MBM Manual Battery Management

MBM Manual Battery Management





I have used cheap Chinese balancing boards and found they failed easily and never achieved anything I thought was of value. At some point I realized "Why not simply manually manage a battery?"

Another big revelation was that "Bottom Balancing" is really the way to go for protecting your individual cells because it's when you are out riding and run too low that damage happens. "Bottom Balancing" means you get a very clear warning you are out of charge.

Anyway... the concept is very simple.

The XT-90 is your "Power" connection.

The XT-60 gives direct access to "Individual Cells". (so you read 2.5 volts to 4.2 volts there)

The Rotary Switch simply "Changes the Channel" so you access the cells one at a time.

And the great thing about it is you can use a big Resistor to lower the charge or I have a hacked USB that can add 5 volts at 2 amps. Everything can be balanced pretty fast.

Once you get everything right it does not deviate much.

This pack has 10S so with 11 Positions I have a spare "OFF" option. Things would get more difficult with more cells because most of these are limited to 11 Positions.

I probably ought to do the electrical diagram... but maybe on a later post. It's pretty easy to figure out.

Okay... so these Rotary Switches have a "Stationary" part which is where the XT-60 is connected.

As you rotate the switch it engages each pair of the 11 possible "Positions".

Using regular balancing wire sequencing it means the positive side of the first pair becomes the negative in the next. Then just repeat that over and over.

Be careful you buy a "Break Before Make" type switch because the other type creates a short.

Not the best drawing, but good enough.

"Top Balancing" or "Bottom Balancing" and Charging and Discharging

The strategy you decide upon is really up to you. "Top Balancing" will give you a slight edge with peak voltage but typically you lose that after you use up the top 5% of your capacity. "Bottom Balancing" is for people more concerned about protecting a small pack from damage. When you have a really large pack some try to balance more in the middle and just avoid either extreme. As long as you know what strategy you are operating with they all work.

One trick is when you charge you can rotate through and check voltages of each cell. I quickly am able to "know" which cell is struggling. You can then simply key off that cell when charging which I also do manually. I do very fast charging (under 20 minutes) so I watch things very carefully each time. That's for a different battery than this one which is slow charged.

Discharging is the same thing. Locate the weak cell and select for it and have a Digital LED simply display what it's doing. In this way you can filter out things you don't need to know.

Anyway, it is how I have been doing things lately. Back a long time ago I would just charge and go and not even bother to look. Doing that meant regularly replacing cells abused and no longer useful.

I like your idea you could just use 5-6s rc voltage readers on your balance leads and charge or discharge the specific 1s that is low to charge or high to discharge.

https://dirtcheaprc.com/shop/cell-check-2s-6s-lipo-liion-limn-life-cell-voltage-reader/
https://www.ebay.com/itm/275055427833?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=275055427833&targetid=4580496732614415&device=c&mktype=&googleloc=&poi=&campaignid=418233788&mkgroupid=1230353745471221&rlsatarget=pla-4580496732614415&abcId=9300542&merchantid=51291&msclkid=65e4406a7abd1282e79121be87e9bb66
https://www.ebay.com/itm/383174368082?_trkparms=ispr%3D1&hash=item5936f8db52:g:qKkAAOSwkAldi-5V&amdata=enc%3AAQAGAAACkPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsSQuF9OYLb3wphIAOfpJK8RtpAiuiuyMJpdjFAU4Jx%252Bt6jUqclhY1tsgwbTGXyQ7cscIG59JBn093xdlpysCTm4onVb%252Fljs9xGTuQ1ngtRxNqMN4ulbZCcu2s5MFgmyKR%252FcxF0djdzEyWKSQDWMebcjc6E9zqMr04lyYQhi58LlKQIvkxKFkgAWaIrUHyfSlcoEPEDj2epI2cIrHUUypQeAjJ%252F5C1IZlUaQfMNtyOBaZiXKqrXRlcruOf%252F%252FZC%252BU6Ygxkg%252FV2PwfzUzW1utqhtpwM8lS2YcQLkgSPyNh7YdW3SMcL8jAZij4lVHa4D2D6OrtUc1Ryw7YG%252FLbGXZXYprNMFR%252FklwsinIR3DuxT1vQwQoyVEQgrDnbaoB4DDlpJHrkWA8JB4B2U2gu0H74UgbYtgVrZL%252Fm5ninQwqrwXa8qgTIuiFHOXqiNEVUw5jI0lMgJkTpG7vhHk03m5VSid01p9c7amV0u3oLuyPkWEBw3Q0iTrMw5qaZkSLbXC05ihXIzylvXFuF%252Bw5BEDcvsxf3jd50pGCpd3RJAlS2GJY79vyNj2mb6yYCKxUtjBOYZwSyMMAKhG9IUsfyE7m23FXPD5DavyEzlLHfIfNvFNmqOsT4gsPFirFk5Bp50VmrlW4H6VrV%252FnpTQksJQD0EzhLFz242XLdjd4nmDrDaCjzX2Y8kfpm3CnAk1GreNicALdtsq2fF4%252BXxP6OoXOrkA428Lhqn4tyzCuB4wUg%252Fy66rDURfwKuS04ZGHewRp7ne8ZJUQF%252FyyzDY10wfzn951aW5gMOIB%252BUklQbPW8kR6MC4S3xr6sLslpcCskEZ1rRwdfQ%7Cclp%3A2334524%7Ctkp%3ABFBMzvjw_8Rf

