Homemade Battery Packs

Try the recommended "cheap" $5 2 cell chargers.
About 600mah charging rate, might get a noticeable, but safer, degree rise if bad.
Any heat dissipates at safer temperature.

As for thermal runaway, from soldering, try following my recommendations.
I've soldered, literally, hundreds & hundreds of cells, with nary a mishap.
3 - 80cell packs & 2 - 84cell & 1 - 40cell(too small for 675w output motor) & many laptop pack replacements.

And, of course, I've always recommended a PCB (Protection Circuit Board - maybe - Protect and Charge Board) to safeguard against overcharging any cell. Search for 25.9v or 37v or 48.1v etc. on eBay etc. Or All-battery.com

Also ... I agree that Li-ion, Lipo etc. can be dangerous, typically due to: mistakes, uninformed experimentation, faulty equipment etc.

The informed mind is the prepared mind! Basic electrical knowledge, reasonable quality equipment, a template of success, and common sense, should make Li-ion production a rewarding experience!

As have been said before all batteries carry certain risks just like any energy store. But 18650 format does have some safety but in: The vent the at positive end. That makes is "safer" that the pouch variation.

How do you charge this pack ?

SamTexas said:

As have been said before all batteries carry certain risks just like any energy store. But 18650 format does have some safety but in: The vent the at positive end. That makes is "safer" that the pouch variation.

Click to expand...

The whole perimeter of a pouch cell is a vent.... Not to mention, the lack of pressure vessel makes it impossible to even make a "bang" (they can only vent fire rather than explode and vent fire both like 18650s). Unlike 18650s, which often sound like a shotgun blast and blow shrapnel. The vents are a weakened pinhole area under the seal. If the cell has a contamination related slow off-gas event, the vent can function. If you have a runaway, the vent does nothing and the cell grenades.

Red_Liner740 said:

Also, OP, would u entertain the idea of selling some of your made packs?

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Honestly, 18650 packs require monitoring, and occasional repair.
If a person has the capability of, what I consider, "proper maintenance" then they would have the capability to build their own packs.
I would feel uncomfortable about supplying a pack to a person, possibly, lacking in the skill and knowledge to use and care for it.

I have built some for local persons, but I supply check-ups and service, etc. Upstate NY USA

^^ I agree absolutely, the whole "buying a pack" was more from the logistical point of finding the laptop batteries in sufficient amount than from the point of "i'm a lemming and i want a plug and play system"

Anywho, i was able to procure 100 laptop batteries at a phenomenal price of 75c a pound at a local recycling depot. the 100 bats ended up costing me $55 and change, with the option of being able to go back and purchase more down the road.

So now they are sitting in two milk crates and i have ZERO time to touch them as i just moved into my house and there is looong list of priorities before "tinkering with stuff".

bah, sucks!

Red_Liner740 said:

^^ I agree absolutely, the whole "buying a pack" was more from the logistical point of finding the laptop batteries in sufficient amount than from the point of "i'm a lemming and i want a plug and play system"

Anywho, i was able to procure 100 laptop batteries at a phenomenal price of 75c a pound at a local recycling depot. the 100 bats ended up costing me $55 and change, with the option of being able to go back and purchase more down the road.

So now they are sitting in two milk crates and i have ZERO time to touch them as i just moved into my house and there is looong list of priorities before "tinkering with stuff".

bah, sucks!

Click to expand...

It's a blessing you're not wasting your time, combining unmatched used cells (many at or near the end of their useful life cycle all ready if they were in a laptop pack discarded as bad), only to end up with a very low performance sketchy pack that has a strong chance of burning your house down.

liveforphysics said:

I don't care what you guys want to do, and I'm all for enjoying fires and explosions and things, but somebody should at least be made aware of the risks.

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And I don't give a shit about your thought, opinion, or self-proclaimed expert status on the subject. You are nothing but a used car saleman trying to push pouch lipo. There are plenty of salemen on this forum but you are different from them. You hide behind your childish technicality to get a commission on each lipo sale.

Sam

Okay we get it, the worlds gonna end if we reuse laptop batteries...THANK YOU for your concern, i think u have mentioned the danger enough times that you can leave this topic alone.

