Winter, Li Po batteries, Lessons

[rfrance0718]

Last summer I replaced the 50 ah lead acid battery in my camper with 2 50 ah Lithium Iron Phosphates. I kept the 100w solar panel that I had, and replaced my charge controller and ac/dc charger with ones designed for the new batteries. This was all done because I gave up on my 3 way fridge and replaced it with a 54qt cooler that runs on 12v and ac, but not propane. The cooler draws about 40w when the compressor is running but almost nothing when it's not. (the 3 way fridge wasn't reliable in the propane mode, and drew power all of the time it was running on 12v)) During the summer and fall all went well, but I had some new lessons to learn when I started going on ski trips where the temps dropped down as low as 0f at night.

At night I keep the camper interior at about 66f, and use a small 12v fan to try to distribute the warmth. With the colder cabin temps, the cooler's compressor doesn't run much, and my other voltage draws include LED lights and the little fan, so not much. With that kind of consumption my batteries should last 24 hours easily, as they had in the summer. The problem is that Li Po batteries are more sensitive to the cold than lead acid batteries and I underestimated the effect.

On my first ski trip the temps dropped down to 0f at night. I did notice that my batteries were down some, maybe 12.6, when I went to bed, but I didn't know to be concerned. When I got up in the morning my controller displayed an error message, and I found that my voltage had dropped to 10.8. Not good, but within the tolerances for Li Pos, barely. At that point, I shut the fridge down and I didn't need the lights. By the time I got to the slopes my solar panel kicked in and I was back up to 12.9 or so by 4:00 PM. This was only a one nighter, so I headed home.

Hmm. I was heading up to Northern Michigan the next week, and expecting similar weather, so I made a few changes, and a few more mistakes. I started with some research that said that the batteries would be effected at 32f or below. My batteries are in one of the lockers below my seat benches, and do really get cold with the seat closed. I decided that I would try keeping the seat top open and monitoring the compartment's temperature. I also brought my 800 w inverter along as well as a clamp lamp with a 40w ac light bulb. I had done some research and learned that I could hook up the inverter and run an extension around to my shore power inlet, giving me ac power in the cabin. What I didn't learn was that the cigarette lighter connection can only be used for about 120 watts. Along the way I stopped at a rest stop and found that my voltage was down to about 12v and that the battery compartment was down below 20f. At a rest stop I plugged in the inverter and used the 40w light bulb to warm up the batteries. After a short while I turned on the ac/dc charger and the batteries responded quickly. All good until I blew the fuse to the cig plug, and found that it had overheated. I figured that the plug connection was the issue and decided that I wouldn't go there again.

When I got to my destination, I put a gallon jug of water outside which froze solid quickly as the temps dropped down to the single digits. This way I could use the frozen jug in the cooler and didn't need to run the compressor at all. Since I was only running the lights and my little fan I had enough power, even though the voltage still dropped down to 11.8 over night. I should mention, at this point, that my propane catalytic heater was working perfectly and keeping me absolutely toasty. With the temps in the cabin at about 66f, the batteries were above 32, barely, but I figured that this was good enough. This proved to be very wrong.

That night I did some more research on Li Po battery temps and on using an inverter. As it turns out, the batteries need to be above 50f to reach their full abilities. I also learned that my inverter needed to be hooked directly to the car battery to handle wattage over 120. (not sure why they would even include the cig lighter adapter with an 800w inverter, but lesson learned) I looked into whether the using the inverter would be hard on my alternator as well.

From what I read, my alternator is safe as long as I'm drawing 600w or less, which I am. Also read that the alternator on my f150 is very beefy. So I went ahead and hooked up the inverter to the battery, ran it around to my shore power inlet, and used my ac/dc charger to top off the batteries. When I got home I attached the inverter to a board, to give it a stable base, and insulate it from the frame. With that done, I'm hoping I won't need it again. Otherwise I could hard wire the inverter, or add a dc to dc charger.
I also read that the Li Po batteries need to be above 50f to reach their potential, and that info lined up with my new experiences.

With the batteries topped off, and the cooler using the ice jugs, I didn't need another charge, but my voltage continued to drop even though I was only running my led lighting and my small fan.

