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Old 09-27-2018, 08:42 AM   #341
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Again, my AS credo applies....😘

“If your happy with what your using…it’s adequate.
If other people are un-happy….it’s not” 😂👍😂
RLC

Bob
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Old 04-01-2019, 08:59 PM   #342
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Thanks for this thread!

After reading the full thread to date, I have decided NOT to upgrade my motorhome house battery to BB LiFePo at this time. I have a WFCO 9855 3 stage converter. As SilverHouseDreams has pointed out, due to the flat voltage discharge curve, the BB battery will likely end up never reaching 100% SOC with the converters designed for Lead Acid. Thus, the BB battery with integral BMS is not truly “plug and play” as advertised by the mfr. I applaud their efforts, but the added cost and headache of changing my functional converter, on top of the price of the BB battery and a Victron 712 is too much to invest in my now 13 year old motorhome. We don’t do a lot of boon docking nor have solar. My answer would be different if we did. But I was simply looking for a more maintenance free, long term economical solution to replace my dying FLAs.

That being said, I think BB has progressed the science of RV power and I am amazed at their warranty. I hope they continue to solve these problems. Maybe they will consider the following ideas:

Like SilverHouseDreams, I think one way to solve the problem of using FLA-optimized converters might be solved with an external relay controlled by a SOC monitor or even a timer that would “fool” the converter into transitioning to bulk charge when needed or periodically, and to stay out of float mode (seems to be some confusion on if this should be avoided). This might possibly use the Victron 712 relay output. I haven’t studied the 712 programmability so not sure how sophisticated the algorithm could get, nor have I knowledge of what triggers mode transitions in the typical multistage converters (voltage alone? current? Time? Some combination?) Might BB solve the problem and offer a kit to do this?

I would be willing to modify my old WFCO 9855, even though it is a pain to remove & replace, if the mod was rather simple such as jumping the circuit board, tweaking a Pot, or changing a zener or regulator IC. But I don’t have access to schematics or theory of operation for the design and doubt if BB would have the resources to research this for multiple converters.

Finally, our motorhome sits in our driveway plugged-in when not in use. From what I have read, the ideal SOC for LiFePo battery storage is near 60%. So it would be nice to have a user control to place the BMS or converter in non-charge accept mode until that level is reached, anticipating storage. Yes, it would have to be switched ahead of time depending on load, but why not include this feature?

PS: Thanks to SilverHouseDreams for his knowledge, and actual test and measurements! You saved me some up-front $$ for now.
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Old 04-02-2019, 07:49 AM   #343
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Quote:
Originally Posted by EVOFXDWG View Post
After reading the full thread to date, I have decided NOT to upgrade my motorhome house battery to BB LiFePo at this time. I have a WFCO 9855 3 stage converter. As SilverHouseDreams has pointed out, due to the flat voltage discharge curve, the BB battery will likely end up never reaching 100% SOC with the converters designed for Lead Acid. Thus, the BB battery with integral BMS is not truly “plug and play” as advertised by the mfr. I applaud their efforts, but the added cost and headache of changing my functional converter, on top of the price of the BB battery and a Victron 712 is too much to invest in my now 13 year old motorhome. We don’t do a lot of boon docking nor have solar. My answer would be different if we did. But I was simply looking for a more maintenance free, long term economical solution to replace my dying FLAs.

That being said, I think BB has progressed the science of RV power and I am amazed at their warranty. I hope they continue to solve these problems. Maybe they will consider the following ideas:

Like SilverHouseDreams, I think one way to solve the problem of using FLA-optimized converters might be solved with an external relay controlled by a SOC monitor or even a timer that would “fool” the converter into transitioning to bulk charge when needed or periodically, and to stay out of float mode (seems to be some confusion on if this should be avoided). This might possibly use the Victron 712 relay output. I haven’t studied the 712 programmability so not sure how sophisticated the algorithm could get, nor have I knowledge of what triggers mode transitions in the typical multistage converters (voltage alone? current? Time? Some combination?) Might BB solve the problem and offer a kit to do this?

I would be willing to modify my old WFCO 9855, even though it is a pain to remove & replace, if the mod was rather simple such as jumping the circuit board, tweaking a Pot, or changing a zener or regulator IC. But I don’t have access to schematics or theory of operation for the design and doubt if BB would have the resources to research this for multiple converters.

Finally, our motorhome sits in our driveway plugged-in when not in use. From what I have read, the ideal SOC for LiFePo battery storage is near 60%. So it would be nice to have a user control to place the BMS or converter in non-charge accept mode until that level is reached, anticipating storage. Yes, it would have to be switched ahead of time depending on load, but why not include this feature?

