LiFePo vs Lead Acid - Knowledge and myths

[Motoboss]

Gordon, Elliott and John thanks for the replies. I thought on battery and 150w solar was optimistic! So I’ll have to look at another battery (2) and 300w solar.
Thanks again

[CarlD]

Originally Posted by Motoboss

Reason being I would like to install a 12v dc fridge,

Power Draw @ 12V Amps Watts
Cooling 2.5-3.3A 30-40W
Idle(When Maintaining Temperatures) 2.9 35
Peak (During Testing) 6.6 80
Rated Max 20. 240


Essentially will 150 watts of solar run the fridge without depleting it in a 24 hour period?
I’m considering a LifePo4 as my next battery and would like to get away from a generator but if it won’t work then I will stay with my qroup 27 AMG deep cycle.
If this sounds confusing, it totally is to me

Based at your load values, it looks you have a large refrigerator. I have a truckfridge TF-130 (4.6 cu-ft) which draws about 40Ah per day (website lists 438 watt-hour per day). I have 200 watts of solar, 9 amps DC-DC TV charging. I have never run out of power. If your fridge consumption numbers are correct, you are going to require additional battery capacity and solar capacity to be comfortable. I would recommend looking at a different refrigerator.

One more item. If you go with LFP you should also get a 30-50 amp LFP charger for your trailer, which will enable fast charging from shore power or generator. For the warm fuzzy, rather than carrying a generator, you can get a 1000 watt inverter for a couple hundred bucks, which is easy to store, that you can attach to your TV with some jumper cables to power your camper, which will rapidly charge your battery. You only need to idle the TV to do this.

Hope this helps.

[Motoboss]

This is the fridge we are considering

https://www.recpro.com/rv-refrigerat...xoCCgUQAvD_BwE

[jwcolby123]

Originally Posted by Motoboss

This is the fridge we are considering

https://www.recpro.com/rv-refrigerat...xoCCgUQAvD_BwE

That's strange because it contradicts itself.


It connects directly into your 12V DC power and draws 15 amps and 180 watts.


How much power does this RV refrigerator use? Power Draw @ 12V Amps Watts Cooling 2.5-3.3A 30-40W Idle(When Maintaining Temperatures) 2.9 35 Peak (During Testing) 6.6 80 Rated Max20240

[CarlD]

Originally Posted by Motoboss

This is the fridge we are considering

https://www.recpro.com/rv-refrigerat...xoCCgUQAvD_BwE

The specs for this fridge don't seem right. They have larger 12 volt fridges the draw only 1 amp (12 watts) to maintain temperature.

For comparison, here is a Truck Fridge 2.3 cu ft and draws 288 Watt-hours per day or 288/24= 12 watts.

It seems like most of these compressor fridges use a danfoss compressor. I am not so sure about the one you specified as it is made in China.

[gordon2]

A fridge with a door on top instead of the traditional side opening door will retain cold better when opened. Many of the various sizes of fridges that use a Secop (Danfoss) compressor use the same size compressor and the power consumption is generally similar even if the fridge is smaller or larger, assuming everything else is similar.

So perhaps these figures will help. They are the power use I measured with a IndelB TB31A 29 liter / one cubic foot portable fridge. This fridge runs on either 120 VAC or 12 VDC. All but one of my measurements were on 120 VAC and you can assume the power consumption on 120 VAC is a little higher than on 12 VDC (but not very much more).

Of course a lot depends on how you pack it, how often you open it, what the ambient temperature is, etc.

If you are looking at a fridge that does NOT use a true Secop (Danfoss) compressor then I would be sure to see that it is as efficient as one that does.

Scenario #1, “Ice cold” beer
Fridge not prechiiled but filled with pre-chilled beer bottles.
Fridge Setting 32 degrees, max cooling
Power usage: Instantaneous with Compressor on = 58-73 watts. With compressor off = 4 watts.
24 hour consumption: 354 watt hours.

Scenario #2, Room temp soda
Starting with 24 room temperature (68 f) twelve ounce cans of soda.
Fridge Setting: 34 degrees, max cooling
Compressor ran non-stop (at about 60 watts) for a little over six hours. The fridge consumed 360 watt-hours in those six hours. Estimated total for first 24 hours: 622 watt hours (this shows the benefit of pre-chilling the fridge and its contents.

Scenario # 3 (Same as #2 except everything pre-chilled, and fridge not opened, eco setting)
34 degrees, eco, 24 cans, all pre-chilled, door left closed.
24 hours: 254-260 watt hours.