Back home now I was able to run a test. I added some Velcro to keep my battery compartment lid open and added a second small fan, mounted to circulate can air into the batteries. The temps only dropped into the high twenties, but the results were very positive. With the cabin at 66F, the battery compartment stayed at 61f. My batteries were at 12.9 at 8PM, and had only dropped to 12.7 at 8:00 AM. With colder outside temps, I'm thinking that I can still keep that difference less than 15 degrees, and the batteries will stay over 50f. I'll need a nice cold night to fully test.

I've attached some photos showing my battery compartment with the new fan, and the inverter setup. Cold weather camping is an adventure, and there is a bit less info available about its challenges than its warm weather counterpart. I also just watched a video about using Li Po batteries on sailboats. Here is the link, very interesting. He uses batteries from the same company as I have.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment..

[rfrance0718]

https://www.youtube.com/watch?v=avxqtbXUR30

[rfrance0718]

Sorry about my typos and other errors. I'm really struggling to get the site to save my latest changes and corrections. I've solved that on long posts, in the past, by creating a word doc to paste in. I didn't realize how involved this would be!

[noelH]

Have been flying UASs powered by lithium polymer and lithium ion batteries for awhile.  Use to be maybe too "OCD" when it came to battery maintenance and monitoring.  Now I just on scheduled basis check the health, storage level of the few too many batteries sitting around.  New tech.  Modern FCs monitor in flight cell voltages, capacity (mAH).  Still trashed a price 6s battery by not realizing how significant voltage sag was when close to lower end of capacity. Time to breakout the discharger and properly dispose of it. 

IR(internal resistance) increases with lower temperatures.  Putting a load onto a too cold battery depending on the lowest individual cell voltage can damage that cell.  Sort of a double kick in the butt.  Lower temps, lower resting voltage and higher IR. Stress with a load. Damage a cell.  "Weakest" cell in a battery is like the weakest link in your chain rode.

Ideally if you get data on the voltage of each cell in the battery and the IR you can estimate if or if not to put a load on the battery. If at the lower end of resting voltage.  Best to not use the battery and let it charge.  The heating up of the battery during charging might allow you to use the battery if absolutely needed with just a slight elevation of voltage.

Monitoring IR of each cell in your battery is a simple way of determining relative health of the battery.  Just make sure the ambient air temp is close to the same each time you monitor the IR and the battery is fully charged.  If you notice one cell is moderately off it is time to invest in a new battery.  Some "smart" charging systems are not that "smart".  You can potentially over charge the "healthy" cells resulting in a catastrophic  event.  If your charger is "smart" it will cut charging when the healthy cells reach "full". The weak cell will just be that.  But, if your use results in discharge to the low of normal low. That cell might be excessively discharged degrading it further until eventually charging it becomes dangerous.

[noelH]

Were you, are you heading up to Mt. Bohemia in the UP?

Lake Effect snow forecasted later this week.  IIRC, Saturday.
Last Wednesday we had a decent snowfall of powder.  Usually the local area is "over" groomed. But this time they left ~10 meter wide swaths along the trees and lift.  Got to the area at opening. 3 of us for the first hour. Gotta love snow-covered, slippery roads and -12C temps and poor visibility from more snow.  So rare in the midwest to ride untracked powder multiple times.  Then the crowds showed up.

Today, hard cord.  Hit +5C yesterday. Dropped down to -6C last night. Blue sky. No whining about vis.

[rfrance0718]

Mt. Bohemia is 13 hours away from here, in good weather. Hard for me to rationalize that long of a trip. I also might be a bit intimidated by all of their blacks, double blacks, and triple blacks! Out West, I'll pick my way down a black, if the bumps aren't too big. Are the Mt. Bohemia blacks, real blacks? At Seven Springs they have what they call blacks, but they're not really challenging at all.

I wouldn't have any idea how to test individual cells?

Cheers

[Seorah]

Cold weather and lithium batteries, definitely a combo that needs some extra planning. Glad you figured out the inverter/cig lighter issue, that's a rookie mistake I've almost made myself. The extra fan in the battery compartment is a smart move.

[noelH]

Mt. Bohemia is 13 hours away from here, in good weather. Hard for me to rationalize that long of a trip. I also might be a bit intimidated by all of their blacks, double blacks, and triple blacks! Out West, I'll pick my way down a black, if the bumps aren't too big. Are the Mt. Bohemia blacks, real blacks? At Seven Springs they have what they call blacks, but they're not really challenging at all.

I wouldn't have any idea how to test individual cells?


