LifePO4 upgrade

[Isaac-1]

A 50 watt solar panel is basically a glorified battery maintainer, I had a 55 watt panel on my 28 ft sailboat 21 years ago, and it barely maintained power for the bilge pump and a few lights.

The previous owner of our 28 ft Class motorhome installed 400 watts of solar panels, in 2022 I upgraded the battery bank to 420AH of LiFePo4 batteries, with 400 watts of panels if I had sunny weather I could generally come close to fully recharging things each day, using a traditional absorption style propane RV refrigerator, and still have enough power to run whatever LED lights, computer, and cell hotspot in the evenings that I wanted to.

This year I upgraded to a total of 1,100 watt of solar panels for a big 5 week trip to Yellowstone and Grand Tetons, camping off grid for much of the trip up to 11 nights in a row before going to a place with hookups.
On this trip I was also powering an ice chest style DC refrigerator /freezer, as well as a Starlink mini for internet, and sometimes an electric blanket, 1,100 watts of panels was just enough, on a typical night I would be down to around 50% battery capacity by morning when it would start recharging, even then a few times it would only make it up to 80-90% by sunset due to either shading from trees or having partly cloudy days.

 

[John From Detroit]

Just now Harbor Freight has their 200 watt folding portable panels for $200 dollars These are like the Jackery and come with both the standard solar panel connectors and an adapter to charge a Jackery (or their Predator line)

Checked it out this AM. It turned on the "Charge light
on my Jackery.

I plan to use it for portable radio stuff.. I need an additional adapter for my other batteries however.. Not a problem

 

[DonTom]

Just now Harbor Freight has their 200 watt folding portable panels for $200 dollars

I have one of those with me right now, one of my four solar panels--all different--that I do in series for this Y2K RV. They have electricity here at Gilbert Ray, so I do not need them here, but my next stop, depending on the weather, could be Gunshot Wash or Organ Pipe (if it is open during this shutdown), where they will get a lot of use.

-Don- Tucson, AZ

 

[Gary RV_Wizard]

A 50 watt solar panel is basically a glorified battery maintainer, I had a 55 watt panel on my 28 ft sailboat 21 years ago, and it barely maintained power for the bilge pump and a few lights.

So true! A 50W panel in full sun only yields about 3.5A at charging voltage (14v), so you are lucky to gain 10 amp-hours per day in northern US or the off-seasons when the sun is lower. The results vary with location, time of the year, panel angle, etc., but a 50W panel is only a little more than a trickle at best.

 

[Rorobert]

No, I haven't.

 

[Rorobert]

I'm putting in a Temgot 300AH back by my panel, it'll be right over an axle. More solar panels will have to wait till next summer. Thanks a lot guys. Don I have 3 HD EVO's and a Suzi for the desert.

 

[Rorobert]

Well the hits keep coming. I found I have a 100w solar panel with a 30 amp solar charger, a voltmeter, and a battery disconnect next to my converter/fuse panel. I'm assuming I'll need to run my new battery through that disconnect and meter panel before going to converter and after going through a 60 amp breaker?...right? ...and what about the power from my alternator while driving, anything I need to do there? I knew about the battery disconnect and volt meter before of course, but didn't know it was part of solar package, or that the panel was 100w, or anything about a solar charger.

 

[Gary RV_Wizard]

At the end of the day, that solar panel & charger is just another 12v source (actually more like 14v) that feeds the battery. By the time the volts & amps come out of the charger, it's plain old DC electric.
Yes, the disconnect should be wired in so it does indeed disconnect the LiFePO4 battery. And it's certainly desirable that the meter panel still works.
That 60A breaker is between the converter/charger and that 6 ga wire from the trailer tongue? It's less important if you move the battery closer, but it's already there so keep it. However, you may find that it trips a lot when in charging mode. The lithium battery can draw a lot more than 60A if the state of charge is very low. Just how much it can draw is managed by the BMS built into the battery, so depends somewhat on the make of battery you choose. Pay close attention to the specs.

The power from the tow vehicle's alternator to the trailer plug is almost surely limited by the tow vehicle. Typically on the order of 20A-30A max. From the trailer plug it travels down that 6 ga wire that leads from the tongue to the new battery location. You could probably use 10 ga instead of 6 ga for that stretch of wire if you want. Hopefully the limiter in the tow vehicle source is an auto-reset breaker, because the lithium battery can easily try to draw more than 20-30A if the battery is discharged very far.

I suggest you sketch out how you think the wiring will look after your mods and post it here. It's a lot more productive if we can see what we are talking about.

 

[16ACE27]

If your Lead Acid battery is happy with that 14 feet of 6 gauge wire, the LFP battery will be as well.
BUT, that inside/warmer location would be a plus if camping in below freezing temperatures. LFP batteries have temperature limits. Many people have upgraded to LFP batteries AND moved them inside at the same time. They are sealed.
Any money spent on LA house batteries these days is money wasted.

