Homemade Battery Packs

Batteries, Chargers, and Battery Management Systems.
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liveforphysics
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Re: Homemade Battery Packs

Post by liveforphysics » Aug 29, 2011 7:09 pm

Do you ride a 250w bike or something? lol
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Re: Homemade Battery Packs

Post by amberwolf » Aug 29, 2011 8:25 pm

miniebiker wrote:Why would anyone want to use cheap made in China batteries to build a homemade battery pack ?
The original source of many of the cells in various laptops, toolpacks, etc., is quite likely China, regardless of what company "makes" or sells the packs the cells themselves are in. ;)

So even making your own battery pack out of cells from other packs doesn't guarantee you're not using those "cheap made in China batteries", unless you specifically use only those cells that you can absolutely trace the origin of back to their original factory, to ensure it is from the place you're wanting them to be from, and the level of quality you want them to be.

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Re: Homemade Battery Packs

Post by miniebiker » Aug 29, 2011 9:05 pm

amberwolf wrote:
miniebiker wrote:Why would anyone want to use cheap made in China batteries to build a homemade battery pack ?
The original source of many of the cells in various laptops, toolpacks, etc., is quite likely China, regardless of what company "makes" or sells the packs the cells themselves are in. ;)

So even making your own battery pack out of cells from other packs doesn't guarantee you're not using those "cheap made in China batteries", unless you specifically use only those cells that you can absolutely trace the origin of back to their original factory, to ensure it is from the place you're wanting them to be from, and the level of quality you want them to be.
So far all the packs I have seen said country of origin and where they were put together.

The packs all say assembled in China.

Cell origin says either Japan, Korea or China cells.

The ones I have that tested best said made in Korea, are pink and say Samsung on them.

I found a data sheet for them too. :)

The cheap ones I was talking about are the no name ones LP was suggesting DA get his name on ? :)

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Re: Homemade Battery Packs

Post by miniebiker » Aug 29, 2011 9:14 pm

liveforphysics wrote:Do you ride a 250w bike or something? lol
It is important to know how many watts you need when you build a homemade battery pack.

It is also important to read the data sheets from the factory on the batteries being used.

It is also important to test the batteries so they can be matched.

Know what your batteries can do so you can build a pack that will go the distance and not get hot or run out. :)

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Re: Homemade Battery Packs

Post by miniebiker » Aug 29, 2011 9:18 pm

DrkAngel wrote:This is the chart that matters most ... to me!
Capacity-1A.png
My typical usage! With my 25.9v - 31.2ah Li-ion battery pack, only 9 lbs.
My testing so far discharging at 1 amp shows very good performance with little temp rise.

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Re: Homemade Battery Packs

Post by DrkAngel » Aug 29, 2011 9:26 pm

liveforphysics wrote:Do you ride a 250w bike or something? lol
450w EZip - cruising at 18-20mph.
25.9v, 31.2ah Li-ion (homemade) pack = 50+ miles per charge, cruising about 3 hours @ 18+ mph, motor only - no pedal assist.
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There, shallow draughts intoxicate the brain,
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Re: Homemade Battery Packs

Post by miniebiker » Aug 30, 2011 3:00 pm

DrkAngel wrote:
liveforphysics wrote:Do you ride a 250w bike or something? lol
450w EZip - cruising at 18-20mph.
25.9v, 31.2ah Li-ion (homemade) pack = 50+ miles per charge, cruising about 3 hours @ 18+ mph, motor only - no pedal assist.
With a 9 lb battery and a 5.5 lb motor. And a bullet proof brushed motor too ! That's what I'm talkin about ! :)

A setup that total would add 25lbs or less to the weight of a bicycle and go 50+ miles on a charge. :)

http://tncscooters.com/product.php?sku=106118

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Re: Homemade Battery Packs

Post by DrkAngel » Sep 29, 2011 8:07 am

Homemade packs are working nicely.
I've gone about 1000 miles, using just my 25.9v recycled Lipo, in EZip, pack.
I've been using my Li-ion builds, for the past 3 years, thought I should concentrate on testing the Lipo.
My first Lipo builds were built from the "defective" packs, the ones that would not properly charge in the 4 bay laptop, bulk, charger.
25.9v.

