Fridge and battery/solar panel size

[Dieseldragon]

In the end, I have decided to leave the fridge project for next year. After adding up the cost of everything needed for a fridge that would only be used for a few weeks

 

[Richard10]

Bit late to the thread, but I am running a similar set-up - 2x100W flexible solar panels which at best will push in 5A a piece, with a 100Ah battery running a 40L Waeco fridge, which pulls 5A. So whilst my Solar may give me on a lovely day realistically 8 hours of light at probably only 3.5A, my fridge running 24 hours a day is smashing 120Ah a day. . .which explains recently why a trip out to the bush for a single night quick camping meant my fridge died halfway through the night. I did pull a spreadsheet which pretty much tells me after a single night my battery would be flat and really hoping it wasn't going to be the case, but alas. Damn maths! Think if I run two 100Ah in parallel as leisure batteries I should be good for at least a day or two. Spreadsheet is at http://www.campertrailers.org/solar_spreadsheet.htm if interested.

Some thoughts on my overland experience running a fridge/battery long term. My 50L Waeco c/w insulating cover draws 5.3A and at 40C is running 55% of the time. I found that having only a single 100Ah leisure battery under those conditions even with an 80W panel is just not sufficient to power a fridge from dusk to dawn. Using round numbers you will have 14+ hours of no solar input (probably more) so 14 x 5.3 at say 30% duty (cooler at night) will consume at least 22Ah.....and that assumes your one battery is fully charged. a 100Ah battery will be at least 22% discharged in the morning even if you exclude other power drains like pumps, chargers, lighting etc. It could easily be 30% discharged. This is not a function of the amount of panel watts - you can only fully charge the battery - it is a function of the battery capacity. We constantly discharged our 100Ah like that and knackered it pretty quickly. This year we will be on 2x 100Ah and we have upped our panels from 80W to 180W. Your 100W panel is only just delivering 8A in full sun - fridge will take 5.3A x 55% average, so 3A leaving only 5A to top up the batteries, power other circuits etc.....if it is not full sun or you are in shade etc then you may not get any net top up charge at all. I can run both my panels off the truck so that I can park in shade to keep it cool and yet put the panels in the sun and optimise their angle to it. I use an IBS split charge controller and the fridge has a low voltage switch off. Temperature management is vitally important - e.g. keeping the truck ventilated when parked up, re-stocking the fridge with cold beers or cooled from a river or cool night temperatures. If you plan to travel in the UK and for weekends only then you may get away with a single battery

 

[AndyCook]

The fridge shouldn't draw 100ah in 24 hrs, it won't be pulling 5amps constantly, is the battery OK ?
I had similar issue with a 95ah battery, after I had been using it for 4-5years
It wouldn't last a night without going low

Got a new battery and all ok, albeit a 190ah battery
But I have a waeco 40l running as fridge and 18l runnng as a freezer hooked up to it. It has lasted 48hrs without running engine and still been ok

 

[Richard10]

Hmm, maybe there is something wrong with the battery then . . . the primary starts fine, but maybe there is something wrong with the secondary. Only brought the vehicle in July so unsure of the history of the batteries. They have dates written on them but unsure if they were dates of install or when to be replaced! One is 2016 and the other 2015, so had thought they were install dates.

Both of those running off of a 190 lasting 48hours sounds a bloody lot better than mine!

The fridge shouldn't draw 100ah in 24 hrs, it won't be pulling 5amps constantly, is the battery OK ?
I had similar issue with a 95ah battery, after I had been using it for 4-5years
It wouldn't last a night without going low

Got a new battery and all ok, albeit a 190ah battery
But I have a waeco 40l running as fridge and 18l runnng as a freezer hooked up to it. It has lasted 48hrs without running engine and still been ok

 

[AndyCook]

According to Waeco manual the fridge runs only 13 mins in a hour at 20degc outside temp and fridge at 5 deg
and 18mins at 32 deg c when set to 5 degrees

So worst case it will draw 18% of 5 amps in an hour = 0.9 amps s
In 24 hrs it would be 21.6 ah draw

Unless your Fridge is running constantly ? What temp is then fridge set to and what is outside temp ?

 

[AlexanderVanBaelen]

Most hours have 60 Min and not 100 !

 

[AndyCook]

Most hours have 60 Min and not 100 !

It feels like 100 when you are at work though

 

[AndyCook]

So my 18 mins in an hour , should be 18% running time in an hour...

 

[Richard10]

Hi Andy,
Well the other day it was running at about 2 or 3 degrees with an outside temperature of perhaps 25, dropping over night. Since Im in Ausstralia and we're approaching summer, the outside temp is only going to increase

 

[StarCruiser]

So my 18 mins in an hour , should be 18% running time in an hour...

18/60 x 100 gives 30% run time
5A x 30% gives 1.5 Ah draw in each hour.

Lots of guys have insulating jackets around their fridges to help when in higher ambient temps. It's also a good idea to ensure good airflow round the compressor area and consider an additional PC type fan if needed. Also check the factory fan is running inside the compressor compartment.

 

[AlexanderVanBaelen]

It feels like 100 when you are at work though

I feel your pain!

 

[Shayne]

 

[Richard10]

Well the good news is that the batteries seem to be running fine. Without the engine running the Main Battery is at 12.98V and Second Battery at 12.88V. When running, they have 14.12V and 14.18V respectively. Haven't tried them under a five min load test which I read about though . . . I do have two solar panels installed running into a CMTP02 Solar Controller (Looks like a cheap controller to me - I didn't install it, blame the last guy) which when I tested the voltage coming from the solar a few days ago was whacking out a whopping . . . 0.77V. So I think I have found one issue anyway. . . or rather, I've found another issue.

 

[AndyCook]

A new solar controller should be cheaper than a new battery at least
Good that you tracked down the issue

I use the controller on my ctek d250s

 

[Richard10]

I use the controller on my ctek d250s

Think the Ctek d250s is the ultimate, it's what I've been coveting for ages anyway. However, I do have an old battery isolator working already (well I say working, it seems to be, which is no guarantee of anything! ha ha) and the CTEK does have the drawback in that it doesn't tell me current out/in. Was thinking of ditching for something else . . . but how have you found it?

 

[AndyCook]

I have found it good, and I use a smart pass unit with it too
Which makes Charging faster and more efficient

And also got a mains ctek charger to use with electric hookup if I need it at home or at a camping ground with electric hookup

I've wired up a amp/voltmeter with a shunt to show me how Many amps and volts my panels generate

 

[Richard10]

I have found it good, and I use a smart pass unit with it too
Which makes Charging faster and more efficient

Yeah I was going to ask if you got a SmartPass too, but you have an awesome set there. I have mains hook up already and was nosing around to see if it actually charged batteries too when plugged in...theres a minefield of wires in this landy!

 

[Richard10]

So....more crap news. I tested out the solar panels directly at the junction box and seems I am not getting entirely the voltage I would hope so. See pic. The junction boxes were filled with silicone which made getting at them pretty difficult, but anyway....any suggestions on next steps would be most welcome!