Lithium Battery BMS Behavior

[SethB]

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.

I think there are far fewer auto electric shops than we once had. I feel lucky that the major u-haul is not so far from my house, and their trailer/hitch/electrics shop is not bad, because our local auto electric shop went out of business maybe 10 years ago.

If you are anywhere near fishing or recreational boat fleets, there is still a lot of custom marine electric/electronics work being done, including cool parts and accessories, solar, lithium batts, etc…

 

[TheSongDogHouse]

I think there are far fewer auto electric shops than we once had. I feel lucky that the major u-haul is not so far from my house, and their trailer/hitch/electrics shop is not bad, because our local auto electric shop went out of business maybe 10 years ago.

If you are anywhere near fishing or recreational boat fleets, there is still a lot of custom marine electric/electronics work being done, including cool parts and accessories, solar, lithium batts, etc…

Got same tip from a senior victron support guy who happened to be sales manager for Precision: go to a marine service place at harbor that does solar on boats.

With the construction and hardware on these little "glamping land yachts" being aviation-marine grade or inspired, it makes sense that way too.

 

[David Rossiter]

I have a lot of experience with the LiPo battery, victron charger (IP65 15A), victron smart shunt. It’s a long story, but i’ve had the setup for few years now. I currently have the CI recommended LiPo battery. It has a basic BMS in it. Here is what i know. First and foremost- configuring the smart shunt properly is a major PIA. If not impossible. If you dive into how it works, the parameters, etc you’ll quickly realize that its an estimate of battery SOC. AGM SOC measurement is based on voltage. Voltage decreases as SOC declines. So you can get a reasonable approximation of SOC. Since it kills the AGM battery if you go below 50%, precision doesnt matter so much. You gotta keep it charged up. Since LiPo voltage is constant until it is almost fully discharged, you cannot rely on voltage. Hence the complicated smart shunt parameters. BTW, as noted sbove, store your LiPo at 40-60%. They don’t like to sit fully charged. Also don’t go below 20%. Many BMS will shut down at 20% to prevent damage.

But on the smart shunt and SOC- if any one of your parameters you configure are even slightly off, you won’t get accurate SOC readings. I’ve been fiddling with the parameters for a few years now, done more research than a Nobel prize winner. I’ve only been able to get it sorta sometimes maybe accurate. It’s all a bit of a mystery. Here is what I’ve found. I use the Victron app for both the ip65 charger and the smart shunt. You can through a combination or these devices figure pretty closely if you’re 100% charged. Study the charging LiPo charging profile for the victron charger. Both devices will give you the total amps during a charging session. The charger data is better for this, it will show you total amps, bulk, maintenance etc. by knowing how many amps the battery took during the charge and comparing it to what your smart shunt said your SOC was before charging, you can get a sense of whether your parameters the smart shunt are good. Note that in my experience the smart shunt will often show 100% SOC before you actually get there. I know this because of the total amps charged per the charger report, when the smart shunt shows 100% before charging. It can be wildly off. You can force reset the SOC to 100% after fully charging. But that doesn’t do you much good if your shunt parameters are off. Your SOc reading will be off as you discharge. I’ve found that with 110Ah (?) battery, it doesn’t matter so much what my SOC is. I have more than enough capacity to run everything I have for days (5-6 days)

Also I have seen from research that some LiPo batteries with extra smart BMSs will end up fighting with your charger. That sounds like that maybe your problem. Both systems (the charger and the BMS) are trying to do similar or conflicting tasks. Since it’s harder to get a dumber LiPo charger, you really need a more basic BMS (which means battery).

 

[Sweeney]

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!

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]

You live a boring life if you live through me vicariously.

Whatdaya think I’m buying a camper for?

Great report bud. Hope it was a fun weekend and your back is all better!

 

[Sweeney]

Whatdaya think I’m buying a camper for?

Great report bud. Hope it was a fun weekend and your back is all better!

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.

 

[Sweeney]

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!

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.

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.

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!