Upgrade to Lithium battery 2018 Micro Minnie 2108D

[KGs2108DS]

to run my Winnebago Micro Minnie 2018 2108DS while boon docking, I'm considering upgrading from 2 deep cycle marine batteries (replacement value$275) to a Lithium battery - WEIZE 12V 100Ah 1280Wh Lithium Battery, Group 31 Deep Cycle LiFePO4 Battery at $219 at present. I'm having a hard time coming up with reasons why this would not be a good upgrade. I'm using a Honda 2200i to recharge via the onboard 6amp charger - an admittedly long process. I've considered buying a 20amp smart charger, which would shorten the charging process, still to be accomplished via the generator. thoughts on these upgrades?

[KGs2108DS]

I've come across another question...is the 6amp on-board trickle charger compatible with the above mentioned Lithium Ion battery?

[l1v3fr33ord1]

KGs2018DS-

Hmm... it seems as if you're not increasing the number of amp-hours, so why make the switch to lithium?

Although it doesn't bear on the lithium conversion topic, this post in this thread:

Micro Minnie Wiring Diagram

may interest you.

[dkoldman]

OP does not say, but if you assume the 2 existing Marine batteries are no more than 100ah each, then he will be increasing usable ah capacity.

FLA 200ah = 100ah usable
Lithium 200ah = 185 - 200 usable depending on battery specs

I am upgrading my battery two vMax tanks 125 ah each to a new 300ah Lithium battery I just bought. I am only doing because my AGMs are about 3 1/2 years old and when they die, I do not want to buy new AGMs to replace so I started early with the conversion as to not in a pinch.

Although I have installed the Lithiums I have had about a week sitting and they are still showing 100% SOC and 13.9vdc.

[Thindirtline]

Go with at least a 150ah LiFePo battery. Install the battery inside. You can’t charge them if it is below freezing. Make sure you set up a charge cycle for lithium. The charging parameters are different than lead acid. Mount two 200w solar panels on the roof if you don’t have them already. This is what I did on my 2022 2108 TB. Seems to be the perfect system size for boondocking.
I mounted the battery in my storage area right behind the external mounting area. I drilled a hole and used the existing battery wiring. I can give you more details if needed.

[KGs2108DS]

thanks to each of you for your thoughts/experience!! I purchased a SOK 100Ah 12V LiFePO4 Lithium Ion battery for my MicroMinnie. I think, together with the Honda 2200i and a LiTime 12V 20A Lithium Battery Charger 14.6V LiFePO4 Battery Charger AC-DC Smart Charger with Anderson Connector LED Indicator Special for Lithium LiFePO4, I'll be able to run the trailer adequately (minus A/C - no problem boon docking in the mountains), and recharge the battery much more quickly!

Have considered mounting the battery in the L side front pass-through compartment, though not entirely certain how warm that might be, though the MM furnace warms the floor and trailer bottom is fully enclosed - so likely warm enough not to freeze. And an inside compartment would afford security advantage.

also the I learned that the stock WFCO Ultra III Distribution Center, WF-8900 series is fully automatic and compatible with Li Ion battery (This microprocessor-driven system recognizes lithium-ion and lead acid battery chemistries and automatically adjusts the charging profile to match the battery type).

So, hopefully a great upgrade in power and definitely less weight than the present 2 deep cycle marine lead acid batteries!!

Thanks again for all your help and advice!!

[tinglett]

I made a battery box for mine (2 Battleborn 100AH batteries) and placed in the garage near the front:





This setup works great. The batteries are a complete game changer, especially after I added three 100W solar panels on the roof. If I'm setup in the sun it won't run out of juice even when I use an inverter to charge my laptop, etc. But it is boondocking, so no A/C, coffee makers, etc .

If I were to setup again, I think I'd place the batteries in the forward middle of the passthrough. I would only block the through space of part of the passthrough. Then I'd have more room for wrangling the wires. But it works fine where it is.

My stock WFCO 8955 was not suitable for lithium. I replaced it with a PD4655LIV which is hard-wired for lithium only.

[Fred L]

Curious on what is involved with the wiring to move a lithium battery inside the storage area? Ie, how do you get the connections that are to the existing battery inside? Presume an extension of some sort, or running heavy gauge wires from the new lithium battery out to the existing area and somehow connecting them there?