Now this is very funny... I actually started this way of thinking doing exactly that.

I own the Black boxes in the second link that "attempts" to do balancing.

They do not work well at least mine were way off.

The problem with having multiple voltage testing paths is that each one might be slightly different as far as resistance. So you think everything is balanced but then when you actually independently test each cell they are way off.

My next evolutionary step was to physically provide actual individual cell XT-60 connectors external to the battery and I use those on one battery now. It's a bit goofy having in this case a dozen externally open XT-60 connectors but it works.

So my next thought was the Rotary Switch. That made certain the cells were being measured the same because I use the same form of measuring device on the output.

I have found that the drift in voltage reading can introduce a huge amount of errors which you might never know is there.

And I've gotten so I just assume the cheap Chinese stuff is junk. So I build most everything myself.

With the "old school" idea of a physical Rotary Switch it's bullet proof... there is nothing to break.

And one other thought... there is a simplicity to Power, Measurement and Rotary Switch. Just three elements. Uncluttered.

You want to go to 20S ?

Then you need to go to 3 Pole and 11 Positions and you would need to read the measurements of two cells at a time.

So "Off" is position one and then ten sets of two to reach 20.

One frustrating thing is 12S is a nice pack size, but that's just too many for the standard Rotary Switches.

However... if you look around you can find some oddball old military hardware from various places which sometimes goes beyond 11 positions.

If it helps, there are a few 12-position 2-pole rotary switches available. I didn't dig deeply into any of it, but a quick google and found Newark carries some, assuming their specs are accurate.
https://www.newark.com/electroswitch/d4c0212n/switch-rotary-dp12t-1-5a-115v/dp/06M4639

This one is "sealed" so might be better for on-bike applications
https://www.newark.com/electroswitch/c4d0212n-a/switch-rotary-dp12t-500ma-125v/dp/06M4594
https://www.newark.com/nsf-controls/mxd2-2x12-u/switch-2pole-12-pos/dp/02M4880

or this for higher currents
https://www.newark.com/ohmite/212-12t2/rotary-switch-2-pole-20a-150vac/dp/23C0768


They also show one 17-position 2-pole:
https://www.newark.com/electroswitch/d8g0217n/switch-rotary-dp17t-2-25a-115v/dp/06M4690

Other distributors probably also have some.

If you had the need and could afford it, (not for this purpose, I assume ) you could even have them custom made by some of the manufacturers.

11 position switch looks like a problem waiting to happen. I've also had a lot of problems with bms. I prefer balance wires and a balance charger when needed if needed. Use high-quality cells.

amberwolf said:

If it helps, there are a few 12-position 2-pole rotary switches available. I didn't dig deeply into any of it, but a quick google and found Newark carries some, assuming their specs are accurate.
https://www.newark.com/electroswitch/d4c0212n/switch-rotary-dp12t-1-5a-115v/dp/06M4639

This one is "sealed" so might be better for on-bike applications
https://www.newark.com/electroswitch/c4d0212n-a/switch-rotary-dp12t-500ma-125v/dp/06M4594
https://www.newark.com/nsf-controls/mxd2-2x12-u/switch-2pole-12-pos/dp/02M4880

or this for higher currents
https://www.newark.com/ohmite/212-12t2/rotary-switch-2-pole-20a-150vac/dp/23C0768


They also show one 17-position 2-pole:
https://www.newark.com/electroswitch/d8g0217n/switch-rotary-dp17t-2-25a-115v/dp/06M4690

Other distributors probably also have some.

If you had the need and could afford it, (not for this purpose, I assume ) you could even have them custom made by some of the manufacturers.