PS: Thanks to SilverHouseDreams for his knowledge, and actual test and measurements! You saved me some up-front $$ for now.
Hi

Swapping out the batteries is a "thousands of dollars" sort of thing. If you mount them "indoors", it's a bit of work. Swapping out the converter is a trivial amount of work in comparison. Cost wise, there are a number of outfits that will sell you
one for $200 or less.

Changing the converter: (assuming the batteries are out already, and power is off)

Remove the mounting screws

Detach the output wires

Detach the AC power wires

Throw away the old converter

Attach the output wires to the new converter

Attach the AC power wires

Screw in the mounting screws

I suspect that your local RV shop would charge you the minimum 1 hour of labor for the job. No cables to make up or wiring to re-route. Mounting might involve adapting the old "tray" to hold the new unit, even that is a 15 minute job.

Judging by the posts here on the forum, roughly 100% of all members replacing batteries also replace converters. If you toss in those who replace the converter *without* replacing the batteries, you would most certainly be over 100%.

=====

If you are concerned about your lithium's storage - what about your lead acid's?
They most certainly are *not* at all happy running on charge 100% of the time. You will indeed shorten their life by what you are doing. If anything lithiums are *more* tolerant (not less) of this sort of treatment.

Bob
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Old 04-03-2019, 09:15 AM   #344
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Originally Posted by uncle_bob View Post
Hi

Swapping out the batteries is a "thousands of dollars" sort of thing. If you mount them "indoors", it's a bit of work. Swapping out the converter is a trivial amount of work in comparison. Cost wise, there are a number of outfits that will sell you
one for $200 or less.

:

:
Bob
Uncle Bob: my motorhome converter is behind a stapled in panel under the kitchen sink cabinet. I can barely get my phone camera in there to take a picture of it over the partition (that is how I identified it). I would have to disassemble part of the cabinet or remove it from the wall for access. If I do changeover, I will likely remount somewhere else or at least where I don't have to remove and replace wood. Coachmen didn't mount it for maintenance!

I am contemplating mounting a LiFePO4 compatible converter in the battery compartment, and closing in and insulating that portion of the battery compartment for that purpose. I may leave the existing converter in place and wire with a 120V switch to let me select which one is used.

I will likely change over in the next couple of years just to get the long term value and maintenance free benefit of LiFePO4. But currently one of my two FLA's appears still good and I just purchased a very small portable inverter generator I can use when needed.

One other consideration in my delay is we actually "use" the capacity of our house batteries very little since we only boondock occasionally when transiting. I would like to think more about how to more automatically put/keep the LiFePO battery in ideal state of charge for "storage" (50-60%), Which is what we should do while we are camping on shore power, driving, or the motorhome is sitting in the driveway waiting on the next trip. I dont want to "use up" LiFePO cycles when I don't need to. I certainly need to install an extra 120V switch or relay so I can power the motorhome (I set the A/C on 90F in summer since we are in middle GA) in the driveway or at a campground but turn off the battery charger.

One other consideration is I don't have the wiring diagrams for my motorhome and need to positively determine if house battery is charged from alternator when engine is running. If so, I would have to do something about preventing overcharging, even if it is just disconnecting from motor charge circuit.

PS: I am thinking about implementing my own "battery system manager" on an Arduino or other microcomputer to do some of the above. It would have to work in conjunction with a Victron or other monitor (something that provided true State of Charge information on some output or relay control signals at programmable SOC thresholds). I would flip a switch when I wanted to enter/stay in storage mode. Of course I would have to do this a day or two before arriving home, and remember to flip to "use mode" a few hours before unplugging from shore in anticipation of a boondock night.
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Old 04-04-2019, 08:39 AM   #345
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Quote:
Originally Posted by EVOFXDWG View Post
Uncle Bob: my motorhome converter is behind a stapled in panel under the kitchen sink cabinet. I can barely get my phone camera in there to take a picture of it over the partition (that is how I identified it). I would have to disassemble part of the cabinet or remove it from the wall for access. If I do changeover, I will likely remount somewhere else or at least where I don't have to remove and replace wood. Coachmen didn't mount it for maintenance!

I am contemplating mounting a LiFePO4 compatible converter in the battery compartment, and closing in and insulating that portion of the battery compartment for that purpose. I may leave the existing converter in place and wire with a 120V switch to let me select which one is used.

