Homemade Battery Packs

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.


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


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!

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.

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

bump.

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.

Got bored!

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

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

bobale said:

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

Click to expand...

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.

DrkAngel said:

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

Click to expand...

So those are some higher quality 18650 cells?

bobale said:

DrkAngel said:

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

Click to expand...

So those are some higher quality 18650 cells?

Click to expand...

Used, 2600mah cells, pulled from Gateway laptop battery.
Hooked 11.1v 5200ah of them to a 12v Toro 250 leaf blower.
Initial, starting draw was 20+amps, quickly settled to 11amps and after 5 minutes run time, was still drawing 9+ amps.
NOTE: Exceeds what I consider "acceptable", or prolonged usage, discharge rates!
But demonstrates brief, or emergency, capability.
After 5 minute 2C drain, cells were warmish.
Prolonged 2C drain liable to damage cells, or present possible hazard.

I would not use these laptop cells at 1.5C for more than 60 seconds. 30 seconds max for 2.0C. No matter what the specs, these cells are designed to be used in a 0.5C environment (2hrs or more on a laptop).

Any advertisement you see on this site can infect your computer. DO NOT CLICK ON ANY ADS
http://endless-sphere.com/forums/viewtopic.php?f=1&t=30462&p=440222#p440222

DrkAngel said:

...cells were comfortably warm, held against face for several seconds, not uncomfortable.

Click to expand...

I recommend an inexpensive IR thermometer.

SamTexas said:

I would not use these laptop cells at 1.5C for more than 60 seconds. 30 seconds max for 2.0C. No matter what the specs, these cells are designed to be used in a 0.5C environment (2hrs or more on a laptop).

Click to expand...

7 seconds to cut 2x4
3 seconds per screw
etc. ... ?

SamTexas said:

these cells are designed to be used in a 0.5C environment ...

Click to expand...

If we only "used", as things were designed to be used, there would be no innovation-enhancement-advancement.
Don't try to take that away from us ...

skeetab5780 said:

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

Click to expand...

FireStorm!

DrkAngel said:

SamTexas said:

these cells are designed to be used in a 0.5C environment ...

Click to expand...

If we only "used", as things were designed to be used, there would be no innovation-enhancement-advancement.
Don't try to take that away from us ...

Click to expand...

Not trying to take anything away. I'm a user of laptop 18650 cells in my ebikes. I too have real life experience with these cells. I have tested them at 1C and 2C and I don't like the heat that comes with those rate. I don't see running hot cells as an innovation-enhancement-advancement.

SamTexas said:

DrkAngel said:

SamTexas said:

these cells are designed to be used in a 0.5C environment ...

Click to expand...

If we only "used", as things were designed to be used, there would be no innovation-enhancement-advancement.
Don't try to take that away from us ...

Click to expand...

Not trying to take anything away. I too have real life experience with these cells. I have tested them at 1C and 2C and I don't like the heat that comes with those rate. I don't see running hot cells as an innovation-enhancement-advancement.

Click to expand...

I'm talking about replacing worn out,1.4ah nicd, w/5.2ah Li-ion, resulting in power for tools, with 3 1/2 times the run time, 10 times the recharge cycles, etc.
At a cost of about $2 for the battery cells!

Better than paying $50-60 for the wimpy replacement pack!

DrkAngel said:

At a cost of about $2 for the battery cells!

Click to expand...

If nothing else, you can't beat those used laptop-pack cells on price . Anyway, where did you get that 4S balancer, and how much did it cost?

DrkAngel said:

I'm talking about replacing worn out,1.4ah nicd, w/5.2ah Li-ion, resulting in power for tools, with 3 1/2 times the run time, 10 times the recharge cycles, etc.
At a cost of about $2 for the battery cells!

Click to expand...

May be so. But you're also telling people that using it at 2C to 4C is OK!!!

DrkAngel said:

Used, 2600mah cells, pulled from Gateway laptop battery.
Hooked 11.1v 5200ah of them to a 12v Toro 250 leaf blower.
Initial, starting draw was 20+amps, quickly settled to 11amps and after 5 minutes run time, was still drawing 9+ amps. After 5 minute 2C drain, cells were comfortably warm, held against face for several seconds, not uncomfortable.