[Marine359]

Originally Posted by Fred L

Curious on what is involved with the wiring to move a lithium battery inside the storage area? Ie, how do you get the connections that are to the existing battery inside? Presume an extension of some sort, or running heavy gauge wires from the new lithium battery out to the existing area and somehow connecting them there?

Easiest is to pull the wires from the battery box and stuff them up through the loom that descends from the disconnect switch and goes through the floor.

[Fred L]

Thanks Jim. From recollection of my last trailer, that should be all wires, except the tongue jack?

[Marine359]

Originally Posted by Fred L

Thanks Jim. From recollection of my last trailer, that should be all wires, except the tongue jack?

There are circuits that bypass the disconnect switch other than tongue jack, including gas sensors, slide, and radio pre-sets. You don’t have to change those because they are wired to the fused junction box on the trailer tongue. You just basically need to re-route the dc bus cable. I found it convenient while I was at this to install bus bars, and an extra disconnect switch between battery and positive bus bar. This enables you to kill all power without needing to remove the battery terminals. You can take a look at my mods album for wiring ideas. Following is a photo/diagram for the junction box. Note the 6 gauge red wire. This is the one to push up in through the loom. In mine it was long enough to reach without needing a splice. Also note the white 6 gauge ground wire. I chose to run a second chassis ground from my negative bus bar to ensure everything is proper.y grounded. It’s been a while and things may have changed in later model years.

[KGs2108DS]

since I last posted I done several things with my electrical system, but the Victron Smart Shunt is giving me some odd numbers. I installed SOK lithium ion 100Ah battery, and a 20 amp Lithium ion charger. I realized that the smart shunt settings need to be changed to a lithium ion battery and have done that. the charger is working, but here are today's numbers

time 0 69min later 10 min later - green light on charger
Satate of charge. 86% 85% 100%
Volts 13.2 13.7V 13.87V
current amps. -3.5a -0.52a. -0.52a. turned off load at time 0
power -47W -7W -7 W
current used Ah. -14.3 -14.6Ah -0.1Ah
time remaining. 14h 19m 6D 7D

this seems like an unusual charge curve in terms of state of charge, with what looks like a very flat/low curve, and then a sudden increase to 100%. And for the first 69 minutes per the state of charge, it does NOT appear the battery is charging at all! this makes it difficult to predict how soon the battery might be charged. Does anyone have any ideas or suggestions? much appreciated, and thanks!
Kim

[KGs2108DS]

very sorry, the data lines up vertically until I het post

[Marine359]

Time to charge from zero SOC = amphrs of battery divided by charge current. LiFePo4 charge curve is almost flat, all the way up until it reaches balance current. This is in the last 5% and varies from battery to battery depending on the bms. So, if you have a 20 amp charger, you should go from zero to 100% in 5 hours assuming your charger is outputting 14.6v.

[KGs2108DS]

thanks Marine359 and for your service to our country! so, it sounds like the SOC is not a great number to use to predict when the charging process is complete. Are any of the other measures on the Victron useful for that? it sounds like you are saying to use the formula to calculate time to 100%SOC? So, 100Ah/20mp = 5hr. in my scenario, 14Ah (used out of 100) divided by 20amp charger = 0.7 hr? But it took a bit longer at 79min.
thanks!

[Marine359]

Oorah!
Your battery may have been “fully charged” in 14 minutes. However, like I stated, if you leave the charger connected, the bms is likely to go into “balance”, some call this absorption phase. This is when cells inside the battery get top balanced. You’ll notice it when charge voltage starts to drop. Which a good thing, but doesn’t need to happen every charge cycle. The Victron shunt is very accurate if you first calibrate it. I think the instructions are to first fully discharge and then charge until the shunt reads 100% SOC. Of course, I don’t know what brand charger you’re using, but they aren’t as accurate as the Victron. When in bulk phase, your Victron should be showing 14.6v input. If it doesn’t, it’s probably not set up correctly. Or charger may not be outputting 20 amps. 14.6*20= 292 watts. A 100ah LFP has 12.8*100= 1,280 wh. So, 5 hours to fully charge. Check your Victron to see how many watts are coming in.

