Struggling with Solar Setup - 100 Watt Solar + Lead Acid + Lifepo4 Power Pack + Dometic Fridge

[rypajo]

Going to assume I am way overthinking this and setting myself up for ridicule but I am struggling with the updates to my setup - Currently, I am running the standard lead-acid primary starting battery w/100-watt rooftop solar setup through a 20 amp solar charge controller to power my Dometic fridge and other minor accessories. Pretty basic and straight forward. Obviously, this isn't ideal and I need an upgrade to not put the strain of 5-8 hrs of fridge consumption on a battery not designed to do this job.


I would love to maintain the ability to still use the solar to keep my vehicle charged when the power pack isn’t in the vehicle since the solar is permanently mounted.


Future setup will include a portable power pack build using a Power Sonic 12.8v lifepo4 45AH battery, 120v inverter, additional 20 amp solar charge controller that is compatible with the lifepo4 battery and all the other trimmings. After reading a lot of what is probably hyperbole on from different articles on voltages and chemistry, I am struggling with how to incorporate it w/out mixing chemistry/voltages while still maintaining solar charging ability for the vehicle as well as the pack being self-sustaining away from the permanently mounted panel on the vehicle. So I am toiling with the idea of two different solar charge controllers in some manner but that just feels like a bad idea unless I come up with a way to isolate which controller is not needed at that moment.



https://expeditionportal.com/forum/threads/charging-lifepo4-from-12v.197220/



I reviewed through this and it basically seems to elude to that if I use an ignition/alt relay to not pull from the starting battery when the ignition is off everything would be fine. I think I could put it in line with the power pack and trigger it from the ignition hot plug in the back of my vehicle. Idle voltage is 13.8-13.9 so I believe I would be fine on that point so all this overthinking might not matter. Just run the +- from my power pack to a 12v relay on my fused run to my starting battery and call it a day.



Any input would be appreciated. Most likely I will just end up having to eliminate/terminate the built in solar controller in the vehicle and run the solar leads to the controller in my pack and use the accessory output from the controller to input back to the vehicle 12v power. Any major repercussions from doing this? The other part of this I haven’t wrapped my brain around is how to charge the power pack from the vehicle while in motion?

 

[Martinjmpr]

Future setup will include a portable power pack build using a Power Sonic 12.8v lifepo4 45AH battery, 120v inverter, additional 20 amp solar charge controller that is compatible with the lifepo4 battery and all the other trimmings.

There are people on the forum with way more electrical knowledge than me so I'll let them chime in on the specifics of your system but I wanted to focus in on the part in bold, because I see it again and again in many types of power box "builds" as well as in commercial, off-the-shelf battery power systems.

Do you NEED an inverter? What is it that you are running that requires 120vAC power? Inverters are terribly wasteful of energy - if they're used only while the vehicle is running, that's one thing as you likely have power to spare from your alternator. But when the engine is not running an inverter can potentially be a huge drain on your battery (depending on the size.)

So once again I would ask: Do you NEED one? Or do you just assume you "have" to have one because "everybody else does?"

Wife and I aren't "overlanders" but we camp a LOT. Sometimes at state parks with electric hookups but more often in the National Forest without. LITERALLY the ONLY thing we have ever needed an inverter for is to charge the batteries on our camera, and as goofy as it sounds, you know what works great for that? One of those crappy little $20 150w inverters that plugs into a 12v socket that you can get at a truck stop or wal mart. That's it.

https://www.amazon.com/BESTEK-Inverter-Charger-Charging-Shared/dp/B003SGJIRO/ref=sr_1_4?keywords=12v+power+inverter+150w&qid=1568299279&s=gateway&sr=8-4

Now, some people in our group (we have a lot of "older" people - including us, I guess! ) use a CPAP and claim they need an inverter for their CPAP. I don't know much about CPAP's but from what I've seen they make battery and 12v power CPAPs so if I was camping a lot and needed a CPAP, that's what I'd use.

As I said, inverters, generally speaking, are big wasters of power. The only thing I can think that most "overlanders" would need with an inverter is a way to charge a laptop computer.

But wait - laptop computers run on batteries, right? And batteries use DC, don't they? That 120v AC power plug actually has a step-down transformer built in to transform the 120vAC power into DC power. That's how it charges/powers the laptop.

So isn't it a little silly (not to mention wasteful of energy) to:

1. Take 12vDC power from the battery
2. Convert it to 120vAC using an inverter, to then plug in a laptop computer that will
3. Convert that 120vAC power BACK to some voltage of DC power to actually charge the laptop?

Seems like a lot of waste and inefficiency there. Wouldn't it make more sense to just go from DC power in the truck battery to DC power in the laptop? I can't believe they don't make DC laptop chargers for just these kinds of situations.

As I've posted elsewhere in this sub forum, I'm working on a "power box" right now to keep our TruckFridge running. But when I consider all the things that I NEED in the box, it has never once occurred to me to put in an inverter because why? I can't think of a single reason I'd need one.

