Homemade Battery Packs

[liveforphysics]

I've not balance charged for the last ~100 cycles or so.

If you start with good matched cells, and test them to ensure they are matched and consistent, you can start with them balanced, and they will stay balanced until some cell in a group becomes weaker or develops a tiny increase in self-discharge, or if the pack has only the outside cells cooled much better than the inside cells, etc etc.

I've never had a BMS on any of my bikes, and likely never will.


The danger here isn't not having a BMS, it's simple enough to just check with a multi-meter once in a while to make sure it's staying balanced.

The danger is starting with an inherently dangerous chemistry cell in a sketchy unknown condition (expired shelf-life and/or various states of used etc), and ALSO not having a BMS or any way to even get a heads up if you're having a cell reversal in discharge or an overcharge event that explodes or vents fire unattended in your garage etc.
All it takes for that to happen is any single cell in the pack to develop a tiny dendrite growth or separator break-down (which both happen on older cells), which drains one bank of cells without you knowing.

 

[icecube57]

[youtube]mKHkxt76FWY[/youtube]
Bravo! Well spoken. I hate 18650 packs especially after i recieved a dud from v power that was 48v 20AH and was 4-5AH short and could track down which cells kicked the bucket.

 

[DrkAngel]

Bravo! Well spoken. I hate 18650 packs especially after i recieved a dud from v power that was 48v 20AH and was 4-5AH short and could track down which cells kicked the bucket.

Fortunately, this thread, explains how to acquire, then test-verify each cell, before building your own pack. Of the size and capacity that meets your need. Oh, and it might cost you 1/10, (probably a lot less!), the cost of the "v power".

I would, much rather, personally verify the components, and assembly, of a 31.2ah Li-ion pack, (at a cost of $50, includes charger), than pay $400 for the OEM 6ah pack (EZip).

Of course it is a lot of work!
Most of it just waiting, during cell tests. Fortunately, I have multiple projects running constantly!
I have 5 packs, that have been in service for 3 years, still performing admirably.
Of course I schedule periodic checkups, and occasional repairs, which I would classify as "proper maintenance".

The alternative is to pay some Chinese guy to do it for you, with new, but possibly untested, or briefly tested cells. ... at 10 times the price!

And, if you build it yourself, you can repair it yourself.
Much easier than trying to ship it back to China, and waiting a month, or 2, ... for any response!

 

[icecube57]

With what you are doing id rather have a cba2 and check all my strings atleast for capacity to have a good data to pair cells instead of falling back on the fact that the cells are new and maybe viable despite being unused for years.

 

[DrkAngel]

Tenergy 25.9v Li-ion charger report:
I decide that the most relevant test would be the maintenance of voltage equalization after repeated deep cycles.
Packs are discharged into the 3.7*v range. (3.5v under moderate throttle)
Further tests will follow.

31.2ah Li-ion 18650 cells (used-recycled):
1-3 Cycles, 4.17v-4.19v
4 th Cycle,4.17v 4.2v (not sure of actual variance, meter doesn't measure 1000ths)

26ah Lipo (used-recycled):
1-5 Cycles 4.17v-4.19v

Packs are performing nicely.
Charger is performing, better than expected!
Variance of equalization, after 4-5 cycles, is minimal to non-existent!

 

[neptronix]

Tenergy 25.9v Li-ion charger report:
I decide that the most relevant test would be the maintenance of voltage equalization after repeated deep cycles.
Packs are discharged into the 3.7*v range. (3.5v under moderate throttle)
Further tests will follow.

31.2ah Li-ion 18650 cells (used-recycled):
1-3 Cycles, 4.17v-4.19v
4 th Cycle,4.17v 4.2v (not sure of actual variance, meter doesn't measure 1000ths)

26ah Lipo (used-recycled):
1-5 Cycles 4.17v-4.19v

Packs are performing nicely.
Charger is performing, better than expected!
Variance of equalization, after 4-5 cycles, is minimal to non-existent!

Yup, welcome to bulk & non-balanced charging.
Nothing special about the tenergy.
My meanwell and icharger ( without the balance leads connected ) have the same results.
There is always a little bit of variance in the voltage of the packs as they will naturally do their own thing.
You just need to intervene with a real balancing charger when it gets bad. 4.17v - 4.20v is what i would call getting into the inbalance zone.

