A123 AMP20M1HD-A Battery pack kit

[docnjoj]

Well Sergio welcome! You probably don't need both a BMS and a balance charger. A good BMS like Cellmans or Pings or the European one agniusm is using will work with a good charger. Or you can get a good charger like a Hyperion and use that . You then have only to keep track of your LVC with a meter, or use Kfongs LVC or Methods HVC/LVC. Using both is probably overkill.
otherDoc

[tome]

A good BMS like Cellmans or Pings or the European one agniusm is using will work with a good charger.
otherDoc

Do I understand correctly that a BMS can somehow "disconnect" a cell within a pack if that cell's voltage goes too low during discharge (load)? If so, how does it do this? I thought there was a single wire tied to the top ( +) of each cell that ran to the bms and allows the bms to sink some current in order to drain a cell down a bit during charging in order to balance cells. That makes sense to me, but I read somewhere that it can also keep a low cell from being drawn down during discharge and I don't see how that is possible with only a small wire that can only handle 2-3A...

Tom

[ohzee]

it just cuts power to whatever the BMS is plugged into so it can not be drawn any lower.

It stops them from being charged to high by cutting power from the charger and to low by cutting power to the controller

[megacycle]

Depending upon how they work, there's a few different designs and myself have little experience of them yet till I finish my A123 packs, as Im running lipo without at the moment.
They can current shunt around cells that are dropping as Fetchers design or as per Ohzee and myself have sourced capacitor bms's, thanks to Michael at evassemble, these shuffle charge between cells to keep them equal.
Michael is active on this thread and am sure he could elaborate more
Added His are specified for this application.

Edit; I think there are quite a few as Ohzee states that cut power when the first cell reaches lvc.
Personally I would like mine to balance top and bottom.

[sergio helder]

thanks for the answer docnjoj. one other thing, could someone tell the normal/best specs for overvoltage/undervoltage protection, so i can setup my bms.

[arkmundi]

A good BMS like Cellmans or Pings or the European one agniusm is using will work with a good charger.
otherDoc

Do I understand correctly that a BMS can somehow "disconnect" a cell within a pack if that cell's voltage goes too low during discharge (load)? If so, how does it do this? I thought there was a single wire tied to the top ( +) of each cell that ran to the bms and allows the bms to sink some current in order to drain a cell down a bit during charging in order to balance cells. That makes sense to me, but I read somewhere that it can also keep a low cell from being drawn down during discharge and I don't see how that is possible with only a small wire that can only handle 2-3A...

Tom

We have to understand there are a lot of approaches to doing "battery management," many different devices that can be applied. Of course if there is a computer chip and programming in the circuitry, then the management has been delegated. The other approach, the one I'm using for now is to use the power of my own brain. Doing so requires good information. Hence, my choice is to introduce the "Watt's Up" meter:

"Watt's Up" & "Doc Wattson" Watt Meter and Power Analyzer User's Manual. RC Electronics, Inc.
10.5 Balancing Battery Pack Cells. You don't want battery pack cells going below their minimum safe voltages for safety and battery life reasons. A battery pack whose individual cells are all balanced delivers the most energy since all cells are exhausted at the same minimum voltage. If any cell is "out of balance" it may reach the minimum safe voltage before the others and continued pack discharge will damage the cell.

Its the differential uptake of charge during the charging cycle that I feel warrants concern. The Watt's Up meter gives me ongoing real-time performance information, telling me when to turn the battery off during use. But it also tells me the charge status after a full charge. I can use this information to gauge the overall health of the battery. When I see degradation, I can then check each cell individually to see the different voltages of the cells. If there's a low one, I can then apply my 2 amp Voltphreaks charger to just that cell and bring it back up, if it wants to. If a cell persists in dangerously low voltage despite attempts to charge it, it time for replacement.

The beauty of Agniusm's kit, in part, is that it also makes deconstruction easy. That way the individual cells can be pulled out or reordered. I believe the placement of the cells in the pack may influence their relative charge/discharge, so simply changing the order of the cells may improve the battery's overall performance; swapping inside to outside, near the poles, for instance.

