Wiki Entry Review: BMS

HRTKD

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Definitely not! Anything that big no one would read. Ideally it's just the most important stuff with links to follow-ups, not restricted to BMS selection alone. But hey, your forums if you think it needs more or less let's do it! ;-)

No, I was more or less asking a rhetorical question, because some of the discussion was leading the document to become a "heat the ocean" type project. LIke you said, too much and nobody will read it. Too much and it will be difficult to maintain.
 

Maast

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<whoosh!>
That was the sound as most of your post went over my head! ;)

So, the first paragraph makes it sound like active balancers aren't very useful after all....? In my one and only pack build my passive BMS has teeny tiny resisters capable of burning mW ... certainly not handling amps ... but then the cells are well balanced, their C-Rate is about 3.3 Amps, and the resistors don't even get hot to the touch. So the thought of a 1 amp balancing burn is pretty amazing (I know your cells are 120 Ah, 36x mine)

Based on the second paragraph, would it be correct to add that active balancers may be warranted in packs with cells that have a greater than 8% mismatch or more (10 ah/120 ah = 8%)? And from the last paragraph, that the minimum current they can carry should be sized no less than 1% the C-Rate?
Sorry, should have been a bit more specific. What I should have explicitly said was that active balancers do not increase effective capacity enough to make much of a difference unless you have a VERY low discharge rate. What they're indispensable for is on large and/or badly mismatched packs from keeping the cells from drifting apart leading to premature pack shutdown. In the same situation a passive balancer just can not burn off enough charge to keep the packs balanced - unless you wait a couple of days between charge/discharge cycles which isnt very practical.

You second statement sounds about right, a 1000ah battery cell groups would need about a 10A balancer. Keep in mind this is all anecdotal so you only have a sample size of 1 working with extraordinarily shitty battery modules so other peoples results may vary, but it sounds like Steve has data similar to mine. New cells can probably get by with a less capable balancer. On the other hand new cells don't stay new forever.
 

Steve_S

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  • What they're indispensable for is on large and/or badly mismatched packs from keeping the cells from drifting apart leading to premature pack shutdown. In the same situation a passive balancer just can not burn off enough charge to keep the packs balanced - unless you wait a couple of days between charge/discharge cycles which isnt very practical.

You second statement sounds about right, a 1000ah battery cell groups would need about a 10A balancer. Keep in mind this is all anecdotal so you only have a sample size of 1 working with extraordinarily shitty battery modules so other peoples results may vary, but it sounds like Steve has data similar to mine. New cells can probably get by with a less capable balancer. On the other hand new cells don't stay new forever.
Quite correct. What many if not most do not quite understand, is that even 2 years ago, cells above 150AH were nowhere near as common as they are today. now 200-300 are "common goods". Passive can actually work really well with small/low capacity cells like 25 & 50AH because they just do not have a massive volume to work "against" as such. BY the time you get to "the big boys" of 200+AH a 1.2A Passive just cannot keep up. I ONLY use it because it helps take the top & bottom edges off a bit and gives the Active Balancer a little extra help because even that can't shift the juice fast enough when reaching the High Points of charge. And as I stated, there is inherent risks involved if using both Passive & Active, one of which is that it can skew a BMS' readings resulting it doing the wrong thing and possibly resulting in greater damage.
 

svetz

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A big thank you (literally ;-) to everyone for helping out with this. I've got all the suggested changes in now (I think) except for the double-checking/verifying the latest literature on micro-cycles and memory effects as @snoobler and @Steve_S suggest. I'll be working on that in my copious leisure time and update what I find in the LiFePO4 wiki thread, but if anyone comes across any additional recent literature regarding it or BMSes please cite it. Naturally, if you spot anything in error please speak out. To HRTKD's point, not all the nitty gritty is in the wiki, but hopefully there's enough clear information that someone interested in the nitty gritty can go after it.

