Advice 60 w 12v/240v fridge running in solar/batteries

oldbobsbus · Guru

Advice 60 w 12v/240v fridge running in solar/batteries

brian · Guru

Why run the fridge from an inverter?

It will use less energy if run directly from 12v.

A second thought on this... If you wish to use an inverter, then consider purchasing a normal 240v domestic bar fridge, it will be far cheaper to buy and probably won't have much different energy demands.

What you save on the fridge will buy you the inverter and the solar panel with change to spare.

Running a domestic fridge in a Hiace or similar won't cause any problems as you're unlikely to be doing any rough driving.

-- Edited by brian on Friday 13th of December 2013 07:11:56 PM

oldbobsbus · Guru

brian wrote:
Why run the fridge from an inverter?
It will use less energy if run directly from 12v.

Thats a point I guess .. and if I put a microwave in it I can put a notice on it to only be used when connected to external power..

Maybe then I could get away with a small 300w/600w inverter for their phones and lappies etc

Oh and just so you know I didn't pay the asking price for it .. smile

brian · Guru

I added another thought to my original post Bob.

No real need to put a note on the microwave, just don't plug it into the inverter.

I'm sure you are aware of the considerations to be given when using an inverter for running multiple appliances.

oldbobsbus · Guru

brian wrote:
Why run the fridge from an inverter?
It will use less energy if run directly from 12v.
A second thought on this... If you wish to use an inverter, then consider purchasing a normal 240v domestic bar fridge, it will be far cheaper to buy and probably won't have much different energy demands.
What you save on the fridge will buy you the inverter and the solar panel with change to spare.
Running a domestic fridge in a Hiace or similar won't cause any problems as you're unlikely to be doing any rough driving.

-- Edited by brian on Friday 13th of December 2013 07:11:56 PM

I do have a small 240v bar fridge I bought at a garage sale a few weeks ago for $20 that would fit in the available space..lol

Thanks Brian now you have me thinking...

I will have a look at it in the morning and see what its power usage is..

oldbobsbus · Guru

brian wrote:
I added another thought to my original post Bob.
No real need to put a note on the microwave, just don't plug it into the inverter.
I'm sure you are aware of the considerations to be given when using an inverter for running multiple appliances.

Thanks Brian smile

You now have me thinking...

Aus-Kiwi · Guru

I asked similar question the other day.. While I'm upgrading solar I'm fitting above what I need .. My old bus conversion had 700 watt and could run fridge Freezer on solar alone
Unless we have more than two days cloudy..
Our Winnebago only has 120 watt..Just good enough for lights.. If I upgrade to 450 / 500 watt and 30 amp reg and double battery capacity I should be fine ..
I cant see the point running a generator for fridge .. Plus when fridge is on DC the thermostat doesn't operate.. Checking fridge specs..
Another thing we'll have to look into.

SnowT · Guru

I want to answer,

But I don't think you would like the answer..
I'm still trying to get all the answer's But I've been pointed in the right direction..

And I think it will have people screaming B@#S$%^..

so have fun..

Juergen

oldbobsbus · Guru

SnowT, You may as well put your ideas up the absolute worst that will happen is I will do it differently..

Sometimes from the silliest ideas comes a solution..

Cruising Cruze · Guru

Hi Bob

I would still have a potable 120 watt panel as well what you can move around Bob depending of the sun
we do everything on 2 portable panels total 200 watt and one 100 ah battery on the moment
and use an 150 watt sinewave inverter for phones and tablets , TV Radio all on 12 volt

Cheers John

moblet · Senior Member

If you take the 12V fridge route you may be able to avoid needing an inverter at all, as laptops and anything USB-powered can be run more efficiently from a 12V source if you have the right toys. Search for "12v laptop charger" and "12v usb charger" and you'll see the kinds of products available. But if I was you and already had a bar fridge that fits in the space, I'd get an inverter rather than buy a new fridge.

Your proposed battery and solar capacities sound more than adequate to me. There is a big performance difference between rooftop panels parked in the shade and portables located to catch the sun; I use portables and reckon I could sustainably run such a fridge on 120W of portable panels, and that's not assuming full sun.

oldbobsbus · Guru

I am a fan of rooftop panels as they are working for you anytime there is sun available ie:- when you are parked in the carpark and off shopping or parked on the side of the road having a cuppa..
The other problem I have with portable panels is storage for them when you aren't using them..

I'm still at the pulling to pieces stage yet so I can give it a good clean up and get it looking a bit respectable...

moblet · Senior Member

oldbobsbus wrote:
I am a fan of rooftop panels as they are working for you anytime there is sun available ie:- when you are parked in the carpark and off shopping or parked on the side of the road having a cuppa..

