Before I start building my pack I have three questions.

[gaisom]

I am going to be using 8s packs. 18650 Sanyo 2200ma cells

#1 Should I set them up as 4s packs and connect them in series for ease of balance charging and replacing bad cells?

#2 What size balance leads should I be using? max discharge C will be 2amps, and max Charge C of 1amp. I have found lots of conflicting info on this question.

#3 Where is a good place to get the Connectors I will need for the balance board connections using an icharger 1010B+ with the balance board that comes with it?

 

[dogman dan]

IMO, the typical balance leads on RC lipo packs can handle 1 amp.

So any supplier of jst extensions would provide wires connected to jst plugs. EP buddy, hobby king, etc etc.

I'm not certain what plug the charger uses though, so I could be wrong. I assume it's JST's.

I'd parallel first, then series the groups of paralleled cells.

 

[TwoWayStreet]

I am going to be using 8s packs. 18650 Sanyo 2200ma cells

#1 Should I set them up as 4s packs and connect them in series for ease of balance charging and replacing bad cells?

I would not. 8s is not that many. If your charger can not handle 8s, you can install two 4s balancing connectors instead of one 8s connector (of course you need to add one lead wire at the 4s intersection/boundary for charging.) By NOT doing two 4s packs, you minimize the number of connectors. Connectors - no matter how robust - always result in more voltage drop than normal/decent wires.

 

[dnmun]

I am going to be using 8s packs. 18650 Sanyo 2200ma cells

#1 Should I set them up as 4s packs and connect them in series for ease of balance charging and replacing bad cells?

#2 What size balance leads should I be using? max discharge C will be 2amps, and max Charge C of 1amp. I have found lots of conflicting info on this question.

#3 Where is a good place to get the Connectors I will need for the balance board connections using an icharger 1010B+ with the balance board that comes with it?

sorry to see another person going this way with laptop cells but to answer your question:

the sense wires to the JST plug do not have to carry much current if you are using the icharger since the balancing currents are only a few hundred mA.

just plugs and pins:
http://www.ebay.com/itm/150970096867?var=450148333804&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
http://www.ebay.com/itm/330832724191?var=540111397800&ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
http://www.ebay.com/itm/130720286593?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

i bot 9 pin JST plugs from this guy before: http://www.ebay.com/itm/JST-2-5-XH-12-Pin-Connector-Plug-w-Wire-x-5-sets-/111187487696?pt=LH_DefaultDomain_0&hash=item19e34a6bd0

 

[gaisom]

Thanks for the info. For some clarification on this :

sorry to see another person going this way with laptop cells but to answer your question:

I got the cells free, I live within 100yds of a 40+ miles of paved bike trail (old railroad grade) that has few hills of any note. I am very mechanically inclined (lifetime of repair of all different types of equip including Computers, Helicopters,Vehicles and one year of Electronics Tech training way back when we used slide rules " Side note (I got two questions wrong on a math test in high school using that slide rule because of the built in error factor)" I can't drive any more because I have lost 90% of my vision, so this is my "get out of the house project". So don't be sorry ok? I go into this with what remains of my eyes wide open and the gains far outweigh the possible losses.

Cheers!

Grant

 

[TwoWayStreet]

sorry to see another person going this way with laptop cells

Don't be sorry for that person unless you're also sorry for Telsa. But above all, just be sorry for being yourself.

 

[dnmun]

Thanks for the info. For some clarification on this :

sorry to see another person going this way with laptop cells but to answer your question:

I got the cells free, I live within 100yds of a 40+ miles of paved bike trail (old railroad grade) that has few hills of any note. I am very mechanically inclined (lifetime of repair of all different types of equip including Computers, Helicopters,Vehicles and one year of Electronics Tech training way back when we used slide rules " Side note (I got two questions wrong on a math test in high school using that slide rule because of the built in error factor)" I can't drive any more because I have lost 90% of my vision, so this is my "get out of the house project". So don't be sorry ok? I go into this with what remains of my eyes wide open and the gains far outweigh the possible losses.

Cheers!

