Homemade Battery Packs

[neptronix]

They generally all do that.
The celllog 8s draws power from 6 of 8 cells, but can be modified to draw from all 8. May be an interesting alternative.

The problem with these units is that you have to repeatedly connect and disconnect them if you don't want them killing your first couple cells. Same problem with 95% of the BMSes on the market out there.

This is why i prefer to use LVC on my controller. I am surprised that nobody has came up with a standalone LVC unit that uses a DC-DC converter to power it.

[DrkAngel]

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm
24hr report:
4.32ah battery
Drained .1v - 24 hours
Draws power from S1 and S2 only
.1v might not seem like much, but that is more than 10% capacity of 2 banks, which would lower entire pack usable by 10%
Of course, with a 20ah pack, that would be a mere 2% per day ...

Still, I would have to recommend, that item should be used only during pack usage, or to check pack occasionally.

A switch or momentary contact button, on neg pin, would easy on-off or allow quick check.

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm RC 1S - $3.29 w/shipping

[neptronix]

Negative pin would still allow for a bit of draw. The question is, how much.
I know you haven't been on ES too long, but i have seen the negative pin thing not work many times in a lot of threads.

Real unfortunate. We need a BMS or LVC unit that only turns on *when the bike power is on!!!*, novel concept right?

This is why i gave up on the idea of constant per cell level LVC / monitoring early into my build. So i just chop a little voltage off the top and bottom of my charges.

[Floont]

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm
24hr report:
4.32ah battery
Drained .1v - 24 hours
Draws power from S1 and S2 only
.1v might not seem like much, but that is more than 10% capacity of 2 banks, which would lower entire pack usable by 10%
Of course, with a 20ah pack, that would be a mere 2% per day ...

Still, I would have to recommend, that item should be used only during pack usage, or to check pack occasionally.

A switch or momentary contact button, on neg pin, would easy on-off or allow quick check.

Wow, DrkAngel; That device looks great! Where can I buy it? Do you have a link? How much does it cost?

FA

[DrkAngel]

Great new price on, 1-8S Lipo Battery Tester Low Voltage Buzzer Alarm. $3.29 w/shipping
Half the price of previous best price! I ordered another 5.

Displays total voltage and well as that of individual cell-bank.
Programmable low voltage alarm, audio-visual. (2.7-3.8v)

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm RC 1S - $3.29 w/shipping

$3.29
Note: Claims accurate to within 1/100th Volt, actual, from several, is a few 100ths.
Total voltage accurate, cell accuracy varies.

I use one as an "on bar" volt-fuel gauge. Rigged into throttle, (voltage to battery level leds).
Up to 30v 1S meter, just attach to neg - pin 1 and pin 2.
Use multiple to monitor, larger than, 8S packs.

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm
24hr report:
4.32ah battery
Drained .1v - 24 hours
Draws power from S1 and S2 only
.1v might not seem like much, but that is more than 10% capacity of 2 banks, which would lower entire pack usable by 10%
Of course, with a 20ah pack, that would be a mere 2% per day ...

Still, I would have to recommend, that item should be used only during pack usage, or to check pack occasionally.

A switch or momentary contact button, on neg pin, would easy on-off or allow quick check.

[neptronix]

Is there an echo in here?

[Floont]

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm RC 1S - $3.29 w/shipping

Thanks,DkAngel for correcting yhe link.

FA

[liveforphysics]

Those devices are what's known as a battery-unbalancer.

[neptronix]

^-- lol, yup

[Floont]

Why would they do that?

Sorry, lipo no0b here. (Ask me about SLA's and I'll talk your ear off; and yes, SLA's are not fashionable and eventually I will be ditching them).

FA

[DrkAngel]

Those devices are what's known as a battery-unbalancer.

Why would they do that?

Sorry, lipo no0b here. (Ask me about SLA's and I'll talk your ear off; and yes, SLA's are not fashionable and eventually I will be ditching them).

FA

The meter draws power from S1 and S2 only, (bank 1 & 2).
Good condition Li-ion - Lipo tend to discharge and recharge at a fairly constant rate.
Meaning?
A Li-ion Lipo pack will discharge-recharge back to the same "equalized" voltage, (all cells same voltage), without a balance-equalization device.
An alternate draw on 2 banks will cause those 2 banks to recharge to a slightly lower voltage, every cycle becoming worse.
Unless ... you use a balance-equalization charger.