Unless you're shopping for hours every day or driving places all day to drink tea, times like these are insignificant in comparison to the time you spend parked at camp. Your batteries won't run down significantly while you're shopping, especially if they charge while you drive, but they will run down over days if you stay put and don't collect enough sun. If you camp in the sun or do long drives every day or two then it's no problem, but if you intend to stay put in the shade for days on end then you will need excess solar capacity, and 200W may actually be enough so I'd start out with that and see how it went. You can always supplement rooftop panels with a bit of portable capacity if you find you need it.

oldbobsbus wrote:
The other problem I have with portable panels is storage for them when you aren't using them..

There are lighter, thinner, semi-flexible panels hitting the market in numbers now, and at prices you would have paid for heavy glass-covered panels a year or two ago (which has pushed down the prices of traditional panels). Whether for use as portables or on the roof they could be worth a look.

Herb · Veteran Member

When we lived solely on solar power we used a standard but energy efficient fridge freezer coupled to an invertor. This was a cheaper option than using a 12 volt fridge and also meant repair and parts were far more readily available. Coupled with the correct solar panel output and a modern regulator ( mppt) into good batteries will power a reasonable sized invertor to run anything. My brother has a standard fridge freezer fitted to his van and has fitted panels to the roof ( 4 x 120 watt) with a 60amp mppt invertor and 3 x 120amp/hr batteries. He also has in the back of the van a generator that will automatically start up if the batteries get to low or the draw gets to high and it will bypass the invertor and directly run the load. The fridge cavity was specially lined to improve cooling ( insulated lining). The van has a hatch in the outside at the back of the fridge so he can put a transit block into the fridge for when he is traveling. he runs a 1500 watt invertor that runs like a mains household invertor rather than a portable plug type which he has wired to a marine type switch panel and then into normal wall sockets. he can run anything he likes as long as the combined draw doesnt exceed the maximum allowed by the invertor/ generator. My van has just had fitted another two panels on the roof. I dont park in the shade preferring not to run risk of trees falling on roof and find if I run the roof vent fans keep main hatch shade closed the van doenst heat up to much and panels keep batteries well charged. Everyone has there way of doing things. I like simple and efficient (2495kg van), My brother is a electronics technician and likes his luxuries while traveling (3500kg), My other brother still uses a tent and car battery, lamps and eskys (750kg car). All work, different length arms and deep pockets. Oldbob I would love to build my own like you are, you get what you want and not what a salesman thinks you need.

brian · Guru

Aus-Kiwi wrote:
I asked similar question the other day.. While I'm upgrading solar I'm fitting above what I need .. My old bus conversion had 700 watt and could run fridge Freezer on solar alone
Unless we have more than two days cloudy..
Our Winnebago only has 120 watt..Just good enough for lights.. If I upgrade to 450 / 500 watt and 30 amp reg and double battery capacity I should be fine ..
I cant see the point running a generator for fridge .. Plus when fridge is on DC the thermostat doesn't operate.. Checking fridge specs..
Another thing we'll have to look into.

I get the impression from the above post that you are using a 3 way fridge.

If that is the case, forget any idea that you may have of running it electrically, either 12v or 240v, whilst off mains power and stationary as you will kill your batteries.

Even the smallest of the 3 ways utilises a 120w element which will draw a continuous 10 amps on 12v, and a bit more via an inverter when on 240v. The bigger units can be double this.

Your 500w of solar will, at best, give you about 2500 watt hours (Wh) per day, the fridge, if it has a 120w element, will take around 2200 to 2300Wh, leaving practically zilch for any other loads.

This means that even in good weather with excellent insolation, your batteries will go down hill daily.

Always better to run a 3 way on gas when stationary with no mains power.

oldbobsbus · Guru

Progress report..
I have purchased one of these..

http://www.ebay.com.au/itm/220810092263?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and 2 of these.

http://www.ebay.com.au/itm/181270863875?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

and one of these.

http://www.ebay.com.au/itm/171173619864?var=470305681108&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

That way I can be confident that the fridge I got at the garage sale (90w) will do it easy on the inverter and it will also run many extras if required..

I will post a couple of pix of the progress when it is all in place..

SnowT · Guru

ok bob..

From what I have had pounded into my head in the Last few week's..

- an AGM you can only use 50% of the Battery Capacity.. so try doing what I did work out the load you have and the charge you expect to get.. and then times by a factor of 2.25..[0.25 is margin of error]

for example.. I worked out that my expected load was 200Ah + so I needed a battery of over 600Ah to cover my expected.. load.. that is 10 Batteries.. Nearly $4000 of value and over 400kg of weight..
- Expected life of 3-5yr's maybe longer if I treat them right..

That idea has been thrown out..

Juergen

brian · Guru

SnowT wrote:
ok bob..

From what I have had pounded into my head in the Last few week's..