Click to expand...

Wow... you are good at finding stuff. Thanks.

999zip999 said:

11 position switch looks like a problem waiting to happen. I've also had a lot of problems with bms. I prefer balance wires and a balance charger when needed if needed. Use high-quality cells.

Click to expand...

Why? The "old school" television used a Rotary Switch.

Do you hate Black and White television? Just kidding. The old rotary switches could last forever.

The whole thing was "Break Before Make" so there were no big voltage spikes as you went through the dial.

SafeDiscDancing said:

Wow... you are good at finding stuff. Thanks.

Click to expand...

I usually am, yes. No problem.

The hardest thing about finding stuff is knowing what terms to use. The more searches you make for something the more you see certain common words in the ones you do find, and then you can start using those specific words to find more of them, and it gets easier from there.

When you have no idea where to start, sometimes just doing a google image search using a picture of the thing you want can help you find the first one, at least, and then go from there if they have a useful name on it.

SafeDiscDancing said:

The old rotary switches could last forever.

Click to expand...

I don't use it much (mostly for things where I need to watch the measurement change), but I have an early-20th century (20's? 30's?) Simpson multimeter that still works perfectly, using a multipole rotary switch....
https://endless-sphere.com/forums/viewtopic.php?f=1&t=97283&p=1425090&hilit=simpson+meter#p1425090
https://endless-sphere.com/forums/viewtopic.php?f=1&t=49550&p=1245554&hilit=simpson+meter#p1245554

Caution.

Watch out for "Make Before Break" products.

You cannot use them for this... skip down below to this one:

https://www.ebay.com/itm/CTS-2-Deck-Single-Pole-12-Pos-Rotary-Switches-Crosses-to-C3-Series-Electroswitch/191800885706?pageci=65ae10eb-de48-4906-ab38-fa6030e5267a&redirect=mobile

My plan is to just run the per-cell/group leads to the outside.

Deutsch connectors, very weather resistant, up to 12-pin use multiple can do as many as you want.

Just for balancing can use 14 AWG or so, can use a BMS, dedicated balancer, hobby charger owhateverr

OR, crazy thought, do not do your xPyS connections intra-pack at all, use heavier gauge wire for per-cell no grouping internally and

bring them to an external Harness Box, power leads only exit from that not the pack

which can be swapped out, so change from

A. 7P20S

B. 14P10S

... Any layout you like without opening the case enclosing your cells.

or Z. 1S - all 140 cells in parallel for MBM (I like that), balancing at whatever voltage, top bottom or middle.

This last becomes more practical using fewer higher Ah capacity cells

john61ct said:

OR, crazy thought, do not do your xPyS connections intra-pack at all, use heavier gauge wire for per-cell no grouping internally and

bring them to an external Harness Box, power leads only exit from that not the pack

which can be swapped out, so change from

A. 7P20S

B. 14P10S

... Any layout you like without opening the case enclosing your cells.

Click to expand...

I did that once using XT-60 for each output point. My suggestion would be to use the bigger XT-90 and make sure they are of the shell casing "outer" type not the flexible "inner". Why? Because once I accidentally shorted the "inner" type using a voltmeter and it weakened the connector.

If you use the "outer" shell casing anything stuck in there is electrically isolated.

(like in the picture at the start of this thread... those are "outer" shell XT-60 which I guess are "female")

Another problem is you just get tired of plugging and unplugging so many connectors over and over for each charge.

With the XT-90 (Power), XT-60 (Measure) and the Rotary Switch you can ignore the balancing most of the time and just do a quick check every once and a while. I find once you accurately get things where you want them there is next to no drift between cells. Now obviously there are really poorly crafted packs that drift wildly, but I haven't dealt with those myself.

https://www.ebay.com/itm/CTS-2-Deck-Single-Pole-12-Pos-Rotary-Switches-Crosses-to-C3-Series-Electroswitch/191800885706?pageci=65ae10eb-de48-4906-ab38-fa6030e5267a&redirect=mobile

I erased the previous listing because it was "Make Before Break" and that is what you must avoid.

This is $10 and has two sets of 1 pole and 12 positions running in parallel.

The wiring would be a little different.

USA seller.

-------------------

https://www.ebay.com/itm/Oak-Switch-399-611-L-Non-Shorting-2-Pole-2-Sec-2-17-Pos-Rotary-Switch-NOS/313816639889?hash=item4910ede991:g:IUQAAOSwlQNfyDTl&pageci=8ae12145-ed17-40d5-a966-85f4c4659b5f&redirect=mobile

2 poles and up to 17 positions (so 16S pack) for about $21.

