Whynter refrigerator just about killing my battery after 12 hours

[OpenTrackRacer]

I have a new (to me) Whynter FM-45G refrigerator that I'm getting setup for the first time in my Jeep Wrangler JKU. I tested the setup last night and the results have me concerned. I have the fridge set around 34 degrees and I left the Jeep at 10pm with the battery fully charged. When I went to start it up this morning at 10am it started but struggled. I have what's basically a factory Group 34 battery but the marine "deep cycle" version.

It seems to me the battery should be lasting longer than this. If I'm out on a trip and park at 6pm and head out the next morning at 10am I think I could be in trouble. I can't imagine this is normal but... Since it's basically not lasting overnight a solar panel won't help.

Anyone care to comment on if this situation is normal?

Thanks!

 

[plh]

Roughly a 60 amp/hour battery... Discharge time seems about right. Frig draw is approximately 4.5 amps per hour (DC) while the compressor is running. That would be 13.3 hours until dead dead.

 

[OpenTrackRacer]

Right but one would expect the duty cycle on the compressor to be much lower that 100%.

 

[Airmapper]

Anytime you deal with a fridge you are going to need a lot of battery. Your case does not seem unusual.

Using a dual battery setup is not absolutely necessary, but fridges are the reason you see that topic frequently discussed on this board. Multiple batteries start to become mandatory if you plan to power the fridge for longer than a single overnight without running the vehicle long enough to help recharge things, and/or do not have an alternate charging method like solar to assist. (Even then solar keeping up with a fridge can be difficult to pull off.)

I have a small (Indel B TB18) fridge and get by with a single starting/house battery, but it is a Group 31 with 100Ah capacity. In it's final months even it stopped being able to last the night and I had to buy a new one recently.

As plh calculated for you it seems you don't have quite enough battery to comfortably last that long, you are on the edge of the limit. When you run a fridge, the actual fridge is only half the expense and consideration in the install. I easily spent 1.5 to 2X what the fridge cost on the supporting infrastructure behind it, namely a big, high amp hour battery and I had to install heavier gauge wiring and connectors to get suitable power to it's location without incurring voltage drop with further exacerbates keeping the fridge online. Fridges are like a whole thought out install thing, not a drop in add on. But there are multiple ways to go about handling it.

Since I do take my chances with a single battery setup, I always have a Lithium jump pack on standby, and not a wimpy one either. However, the safety cutoff on my fridge has proven to leave me enough to go ahead and start the engine. It's not happy about it but it will do it. (This was when my battery was nearing the end of it's life and was starting to not hold it's own overnight and into the following day.)

You can probably make your setup work a while for the meantime, but you'll likely need to be getting that engine started first thing in the morning.

Right but one would expect the duty cycle on the compressor to be much lower that 100%.

He's also likely assuming your battery is healthy and actually capable of 60Ah. When figuring stuff like this, always calculate for the worst case scenario. Assume it is going to run 100%, what if it's a warm night? Pad the numbers against you and if you can pass that with a safety margin, it might work smooth for a time. This is not a area where good enough gets by. You need a little more than enough and then maybe, just maybe, it might not give you grief.

 

[plh]

Right but one would expect the duty cycle on the compressor to be much lower that 100%.

Duty cycle, ambient temperature and how much stuff in the frig (thermal mass) all come into play. I have 2 group 31s (roughly 100 amp/hour each) and 300 watts of solar in my camper. Edgestar 45 (same as Whitner) and a few LED lights, heater fan occasionally are the main power consumers. You need more battery.

 

[jadmt]

seems off. I have a jeep jkur and stock battery and can leave my ARB 50 plugged in set on 32* in the heat of summer and 24 hours later spins right over no problem.

 

[john61ct]

Get a cheap AH meter and you won't need to guess.

Of course compressor cycling is near 100% for the first day or two if loaded with relatively warm contents.

Run on shore power full of contents for 48 hours get down to colder than the setpoint planned while off grid.

I personally would not try to use any even very efficient fridge on less than one pair of deep cycle GCs at 200+AH.

So called "deep cycle" from auto or big box at 12V? fuggedaboudit, not designed for that.

If remote for more than a day and not driving for 4+ hours a day, add a genny or 300W of solar.

Or buy ice and a 4-day cooler.

 

[luthj]

John61ct is correct. Even a true deep cycle 60AH battery can only be discharged to around 50-40%SOC in moderate temps, and still start an engine.

Those "deep cycle" marine/dual purpose batteries sold at most stores are not really adequate for this type of service. Even at a 30% duty cycle, you are looking at 30AH per 24hr. The whytner units use a fair bit more power as well.