... to become a "heat the ocean" type project...
Pfft... were it so easie peasy ;)
 

Maast

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During that process, I FRIED one Chargery BMS-8T and one QNBBM-8S which was a fairly expensive set of lessons but I "had to know" where edge cases an.......
At least you got some work out of it, I destroyed my first Chargery 16T within a week because it was sitting on the lid of the 30 gallon test load water drum and I bumped it and the lid popped up and sent the energized Chargery to the bottom of the barrel.
 

snoobler

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As well you should!

BMSes have no memory affect as far as I know. Fortunately, there's nothing in the BMS wiki entry on a memory affect. I suspect you're talking about the recent LiFePO4 entry, which has it's own thread so I'll respond to your post over there in a bit.

DOH... replied to wrong thread... what a dummy. :)
 

ArthurEld

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These guys trying to organize the place really would like us to keep track of where we are.
They prefer that we talk about things they understand too.
 

DerpsyDoodler

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A big thank you (literally ;-) to everyone for helping out with this. I've got all the suggested changes in now (I think) except for the double-checking/verifying the latest literature on micro-cycles and memory effects as @snoobler and @Steve_S suggest. I'll be working on that in my copious leisure time and update what I find in the LiFePO4 wiki thread, but if anyone comes across any additional recent literature regarding it or BMSes please cite it. Naturally, if you spot anything in error please speak out. To HRTKD's point, not all the nitty gritty is in the wiki, but hopefully there's enough clear information that someone interested in the nitty gritty can go after it.


Pfft... were it so easie peasy ;)
To summarize Steve_S’ earlier post, BMS‘ are a complex subject with lots of literature.

New technologies and approaches are emerging all the time. How often will the wiki be reviewed and updated with changes based on new findings or more debunked myths? Who will be responsible for that? Technology grows and changes fast, as I am sure any EE is aware of. What was wrong with Steve’s suggestion of linking to authoritative literature as opposed to culminating this wiki that will need to be reviewed and updated on a regular basis to keep accurate? Why is diysolar trying to recreate a system of peer review when experts in the field have already done this? Is this an attempt at a wiki for the layman? If so, keeping it simple without all the explanation and detail seems best..... all the way to include a list of “gotchas” (or common mistakes) that people new to the whole BMS thing might make and can be avoided.

What is the actual goal of this wiki? Who is the intended audience?
 

ArthurEld

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To summarize Steve_S’ earlier post, BMS‘ are a complex subject with lots of literature.

New technologies and approaches are emerging all the time. How often will the wiki be reviewed and updated with changes based on new findings or more debunked myths? Who will be responsible for that? Technology grows and changes fast, as I am sure any EE is aware of. What was wrong with Steve’s suggestion of linking to authoritative literature as opposed to culminating this wiki that will need to be reviewed and updated on a regular basis to keep accurate? Why is diysolar trying to recreate a system of peer review when experts in the field have already done this? Is this an attempt at a wiki for the layman? If so, keeping it simple without all the explanation and detail seems best..... all the way to include a list of “gotchas” (or common mistakes) that people new to the whole BMS thing might make and can be avoided.

What is the actual goal of this wiki? Who is the intended audience?
I think the reason they decided to use a wiki is because it is difficult to search for info on the site.
Interesting subject about who's going to keep it up. Aren't wiki's supposed to be open to input from everybody? 🥺
 

Steve_S

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@DerpsyDoodler I don;t think that Vetz or anyone else intended this to be the Be All & End All of info but rather an "At a Glance Summary Snapshot" with quick important details. There is no possible way to incorporate the minutia of details, which as you said in the EE world it's all fast moving. Only have to look back One Year to see how much things have evolved in BMS land, let alone 2,3 or 5 years.

At least this WIKI Software is not as hostile & tedious like "Wikipedia" WIKI software which demands "Hand to Keyboard Combat" with their fricken markup language... and I hated Wordstar 2000 TOO ! Most of you whippersnappers never heard of that fugly beast, count yourselves LUCKY!.

