A123 AMP20M1HD-A Battery pack kit

[arkmundi]

I have played with those A123 cells with high discharging and then charging again and must say even Icharger was having problems keeping them in balance. Personally, i would not go BMSless route myself after seeing these cells drifting a lot. BMS or balance charger is the way to go.

Thanks for the recommendation. So what's the range you've seen? What exactly is an unbalanced AMP20 cell? My cells are all testing in the range of 3.3 to 3.4 volts. Is 0.1V out of balance? 0.2V? 0.5V? What's the impact of an unbalanced cell on battery performance? I

[agniusm]

my iCharger was charging 6S pack, all voltages at 3.3, one cell shoots to 3.65. I dont know if it's a charger cause it broke recently or cells behaving like that. Anyway, i have cellman's bms and it works wanders. I mean whats the point in not having one?? I build my scooter with built in charger so i just plug in 220V and forget about it. Always have charging lead with me so i can top up if needed. My view on e transportation is that it has to be hassle free, no oil change, no filters, plug and play as they say. This is why i don't understand why people have their packs in the back pack and hobby chargers at home which takes some effort to charge. This is my thingy charging:

To me BMS makes a lot of sense and i wouldn't go without. Cells cost a lot not to look after them

[docnjoj]

Absolutely true, agniusm. I am only using the Hyperion because I wanted to try out having the BMS off the bike. I have kfongs lvc (set for 3 volts at this moment) on the trike and I normally use Pings BMS, but the Cellman one may be better. I think it is worth the try. So far my cells all balance at 3.60 with variations on the third decimal place. I think this is good enough with the Hyperion.
otherDoc

[megacycle]

I have played with those A123 cells with high discharging and then charging again and must say even Icharger was having problems keeping them in balance. Personally, i would not go BMSless route myself after seeing these cells drifting a lot. BMS or balance charger is the way to go.

Thanks for the recommendation. So what's the range you've seen? What exactly is an unbalanced AMP20 cell? My cells are all testing in the range of 3.3 to 3.4 volts. Is 0.1V out of balance? 0.2V? 0.5V? What's the impact of an unbalanced cell on battery performance? I

There's s few threads on them a few offerings;-
http://www.google.com/search?tbm=isch&s ... h=1280#i=5
http://endless-sphere.com/forums/viewto ... &start=165
They'res a few graphs etc work on IR and impedance too, which I think is really relevant.
They seem to live in the band around 3.0 to around 3.4 ish above that its like surface change pumping them up the 3.6ish think it's just a pain and waste if your bms is resistive, soon after they're down to like 3.3 to 3.3ish anyhow, Im reckoning gonna live longer too.
I'm gonna get mine up to say 3.4ish and terminate

[999zip999]

Mega Right at 3.3v. done lower than that no power. They live at 3.4v and to 3.6v is a .5ah of fluff. !7.99ah one test and one test only. !420 to 3.59v

[arkmundi]

Mega Right at 3.3v. done lower than that no power. They live at 3.4v and to 3.6v is a .5ah of fluff.

I believe we have the discovery of a new phenomena that should delight and boogle the mind of the modern physicists: li-ion nanophosphate electron fluff, defined as the ionic excess held in an electrolyte beyond its physcial capacitance.

[megacycle]

The froth on a beer sounds good too
Was just knocking the top off an iconic beer and had an epiphany aahhh.
Best be off to the late night beer thread Cheers.

[arkmundi]

Dear Agniusm and all - my last post on this thread. Many thanks for making this forum honest and relevant to life! Specially docnjoj, deVries, ohzee, 999zip999, and megacycle, for responding in real time and keeping it real. Most importantly to the engineer himself - congrats on your wedding, the beautiful bride, and this other love affair! Anyone interested in Arkmundi's saga in making an A123 AMP20 battery can pick up the story here: http://endless-sphere.com/forums/viewtopic.php?f=14&t=42871, with latest photos. Also of interest to the crowd here, will be a Construction manual on the complete build, including the balance-of-system. Tat-tat!

[teklektik]

I just bought one of these and will test out in thes scenario:
https://p10.secure.hostingprod.com/@www.voltphreaks.com/ssl/catalog/product_info.php?products_id=28
Single cell chargers for LiFePO4 batteries. These are constant current constant voltage (CCCV) chargers for 3.2V LiFe batteries. Max charging current of 2 amps.
CCCV to 3.65V,
AC input: 100-240V/50~60Hz 0.35A MAX

These VoltPhreaks chargers are well known on the forum and work nicely albeit slowly at only 2A. I use a flock of them to charge 20Ah of Headways overnight. 100+ cycles so far. They will, however, overheat if passively cooled and placed side-by-side without an intervening air space (e.g. use every other socket on power strip).

[sergio helder]

hello everyone. im new to the forum and i would like your opinion on this.
im planning of building a 12s (36V 20A) pack and i was thinking what would be better. i can get a BMS AND A LIPO CHARGER to go with the cells .or instead, just one charger with pre installed balancer to charge then. will be using a 500w hub im not pushing the battery more then 20 A so im not expecting any dramatic balance problem on the cells after use.
thanks, really would like to hear your opinion on this.

Agniusm did you consider making the spacer for the to boards in plastic. i supose they would come out less expensive and serve the purpose all of the same.
congratulations to everyone. From Portugal this is Sérgio

[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....