Battle Born Performance & Charging

[uncle_bob]

Hi

Assuming that nothing is going on in the trailer (yes that's another assumption) very little power came out of the batteries between "fully charged" at 14.28V and the shot 24 hours later at 13.28V. Whatever did happen was below the 712's measurement threshold. That could make it up around 2.4AH, it could be a whole lot less ....

Bob

[SCOTTinNJ]

Originally Posted by ROBERT CROSS

My bad Bob...I just ass-u-me that no-one is charging 24/7/365.

To your point...two screenshots. "Fully" charged and at rest a day later.

Bob
🇺🇸

Those two images look exactly as mine would look in the same circumstance. My BB's rest in that 13.2x range.

[SCOTTinNJ]

Originally Posted by uncle_bob

Hi

You do need to get up above 14.2 every so often to engage the equalizer in the BMS. Nothing much is going into the battery or coming out of it at 13.4 to 13.9V. The converter is not running at all unless you have a load somewhere pulling power. If you are pulling power and are on shore power, that's what the converter is there for. Why wear out the batteries? Stay away from 13.2V where the current is chugging in an out of the batteries all the time.....

Pretty much everything above can be observed by playing with a current monitor setup, some loads, and a programable converter / charger. It's an entertaining thing to do on a rainy day in the trailer .... You can also dig into the BB posts here and get the same info, but that's not as much fun

If the converter fan is the issue, address that point. The fan(s) on my Victron only kick on when it's doing heavy lifting ( = charging at a measured 80A into the batteries). Normal loads (lights + fridge + Alde + water pump) around the trailer don't get it going at all. Since that's probably < 8A, I don't find this alarming at all.

Bob

I think we are saying the same thing. My converter at 13.8 constant will not let the batteries drop below that. In the meantime, my solar charger will be bouncing between 0 and 14.4, or whatever max I can squeeze out of that day's sun. So I'd hit 14.4 quite often.


And yea, the Boondocker fan kicks on quite often, and at weird times. I can be at 100% battery, with hardly any loads on, and the fan will kick on. Sometimes just in the middle of the night. Probably should have gone with a Progressive Dynamics or Victron instead.

[SilverHouseDreams]

Thankfully my Progressive converter is silent, other than true bulk charging at 20-30amps or more. Initially it had some hissing switching power supply sound, but they swapped it under warranty and is not silent outside of the fan that I would ever notice outside of the sleeping hours without A/C.

As for the charging voltage, balancing cannot occur if you do not go beyond 3.6V per cell. Most LiFePO4 BMS that use the Panasonic or other individual cells, as these likely are based on voltage, cannot initiate balancing until closer to 3.65V per cell. The reason is that they use bleed-down to balance, it cannot “push” the voltage up to balance cells that are below voltage. So if you never cross >14.4V then it cannot ever assure that _every_ cell is at 100%, you could have an individual cell that keeps falling behind and could eventually short. The number of cells we are talking is likely significant, so there is a chance that a single cell could easily lag and would degrade the full pack.

I’ve assembled my own batteries from individual A123 cells when they were the sole player. I’d salvage the cells from DeWalt battery packs, resolder them into my arrangement (source was 10s, serial, packs for 36V)...and I wanted 2p5s or 2p6s for my hobby use. It wasn’t uncommon to find cells that would trail in SOC after a dozen cycles without forcing balancing. Thankfully the cells would normalize fairly well once they were balanced, but it absolutely required crossing 3.65V to get it done.

Now, my use case then was more abusive...charging at >2C and discharging at the peak of what the cells could provide (short bursts of high discharge)...and a full cycle of 100-20% SOC was within 5-10 minutes...but, my exposure to the chemistry and it’s tolerance for abuse is why i have it in my AS.

That all being said, if the battery never exceeds 14.4V it absolutely could degrade the bank of cells. Without knowing more details about the ranks of cells within the BB it is harder to calculate the risk of it happening (how many cells/capacity each per rank).