[Floont]

Why would they do that?..

The meter draws power from S1 and S2 only, (bank 1 & 2)...An alternate draw on 2 banks will cause those 2 banks to recharge to a lower voltage, every cycle becoming worse...

Thanks for the explanation.
I feel like rushing right out and purchasing an arm-full of them.

[DrkAngel]

Those devices are what's known as a battery-unbalancer.

Why would they do that?

Sorry, lipo no0b here. (Ask me about SLA's and I'll talk your ear off; and yes, SLA's are not fashionable and eventually I will be ditching them).

FA

The meter draws power from S1 and S2 only, (bank 1 & 2).
Good condition Li-ion - Lipo tend to discharge and recharge at a fairly constant rate.
Meaning?
A Li-ion Lipo pack will discharge-recharge back to the same "equalized" voltage, (all cells same voltage), without a balance-equalization device.
An additional draw on 2 banks will cause those 2 banks to discharge and recharge to a lower voltage, every cycle becoming worse.
Unless ... you use a balance-equalization charger.

Of course, if only on during battery usage, (20ah pack), it would take a dozen cycles to produce a 1% variance.
I would certainly recommend an equalization at least that often.

Note: When used as a voltage meter only, voltage draw is over entire pack, and of insignificant drain.
If wired into throttle meter LED voltage, it will disengage when power to controller is disconnected.
Voltage limit, in this mode is only 30v.
Great for OEM SLA, Lipo - Li-ion up to 25.9v, LiFe, Nimh etc

[Floont]

...If wired into throttle meter LED voltage, it will disengage when power to controller is disconnected...

Hm. That actually seems clever.

FA

[DrkAngel]

Balancing-charging a 8S-10S-12S LI- pack!
Found a nice little item that allows 1 step charging-balancing of larger Li-ion Lipo etc. packs, from a 6S charger.
5pcs XH 6S to 2XH 6S Silicone Wire 22AWG

6-12balance.JPG (29.24 KiB) Viewed 1255 times

Simply split pack int equal halves, 12S into 2-6S, etc.
Use of a quick connect, recommended, 100a T-Plug, or other.

No, it is not necessary to use all 6 balance pins.
On the iMax B6, connect neg pin to Neg pin, leave additional on Pos end empty.
10S as 2-5S or 8S as 2-4S works fine. (As tested on iMax B6 and B8.)

Cautions! Disconnect battery from controller, and separate battery, before attaching balance plugs.
Disconnect charger and balance wires before reconnecting battery! (6-22awg silicone wires will surge a nasty current!)

[DrkAngel]

Soon after I got my first EZip, I determined that the OEM 24v SLA batteries were woefully inadequate.
Even before I went to 36v SLA, I built and, briefly, used a home-built Nimh pack.
Somewhere I found a reasonable priced source for 7ah D cells.
After a bit of searching I also found a "lot" of 8 D cell holders.

Using 2 1/2 - 8packs I had my 1st 24v 7ah pack.
Probably, due to the limited wire capability, the pack seem inadequate.

Nimh7ah.JPG (53.8 KiB) Viewed 3103 times

So ... I decided to double the pack, in order to achieve double the amp output, as well as double the ah.

Nimh14ah.JPG (62.6 KiB) Viewed 3094 times

At the time, my ezip was limited to the oem 16mph, and that, combined with a mishap that detensioned all the springs on 1/2 the cells, prompted me to move on to my 36v SLA phase.

Yes! That is why I always recommend installing an inline fuse!

[DrkAngel]

Testing Recycled Li-ion Cells!

Testing cells is the most laborious part of building your HomeMade Li-ion, or Lipo, battery pack!
It is important to test thoroughly.
A few extra hours testing, before assembly might give you years of trouble free use.

Start with an excess quantity of identical packs!
Ideally you should begin with with enough cells to create 3 packs.
I would recommend 2600mah cells.
2600mah cells were produced after the contaminated cell recalls, of previous years.
(Metal particulate contamination produced possible internal shorting, during certain productions.)
Smaller capacity cells will be older, but price and availability, might make them a better option.
(If worried about recalls of an older battery pack, investigate notebook battery recall, by manufacturer and model. Before purchasing batteries.)
Most laptop packs have cells paired, or connected, leave them connected, it makes final assembly much easier.