Grant

free is the best policy, my eyes aren't that far gone, but here is what you need for 8S packs:
http://www.ebay.com/itm/JST-2-5-XH-9-Pin-Connector-Plug-w-Wire-x-5-sets/111187487724?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D18242%26meid%3D2143082053750076139%26pid%3D100005%26prg%3D8344%26rk%3D3%26rkt%3D5%26sd%3D111187487696%26

ps: i was the state slide rule champ back in 1958

 

[gaisom]

Can't beat the price for a pack of five at that link Thanks

Pretty soon I am gonna have plugs coming out my ears

ps: you were just the champ cuz I couldn't drive yet

 

[dnmun]

if you build it as two 8s packs and use the icharger for balancing then you will need to use the 9 pin plugs. one is ground and the others are the tops of the cells. you can plug the cellogs into the 9 pin plug to monitor the pack voltage too.

 

[gaisom]

Well, I am out of money now. Cell logs are something for the future. I think I can spring for one of those digital voltmeters that scan from cell to cell so I am going to have to do that or check overall voltage once in a while with a voltmeter. Spent way more than I figured on stuff to set up the packs and charge em and test em and.... blah ..blah..blah..

Not having much of an income really sucks at times :wink:

Oh, I forgot, I am going to set up as 8s4P to start with.. Guess I should figure out what the AH will be using 2200mah cells. Gonna run em at 3.8 to 4.1 so will lose about 8% just from not charging to full voltage.

Cheers!

Grant :lol:

 

[TwoWayStreet]

If your Sanyo 2200mAh cells are new, then the actual capacity is 2200mAh at 0.5C from 4.20V to 3.00V. So 4 in parallel will give 8800mAh. If they are used, then you need to test and determine the remaining capacity before making a pack out of them. Otherwise, you will have a wildly mismatched pack where one group of cells has very low capacity.

You're are correct about giving up roughly 8% by charging to 4.10V instead of the max of 4.20V. But I'm not sure what you mean by 3.8V? 3.80V (rest voltage) is about 50% SOC for Sanyo cells. So if you only run from 3.8 to 4.1 (both are rest voltages), you will only use about 42% of the cell potential energy.

 

[dogman dan]

Time spent sorting the cells is good idea. If any cells are lower in capacity, you sure don't want them all in one parallel group. Ideally don't use any that are a lot lower capacity.

Stopping at 50% is fine if you are done. But you don't have to keep them above 3.8v. There can be a lot left at 3.8v.

Where is the cliff for those sanyo cells two way? is it around 3.5v like the hobby king lico?

 

[TwoWayStreet]

At 0.5C, the knee (cliff) begins at about 3.05V (not 3.50V).

 

[gaisom]

They are new cells. I ended up with 156 of them from HP Laptop batteries my brother had left over from some contract he did where he bought too many batteries

You are correct, I misplaced a number in my head or something on the low end. I was going to go with 3.20 as I have read in quite a few places that battery life is greatly extended if you don't use the whole range of available voltage in the 18650 Cells. I am going to have to recheck that I think.

Wish my charger would get here, want to run few shallow charge/discharge sessions before doing any voltage leakdown tests. I am beginning to wonder about HobbyKing, first Ebay removes the auction I won the charger in after I paid for it, then the shipping number at SingPost seems to be expired the day after it was shipped. Guess I will just have to cross my fingers and wait. At least if I have troubles I have a daughter in China. I can send her over to HK in attack Mode

 

[dnmun]

the article on batteries that pdf just posted and arkmundi put up the pdf links for talked about this.

it turns out that if you discharge the lipo by more than 50% the volume changes in the polymer become significant so the introduction of the lithium titanate anode electrode helps prevent that volume change.

it turns out that the biggest risk is from charging at high rates and the growth of dendrites of lithium on the surface of the anode. this is worst at low temperatures so it covers the argument of why charging at high rates and low temperatures is sure to kill the pack fastest.

 

[dogman dan]

Interesting that the knee is that low voltage. That would make even stopping at 3.2v fairly conservative.

I don't know about the effect on lifespan, but my experience with both cheap lifepo4 and low quality hobby lico has been that 100% discharges just make you work to rebalance the pack. I think if you stay above the knee with all your cells, you stay more balanced.