Obviously, my needs are not yours. You may well need an inverter for something and in that case, I guess that's the way you have to go. But I'd carefully evaluate your NEEDS vs. your "nice to have" because without an inverter, making a 12v power system gets quite a bit easier.

 

[rypajo]

Totally a fair assessment. The inverter I am using is a very small Pure Sine 150-watt peak inverter that without its case has the footprint of a credit card and it under an inch tall. 99% of my needs are 12v but there are a few uses that the small inverter will be handy ex: LED light strands used while camping that we already own, small TV during our frequent power outages (house runs off a battery-backup hotspot year round), 18v tool charging, etc... I am also going to run leads to terminals for the very infrequent needs of a 1kw inverter for short periods of time. Laptop charging duties will be taken care of with a usb type-c socket so there will be very few times that dc-ac-dc will be necessary. If my case is running out of room this will be the first thing that will be eliminated as I am trying to keep my package as small as possible. The current goal is to use a Pelican 1300 case that I already have. Based on preliminary Solidworks modeling it's possible but won't be easy.

Again, thanks for your input and concerns. They are duly noted.

 

[rypajo]

Got the battery electronics wired up and functioning. Reviews implied the ammeter would need calibration but my load tests using the inverter and a hue bulb the amp were spot on for a 10% loss in the inverter so I'm not going to stress over it. Need to sort out connectors for external charge cord, solar hookups, and 12v auto/dist+relay. 2.5mm screws are hard to come by for attaching the external hookups so wasn't able to button those up yet. I prioritized having the ac charger onboard over inverter for now so it will be an all-inclusive package. I still have room to fit the small inverter but I have yet to find a 120v socket set that I like. Most have felt very cheap and do not offer weather sealing. I'm thinking I might make a little dongle/pigtail that stays inside the case till needed to take care of that issue if I go that way. My fridge is plugged into it right now and in a 78-degree ambient room, it's been chugging away for 32 hours with 57% battery remaining. Pretty excited overall.

 

[Martinjmpr]

What is that in your first picture? A battery monitor? Or is that your LiFePo power pack?

 

[revbillyg]

Have a parts list?

 

[rypajo]

What is that in your first picture? A battery monitor? Or is that your LiFePo power pack?

It's a monitor but it honestly doesn't work all that great. It's designed to measure the current in and out of your battery but I think I'd have to wire my solar to my relay instead of direct to the battery for this functionality to work. It's amps out seems to be a bit off as well.

Have a parts list?

Basic Build and Materials:

Pelican Storm iM2075
Mroinge 120v lifepo4 charger
(2) Cigarette Waterproof Sockets
PD Type C / QC 3.0 USB Socket
DROK Ammeter w/ Hall sensor
12v Toggle Switch
12v Relay
Assorted xt60 bullet connectors
Handful of 8 awg ring connectors
m2.5 x 8 hex screws
ALLPOWERS Solar Charge Controller (Compatibility Mode For lifepo4)
Power Sonic PSL-12450

 

[Larkinsg]

A Dometic CF 25 draws 600 Watt-hrs per day when set at 35 F or 2 C in 100 degree heat. A 150 watt solar panel is a minimum to run this fridge without any help from the alternator in my truck. I find that real world solar panel power outputs need to be derated to 73% of their listed value when placed flat on a vehicle so where 100 Watts would be marginal in theory the reality is that you will need at least a 120-150 Watt panel.

That said, a 50 Amp-Hour battery is an absolute minimum IF it is a LiFePO4 12v battery. I use a 100 Amp-Hour Battleborn. If you are using a lead acid you will need a minimum 100 Amp-Hour battery and 150 Amp-Hours is more realistic. With lead acid you will need a larger panel, I suggest 200 Watts as a minimum, since lead acid charges.more slowly and less efficiently.

Cheers,

Grover

 

[dstefan]

Future setup will include a portable power pack build using a Power Sonic 12.8v lifepo4 45AH battery, 120v inverter, additional 20 amp solar charge controller that is compatible with the lifepo4 battery and all the other trimmings. After reading a lot of what is probably hyperbole on from different articles on voltages and chemistry, I am struggling with how to incorporate it w/out mixing chemistry/voltages while still maintaining solar charging ability for the vehicle as well as the pack being self-sustaining away from the permanently mounted panel on the vehicle. So I am toiling with the idea of two different solar charge controllers in some manner but that just feels like a bad idea unless I come up with a way to isolate which controller is not needed at that moment.

I *think* you may be making this too complicated and maybe mixing your battery systems together in a way that isn’t helpful to either, if I’m correctly understanding your description.

IMO you’re better off keeping the house battery and camper battery systems separate, except for a 4 to 6awg cable appropriately fused at the starter battery, running to a DCDC charger for your LiFePo camper battery. Run all your camper stuff off the house LiFePo battery. Feed it with the current panel and controller. Forget trying to solar charge your starter battery. You have an alternator for that. Carry a LiOn jump pack if you need. Don‘t use your starter battery for anything except starting your car, running a winch or compressor if you have one and any driving lights. If you are running many or any high amp draw items “up front” you really might want to consider an AGM battery for your starter.

