Does anyone add Li batteries to their tow vehicle? - Fiberglass RV
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Old 03-17-2024, 08:35 PM   #1
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Name: zack
Trailer: scamp 13
California
Posts: 350
Does anyone add Li batteries to their tow vehicle?

I am thinking of putting a Li battery in my tow vehicle. I am wondering if people have experience with doing this or opinions about such an endeavor?

Here is my reasoning: A lot of days I leave my Scamp in camp and drive just my 4Runner for an hour or so (to get food or explore...). If I had a Li battery in my tow vehicle I could be charging that at 300 or 400 Watts and I could accumulate a lot of energy in just an hour of driving. The other benefit of having a Li battery in the tow vehicle (instead of the RV) is shorter wires from your alternator to the battery. These are benefits mainly for people who care a lot about charging from the TV alternator, rather than solar, which is the case for me because I am often in shade.

I am thinking about a spot in the center of the 4Runner right behind the from seat area. I think a group 27 size would fit in there pretty easily and even sort of snugly in terms of fore and aft motion. Probably I need to strap it or mount a bracket or something to make it safe and prevent side to side motion. (I will try to post some pictures.) But I am wondering: is this even a good idea at all? Are there things I haven't thought about? I am pretty new to this.

I am thinking I could utilize this power via a Jackery 1000 that I already have in my 4Runner which powers a 12 volt Dometic Cooler type fridge. I am thinking about a 24 volt LiFePO battery; that would charge the Jackery twice as fast, but maybe that is not so smart since the alternator is putting out 12 volts and maybe it is simpler and more efficient to stick with that? I really don't know what voltage would be best, all things considered, or the whole idea makes sense at all?

To be clear, I am planning to have a regular starter battery in the 4Runner (Interstate) and a regular lead acid battery in the group 27 box on the Scamp tongue (Interstate, RV type). This third battery behind the seat would be an additional source of power. There would be an appropriate dc-dc converter between the starter battery and the new added LiFePo battery. I am thinking that the advantage of the new LiFePO battery over all my other batteries is:
1) its' ability to accumulate stored energy at a high rate (400 Watts vs 70 Watts for the Jackery and less than that for the Pb-acid batteries).
2) Lots of cycles,
3) Light weight
(Did I leave anything out?)

Advice is much appreciated. I am pretty new to this, and I imagine there a lot of people with much more experience and knowledge!
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Old 03-17-2024, 08:43 PM   #2
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Name: zack
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Some pictures
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Old 03-23-2024, 10:07 AM   #3
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Name: M
Trailer: Shopping
California
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Stock vehicle charging won't accommodate a Lithium battery. (or do you mean another power bank?)

You'll need something designed to meet the voltage requirements. (most lithium batteries require more than 12.5 volts, there are a few that are designed to operate at a lower 12.8v) Cars don't output 24v.
This is going to be a lot more work than you think. You'll need to come directly off your alternator and into a converter/charger if you expect to rapidly charge. The size of your current alternator and current electrical demands may not provide as much power as you think.

In my opinion, it is cheaper and makes more sense to use solar and actively charge your battery all the time in your trailer.

I hope I understand what you meant.
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Old 03-23-2024, 10:36 AM   #4
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Name: John
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Does it count if your tow vehicle is electric?

Sorry. I’ll see myself out.
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Old 03-23-2024, 10:48 AM   #5
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Name: Don
Trailer: 2015 Escape 17A
California
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One solution is the one we selected. We have an Ecoflow system, which has an LI battery for storage, and also circuitry to safely and efficiently charge from shore power (120V AC), from a vehicle 12V DC outlet, and from Ecoflow folding solar panel arrays.

Outputs from the unit include 120V AC, 12V DC, 5V DC USB and USB-C
It's 26 lbs., and usually rides behind the drivers seat on the floor on trips.
We also have an additional Ecoflow battery for extra power storage capacity, so the system serves as emergency power back up for our home.
ecoflow.com


Edit: We have had occasion to use it in our home when power was out during a brushfire. We deployed the solar panel to recharge the Ecoflow, while simultaneously using the 120V AC to run our refrigerator and freezer, some lights, computers, and cell phone chargers.
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Old 03-23-2024, 11:03 AM   #6
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Name: Lynn
Trailer: '06 Scamp 16
Rochester, New York
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I've had an extra battery in my vehicle for years. I used to take it out to power audio equipment on parades. Now it adds extra battery capacity while camping. Its connected with a voltage sensing relay and, obviously, it charges any time I drive. It's an AGM for safety and voltage compatibility.
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Old 03-23-2024, 11:18 AM   #7
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Name: Hugh
Trailer: Weiscraft
California
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Any time you are designing a system that uses a 12V alternator to charge a LiFePO battery you must respect the amount of power (amps) the alternator is designed to source. Your TV draws power and then you add the battery charge draw. If you draw power near or at the rated maximum for the alternator you will likely shorten it's working life. Check out the Victron video on this subject; the video may be a melodramatic, but it makes a point.