Click to expand...

bobale said:

DrkAngel said:

At a cost of about $2 for the battery cells!

Click to expand...

If nothing else, you can't beat those used laptop-pack cells on price . Anyway, where did you get that 4S balancer, and how much did it cost?

Click to expand...

4S 14.8V LED Intelligence LiPo Battery Charger 1500mah - $10.98
Probably wont use this with my FireStorm battery pack, will probably T-Plug an iMax B6 into one of my defective 14.4 charger bodies and charge at 2.5 - 5 amps, 5 amps, if I'm in a hurry.
Tho I did install a balance connector, I haven't yet cut a hole, for external access.

I have about half a dozen of these packs, after testing is complete, I'll probably convert another few.
Might need to build a treehouse, up in the woods? ...or?

SamTexas said:

I would not use these laptop cells at 1.5C for more than 60 seconds. 30 seconds max for 2.0C. No matter what the specs, these cells are designed to be used in a 0.5C environment (2hrs or more on a laptop).

Click to expand...

I use these cells on my ebike, also.
I recommend 20-30ah worth, which gives me about 1C surge and .33-.5C continuous, which is what I recommend as reasonable for these type cells.

On the other hand, with the brief outputs of B&D power tools, 2C, (10amps+), in few seconds bursts, seems very acceptable.
These tools do not have an "amp" usage on the label, but I doubt it to be 10amps.
I ran the Reciprocating saw, almost continuously, for an hour, and had plenty of power left, less than 5 amps during actual use?

Promoting the use of recycled 18650 laptop cells is a commendable task, especially on this forum where the majority looks down on laptop cells. So you did a very good job so far. But when you told people that these cells could be run at 2C and 4C like you did a few posts up in the Toro leaf blower example, you went too far.

As I have said earlier, 2C is fine for a very short time, 30 sec max. 4C is fine too for 5 sec max. The biggest advantage of laptop 18650 LiCoO2 cell is its very high energy density. And because of that very same high density the c-rate (power density) is compromised. You're absolute correct in your ebike application, 1C surge and up to 0.5C continuous.

If I were you, I would remove or edit the Toro leaf blower application note and send me a PM so I can remove my comments surrounding it too.

DrkAngel said:

Used, 2600mah cells, pulled from Gateway laptop battery.
Hooked 11.1v 5200ah of them to a 12v Toro 250 leaf blower.
Initial, starting draw was 20+amps, quickly settled to 11amps and after 5 minutes run time, was still drawing 9+ amps.
NOTE: Exceeds what I consider "acceptable", or usable, discharge rates!
But demonstrates brief, or emergency, capability.
After 5 minute 2C drain, cells were warmish.
Prolonged 2C drain liable to damage cells, or present possible hazard.

Click to expand...

DrkAngel said:

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 usable, discharge rates!

Click to expand...

There you go. I like the edited (in red) version much better.

For people new to (or unfamiliar with) laptop 18650 LiCoO2 cells, make sure your battery pack does not exceed 2C draw for more than 30 seconds. For example if you built a 500wh pack for your ebike, it's ok to see 1,000W draw when you're accelerating, but it's not ok to see 1,000W when you're cruising. For 1,000W cruising you need to build a 2,000wh pack.

14.8v Li-ion power pack rebuild seems to be working excellently!

Next, I'm gonna dig up my old Craftmen 12v power drill, and rebuild it's 2, bad battery packs!
11.1v Li-ion should work nicely with 12v (1.4ah = empty at 10v), 11.1v charges to 12.6v (5.2ah = empty at 10.5v).
Note: Li-ion - pay attention to voltage, deep discharge can severely reduce lifespan-usability.

Good possibility that other voltages should work nicely also:

Nicd ................ Li-ion
12v ................. 11.1v
14.4v .............. 14.8v
18v ................ 18.5v
24v ................ 22.2v or 25.9v

If we only "used", as things were designed to be used, there would be no innovation-enhancement ... advancement.

Well I think I have enough cells now....

The first lot- after charging and sorting, enough for 48V 40Ah




Picked up my second lot today- should be about 48V 80Ah's worth there!


I don't want to stress these little suckers much so will put on as much Ah as my bike will fit!