Scenario #4 Same as 3 except temp setting 39 and run on 12 VDC
Run on 12 VDC in Scamp where air temp was 74-89. 24 hours: 15.78 AH (~197 watt-hours)

Scenario #5 Used as a Freezer (Setting 5 degrees, Eco mode,120 VAC indoors)
592 watt hours in 24 hours.

[AlanKilian]

I want totally minimal for my setup. US$150-US$200
- 12 Volt water pump.
- Maxxair fan with the controller replaced with a solid-state variable-speed one.

One 30 Watt solar panel/controller kit US$70
One 35 AH AGM battery US$65
Low voltage cutoff US$12
(You don't need it, but I do since I'm a geek) Astroflight Wattmeter US$62
Fuseblock US$9
3D printed stuff, switches etc. Probably US$10
https://www.amazon.com/gp/product/B0836PVY8J
https://www.amazon.com/gp/product/B00K8E0WAG
https://www.amazon.com/gp/product/B07929Y5SZ
https://www.astroflight.com/101-supe...r-details.html
https://www.amazon.com/gp/product/B078T7RP1V

[John in Michigan]

These posts concerning compressor fridge power usage show why its important to accurately determine. Also I've found its difficult to find this info for most current compressor fridges. Here are specs for two 100 liter upright fridges. They seem reasonably objective.

Example 1: For the Isotherm Cruise 100 Classic Refrigerator, found two informative sources.
First, on the suremarine dot com website is this:
Power Consumption: 400 W/24 h*
*Note: Power consumption W/24 h in operation on 12 V with +5°C in the refrigeration space, ambient temperature +25°C according to the Standards ISO 15502:2005 and EN 153:2006.
Second, on the westmarine dot com website is this:
Amperage 0.9 Amps at 120 Volts AC; 2.8 Amps at 12 Volts DC

Example 2: For the Nova Kool R3800 Refrigerator, found one informative source, the vendor's website:
Amperage Running* 12/24vdc 2.4 / 1.2
*Note: The amperage listed is while the unit is running. To determine 24hr consumption calculate the run time for 24hrs and multiply this by the listed amperage. Listed amperage will change with ambient temperature and unit door openings.

[John in Michigan]

I had a setup similar to AlanKilian's in my Trillium 4500 (36 ah yellow top battery, 100 watt solar panel). Used for charging phones and tablets and running led lights and lp detector. It worked fine except that in heavily shaded sites the battery would be at 50% after 3-4 days.

When we started using the Boler 17 AND added a Propex HS2800 furnace (2.8 amp), we switched to two lifepo4 100 ah batteries. Our typical worst case is shoulder season camping for up to seven 24 hour days with very little sunshine (overcast/short days/low angle sun) and cold temperatures (highs in the mid forties F) with the furnace running 1/3 of the time. Also justified the switch to two lifepo4 100 ah batteries with our intent to replace the 3 way fridge with a compressor fridge.

[CarlD]

Specifications are all over the place. I really like the 24 hour watt-hour consumption because it is an average value, however the ambient temperature is not usually defined.

Gordon2:

Interesting scenarios you posted but only the first one has any value, because if the fridge doesn't have beer in it, what good is it!

[gordon2]

Originally Posted by CarlD

Specifications are all over the place. ...

Of course that is true because of the wildly varying conditions, temp and eco/max setting, number of door openings, etc.

I once used the IndelB in my car parked in the hotel parking lot all day in the summer. It kept up, which was impressive, but it must have used almost 900 watt hours during the day and I would guess 1200 for 24 hours.

I'm actually running some more tests now but I can predict the range from maybe under 200 watt hours / 24 hours to over 600, and that is with an ambient temp of 75-80 f.

Originally Posted by CarlD

Interesting scenarios you posted but only the first one has any value, because if the fridge doesn't have beer in it, what good is it!

True, the only problem is that the door is opened so often!

[zack sc]

I have a group 27 Pb-acid battery and a Jackery E1000 Li-ion battery. I think it is great having both. I use the Jackery to run a CFX65DZ Dometic fridge which uses only about 300 or 400 Watt hours per day at 37 F. (The Jackery E1000 capacity is 1000 Watt-hours.) The other thing I find really useful is, when needed, I can plug the Scamp into the Jackery 110 volt inverter output and thereby power the Scamp converter and top up my Pb-acid battery. It doesn't take that much power (typical is 70 Watts) and I think that can really protect my Pb-acid from sulfation by getting it back to full charge when there is no shore power around. (I am thinking the charge wizard in the Scamp converter does a better job at topping up the charge (absorption & float stages) than the TV alternator. Is that true?)

