The care and feeding of a123-based packs...

[scoot]

hi there , do i need a bms for a 6sp2 A123 pack because i want to add it to my lipo pack for some more range , i know i can use balancer and then charge but some people
say that more you have cell more I have chance to destroy the cell with out a proper balancing , but what is the maximum we can use with out a lvc or bms ?

thank you

I think that last thing you want to do is parallel connect a Lipo and Life pack together for extended range. They have have significanlly different voltage profiles when charging and discharging. Unless you have more info that you have yet to provide as to why you are contemplating this approach, I would steer clear of considering it.

 

[lifepo4ever]

oooh sorry i want add in series not in parallel and I never say i will charge them together with lipo only thing you have to figure it out is the capacity and my lipo pack is
10ah and i will add to my 50v lipo pack 2 x 6sp2 anyway my question not solve do i really need lvc or bms for this small pack ?

 

[scoot]

Adding extra cells or another pack in series is not the typical approach for increasing range.

Connecting another 6s Life pack in series with your Lipo pack will increase your overall voltage by 20 volts or more, hence your motor speed. Your overall capacity and range will be limited by the smaller of the two packs. If the two packs were roughly the same capacity, then the only way you might achieve some more range with that kind of mod is to modulate the acceleration and motor speed to the same level as before you added the extra pack. All of the usual protection and balancing principles would apply IMO.... independant of the cell count for a given pack.

 

[ramboman]

This is a nonsense...
Mixing different chemistries...
Build a full a123 pack and you get it!
More in parallel to increase range...

 

[scoot]

This is a nonsense...
Mixing different chemistries...
Build a full a123 pack and you get it!
More in parallel to increase range...

The short (best) answer :wink:

 

[The Mighty Volt]

My original question was not about an increase in range it was about an increase in power to allow an PREDOMINANTLY A123 pack {23Ah..is that one of the biggest on ES?} be coupled with a small booster pack of LIPO so I could swap over to Lyens power controller and enjoy some sprints.

 

[texaspyro]

I have a PITA standing around trying to charge A123 via the CV method, where the voltage is set to 3.6v from my power supply, and then observe as the current drawn by the battery decreases, until it eventually hits 0.01A, CV. At that point it is, in my opinion, fully charged.

However, it is taking an age to move from 0.10A to 0.01A, 3.6v CV. So, I ask, what is the difference in SOC at these values? Is it so insignificant, as I can safely connect these batteries in parallel without suffering any damage to the lesser charged cells?

Check out the first post in my A123 capacity/charging thread: http://endless-sphere.com/forums/viewtopic.php?f=14&t=20698&start=0#p301558


I charged some A123 cells with a CC/CV charger (constant current/constant voltage). The CC phase was set at 6 amps. With the 2300 mAh cells, the cells would ideally fully charge in 23 minutes, but the chemistry does not allow that. At 18 minutes the charger started the CV phase where the pack voltage remains constant and the charge current drops. It took another 18 minutes to reach the recommended cutoff current of 50 mA.

So just how much extra capacity does one gain in the final CV charge phase. A fully CV/CC charged cell had 2305 mAh capacity. The same cell that was charged for only the 18 minute CC phase had 2093 mAh. You gain around 9% capacity from the final CV phase (that takes as long as the constant current phase).

 

[Doctorbass]

I have a PITA standing around trying to charge A123 via the CV method, where the voltage is set to 3.6v from my power supply, and then observe as the current drawn by the battery decreases, until it eventually hits 0.01A, CV. At that point it is, in my opinion, fully charged.

However, it is taking an age to move from 0.10A to 0.01A, 3.6v CV. So, I ask, what is the difference in SOC at these values? Is it so insignificant, as I can safely connect these batteries in parallel without suffering any damage to the lesser charged cells?