- an AGM you can only use 50% of the Battery Capacity.. so try doing what I did work out the load you have and the charge you expect to get.. and then times by a factor of 2.25..[0.25 is margin of error]

for example.. I worked out that my expected load was 200Ah + so I needed a battery of over 600Ah to cover my expected.. load.. that is 10 Batteries.. Nearly $4000 of value and over 400kg of weight..
- Expected life of 3-5yr's maybe longer if I treat them right..

That idea has been thrown out..

Juergen

That's one heck of a daily draw Juergen.

Can you post up the sums that you did to arrive at that figure?

Not sure where you got your prices or weights. I have 675Ah of floodeds in my van, made up of 6 x 225Ah 6v batteries for a total weight of just 168Kg and all up cost of around $1100. My expectation of their lifespan is around 10 years.

A 100Ah AGM will normally weigh in at about 31Kg, so 6 of will only be a total of 186Kg. They cost around $300 each, so that's just $1800 in total. Way short of your figures in both instances.

It's also not correct that you can only use 50% of a battery's capacity, you can take it down to 20% Soc (80% Dod) quite safely, you will just reduce its charge/discharge cycles very rapidly to a point where it is no longer a workable entity.

The 50% rule is a rule of thumb where the cost per usable amp-hour versus cycle-life of the battery is at its most economical.

What this means is that having more capacity to keep the Dod lower will cost you more to supply that capacity, and conversely, having less capacity will result in deeper Dod and consequent early replacement of the battery, thus resulting again in more cost.

Hope this helps.

SnowT · Guru

Ok Brian..

As I said my Expected Ah load for the 24hr period is 200Ah..
- That figure was derived from 2000wh per day[minimum]
- (2000Wh * 4[days] / 24V) / 0.7 * 1.1[efficiency] = XXX .Ah.
using this formula I get 192.5Ah of Batteries..

As You can only safe discharge the batteries 50%
double that figure and add a little extra to be safe..

192.5 x 2.25 = 433.125 Ah.

so the nearest combo is 480Ah.. 24v =

so there fore 8 x 120Ah batteries.. At a Bare minimum..
Fullriver 120Ah 12v
So 8 x $368 = $2944..
8 x 37kg = 296kg..

It probably does not help that I'm looking at running predominately 240v for most of the loads..

Juergen

brian · Guru

SnowT wrote:
Ok Brian..

As I said my Expected Ah load for the 24hr period is 200Ah..
- That figure was derived from 2000wh per day[minimum]
- (2000Wh * 4[days] / 24V) / 0.7 * 1.1[efficiency] = XXX .Ah.
using this formula I get 192.5Ah of Batteries..

As You can only safe discharge the batteries 50%
double that figure and add a little extra to be safe..

192.5 x 2.25 = 433.125 Ah.

so the nearest combo is 480Ah.. 24v =

so there fore 8 x 120Ah batteries.. At a Bare minimum..
Fullriver 120Ah 12v
So 8 x $368 = $2944..
8 x 37kg = 296kg..

It probably does not help that I'm looking at running predominately 240v for most of the loads..

Juergen

Can you explain that formula a bit for me as I have no idea what some of those figures represent?

Also, what figures for your appliances did you use to get the 2000Wh/day number?

You appear to have allowed for no charge input in your figures, and it's highly unlikely that you will get none for 4 days.

Using 240v appliances adds a bit to the daily draw figures, but I fear that you are grossly overestimating your needs.

Ultimately it's your choice, just trying to help here.

oldbobsbus · Guru

Juergen,

I have a feeling you are trying to cross tooooooooo many bridges before you come to them mate, why don't you just concentrate on getting your unit here and then one at a time do to it what is needed to get it the way you want it..
For instance on the MH we travel in I have 600w of 24v solar on the roof that takes up 2.5m x 1.6m including brackets now are you going to have that free space available..
I have 4 x 200ah AGM batteries that take up 950 x 500 floor space and they are 250 high and weigh 260kg's
I run my 240v 320l fridge 24/7 through a 1500w/3000w Pure sinewave inverter and when I want to use the microwave or the washing machine as well I change over to the 3000w/6000w inverter that weighs 40kg's IF I use the BIG inverter all the time it uses toooo much power out of the batteries and unless it get full sun most of the day most days I have to connect to shore power to bring the batteries up again.
The point I am making is that all of these things take up a lot of room and and consume lots of your available weight.. having worked on a Coaster or 10 over the years I am wondering where you are gunna put everything and what it is going to weigh when you have finished..

Maybe when you start fitting your bus out and are standing there looking at it you will find you will have to do it a little differently to what you would like to do..
Just a thought go and have a look at a few Coaster buses that are for sale and you will see that they don't have a lot of storage space available for fixed thing and still leave space for the other stuff you want to carry (like tools and sundries)

Just saying...

oldbobsbus · Guru

To date I have converted 6 school buses to motorhomes and each time I just start at the start and end at the end, each one is different in the way they get done but they are now all out there with a happy GN behind the wheel..