-------------------

Another idea would be to buy a "Make Before Break" rotary switch which is available up to 24 positions (only $13) then take it apart and grind the connector to convert it to "Break Before Make".

The only difference is the width of the slider which does the electrical contact.

This is the kind of crazy stuff I love fiddling around with... okay... strange... yes.

How can you tell if its a make before break or break before make most listings I searched for dont mention anything like that.
https://www.ebay.com/itm/CTS-2-Deck-Single-Pole-12-Pos-Rotary-Switches-Crosses-to-C3-Series-Electroswitch/191800885706?pageci=65ae10eb-de48-4906-ab38-fa6030e5267a&redirect=mobile

Non-Shorting Silver Plater Terminals and Contacts

Click to expand...

https://www.ebay.com/itm/Oak-Switch-399-611-L-Non-Shorting-2-Pole-2-Sec-2-17-Pos-Rotary-Switch-NOS/313816639889?hash=item4910ede991:g:IUQAAOSwlQNfyDTl&pageci=8ae12145-ed17-40d5-a966-85f4c4659b5f&redirect=mobile
in title and description

Non-Shorting

Click to expand...

The point is the seller must be wise in knowing and list it which will be the rare seller so you need to put it in the search term which I never have much luck with. I just looked at some retail outlets online, non shorting would be break before make?

calab

Click to expand...

Ebay is the low end for a lot of stuff.

Cheap. Often not very good. And many times it's hard to find exactly what you want.

But on the bigger electronics sites they can be so extremely expensive as to make you rule out the idea.

Basically the Rotary Switch is WW2 era technology. It's stuff designed to withstand military type abuse and that's the attraction of it because the stuff we see is all designed to break in a planned obsolence kind of way. Reliability matters because I like to ride a lot and tend to put on thousands of miles on my ebikes. And things do still always break anyway because I'm always pushing it hard.

Every once in a while I see an old Russian military switch with 2 poles and 16 or so positions for sale for $10 on Ebay.

Probably the easiest idea is to buy a 24 position "Make Before Break" and just modify it... that's what I was saying a post ago... the only real difference internally is the width of the contact slider. If you took it apart you could grind down the slider and make it into a "Break Before Make". (just be sure to test it carefully afterwards)

Up to an 11S pack and you can buy a rotary switch for $5 which is what I did on the battery pictured here.

And the idea of two measurements at a time isn't bad either. So a 20S pack can be checked by only rotating through ten positions. Obviously a 12S pack could be checked in just six clicks.

Seems like people these days prefer the smartphone type virtual reality experience and like the gadgets... which then break on them.

SafeDiscDancing said:

Basically the Rotary Switch is WW2 era technology.

Click to expand...

More like pre-WW1!

Seems like people these days prefer the smartphone type virtual reality experience and like the gadgets... which then break on them.

Click to expand...

If I had the roundtuitiveness, and the budget for the tools and materials and parts, my SB Cruiser trike would have a "dashboard" and "console" that would remind people of an early-mid-20th century airplane cockpit. I'd have to custom make a number of things (like most of the handlebar controls), since I've never seen anything like what I'm after (a few plastic ones resemble parts of it, but they're plastic...I want metal!).

Dials and gauges and toggles and flipcovers oh my!

amberwolf

Click to expand...

How about this one?

JEANRENAUD is a Vintage well-known French manufacturer of switches. In 1974 ITT Industries acquired Jeanrenaud and Rudolf Schadow and later these companies formed C&K Components.
JeanRenaud switches were very often used in High-End Audio and Video recording equipment, especially in NEVE 80-series analogue mixing consoles and modules.
Total Body Size, including shaft, not including leads (Diam x Height): 17 x 37 mm = 0.67 x 1.45 inch
Diameter with leads: 20mm = 0.78 inch
Shaft (Diam x Length) = 6 x 5 mm = 0.24 x 0.20 inch

2 pole, 12 throw --> 12 positions
This is a NON-SHORTING (Break-Before-Make) switch.
Rated at: 100V, 0.5A (500mA), 5W

Condition - NEW.
The price is for ONE piece.

Worldwide Shipment: $6.00 (Ebay price $6.80)

https://www.ebay.com/itm/Rotary-Switch-JEANRENAUD-C-K-2P12T-2-pole-12-position-NON-Shorting-BBM-NEVE-80xx/254881081409?pageci=f32fc44f-6fd8-434b-bd54-519beb8f65ef&redirect=mobile

That has a very elegant style.