I know I might of said something like that in the past about liveforphysics luke, but I'm pretty sure it's not the case. I know it's frustrating arguing with him because he tends to be condescending and rude sometimes, but he really does know his stuff. While he might be warning you about the dangers of using these because he enjoys pointing out when people are wrong, I can assure you it's not to get you to buy lipo. The fact is, as DrkAngel put it,

Honestly, 18650 packs require monitoring, and occasional repair.

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With out this sort of maintenance and diligence you could very well be the first person on this forum to burn your house down. Tesla spend years and millions of dollars perfecting a saftey system to get 18650 cells working for them. Are you prepared to play Guinea pig?

That being said, I can definitely appreciate the sheer awesomeness of making your own battery pack completely from scratch. It will make a great lesson in the importance of matching cells and building safe guards into the system to prevent bad cells from bringing the whole group down. It'll make for a great experiment if I ever get around too it, but I hold no illusion of being able to building a battery pack that I could use daily, or even get a return on the time I invested in it. Maybe if the cells were free, in great shape, and I already had experience doing it. Otherwise it doesn't really seem worthwhile when my I could make the $200 to buy an equivalent lipo pack in less than the time it would take me to design, test, repair, and maintain a pack of used 18650 cells.

auraslip said:

I know I might of said something like that in the past about liveforphysics luke, but I'm pretty sure it's not the case. I know it's frustrating arguing with him because he tends to be condescending and rude sometimes, but he really does know his stuff. While he might be warning you about the dangers of using these because he enjoys pointing out when people are wrong, ....

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It might be relevant, that liveforphysics lists, in his profile, under interests - "Racecar engine design"?
That might seem to make him the "Anti-christ" ... against electric engines and batteries.

auraslip said:

..., but he really does know his stuff.

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I disagree. He's an idiot. This is the guy who said an ebike is better than a motorcycle. This is the guy who said lead-acid is the most dangerous battery, then Nickel is the most dangerous, then Lithium Cobalt is the most dangerous. This is the guy who can never provide a balanced view of anything. This is a self inflated kid with little knowledge about anything at all.

Sam

18650 cells dangerous! ... ?

I have to compliment Liveforphysics for trying to prove his point using the scientific method.
First, he considered all the ways, that he believed, that the 18650 cells might be hazardous.
Then he devised tests ... tests that were specifically designed to show 18650 cells burning, exploding etc.

Test #1
18650 cell -
overcharged then
crushed in vise
skewered with a screwdriver
pounded - crushed-mangled by heavy hammer

[youtube]vi5lGtm_ItQ[/youtube]

Test #2
18650 cell -
overcharged then
hyper-charged with V & A
placed under a heat gun
finally with torch applied!

[youtube]6njY0mg1TP4[/youtube]

Sadly, for LFP, his failure to demonstrate any hazardous results caused me to consider 18650 cells to be even safer than I had previously believed.

Except for when he applied a torch directly to a cell ... which I don't intend on doing!

It did shake my spirit tho ...
After LFP scientifically formed his hypothesis, devised tests to prove his hypothesis, diligently performed these tests and noted the findings ... but then ... apparently completely ignored his own results ... by standing steadfast in his assertion that 18650 cells were dangerous and liable to burn and explode???

I'm afraid that he, himself, severely degraded my opinion of him.
After my disappointment wore down and I accepted it ... I was able to watch the 2nd video again and laugh at the "stupidity" of performing flaming-exploding tests in the midst of gasoline cans and nitrous tanks.

I'm still wrestling between:

1) A balanced Li-ion charger and unsupervised discharging.
2) A PCB (BMS)

Any advice based on real life experience?

Nice little volt meter for 8 cells, or less!


Meter & Low Voltage Alarm

Dark--Can you please tell us what kind of motor and riding these packs were used with?

<<My 37v li-ion 20.8ah pack, (used on a 2008 EZip Mountain Trailz), has been charged hundreds of times and just passed 3500miles, (ran it through the last 2 Winters!)!

My other main battery is a 25.9v li-ion 31.2ah, (used on a 2008 EZip Trailz), has also been charged hundreds of times and exceeded 3000miles.>>

Nimbuzz said:

Dark--Can you please tell us what kind of motor and riding these packs were used with?

