Engel and fridge cooling

Hi IF the battery voltage @ bat terminals is only 12.2 v they are far from fully charged.
Suggest you also check actual voltage @ fridge while running, you could have a substantial voltage loss between bats & fridge.
Low voltage @ fridge could be critical when max operating efficiency is required, also like any fridge they do need good ventilation especially in hot weather.A small fan such as a computer type would assist cooling of the unit.

Hi Ausrtavel
"Will check the voltage at the fridge itself. 12.2 V was at the solar regulator where all three batteries join. Will also double check the fan but believe it was running."

What capacity solar panels do you have??
An engel running on freeze [MAX] will typically draw in excess of 100A/HS PER 24 HRS,ie IT WILL REDUCE 2X100AH BATTS TO 50% CAPACITY IN 24HRS
AS you move it back to a warmer setting the power [amp/hr ]draw decreases , usually running it around 4degs will draw 25<50 ahs per day DEPENDING ON HOW OFTEN YOU OPEN & what warm loads you put into it.
The unit does NOT actually draw more current @ low voltage it just operates so inefficiently [ the swing motor cannot make a full stroke due to low voltage] that it will not reach a set temp & switch "off "so it will run for much longer times doing no usefull work & thus run the bats down.
ANY compressor fridge is a problem with power if you are sitting down for a few days unless you have adequate means of charging the bats which as others have said should be deep cycle types to withstand the hard work.
For long term camping 3ways are often the best way to go. I run both types & have 200a/hrs bat capacity & 200w solar panels & have often had to move frozens to the 3way during poor weather.

Hi
IF you are getting 12v+ AT the fridge terminals & with no signs of heating or excess temp at plug [ which would indicate poor connection & loss of voltage there] VOLTAGE IS NOT THE PROBLEM .
BUT if voltage is 11.5v or lower then that is most likely the problem.
AS said previously you need to protect the fridge from high ambient temps & get rid of the heat from the radiator fins as much as possible.

Thanks Oldtrack,

Set up is one 57 litre (approx 60) combi fridge and freezer, Engel. Three NZ70 cranking batteries in parallel and I can and do bring in the NZ70 starting battery. So for a day or so I have 4 batteries in parallel until the voltage drops to low 12 volts. I have one 80 watt panel that I only use if staying for more than 3 full days. Otherwise I just run off the batteries. Voltage can get down to mid to high 11 volts but that's after 3 days and unusual. Generally voltage is down to 12 as a min.

Voltage just before plug into fridge is approx 0.4V below battery voltage. This will be due to fuses and standard engel plugs. Not sure what it is after the last engel plug it's a bit hard to get access.

I didn't realise ths particular motor wouldn't increase current draw with a decrease in voltage. My understanding from W=VxA is that amps will increase if volts drops to ensure constant energy to the appliance. Are you saying with the Engel that current draw remains constant so wattage drops??

Regards

Hi Austraveller
"I didn't realise ths particular motor wouldn't increase current draw with a decrease in voltage. My understanding from W=VxA is that amps will increase if volts drops to ensure constant energy to the appliance. Are you saying with the Engel that current draw remains constant so wattage drops?? "

W=VA could be interpreted as you have done but that is true only if you know the actual v & amps draw. with out complicating it too much I''ll use a simple electric heating element as an example .
IT has a reasonably constant resistance of 1ohm ,apply 12v & the current will be 12amps . w= 12v x12a =144w.
Drop the voltage to 10v the resistance is still 1ohm but the current drops to 10amps,10v x10amps =100w.
IE a16% voltage drop gives 30.5% loss of power. This why cable size is so important in low voltage systems cable voltage loss can lead to greatly reduced wattage to do the work.[ especially with 3way fridges on 12v]
NOW a little complication is that this does not hold true for electic induction motors under all conditions, BUT THE ENGEL SWING MOTOR IS not AN INDUCTION MOTOR,It is a selonoid type action whose current draw is determined by the#1 applied voltage,#2 the reactive resistance of the winding [ due to normal wire resistance & the magnetic effect of the iron core ,in simple words in case there are any purists reading] & #3 finally the supply frequency. # 2 & #3[which give what is near enough the equivalent of restance areconstant]
SO as in the heater the lower voltage will give actually a lower current & the WATTAGE AVAILABLE TO DO THE WORK ie PUMP REFRIDGERANT IS LOWER than the name plate rating which is only correct @ the specified voltage.
I know this was looong but could not see any way of shortening it.

"QUOTE This will be due to fuses and standard engel plugs. Not sure what it is after the last engel plug it's a bit hard to get access UNQUOTE"
You can get a reading under load right @ the last plug by carefully sticking a pin into each cable & reading from them, also note the plug may have high contact resistance is there any sign of heat at the plug.?
If all is ok then all you can do is improve ventilation, insulate even more, put in coolest possible area.
As someone else suggested it could be faulty[ loss of gas , clogged line etc , the easy way to check is run it on 240v .