The good news?
I have 200+ "good" packs, that fully charge, and more importantly, maintain 80% charge after sitting for 3 months!
(4 of 5 capacity meter leds)
4-5 kWhs of SONY cells (only tested at 11.1v 21.6ah, with 110v AC inverter, then replacing 2 - 6v cells in 12V florescent lantern.)
7-8 kWhs of unlabeled cells
No where near as cheap as Li-ion, but typically in much better condition, (Higher percentage of 100% usable)

For my ebike packs, I leave the individual cell fuses.

For my 18v B&D (Black & Decker) Power tool pack upgrades, I will bypass the built in fuses.
Of course I will closely monitor, as I apply maximum demand, during durability testing.
I'm guessing the 8" chainsaw should demonstrate the highest demand.
Testing will use an amp meter between the tool and an external pack, (temperature monitored , of course!)

Still shopping for eMotorcycle ... and eCar candidates-components ...
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 04, 2011 8:43 am

SamTexas wrote:
DrkAngel wrote:... a digital voltage meter ... capable of measuring 1/100ths volt!
Which one is that? How accurate is it?
I'm looking for one that can also accurately measure mV with 2 decimal digits, e.g. 5.23mV.
Most all digital meters will read 100th volt.
Only way to verify accuracy is comparison against "known" good, or "Standards" certification.

Never had any use for 5.23mV accuracy. (.00532 V) 100,000th V
Last edited by DrkAngel on Oct 06, 2011 7:07 am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Index - Homemade Battery Packs - Updated - November 2015

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Re: Homemade Battery Packs

Post by SamTexas » Oct 04, 2011 8:57 am

DrkAngel wrote:... a digital voltage meter ... capable of measuring 1/100ths volt!
Which one is that? How accurate is it?
I'm looking for one that can also accurately measure mV with 2 decimal digits, e.g. 5.23mV.

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 06, 2011 7:08 am

Cell capacity-condition easy "quick check" ...

After evaluating hundreds & hundreds of cells, I noticed that the best cells were the ones with the "best" bleed down profiles.
Typically I charged all cells to a 4.2v resting voltage.
With a quick charger, the finish voltage must be slightly higher to attain this "resting" voltage.
My standard procedure was to confirm 4.2v, after 1 hour removal from charger.

Then ...
Voltage, of each cell is tested, and recorded at 24 hour intervals.
1 week of testing gives a very good cell evaluation, I use this method to compare cells of same manufacture and capacity.
Initial voltage drop seems to give a good indicator of capacity-condition.
This method seems fairly reliable for Li-ion, as well as for Lipo.
I have used this "yardstick" method to match cells for my larger pack builds, (84 - 120 cell packs), with good success.

Taking this method, to the next level, I intend to do my future cell matching, using a preliminary cell voltage of 4.25v.
While towards the high end of acceptable charge, daily "bleed down", should earmark the very best cells, (The ones closest to brand new condition), indicated by the 1st 24 hour voltage drop.

Typically I try to parallel together a dozen cells, or more, then "gang charge" to specified voltage, before separation and testing.

Oh! It is important to have a digital voltage meter ... capable of measuring 1/100ths volt!

Stay tuned for my 44 Magnum!

The Lipo packs I recycle, are nicely built in 3S, 11.1v, "bricks".
It has been bothersome adding 1S, to build 7S 25.9V and 10S 37V packs.
Fortunately, a 12S 44.4V pack charges nicely to 50.4V.
The 48V controllers, I've been eying, have low voltage cutoffs of 41V & 42V ...
41V / 12S =3.4V
42V / 12S = 3.5V, which is my personally recommended, optimal DOD (Depth Of Discharge)!
Update: Optimal DOD revised to 3.7+V (Li-ion - LiCo 18650 cells)
3.5V per cell, low voltage cut-off, should work nicely for 3.7+V minimum, actual, discharge. ("Voltage sag" under throttle.)