Click to expand...

EZip Trailz vs Mountain Trailz

EZip Basics - Electric Bike or Electric Assist Bike

EZip Mountain Trailz 1600 mile - 1Year - Report

SamTexas said:

liveforphysics said:

I don't care what you guys want to do, and I'm all for enjoying fires and explosions and things, but somebody should at least be made aware of the risks.

Click to expand...

And I don't give a shit about your thought, opinion, or self-proclaimed expert status on the subject. You are nothing but a used car saleman trying to push pouch lipo. There are plenty of salemen on this forum but you are different from them. You hide behind your childish technicality to get a commission on each lipo sale.

Sam

Click to expand...

This is some classic stuff! Love it!
I've given quite a bit of LiPo away, never sold a single pack.
I've visited the nano-tech (and other) factory in China, visited (for business reasons unrelated to ebikes) some other LiPo factories in Korea, and spent a few days with the owner of hobbyking in Hong Kong and in China.

To get some things straight:
#1 He had no idea people were running ebikes on RC Lipo.
#2 All our ebike Lipo sales for the last 5 years wouldn't keep his factory busy for more than an hour.
#3 All of us combined are a statistically insignificant part of his battery businesses that means nothing to him.
#4 HobbyKing has still only lost money (and he is fine with that, his money comes from other industry, he runs hobbyking for fun, and has said the moment its not fun anymore he will close it down),
#5 The whole RC battery division is just a side-gig as something to do with OEM mfg left overs and surplus, excess supplies from OEM contracts etc. This is why supply/stock consistency is so random.
#6 He absolutely hates the thought of people charging these large Lipo packs in there garages and homes.
#7 After showing him vids of high-power ebikes (which he didn't know existed) he thinks ebikes should use LiFePO4, and thinks RC Lipo should only be used for racing (loves the idea of racing ebikes) or by experts in charging and charged outside somewhere safe.
#8 Ebike battery sales (in the form of RC packs) don't matter to him, and he would rather discourage than encourage them.

I've never received anything from him in return, never will, and wouldn't accept some stupid commission anyways. Never have worked in sales my whole life, and don't ever plan to. Engineering the things that other people can sell seems to be much better suited to me.

SamTexas said:

auraslip said:

..., but he really does know his stuff.

Click to expand...

I disagree. He's an idiot. This is the guy who said an ebike is better than a motorcycle. This is the guy who said lead-acid is the most dangerous battery, then Nickel is the most dangerous, then Lithium Cobalt is the most dangerous. This is the guy who can never provide a balanced view of anything. This is a self inflated kid with little knowledge about anything at all.

Sam

Click to expand...

LOL! Coming from the guy who is wrong about everything, I'm flattered.
The more SamTexas dislikes something, the better you know it is.


This idiot needs to get back to work on the TTXGP pack build for this weekend, and tear down and inspect the packs from the world championship winning (friday night in Vegas, Geico MinimotoSX) electric motocross bike battery packs to see how everything handled the vibration and shock of hard jumping and bumping a few hundred times.

It's part of what you do when your profession is to design and engineer performance battery systems.

Its good to have you here Sam. Morph and Aura etc finally seem to have there heads on an exit route from there anus', but I know being a stubborn Texan you can provide years of fun and entertainment for the group.

Here I have been championing recycled notebook batteries, and just realized, ... I haven't built one in 3 years!

My 37v li-ion 20.8ah pack, (used on a 2008 EZip Mountain Trailz), has been charged hundreds of times and just passed 3500miles, (ran it through the last 2 Winters!)!

My other main battery is a 25.9v li-ion 31.2ah, (used on a 2008 EZip Trailz), has also been charged hundreds of times and exceeded 3000miles.

Problems, after being put into service, has been limited to, dented cells replaced(accident), cracked solder connections (contained in fabric "lunch bags"), 1 failed pair - replaced, and 3-4 weak pairs replaced, (possibly "over taxed" by failed, (cracked) circuit).

Anyhoo ... I will be building, at least, 2 Li-ion packs and will do my best to document, and provide tips and pictures.

25.9v - compatible with all 24v's I've run into.
37v - compatible with all 36v I've run into.
48.1v - Sorry ... not built ... yet.