So anyway, I think of Li-ion and Pb-acid as complementary. It is nice to have both.

I am a little confused as to what type of Li-ion you guys are talking about and whether it is different from the various sorts of 18650 and 21700 cell based batteries that are in Jackery batteries, Teslas and a lot of e-bikes? If anyone could clear that up for me, that would be really appreciated.

[jwcolby123]

Originally Posted by zack sc

...

I am a little confused as to what type of Li-ion you guys are talking about and whether it is different from the various sorts of 18650 and 21700 cell based batteries that are in Jackery batteries, Teslas and a lot of e-bikes? If anyone could clear that up for me, that would be really appreciated.

Yes they are different chemistries. My understanding is that the 18650 is Lithium Ion. TBH Lithium Ion is a catch phrase, it is not the actual chemistry, and I do not know that chemistry as I have studiously avoided using those types of batteries. That is the 'dangerous' chemistry which can go into thermal runaway and catch fire. This is mostly a problem where the charge current is not limited or they sit in very hot environments such as a hot car in AZ. Lithium Ion has about the highest charge per weight of any readily available battery, and is used in phones, laptops, scooters, ebikes and many of the e-vehicles. It requires a BMS to make it safe.

The batteries in this thread concentrate on LiFePO4 or Lithium Iron Phosphate. These batteries have a somewhat lower power to weight ratio but do not suffer from the safety issues of Lithium Ion. There are videos of people drilling into them, driving nails, shooting them etc. They will smoke and smoulder but to my knowledge just won't catch fire.

I look specifically for LiFePO4 as the chemistry for any battery I want to work with.

The other thing to know is that every chemistry has its own min/max voltage. For example a Lead Acid battery requires 6 cells to make 12.75 volts or about 2.125 volts per cell.

LiFePo4 has a battery range from 2.5 (fully discharged) to 3.65v (fully charged. As it happens this maps pretty well to automotive '12v' systems, 4 x 2.5 (fully discharged) is 10v, 4 x 3.0v (top of the low charge knee) is 12v, 4x 3.3v is 13.2v (bottom of the upper charge knee) and 4x3.65 = 14.6v which just happens to be the upper charge voltage for lead acid.

The result of this is that 4 LiFePO4 cells 'emulates' a lead acid battery very well, and can even use the same charger (though not 100% optimally).

Lithium Ion (18650 and the like) has a voltage range significantly higher - 2.75-4.2 volts which does not map well to 12v automotive though it does map well to 24v (6 batteries in series.) and even 48v which is used for ebikes and such.

[David Tilston]

Originally Posted by jwcolby123

Yes they are different chemistries. My understanding is that the 18650 is Lithium Ion. TBH Lithium Ion is a catch phrase, it is not the actual chemistry, and I do not know that chemistry as I have studiously avoided using those types of batteries. That is the 'dangerous' chemistry which can go into thermal runaway and catch fire.

That may be true of lithium-ion batteries. I remember some cell phones being banned on comerical flights. However, it is the lithium-polymer chemistery that I have heard very bad things about, (one of my neighbors house caught on fire). To the point that the devices I have that use them, (old quad-copter drones) come with a warning to not charge them unsupervised. Hopefully they have seen some technical development like a BMS to prevent fires.

[zack sc]

Originally Posted by jwcolby123

Yes they are different chemistries. My understanding is that the 18650 is Lithium Ion. TBH Lithium Ion is a catch phrase, it is not the actual chemistry, and I do not know that chemistry as I have studiously avoided using those types of batteries. That is the 'dangerous' chemistry which can go into thermal runaway and catch fire. This is mostly a problem where the charge current is not limited or they sit in very hot environments such as a hot car in AZ. Lithium Ion has about the highest charge per weight of any readily available battery, and is used in phones, laptops, scooters, ebikes and many of the e-vehicles. It requires a BMS to make it safe.

The batteries in this thread concentrate on LiFePO4 or Lithium Iron Phosphate. These batteries have a somewhat lower power to weight ratio but do not suffer from the safety issues of Lithium Ion. There are videos of people drilling into them, driving nails, shooting them etc. They will smoke and smoulder but to my knowledge just won't catch fire.

I look specifically for LiFePO4 as the chemistry for any battery I want to work with.

The other thing to know is that every chemistry has its own min/max voltage. For example a Lead Acid battery requires 6 cells to make 12.75 volts or about 2.125 volts per cell.