[KGs2108DS]

thank you again Marine359: My charger is Li Time 14.6V 20A LiFeP04. I've not left the charger on once the green fully charged light comes on. I will be boon-docking in the mountains for the next month or so, and the plan is to use my Honda 2200i generator plugged into the trailer shore line which will power the 6amp on-board trickle charger. Additionally I'll plug in the Li Time 20A into a 110VAC outlet on the generator. The Micro Minnie is small with only 2 people, and I think with this set up, I'll be able to generally get the battery back up to 100% in a couple of hours. I've read pretty extensively, and as best I can tell the stock Winnebago WF-8935-AD Power Center is compatible with this approach. The previous approach using 2 lead-acid batteries with total of 135Ahr typically dipped into the high 70s% range by evening. But, the generator plugged into the shore line never brought the battery up to 100%; typically only up to 85ish in a several hour run. so, gradually over several days the SOC would diminish, and not be fully replenished. I'm hoping for a better, quicker recharge with the new approach, and would be interested in your thoughts on likelihood of this scenario. thanks!

[Marine359]

Originally Posted by KGs2108DS

stock Winnebago WF-8935-AD Power Center is compatible with this approach. The previous approach using 2 lead-acid batteries with total of 135Ahr typically dipped into the high 70s% range by evening. But, the generator plugged into the shore line never brought the battery up to 100%; typically only up to 85ish in a several hour run. so, gradually over several days the SOC would diminish, and not be fully replenished. I'm hoping for a better, quicker recharge with the new approach, and would be interested in your thoughts on likelihood of this scenario. thanks!

Your LiTime charger is a good one. And, the WF is auto-detect, and I think will automatically switch to LiFePo4 charge profile @30 amps charge current. So you’re all set with those two th8ngs. However, and this is huge, you did not indicate what kind of fridge you have. If you have a compressor fridge 100ah is kinda wimpy. The Dometic 4100 series dc fridge in my MM was pretty frugal, using 700-850wh per day. I’ve been reading that the GE dc fridge that WBGO is now using is a big time power hog. You definitely will want to take a power audit before leaving on a trip. 100ah may get you through the night but that’s about it. You also did not indicate if you were using your WF and LiTime to charge simultaneously. That’s probably not a good idea. It’s ok to use multiple simultaneous charging sources (like solar and dc charger), but auto-detect on WF may fail when it senses another dc charge source on the dc bus. IDK for sure, but I wouldn’t do it. That being said, I routinely used my inverter/charger @ 60 amps to charge while my solar was connected, and it worked fine. But I did not have auto-detect. I just don’t know about WF. Maybe read manual. And maybe get a second LFP depending on fridge type.

[KGs2108DS]

thanks! I think the fridge draws very little juice. I've run it for 3 days (on the old batteries), when not using any other power, and it's fine SOC ~70%. it is a Cometic DM2652 triple power 120V 60Hz - 2.7amp; 12V. So, I don't think it is a power hog. I always marvel that the fridge running on propane stays very cold, colder that when on 110VAC.

[KGs2108DS]

New post and update to the thread above. My Lithium Ion battery does not seem to be charging correctly during towing. Yesterday 8hr travel, only refrigerator running on propane ~1.25amps. Upon arrival at destination 65% SOC, 13.11V, -16W, -35.9Ah, 1d12hr remaining. This morning after standing overnight w/refrig 57%SOC, 13.08V, -1.06A, -14W, -44.4Ah, 1d13hr. Connected 20amp Li charger for 1 hr: 56%SOC, 13.08V, 6.22a, -14W, -44.4Ah. The charger is new, and red light indicates charging. It seems to me running a 29amp charger for 1 hr should add 20Ahr to the battery, moving the ending -44.4Ah to -24.4Ah - is this wrong? I do note the charging wire from charger to battery is ~30” long of small gauge wire. At I then d/c the 20amp charger and plugged the shoreline in for 30min getting: 59%SOC, 13.5V, 6.34A, 86W, -42.3Ah. This is running the on-board 6amp battery charger in the WFCO Ultra III Distribution Center WF-8955PEC. I then plugged in solar “brief case” given to me by a friend, and after 2.5hr: 62%SOC, 13.43V, 2.32A, 31W, -39.3Ah. The user manual for WFCO has 4 trouble-shooting notes: a) open inline fuse in battery wire (don’t think my trailer has this), b) open wire between the converter and RV battery (seem like there’d be NO charging whatsoever if this was the case), c) loose ground (hum… possible, but I’m not sure how to check the various grounds), d) improper torques (I’m not sure what this is??). I’m at the beginning of 6 weeks of boondocking, and am a bit worried about this issue. Oddly, the LED display on the MicroMinnie indicator panel (tanks and elect) show the battery to be fully charged 4 LEDs lit. Any help or thoughts would be much appreciated!