Test pack will use 2160mah cells, in a 12S 10P configuration. (.96kWh)
44.4V - 21.6ah
Which can be easily paired with Twin Sister Pack for 1.92kWh pack.
44.4V - 43.2ah
Yeah ... I stocked up on cells!

Initial charging will be done with multiple iMax B6 as 22.2V sub-packs,
or ... slower ... 22.2V dual charging from single charger.
Last edited by DrkAngel on Apr 06, 2014 9:33 am, edited 2 times in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 07, 2011 8:44 am

DrkAngel wrote: Stay tuned for my 44 Magnum!

The Lipo packs I recycle, are nicely built in 3S, 11.1v, "bricks".
It has been bothersome adding 1S, to build 7S 25.9V and 10S 37V packs.
Fortunately, a 12S 44.4V pack charges nicely to 50.4V.
The 48V controllers, I've been eying, have low voltage cutoffs of 41V & 42V ...
41V / 12S =3.4V
42V / 12S = 3.5V, which is my personally recommended, optimal DOD (Depth Of Discharge)!
Update: Optimal DOD revised to 3.7+V (Li-ion - LiCo 18650 cells)
3.5V per cell, low voltage cut-off, should work nicely for 3.7+V minimum, actual, discharge. ("Voltage sag" under throttle.)
!
Test pack will use 2160mah cells, in a 12S 10P configuration. (.96kWh)
44.4V - 21.6ah
Which can be easily paired with Twin Sister Pack for 1.92kWh pack.
44.4V - 43.2ah
Yeah ... I stocked up on cells!

Initial charging will be done with multiple iMax B6 as 22.2V sub-packs,
or ... slower ... 22.2V dual charging from single charger.
My initial use will be on my 24V EZips ...
Running a 24V motor at 44V might seem like a good way to burn up it up?
There are many stories of these motors being burnt up, running at 36V.
Some have gone to extravagant measures of, cooling, ventilation etc.

Well ... I do not propose this option as an uninformed or lightly considered manner.
I have run multiple bikes at 37V, for thousands of miles, with no problems.
My key to motor 'survival" is not additional cooling, it is prevention of heat production!
Full throttle draw at a dead stop is 30+ Amp, full throttle at top speed is 10- Amps.
Full throttle at 5mph might produce 80% waste heat and 20% usable power.
DC motors seem to have an efficiency range, this range moves - dependent on throttle position.
Throttle, "effectively", regulates the voltage to the motor, the "efficiency range" of the motor seems to be in the 50-80+% of top speed, nearing 80%+ efficiency & 20%- wasted heat.

With the EZip 24V:
Throttle % : Equiv. V : Max mph : Best Pwr
....25...........6V.......... 5....... 3-4 mph
....50...........12V.........10.......5-8 mph
....75...........18V.........15...... 7-12 mph
...100...........24V.........20......10-16 mph

With the EZip 44.4V:
Throttle % : Equiv. V : Max mph : Best Pwr
....14...........6V..........5.........3-4 mph
....27..........12V.........10.........5-8 mph
....40......... 18V..........15........7-12 mph
....45......... 24V..........20 .......10-16 mph
....67..........30V......... 25........13-19 mph
....81......... 36V..........30........15-24 mph
....90 .........40V..........35........18-30 mph
...100......... 44.4V.......39 **......20-35 mph

As long as the throttle is regulated and the motor kept in the efficiency groove, heat should be manageable.

24V full throttle at 5mph (80% wasted heat)
Should prove much more damaging than -
44.4V full throttle at 30 mph (20% wasted heat)
44.4V full throttle, @ 30mph, produces less than 1/2 the heat as 24V full throttle @ 5mph!

Moderate initial throttle, combined with pedal-assist, keeps my motors in the pink, (moderate temperature).

Personally, I have difficulty understanding eBikers that pump more and more amps into their motors.
2x the amps might produce 50% more low speed torque, but it also produces 300% of the damaging heat.
With only a slight, if any, increase in top speed.
But that might just be my frugal spirit being offended by the speed, sorry, power demons!

