2025 Micro Minnie FLX Extra Battery and Solar Charge Issues

[alannsalter]

Hello all, I am new to the forums but did check to see if this topic has been addressed before. I didn't see the issue I am having, but if I missed it, please point me in the correct direction, thanks in advance.

I ordered my FLX from the factory to get a furniture configuration my dealer did not have. It was shipped to the dealer who delivered it to me and I assumed that it was delivered to me as it was delivered to them by the factory. The past year and half has brought much frustration with poor charging ability from the solar system and started me on a path of discovery. An internet search told me that the FLX trailer is configured in the factory and shipped with ONLY the Lithionics battery. My trailer was delivered to me with a GSM battery as well on the trailer tongue like other non-FLX trailers. I must say that the installation, to include the wiring, looks very professional, and since it was delivered to me with the battery I assumed upon delivery that it was supposed to be a part of the trailer and was designed by and installed by the factory. NO ONE ever told me that a second battery would be added to the trailer and I certainly didn't authorize anyone to change anything from the factory. I have spoken with the service department at my dealer who denies putting the battery on the trailer, but has indicated that by the cheap brand of battery that was installed they have an idea as to who may have done it. They refuse to share that information with me. They did confirm though that the GSM and Lithionics battery should not be on the same circuit and thus should not be charged together.

It appears that the presence of the GSM battery is causing an issue with the MPPT Solar Controller. Since the main Lithionics battery powers everything, the GSM battery never drops low and I think causes the solar controller to read the battery system as full or nearly full, thus never moving the charging system out of float which may cause the low charging speed. I took it to the dealer who simply removed the battery and taped off the wires. However, all that did was seem to leave an open circuit on the solar charging system and the system initially didn't recognize the presence of any battery. I figured out that the MPPT setting were set for the GSM battery and then it recognized the presence of the Lithionics battery, but won't send any charge to it. I hooked a nearly dead RV battery I borrowed from a family member back up to it and not only did the system begin charging again, but it moved to bulk which seems to confirm my suspicions that the GSM battery is wired into the main charging system seemingly interfering with the charging ability of the Lithionics battery. The GSM battery had three wires attached to it. First, a 6 gauge red that went to the positive power bus on the chassis right behind it; second, a 6 gauge white wire that went to the chassis just in front of it; and, third, a 10 gauge white wire that disappears into the cabin of the trailer. I feel like the two 6 gauge wires would be fairly easy to remove, but the 10 gauge would cause some tracing, unless someone knows who wired it and could tell where the other end is so that I could disconnect it hopefully taking that open loop out of the circuit and thus closing the circuit again on the solar system.

My questions for anyone that might be able to offer insight:
1. Am I, and internet AI, correct that the trailer should have been delivered WITHOUT the GSM battery? If so, any idea why it would have been put on?
2. Anyone have any idea where the extra 10 gauge white wire would go?
3. Anyone else have the same issue with an after market and unauthorized battery being installed (possibly incorrectly)? If so, how did you handle it with your dealership.

Thanks,
Alan

 

[Morich]

Not having run into "GSM", I id a search on AI and came back with this:

I would first have to assume that somebody at the dealer was involved in this getting on an RV. One reason for thinking this is that an RV builder would nothave anything involved in batteries for cell phone use, so highly unlikey to get confused there! But at a dealership ( sometimes called stealership?) there is a lot more chance of thing s getting switched out while the RV is in the back lot!
I would be going directly to Winnebago and bypassing the dealer if they are not willing to make it right and quick!
This actually begins to sound like a trailer that was sold, where somebody made a change and then returned the trailer?
But if you bought a "new" trailer, it should be new!

 

[alannsalter]

Thank you Morich! And, you are correct, in my haste I mixed up my acronyms, I am referring to an rv battery not a cell phone. You also made me go back and take a second look at the battery (pictured above) and I realized that it does not appear to be an AGM battery either. That is what the MPPT controller was originally set for, an AGM, and that may not have been correct either. I will add that to the equation. Thanks.

