Where to install lithium battery in Minnie 2500FL

Greg2500RL · 08-08-2022, 08:28 AM

Has anyone installed a battery(s) for solar in their Minnie 2500RL? I am getting ready put 2 225 watt solar panels on the roof and install one 170 aH LiFePo4 battery inside. I am wondering where people are putting their batteries and charge controller for this purpose. Some options I am considering are 1) behind the recliner, against the front wall, 2) inside the starboard cubby beside the recliner. It is hard to work inside the cubby due to the cramped space. The factory solar wiring terminates behind the starboard recliner, so I will likely put my charge controller there too.

Greg2500RL · 08-13-2022, 09:30 PM

I just finished installing my panels, 170AH LiFePO4 battery and 1000W inverter. I did not use the solar ready roof vent or wiring. They lead to the front of the trailer behind the theatre seats.

I decided not to replace the lead acid factory battery, but to keep it and switch back and forth between the lithium and lead acid batteries using a battery selector switch which never connects the two batteries together.

If I run into freezing temperatures, I can just shut off the solar panels with my solar panel disconnect switch and shut off the switch to the lifepo4 (lithium) battery. This will protect the battery from receiving a charge in freezing temps. I just need to be diligent with this until I can rig up a low temp shut off for the solar panels. I installed the lithium battery inside the closet closest to the bedroom, in the bottom compartment. I reinforced under the thin panel floor of the closet to support the 48 lb. battery.

I disconnected the red 6 AWG battery cable on the WF8955 converter and extended it to the battery selector. I ran the positive cable from the lithium battery to the other pole of the battery selector. I then ran a 4AWG wire from the output of the switch to the terminal on the converter from which I moved the factory battery cable. I installed a 1000W inverter which I had as a spare, in front of the lithium battery on the floor of the closet. I will just run extension cords from this to our TV and my laptop, etc., until I rig up some sort of an automatic transfer switch solution.

When plugged in to shore power I can add some charge to the lithium battery from the factory, lead-acid designed, converter. It won't charge it up past 13.6V but my solar panels can top it up if necessary. I generally won't intentionally select the lithium battery when connected to shore power. I have a lithium ac charger form my 170 AH battery if I need to top it up using shore power or my generator.

Using this hybrid system, I can still have off grid power in my trailer using the lead acid battery, realizing it's capacity will be much lower in cold temps but could use it in a pinch without worrying about ruining my lithium battery.

lenore · 08-13-2022, 11:04 PM

Great job, sounds pretty useable to me.

Marine359 · 08-16-2022, 09:54 AM

Quote:

Originally Posted by Greg2500RL

I just finished installing my panels, 170AH LiFePO4 battery and 1000W inverter. I did not use the solar ready roof vent or wiring. They lead to the front of the trailer behind the theatre seats.

If I run into freezing temperatures, I can just shut off the solar panels with my solar panel disconnect switch and shut off the switch to the lifepo4 (lithium) battery. This will protect the battery from receiving a charge in freezing temps. I just need to be diligent with this until I can rig up a low temp shut off for the solar panels. I installed the lithium battery inside the closet closest to the bedroom, in the bottom compartment. I reinforced under the thin panel floor of the closet to support the 48 lb. battery.

Using this hybrid system, I can still have off grid power in my trailer using the lead acid battery, realizing it's capacity will be much lower in cold temps but could use it in a pinch without worrying about ruining my lithium battery.

Hi Greg,
Nice setup, and good thinking to use LA batt as backup. But I’m wondering why you would worry about accidentally charging your LiFePo4 in freezing conditions. You’ve mounted it in a heated space, so as long as you don’t shut off the furnace, the battery temp will maybe drop a few degrees below cabin temp. We mounted our LFP in our pass-thru where it gets colder than the closet. We traveled a couple of months in shoulder season, with about 25 days of freezing nighttime temperatures. Just to be sure, I checked the battery temp when outside temps were below freezing, and the battery was about 45F while cabin thermostat set at 65F. We never had a problem charging or discharging our battery in outside temps as low as 15F. So, you may want to check your battery temp during freezing outside temps before you exert time and money to engineer a fix that shouldn’t be needed. Besides, at 170ah, I’m guessing you have a BigBattery Owl like ours. It has automatic BMS cold charging shut off (thermal management system).

No1Hunter · 08-28-2022, 04:34 PM

Jim,

Question for you. Do you remove your batteries during the off season? And, if you do, do you keep your TT pulled in, so you can run dehumidifiers, etc? Also, any issue with your solar panels & controller if the batteries are removed?

There are times when we may have very cold weather and no snow. So, the solar panels will be, or attempting to charge the batteries if I leave them connected.

Marine359 · 08-28-2022, 04:58 PM

I leave my LiFePo4 battery in the pass thru all year. I leave it turned off at the battery I/O switch. When I want to take a trip in the winter, as we will this January, I turn on the battery and turn on the furnace. When the pass thru is over 40F, I plug into shore power to fully charge the battery. Then I begin de-winterization. I keep everything buttoned up, so seldom have humidity issues. If I see any condensation on inside windows, I use a damp-rid jar. My portable panel doesn’t try to charge because I keep it in the trailer’s closet. For rooftop panels; they cannot charge when the battery I/O is switched off.

Since you don’t have a battery I/O switch, you can accomplish the same thing by connecting the charge controller leads through a resettable breaker switch, or by installing bus bars with a disconnect between the bus bars and the batteries.

Of course if your battery has low temperature bms protection, you don’t have to sweat it as much because the bms will not allow the battery to accept a charge below 32F.

No1Hunter · 08-28-2022, 06:16 PM

Thanks for the reply, Jim. Though Winnebago hasn't sent me a wiring diagram specifically for my TT model, they did send me a Micro Winnie external wiring diagram and it shows the solar controller being wired directly to the battery. It does not go through the battery cut-off switch.

So, what you are saying is installing a simple disconnect between the battery and the control is all that is needed. You're right about the low temp bms protection and when buying LiFePo4 batteries, that is an important item to look for.

Marine359 · 08-28-2022, 06:58 PM

If your solar charge controller is wired directly to your batteries, you need a way to cut that circuit. It can be a disconnect, or a resettable breaker. But if it’s a disconnect, you need to ensure it disconnects EVERYTHING.

No1Hunter · 08-28-2022, 07:17 PM

Quote:

But if it’s a disconnect, you need to ensure it disconnects EVERYTHING.

Everything connected to the controller, correct? The drawing shows it being connected to the battery side of a 30amp breaker that then goes to the slide motors and the battery cut-off switch. So, the disconnect or resettable breaker would need to be between the controller and that breaker.

As you know, I am incorporating a portable solar panel and will be installing a second controller. I anticipate the output of each controller going to a buss bar
or a victron Lynx Distributor and them to the battery(ies). It would appear the lead to the battery that would be a good place for the resettable breaker.