I will likely change over in the next couple of years just to get the long term value and maintenance free benefit of LiFePO4. But currently one of my two FLA's appears still good and I just purchased a very small portable inverter generator I can use when needed.

One other consideration in my delay is we actually "use" the capacity of our house batteries very little since we only boondock occasionally when transiting. I would like to think more about how to more automatically put/keep the LiFePO battery in ideal state of charge for "storage" (50-60%), Which is what we should do while we are camping on shore power, driving, or the motorhome is sitting in the driveway waiting on the next trip. I dont want to "use up" LiFePO cycles when I don't need to. I certainly need to install an extra 120V switch or relay so I can power the motorhome (I set the A/C on 90F in summer since we are in middle GA) in the driveway or at a campground but turn off the battery charger.

One other consideration is I don't have the wiring diagrams for my motorhome and need to positively determine if house battery is charged from alternator when engine is running. If so, I would have to do something about preventing overcharging, even if it is just disconnecting from motor charge circuit.

PS: I am thinking about implementing my own "battery system manager" on an Arduino or other microcomputer to do some of the above. It would have to work in conjunction with a Victron or other monitor (something that provided true State of Charge information on some output or relay control signals at programmable SOC thresholds). I would flip a switch when I wanted to enter/stay in storage mode. Of course I would have to do this a day or two before arriving home, and remember to flip to "use mode" a few hours before unplugging from shore in anticipation of a boondock night.
Hi

Here's the gotcha: This is Airforums, a forum for Airstream owners and owners of vehicles made by Airstream, but possibly not labeled as such. Airstream (at least 99%) of the time, mounts converters where you can get at them. The default assumption here is going to be based on an Airstream.

There *is* a section in the control panel where you can (and should) enter the information about the rig you have. That will show up on your posts and give people some clue about what you are running. If it's something odd, I'd suggest that this is a pretty important thing to do.

You have a number of issues that are *very* specific to the rig you own. Getting the answers to those questions ("How do I get at the converter?" ....") seems like a pretty high priority. Given that converters do fail and do get replaced, I'd bet people have pulled them out before. There may not be a "magic" zero effort way to do it. There likely is a "not quite as bad" way to do it. Digging on a forum that is specific to your rig is far more likely to turn that up. ( ... pull these five bolts and the cabinet swings out ... ). Same thing applies to things like wiring diagrams.

Abandoning odd chunks of this and that is usually not a good idea. They randomly disintegrate and eventfully do odd things like catch fire. Pulling the converter is the right way to do it. Based on the description, I'd put in a panel that is held in with clips (like Airstream does it) so you can get access easily. At the very least I would un-wire it from shore power and the 12V lines. You might be able to do that without actually getting to the converter.

Assuming that the converter does what it's specs claim ( 14.4 V float, 13.6V absorption) BB's *will* fully charge. They will drop back to about 75% in "float" mode before they charge back up to 100% again. If the discharge rate is > 10A, you will go back into full charge a lot sooner than the 75% point. That's hardly the end of the world if you want to leave it in place.

======

If you rarely discharge the batteries, Lithium's are going to last "forever". At a rational usage rate, you have > 5,000 "full discharge to zero capacity" cycles. If you go dead flat once a week, that's 10 years. Discharge less often or not as deep and you are out at 20 or 30 years. Even then the "end of life" is a very arbitrary capacity limit. You might be quite happy to keep on going for more cycles until you hit 70% capacity batteries .... There are a *lot* of people who do exactly that with lead acid's.

What *will* kill them? We'll only know in 10, 20, or 30 years. The first 10 years are all in warranty. It's a pretty good bet that *something* will, but maybe not discharge cycles. There is no need to baby lithium batteries. There also is the minor point of - will you own and actively use this RV for another 10, 20, 30 years?

Your "only store at 50%" idea simply is not a big deal. Adding cycles to the battery to discharge it before you go into storage / charge it to 100% when you come out does not make sense. Much better / easier / safer / more reliable / lower stress to do what we always have done and roll along with fully charged batteries. Parked in a giant 20 hour traffic jam? ... batteries are fully charged ....

Part of your concern is that you simply don't need batteries. That's most certainly a *very* valid point. However it really has nothing to do with lithium's or any other battery approach. If you can do everything you want to do with the capacity and gear you have, don't change. However that's *not* the same as "I have a problem with a lithium conversion ....". Cost wise, you *do* need a compelling case to make this switch.