Hi OT,

Thanks for the electrical lesson. So when or for what equipment do you see current increase as volts decrease to ensure wattage is the same?

Sticking pins in is what I did to get the 0.4v drop. The plug seemed ok temp wise. However I intend trying to get access after the plug. Strangely there is a 0.8v drop when using the earth wire inside the cabinet. Ie pin in positive wire before plug and earth wire from motor to cabinet. Now I believe there's a bit of trickery in the electronics to invert the voltage. Not sure if this is why I'm getting such a voltage drop using the earth wire at this point.

That's the thing when using 240v or over night with the fridge running flat chat on 12v it will pull down to -18 to -20 deg C. So my thoughts where that either the compressor can't keep up in the heat, ie to many losses through the cabinet. Or it can't remove the heat from the condenser in high ambient temps efficiently.

Re-reading the first post I didn't put this in. What's it about assuming.

Hi Aus
"So when or for what equipment do you see current increase as volts decrease to ensure wattage is the same? "

In simple circuits rarely ,however electronic circuits can be designed to do just that, if required, to cope with normal voltage fluctuations, but obviously have a design limit .ie If voltage falls to zero then there is no voltage to drive the system.
A simple devise that was used for many years to maintain near constant current[not an increase in current]where special iron filament bulbs whose resistance increases in a near linear form ,over their designed range ,ie as voltage increased current increased , resistance increased current decreased. similarly if voltage dropped, current dropped, Resistance dropped current increased.
This can be seen in any light bulb, measure its cold resistance & do a watts calculation you will find its actual wattage from those reading is many times its rated wattage as it heats up the resistance rise rapidly to give its final working temp & wattage This massive initial surge current is the reason light bulbs OFTEN fail @ switch on.
AC equipment incorpoating any form of ferrite [iron ] have an inductive effect which has a limiting factor on current, the effect is also frequency dependent ,@ lower frequencys more current will pass or be drawn by the devise, higher less current.
Electric INDUCTION motors current changes according to load[higher load = higher current] but if voltage is low[ LOW POWER OUTPUT] & they loose speed they will not generate what is called back emf [voltage ] & their current will rise dramaticaly Again measure the resistance of any motor, ac or dc,& do watts calc,YOU WILL SEE A SIMILAR RESULT TO THE LIGHT BULB.

Now back to your orignal problem, I wonder what the temp in the vechicle is ,the efficiency of the refrigerant certainly drops off with temp rise as it leaves the condenser[ thats why good cooling of the condenser is so important on ANY fridge. I think from memory that most compressor fridges with new gas requirements start to loose their ability around 40deg C & CERTAINLY THE RUNNING TIME WILL ENCREASE DUE TO THIS LOSE OF EFFICIENCY AS WELL AS DUE TO HAVING TO COPE WITH HIGHER CASE TEMPS ETC.
MY Engel has coped with near 40degs but I have insulated with 25 mm of polyeurethane all round[ top, bottom, sides.]
We did a trip wth temps in that range many years ago around Aus in an old toyoata with no aircon OUR one saviour was icy pole ice blocks with which we could have made a fortune as we pulled up @ such place as HAMMERSLY GORGES , the Olgas etc.
We were approached from many wanting to know where we got our ice blocks, did we have any to sell etc , all in our ENGEL
I do believe the now illegal gas may have been more efficient in high temps.

Hi Aus
"Strangely there is a 0.8v drop when using the earth wire inside the cabinet. Ie pin in positive wire before plug and earth wire from motor to cabinet. Now I believe there's a bit of trickery in the electronics to invert the voltage. Not sure if this is why I'm getting such a voltage drop using the earth wire at this point. "

I'll have to see if I can find my old wiring diagrams to check that out but from memory neg & earth should be common & that may be the answer [a fault in the plug or socket].
WHEN your 80 the memory does loose a few things.

Hi OT,

Would appreciate it if you can have a look at a wiring diagram and let me know if it is a common earth. If so then either there is a large voltage drop across the plug into the engel or losses through out the inverter etc, etc.

Hi Aus
I can not find my Engel diagrams , must have put them in a safe place during a senior moment.
I have checked on my 2 Engels & found there is no direct [common] connection between frame & neg. There does appear to be a capacitor between frame & neg which could be responsible for the reading you are getting[ very low leakage will show on modern high sensitivity meters.]
Back to base possibilties are:-
loss gas, a crackedpipe as most likely cause ,it can happen with severe vibration.
Though you appear to have sufficient voltage does it have healthy 50cycle/hertz hum. could indicate faulty inverter.
Somtimes if stored for a long period the the system can get a blockage.
Inadequate cooling of the condensor.
faulty lid/ door seal .
SIMPLY TOO HOT TO COPE bearing in mind that performance does fall off@ high temps.
A faulty swing motor

Thanks OT,

I'm not as senior as you and trust me have far to many of those moments lately.

Thanks for all the suggestions, some I've checked but will work through the rest. Yes the hum sounds ok, even though my technical field is mechanical (thermo, energy etc) it sounds ok to my non electrical ears.

