Experiences with running fridge off main car battery overnight for a few nights in a row?

[DaveM]

10.9v is resting volts, but under load its hitting 10.1v

That makes sense, but then shouldn't I have seen the fridge briefly come on or the batt voltage drop when the fridge put it under load? And the bypass should have worked regardless, my understanding is it has no low voltage protection and will run the batt all the way down.

 

[dreadlocks]

10.anything volts is a flat battery as far as lead acid is concerned, might not be enough to fire the pump up even if LVD is bypassed.. remember the voltage you see at battery is not what fridge sees at end of its cabling, unless you pull it apart and stick a probe in there, yet still its within normal deviation anyhow.

3S is a poor 12v lead replacement.

 

[vtsoundman]

That makes sense, but then shouldn't I have seen the fridge briefly come on or the batt voltage drop when the fridge put it under load? And the bypass should have worked regardless, my understanding is it has no low voltage protection and will run the batt all the way down.

All fridges draw a slug of current on startup...lots of little things can be the 'straw that broke the camels back' when your batt resting voltage is below 11V...I am referring to voltage drop across thin wires, poor connection, crappy goal zero internals etc ... All of the things that normally wouldn't matter at nominal levels become an issue...

Is the Goal Zero really only 3s? I had a very low opinion of their products (solar panels, over priced boxes, etc) already, but if that's true, yikes.

 

[john61ct]

Say the transient startup is 12-15A. Any battery that can't handle that without a lot of sag has no business running a fridge.

Personally even if it's "only" a 4A load normally, adding a fridge to the usual lights + fan + screen gadget charging load, would lead me to upgrade from 100A @12V to 200+A

And I still would ensure a decent daily input of energy. If I know I'm not going to get any for two days in a row, then the bank needs to be sized to carry the average loads for 4-5 days without going below X% SoC.

Otherwise you're just playing chicken, like "let's see how far we can drive with only 10psi in the tires" or how far you get after the low petrol light goes on.

These expensive powerpacks are toys compared to what actual boondocking House banks need.

 

[DaveM]

Say the transient startup is 12-15A. Any battery that can't handle that without a lot of sag has no business running a fridge.

Personally even if it's "only" a 4A load normally, adding a fridge to the usual lights + fan + screen gadget charging load, would lead me to upgrade from 100A @12V to 200+A

And I still would ensure a decent daily input of energy. If I know I'm not going to get any for two days in a row, then the bank needs to be sized to carry the average loads for 4-5 days without going below X% SoC.

Otherwise you're just playing chicken, like "let's see how far we can drive with only 10psi in the tires" or how far you get after the low petrol light goes on.

These expensive powerpacks are toys compared to what actual boondocking House banks need.

No argument. This is not a long term off-grid power solution for larger setups. This will eventually be paired with a solar panel for in-camp. On the road I'd normally have ganged the fridge to the Yeti and the Yeti to the 12v aux in the car to keep it fed, but I don't have the optional 12v charging cable yet Like the Outback, the Yeti is an experiment in going a little lighter. Full size lead batts are too heavy and too large for my newly limited space and I can't really justify a dual batt setup (not even sure there's room under the hood of the 3.6r). If I ever go full size on the spare and mount it to the rear, there will be room in the empty spare compartment.

 

[e60ral]

Have you actually measured that current or an information source ?
Its always bugged me why such a low running current appliance that uses threephase inverter could not be made with ’soft start’ to minimise starting surge.
Or at least programmed retard time into its low voltage shutdown what would allow voltage to stabilise after a moment of running.
I confess not owning a ’fridge, but always read about them tripping out their lowvoltage shutdown when its supply voltage should be adequate to run.

it's not a big spike, it seems fairly soft. i don't have amperage trending, but i can clearly see the small spike in the voltage trending. when the compressor kicks on there is a 0.3V drop then it goes up and levels at only a 0.2V drop while running. the main reason it trips before it's supposed to is just a resting voltage vs. load thing. i only have a single agm battery so I typically use the high setting which is 11.8V but the battery measures a little over 12V if i check it after the fridge shuts off (which takes about 30 hours in summer for me with my 31m battery assuming the fridge is mostly full)

 

[vtsoundman]

Have you actually measured that current or an information source ?
Its always bugged me why such a low running current appliance that uses threephase inverter could not be made with ’soft start’ to minimise starting surge.
Or at least programmed retard time into its low voltage shutdown what would allow voltage to stabilise after a moment of running.
I confess not owning a ’fridge, but always read about them tripping out their lowvoltage shutdown when its supply voltage should be adequate to run.

