Now that summer is here the fridge runs a bit more. I have had a few days lately where I only drove my vehicle 1 hour a day and the fridge shuts off on low voltage. I had a deep cell battery from Batteries Plus and it worked a bit better. This time I got a Costco Interstate. The vehicle still starts with the low voltage thanks to the shut off. What is the easiest way to keep from having to start the vehicle and idle it to keep the battery good for the fridge? Will a 25W panel with a charger do it? I am looking for a simple panel with alligator clips I can set next to the vehicle or something like that. I am not looking to mount anything permanent. Thanks for the help
Simple solar to assist with fridge while parked
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javelinadave
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I think you need to see what your fridge draws to determine is a 25w panel would do the trick. This article may also be of some help.
Fridge Power Draw
Fridge Power Draw
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- #3
Ok, that looks like .4 Amps/Hr is what my 47L will pull
^ 0.4A average looks low to me.
A typical camping fridge uses about 50W to run and is on maybe 1/3 or 50% of the time. Depends on conditions but roughly speaking. So around 20 - 25W average. That makes it look like a 25W panel should do the trick. Unfortunately, a "25W" panel will rarely produce 25W. So, no, I don't think a 25W panel would be enough to maintain the battery under typical conditions.
The cheap little panels you see connected directly to the battery without a controller, with just alligator clips or a cigarette lighter plug, have to be very small to not potentially damage the battery since they are so dumb. I'm thinking 5W, maybe 10W. For more than that, you would want a controller but then the cost of the controller would likely be more than a 25W panel, so better to get bigger than a 25W panel while you're at it.
Anecdotally, I did read a fair bit of discussions where people say a 100W panel is a comfortable size for a fridge and 75W may be cutting it close. Obviously, all that depends on where you are and what time of year.
A typical camping fridge uses about 50W to run and is on maybe 1/3 or 50% of the time. Depends on conditions but roughly speaking. So around 20 - 25W average. That makes it look like a 25W panel should do the trick. Unfortunately, a "25W" panel will rarely produce 25W. So, no, I don't think a 25W panel would be enough to maintain the battery under typical conditions.
The cheap little panels you see connected directly to the battery without a controller, with just alligator clips or a cigarette lighter plug, have to be very small to not potentially damage the battery since they are so dumb. I'm thinking 5W, maybe 10W. For more than that, you would want a controller but then the cost of the controller would likely be more than a 25W panel, so better to get bigger than a 25W panel while you're at it.
Anecdotally, I did read a fair bit of discussions where people say a 100W panel is a comfortable size for a fridge and 75W may be cutting it close. Obviously, all that depends on where you are and what time of year.
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Yeah, 100W would be 'ok'. Use a decent charge controller to do right by the battery.
Also, NOTE, you don't want to discharge your lead acid (gel, or wet) more than 50%, so whatever the AH rating of the battery is, you really only have 50% of that. Even 50% discharge will reduce the life of such batteries.
Also, charging a battery is not 100% efficient, so your 100W of solar will have losses through the charge controller and then less than what gets to the battery will end up as charging AH.
A lot of folk now run a LiFePO4 battery as an aux, they can deal with much deeper discharge and still provide 1000's of cycles, they also charge more efficiently. Obviously you would want a decent charge controller from the main battery to the aux.
Of course you are then going down the rabbit hole
cheers,
george.
Also, NOTE, you don't want to discharge your lead acid (gel, or wet) more than 50%, so whatever the AH rating of the battery is, you really only have 50% of that. Even 50% discharge will reduce the life of such batteries.
Also, charging a battery is not 100% efficient, so your 100W of solar will have losses through the charge controller and then less than what gets to the battery will end up as charging AH.
A lot of folk now run a LiFePO4 battery as an aux, they can deal with much deeper discharge and still provide 1000's of cycles, they also charge more efficiently. Obviously you would want a decent charge controller from the main battery to the aux.
Of course you are then going down the rabbit hole
cheers,
george.
25W isn't going to be enough. I have a 30W panel on some of my cars and that's barely enough to prevent self discharge.
I went through the same process that you're going through right now. If you want to save money and skip the the end I can tell you where I ended up. 100W solar panel (~$100), 100Ah LiFeP04 battery (~$300), and Renogy dual input charge controller (~$200). Trying to save money by incrementally changing my setup ended up costing me more money in the long run.
Solar actually isn't that efficient when you take into account all the loses. A 100W panel is really good for about 70W at it's peak. Once you take into account charging loses, sunlight angles, shading, etc, at best you might be getting 300-350Wh a day, but usually a lot less. You could increase that if you're panel is moveable and you're willing to constantly optimize the angles, but that takes a lot of effort. The tradeoff is if you're panel is near or attached to the vehicle, then your car is also in the sun getting hotter and your fridge is using more energy.