** "Max Mph" does not reflect wind resistance! Still ... 44.4V should produce 30++ mph!
37V provides 27mph, with pedal assist, past 30mph.
Last edited by DrkAngel on Apr 06, 2014 9:34 am, edited 5 times in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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Re: Homemade Battery Packs

Post by alsmith » Oct 07, 2011 12:59 pm

It's good to have a plan- I hope it works for you. Why not fit a temperature probe in the motor by the windings so you can watch what is happening- it seems sensible given the feedback on overvolting these motors, and the probes aren't too expensive. I got one to fit into my motor so I can see what happens for peace of mind. It's an overcautious step for me but better to be safe.....
DrkAngel wrote:
DrkAngel wrote: Stay tuned for my 44 Magnum!

The Lipo packs I recycle, are nicely built in 3S, 11.1v, "bricks".
It has been bothersome adding 1S, to build 7S 25.9V and 10S 37V packs.
Fortunately, a 12S 44.4V pack charges nicely to 50.4V.
The 48V controllers, I've been eying, have low voltage cutoffs of 41V & 42V ...
42V / 12S = 3.5V, which is my personally recommended, optimal DOD (Depth Of Discharge)!
Test pack will use 2160mah cells, in a 12S 10P configuration. (.96kWh)
44.4V - 21.6ah
Which can be easily paired with Twin Sister Pack for 1.92kWh pack.
44.4V - 43.2ah
Yeah ... I stocked up on cells!

Initial charging will be done with multiple iMax B6 as 22.2V sub-packs,
or ... slower ... 22.2V dual charging from single charger.
My initial use will be on my 24V EZips ...
Running a 24V motor at 44V might seem like a good way to burn up it up?
There are many stories of these motors being burnt up, running at 36V.
Some have gone to extravagant measures of, cooling, ventilation etc.

Well ... I do not make this decision as an uninformed or lightly considered option.
I have run multiple bikes at 37V, for thousands of miles, with no problems.
My key to motor 'survival" is not additional cooling, it is prevention of heat production!
Full throttle draw at a dead stop is 30+ Amp, full throttle at top speed is 10- Amps.
Full throttle at 5mph might produce 80% waste heat and 20% usable power.
DC motors seem to have an efficiency range, this range moves - dependent on throttle position.
"Throttle", effectively, regulates the voltage to the motor, the "efficiency range" of the motor seems to be in the 50-80+% of top speed

With the EZip 24V:
Throttle % : Equiv. V : Max mph : Best Pwr
....25...........6V.......... 5....... 3-4 mph
....50...........12V.........10.......5-8 mph
....75...........18V.........15...... 7-12 mph
...100...........24V.........20......10-16 mph

With the EZip 44.4V:
Throttle % : Equiv. V : Max mph : Best Pwr
....14...........6V..........5.........3-4 mph
....27..........12V.........10.........5-8 mph
....40......... 18V..........15........7-12 mph
....45......... 24V..........20 .......10-16 mph
....67..........30V......... 25........13-19 mph
....81......... 36V..........30........15-24 mph
....90 .........40V..........35........18-30 mph
...100......... 44.4V.......39 **......20-35 mph

As long as the throttle is regulated and the motor kept in the efficiency groove, heat should be manageable.

24V full throttle at 5mph (80% wasted heat)
Should prove much more damaging than -
44.4V full throttle at 30 mph (20% wasted heat)

Moderate initial throttle, combined with pedal-assist, keeps my motors in the pink, (moderate temperature).

Personally, I have difficulty understanding eBikers that pump more and more amps into their motors.
2x the amps might produce 50% more low speed torque, but it also produces 300% of the damaging heat.
With only a slight, if any, increase in top speed.
But that might just be my frugal spirit being offended by the speed, sorry, power demons!

** "Max Mph" does not reflect wind resistance! Still ... 44.4V should produce 30++ mph!
37V provides 27mph, with pedal assist, well past 30mph.