Yes. It varies based on last run time, current compressor temp, voltage, etc. I don't recall the value (did an office purge and all those notes went with it), but it is somewhere between 10-25A.... high enough to cause an UVLO. A decent meter with a min/max function will catch it. I also used a scope to see the full curve( to make sure it wasn't a closure arc).

 

[TwinStick]

First, make sure that the 12v plug you are using has enough gauge to support the power you will be drawing. Many factory wiring is not. Our Power Wagon and our 4RUNNER would not support our 50 qt ARB fridge. I can strongly recommend the ARB 18' direct to battery wiring kit. Our 4RUNNER almost caught fire. Wiring melted. Not good.

I can also vouch for the cheap Gp 29 deep cycle battery that W-M sells. It would power the 50 qt ARB for 24 hrs with no sweat. Probably would go 48 hrs. I brought it back up every day with a charger & generator. Only took 20 minutes until charged.

 

[67cj5]

First, make sure that the 12v plug you are using has enough gauge to support the power you will be drawing. Many factory wiring is not. Our Power Wagon and our 4RUNNER would not support our 50 qt ARB fridge. I can strongly recommend the ARB 18' direct to battery wiring kit. Our 4RUNNER almost caught fire. Wiring melted. Not good.

I can also vouch for the cheap Gp 29 deep cycle battery that W-M sells. It would power the 50 qt ARB for 24 hrs with no sweat. Probably would go 48 hrs. I brought it back up every day with a charger & generator. Only took 20 minutes until charged.

Struth TS, How big is your charger, and at what Amp setting are you running it At, ??

 

[luthj]

Not that it likely matters with a cheap throw-away (not true deep cycle) Walmart battery. But no lead acid battery would be fully charged in 20 minutes. Maybe if it was already 98% full. At 50% DOD, 20 minutes might get you back to 80%, but you need a large charger.

 

[67cj5]

Not that it likely matters with a cheap throw-away (not true deep cycle) Walmart battery. But no lead acid battery would be fully charged in 20 minutes. Maybe if it was already 98% full. At 50% DOD, 20 minutes might get you back to 80%, but you need a large charger.

Well that type of Deep Cycle are duel purpose deep cycle batteries, About the maximum charge rate of any deep cycle battery is about 17%.

 

[MountainBiker]

OP, do what DuckTapeGuy said in his post. I spent 3 weeks in Baja this year, and the water bottles stayed frozen for the first 2 weeks! Pre-freezing a couple layers of water bottles in the bottom of the fridge, setting the temp at about 30 degrees during the driving period and ~38 at nIght, keeping the fridge out of the sun and driving every day are the keys. All the typical cooler rules apply,such as minimizing opening it, putting in only cold items, etc.

 

[john61ct]

About the maximum charge rate of any deep cycle battery is about 17%.

No, quality AGM can accept 0.7-8C charge rates when depleted.

That CAR declines as SoC rises of course.

And doesn't save more than a half-hour or so off the minimum 7+ hours usually needed.

 

[67cj5]

No, quality AGM can accept 0.7-8C charge rates when depleted.

That CAR declines as SoC rises of course.

And doesn't save more than a half-hour or so off the minimum 7+ hours usually needed.

The trouble is you get told that so many stories about AGM batteries it is hard to know what to believe, I still use my standard charger @ 10 Amps although I have 3 Smart chargers that are from 3.5 Amps up to 26 Amps,

I am sick and tired of all the can and can't Do's with all these modern batteries, They all require too much messing around along with the high investment cost plus all the special charging systems required and the reliability issues I am not prepared to throw heaps of cash in to them until they workout the bugs and the pricing becomes more reasonable, because there is no way is a battery worth 800 to a 1000 dollars.

 

[dreadlocks]

IMO AGM's are the least suitable for recreational house use for most here, given the cost and short life span in these rather hodgepodge minimalistic setups.. Its nearly impossible for most to reap the benefits of agm in a boondocking setup, you are far more likely to expose their weaknesses IMO.

GC2 FLA's with a slow charge and discharge rate (0.05-0.1C) are perfectly suitable indoors and out, with simple monitoring, no pampering, and checking the levels a few times a year.. and if you do mess em all up and end up with some tractor ballast then its not such a impact to the budget, you have enough room to mess em all up several times over before you even reach entry point for some quality AGM's.

LFP is a whole another can of worms, but it makes AGM's look even less ideal as usable amp hour per dollar of high end AGM bring it within range of DIY LFP.