Now if you had well balanced packs, they would look like this at the top of the charge after many dozens of unbalanced cycles:

And like this near the bottom of the charge after dozens of unbalanced cycles:

 

[DrkAngel]

Nothing special about the tenergy.
My meanwell and icharger ( without the balance leads connected ) have the same results.

Except ... the Tenergy costs less than $25!

 

[neptronix]

Nothing special about the tenergy.
My meanwell and icharger ( without the balance leads connected ) have the same results.

Except ... the Tenergy costs less than $25!

I'm not hating on your choice of charger, just saying that what the charger does is no different than the meanwells / other power supplies that are becoming popular on the forums as chargers.

 

[amberwolf]

Basically any pack's regular charger would still work for this, even without a balancer or BMS, as long as it is set to stop at the right voltage. Many of them are pretty inexpensive, as long as you don't count shipping. Counting shipping, lots of the "cheap" ones end up roughly equal in price to the higher-cost ones.

 

[DrkAngel]

Basically any pack's regular charger would still work for this, even without a balancer or BMS, as long as it is set to stop at the right voltage. Many of them are pretty inexpensive, as long as you don't count shipping. Counting shipping, lots of the "cheap" ones end up roughly equal in price to the higher-cost ones.

Except ... the Tenergy costs less than $25! Shipping FedEx $10+, $11+ for 2.
Free shipping, if order over $75 w/code "THANKS".
all-battery.com

 

[neptronix]

Compare to:

$68 shipped for a 350w genuine meanwell ( at your voltage, will do about 14 amps... )
~$40 shipped for a 150w genuine meanwell ( at your voltage, will do about 6 amps... )
Even less $ if you're okay with a non-genuine one.
Meanwhile the tenergy outputs about 50-60 watts, all of 2 amps.

It's cool because of it's size, but compared to some other options it is not that great of a deal for the amps it provides.

 

[icecube57]

The tenergy chargers can be ganged in parallel...

 

[DrkAngel]

Nothing special about the tenergy.
My meanwell and icharger ( without the balance leads connected ) have the same results.

Compare to:

$68 shipped for a 350w genuine meanwell ( at your voltage, will do about 14 amps... )
~$40 shipped for a 150w genuine meanwell ( at your voltage, will do about 6 amps... )
Even less $ if you're okay with a non-genuine one.
Meanwhile the tenergy outputs about 50-60 watts, all of 2 amps.

It's cool because of it's size, but compared to some other options it is not that great of a deal for the amps it provides.

Which meanwell, "Mean Well"?, are you using?
The charger designed for Lead Acid batteries, or the basic power supply? (360w about $150?)
I wasn't able to find anything, by them, designed for Li-ions???
The 7S capable icharger costs $170+ !

I'd much rather pay, $58 for a pair (2) of Tenergy, designed for Li-ion, (shipping included!)

 

[icecube57]

...blinks innocently as if he knows what is going on.

 

[neptronix]

Which meanwell, "Mean Well"?, are you using?
The charger designed for Lead Acid batteries, or the basic power supply? (360w about $150?)
I wasn't able to find anything, by them, designed for Li-ions???
The 7S capable icharger costs $170+ !

I'd much rather pay, $58 for a pair (2) of Tenergy, designed for Li-ion, (shipping included!)

There are lots of threads on here about meanwells, just search around.

http://cgi.ebay.com/MW-27V-DC-13A-3...ultDomain_0&hash=item3a66021141#ht_3876wt_957

This is what i am referring to, you can adjust the voltage +/- quite a bit.. in fact my 48v has a bigger range over what is advertised, so you may be able to do 8s on this.

They work great as lithium chargers actually, CC-CV is all your need. The only downfall is that you will not have a light indicating that the charge is done, but just like your tenergy, it will just kinda float the voltage. Instead of putting out current spikes from time to time, it will keep the pack on a miniscule amount of amps.

You can use a watt-meter to determine the state of charge, and when the amps start gradually dropping, you'll know that it's about to finish.

What differentiates them from just plugging them into a bare power supply is that they have current limiting. The only mod you really need to make is to turn the current limiting value down a bit with the resistor mod. Then they work just as the Tenergys will, as far as how the power is transferred to the pack.