 

[Morich]

Ok, easy to jump too high and too soon if I don't look carefully! so we may need to start over?
I think I see "deep cycle marine" Hiding part way under the white wire in last picture?
I believe that would make it somewhat of a hybird lead acid. Meant for longer lasting and a bit deeper discharge like we need if used for a trolling motor on a boat as the more common use. Older design than lithium, AGM, or others but good for some uses.
I use them for my RV as rarely boondock without hookups.
They don't give the quick burst of power we may like for engine starting but for 12VDc coach use like lights, water pump, etc. they are better for that longer, slower use than the standard lead acid designed for engne starting. The CCA (cold cranking Amps) at 600 is not good for cranking a big engine in cold weather!
So how it is used may be the main points as this is very much a lead acid but I think the difference is mainly thicker plates? That needs to be checked!
But not good to use connected directly to lithium as this likes a float (charged) voltage of 12.7 and lithium needs to top out quite a lot higher to get the best use of them. Main point is that we can't charge the lithium fully without overcharging this lead acid if they are connected directly to each other!
For motorhome use, this would be somewhat step up as it lets us "deep cycle" this battery for inside power uses while not needing any changes to charge from the normal truck charging system. On a trailer wth no engine starting issue, this might be looked at as a step above the normal lead acid but then if thrown in with lithium, it needs we need to keep them seperated if only charging from one source.
Not at all clear to me on some points, though! But, yes, I would expect some problems on setting up charging on two far different battery types! There may be something already added but getting one topped off without overcharging the other is one biggie to work around?

 

[Steph-WO]

First, your dealer should have your order and the day it arrived from the factory. Ask to see all the paper work from the time they placed the order until they received it. I agree this seems like a used not a new trailer directly from the factory.

The way the FLX is wired is very specific to the FLX model. Adding any other battery except an additional Lith. Battery will cause any number of issues. The fact that this battery is not a LifPo battery compounds the issue.

On the FLX all the wires run in the channel on the drivers side from the fuse box all the way to the front of the trailer. It is very easy to raise the tongue jack up and crawl under and see where they have spliced into those wires.

Winnebago ships the FLX with:

• One Lithionics 320Ah battery
• One Xantrex XC2000 inverter/charger
• One MPPT solar controller
• No second battery, no tongue battery, no mixed chemistry

The Lithionics is the only battery the system is designed around. .Adding an AGM/GSM battery:

• Breaks the Lithionics charging logic
• Confuses the MPPT controller
• Forces the Xantrex to see a blended voltage curve
• Prevents proper bulk/absorption charging
• Can cause the Lithionics BMS to refuse charge
• Can cause the MPPT to sit in float forever

The #10 wire, after thinking, I bet it is The MPPT controller’s battery negative lead. What triggered this was what you said about adding the nearly dead battery activate charging. The MPPT not seeing a battery until you connected a “nearly dead RV battery”. Think of it as the MPPT battery-sense wire floating open. When you connected a nearly dead battery:

• The MPPT saw a low voltage
• It entered bulk mode
• It began charging normally

When only the Lithionics was connected:

• The MPPT saw a high, stable voltage
• It stayed in float
• It refused to push current

The issue is the wrong battery is connected to the MPPT. Basically the FLX is designed with both wiring and logic to only have the Lithionics battery. Adding the second battery causes the logic to collapse.

One thing I have seen at dealers is that when they winterize the FLX they will remove the Lithionics battery and put a cheap battery on the tongue just to have power. When they reinstalled the Lithionics battery they did not remove the cheap battery. This make sense because someone had to change the MPPT setting to the new battery. If this was the case, then again this is not a new factory ordered trailer.

First, ask the dealer for all documents related to the trailer.

• Order date
• Ship Date from Factory
• Date they received it
• They may have transferred it from another dealer, they will have this paperwork as well

Demand they tell you who installed the battery. My guess is, it was done at the dealership since the wiring was done professionally. If they still refuse, then you have a couple other options.

Check the Lithionics batteries log:

• Manufacture date
• Activation date
• First power‑on
• First charge
• First discharge
• Cycle count

If the trailer was “new,” the activation date should be:

• within a few days of factory ship
• cycle count = 0 or 1
• first charge = factory test
• first discharge = factory test

Open the Lithionics app → Battery Info → “Manufacture & Activation.” If the activation date is

• months before delivery
• shows multiple cycles
• shows non‑factory charge patterns

Then more than likely the trailer was used.

Check the trailer build date. Every Winnebago trailer VIN encodes:

• Model year
• Production batch
• Factory sequence number

The key is the actual build date is not the model year — This is only stored in Winnebago’s internal production system. Contact Winnebego Towable customer service and provide:

• VIN
• Your name
• Ask for factory production date and shipping date

They should send:

• Production date (when it was built)
• Ship date (when it left the factory)
• Dealer destination

You can also check the Zantrex and MPPT logs for changes and dates.