Its an ongoing experiment. For now, my pack holds charge beautifully, I have the data I need, and I require nothing more. This state may persist for years, before I need to intervene. I hope so.

[megacycle]

Each chemistry appears to have its own rules with the lipo flightmax using presently I pump them up at up to 3C close to 50A and with the cellogs watch them climb reasonably together and in about 20 mins close to about 50mV out worst case, I use a combo of another charger to charge 1-3 cells group and a 10W resistor to get about 30 - 40mV out

I tried similar with a 8S A123 pouch pack pumping about 3-4C, 60/ 80A in, I couldn't keep up with the the out of balance with a manual method.

I suppose if you columb count with energy and watt meters CA, powerlog 6S which is similar in watt meter function but does a lot more, as you mention be a good method to know when your packs close to full or empty, if you know the SOC at start, but this chemistry tends to have larger fluctuating cell values near the walls. I had some trying to get to 4.0 when others were less than 3.5
Single cell chargers would be good Yeh would be good to do a whole pack and no worries.
Would love little 80A singles for onboard be great.
My first pack had a switch so could parallel all cells together to kinda instant balance as I got to the wall with a couple and switch back to series but it was still work to keep them together.
I think these cells can take abuse and maybe going to 4.0V with some might not be too much of an issue as the surface charge is removed and there all down to 3.33V again.

[agniusm]

Hello. Have done couple of tests on A123 cells yesterday. Before the test some relaxing:

...and here is a glimpse on aftermath:






Video coming up...

[ohzee]

Holy crap that's a nice swing.. That water pretty deep there ? Looks pretty awesome you build that contraption ?
Can I come live with you for a while ? looks like such a pretty place.

[agniusm]

Holy crap that's a nice swing.. That water pretty deep there ? Looks pretty awesome you build that contraption ?
Can I come live with you for a while ? looks like such a pretty place.

Don't know about living thou you can come visit in summer time. We have a cabin near the lake with some solar electricity to charge cellphone, have lights and some music
Me and my bro build that contraption. Was some job to get the steel work 22m up in the tree. Even quad didn't helped.

[njloof]

Adding to my list of places to visit before I die Might want to trim back that tree branch!

[tome]

[quote="arkmundi"]
We have to understand there are a lot of approaches to doing "battery management," many different devices that can be applied.
[quote]

Thanks for the replies, but I guess I didn't ask my question correctly, let me try again.

There are BMS's that (I think) claim to shunt current during the charge process in order to keep all cells charging whilst removing the ones at HVC (by shunting). To do this, you only need to bleed off a little current (2A or less) and so with a tap wire of, say 24AWG or so, I see how this is done. However, these BMS's also claim (I think) that they "remove" cells that have reached LVC from a pack during discharge. In my head it seems the only way to do that is for the entire pack current (potentially 100s of amps) to be passing through the BMS. The BMSes don't look like they are beefy enough for this to be the case, so I am wondering how do BMS work (how are they wired into the battery pack) that can protect a pack during the discharge phase?

Tom

[agniusm]

Here is that vid

[999zip999]

Fluff ? The voltage above 3.4v to the cutoff of my 1420 at 3.59v. Is true voltage. And charged to 3.65v is possible without harm. But charging above 3.59v as with my 1420 does is easy. But it will drop fast to 3.4v and stay there for many ah.. So how much good does it do to go higher than 3.5v. ? For long battery life ? How many ah are there up at a high voltage ? That's way I put out the ( fluff ) word. And to hear some kickback. At lease I didn't use fluffy. As this could have got me banned from E.S.

[sergio helder]

better ulpoad that vid again....

[agniusm]

better ulpoad that vid again....

Fixed!


Started assembling my cargo bike battery, still missing couple of cells. Here is my kit balancing connector wiring:

1. Prepare bits and peaces:




2. Put heat shrink tube on wires, solder wires. Note i am using two wires (BMS specific) and heat shrink and fits perfect:




3. The whole deal:

[Doctorbass]

Here is that vid

Agniusm were they charged or discharged when you did that test ?.. because it make a huge difference on the result!

