50ah lifpo4

[JINO]

I don't know much about wiring and batteries, but I want to add a 50ah lifpo4 battery under my rear seat and not have to wire it to main battery.
Would it be feasible to mount under the seat and run wires to a solar panel for charging?

Mostly I just want this to run the fridge. I'd like to use my ecoflow inside my tent for my wife's heated blanket and possibly a portable AC.

Do I just connect the positive and ground from the fridge directly to the 50ah or do I have to include a appropriate fuse?
How would a solar panel be wired to it?

Sorry for the stupid questions.

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[JINO]

Would this plug into the 50ah battery and charge it?

 

[Ratbert]

Is that also a DC-to-DC converter? You'll really want to use one so it'll charge decently while traveling.

 

[Jeepeto]

DC to DC charger would be the easiest solution. I've done this in my work truck with a 100Ah LFP and a 20 amp DC to DC charger. It works fantastic, and powers my truck fridge more reliably than my dual battery/solar setup on the Jeep. 50Ah will do you fine if it isn't super hot. For reference, with a Dometic CFX3 45, the truck fridge is good for about 48 hours in texas summer with the truck parked in the sun. It will last for 3-4 days if parked in the shade during summer, you will be right at about half that at 50Ah. Adding solar will only help, but LFP batteries are very cheap these days, it may be just as easy to add battery

 

[GATORB8]

DC to DC charger would be the easiest solution. I've done this in my work truck with a 100Ah LFP and a 20 amp DC to DC charger. It works fantastic, and powers my truck fridge more reliably than my dual battery/solar setup on the Jeep. 50Ah will do you fine if it isn't super hot. For reference, with a Dometic CFX3 45, the truck fridge is good for about 48 hours in texas summer with the truck parked in the sun. It will last for 3-4 days if parked in the shade during summer, you will be right at about half that at 50Ah. Adding solar will only help, but LFP batteries are very cheap these days, it may be just as easy to add battery

I'd 100% just do a DC-DC charger, wish I'd never screwed with solar on the trailer (although it looks cool). I bought my battery setup on the trailer from LiTime, they have a new "mini" 100 AH that's not too much bigger than a 50.

https://www.litime.com/products/lit...XSxqQuRQmd4Mgqi9dJFE87_BFnOiulCsaAmI2EALw_wcB

 

[JINO]

DC to DC charger would be the easiest solution. I've done this in my work truck with a 100Ah LFP and a 20 amp DC to DC charger. It works fantastic, and powers my truck fridge more reliably than my dual battery/solar setup on the Jeep. 50Ah will do you fine if it isn't super hot. For reference, with a Dometic CFX3 45, the truck fridge is good for about 48 hours in texas summer with the truck parked in the sun. It will last for 3-4 days if parked in the shade during summer, you will be right at about half that at 50Ah. Adding solar will only help, but LFP batteries are very cheap these days, it may be just as easy to add battery

So I would be charging the 50ah with my jeep's cigarette socket??

I only camp when it's cool/cold weather.

 

[GATORB8]

So I would be charging the 50ah with my jeep's cigarette socket??

I only camp when it's cool/cold weather.

You'll need to hardwire a 20 amp, but I'm sure there are some options out there that would work on <10 amps from the socket.

 

[Left Field]

So I would be charging the 50ah with my jeep's cigarette socket??

I only camp when it's cool/cold weather.

Yes, that can work.

I'm using this DC-DC charger and have been pretty happy with it. It's maximum output is 8 amps which limits its input demand to somewhere around 10A - which would be fine for a vehicle cigarette socket.

https://powerwerx.com/dcdc-charger-lifepo4-8a-adjustable

There are some nice larger units but they would need to have dedicated larger wiring installed. An example would be this:

I agree with others that the DC-DC charging solution is probably the simplest.

I'm running a 23 AH lithium battery; it has been enough to run my 50L fridge for about 1 - 1-1/2 days, depending how hot it is. That means I have to drive at least every other day to keep it charged.

If you are going to spend more than a couple days without driving then it would necessitate either a larger battery or adding solar.

For the 12V cigarette outlet you'll want to make sure it is only powered when the engine is on, otherwise it will charge your Lithium battery off your vehicle battery and run it down.

The vehicle cigarette outlet is fused so you are covered there for circuit protection. You should have a fuse from the battery to the fridge however; this would be for the new 12V cigarette socket that you would connect to the new battery (to plug the fridge into).

Regarding the 'camping during cool / cold weather' - note that Lithium batteries generally cannot be charged below 32F. Some batteries have heaters to resolve that issue.