I agree that a better solution is to have a converter that hits “close enough” to 100% SOC, while the solar could provide the balancing boost voltage to 14.4-14.6V range. I actually have my MPPT set with W different charge profiles, one for active use and one for storage. The “storage” settings only target “absorption” of 13.6V, 13.55V float and then a scheduled equalization at 14.45V, I don’t remember how many days I set that to. My “in use” profile absorbs to 14.55V and 13.6V float.

My converter puts out a fixed voltage, though we often leave it turned off as I want to use the time we have hookups to validate our boondocking capacity as we are relatively new to this still. Seems that with another ~100W of solar that we could likely boondock (without A/C being needed) longer on our single BB than our schedules would normally allow us to be away.

[ROBERT CROSS]

Ok...I'll bite...😳
"The “storage” settings only target “absorption” of 13.6V, 13.55V float and then a scheduled equalization at 14.45V, I don’t remember how many days I set that to. My “in use” profile absorbs to 14.55V and 13.6V float."

Why are you charging during storage? Is it constant?
Lion's really do require a float?
How can that be when charging at a 'fixed' rate.
Do you ignore the BMS or is your, "use profile" set by your 'system'?

Scott....
Yes they would rest at the same voltage, the point is they would not reach the equalization voltage...

Bob
🇺🇸

[SCOTTinNJ]

Originally Posted by ROBERT CROSS

Scott....
Yes they would rest at the same voltage, the point is they would not reach the equalization voltage...

Bob
[emoji631]

Not reach equalization voltage because my solar is set too low? I have it at 14.4. Could go to 14.45 or 14.5.

But it will hit those numbers even if my converter is not set up to.

[SilverHouseDreams]

Originally Posted by ROBERT CROSS

Ok...I'll bite...��
"The “storage” settings only target “absorption” of 13.6V, 13.55V float and then a scheduled equalization at 14.45V, I don’t remember how many days I set that to. My “in use” profile absorbs to 14.55V and 13.6V float."

Why are you charging during storage? Is it constant?
Lion's really do require a float?
How can that be when charging at a 'fixed' rate.
Do you ignore the BMS or is your, "use profile" set by your 'system'?

The reason to have a different "absorption" and "float" voltage is to allow for a higher charge rate as the MPPT will be attempting to put out the higher voltage, but the battery would be pulling the voltage down...the higher the target differential coming out of the charger the faster it can charge. But I agree that maintaining the higher voltage 24/7 is not desirable, as the "bleed down" nature of the BMS means that it is having to dissipate any excess voltage as heat which does cause wear of some form...is it enough to matter? I don't know as I don't have specs on the BMS. The "float" is there to maintain a minimum voltage, and if the sun is shining I would rather the energy come out of the MPPT than the battery itself and causing unnecessary cycles.

As for if it is "constant", I haven't bothered to calculate how many sun hours my AS gets while it is in storage...but it is a very short "day", especially in winter. My Airstream is "covered" with the opening facing west (had stated "AS" instead of Airstream, but a simple typo makes that into a far more awkward sentence ), and I happen to reside in a northern location so the sun is largely in the southern horizon...add in the cloud cover that may last for 60+ days and the amount of solar potential is low while in storage. However, on the days it does get sun I want it to avoid unnecessary cycles on the battery.

Thankfully LiFePO4 isn't as bad as LiPo on dealing with being "charged all the time". Ever visit a coffee shop that is using an iPad as their register, which is plugged in 24x7...and the battery has puffed up and the iPad display is all distorted/lifted from the body? Clearly that is battery management that failed to account for the "always powered" use case.

[ROBERT CROSS]

Originally Posted by SCOTTinNJ

Not reach equalization voltage because my solar is set too low? I have it at 14.4. Could go to 14.45 or 14.5.

But it will hit those numbers even if my converter is not set up to.

Yes they would equalize if you've seen 100% @ 14.4-14.6v on the monitor...at least that is the way I understand it.