Cheers

Usually quality stand alone chargers have diagnostic functions.  Years ago I purchased a tester from a Brit specifically designed to test only IR up to 6 cell (aka 6s) batteries. Guessing someone out there still makes a similar tester.  Especially now with more home battery systems for their alt electric sources. 

Haven't ever ski or snowboarded Mt. Bohemia.  It's a slow ~200 miles road trip from home. Lutsen is ~1 hr closer to hit a larger(ie, almost 1000ft vert) regional ski area.  Be a good trip.  Housing at the hill use to be yurts for hostel like accommodations. Today you have cabins. No Saturday daily lift tickets available.   Friend who use to be a PSIA instructor at Steamboat who was also listed by SKI as one of Americas Top 100 PSIA instructors has skied Mt. Bohemia. Black is true black.  Steep and deep and tight or steep,deep,glades and/or major drops. Advance or expert only mountain. Mt. Bohemia is a no groom mountain. Pure natural. Benefit of being high up on the Keweenaw in the middle of L. Superior.

[Norm L.]

I'm speechless. My only comment is that I am totally impressed with that amazing camperette.
It is about 300 steps ahead of my homemade 1970 VW Type 2 camper in 1972.

[rfrance0718]

Camperette! I love it. In 1972 I had a friend who fitted out a micro bus by faithfully copying the Vanagon interior, without the pop top. It really influenced me. Just took 50 years to do my thing.

[Norm L.]

I did the same thing, although far from faithfully. The fold down seat kit and one of the louvered screened windows. Then behind the driver's seat a cabinet with sink and a fold down table. Storage shelves went on the inside of the sliding door. It's feint towards the Vanagon was the sliding sunroof.
A round trip to the west coast to catch the National Motorcycle finals and a road Small Great Loop New Orleans to Kitty Hawk beach, Maine, Ohio, and back to New Orleans.  Never any repairs necessary except putting a new wire on the sliding roof mechanism.

You cannot view this attachment.

This is one of our favorite campgrounds. About a 3-hour drive to COE Lock 7 primitive but pretty site on the Tombigbee River. The sink Leslie is using holds 5 gallons of water and a hand pump. It fits on top of the cabinet behind the driver's seat.
Something like what might be found on some small trailer sailers.

[Charles Brennan]

Norm, That pic with the Reliance Porta-Sink, took me right back to the '70's. We originally got it from a short-lived off-shoot of J.C. Penney's, called: The Treasury. It went camping with us and when we first got Urchin, it fit neatly behind the main cabin bulkhead, next to a side berth.  Quite a necessary piece of gear, back when the kids were little.

You cannot view this attachment.

On cross-country trips, we used Urchin as a camper and the kids ate in the cabin, instead of inside restaurants.  Their table manners were still evolving and we figured it was easier to hose off the inside of the cabin, than to provide raincoats for all the patrons surrounding our table.  That sink was highly useful for the apres dinner child washing.

All the white plastic parts (drain hose, fill vent cap, pump/faucet, water fill cap) eventually got brittle and broke, rendering it useless.
And OF COURSE!!  Any time I like something, they quit making it, so we learned to do without. But there are still times when I would like to have another one; pretty sure it would fit right in the SCAMP for extended weekends.

Thanks for the memory,
Charles Brennan

[Norm L.]

Our sink was rectangular and held up very well. Even passed on to daughters camping. Until she got more sophisticated.

[rfrance0718]

I had dreams about such an excursion. Lot's of reasons that it didn't happen. My first wife wouldn't camp, couldn't get much time off of work, and didn't have much money.

Your campground and setup look awesome. Looks like it was 72 and sunny for the whole trip!


 Finding a decent place to camp is harder than finding a marina or nice anchorage. Seems like it should be easier in the winter, but it's actually more difficult.

I had a friend whose parents owned a short bed Winnebago. In 1974 we did a two week trip from Ohio to Yellowstone. We had friends who worked at the Tetons and at Yellowstone. I could have just kept going.

[Brian S]

rfrance, do you ever have to worry about the propane tank freezing up on you in those cold temps? I'm guessing your heater uses less gas flow than, say, my grill uses, and so the tank doesn't cool off too much due to the expansion of the gas?

As an aside, does anyone remember the Ideal Gas Law from chemistry class? PV=nRT I have no idea why that equation has stuck in my head so strongly all these years after high school...