The low voltage cutoff might save you from being stranded, but it's also killing your battery. Every time you hit that limit your battery life is taking a hit. I went through 3 lead acid batteries in less than 3 years before finally spending the $$$ on a lithium. I would've saved $$$ by just purchasing it up front, but I'm a slow learner. Not only do you get 2x the capacity (as george mentioned), you get probably 100x the number of cycles.
You can also get a cheap charge controller for around $10 that will do a decent job of charging your battery, but then you'd have to figure out a way of also charging from the car alternator. A dual input charge controller like the renogy makes everything simple and headache free, it charges from solar when the sun is out, switches to alternator when the engines running, and automatically switches to charge the starting battery after the house battery is fully charged. I tried different methods of having it switch between solar and alternator, but it quickly became a mess of wiring and require constant tinkering.
I went through the same process that you're going through right now. If you want to save money and skip the the end I can tell you where I ended up. 100W solar panel (~$100), 100Ah LiFeP04 battery (~$300), and Renogy dual input charge controller (~$200). Trying to save money by incrementally changing my setup ended up costing me more money in the long run.
Solar actually isn't that efficient when you take into account all the loses. A 100W panel is really good for about 70W at it's peak. Once you take into account charging loses, sunlight angles, shading, etc, at best you might be getting 300-350Wh a day, but usually a lot less. You could increase that if you're panel is moveable and you're willing to constantly optimize the angles, but that takes a lot of effort. The tradeoff is if you're panel is near or attached to the vehicle, then your car is also in the sun getting hotter and your fridge is using more energy.
The low voltage cutoff might save you from being stranded, but it's also killing your battery. Every time you hit that limit your battery life is taking a hit. I went through 3 lead acid batteries in less than 3 years before finally spending the $$$ on a lithium. I would've saved $$$ by just purchasing it up front, but I'm a slow learner. Not only do you get 2x the capacity (as george mentioned), you get probably 100x the number of cycles.
You can also get a cheap charge controller for around $10 that will do a decent job of charging your battery, but then you'd have to figure out a way of also charging from the car alternator. A dual input charge controller like the renogy makes everything simple and headache free, it charges from solar when the sun is out, switches to alternator when the engines running, and automatically switches to charge the starting battery after the house battery is fully charged. I tried different methods of having it switch between solar and alternator, but it quickly became a mess of wiring and require constant tinkering.
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- #7
Wow, good to know. Sounds like it would be far easier to bring my generator and battery charger. Maybe pony up for a deep cell battery next time
Yes, a generator is easier (at first) if you don't mind the noise, the fuel, and the size/weight, and already have one.
But it's actually pretty simple to set up a solar system if you have a basic understanding of DC wiring and are willing to read a bit about the components. For just a fridge the system could be small and relatively inexpensive, I would say starting at around $150 not counting the battery, if you are frugal. It's really only the panel, wires, a controller, and wires to the battery. Plus a fuse someplace, ideally. You could conceivably use your starter battery to save money, but a LiFeP 12V 100Ah battery is now as low as about $150. Not that much more than lead acid and head and shoulders above lead acid as a house battery. And it's nice to have a separate battery for the fridge.
If money is no object, one of those newer fancy all in one "solar generators" (bad name) would make it even easier and more versatile.
But it's actually pretty simple to set up a solar system if you have a basic understanding of DC wiring and are willing to read a bit about the components. For just a fridge the system could be small and relatively inexpensive, I would say starting at around $150 not counting the battery, if you are frugal. It's really only the panel, wires, a controller, and wires to the battery. Plus a fuse someplace, ideally. You could conceivably use your starter battery to save money, but a LiFeP 12V 100Ah battery is now as low as about $150. Not that much more than lead acid and head and shoulders above lead acid as a house battery. And it's nice to have a separate battery for the fridge.
If money is no object, one of those newer fancy all in one "solar generators" (bad name) would make it even easier and more versatile.
Depends. Lithium batteries are cheap now. It's probably close to the same cost as a deep cycle and the there are so many more benefits to lithium it's not worth wasting the money on anything else. 1/2 the weight, 2x the usable capacity, at least 2X-10X the charge rate, and 10X-100X the lifespan for less than twice the money.
You can make it work with a generator, it all depends on how often you need it and how much effort you want to put into it. A generator would work well with a battery pack like the Ecoflow Delta 2, because it can fast charge at 1.2kW so you'd only need to run it for an hour to fully charge. Some of the older battery packs can't handle that kind of charge rate so you'd have to run the generator 4-5x as long to fully charge at a slower rate, so you'd be "wasting" the excess generator capacity. Normal SLA batteries would probably take all day to fully charge.
There are some pros and cons to lithium in cold or super hot. The batteries dont like to be frozen and they also dont like extreme heat in an engine bay. It’s worth reading into.
