Batteries older, fridge more inefficient, deeper discharges: Here's my plan

Surfpath

My Trojan L16REB's are now 5.6 years old. They have been pretty good I think.  For 5 years we typically discharged to 70-80% SOC. However, our 11Cu Ft fridge has been getting more inefficient.

In 2012 it was drawing ~1.7 KWH/d, now it's about 2.4 KWH/d (it's also a bit leaky and it's getting a bit small for us). 

Subsequently, over the past 3 months we now discharge to 57%-67% SOC (Trojan's DOD/cycle life chart here).  I am pretty sure this is because of the fridge. I believe we may hasten the end of our Trojans a little if we continue this way, so....

We are looking at purchasing a new, more efficient, slightly larger fridge and have narrowed it down to either an LG or a Panasonic Inverter Fridge. The 2 models that are available to us [we live very remotely - we cannot simply go to Home Depot, everything is pretty expensive to ship in] draw an advertised ~25.6KWH/Month (LG) to 35 KWH/Month (Panasonic). So a little less or more than one KWH/d.

Seems like a good solution?  here are a couple of hesitations:

1) Search: It seems like the Outback "Search" function may not work so well with these new fridges.  Here's the link to that discussion: http://forum.solar-electric.com/discussion/comment/376598#Comment_376598

2) Cost: They are around 50-70% more expensive than a conventional compressor fridge here. Roughly speaking the inverter fridge will cost me 1,850us and a similar feature conventional fridge will cost 1,100us.

The reason for an inverter model is the low start up surge (aside: we don't come close to the wattage max for our Outback, but perhaps this feature will be helpful in the future). They also seem to have less moving parts and therefore last longer than a conventional fridge.  All the conventional fridges here come with a 1 year warrantee, but the dealer has the inverter fridges on a 3 year warantee.

Anyway, wondering what you all thought of this plan. As I explained, I am a little limited in what I can purchase.  I am not keen on a chest freezer conversion at present. But I am keen on raising the SOC's a little.
-SP

mcgivor

The efficiency of the refrigerator probably hasn't changed, but the batteries have, as batteries age they have higher internal losses which reflect in the amount of energy required to change them, I'm assuming you're looking at daily solar input rather than a measure on the output of the inverter with a Kill-a-watt device.

Inverter refrigerators are perfect for off grid reducing consumption considerably as well as not having surge, they do however have a problem with search settings, reference to my system. Price wise it seems in North America the inverter units are on the higher en models only, here in Thailand there are many, ranging in size from small apartment sizes to double door monsters, non inverter seems only available in smaller size these days.

One way around the search mode would be to have a dedicated small low idle 300W inverter for the refrigerator to allow search mode enabled on the large inverter to function, or do a timed shut down overnight. Some ideas.

Did a quick search at on retail outlet here for inverter refrigerators, they carry 50 different models, divide price by 32 to get an idea of US $ just to give an idea. Grid power costs reflect the demand and supply responds accordingly, North America has cheap energy costs and higher disposable incomes.


https://www.powerbuy.co.th/en/catalogsearch/result/index/?q=inverter+cooling+refrigerator&product_list_limit=96

Surfpath

It's an interesting question (whether it's the batteries that are not holding charge, as opposed to the fridge incurring more of a draw at night).

I do know for sure that the fridge is drawing more (I make regular and lengthy K-A-Watt measurements), especially over the last 3 months.

But I have not done the math to see if it is proportional to the increase in daily battery discharge.
Can this be done?

I am sure there are inefficiencies involved at each step. But here's a very simplistic attempt:
 
My Fridge's going from 1.7 to 2.4KWH/d is a increase of .7 KWH/d (but, this is not used all at night, right? hmm)
My 370 Amp hr 48v bank (potential for 17,760 watt hours) is now cycling (say) 12.5% deeper (or 2,220 watt hours).

Rats, not as easy as I thought. But doing the math makes me realize that it's likely both the fridge and the old batts that are at issue.

 

BB.

Also make sure the fridge condenser coils on the outside are clean (no dust bunnies) and if the coils are in the refrigerator walls (no coils on back/under fridge), that the sides have good air circulation too.

And look inside the fridge--Cold air vents clear. Door and gaskets are sealing well when closed. Not making lots of ice (or cooling warm/hot food) when making day to day energy measurements.

-Bill

softdown

Is the ambient air around the fridge warmer this year? More house guests? Change in diet preferences? Somebody turned down the settings on the fridge? Dirty coils? Heavier loads on the fridge circuit starving the fridge of the voltage that it grew accustomed to? 