This current project just needs a BIG clean up and things fixing and a few extras fitted to make it more user friendly..

oldtrack123 · Guru

HI Juergen
I think you should take Old Bobs advice
You certainly need to reconsider your load weight & energy requirements
2kW per day is very high for a small motor home.

You would need at least 700W of solar just to replace daily use ,with no allowance for those bad days

PeterQ

SnowT · Guru

To get the Whr's etc I used the formula's from..

formulas

So you can see where my number's came from..

Juergen

mr glassies · Guru

got excited then bob saw the van come from bundy i thought you lives there so i looked at ya profile na .
ok my story so far on my roof i got 800 watt of solar . unfortunately i bought mine just before research was done on flexible ones and could have saved weight . my panels are 14 kgs each and the flexy ones are half that but ya get that . i only have 2x6 volt 200 amp batteries they weigh 48 kgs each.
now i have one of those fridges only it 210 ltrs and as i stand now it runs on 12 volt of the batteries and only 2 panels as i havnt got a big enough controller so im pushing 23 amps at optimum input as if haha and it starts at 6 amps and cycles at 4.5 amps . i have 3 fans circulating air in the back bottom vent as the vents are 45% upturn on them and i figured if you pull from the top the air would only hit the fridge half way up and not doing the job. those fans are heat switch activated . there is also 1 fan blows onto the compressor and thats from the factory.
i was told when i got the fridge if it goes kaput i will have to wait for a new compressor (could be ages ) but evakool do a compressor and its readily available so thats that bit . the fridge is gr8 -15 freezor 2/3 fridge and thats on 1.5/2 on the dial.

going bigger batteries when we sell the house and business so we shouldnt run out of power just use it like this for now .

dibs
ps that looked like a good buy on that little camper m8 you just gunna do it up and sell it

oldbobsbus · Guru

Juergen,
Honestly mate I wouldn't be worrying about what panels to install untill you are standing on the ladder beside the bus you buy and see what available space you have to put them..
Also keep in mind that anyone selling items does their darndest to sell you as much as they can hence to overkill on that website you provided a link to..

This new camper will run the little fridge I have put into (thanks to advice from Brian) from the 200w panel and 200ah batteries i have ordered running on the 1500w pure sine inverter, it will also have some spare capacity to run some other smaller usage items and it will be no problem finding the space to put them..

I will feel very confident when I finish this project and put it on the market that the new owner will have a good little gadget to go and travel and enjoy some bush camping..

oldbobsbus · Guru

mr glassies wrote:
got excited then bob saw the van come from bundy i thought you lives there so i looked at ya profile na .
ok my story so far on my roof i got 800 watt of solar . unfortunately i bought mine just before research was done on flexible ones and could have saved weight . my panels are 14 kgs each and the flexy ones are half that but ya get that . i only have 2x6 volt 200 amp batteries they weigh 48 kgs each.
now i have one of those fridges only it 210 ltrs and as i stand now it runs on 12 volt of the batteries and only 2 panels as i havnt got a big enough controller so im pushing 23 amps at optimum input as if haha and it starts at 6 amps and cycles at 4.5 amps . i have 3 fans circulating air in the back bottom vent as the vents are 45% upturn on them and i figured if you pull from the top the air would only hit the fridge half way up and not doing the job. those fans are heat switch activated . there is also 1 fan blows onto the compressor and thats from the factory.
i was told when i got the fridge if it goes kaput i will have to wait for a new compressor (could be ages ) but evakool do a compressor and its readily available so thats that bit . the fridge is gr8 -15 freezor 2/3 fridge and thats on 1.5/2 on the dial.

going bigger batteries when we sell the house and business so we shouldnt run out of power just use it like this for now .

dibs
ps that looked like a good buy on that little camper m8 you just gunna do it up and sell it

Geee Dibs, if I would have known you live up there I would have gone up and got it and paid you a visit mate...

Yep it is just something to do and it is keeping Jenny and I out of mischief..lol..

It is already looking half a chance..

mr glassies · Guru

hence the name bob glasses is for glasshouse mtns lmdo o well next time .
bob if you go the 240 volt with the fridge a little tip m8 cut of the cigar plug connector and put anderson plugs on it i ran mine n 240 on the back deck for 18 mths with the transformer and the only problem was the plug came apart sometimes and lost power but no its in the van its straight 12 volt i even cut of the wires behind the plug on the fridge and connected the main feed from batteries to it and fussed it at the batterie.
dibs

oldbobsbus · Guru

Well there ya go... I have friends that live in Johnson Rd just off the Highway..

I have put the bar fridge in that only runs on 240v..

Here is a couple of progress pix showing before and after..

mr glassies · Guru

hmmmm thats close a bit futher down the road is us lol
just out of curiosity did you change the way the transformer connected to the fridge
dibs