Info on Laptop 18650 LiCo cells

[veloman]

lol, well she only needs 10 to go to work and back. the lifepo4 main pack on her bike is beat and only gives about 5ah

[Hillhater]

..It's beyond my imagination how anyone can put up with a 20 miles range, let alone 10.

There is no point in carrying more battery weight ( and cost) than you actually need.
20 miles would probably cover 80% of most cycling commuters.

[SamTexas]

New info added to Page 1 of 2.

[DrkAngel]

2008 build - 37V 20.8Ah



2008 Build - 25.9V 31.2Ah



2011 Build - 25.9V 31.2Ah in an eZip oem pack.



2013 builds?
22.2V 41.6Ah in an eZip oem pack = .932 kWh (oem SLA = .240 kWh but < .150 usable)
44.4V 20.8Ah in an eZip oem pack = .932 kWh (2 packs run parallel = 44.4V 41.6Ah!)
Modular - 11.1V modules. 22.2V, 33.3V, 44.4V, 55.5V etc. easy and quick builds.
Adjustable "bulk chargers".
Cheap V monitor LV alarms available! - Use multiple for > 8s.
Rebuilding 5 - 2008 builds - re-evaluating, capacity rating-matching and reassembly of 400+ cells.
18650 cells paralleled with small RC Lipo packs for better surge capability? ... Will try it.
(33.3V 20.8Ah Laptop + 33.3V 5.7Ah RC Lipo = 33.3V 26.5Ah that fits in eZip pack.)
Much neater builds, 9-10 gauge tinned copper braid for power rails, 22ga solid tinned copper balance connection wires/

Homemade Battery Packs - very large thread!

[SamTexas]

DrkAngel,
One of the more difficult task in assembling packs is the soldering process. Seems to me that you have that down really well. Would you explain the process you use, any trick you have to make it faster and more robust? Temp, solder type (lead or lead-free), flux or no flux. Solder on tabs vs on the cells. etc...

You are welcome to do it here or in your thread.
Sam

[DrkAngel]

DrkAngel,
One of the more difficult task in assembling packs is the soldering process. Seems to me that you have that down really well. Would you explain the process you use, any trick you have to make it faster and more robust? Temp, solder type (lead or lead-free), flux or no flux. Solder on tabs vs on the cells. etc...
Sam

Leave cells connected!

Tabs are much easier to solder than cells.

1st, you must abrade solder points, dremel grinder-sander, file or even scrape with knife etc.
Flux - I use a Q-tip to spread a thin amount.
40w iron recommended (25w might work)
A hotter soldering iron transfers less heat to cells - less contact time required!
"Pre-tin" - apply solder to all solder points.
Apply a small drip of solder to tip ... allow to regain heat, apply to fluxed solder point, try 2 sec, if not good allow to cool then try 3 seconds.
(Keep a few bad cells for test soldering!)
After all contact points tinned, reapply flux.
Position for final solder apply heat till solder melds together. (Hold solder points together with chromed metal probe, small screwdriver etc.)
Test all solder connections with pick or similar.

Direct to cells is similar but usually requires slightly longer contact time, test on bad cells!


Quick Review
Abrade solder points
Flux all solder points
Hot soldering iron
Pretin solder points
Reflux
Collapse pretined solder points onto each other
Use metal probe to position

Rejoice!

Do many cells at once each step for all, then next step for all etc.
Practice-repetition makes perfect

[SamTexas]

Pretty much what I did. Lots of practice and I still dread soldering.

Lead or leadfree solder? I have a tough time with leadfree, so now I use lead (63/37).

[DrkAngel]

Solder type
I use Lead solder - electronic grade preferred, non flux core, (not rosin nor acid), I put all the solder on irons tip first, so flux on surface is needed anyhow.
Oops! Just rechecked ... using 60-40 rosin core ... on my latest builds, anyhow.
0% cracked solder joints! But I did stabilize builds inside eZip cases.

Tinned Copper Braid
Ideal for connecting separated cells!
The flex between cells helps prevent cracked solder connections.
Hunt for good price - Just found 200' 22ga for ~$18.99 on ebay. (Good for parallel-balance wiring)
10ga? for full amperage.

[veloman]

Tinned Copper Braid
Ideal for connecting separated cells!
The flex between cells helps prevent cracked solder connections.
Hunt for good price - Just found 200' 22ga for ~$18.99 on ebay. (Good for parallel-balance wiring)
10ga? for full amperage.

Who is the seller? A few minutes of searching didn't find anything close to that price.

[DrkAngel]

Tinned Copper Braid
Ideal for connecting separated cells!
The flex between cells helps prevent cracked solder connections.
Hunt for good price - Just found 200' 22ga for ~$18.99 on ebay. (Good for parallel-balance wiring)
10ga? for full amperage.