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- #12
I am handy and have no issues with wiring or installing anything, it just looks like it might be more than I want to spend to get something that will work. I only use the fridge when I am camping and normally it isn't an issue unless I do not drive much that day. So really it is only a handful of days a year, so a $600 upgrade is a big pill to swallow. I do have a generator and charger I can bring, but it does take up space.
You can get a flexible 100w solar panel for not too much money, and a small 10-amp charge controller for less (get an MPPT). Victron makes one for $60. This should give you something approaching modest energy independence. The solar panel can live inside the vehicle tucked up next to the ceiling. When you get to your destination, deploy the panel, secure it, and hook it all up. A lithium battery will give you more time between charges because you can safely discharge down to a very low reading (10% for instance) which you could never do with lead, or at least not many times.
No way would I use a generator. I'd find another hobby first. A high quality cooler now is capable of keep food cold for days and days and you can forget about the whole solar thing. Just buy ice once a week.
No way would I use a generator. I'd find another hobby first. A high quality cooler now is capable of keep food cold for days and days and you can forget about the whole solar thing. Just buy ice once a week.
FWIW, I use an engel mt45 and in good sunny days it takes a 60watt panel to "keep up" and thats on moderately hot days. add in hotter temps and it takes 68 watts at peak perf to " keep up" when fridge is on a 50% duty cycle ( kinda worst case scenario). Thats breaking even. With potential shading and variables it is best to double that. I went to 150watts solar with 2 batts ( linked 100% of the time, no dual batt BS ) . The system will recover the nights drain before breakfast is over, its pretty much stand alone without having to start vehicle given sun. And I run a Starlink & lights at night. The starlink will draw it down at night when on for hours but again,it recovers quickly. If you stay at say 100w it would affect the recovery time and the system may not recover batt to 100%. I have found that with 150watts it keeps the system closer to voltage. I used to run 100watt panel and after sitting 3 days same conditions I would have to start truck to get batts back to voltage, the 150watt panel has extended that to indefinite given sun.
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- #15
Good to know, sounds like you have found the right amount of panel for the job
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- #16
Looks like Prime day has some sub 100 deals, would something like this work across my regular battery?
quick impression is that the above is inexpensive and inexpensive stuff is probably what you will get. There is not much info there, though. Given that it's 150W nominal, it would probably be big enough for a fridge even if not particularly high performance, so likely OK at least in that respect. The controller is probably on the very low end and you'll likely want better before too long. The solar panel will probably be useful in the future even if not especially great -if it does not conk out early-. And, yes, as P says, depending on the construction, the folds can be problematic. But folding panels are also so much easier to store.
Overall, it would likely make a big difference over relying on running the engine, and be a reasonable intro into solar stuff. If $$ are limited to $100, I would say try it if you don't see a better deal or better reviews. If you can spare more than $100 I would suggest you do a bit of research and get better stuff. For $150-200 you could likely get significantly better quality that will last longer and work better. My general impression is that it's usually the controller that is often the bottleneck in getting a system to work well (efficiency, MPP algorithm, range of settings etc), not so much the panels if they are at least of suitable size (they are dumb and just sit there, and their efficiency is likely a moot point compared to poor orientation issues).
Overall, it would likely make a big difference over relying on running the engine, and be a reasonable intro into solar stuff. If $$ are limited to $100, I would say try it if you don't see a better deal or better reviews. If you can spare more than $100 I would suggest you do a bit of research and get better stuff. For $150-200 you could likely get significantly better quality that will last longer and work better. My general impression is that it's usually the controller that is often the bottleneck in getting a system to work well (efficiency, MPP algorithm, range of settings etc), not so much the panels if they are at least of suitable size (they are dumb and just sit there, and their efficiency is likely a moot point compared to poor orientation issues).
Thats it, the controller is where you get the ability to expand system. For example I use a very simple( idiot lites, no read out/screen) controller rated at just above my solar input and I just went pos to pos on the dual batts. A better controller could allow an auto function for charging and disconnecting the second batt as well as provide other percs like a detailed readout of various info and ability to power aux acc's. Those controllers are significantly more expensive than the entire system you posted. E is correct- run it and see if you need mods like more solar, more abilities from charge controller or more batt cap.
The real difference is making the jump from using a standard solar charge controller ( as in the kit) versus the big exp ones that handle batt charging, dual batts, solar input, other aux inputs, & acc load. I have found a water wheel that plugs in just like a soalr panel and cant wait to test it out. If next to running water you just drop it in and plug it in, might be useless , there are a few camp spots where it would be ideal and its small to pack.
The real difference is making the jump from using a standard solar charge controller ( as in the kit) versus the big exp ones that handle batt charging, dual batts, solar input, other aux inputs, & acc load. I have found a water wheel that plugs in just like a soalr panel and cant wait to test it out. If next to running water you just drop it in and plug it in, might be useless , there are a few camp spots where it would be ideal and its small to pack.
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- #20
Ok, I pulled the trigger and got a different style besides the accordian. Might be here tomorrow
