought my system from knew what size gear to get.

So I was thinking that if these solar charge regulators are very bias to save the battery, can do a workaround? So what I was thinking was before Garry said he bi-passed the controller a couple hours a day to get a good charge going. Now I wouldn't think throwing away the regulator is a good idea, so I was thinking that I would use the "charge wire" as a signal to switch a relay that bi-passes the regulator. I would then get the pull charge capacity of the panel charging up my battery nice a quick

Writing that down makes me think, maybe I am going to shoot myself in the foot here. If the charge regulator sees the high voltage going in then it might drop out the charge, then see a low voltage.... O no....

Originally Posted by debruiser

Wow, you must have shelled out for that unit.

It was $280 back when I got it. They are now $335. Good thing is they are made in Australia, Melb.

When I fist got it I did not have time to install it so I used it portable for my first holiday. I just had wires with alligator clips and would just open the bonnet and rest it in the engine bay.

Nearing the end of my holiday when removing it, one of the wires that should not touch the battery did and fried it. Good thing was that being made here it is repairable. Cost me $90 though which is better that it being a write off, which often happens when made in China.

Unlike my 25 amp Ctek charger. My new dog got hold of it and chewed off the positive clamp which also included the temp sensor. Can't be fixed, no one in Au services them. And these are not cheap.

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