Least troublesome 7s LiCo Battery Murdering Systems

[SamTexas]

Yes, I am fully aware that most if not all BMSs are junk. But this is not for me.

I'm assembling a 24V LiCo battery from scratch for a friend of mine. He's 1,500 miles away so I can't be the occasional human BMS for the pack. So I am looking for inputs from members that have actually used a 7s, 30A or higher LiCo BMS. For the moment, let's assume that cost is a non-issue. I would appreciate actual measured/test data if available. Specifically

0) BMS brand and model. Link if available.
1) What is the BMS's current draw, and from which cells?
2) Can the BMS's actually balance a relatively out of balanced pack? 4.00V for 3 cells, 4.10V for 3 cells and 4.20V for 1 cell.
3) If yes for [2], how long does it take to balance a 20Ah pack?
4) Does the BMS overcharge one or more cells when the pack is unbalanced (as in [2])
5) What is the low voltage threshold (created by the BMS itself) for the BMS to stop working all together?

For those who love to give opinions, please don't. I'm looking for real data, real experiences. Thanks in advance for contributing (and for NOT contributing).

 

[miuan]

I'm sorry for derailing, but I'm sure many of us would just use a RC Charger with this cell count. Why not do that in this case, and program the controller for a fail-safe lvc?

 

[SamTexas]

I'm sorry for derailing, but I'm sure many of us would just use a RC Charger with this cell count. Why not do that in this case, and program the controller for a fail-safe lvc?

Yes, that is the current backup plan. Still I want to locate that working (or least troublesome) BMS. A WORKING BMS is better and simpler than a balancing charger because the user doesn't need to handle the balance wires.

 

[999zip999]

I think methods LVC- HVC boards are the ones people are using.

 

[DrkAngel]

See - BMS Included for Recycled Laptop Battery Builds?

 

[melodious]

I think methods LVC- HVC boards are the ones people are using.

Unavailable from what I've surfed on his site. 4S, 5S, 6S is what I can find (I've been kinda hounding http://www.methtek.com/ this morning). And a mention from someone here about him making an 8S board within a few months. Not sure If he's going to just skip 7S altogether...

 

[SamTexas]

I think methods LVC- HVC boards are the ones people are using.

Unavailable from what I've surfed on his site. 4S, 5S, 6S is what I can find (I've been kinda hounding http://www.methtek.com/ this morning). And a mention from someone here about him making an 8S board within a few months. Not sure If he's going to just skip 7S altogether...

Thanks for the pointer but I'm not at all interested in this product.

 

[wesnewell]

Google 7s lipo bms and you will find a bunch of them.

 

[melodious]

My bad. Read your thread again. You want a reliable & dependable BMS on a 7S 24V LiCo @ some unspecified # of parallels.

 

[Kin]

Since most low-cost low power balancing chargers don't put out much power, you can do balance charging and main charging through the balance wires. Mdd0127 did that with his 14S hyperion. The balance output and charger output go to a 13 terminal molex block so there's just one thing to plug in, in addition to the balancing charger input. I was charging at 5A and that was no problem.


Not to rag on an old idea or distract from the topic of the thread. I think there are a lot of reasons one might still opt for a BMS instead.

 

[amberwolf]

Since most low-cost low power balancing chargers don't put out much power, you can do balance charging and main charging through the balance wires.

Perhaps, but AFAICT this:

A WORKING BMS is better and simpler than a balancing charger because the user doesn't need to handle the balance wires.

negates doing that in this case.

I think methods LVC- HVC boards are the ones people are using.

Unfortunately Methods' system does not do any balancing, which is one of the things asked about in the OP.


I wish I could help find the unit desired for the OP, but I don't have any ideas on that.

 

[Kin]

Since most low-cost low power balancing chargers don't put out much power, you can do balance charging and main charging through the balance wires.

Perhaps, but AFAICT this:

A WORKING BMS is better and simpler than a balancing charger because the user doesn't need to handle the balance wires.

negates doing that in this case.

I noticed SamTexas said this, but what I was trying to describe is a situation that involves just handling the balance taps as one bunch, which (I was claiming) is really the same as handling the regular charge leads. In fact, you get to avoid the problem of your main leads sparking, because you can leave them connected to the controller (as long as the drain isnt too bad.)

 

[amberwolf]

Ah, that makes sense.

 

[Kin]

Cool! I don't always explain things well when I first type them . Recently I've also noticed this pompous flair in my ES writing and I'm worrying all about it. You know, most things would be better communicated if I just thought to type as I would speak. I guess I wasn't explicit the first time I posted, that while the combined balance wires could be considered admittedly not what was asked for by the OP, but perhaps an equivalent solution.

 

[999zip999]

typing is like talking and spelling plus thinking at the same time. I don't do to well.

 

[Kin]

typing is like talking and spelling plus thinking at the same time. I don't do to well.

I like the way you put it. I think most of us could benefit from framing the situation so we're not caught in that trap. It's analogous to doing basic arithmetic- if you start engaging the numbers as visual objects, it can boot up a complex graphical component to what is a simple arithmetic experience. I can do math much better when I disengage the object visualization (except for problems of a graphical nature). In the same sense, if you type with so many complications (talking, spelling, thinking, and physically writing), you can over-complicate what is just another form of talking and should be no harder. Well, I used a lot of words to describe something that might be very subjectively described.
/END OF FF TOPIC RANT.

Sorry about that Samtexas.