Lithium Battery BMS Behavior

taranis17 said:
I'm very interested in your 'boondocking' test results, especially if you decide to use solar at all. Interesting about the furnace being a power hog - how many watts does that draw? I figured, it being on propane, the only power needs would be the blower/fan.

I shall be living vicariously through you this weekend!
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You live a boring life if you live through me vicariously.

I Left the house Friday with the camper in tow and the lithium bank sitting at around 70% SOC. Two hours of tow vehicle charging and I rolled into the campsite at 8:00 PM at 99%. That's the last time I thought about the battery until I started taking notes.

Friday Night

Loaded the CFF35 12V compressor cooler with a a few warm ones, about to be cold and some groceries for Saturday. Left the galley light on for a couple of hours. Charged the phone and watch. Vent fan running. Normal stuff — nothing heroic in termf of saving power. Pretty much just as I would use it with shore power, herpahs even a little more 'wasteful' --- thninking worst case sceneario

(is it just me? Every time I say worst case, I think sausage and cheese)

By midnight: 91% SOC, fan still running at about half speed overnight. It was the first time in a long time I did not use the AC at all -- the temperatures were perfect!!!!

Saturday Morning — 81% SOC

Fan ran all night with one marker light burning. Lost 10% overnight. This is the point where the ol' a lead-acid battery is going to make less sense -- that battery woudl be getting pretty close to 50% by now, which is, as we know where damage starts to happen inside the cells. On lithium, I didn't give it a second thought.

Saturday Afternoon — 67% SOC

At 67%, I'd be watching the gauge nervously and shutting things off. Instead, I left everything running.

Saturday Evening, 6:30 PM — 57% SOC.

Voltage holding at 13.1V. The vent fan and compressor cooler are the main draws, and adding the refrigerator definitely accelerated things. I'd routinely see aroud 4.5-5 amps being used. Per the BMS: 57 Ah remaining, approximately 9 hours of runtime left at current load. That puts exhaustion around 3:30 AM which will become interesting in a moment.


Saturday Night: 10 PM 49% remaining. Running fan on high, refrigerator bringing a few sodas down to temperature, 1 light on -- charging a phone, and a watch. Pulling 10 amps from the battery. I havn't seen this question in the forum in a while, but the 'small' is not adequate if you are a super power user. At that rate, BMS is saying 5 hours... but the fridge will soon stop chugging as it will have gotten down to its target temperature, and the light will go out, and the phone wil be satisifed. I'm thinking I"ll make morning.

Sunday Morning: 4:19AM The observation taken at 6:30 where it project 3:30 depleation? It was off just a little...4:19 my fan suddenly stopped. The BMS cried mercy and powered off the battery. Pretty good considering the project was 3:30.


Next trip, I'm sure I'll need AC -- but I cna power off the charger seprately. I plan on the same experiment but doing two things different.

1] Power saving mode -- being sure to turn non-essentials off when not in use
2] Plug in the solar panel. I've got folding suitcase panel -- I think it is 150 watt...We'll see how it help me...

So --- there you go!
 
taranis17 said:
Whatdaya think I’m buying a camper for? :p

Great report bud. Hope it was a fun weekend and your back is all better!
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It was an OK weekend --- I bought a rope with me that had way too many knots in it, metaphirically. I need to find a way to untie those more often. But, I feel like I've had a day off which is something I havn't felt in a while.

Back is doing much much much better thanks for asking, though it is a little tender at times. This new and ongoing problem is making me reconsider what I do --- my 30 year old brain is realizing the body attached is twice its age.

I Kind of expected that would happen. I think I'm going to defocus repair and shift more towards inspection. I get a request here and there for those, and I think if I market it I can find a market. I found a few holes in my business plan - which is expected, no battle plan ever survives contact with the enmy.

I had a few more thoughts about the battery, and ran into a few technical issues -- I'll be figuring those out and keep this updated.
 
taranis17 said:
I'm very interested in your 'boondocking' test results, especially if you decide to use solar at all. Interesting about the furnace being a power hog - how many watts does that draw? I figured, it being on propane, the only power needs would be the blower/fan.

I shall be living vicariously through you this weekend!
Click to expand...

I didn't have a soid amp reading -- I'm seeing comments that this family of furnaces are very low -- 3.1 amps. I may have to test that ...

Honestly, I never leave mine 'on' except when I'm awake, and I usually run it for a few minutes just to warm the cabin, then turn it off, until I get cold again. I like to sleep in cold rooms, so its never a real problem.


TheSongDogHouse said:
Well, @Sweeney you can write it off as business expense, right? Training and evaualtion? ;)
One thing I have noticed is its not easy to find auto shops, stereo installers or even RV repair places that can trouble shoot trailer-hookup, ctek, lithium and solar issues, from the TV start battery to the RV house battery.