Random ideas....

westbranch

well you can always get an off the floor in you local seller from GE

http://www.geappliances.ca/en/products/refrigeration/refrigerators/applproducts?s=UGFnZUluZGV4PTAmRmFjZXRzW3tBMEQzNzNENC1EN0E5LTRBMzItOEQwRC0wMjNEOTcxRDcxMzB9XVswXT17MzNFOUZDMTItOTdGMC00MDBELTlCQTUtRkUyREY4NzE1MUNBfSZGYWNldHNbe0EwNzQxRTg3LTQxMjMtNDJBRC1BMEFBLUJEMDI3RTA2NjBERH1dWzBdPXtDMjRFMDBDRC1CREEyLTQ1RTItODg0Mi1FNjM0MEY0MkIwNzB9

the price is in Can $$1,149, so discount that MSRP heavily if you aren't North of the 49 th..

Pulls  ~30 Amps at 25 V when starting,

see my posts http://forum.solar-electric.com/discussion/338363/cotek-1500w-inverter-powering-new-ge-fridge

similar on in Home Depot US$ 849

These models do have a non inverter compressor that reacts like  the inverter type without the cost  $$ and Watts per day!.

PS your rough location would help us understand your local environment...

BB.

Surfpath may be roughly in the Miami Florida region...

-Bill "guessing" B.

Surfpath

**Good News UPDATE***
So I went ahead and got a new inverter fridge.  Made by LG. At 14.5 cu Ft, it's about twice the size of our previous 10 year old Frigidaire.

The "energy star" rating was an amazing 23.5 KWH a Month (disclaimer: the fridge is made in south America so the testing requirements are likely different).

I put the KAW Meter on it.  Over the past 3 days we have experienced around 1.3 KWH/day: but that's with a mainly empty fridge.

The good news is that we have gone from about 3 weeks of  60%-50% SOC each morning, to 80% over the past 3 days.

Hopefully my older batteries (L16 REB's at almost 6 years old) will benefit.

It wasn't cheap, but I am hoping it will give me another year of battery life.
SP

mcgivor

The one downside to the inverter refrigerators is they don't work with search mode on inverters, at least that's my experience, meaning the self consumption of the inverter, 40W in my case, uses more energy than the refrigerator itself overnight. To overcome this, I installed a small inverter to cover the overnight loads interlocked with a relay, the coil of which is powered by the main inverter, then programed a shutdown of the main inverter between 8pm and 8am which transfers all loads to the small inverter, this resulted in a significantly reduced battery capacity consumption.

Surfpath

Hi there.
Right now I am just happy about the new low discharge at night.  I am not too bothered about search.

20% DOD is fine by me.

ps. Random interesting observation.  Per the KAW meter the minimum watts when running was 83 watts (max was 90watts).  Also, when it stopped compressing the draw was 1.3 watts.  Maybe this one will work on search? 

petertearai

yep  sounds similar to my LG inverter fridge 450 l  299kw per year , havnt tried mine on search , but think thatle mess up defrost cycle . Ive given up worrying about inverter loss . i like the lights to come on instantly. and also only relevant from when all house has gone to bed.  

706jim

I used to have my inverter on search mode. I suppose it saved some energy. But now, my old Trace runs 24/7 and standby losses seem insignificant. I'm sure it's less confusing to my fridge electronics. And I sure love having that defrost cycle after many years of defrosting a propane fridge.

solorone

Shame you cannot get to a Lowes.  After being on gas frigs  since 83 I moved to an LG  LTCS20220, it is an Energy Star + tier1 unit.  Not sure it is an inverter, but it was the most efficient I could find, and it was at the top of Consumer reports list.  Did a long test and found that in July in Georgia, it was using less than a KWH a day, I leave my Belkin meter on  counter  beside frig.  Runs at 47 watts.  high point might hit 70 watts.  I have never seen it higher other than on a warm start up. It comes on in stages, soft start, of 70, 150, 300, 500, 700 watts, this takes maybe 7 seconds or so. It makes 6# of ice a day and has made 9/10 in 24 hours. it is an amazing unit. I looked it up for someone  this summer and saw them as low as $785.  I paid $900 on sale last year.  It is 20 CF.  It may  be too big, but you could have it shipped.  I have seen others here on the forum with the same unit. Good luck.

Surfpath

Just a quick update again:

• After a couple weeks of K-A-Watt testing, the new LG inverter fridge pulls about 0.90 KWH/day. Pretty good so far.
  

• The batteries now go from 55-65% SOC in the morning to an average of 80% SOC.  So way less draw overnight.

• My old traditional compressor fridge was donated to a young poor recently married couple who just moved in to a shack (grid connected).