Stay tuned ... might be a few days! Weather forecast is too good to be puttering around, inside!

LIVE FOR PHYSICS - YOU SHOULD READ THIS BOOK

Because lets be honest, people put up with you here because you have experience and talent. You'd be a leper if you weren't doing so many cool things. You're a likeable villain. Hard to hate a man with a flame thrower.

But eventually, everyone here is gonna have a flame thrower and a bad ass ebike? Then what will you be? Just a sad lonely villain with no one to feel better than.

Thank you for the advise, and thank you for the kind words.

I do try never to be liked by more than about 10% of the folks on a forum. It seems that slim 10% is what holds about 99% of all the worthwhile contribution, innovation, and development in any sort of group setting (including forums).

The rest seems to be noise and/or comic relief. If they are sharp enough though, they will absorb from that 10% as much as possible, and it will lead them to a place they wouldn't have found alone. If they are fools, they will battle the 10%.

If I had more friends, I would only end up getting less work done. :'( As it is, it seems I have calls/texts every hour or so all day long from buddies wanting to go do crazy stuff together, and I sadly have to ignore calls and break plans all the time just to get projects finished on time. :'(

Luke's life priority order:

1. Enjoying and appreciating the infinite beauty designed into the nature that surrounds me.

2. Helping strangers I encounter that need it with random things no matter how big or small.

3. Projects that help the electric revolution.

4. Friends/family.

5. Other projects.

6. Job/income/money/investments etc.

SamTexas said:

I'm still wrestling between:

1) A balanced Li-ion charger and unsupervised discharging.
2) A PCB (BMS)

Any advice based on real life experience?

Click to expand...

After finding comparable cells, I used PCB for charging and never for discharging.
Balance charger should work nicely.

Of course before deeply discharging, monitor pack during initial discharges.
Volt meter highly recommended. Do not discharge below 3.5v (no drain voltage), or 3v under throttle.
Also available are, low voltage alarms!

Very nice item is an 8 cell voltage monitor w/programmable low voltage alarm!
Plugs into a balance connector and monitors from 1 to 8 cells.
Shows total voltage, then cycles through individual cells, nice bright led!

Perfect for my 25.9v, 7 cell packs. Also, for 8 cell LiFePO4.
Might leave it in balance connector, or extend to front, on bars.

Meter & Low Volt Alarm

A marvelous little item, for only $6.29 - includes shipping!


Low voltage alarm is programmable in .1v increments from 2.7v to 3.8v.

DrkAngel said:

After finding comparable cells, I used PCB for charging and never for discharging.
Balance charger should work nicely.

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Which PCB do you use? Has it been working reliably for you?
If you were to do it again, would you use balance charger or PCB?

Eagerly awaiting updates!

Funny enough i have over 300 cells sitting on my work bench....currently tearing apart the battery packs and measuring sitting voltage. Suprisingly, 90% of them still have over 3.7V, with most being at 4v and up. About a dozen or so are 0v so far, and about two dozen are between 3 and 3.6v which will be the first to go on the charger.

As soon as i'm down tearing it down im at an en passe until i can charge and measure capacity. I can see where this is a bit overwhelming when it comes to time usage. Its taking up a lot of man hours...but its something to do.

Any tips/hints on how to setup a capacity measurement?

Red_Liner740 said:

Eagerly awaiting updates!

Funny enough i have over 300 cells sitting on my work bench....currently tearing apart the battery packs and measuring sitting voltage. Suprisingly, 90% of them still have over 3.7V, with most being at 4v and up. About a dozen or so are 0v so far, and about two dozen are between 3 and 3.6v which will be the first to go on the charger.

As soon as i'm down tearing it down im at an en passe until i can charge and measure capacity. I can see where this is a bit overwhelming when it comes to time usage. Its taking up a lot of man hours...but its something to do.

Any tips/hints on how to setup a capacity measurement?

Click to expand...

Just set up a circuit to discharge through a resistor and time it. When the voltage gets to whatever you want for a LVC setpoint, have the circuit trip open a relay and stop both the discharge and timer. Should'nt be too complicated with a couple (maybe 3 or 4) 555's and a couple of op amps. You could even run several setups in parallel with one timer, shutting each off with an independent readout.

Cameron