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 07, 2011 2:27 pm

alsmith wrote:It's good to have a plan- I hope it works for you. Why not fit a temperature probe in the motor by the windings so you can watch what is happening- it seems sensible given the feedback on overvolting these motors, and the probes aren't too expensive. I got one to fit into my motor so I can see what happens for peace of mind. It's an overcautious step for me but better to be safe.....
44.4V Magnum
I've put 3000 miles, @37V, on one motor ... will try to "burn-it-up", as my test bed.
I have 3 new, spares.

No ... I won't really try to kill it ... but not going to treat it any nicer than "my" usual.

My EZip goal is, melding smoothly with local 30mph traffic.
No need to go any faster than that.

Beyond that will be my eMotorcycle project ...
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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Index - Homemade Battery Packs - Updated - November 2015

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 08, 2011 8:50 am

44 Magnum - TURBO

Possibly, just so that I could add the Turbo moniker, I'm resurrecting one of my older ideas.

The implementation of an additional throttle return spring.
Preliminary idea, was a method of regulating top speed, as could be used for seniors, on a motorized tricycle designed as a mobility device.
A simple set screw on the throttle could suffice.
Next stage was the possibility that instead of a "stop" screw, a heavy spring could engage at a specific throttle position.
Logically, I could set this point where "legal" 20mph cruising is provided, (about 24V equivalent).
Beyond that point, additional required effort would serve as a firm reminder that throttle "Turbo" should only be used in emergencies ... or when cops aren't looking.

Alternately, I could "switch" a proper value resister into the HALL throttle circuit.
A simple switch, or even an appropriately labeled, TURBO momentary contact button, could bypass the resister and provide the same function!
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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Re: Homemade Battery Packs

Post by jamo96 » Oct 09, 2011 5:11 am

Here are a couple of battery packs I've made recently. They are 14s 5000mah Turnigy 20c lipo contained in a 150mm x 150mm x 75mm enclosure. They fit very well. I have soldered a harness so that 2 x 7s jst-xh plugs are available from the outside for balancing on my hyperion charger. So gives me a total of ~55V 10Ah.

Finished pack. Contains two 3s and two 4s packs.
Image

Image

Unfinished pack. Contains four 3s packs and is missing a 2s pack (its in the post)
Image

Image

With the Cell Logs connected.
Image

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Re: Homemade Battery Packs

Post by bobale » Oct 09, 2011 6:24 am

I must say, that looks super-neat!
RWD 2807 9Continent rolling on Kenda Flame 26x2.125
12S3P out of Turnigy 4S Hardcase 20C (600Wh)
35A 9FET Infineon Controller (Regen, Cruise control, Speed limit)
Top Speed 27mph (31mph@120%)

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Re: Homemade Battery Packs

Post by SamTexas » Oct 09, 2011 7:17 am

Nice box. Where did you buy that box? Is it an electrical junction box?

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Re: Homemade Battery Packs

Post by jamo96 » Oct 09, 2011 7:35 am

Yes I very happy with the way they turned out. The batteries fit very nicely inside the boxes. I had 15s in there initially but went back to 14s for my charger. They are just general electrical termination boxes from B & R:

http://www.brenclosures.com.au/pj.htm

They were about $15 each from a local electrical supplier. Can probably find them cheaper online somewhere.

Probably should have just made two 7s 10Ah packs but they were not made at the same time. But overall very happy!

Improvements: Need to think of someway to mount the cell logs better, possibly add an LVC alarm output and maybe a temp sensor.

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Re: Homemade Battery Packs

Post by DrkAngel » Oct 11, 2011 8:53 pm

25.9V Li-ion - Lipo chargers - available again!
Free shipping on $75 order w/code: "THANKS"
Tenergy Intelligent 2A Charger for 25.9V - $23.63 Works fine with, all I've tried, 24V EZip-IZips, probably all 24V controllers?