I believe it would be prudent to keep a lid on Wiki Contributions on a site like this because it can also go pear shaped quickly, seen it far too many times. Ideally a Base Foundation Page is written up with accurate & verified details with references and attributions to said material is generally the first order and then to build on it. I believe Svetz started this thread with that intention and now I see people had "discussed" in the wiki which is NOT for that purpose. Discussion inside a Wiki Doc & Pages virtually kills it's purpose, it is not a discutional facility, that's for forum threads.
 

DerpsyDoodler

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@DerpsyDoodler I don;t think that Vetz or anyone else intended this to be the Be All & End All of info but rather an "At a Glance Summary Snapshot" with quick important details. There is no possible way to incorporate the minutia of details, which as you said in the EE world it's all fast moving. Only have to look back One Year to see how much things have evolved in BMS land, let alone 2,3 or 5 years.

At least this WIKI Software is not as hostile & tedious like "Wikipedia" WIKI software which demands "Hand to Keyboard Combat" with their fricken markup language... and I hated Wordstar 2000 TOO ! Most of you whippersnappers never heard of that fugly beast, count yourselves LUCKY!.

I believe it would be prudent to keep a lid on Wiki Contributions on a site like this because it can also go pear shaped quickly, seen it far too many times. Ideally a Base Foundation Page is written up with accurate & verified details with references and attributions to said material is generally the first order and then to build on it. I believe Svetz started this thread with that intention and now I see people had "discussed" in the wiki which is NOT for that purpose. Discussion inside a Wiki Doc & Pages virtually kills it's purpose, it is not a discutional facility, that's for forum threads.

All I am saying is it seems like a lot of work to do and to have to keep up with on a regular basis for people that aren’t paid. Is there a formally defined policy for when the wiki gets reviewed and updated? if you’re only posting authoritative links in chronological date order with a brief description or title, it really minimizes the work associated with maintenance. Perhaps by starting the entry with a brief primer about what a BMS is (and/or is not), a list of commonly used acronyms related to BMS, a list of caveats/gotchas, and then authoritative literature links for those who want to deep dive. I don’t want to try and beat up this subject, so that’s all I’ll post on the matter. It’s my opinion, I made it known, and that is good enough for me.
 

ArthurEld

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My BMS has 4 wires. It is a common port (same port?) but it can shut off just charging or just discharging.
Seems like a subject that people would want to know.

Am I thinking correctly?
 

svetz

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...How often will the wiki be reviewed and updated with changes based on new findings or more debunked myths? Who will be responsible for that? Technology grows and changes fast, as I am sure any EE is aware of. What was wrong with Steve’s suggestion of linking to authoritative literature as opposed to culminating this wiki that will need to be reviewed and updated on a regular basis to keep accurate? Why is diysolar trying to recreate a system of peer review when experts in the field have already done this? Is this an attempt at a wiki for the layman? If so, keeping it simple without all the explanation and detail seems best..... all the way to include a list of “gotchas” (or common mistakes) that people new to the whole BMS thing might make and can be avoided.
All good points, there's actually a wiki entry on writing wiki entries that says much the same (see Writing Wiki Entries). There's nothing wrong with Steve's idea, that's what we're trying to accomplish.

Ideally entries are the basics for a beginner with either links or enough information that someone can get to more expert information, ideally they are time defying. But you're also correct that as our understanding grows or new facts come to light what we "commonly believe" can be quite wrong. Hopefully when those come to light in the forums the wiki will get updated by a member, or someone reading the wiki will "report" it as incorrect and then it'll get updated.

That said, if any of those goals weren't met then let us know how it could be better and someone with wiki authoring privileges will update it.

Why is diysolar trying to recreate a system of peer review when experts in the field have already done this?
DIY Solar's mission is to be a teaching site. While there are some experimenters here reporting their findings, the ultimate goal is for those who have questions about solar technologies to learn. A lot of that is to separate fact from fiction, expert from crackpot. As such, it's important to make sure that items in the wiki and FAQ entries are reviewed for accuracy. It's not a repeat of what other experts have done, it's more of an interpretation of what the experts have learned for the layman and the the poster's understanding is correct. And yes, there should be links or enough information so those that want more can research deeper into it.