As long as you have the second battery is connected the Lithioncs/Zantrex/MPPT logic will not work correctly. Beside removing the battery, you also need to remove all added wring, fuses, splices, or grounds to restore the FLX back to factory specs.

 

[alannsalter]

First, your dealer should have your order and the day it arrived from the factory. Ask to see all the paper work from the time they placed the order until they received it. I agree this seems like a used not a new trailer directly from the factory.

The way the FLX is wired is very specific to the FLX model. Adding any other battery except an additional Lith. Battery will cause any number of issues. The fact that this battery is not a LifPo battery compounds the issue.

On the FLX all the wires run in the channel on the drivers side from the fuse box all the way to the front of the trailer. It is very easy to raise the tongue jack up and crawl under and see where they have spliced into those wires.

Winnebago ships the FLX with:

• One Lithionics 320Ah battery
• One Xantrex XC2000 inverter/charger
• One MPPT solar controller
• No second battery, no tongue battery, no mixed chemistry

The Lithionics is the only battery the system is designed around. .Adding an AGM/GSM battery:

• Breaks the Lithionics charging logic
• Confuses the MPPT controller
• Forces the Xantrex to see a blended voltage curve
• Prevents proper bulk/absorption charging
• Can cause the Lithionics BMS to refuse charge
• Can cause the MPPT to sit in float forever

The #10 wire, after thinking, I bet it is The MPPT controller’s battery negative lead. What triggered this was what you said about adding the nearly dead battery activate charging. The MPPT not seeing a battery until you connected a “nearly dead RV battery”. Think of it as the MPPT battery-sense wire floating open. When you connected a nearly dead battery:

• The MPPT saw a low voltage
• It entered bulk mode
• It began charging normally

When only the Lithionics was connected:

• The MPPT saw a high, stable voltage
• It stayed in float
• It refused to push current

The issue is the wrong battery is connected to the MPPT. Basically the FLX is designed with both wiring and logic to only have the Lithionics battery. Adding the second battery causes the logic to collapse.

One thing I have seen at dealers is that when they winterize the FLX they will remove the Lithionics battery and put a cheap battery on the tongue just to have power. When they reinstalled the Lithionics battery they did not remove the cheap battery. This make sense because someone had to change the MPPT setting to the new battery. If this was the case, then again this is not a new factory ordered trailer.

First, ask the dealer for all documents related to the trailer.

• Order date
• Ship Date from Factory
• Date they received it
• They may have transferred it from another dealer, they will have this paperwork as well

Demand they tell you who installed the battery. My guess is, it was done at the dealership since the wiring was done professionally. If they still refuse, then you have a couple other options.

Check the Lithionics batteries log:

• Manufacture date
• Activation date
• First power‑on
• First charge
• First discharge
• Cycle count

If the trailer was “new,” the activation date should be:

• within a few days of factory ship
• cycle count = 0 or 1
• first charge = factory test
• first discharge = factory test

Open the Lithionics app → Battery Info → “Manufacture & Activation.” If the activation date is

• months before delivery
• shows multiple cycles
• shows non‑factory charge patterns

Then more than likely the trailer was used.

Check the trailer build date. Every Winnebago trailer VIN encodes:

• Model year
• Production batch
• Factory sequence number

The key is the actual build date is not the model year — This is only stored in Winnebago’s internal production system. Contact Winnebego Towable customer service and provide:

• VIN
• Your name
• Ask for factory production date and shipping date

They should send:

• Production date (when it was built)
• Ship date (when it left the factory)
• Dealer destination

You can also check the Zantrex and MPPT logs for changes and dates.

As long as you have the second battery is connected the Lithioncs/Zantrex/MPPT logic will not work correctly. Beside removing the battery, you also need to remove all added wring, fuses, splices, or grounds to restore the FLX back to factory specs.

I truly appreciate you thorough response. Thank you for taking so much time. I think I will start with reaching out to Winnebago's Towable customer service and get the production and shipment information. If I am going to confront the dealer, I would like to have as much information as I can so I don't get a second run around. I will also check the battery logs as well. Again, thank you so much and I will respond with the results when I have them.

 

[Morich]

Good to see a man with a plan. Also great to see how much more they know about the trailer!