I also got 1 - 18.5V 2.5A Lipo charger, for charging 18V B&D power tool pack, lipo conversions, about same price.
Tenergy Intelligent 2.5A Charger for 18.5V - $22.81
Last edited by DrkAngel on Oct 12, 2011 8:46 pm, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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Re: Homemade Battery Packs

Post by pavlik1 » Oct 12, 2011 3:36 am

Here is one more, not quite finished yet.
the box
Image
the bat
Image

Image

Image

Image

Image

Image

looking for BMS

16s app 20Ah
Weight 9.8kg
1st old radiator fan motors, 20km/h - stolen after 2 days - no pictures
2nd 250W-24V eZiplike motor with gear. running on 36V, 8Ah, peak 1000W, 40km/h. Just disassembled (running again)
3th GM 48V 1000W, running with 16S 20Ah WinForce Lipo. different controllers, speed over 72km/h - LiPo FIRE
4th Recumbent HS3540 2X16s 48V 20Ah
5th full suspension Haibike Attack FX, running with e-novation M15 16S 10Ah LiFePo4 or 13S LiIon
6th Hardtail alu 26'' with e-novation M15 10S, VESC and throttle

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Recycled Lipopackpatchjob

Post by DrkAngel » Oct 22, 2011 9:49 pm

My 25.9V 26Ah recycled Lipo EZip build has been doing great for the last 1000+ miles!
Finally, it developed a voltage fluctuation on 1 bank.
So I desoldered one leg of the parallel, and put a one amp draw on the individual pairs.
It was easy to find the weak cells, right on top of my "A" stack.
Replacement would be very simple, but I wanted to try one of my experiments.
Since the voltage variance was fairly minor I figured one additional cell on the 12P bank, should equalize things nicely.
Image
Well, everything is packed pretty snug, no room for another lipo cell.
So ... I wired a single 18650 Li-ion cell into the weak bank, and placed it on the lower side-6pack.

Result:
After 2 charge-discharge cycles pack is back in balance. within 1/100th at the high and low voltages.

Of course I will, eventually replace the weak cells, but 1st, I have to give the Lipopackpatchjob a proper trial.

Which might help me seriously consider the option of building larger packs with spare cells built-in.
The spare cells would be part of the pack, but not wired in-circuit.
If one bank suffers, an additional cell could be easily tacked in.
Or, bad cells clipped out and the replacements clipped in.
A quick fix for longer trips, or when shop not available.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

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DrkAngel
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Re: Homemade Battery Packs

Post by DrkAngel » Oct 23, 2011 10:50 am

DrkAngel wrote:Sorry, this is the raw data of my monitored discharge test.
Will graph later, but wanted to post the results.

Quick stats on mAh per 100th V.
Li-ion (LiCo) 2600mAh used cells.
Charged to 4.25V
.2C discharge rate
..V... mAh
4.23V .. 4
4.22V .. 5
4.22V .. 6
4.20V .. 9
4.19V .. 18
4.18V .. 37
4.17V .. 38
4.16V .. 38
4.15V .. 38
4.14V .. 38
4.13V .. 38
4.12V .. 38
4.11V .. 40
4.10V .. 40
4.09V .. 42
4.08V .. 43
4.07V .. 44
4.06V .. 44
4.05V .. 44
4.04V .. 42
4.03V .. 43
4.02V .. 42
4.01V .. 43
4.00V .. 44
3.99V .. 44
3.98V .. 43
3.97V .. 45
3.96V .. 46
3.95V .. 45
3.94V .. 45
3.93V .. 47
3.92V .. 48
3.91V .. 47
3.90V .. 45
3.89V .. 43
3.88V .. 42
3.87V .. 44
3.86V .. 45
3.85V .. 57
3.84V .. 57
3.83V .. 78
3.82V .. 82
3.81V .. 86
3.80V .. 88
3.79V .. 89
3.78V .. 86
3.77V .. 94
3.76V .. 98
3.75V .. 103
3.74V .. 102
3.73V .. 105
3.72V .. 120
3.71V .. 125
3.70V .. 100
3.69V .. 100
3.68V .. 100
3.67V .. 78
3.66V .. 74
3.65V .. 72
3.64V .. 74
3.63V .. 72
3.62V .. 71
3.61V .. 70
3.60V .. 45
3.59V .. 43
3.58V .. 43
3.57V .. 24
3.56V .. 20
3.55V .. 20
3.54V .. 20
3.53V .. 17
3.52V .. 14
3.51V .. 12
3.50V .. 10