Based on bits and pieces of information you have dropped, it sounds like your plan is to mount the batteries outside the heated area of the vehicle. Again this is just a guess. If so - where do you live and where to you plan to be in the winter? Will you be in the RV in freezing temperatures?. That is a *very* valid concern when it comes to lithium power.

Depending on just how well protected the battery section of the coach is, mounting a charger / converter there may or may not be a real good idea. they are very much designed for a non-challenging environment. Dirt, moisture, salt, and extreme temperature generally are not on the list of things they deal with well. Since they also require good ventilation for cooling, outside mounting would be a challenge.

Lots of fun !!!

Bob
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Old 02-13-2020, 11:34 PM   #346
CLOUDSPLITTER "Tahawus"
 
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For those who store bb's in the as...

I have stored our BB's in the AS, isolated, fully charged this and all last season.
If others are doing the same what are they resting at?

Nine day snapshot.
3/04/20 13.91v 1:30pm Charged rested 6hrs
3/04/20 13.38v 11:30pm 33*
3/05/20 13.32v 9:00am 29*
3/06/20 13.29v 9:00am 26*
3/07/20 13.28v 5:00pm 27*
3/09/20 13.28v 8:00pm 36*
3/11/20 13.28v 10:26pm 35*
3/13/20 13.28v 7:35 pm 26*

Bob
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RLC

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Sweet Streams....🌥
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Old 02-15-2020, 08:31 AM   #347
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Originally Posted by ROBERT CROSS View Post
I have stored our BB's in the AS, isolated, fully charged this and all last season.
If others are doing the same what are they resting at?

Nine day snapshot.
3/04/20 13.91v 1:30pm Charged rested 6hrs
3/04/20 13.38v 11:30pm 33*
3/05/20 13.32v 9:00am 29*
3/06/20 13.29v 9:00am 26*
3/07/20 13.28v 5:00pm 27*
3/09/20 13.28v 8:00pm 36*
3/11/20 13.28v 10:26pm 35*
3/13/20 13.28v 7:35 pm 26*

Bob
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Hi

Mine went in last year at 13.45 and came out at 13.45 ....

Bob
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Old 02-15-2020, 10:22 AM   #348
CLOUDSPLITTER "Tahawus"
 
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Thanks Bob

Well, I'm at 12.70v today at 18*.

Supposed to get above 40* tomorrow, we'll see.

Last season I didn't do a log.
Just 13.4 in the Fall and 13.0 Spring.

I fear I may fret too much.🥴

Bob
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RLC

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Sweet Streams....🌥
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Old 02-16-2020, 08:19 AM   #349
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Hi

Given the cost of these things, I'm not sure that you *can" worry to much ....

Bob
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Old 02-16-2020, 09:27 AM   #350
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👍 I am now fretless...

3/16/20 13.28v 10:40am 35*

I now have my own black & white on how much temp matters.

Bob
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"Any nation that can survive what we have lately in the way of government, is on the high road to permanent glory."
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RLC

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Sweet Streams....🌥
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Old 02-17-2020, 09:08 AM   #351
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Hi

The only reference I can quickly find:

https://pubs.rsc.org/en/Content/Arti...H#!divAbstract

Is behind a paywall. The abstract seems to say that (like most batteries) the temperature coefficient on these cells is negative. The voltage goes down as temperature rises.

Maybe your voltmeter doesn't like the cold

Bob
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Old 02-17-2020, 10:41 AM   #352
CLOUDSPLITTER "Tahawus"
 
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Perfectly clear...
Geralmente, o potencial dos eletrodos da bateria de íons de lítio (a temperatura constante) é expresso contra o lítio metálico, assumindo que seja igual a zero. No caso de potenciais coeficientes de temperatura e, portanto, entropias, nenhuma suposição semelhante pode ser aplicada, pois é contra o terceiro princípio da termodinâmica. Aqui, os coeficientes de temperatura do potencial de eletrodo único foram estimados usando uma 'suposição de potencial de difusão térmica desprezível'. A dependência da tensão em circuito aberto (Δϕi) da temperatura T, para três cátodos de bateria de íons de lítio, foi medida em células simétricas não isotérmicas (ambos os eletrodos tinham a mesma composição, mas foram mantidos em diferentes.

Thanks Bob....I think.

Bob
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"Any nation that can survive what we have lately in the way of government, is on the high road to permanent glory."
Molly Ivins

“Growing Old…being able to think about things you can no longer remember.”
RLC

"Never tow faster than your Guardian Angel can Fly"


Sweet Streams....🌥
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Old Yesterday, 08:36 AM   #353
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Hi

Now I have to go find one written in Greek .....

Bob
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