LF

 

[AndySpill]

I don't know much about wiring and batteries, but I want to add a 50ah lifpo4 battery under my rear seat and not have to wire it to main battery.
Would it be feasible to mount under the seat and run wires to a solar panel for charging?

Mostly I just want this to run the fridge. I'd like to use my ecoflow inside my tent for my wife's heated blanket and possibly a portable AC.

Do I just connect the positive and ground from the fridge directly to the 50ah or do I have to include a appropriate fuse?
How would a solar panel be wired to it?

Sorry for the stupid questions.

These aren't stupid questions Jino; they're smart ones. Your asking the right things, it's just that your ignorant on this subject matter, not stupid.

Stupid would mean that you're incapable of learning or asking questions maybe that make no sense; you're not.

To answer your questions in the order they were posed:

I want to add a 50ah lifpo4 battery under my rear seat and not have to wire it to main battery.

As a generally rule LiFEPO4 (Lithium Iron Phosphate, which for those reading and new to this, is an entirely different chemistry from Lithium Ion) batteries can be positioned in any orientation. You may know this; I include it for those reading who may be new to this stuff.

Yes, Lithium Ion and Lithium Iron Phosphate batteries both use Lithium, but in the world of chemistry, there is a world of difference between the elements on chemistry's periodic table, and the compounds formed by them. E.g. Don't put sodium or chloride on your food, but you want to sprinkle sodium chloride (table salt)...go for it if not watching your blood pressure.

Of course there are quality differences among LiFePO4 battery manufacturers but batteries using this chemistry are as a rule of thumb considered safe from the dangers of fire, explosion and off-gassing that allow them to be placed in the cabin area of a vehicle.

I should qualify that. It's not that the LiFEPO4 chemistry is so safe (or not safe) it's that these batteries are almost invariably outfitted with a BMS (battery monitoring system) that prevent them from being exposed to charging or draining scenarios that could prove dangerous.

As you may know LiFEPO4 batteries generally have many more cycles that lead acid ones (including the AGM battery/ies under the JL hood-AGM (absorbent glass mat) being a type of lead acid battery that is sealed and generally also ok for in cabin (as opposed to just under the hood) use). This LiFEPO4 chemistry permits a further depth of discharge than lead acid chemistry batteries without ill effects, but needs temperatures above freezing to accept charge short of battery warming blankets or LiFEPO4 batteries with built in heaters (expensive.) As a generally rule of thumb, taking a lead acid battery below 50% of its full charge (a.k.a. DOD: depth of discharge) is ill advised.

And yet if you plan on camping in Northern California for example, where it can get cold, an AGM battery may be a better choice, much that you'll need it to be larger in amp hours than a properly size LiFePO4 one due to the DOD limitations of its chemistry.

Let's take a step back. Why a 50 amp/hour battery? I'm not saying this is the right or wrong size. But without knowing the specifics of your fridge, including the wattage it draws, choosing the right battery size is hard. Does this fridge have a voltage cutoff that you can set, to prevent the battery from being drained too much?


And of course that battery needs to be recharged, where such electrical current can come from one or more of these 3: solar panels, plug in 120 VAC (shore power) or the vehicle alternator. Battery sizing is also about considering your access to these 3 power sources and the duration with which you will likely go without such access. For example, if you're out camping in the woods the first two power sources won't help. If you don't want to run your engine or can't at the campsite, to have the alternator charge this battery, that's another consideration. So are the presence sunny days, even in your California, the length of day during parts of the year, and the fact that about 1/2 of your solar panel's effectiveness will be untapped if it sits on your vehicle roof horizontally, rather than at about a 37 degree angle (longitude in the middle of California.)

I'd like to use my ecoflow inside my tent for my wife's heated blanket and possibly a portable AC.

Do you plan on charging the Ecoflow (portable power station) only before leaving for a trip, with no expectation on charging it again until you get home?

Do I just connect the positive and ground from the fridge directly to the 50ah or do I have to include a appropriate fuse?

The size of your system, while certainly not big, is also not small when compared to, say, one of those solar trickle chargers that sits in the dash and plugs into a 12V DC port.

Given this size, I cannot see you using less than a 100 W solar panel, likely larger if you only go that power route, or if you want to alternatively or additionally use your alternator for power.

With a properly sized solar panel setup consistent in size with a 50 amp hour LiFEPO4 battery you will need a solar controller. These devices usually have connection points for the solar panel, battery, and appliance, none of these 3 directly connected to one another but only through the controlling mechanisms of this controller.

Controllers come in two basic varieties: the cheaper PWM (pulse width modulating) controller, which is less efficient, dissipating excess power as heat, and the pricier but more efficient MPPT (maximum power point tracking) variety which seek to give you the maximum power (watts) by regulating the components of watts: volts and amperage.