I’m currently running what I think it’s similar to what you want to do, but with the systems separated. I have a Northstar AGM starter battery (standard lead acid battery works just as well, which is what I had previously) with a 6 AWG cable running back to my truck bed feeding into a DCDC charger for my camper battery. My fridge is hardwired to the battery, with a fuse and everything else runs through a circuit breaker and a switch panel. I don’t run a lot of things, but everything I use is 12 V. I had a 500 W victron inverter I never used so I took it out for weight savings. I don’t miss it at all. Really anything you need to be charged can be done through 12 V as @Martinjmpr described above.

While I have a cable gland and wiring in the roof of my camper, I’ve never bothered to install permanent solar because the DCDC charger does such a good job and I’m rarely stationary for more than over night. On a 100 AH Battleborn I can run all my systems for at least three days without moving. I do have 100 W portable solar panel, and used it once over a five day period where we were mostly parked, but I’m not sure I even needed it then.

Hooking up a DCDC charger and running a cable along your frame is pretty simple. Not something to be concerned about doing. Simpler is better!

 

[67cj5]

A Dometic CF 25 draws 600 Watt-hrs per day when set at 35 F or 2 C in 100 degree heat. A 150 watt solar panel is a minimum to run this fridge without any help from the alternator in my truck. I find that real world solar panel power outputs need to be derated to 73% of their listed value when placed flat on a vehicle so where 100 Watts would be marginal in theory the reality is that you will need at least a 120-150 Watt panel.

That said, a 50 Amp-Hour battery is an absolute minimum IF it is a LiFePO4 12v battery. I use a 100 Amp-Hour Battleborn. If you are using a lead acid you will need a minimum 100 Amp-Hour battery and 150 Amp-Hours is more realistic. With lead acid you will need a larger panel, I suggest 200 Watts as a minimum, since lead acid charges.more slowly and less efficiently.

Cheers,

Grover

Struth 600w is a lot, my CF/CDF18 uses about 200/220w in temps of around 82/83*

 

[SanDiegoCruiser]

I have a similar setup. I use an AGM starter battery, a 2nd smaller battery that is isolated via a blue sea solenoid which then feeds a DCDC 15 amp Victron charger to charge my Lithium ion battery in the rear. I also have a 160W panel that charges the Lithium battery via a Victron MPPT charger.
A recent addition to the system was a 3 way switch that allows me to either charge the Lithium battery or the AGM battery via solar. It works great. The only thing I need to remember is to change the battery type to AGM via the Victron Bluetooth app so it so it uses the correct charge profile when I switch it over to AGM.
I’ve never really needed to solar charge the AGM, but it’s nice to have if I plan on parking my rig for an extended period of time to keep the starter battery charged.

Another unplanned benefit of this is if I have the solar charging the AGM battery, I can also configure the DCDC charger to also charge the lithium. So that means the solar panel could charge all three batteries at once. The DC DC charger would make sure the correct charging profile is used for the lithium battery. I have tried this in my driveway. I drained the lithium bat down to 70% and then the starter battery down to 12v. I parked the rig in the sun all day and came back to all 3 batteries charged to 100%. So it worked!

So what you are wanting to do is possible, it just requires some planning.


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[dstefan]

I have a similar setup. I use an AGM starter battery, a 2nd smaller battery that is isolated via a blue sea solenoid which then feeds a DCDC 15 amp Victron charger to charge my Lithium ion battery in the rear. I also have a 160W panel that charges the Lithium battery via a Victron MPPT charger.
A recent addition to the system was a 3 way switch that allows me to either charge the Lithium battery or the AGM battery via solar. It works great. The only thing I need to remember is to change the battery type to AGM via the Victron Bluetooth app so it so it uses the correct charge profile when I switch it over to AGM.
I’ve never really needed to solar charge the AGM, but it’s nice to have if I plan on parking my rig for an extended period of time to keep the starter battery charged.

Another unplanned benefit of this is if I have the solar charging the AGM battery, I can also configure the DCDC charger to also charge the lithium. So that means the solar panel could charge all three batteries at once. The DC DC charger would make sure the correct charging profile is used for the lithium battery. I have tried this in my driveway. I drained the lithium bat down to 70% and then the starter battery down to 12v. I parked the rig in the sun all day and came back to all 3 batteries charged to 100%. So it worked!

So what you are wanting to do is possible, it just requires some planning.


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Just curious what the need/logic for the second smaller Isolated battery (under the hood, I’m guessing) that then feeds the DCDC charger is? Just redundancy for your starter battery?

 

[SanDiegoCruiser]

Just curious what the need/logic for the second smaller Isolated battery (under the hood, I’m guessing) that then feeds the DCDC charger is? Just redundancy for your starter battery?

Yeah, it was an existing 2nd battery already installed before I got the Lithium. I really don’t need it, but if I’m ever winching a ton I can combine the two AGM batteries for more power.


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[MobileCabin]

Does anyone know if it matters what orientation the Blue Sea 285-Series Circuit Breaker - Surface Mount is positioned? I have a few wires that would be easier to connect if I mounted the breaker horizontally.

Thanks