Some just say "our insurance wont let us do anything solar" etc.
What it really comes down to is the ability to troubleshoot at the basic wiring level but understanding how new things added in the system, interface.

So you have that going for you at a high level.
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Well, technically my van has signs on it, and I do take 'calls' from people in the park --- so it COULD be argued as a business expense in any condition :) And yes --- I do >if< my intention is to drum up business. If my intention is R&R, then I do not claim it.

I think the insurance thing is a red herring -- a lot of guys simply don't understand and it saves face to blame the insurance...Or they simply aren't 100% sure they can and can't do under the insurance, the policy commonly used is issued by 1 company and it is rather ambiguous on some things. Particularly on 'edge' cases like solar where tehre is some expertise and extra training avaialble.

Honeslty though, if they aren't confident -- I do not want them touching it anyway!
 
@Sweeney Glad that you seem to be getting your Lithium adventure all sorted. I also took the Lithium plunge last summer and installed the same LiTime heated group 24, so it's great to hear your experiences. I've been meaning to do a post on my install...maybe I'll get around to it.

A few things, I've found. First to deal with parasitic draws, middle term storage (days or weeks vs months), and even things like the breakaway brake switch. I added a dedicated 60 AMP fuse breaker at the battery (see picture). Works as a disconnect and fully isolates battery from all charging and loads, great piece of mind when checking connections and fidling around that nothing is connected (also doesn't require plugging in the charger to turn the battery back on like turnoff the battery using the battery phone app). The camp-inn disconnect still turns off loads but allows the battery to be charged and keeps the brake away circuit powered. Just need to reset the breaker before towing to power up the breakaway circuit.

I also had started off with similar charging issues as you. What I noticed my is my shore charger (high end Victron unit) doesn't have a separate voltage test line to measure voltage at the battery during charging (like my solar charger has). Instead the AC shore charger measures voltage output, and that voltage did not agree with the voltage shown on the battery BMS. Basically at high charge currents I was getting a large resistive voltage drop due to small gauge wiring and long cable run. Since my charger was installed in the factory location under the camper above the axle (2012 model) I couldn't do much about length so I pulled fresh oversized charge wires to minimize voltage drop. Interestingly even the stock charger cabling seems undersized for length for such a high amp shore charger. However, the larger cabling at least coupled with setting the charge voltages to the upper end of the LiTime recommended settings did the trick. There is still a voltage off set during the initial high current constant voltage charge but the voltages readings (shore charger and battery BMS) merge as the charge current tapers off in the constant voltage stage and the charge current goes towards smaller numbers (V=I × R so smaller voltage drop at smaller current). This allows the charger to fully the battery before going into storage mode.

Look forward to following your continued adventures and maybe I'll get around to that Lithium install post I been meaning to draft...
 

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TheSongDogHouse said:
@RichE That looks very clean!
Is that hole on left side of photo of battery compartment made as a pass thru to where? Cabin?

Did you jigsaw cut that opening in the forward side of the battery compartment?

I've been noodling on how that method might be one way to vent heat, for a lion battery stored in a high temp storage lot, per the caution earlier...
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The cutout does go into the cabin. Footwell area under the cabinets. It was leftover where I removed a non-functional CO detector ( I do have battery powder CO installed and am working on wiring up a dual CO/propane one)

I actually cover it up, although I did run a conduit line through there and into the rights side galley cabinet where my DC/DC and solar charger controller is located.

I hadn't considered using it for cooling although now I'm considering whether a grate might be a good alternative to the blanking board I installed to allow some passive (or active as you describe) cooling of the battery area.
 
TheSongDogHouse said:
Thanks! That could also be a handy way to discharge this stuff if needed into bat-tree compartment. Thats the other rnd of the heat range: camping below zero overnight and sun starts charging the bat-tree, which is bad juju.

I understand the heated lion batteries BMS is supposed to use battery juice to preheat the battery to avoid that but...just in case...a himged and latched door like the cabinet cubbies...lots easier than popping the galley hatch, opening galley bin, digging thru and removing stuff, unscrewing the battery door, hmm.
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The battery I have can warm itself in two ways...if you have 10 amps coming in, it can heat tha battery purely off the incoming voltage --- or, it can use the battery cells to self-warm. I'm not convinced I"ll ever use the feature -- my garage is semi-heated, and never goes below 35 or 40 degrees, and for the most part, if I'm camping its during the shoulder/summer season...I don't do much if any sub-freezing temperatures, though it has happpened a few times.

I probably could have solved the problem using a battery cutoff switch that detected low voltage then saved the battery by disconnecting it -- but the price point of LIFEPO4 and Lead Acid deep cycles were very close to the same...the lifepo4 was actuallly just a little less expensive...shockingly.

Pretty please so far, except for the aforementiond difficulty getting the shunt to report correctly...but thats not a big deal with a BMS that is smarter and connected.
 
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