As for the iCharger, there are very low prices on hobbyking actually.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6609

This is the one i have, although they have an 8S version that will work too. You just need to make a balancing adapter that will turn your pack into 2x 4s leads as if it were an 8s.. the iCharger will see the 7 cells and charge that odd number, no prob.

The 10S charger would be great if you ever wanted to break into the 10S zone eventually.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9005
Otherwise they have an 8s charger. It may be able to pump out a few more amps at 7s than the 10S charger.

These would be good as main chargers too, and they are fantastic at balancing and collecting data about your cells ( that's how i get the graphs i make ) but nothing compares in terms of amps per $ than the meanwells if you are looking for just a bulk charger with no frills.

 

[DrkAngel]

The 10S charger would be great if you ever wanted to break into the 10S zone eventually.

Been running my 37v, recycled 18650 cell, 20.8ah pack, for 3 years - 3500 miles.
Last build ... when I built the:
Li-ion 25.9v 31.2ah pack
and the
Lipo 25.9v 26ah
I also built:
Lipo 37v 26ah, in a fabric 6-pack cooler = .96kwh!

The reason I play at 25.9v, is that it works so nicely with the Currie EZip-IZip bikes, and keeps it 20mph "legal", if you run the battery down and let some air out of the tires. .
Combined with my other mods, it can turn a base model, budget ebike, into a really decent machine!
I have 5, 4 different models, all with various modifications. (1 is geared for torque, then bumped to 37v, w/homemade studded tires! Ran it through 2 Winters!) Latest project is adding a standardized "Deans" T-Plug connector at the motors. This will make possible a 5 minute, tube replacement, rear wheel swap, etc., previous time, 1/2hour, or longer.

My next voltage upgrade will be 44.4v* on an AmpedBikes front hub, then, I will probably push it to, the newly capable 60v.

* 44.4v is extremely simple, from my supply of 11.1v 6packs of Lipo. I have 11.1v 500ah+ Lipo stockpiled (1/2 are SONY matched cells!). All charge to full, and maintain voltage.
55.5v is easier than 48.1v, but uneven, for my saddlebag design plan.

 

[neptronix]

If you're going to do 12s later on, get the 48v meanwell and do the shunt clip mod i did ( see the last pages of my trek build ), the amperage is perfect for 12s.

The 48v meanwell can adjust to 50v, with the shunt clip it is putting out 6.675 amps for me, that's ~330 watts which is just a bit under it's max rating and i reckon that would be perfect for you.

Or you can do the resistor mod, it doesn't matter.

And an ampedbikes DD hub at 44v nominal should do upper 20mph.. go for it.. it will be a massive improvement over your fleet of eZips even at the stock amperage.

Look into the cell_man kit though, it consists of the same parts. And is dirt cheap in comparison, should be under $250 shipped to the east coast.

Hey, look at you now.. lipo.. direct drive hubs.. hang out in a barber shop long enough and you're gonna get a haircut.. :lol:

 

[DrkAngel]

I've been "equalization testing", to determine getting better, maintaining or getting worse, on my Li-ion & Lipo homemade packs for a couple weeks now.
My preliminary testing was solely for non-pedal assist range.
Results:
Li-ion 25.9v - 31.2 ah 50miles+ at 18mph average level cruising pace.
Lipo 25.9v - 26 ah 40miles+ at 18mph average level cruising pace.

Equaliziation - monitored charging, (w/Tenergy Li-ion-Lipo charger $23.62), 10 cycles, (5 cycles each)
All cells, both packs remained within about 1/100v of 4.18v!

Equalization testing has been done with my normal pedal assist mode.
For the Li-ion, (18650 cells), I typically recharge every 30-35 miles.
For the Lipo, I typically recharge every 25-30 miles.

Of course, I tend to cruise at 20mph+, But attack hills, and sprint ahead of traffic - motor and pedal combined gives me almost a block, from a red light, till traffic catches up.
Sprints on the level are starting to give me an endorphin rush!
I get up to near 30mph, impressive, since motor assist fades at 23mph, and ends at 25mph.
I try to, daily, get my 5 block "rush", maybe 1/2 mile. (potholed side streets make main drag advisable!)