Most of these fridges use less power if they have a decent bit of food in them. Pre-cooling the fridge before putting it on the battery is also important. Starting with a warm fridge and contents it can take 12+ hours to stabilize internal temps.

Amazon has a few cheap AH monitors. You want one that uses a shunt or Hall effect sensor. The hall units are not as accurate, but you can thread your existing battery cable through without doing any big cables.

https://amzn.to/2RezBkV

 

[OpenTrackRacer]

Thanks for the feedback. I'm actually very experienced with 12v power systems, batteries, solar and proper fridge/cooler prep. What really caught me out here was this first test experience versus the real world experiences I see with friends that have the same or similar refrigerators. Most if not all of them are having no issues with a single starting battery lasting ~18 hours with the refrigerator running (usually through their stock vehicle 12v outlets with their corresponding small gauge wire).

The refrigerator was adequately pre-cooled on AC power and has some thermal mass (one gallon of water) but not nearly as much as it would in actual use. It turns out that the battery may not be in as good as condition as I thought so I'll be replacing it and testing again. I have all the tools on hand (amp meter, shut Ah totalizer meter, etc.) to work this issue but I wanted to get some feedback on the experiences of others now rather than waiting.

We usually drive for a while everyday but it's the overnight performance that already was occupying my mind. Solar won't help with that of course. I'm trying to avoid going to a dual battery setup if I can. Modifying the tray to hold a Group 31 battery is an option I've been looking at however.

Got a trip coming up soon so if I can't get this to a workable condition I'll just throw the cooler in as before and deal with it later.

Thanks (again)!

 

[luthj]

The other question is: Battery Condition? Age? Is it getting charged well? corrosion in a cable? Loose connection? Lots of variables. Maybe your battery wasn't that low, and the wiring is dropping lots of voltage? What was the battery resting at after the nights run?

 

[OpenTrackRacer]

The battery is a bit of a story... I just installed it yesterday. The two year old Costco Interstate battery that was in the Jeep bit the dust (I'll be getting it replaced under warranty). I had an identical Interstate green top battery sitting in my garage on a trickle charger that I put in. It was out of a friends trailer and I thought it was newer than it is. I didn't find that out until a little while ago. So, the battery could definitely be a factor. I had to run to work so I didn't get a chance to check the voltage this morning. I'll be testing again tonight for the hell of it (with the fridge set to a higher temperature out of curiosity) and I'll get the voltage at the terminals and the fridge before I try to start the engine.

Wires and terminals are good (and there's a new run of 14 gauge wire directly from the battery to the fridge).

 

[john61ct]

none of those are true deep cycling

and just using alt to charge will not care for it adequately

really should use a separate house bank

 

[luthj]

Yeah, interstate are not the best... FYI, 14 gauge is probably a bit light if your fridge is more than 5-6 ft away. It depends on the fridge, but your low voltage cut-out may have that fridge dropping out fairly early. The compressor will pull about 8-10A for a second or so during startup.

There really is a big difference between a true deep cycle battery and most starter type "dual purpose". If I was running a fridge, I would consider some solar, or a good shore power charger plugged in 1-2x a week overnight.

 

[OpenTrackRacer]

Yep. It's just a starting battery. I'm hoping to avoid a dual battery setup due to the space required and the cost. The Jeep is a daily driver and the refrigerator is only hooked up for trips so I'm not concerned with the day to day care and feeding of the battery being an issue. The 14 gauge wire should yield a voltage drop of around 3% with the compressor running. I have to check the number for startup. If I need to up the size I will. The low voltage cutoff was tripped this morning. The Jeep did still start as well, it just wasn't happy about it so everything worked as it was supposed to in that regard.

I'm familiar with deep cycle vs starting batteries and run a pair of 6v T-105's in my RV as the house batteries (with 250 watts of solar to boot). For the Jeep, solar won't help if the single battery isn't enough to keep the fridge running overnight. Again, since so many people are able to do this on their stock Jeeps, Tacomas and Xterras I'm fairly certain something else is going on (like the battery not being as healthy as I first thought).

 

[(none)]

Hopefully the battery is the issue. I've had no issues with my Dometic in my Frontier sitting for 3 days while camping. I was monitoring voltage to see how it'd do .

Also might be worth checking the parasitic draw in your JK. I have a ford edge i'll leave my fridge in too. If i leave the key in the car (it has the pushbutton ignition) with the fridge hooked up, i'll run the battery dead within 12 hours. Take the key out, the car actually goes to "sleep" and the it has no problem sitting for 24 hours.