Who is the seller? A few minutes of searching didn't find anything close to that price.

7 - 2x100' lots left - http://www.ebay.com/itm/Cable-Shielding ... 2a288ac33b

[veloman]

Awesome, thanks!

[DrkAngel]

More 18650 builds

37V 20.8Ah - 10s8p - 2008




Power tool rebuild - 4s2p - 2011



22.2V 41.6Ah - 6s16p - 2013



29.6V 31.2Ah - 8s12p - 2013


33.3V 31.2Ah - 9s12p


"My" Homemade Battery Packs

[auarhau]

Nice battery packs! I am curious about the power tool pack. How does the 18650 cells handle a drill? I was afraid the low discharge rating on those cells made them unsuitable for a drill. Also I have been sourcing some 18650 cells from old laptop batteries, but after reading about them I got very worried about fires etc. How low voltage can they be, and still be safe for me to recharge and use? So far I tossed away batteries below 3v, but that leaves me with very few good ones.

[DrkAngel]

I try charging up ... then testing, all cells ... with any voltage.
Name brand Laptop cells are probably the safest technology available.
See - "Explosion" - "Fireball" tests! ala LFP

The pictured Sanyo cell in the power pack were low discharge rated but sufficient for screwing computer screws.
Differing cells have differing C rates.
I recently tested some Sanyo 2200mAh with excellent discharge capability.
2350mAh Samsung also provide decent power tool capability.
Test each fully charged cell for C rate. - Use a discharge device of 1 - 2A, measure voltage sag and compare between all cells.
Those with the least sag have a better discharge capability.
5Ah laptop cells at 2C = 10A (30 min run time) is equal to 1.2Ah NiCd at 8.3C (7 min run time).
4.4Ah laptop cells at 4C brief surge = 17.6A is equal to 1.2Ah NiCd at 14.66C.

[veloman]

Do you separate the cells with anything to protect against shorting if the plastic wrap wore away?

What do you consider a 0.2v drop under 1amp load for a pair? That's about 5% sag for 1/3c (I estimate the average capacity of used laptop cells to be around 1.5ah each from what I have seen in my testing). Some pairs drop .4v, and I wonder if those are still okay to use, for example, in parallel with the lower sag cells?

I don't plan to build anything with under 60ah capacity. Will likely have 120ah for use on my lightweight motorcycle (limited to around 100amps peak, and 30-40 constant.)

[DrkAngel]

Do you separate the cells with anything to protect against shorting if the plastic wrap wore away?

What do you consider a 0.2v drop under 1amp load for a pair?

No, I wrap cells together tightly, so there is no wear.
I have never had any wear through, even with loosely wrapped cells in a soft pack.
Now, I tightly wrap cells with clear boxing tape and immobilize in rigid "bricks", stabilized with sheets of closed cell foam padding.

I forgot to mention ...
I began testing cells at ~ 4.10V.
This bypasses the excessive sag from 4.20V, which with some cells, is a region of miniscule energy capacity.
Especially when comparing batches of cells it is important to maintain a reasonable-warm equal temperature for all cells. 10 degree F difference will skew reading noticeably.
Best reading was .16V sag from 4000mAh pair, s3p2 with 12V 2.8A drain (fan) (sag measured at each pair), but this was a HD formulation built for massive discharge(?), capacity sacrificed to provide good surge capability, (I saved these for power tool pack build).

See - Homemade Battery Packs - Index
You might find interesting - Watts = MPH eMotorcycle - some info is outdated - my knowledge-understanding has progressed - will try to update-enhance my posts, as time allows. (Thread got twisted into voltage as SOC gauge debate, opponent(s) was only familiar with LiFePO4 (flat discharge curve), while I was using LiCoO2, with a much broader voltage range.

[kje]

How do you store Laptop 18650 LiCo cells if you have a lot?

I have a lot of cells in a big plastic box. Should I protect the ends of each cell? (+ and -) If one cell touch the opposite polarity on another cell would that harm the cell and maybe cause some danger?

[DAND214]

If the cells have any tabs on them, YES. bBare ends with not tabs, not much a concern.

Dan

[DrkAngel]

How do you store Laptop 18650 LiCo cells if you have a lot?

I have a lot of cells in a big plastic box. Should I protect the ends of each cell? (+ and -) If one cell touch the opposite polarity on another cell would that harm the cell and maybe cause some danger?

Find a box about same width as cells, (cd-rom box?), place cells in box, stacked on side with pos in one direction neg in other.
Each end against cardboard.

[kje]

Thank you!
I`ve stored a lot of fully charged cells with tabs in a big plastic box for a long time. Could some of the cells been drained from weaker cells?