Check out the first post in my A123 capacity/charging thread: http://endless-sphere.com/forums/viewtopic.php?f=14&t=20698&start=0#p301558


I charged some A123 cells with a CC/CV charger (constant current/constant voltage). The CC phase was set at 6 amps. With the 2300 mAh cells, the cells would ideally fully charge in 23 minutes, but the chemistry does not allow that. At 18 minutes the charger started the CV phase where the pack voltage remains constant and the charge current drops. It took another 18 minutes to reach the recommended cutoff current of 50 mA.

So just how much extra capacity does one gain in the final CV charge phase. A fully CV/CC charged cell had 2305 mAh capacity. The same cell that was charged for only the 18 minute CC phase had 2093 mAh. You gain around 9% capacity from the final CV phase (that takes as long as the constant current phase).

Yes.. But after many discharge cell tests i did.. i can say that the last CV stage depend ALOT on the accuracy of the voltage reading of the charger/power supply and wire you use!!

That time for the CV decrease if you use a Kelvin ( 4 wire sensing method) to connect the cell to the charger.. so the V loss in the wires is bypassed and the charger can finally see the REAL voltage of the cell... not the voltage at the end of wires that vary too much with current that pass thru them..

Kelvin is ideal because the current pass thru a pair of wire and the voltage reading pass thru a different pair of wires.. making the voltage reading not affected by the voltage loss in the current carying wires.

The charger use the voltage reading of that cell to determine the point where it start the CV stage... so the more accurate the cahrger read it the longer you will keep that CC stage and shorten the charging time!

Some explanations:
http://en.wikipedia.org/wiki/Four-terminal_sensing

And exemple when charging with DC-DC for individual 3.6V cell charger:

Tested... and Working ! :wink:

Doc
:wink: :wink:

 

[texaspyro]

Yes.. But after many discharge cell tests i did.. i can say that the last CV stage depend ALOT on the accuracy of the voltage reading of the charger/power supply and wire you use!!

Actually this test is rather non-sensitive to most of those conditions. Once the cell reaches the CV point, the charge current drops rapidly. The lower current means lower voltage drops in the cabling and less error due to IR losses. I did my tests with the battery clipped to the power supply via 8 inches or so of 10 gauge wire... total resistance was less than 0.005 ohms. At full charge current that was under 30 millivolts of maximum possible error. By the time the cell reaches full, the cable losses are in the microvolts, even with long leads.

What does make a large difference in charge time is the charger voltage. I ran several tests to see battery capacity at various charge voltages. Once you got below about 3.5V, the charge times went up dramatically. Trying to charge to the CV point at 3.3V took all day. Even with long, skinny leads you will eventually get to the CV point. It may take a long time...

If you are charging at high currents, you really want to do remote sensing of the voltage at the end of the leads, not at the power supply.

 

[lifepo4ever]

i was asking if a need a lvc or bms on a 6sp2 a123 pack I know what is series and parallell is 10 years ago !! and what its the problem using a123 and lipo ? at the same time , if i use the same capacity as my lipo I should not have problem ?

 

[The Mighty Volt]

@TexasPyro and @Docbass: Many thanks for those two replies. Cheers.

 

[The Mighty Volt]

Good for 100Amps???

Above is a 1s10p sub-pack of A123, tabbed cells, finished with copper wire and shim.

What I now need to do now is terminate the pack so I can join them up in series. I got some female and male spade-ends from a friendly ES member and they seem to fit well into 9AWG wire. {6mm2 European, its around 9-10 AWG}

It should be noted that the sub-pack is already connected with suitably heavy and conductive materials.

These spade-ends and the length of wire are only needed to terminate each sub-pack. I was wondering what people thought about the Spade-Ends and their ability to handle long bursts of 100A peak.

Lyen thinks they are good to go, and sure enough he uses them on his controllers, I just thought I would throw it out there and see what everyone else feels. Thanks.

 

[TMaster]

and what its the problem using a123 and lipo ? at the same time , if i use the same capacity as my lipo I should not have problem ?

I don't think mixing chemistries and different C ratings into the same circuit is a good idea...

