Solar Calling all 12 v battery box experts

Axl

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Dec 23, 2014
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Are you saying your fridge is running for 45 minutes of every hour? if you are then firstly you need to put some stuff in the fridge, preferably cold stuff and preferably as full as you can If it were me I would be filling it full of stubbies:encouragement:.
You need to do real time testing you aren't going to go away with an empty fridge are you? An empty fridge will work a lot harder than one with cold stuff in it, some even fill the remaining space in the fridge with scrunched up news paper to help with cooling.
When full you'll find that the compressor will cycle time will be around 20 minutes over an hour, this equates to a third of the hour so a third of 24 hours is 8 hours, 8 hours of compressor run time at 4amp is 32amp this is what your fridge should use over a 24 hour period. As I've said earlier there are a lot of variables involved here, this is only a guide but it should be very close to the money.
We also need a bit more info to help out with your other questions,
  • how olds the van and battery?
  • it sounds like you have 120w of solar on the roof is this form the factory
  • Is the van in full sun during the day?
  • What load is on the battery when the van is sitting?
Assuming the van is in the sun all day the battery should be fully charged, but if it isn't then this could be your problem. Just because your battery monitor says fully charged this may not be the case, batteries need to be held on float for many hours to a couple of days with no load on them to become fully charged.
If I were you I would plug the van into 240v power then plug the fridge into 240v in the van fill the fridge (with beer) ensure the battery switch in the van is on so the Setec can charge the battery, don't draw any power from the battery let it sit like this for 2-3days.
After 2-3 days the fridge and contents will be nice and cold and the battery will be fully fully charged, once these two main factors have taken place put the fridge onto 12v power and run your test, this will be much more accurate than what you are doing now.
As for adding a second battery and more solar if you can afford to do it , do it. When free camping the more 12v power you can carry and harness the better, as you already have panels on the roof id go with a mobile set of panels so you can move them around and catch as much sun as you can.
Lastly you can always resort to a generator if they are allowed.
 
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Drover

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Nov 7, 2013
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For a start don't use the CIG sockets in van, in fact don't use them period for a fridge. My last word is if your killing a battery in hours then something is wrong with the set up......
 
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Axl

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Dec 23, 2014
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Brisbane/Bayside
For a start don't use the CIG sockets in van, in fact don't use them period for a fridge. My last word is if your killing a battery in hours then something is wrong with the set up......
Why not @Drover am I missing something? I use the cig sockets in my expanda both internal and external to run the fridge all the time whilst traveling and free camping.
 
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Drover

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Nov 7, 2013
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Sorry @Axl , I meant for running fridges and high draw units the one's inside your van generally do not have the wiring to run a fridge unless they have been specifically set up as such, they are really lousy connections for anything but a low power unit........In the case of a fridge far better to draw power direct from battery less loss from crappy wiring and the chance of the plug coming loose is high, have come across quite a few pee'd off people with warm tucker or worse, warm beer because the socket came loose.
Many will say been using it for years but it only has to happen once to upset things, never have had a problem with an Anderson or Merit socket coming loose..........40 yrs of experimentation, actually would prefer a Nato socket for outside, will carry the load, secure and waterproof......

I use cig sockets in my van for running the TV, STB and phone chargers, the portable 400 Invertor gets plugged into an Anderson so it gets a good dose of steam to run.....
 
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Bellbirdweb

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Jan 24, 2014
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Sorry @Axl , I meant for running fridges and high draw units the one's inside your van generally do not have the wiring to run a fridge unless they have been specifically set up as such, they are really lousy connections for anything but a low power unit........In the case of a fridge far better to draw power direct from battery less loss from crappy wiring and the chance of the plug coming loose is high, have come across quite a few pee'd off people with warm tucker or worse, warm beer because the socket came loose.
Many will say been using it for years but it only has to happen once to upset things, never have had a problem with an Anderson or Merit socket coming loose..........40 yrs of experimentation, actually would prefer a Nato socket for outside, will carry the load, secure and waterproof......

I use cig sockets in my van for running the TV, STB and phone chargers, the portable 400 Invertor gets plugged into an Anderson so it gets a good dose of steam to run.....
I’ve had very bad experiences with cig lighter sockets as well.

We did a trip through Wilpena Pound and Arkaroola many years ago in a Pajero.

We had one of those cheap little compressors and ended up needing it on a 48 degree day.

The 2 sockets in the Paj both burned out. They had fusible links inside that melted, then the wiring melted.

I now run an Engel connector for the fridge, and Merit connectors inside and Anderson’s outside.
 

Boots in Action

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Mar 13, 2017
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Hello @Les321 , a bit late but just caught up with your situation. An easy rule of thumb on compressor fridge use is the compressor runs for about 40% of the time in real conditions, taking into account opening and closing and adding new (warm) items. So if the fridge draws approx 4 amps the calculation would be as follows:
4 (amps draw per hour) multiplied by 24 hours equals 96 amp hours. But as compressor only runs about 40% of the time, 40% of 96 equates to approx 38 amp hours in a 24 hour period. With this sort of current draw, you definitely have to have 2 batteries (120ah by 2 in parallel) would give you 240 ah capacity. But working on NOT draining your AGMs down below 50% on a regular basis, you are only talking about approx 100ah usable - less than 3 days (at best) from FULLY charged batteries! From some of my earlier posts in SOLAR setups, your solar panels should be connected only through the ONE controller (MPPT) bypassing the controllers on each panel. Hook up in SERIES for max output from your MPPT controller. I use 1 X 200 watt (rated??) and 1 X 180 watt (rated??) portable panels in SERIES (giving me a charging voltage of 30 to 39 volts to the controller) and am able to generate 36 ah easily on a fair day and even more on a good day to fully recover my own usage. That should meet your demands. Your MPPT controller will give you a readout of ah IN and ah OUT for each day so you can monitor your system. I do not have a compressor fridge (but lots of other low current items) and only 1 X 120 ah AGM in my Penguin and so far have had no problems even when off grid for 6 or 7 days. Hope this helps a bit, but there are a lot of variables - ambient temp, whether fridge is shaded or not, amount of sunshine available and if you are able to place your panels in full sun for long periods etc.
 
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