Doc

[agniusm]

Charged, storage, 3,32V

[arkmundi]

Here is that vid

What the fracking cell^*&^*&^%! Before you destroy anymore, send them to me, please! OK already, the cells can take a lot of abuse without being hazardous. Is there some way to translate that into li-ion shipping policies? We're all going to pay an unnecessary premium for hazmat shipping it seems!

[megacycle]

We have to understand there are a lot of approaches to doing "battery management," many different devices that can be applied.

Thanks for the replies, but I guess I didn't ask my question correctly, let me try again.

There are BMS's that (I think) claim to shunt current during the charge process in order to keep all cells charging whilst removing the ones at HVC (by shunting). To do this, you only need to bleed off a little current (2A or less) and so with a tap wire of, say 24AWG or so, I see how this is done. However, these BMS's also claim (I think) that they "remove" cells that have reached LVC from a pack during discharge. In my head it seems the only way to do that is for the entire pack current (potentially 100s of amps) to be passing through the BMS. The BMSes don't look like they are beefy enough for this to be the case, so I am wondering how do BMS work (how are they wired into the battery pack) that can protect a pack during the discharge phase?

Tom

Hi Tom was hoping to find some information to aid in answering your question.
As Arkmundi was referring to, there's many different ways.
This area is like opening a can of worms and was looking it up too in relation to lifepo4 and so hope the information on this excellent site by Albert Van Dalen ( who I think has contributed to this site a fair bit too). http://www.avdweb.nl/solar-bike/electronics/bms.html

Everyone seems to have a different take on charge/discharge bms parameters etc.
In relation to resistive types seems for simple operation they bleed charge from the good cells to drop down with the cell that hit the lvc mark first, which should be the lowest capacity cell.
I'm hoping the capacitor bms that Ohzee and myself have bought might help give better capacity in this respect, but havnt tested them yet too busy building etc.
There was another ES thread relating mainly to bottom balancing quite a few knowledgeable people inputting viewtopic.php?f=14&t=27263&hilit=bottom+balancing
Must warn I had a headache afterwards

[whatever]

I'm a bit worried about the guy in the forest with shotgun and axe, seeming to enjoy a little bit too much destroying the cells....."oh yes'

[agniusm]

I'm a bit worried about the guy in the forest with shotgun and axe, seeming to enjoy a little bit too much destroying the cells....."oh yes'

Those cells were damaged, punctured and lost vacuum. Occasionaly everybody has to have some fun.

[tome]

Hi Tom was hoping to find some information to aid in answering your question.
As Arkmundi was referring to, there's many different ways.
This area is like opening a can of worms and was looking it up too in relation to lifepo4 and so hope the information on this excellent site by Albert Van Dalen ( who I think has contributed to this site a fair bit too). http://www.avdweb.nl/solar-bike/electronics/bms.html

Everyone seems to have a different take on charge/discharge bms parameters etc.
In relation to resistive types seems for simple operation they bleed charge from the good cells to drop down with the cell that hit the lvc mark first, which should be the lowest capacity cell.
I'm hoping the capacitor bms that Ohzee and myself have bought might help give better capacity in this respect, but havnt tested them yet too busy building etc.
There was another ES thread relating mainly to bottom balancing quite a few knowledgeable people inputting http://www.endless-sphere.com/forums/vi ... +balancing
Must warn I had a headache afterwards

Great! The links are exactly what I needed. Lots of good info in there including schematics and links off to other good sources of info from BMS chip makers.
Many thanks,
Tom

[999zip999]

The cell measure 2.8v before test and after test 3.3v. Great fast charge.

[megacycle]

Great! The links are exactly what I needed. Lots of good info in there including schematics and links off to other good sources of info from BMS chip makers.
Many thanks,
Tom

No worries bud, hope you were able to sort through it all,you'd be smarter than most, I still got a headache