 

[Rorobert]

Just back from being out of town for weekend. Battery is a TEMGO. I'll get some pics tomorrow and try and draw a little sketch of my plan. High points of battery.

• 【Massive 300Ah Capacity & Reliable Low Temp Protection】Built with high-quality LiFePO4 cells, this 12V 300Ah lithium battery delivers stable performance, higher energy density, and over 5000 cycles. Includes low-temperature cutoff to protect battery health in freezing conditions.
• 【Smart Touch Screen & Bluetooth App Monitoring】Check battery status in real time with the integrated touch display — no extra tools needed. Stay connected via Bluetooth and monitor performance on your phone with the TEMGO App (iOS & Android supported).
• 【200A BMS for Superior Safety】The advanced 200A Battery Management System (BMS) safeguards against overcharge, over-discharge, overcurrent, short circuits, and overheating. Safe, stable, and environmentally friendly — no risk of fire or explosion.
• 【Self-Heating for Cold Weather Charging】Built-in automatic self-heating activates when battery temperature drops below 32°F (0°C), ensuring safe charging even in freezing conditions. Heating stops once the battery reaches 41°F (5°C), then charging begins.
• 【Versatile Use & 5-Year Warranty】Install in any direction without leaking or damage. Ideal for RVs, campers, solar systems, and off-grid setups. Backed by TEMGO’s 5-year warranty and responsive 24/7 customer service for peace of mind.

 

[Rorobert]

Should be able to see bottom shelf (behind pantry door 99% of time). Battery would be on it's side so I can see window. Schematic should show my idea for wiring. The only other thing on 30 amp self resetting breaker up front is black wire which goes to junction box and then to trailer connector, and t6he blue and white, which together with the white wire on neg. go up the front of RV in front wall. I was thinking the black would be aux. power from truck and blue/white & white come down in front wall from roof solar panel. Where am I off on this?

 

[Rorobert]

If this won't work, I'll just do as 16ACE27 said and keep in on the tongue. I just know it's warmer in the camper, and quite a few times I've had to wait for my garden hose to thaw out in the morning in Arizona at different parks.

 

[Gary RV_Wizard]

The only question I have is the wiring from Trailer plug charge line (Aux 12v) to the battery +. If you connect to the tow vehicle trailer plug when the battery is discharged, the battery will immediately try to draw as much as 200A (the BMS limit) thru the trailer plug. It can't deliver but a small fraction of that, so needs either an auto-reset breaker for self protection OR a DC-DC charger to limit the charging current. Without one of those, you will likely trip whatever fuse or breaker in the tow vehicle that feeds the trailer charging circuit.

 

[Rorobert]

Where would that go?

 

[Rorobert]

And won't that manual resetting breaker between the lithium battery and the battery switch limit it?

 

[Gary RV_Wizard]

And won't that manual resetting breaker between the lithium battery and the battery switch limit it?

Perhaps I'm not reading the [rather small] schematic correctly, but I don't see where that is. The only switch I see goes to some Control Panel. Where is the trailer plug in that diagram? I'm envisioning there to be a long 10 ga (30A) wire from the plug out on the tongue back to the battery positive. Is that not the way it is?

 

[Rorobert]

No there is no 10 ga from trailer plug going to battery now. If you look at my pic under the trailer you'll see 3 wires that go back towards battery in the sheathing. Two go to emergency brake switch and one goes the trailer jack, and I don't think they're 10ga but maybe. I'm thinking the black 10 ga. coming from junction block to the bottom of the 30 amp self resetting breaker is the aux. 12v wire, which I guess does go back to battery, I thing the blue/white is from solar panel. So I could put a 60 amp self resetting breaker their or a DC to DC charger there.

 

[Rorobert]

But that would mean the AUX. 12v from truck is already going through that 30 amp self resetting and also through the 60 manual reset I have in back.

 

[Rorobert]

If it kicked out both the 30 A self resetting and the 60 amp manual resetting I'd just have to wait till I get to where I have either shore power or generator. Suppose I could change that 30 amp resetting to a 60 amp resetting or put a DC to Dc charger between that aux black line and the 6 ga going back. The 60 amp manual restting breaker in sketch above is above right end of battery with just the face through the wall.

 

[Gary RV_Wizard]

You need a breaker that trips BEFORE the wiring in the truck or the plug itself burns out. There's probably a 20A or 30A fuse in the truck, but blowing those are often a pain to replace. The 60A breaker doesn't protect anything that can't handle at least 60A of current.

When I said 10 ga wire, I merely meant a wire that can handle 30A, which I''m assuming is the max the plug and tow vehicle can handle. 10 ga is rated for 30A. Larger ga than needed is OK, but not smaller. But a larger fuse or breaker is not.