Yes it takes time, we're human and make mistakes, and even the best entries will need periodic tuning. Hopefully there will always be members that feel it's important enough to do to make the time to do it.

I think the reason they decided to use a wiki is because it is difficult to search for info on the site.
Exactly right. The Wiki entries are intended to be concise and simple. Ideally it's the sum of basic knowledge from everyone and removes any bias; so they take seconds to read rather than the hours you might spend wandering the forums. The downside is a loss of nuance, for example I've learned a lot in the discussion in this thread alone and those facts won't make it into the wiki just because they are too nuanced.

All I am saying is it seems like a lot of work to do and to have to keep up with on a regular basis for people that aren’t paid.
I get paid. It's in thank-you's, a thumbs up button, a smiley face, or best yet a response (members have helped me a lot). It'll be the currency of the realm after singularity so it's good to start early 😜

Is there a formally defined policy for when the wiki gets reviewed and updated?
The current policy is members should report anything incorrect. But, I can see where a periodic review would be useful. Possibly we'll get more organized as the entries age more or someone steps up for it.
 

DerpsyDoodler

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All good points, there's actually a wiki entry on writing wiki entries that says much the same (see Writing Wiki Entries). There's nothing wrong with Steve's idea, that's what we're trying to accomplish.

Ideally entries are the basics for a beginner with either links or enough information that someone can get to more expert information, ideally they are time defying. But you're also correct that as our understanding grows or new facts come to light what we "commonly believe" can be quite wrong. Hopefully when those come to light in the forums the wiki will get updated by a member, or someone reading the wiki will "report" it as incorrect and then it'll get updated.

That said, if any of those goals weren't met then let us know how it could be better and someone with wiki authoring privileges will update it.


DIY Solar's mission is to be a teaching site. While there are some experimenters here reporting their findings, the ultimate goal is for those who have questions about solar technologies to learn. A lot of that is to separate fact from fiction, expert from crackpot. As such, it's important to make sure that items in the wiki and FAQ entries are reviewed for accuracy. It's not a repeat of what other experts have done, it's more of an interpretation of what the experts have learned for the layman and the the poster's understanding is correct. And yes, there should be links or enough information so those that want more can research deeper into it.

Yes it takes time, we're human and make mistakes, and even the best entries will need periodic tuning. Hopefully there will always be members that feel it's important enough to do to make the time to do it.


Exactly right. The Wiki entries are intended to be concise and simple. Ideally it's the sum of basic knowledge from everyone and removes any bias; so they take seconds to read rather than the hours you might spend wandering the forums. The downside is a loss of nuance, for example I've learned a lot in the discussion in this thread alone and those facts won't make it into the wiki just because they are too nuanced.


I get paid. It's in thank-you's, a thumbs up button, a smiley face, or best yet a response (members have helped me a lot). It'll be the currency of the realm after singularity so it's good to start early 😜


The current policy is members should report anything incorrect. But, I can see where a periodic review would be useful. Possibly we'll get more organized as the entries age more or someone steps up for it.
Consider yourself paid! 😜 Thank you’s and likes are nice, not saying they aren’t, but at some point tedious/monotonous stuff gets...well....tedious and monotonous... perhaps I’m making something out of nothing?
 

svetz

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My BMS has 4 wires. It is a common port (same port?) but it can shut off just charging or just discharging.
Seems like a subject that people would want to know.

Am I thinking correctly?
From what the link shows there are two B- and two P-, and no C-. So it looks like a four wire common. At a guess it's because it's 200 Amps and they needed to split the current.

So, thanks for bringing that up! It just goes to show that even though 2/3 wire is a common term, it's confusing. So, altered the entry to de-emphasize 2 vs. 3, added a graphic, and put the emphasis on charging/discharging rather than 2 vs. 3.

Hopefully it's better, but if I messed anything up you know what to do!

... perhaps I’m making something out of nothing?
I think what you're saying is smart, those are all valid concerns.
 
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