A solution is to replace the TV's alternator with an alternator having a higher power rating... if such is available for your vehicle. Can you reduce the power draw by going to a more efficient frig like the Engle ? Rather than having multiple batteries in multiple locations with multiple charging requirements it seems to me that it would be simpler to have one LiFePO charging system with the LiFePO battery(s) in one place on the trailer.

regards, Hugh
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Old 03-23-2024, 01:01 PM   #8
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Name: Douglas
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I have had a system like that on my 4Runner for about 5 years. It works great. The system was built in the back passenger side corner of the cargo area. The 50Ah LiFePO4 battery is held in by a strap. It is fed by a dedicated 10ga wire from the car battery via a battery isolator, which is hidden down in the passenger side rear cubby. The isolator needs power (i.e. a hot lead when the ignition is on) to operate, so I do that by plugging the isolator into the power outlet on the tire well (see pic). Power then goes to a Victron DC/DC converter mounted to the fender well (the blue box) to boost the voltage to 14.2. Power then goes to the battery. The ground is a bolt under the plastic cover of the fender well, where it is connected to a shunt hidden there. The shunt display/gauge is mounted in the rear corner of the cargo area. A 12V power outlet under the gauge is one way to get power from the Li battery. There are various other 12V connectors too. There is a fuse block attached with Velcro to the battery case for all the circuits.

The second part of the system is a 100watt solar panel on the roof. It feeds down through the drivers side rear corner and over to the MPPT controller above the passenger side cubby. It has a switch to disable charging if desired.

The battery is continually charged at 9A or less when driving and about 5A or less when in the sun. They are additive. Both gradually decline to zero as the battery is charged. Battery BMS prevents overcharging.

This setup works great. I use it to charge the Li battery bank in my trailer when needed via a 10 gauge jumper to the trailer 7-pin connector. Doing it this way assures that the power from truck to trailer has to go through the Victron DC/DC converter in the trailer, keeping transfer at 9A or less. This prevents blowing a fuse or melting the jumper wire when the trailer batteries are low.
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Old 03-24-2024, 08:39 AM   #9
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Name: Gus
Trailer: Boler
Ontario
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I've had a system similar to "Air Doug" for a couple of years now. It works great.

The DC-DC charger is located under the driver seat and the lithium battery sits in a box in the rear passenger footwell as I needed the cargo area for the fridge and camping gear. I went with a 20A Renogy DC-DC charger throttled down to 10A, but, only because I hadn't found a Victron unit that could provide a similarly low charge rate. Don't know how I missed the one Doug has. I also went with portable solar panels so that I could keep my car parked in the shade and just have the panels in the sun. I have been contemplating having an additional panel on the roof but have yet to figure out the mounting and cable routing. What Doug has looks very well implemented.

The attached photo shows the combined charge rate with the vehicle running AND solar panels connected.
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Old 03-25-2024, 10:57 AM   #10
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Trailer: Casita SD
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related piggyback

My truck has an AC outlet described as 100W. Am I correct that a battery charger plugged into this would provide no significant charge? I had the thought of carrying an extra battery but it seems it would require a different charging source. I have little understanding of electricity.
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Old 03-25-2024, 12:07 PM   #11
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Name: Douglas
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Quote:
Originally Posted by ShelbyM View Post
My truck has an AC outlet described as 100W. Am I correct that a battery charger plugged into this would provide no significant charge? I had the thought of carrying an extra battery but it seems it would require a different charging source. I have little understanding of electricity.
Well, it would provide some charge, but the process involves changing from 12 volts to 120 volts in your outlet, then back again to a little more than 12 volts (whatever your wall charger provides). These conversions are not fully efficient, so you would lose maybe 10% each way.

A better way is to have a backup battery that you can charge using the 12 volt power outlet in your truck. If you buy one of the new power stations (so-called solar generators) that are so popular now, you can just plug it in and go, charging while driving.
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Old 03-26-2024, 10:04 PM   #12
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Name: zack
Trailer: scamp 13
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Isolated or non isolated?

Quote:
Originally Posted by Travellers View Post
Does it count if your tow vehicle is electric?

Sorry. I値l see myself out.
Lol. That痴 not such a bad question. I thought about that a little, like if you were towing with a model Y. But then it痴 a zero sum game, just transferring power from one Battery to another.

I think with my forerunner I can safely charge from the alternator with a victron Orion tr smart 12-12 30a, which would charge at 30 A when the conditions and RPM are sufficient to allow that. I知 not sure if I知 supposed to get the isolated or the non-isolated version. Does anyone understand that?
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Old 03-27-2024, 07:22 AM   #13
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Name: Douglas
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Quote:
Originally Posted by zack sc View Post
I知 not sure if I知 supposed to get the isolated or the non-isolated version. Does anyone understand that?
Isolated converters are supposed to prevent ground loops. I don't know much about it (I'm a geologist), but when I installed my inverter, there were lots of warnings to not have multiple grounds to prevent ground loops, which can cause RF interference. Since we use a cell phone booster, at times a wireless router, and mobile wifi hotspots, I would rather not worry about it. Isolated DC/DC converters are likewise supposed to prevent RFI.

Here's an interesting article:

https://www.solar4rvs.com.au/buying/...ideal%20choice.

Our neighbor camper in January in Tucson was towing their Bigfoot 17 with their Tesla Model Y. Interesting stories, but that's for another thread.
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