Output is reasonably steady from about 4.18V till 4.1V.
Slowly increases from 4.1V till 3.85V
Then increases sharply from 3.85V till it peaks around 3.7V.
Below 3.7V output decreases rapidly till it reaches minimum usable at 3.6V.

Based on these figures:
For Li-ion (LiCo),
Charge-discharge voltages should be,
Maximum 4.18V
Minimum 3.6V

3.85V to 3.65V is the muscle bulge of the discharge curve.
To take full advantage of this "bulge" I would recommend "bottom balancing", at 3.65V.

Charging above 4.2V is worthless, and unnecessarily damaging.
Same for discharging below 3.6V.
Image
Notes:
Monitored discharge was done with an iMax B6.
iMax B6 voltage readings were not used, voltage was determined by meter directly on battery.
The iMax displayed a noticeable voltage sag, that varied at different points of the discharge.
The meter flip-flopped between voltages as the voltage dropped, I marked the point when lower voltage was constant for 10 continuous seconds.

Be aware! These results are for a specific cell type-formulation and might have no relation to other brands-types-formulations!

Recycled Lipo will be tested next.
New RC Lipo after that.
Maybe SLA ... for a laugh!

Smoothed the graph, to moderate ... human error ... ?
Image
Last edited by DrkAngel on Oct 30, 2011 12:10 am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

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User avatar
DrkAngel
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Re: Homemade Battery Packs

Post by DrkAngel » Oct 27, 2011 5:24 am

DrkAngel wrote: Stay tuned for my 44 Magnum!

The Lipo packs I recycle, are nicely built in 3S, 11.1v, "bricks".
It has been bothersome adding 1S, to build 7S 25.9V and 10S 37V packs.
Fortunately, a 12S 44.4V pack charges nicely to 50.4V.
The 48V controllers, I've been eying, have low voltage cutoffs of 41V & 42V ...
41V / 12S =3.4V
42V / 12S = 3.5V, which is my personally recommended, optimal DOD (Depth Of Discharge)!
Update: Optimal DOD revised to 3.7V+ (Li-ion - LiCo 18650 cells)
3.5V per cell, low voltage cut-off, should work nicely for 3.7V+ minimum, actual, discharge. ("Voltage sag" under throttle.)

Test pack will use 2160mah cells, in a 12S 10P configuration. (.96kWh)
44.4V - 21.6ah
Which can be easily paired with Twin Sister Pack for 1.92kWh pack.
44.4V - 43.2ah
Yeah ... I stocked up on cells!
mAh per 100th Volt graph, prompted revision to 3.6V maximum DOD! (18650 LiCo cells)
Image
Last edited by DrkAngel on Apr 06, 2014 9:38 am, edited 1 time in total.
A little learning is a dangerous thing;
Drink deep, or taste not the Pierian spring:
There, shallow draughts intoxicate the brain,
And drinking largely, sobers us again.

I enjoy enlightening ... and enlivening the spirit of the innovators.

New & Improved - Acronym Definitions

Index - Homemade Battery Packs - Updated - November 2015

EBike Toolbox - Bargains! $

Endless Sphere Wiki

Kin
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Re: Homemade Battery Packs

Post by Kin » Oct 27, 2011 10:18 am

Just wondering if you got the PM I sent asking about tips for sourcing used LiPo. Was looking over at RCgroups, thinking they might have some stuff (but a lot of it is excessively high C rating or excessively low Mah).
New to endless-sphere? Notice a lot of signatures recommending Ebikes.ca? That's because it's the best place for a quality and manageable, (but still 'real'), first build. Justin is a solid supporter of electric bike development, and a good source of equipment.

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