 

[lifepo4ever]

hey Mighty Volt !! you want to build a monster pack ? 23 ah capacity where you want to put these cells ?

i have some a123 cells left here and i want to build a 50 volt 9.2 ah i have 50volt charger here that why i made smaller pack so if want to charge i need to bring one charger so 5sp4 for each pack with balance plug , give me 54volt full charge but the charger can only charge at 51 so 80% capacity or maybe a 5sp5 will be better for capacity anyway this is spare pack i will use when my 24s lipo pack is empty , i can also split lipo my pack to run 50 volt 10ah , so 2 pack of lipo 10 ah and 2 pack of A123 10ah for a total of 40ah at 50volt! not so bad !! , i want also build some rack on the front of the bike so i can remove quickly and bring inside to recharge them , i am little bit tired to bring the bike inside the kitchen .

 

[The Mighty Volt]

hey Mighty Volt !! you want to build a monster pack ? 23 ah capacity where you want to put these cells ?

i have some a123 cells left here and i want to build a 50 volt 9.2 ah i have 50volt charger here that why i made smaller pack so if want to charge i need to bring one charger so 5sp4 for each pack with balance plug , give me 54volt full charge but the charger can only charge at 51 so 80% capacity or maybe a 5sp5 will be better for capacity anyway this is spare pack i will use when my 24s lipo pack is empty , i can also split lipo my pack to run 50 volt 10ah , so 2 pack of lipo 10 ah and 2 pack of A123 10ah for a total of 40ah at 50volt! not so bad !! , i want also build some rack on the front of the bike so i can remove quickly and bring inside to recharge them , i am little bit tired to bring the bike inside the kitchen .

The idea of the 23Ah pack is to make the cells last longer and also to allow for longer journeys and higher potential amperage. Bigger packs need to be charged less often, so this provides me with an opportunity to extend the life of the cells. Also where is the fun if you have to put your bike back on charge every few minutes......

 

[lifepo4ever]

I don't say its not great idea to have a big pack but a123 are heavy and take lot of space then lipo , you just have more patience then me

 

[The Mighty Volt]

I don't say its not great idea to have a big pack but a123 are heavy and take lot of space then lipo , you just have more patience then me

 

[The Mighty Volt]

What is the story with using 18650 sub-packs {18650 cells only} and 26650 sub-packs {26650 cells only} in conjunction with one another as individual, identically sized sub-packs which make up a larger overall build?

I understand that the 18650 cells are rated for 30A continuous, but in a 20o string they should be good for 100amps continuous, correct? So the discharge discrepancy issues should really become an irrelevancy once we move beyond 4p or 5p??

I have seen a gentleman called Steve Ali Labib does this, except he takes it one step further and combines Life-Batt sub-packs with A123 26650 sub-packs!!!

[youtube]InVkkSySyA[/youtube]http://www.youtube.com/watch?v=_InVkkSySyA

 

[hillzofvalp]

practical solution to charging/balancing a 14s5p pack (with hyperion 1420i)? does anyone have a source for a 14s BMS and LVC?

Thanks! 8)

 

[micart671]

Hi, great thread with plenty of good info.
I couldn't see photo's though??

A couple of questions;
*What's stopping you using the packs as they are with four battery pack mounts in parallel on your trusty treadly?
*How do you know you're getting genuine product? Can products from China be trusted?

 

[ramboman]

To charge and balance 14s5p... I do the following for 14s3p...
- either MasTech 5020i set to max... 50V 20A (no balance)
- or two iCharger 3010B set to 7s3p each at 30A (no balance)
- balance once a month to check...

 

[crusoe]

Can the original author of this thread repost the pictures of the disassembly of the dewalt packs? Greatly appreciated!

 

[BShady]

Can the original author of this thread repost the pictures of the disassembly of the dewalt packs? Greatly appreciated!

yup, pictures would be greatly appreciated.
thanks

 

[ambroseliao]

Can the original author of this thread repost the pictures of the disassembly of the dewalt packs? Greatly appreciated!

Unlikely. Gary isn't active on this board anymore.