LiFePo4 has a battery range from 2.5 (fully discharged) to 3.65v (fully charged. As it happens this maps pretty well to automotive '12v' systems, 4 x 2.5 (fully discharged) is 10v, 4 x 3.0v (top of the low charge knee) is 12v, 4x 3.3v is 13.2v (bottom of the upper charge knee) and 4x3.65 = 14.6v which just happens to be the upper charge voltage for lead acid.

The result of this is that 4 LiFePO4 cells 'emulates' a lead acid battery very well, and can even use the same charger (though not 100% optimally).

Lithium Ion (18650 and the like) has a voltage range significantly higher - 2.75-4.2 volts which does not map well to 12v automotive though it does map well to 24v (6 batteries in series.) and even 48v which is used for ebikes and such.

Thanks John. This is really helpful.
I guess all my experience is all in the "Li-ion" category. Personally, I do not feel at all in danger from my Jackery or my bike batteries, which all have a high-end BMS (though I guess if you put a bullet in it you could get thermal runaway). The E1000 is 1000 Watt-hours and just 22 lbs which includes a good inverter.

[redbarron55]

Lead is fairly easily recycled, but I lived in Leeds, Alabama for a time where Interstate had a recycling/reclaiming operation and the result of (basically criminal) operations was a super fund site with lead in the ground water.
Other than that, no problems.
That was when I started installing reverse osmosis water filter systems in all of my houses.
No matter the technology companies who fail to follow the law are a problem for all of us.

[jwcolby123]

Originally Posted by zack sc

Thanks John. This is really helpful.
I guess all my experience is all in the "Li-ion" category. Personally, I do not feel at all in danger from my Jackery or my bike batteries, which all have a high-end BMS (though I guess if you put a bullet in it you could get thermal runaway). The E1000 is 1000 Watt-hours and just 22 lbs which includes a good inverter.

There is more to it than that. The 'Lithium Ion' batteries have higher power density (I believe is the term) but also far lower life cycles, typically about the same as Lead Acid, whereas the LiFePO4 have lower power density but way higher charge cycles, typically around 3000, depending on a lot of things such as temperatures operated at and how deeply charged / discharged.



I just feel that for our purposes LiFePO4 is the better chemistry. Just my opinion of course.

[John in Michigan]

Here is a teeny bit more detail:

https://www.epectec.com/batteries/cell-comparison.html

lifepo4 batteries fall under the category of li-ion. Interesting table at the bottom of the article should garner some discussion!

[Perryb67]

Add another myth:
A battery's BMS always protects the battery.

Any BMS will fail and when they do it can be catastrophic. One failure with that cheap, poorly mass-produced battery with a cheap BMS can justify the cost of a BattleBorn or Renogy. At least you get a warranty that probably will get you a replacement.

An interesting read is: why I call Li fussy
No, it's not all factual, but then what thread is, including this one.

Enjoy,

Perry

[jwcolby123]

I worked in electronics for 15 years. Some more or less facts. Everything fails. The sun will fail eventually. So yes, the BMS will fail.

What is true about electronics failures is that absence power cycling, most electronics will work for a long loooonnnnng time. As in decades. Or centuries.

https://en.wikipedia.org/wiki/Centennial_Light

The fact is that current surges cause the leads between the package pin and the internal die to flex. Anytime anything flexes, it causes stress fractures.

Everything manufactured by man pretty much follows the infamous bathtub curve, high failure rate for the first X days (about 90 for most electronics) then a flat area where very few failures occur, then the failure rate trends back upwards and lots of failures.

Which is why I claimed that if the battery lasts 90 days or so it probably will not fail for a long long time. Unless it is a PbA battery in which case the BMS (owner) will often trash it.

As for the concept of "cheap Chinese"... That is a mostly racist stereotype. Chinese people are genetically identical to white anglo people, or black people or mexican people. They are no better or worse. And I got news for a lot of people, they are winning the technology race. They are cleaning our clock so to speak.

Every single component in the Battleborn Battery is manufactured in China. Final assembly is all that Battle Born can claim. If you believe that the Chinese can build clean rooms and the manufacturing to completely take over the semiconductor industry but can't assemble a battery you are delusional.

Do you shop at WalMart? If so you are personally and individually responsible for the 'cheap junk' so prevalent in the USA today. You want cheap, you demand cheap, you get cheap. You want Battle Born? You get the same cheap, just assembled in the US. BTW the 'cheap' lithium cells manufactured in China (and they are inexpensive) are extremely high quality stuff, manufactured using precision techniques as good as any in the world.

Sorry, I have no time for such drivel.