Step 1
Charge a batch of cells to an identical voltage, I recommend 4.2v, make sure your volt meter measures 1/100ths.
Preliminary charging, then ganging cells together into parallel banks, for final top-off charge, is recommended.
After attaining full charge, separate all cells.
The typical charger will charge to slightly higher than 4.2v, this surface charge will equalize to actual voltage after a couple minutes.

Step 2
Allow cells to set a full 24 hours, then compare the voltage of all cells.
The percentage of voltage drop, is a good indicator of battery condition and capacity.
Mark all cells, -1 if drop is .01v, -2 if .02v etc.
Separate cells into categories, then recheck after another 24 hours.
The more days you test, the better determination of quality!

Step 3
Occasionally one cell of a pair will be bad, holding a surface charge.
So it is important to test for this.
This is done by either applying a timed power drain, then comparing voltage drop, or by monitoring the voltage sag while applying a power drain.
A larger comparative voltage drop will indicate a bad cell.

Most important is that you find cells of comparable condition.
Ideally you should begin with with enough cells to create 3 packs.
Use your best cells for one pack, the next best for your reserve or second pack the remainder might either be bad or of lesser quality.
Quantity of "good" cells will vary by brand, ah capacity, etc.

The better matched the cells in a pack are, the more even will be a charge, from a non-balancing charger.
My last pack assembly has been re-charged a dozen plus cycles and is still equalized within a couple 1/100ths of a volt.
Monitor cell voltages before, during and after recharging, especially during your 1st uses.
If anything seem "out of balance" monitor charging carefully, until problem is determined.
I do recommend the occasional balance charge, so install a balance connector, or manually equalize cell voltages occasionally.

[DrkAngel]

I got my 5 - 1-8S Lipo Battery Tester Low Voltage Buzzer Alarm.

Looks like when people started ordering quantities, they re-checked the monetary exchange rate, then tacked on another $1.19 per item.
Glad I ordered mine fast.

1-8S Lipo Battery Tester Low Voltage Buzzer Alarm RC 1S - $4.48

[999zip999]

bump.

[DrkAngel]

I must say, The latest batch of - 1-8S Lipo Battery Tester Low Voltage Buzzer Alarm, has greatly improved voltage accuracy.
My last purchase, of 5 items, when tested, showed only a slight variance from tested actual. They might even have met their claimed "within .01v".
Even at their new, higher, price, a fabulous bargain!

I will use the older, less accurate, ones as voltage meters.
Simply wiring one into the throttle, voltage level, leds, should give a very accurate fuel gauge!
Since the low voltage alarm won't work, in that application, complete water-proofing should present no problems.

[DrkAngel]

Got bored!

[bobale]

Will those 18650 batters be able to provide enough current to drive such powerful tools?

[skeetab5780]

lol look out for that raw black and decker power! rawr

[DrkAngel]

Will those 18650 batters be able to provide enough current to drive such powerful tools?

Li-ion is 14.8v 5.2ah and, as I tested, capable of 10 amps continuous 20 amps surge.
NOTE: Exceeds what I consider "acceptable", or prolonged usable, discharge rates!
But demonstrates brief, or emergency, capability.
OEM pack is 14.4v 1.4ah, if expended in 10 minutes continuous use, (6C), then battery draw would be 8.4 amps.
Which is less than, the tested, continuous output on the Li-ion, and about 40% of the surge capability.

Ultimately, it is a mater of how well it works, during typical use.
Testing ... so far:
Circular sawed a few 2x4's
Recipricated down a couple dozen small trees - branches
Screwed - unscrewed a dozen 1 5/8 drywall screws into a 2x4

Performed as-well, or better, than a good nicd pack!

Of course ... I haven't tried 2 1/2" decking screws, into pressure treated yellow pine ... yet.
But I always predrill that sort of stuff.

[bobale]

Li-ion is 14.8v 5.2ah and, as I tested, capable of 10 amps continuous 20 amps surge.

So those are some higher quality 18650 cells?