But what do I know I'm new here. 🤓
I'm the one who had Lifelines that that were never left in 'store' mode plugged in.
They were checked often and charged when needed, they only lasted 11yrs.🤣

Bob
🇺🇸

[ROBERT CROSS]

Originally Posted by SilverHouseDreams

The reason to have a different "absorption" and "float" voltage is to allow for a higher charge rate as the MPPT will be attempting

Never mind...👍

MPPT....that 'splains it, the MPPT is not in our loop.
Our Zamp suitcase has it's own Lithium compatible controller charging thru the 7pin...we only spent $2k😂

Bob
🇺🇸

[SilverHouseDreams]

So far my expenses are the BMV-712, BB batteries, converter, MPPT, Orion DC-DC converter. Our solar panel is some Zamp 95W that came on our 3rd hand AS. I am likely buying a Renogy solar suitcase that will just feed into the MPPT via a tongue connection, while any form of federal credits exist.

[ROBERT CROSS]

[QUOTE=SilverHouseDreams;... while any form of federal credits exist.[/QUOTE]

Full disclosure....federal credits? h/Wow did I miss out on that one? 😂

Bob
🇺🇸

[SilverHouseDreams]

There are credits for PV “install costs”, just like how if you are paying interest you may be able to deduct that as a “2nd home”. I don’t have a payment on my AS, so that doesn’t apply to me. But if I can get 30% of my solar cost back I’ll take it.

[ROBERT CROSS]

Well, worth a try on this yrs return...👍

Bob
🇺🇸

[uncle_bob]

Hi

According to the spec sheet on the BB batteries and their BMS:

14.4 to 14.6 gets the BMS into the "equalization" mode. Anything over 14.6 may cause the BMS to disconnect due to over voltage (there's a range ...). They are equalizing 4 banks of cells so there is some guesswork in terms of what they do. Are the banks split into blocks or are there just 4 of them? Anybody want to take a hammer to their $1,000 battery?

The term "float" gets BB a bit excited. Basically, lithium's don't require a float to stay happy. All you are doing with a 13.6 (or whatever) voltage is backing down to a point that you are out of equalize mode, but well above the point significant discharge occurs. It simply is a setting that allows the converter / charger to source the power to the trailer loads. The batteries would be perfectly happy if you fully disconnected them.

Bob

[SCOTTinNJ]

Originally Posted by uncle_bob

The batteries would be perfectly happy if you fully disconnected them.

Bob

In my case I dont like disconnecting the batteries only because some campgrounds have inconsistent power. If the power goes and the batteries are disconnected the fridge won't kick over to gas and the vent fans wont shut in the event of rain.

[waninae39]

these are the recommended parameters
Bulk: 14.5
Float 13.6
Absorb 0.5
equalize < 14.6 for 100AH

[ROBERT CROSS]

"Equalization"
Equalization is not recommended for our batteries. Most chargers will allow you to shut this feature off or use a setting that does not use equalization. If you cannot turn off this mode, then you will need to adjust the equalization voltage to below 14.6v

Bob
🇺🇸

[uncle_bob]

Originally Posted by waninae39

these are the recommended parameters
Bulk: 14.5
Float 13.6
Absorb 0.5
equalize < 14.6 for 100AH

Hi

You probably don't want to take the batteries to 0.5V as part of an "Absorb" cycle

Terminology gets confusing between lead acid (which does have some in's and outs) vs Lithium (which is much more simple). With the BB's 14.5 every so often and 13.5 or 13.6 the rest of the time seems to be the target. What you decide to call those phases ... up to you.

Bob

[ROBERT CROSS]

FWIW...just got a follow-up call checking if the info I recieved last week had resolved the questions I had...yes it did, thanks for asking.👍
Something to consider when selecting what path to take.

Thank You BB

Bob
🇺🇸

[ROBERT CROSS]

https://www.youtube.com/watch?v=s64CuK5Yy_o

Bob
🇺🇸