The more I read and consider I feel it's more about not coping. I think the thermal load builds up through the day and it simply can't get rid of it. I'm sure if I could keep the voltage up and concentrate on cooling a bit more it would help. As would making sure it reached min temps over night but that's a catch, uses more current doing so.

Will let you know what I find.

Thanks again for the help.

Hi Bungarra,

At 12.2V the current draw will be higher but I thought the Engel's could handle much lower and still function respectably. Yep it reduces battery life but it's a trade off.

Here's my situation. Sitting in the one spot for 3 days, bar a quick run to check the pots. Approx 300 Ah in 3 cranking batteries, I know not the best but let's assume this is approx right for this case. I even bring in the main cranking battery for a bit, so that's 4 NZ70's I carry. Over cast sky so no use putting out the panel. Not using genny as NP. Therefore after day 1 battery voltage is down to 12.??V

How do you keep the batteries charged under these circumstances? Plus are you saying that the Engel will run colder when bat voltage is at max?

Hi Bungarra,

Just re-read your post and notice you say you heavy cables with no voltage drop. Where did you measure the voltage, after the plug into the fridge? If so how did you do that?

Did you use the supplied engel cables? I used both the one with the two inline fuses and female socket and the one with the male socket to the plug for the fridge. This setup losses around 0.4V. Might be worth taking it all out but even by removing the female/male plug I can't see it dropping back to zero in my case.

G'dday Austravel

Over the years I got sick of all the experts that sold me 12v gear but never really used it or understood it (and left me with hot beer and no power) and so I made a test box so I could better understand what the hell was really going on with current draw, voltage etc of the all the various accessories.

purchased a little black (can get them in grey) plastic box about the size of 2 cigaret packets...empty things used for a multitude of uses..but cannot think what they call them...get them from Dick Smith outlets

anyway I purchased a volt meter and an amp meter and set them into the top of the box. On one end of the box I put a male plug to receive the power and fed it through the gauges and out to and around the other 3 sides I arranged various outlets...2 pin round, engel outlet, ciggaret outlet, anderson, and another outlet that I cant think what it is called at the moment.

the idea was that whatever the acccessory plug arrangement had that I wanted to test had the ability of drawing through my test box....amazing how many times it has been dragged out over the years when campers we have met start telling of their 12v power woes..havent been stumped yet in putting inline for them and at least they can see actuals..not theorys.

So in actual test mode there was still the supplied factory cord between the test box and the accessory under test..........but only that length.........I tapped into the supply line at the far end of the supply discharge...in other words where the acccessory was going to receive the power...furtherest from the battery......I believe the actual voltage drop in the 1 maybe 2 meters of accessory cord supplied was irrelevant and so have never taken that into account

hope that might help you...

cheers

Hi Bungarra,

Thanks for the reply.

"So in actual test mode there was still the supplied factory cord between the test box and the accessory under test..........but only that length.........I tapped into the supply line at the far end of the supply discharge...in other words where the acccessory was going to receive the power...furtherest from the battery......I believe the actual voltage drop in the 1 maybe 2 meters of accessory cord supplied was irrelevant and so have never taken that into account"

I guess in testing like this it assumes the plug into the fridge is ok. Not knocking your process it's just in my case this might be the drama, so will have to try and test the voltage after this point. Your right though, pull everything down to it's simplist and test step by step.

I'll need to check into AGM's when I next change my batteries.

By the way, love your rig set up.

Hi,

Thanks for the detail. I've never gone down the path of deep cycles. If it's a true deep cycle and not a hybrid then recharging times are an issue. I believe even an AGM deep cycle has a much longer charge time than the cranking battery. If it's charging quickly it's most probably a hybrid. I've heard the same about discharging cranking batteries and longevity. However the last lot of Cat cranking batteries lasted around 10 years of deep discharges. I'm sure they can fail quicker but maybe the better ones can handle it for longer.

Mine is a 60l combi and I think amp draw is over 4amps.

Are you sure at 50% discharge your battery is still at or over 12.4v?

Do you find it takes a long time to charge your deep cycle agm?

Thanks

I thought AGM's accepted charge faster than lead acid batteries??

Hi Austravel

havent kept specific records of all the settings but what I can tell you that my 2x100ah AGM are currently showing 46% SOC and 12.06V.

As for charging time quite frankly I dont take a lot of notice....they are either being charged by the alternator whilst driving or the 4 x 75 watt panels do the job...never had an issue to date

cheers

Thanks Bungarra.

John Vic), I've been told that cranking AGM's charge very quickly but deep cycle AGM's are typically slow. This is due to construction. But just because this is what I was told doesn't make it right hence my question to Bungarra.

Hi Aus
Bungarra's post 9of 9 is very good [except for the current draw encreasing as the voltage drops . The actual current demand of the fridge {amps} will decrease but due to inefficiency the total draw { amphrs } from the bat will encrease.]TAKE NOTE OF HIS COMMENTS TOO.

oldtrack123

thanks for picking me up on my current draw explanation

cheers