Jino, let me leave you at this point of departure. I am going to refer you to the Renogy DCC30S product, not because it's the best, but because it is adequate for your needs and provides ability to charge from either a solar panel or alternator.

Here is it's manual https://www.renogy.com/content/RBC3050D1S-G1/RBC3050D1S-Manual.pdf where on page 15 it shows all the setups, including fuses. This happens to be an MPPT solar controller in addition to a DC to DC charger as mentioned by others prior. Your LiFEPO4 battery in that picture is considered the "house" battery.

When people want to add shore power to this they often find themselves hooking a DC power supply or battery charger directly to the battery, or the device's alternator input.

I'm sure I've raised at least as many questions as those I've hopefully answered, but will stop here until I know more of your situation.

 

[Jeepeto]

So I would be charging the 50ah with my jeep's cigarette socket??

I only camp when it's cool/cold weather.

Depending on how long you drive each day a small charge controller may work fine. Just need to make sure the Jeep will run long enough to charge.

I generally see ~1Ah/hour in cooler months on my Dometic. This means the fridge would require 24Ah/day to keep running continuously. As long as you can provide that you should be fine if it stays cool. If you have a 6 amp charger this means 4 hours per day for continuous use. (6 amps x 4 hours = 24Ah) If you only plan to use on the weekends and your charger keeps the battery topped off during the week days (no fridge use) you would start the weekend with 50Ah. Try not to drain it too deep (BMS should cut you off anyway) but you'd be able to get away with much less charge per day.

 

[THAW]

Do I just connect the positive and ground from the fridge directly to the 50ah or do I have to include a appropriate fuse?

Always use a fuse as close to the power source as possible (ideally within 7 inches), sized to protect the power wire.

Wire gauge should be based on distance and current draw from the device(s) requiring power. You can find wire gauge calculators online (Blue Sea Systems has a good one).

 

[AndySpill]

Always use a fuse as close to the power source as possible (ideally within 7 inches), sized to protect the power wire.

Wire gauge should be based on distance and current draw from the device(s) requiring power. You can find wire gauge calculators online (Blue Sea Systems has a good one).

Shore power, solar panel, alternator power and a battery are all power sources and therefore the term "power source" risks conveying ambiguity.

Solar fuses, at least as I was trained, typically belong closest to the battery and solar panel output, again, consistent with the picture I linked, where specific product manuals don't otherwise say to act differently.

 

[AndySpill]

So I would be charging the 50ah with my jeep's cigarette socket??

I only camp when it's cool/cold weather.

You would not. Between the starter batteries and your LiFePO4 (house battery) must exist tech (e.g. a DC to DC charger) that is aware of not only the house battery's (and often the starter battery's) state, but the fact that your proposed house battery is composed of a different chemistry that your starter batteries, even isolates the starter batteries if they drop too low (setups that don't know that the vehicle's engine is on.)

LiFePO4 batteries charge at higher voltages and in different ways that AGM batteries: another reason you can't direct connect them to your starter battery/batteries. Still more, if you are going the DC to DC charger route I would make sure that you are getting one that can handle the JLs smart alternator, which regulates its voltage (to save fuel) based on need of the starter batteries. (They product I linked may be overkill for you, but does work with smart alternators. In the hard core solar RV world, Renogy products though are often frowned upon for not being as battle tested as say Redarc products, so it's all relative.)

Such DC to DC chargers, I'm to understand can up the voltage from what might be insufficient from the smart alternator to charge LiFEPO4 chemistry batteries.

Jino: in this world pretty much the only thing that connects to your battery is a solar charge controller, or DC to DC controller, or, as per my linked product, a product that does both. We generally try to not connect power sources or appliances directly to the battery, (although in some DC to DC charges I think direct connect between appliances and the battery may be ok) but run them through access points in the controller: solar or DC, or a combined unit.

 

[THAW]

Shore power, solar panel, alternator power and a battery are all power sources and therefore the term "power source" risks conveying ambiguity.

Solar fuses, at least as I was trained, typically belong closest to the battery and solar panel output, again, consistent with the picture I linked, where specific product manuals don't otherwise say to act differently.

What's a solar fuse?

Your training claim is ambiguous, what kind of training do you have?

While both a battery and a solar panel are technically power sources, fusing a single solar panel is unnecessary (they are rated to handle their own short circuit current). Fuses are required in a panel array if the combined short circuit current of the array exceeds the maximum series fuse rating of a single panel.

 

[GATORB8]

What's a solar fuse?

Your training claim is ambiguous, what kind of training do you have?

The solar fuses I've seen for auto use look like the old glass fuses you see in a 12V cigarette plug in. Meant to go in a holder that works in the standard connectors.

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