Finally getting back in shape, after my "range trials".

I feel that eaBikes" Electric Assist Bikes", are best used to enhance my biking ability ... not replace it!

 

[Ypedal]

you keep using the term equilization with that tenergy charger, and this is fundamentally wrong, readers of this thread need to understand that your charger is not equilazing or ballancing or doing any of that.... it simply charges the whole pack to a set voltage.. that's it...

Luke has tried to explain this to you, many times over, and you insist on testing something that is already known, nothing wrong with you enjoying your pack, and reporting findings, but let's be clear on something.. your tenergy charger is not ballancing the pack

 

[DrkAngel]

you keep using the term equilization with that tenergy charger, and this is fundamentally wrong, readers of this thread need to understand that your charger is not equilazing or ballancing or doing any of that.... it simply charges the whole pack to a set voltage.. that's it...

Luke has tried to explain this to you, many times over, and you insist on testing something that is already known, nothing wrong with you enjoying your pack, and reporting findings, but let's be clear on something.. your tenergy charger is not ballancing the pack

Never claimed it was "ballancing"!
Merely pointed out, that it was - maintaining equalization!
Without a BMS/PCB/PCM, or, balancing charger.

In fact, I clearly state that it is not a perfect balance and is not improving!
Which would mean, that I am not even, implying, that it is a balancing charger!

 

[icecube57]

Everybody Calm Down.

 

[neptronix]

you keep using the term equilization with that tenergy charger, and this is fundamentally wrong, readers of this thread need to understand that your charger is not equilazing or ballancing or doing any of that.... it simply charges the whole pack to a set voltage.. that's it...

Luke has tried to explain this to you, many times over, and you insist on testing something that is already known, nothing wrong with you enjoying your pack, and reporting findings, but let's be clear on something.. your tenergy charger is not ballancing the pack

+1, that's the reason i jumped on here.

According to merriam-webster.com:

Definition of EQUALIZE

transitive verb
1 : to make equal
2 : to compensate for

Synonyms: balance, equate, even, level

Equalizing sounds a lot like balancing to me.

Might indicate a balancing algorithm?
Charge-discharge-charge-discharge - cycles every 2-3 seconds.
Premise 1 - A lower voltage cell will accept charge more easily than one with a higher voltage.
Premise 2 - A higher voltage cell will expend energy more easily, (faster), than lower voltage cell.
Given these 2 reasonable premises, then the chargers, charge-discharge pulsing, would tend to equalize, (balance), Li-ion cells!

Immediately after you said this,. we jumped on you and you resisted the idea that your charger isn't capable of doing any sort of balancing, or uhh, equalizing.

Lithium-ion Polymer 25.9v, 26ah pack charged nicely, also!
All banks of cells charged tightly within 1/100th of a volt, of the median 4.18v!

Previously described, "off balance" pack test, scheduled for Tuesday, when I'm back in the shop.

But you didn't go through with it because it sounds like you may have learned that your charger won't do what you thought..

Immediately after you said this, this thread was created by someone excited about your newfound cheap balancing charger:

http://endless-sphere.com/forums/viewtopic.php?f=14&t=28496

This is why we ding people for posting incorrect info. Happens to the best of us.. myself included. It's ok to correct yourself and move on. I haven't seen anyone be eternally hated on this board for being wrong once. Just sayin.

 

[DrkAngel]

Tenergy 25.9v Li-ion charger report:
I decide that the most relevant test would be the maintenance of voltage equalization after repeated deep cycles.
Packs are discharged into the 3.7*v range. (3.5v under moderate throttle)
Further tests will follow.

Most important, real world application test, not completed yet.

 

[DrkAngel]

+1, that's the reason i jumped on here.

According to merriam-webster.com:

Definition of EQUALIZE

transitive verb
1 : to make equal
2 : to compensate for

Synonyms: balance, equate, even, level

Equalizing sounds a lot like balancing to me.

My lipo cells come out equalized after dozens of non-balance charges too, only because they a set of matched cells in the first place.

OOPS! ... Can you say ... hypocrite?

 

[neptronix]

Oh my god... :lol: :lol: :lol:

I see we are not getting anywhere here, so i'm going to step out for now.