Homemade Battery Packs

[DrkAngel]

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Index Updated

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. . . . . . . . . . . . . . . SONY LiPo Mapped!

Building my next battery packs using Sony LiPo.

I decided to precisely map charged capacity at specific voltages ...

These cells look excellent for prolonged usable life by reducing charged voltage!

These Sony cell lack the capacity bulge near 4.10V and will respond much more advantageously to charged voltage limitation! (I have in large quantity)
Differing cell formulations map very differently!

While I have never recommended charging specifically to 4.00V ...
(4.00V charge ~75% usable capacity x 400% usable lifespan)

$100 10Ah battery 3.70V - 4.20V (10 mile range x 500 cycles = 5000 mile lifespan)
$135 13.5Ah battery 3.70V - 4.00V (10 mile range x 2000 cycles = 20,000 mile lifespan)
(Looks to be an excellent bargain!)

I have often recommended charging specifically to 4.10V ...
(4.10V charge ~90% usable capacity x 200% usable lifespan)

$100 10Ah battery 3.70V - 4.20V (10 mile range x 500 cycles = 5000 mile lifespan)
$111 11.1Ah battery 3.70V - 4.10V (10 mile range x 1000 cycles = 10,000 mile lifespan)

Charging oven lower 3.95-3.90V looks very usable ... !

These cell look optimal for extreme long life for my mobility scooter (eTrike) builds. (NEV might be better, more descriptive)
At designed 10mph, 4.00V 500Wh battery should give 2000 ~25mile cycles = 50,000 miles
(These SONY cells have deteriorated minimally in their 6-10 year ageing, unused samples exhibit 90%+ of rated capacity! )

I did the numbers on solar panel output, compared LiPo to SLA charging and discharging efficiency, rated usable cycle lives.
Showed LiPo needing about 60% the number of solar panels for the same provided electric return. - (through battery)
Showed 90% charged LiPo as cheaper than SLA in as little as 3 years. (cycled daily)

Received requests for all the 3s 1kWh packs I can build, SONY preferred!
3s50p 2.16Ah cell = ~1200mAh
Sorting through the ~1000 cells I charged last Fall, will only use those with negligible self-discharge and 6 packs of equally retained voltage.

Less than perfect cells to be used in inverter packs, or similar.
Perfect cells, gotta save the best ... reserved for my eBike builds.

Index Updated

 

[Skalabala]

Hey bud. I can get hold of 7000mah tablet lipo. About 900wh worth(on paper)
What do you think? Low C rate?

 

[DrkAngel]

Laptop (and tablet) LiPo and Li-ion are specifically designed for high capacity, which sacrifices C rate.

My rule of thumb is to build "laptop packs" for ≤1C max discharge.
≥30Ah (actual capacity) battery pack for a 30A controller.
Not only does this limit voltage sag, but greatly extends battery life!

I converted most of my eBikes to a multi-compatible 22.2V - 44.4V 28A controller - (50V caps ... 12s x 4.12V = 49.44V. Will replace w/63V caps if 50V caps ever fail).
31.2 oem rated packs usually have near 28Ah actual capacity when built (recycled cells)
26Ah LiPo builds push my self-imposed limit somewhat and I do transfer from 21mph geared to 17mph geared eBikes when actual capacity drops near 20Ah.

 

[DrkAngel]

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. . . . . . . . . . . LiPo vs SLA

30A controller with 10Ah batteries = 3.0C

At 0.5C discharge: 10Ah LiPo (6lb) = ~20Ah SLA (50lb)
At 1.0C discharge: 10Ah LiPo (6lb) = ~30Ah SLA (75lb)
At 2.0C discharge: 10Ah LiPo (6lb) = ~40Ah SLA (100lb)
At 3.0C discharge: 10Ah LiPo (6lb) = ~50Ah SLA (125lb)
At 5.0C discharge: 10Ah LiPo (6lb) = ~70Ah SLA (175lb)

*200% additional SLA size to meet recommended 50% discharge = reasonable battery life!

 

[ASK1]

Hi guys,

I've assembled my parallel groups of 18650s and am about to connect them in series (with redundant series connections). Do you think any kind of padding material between cells is needed, or is it okay to have them in a tight staggered configuration? I intend to go easy on these cells as far as how hard I push them. Thanks.

Edit: Also wondering if there is any advantage to wrapping each parallel group in tape, maybe to add a little more strength so they aren't just relying on the solder joint-to-tinned braid connections to hold together and minimize the stress on those connections. However I feel like that would insulate the cells more and cause them to run hotter?

 

[DrkAngel]

I tightly wrap the outside, to prevent any wiggle.
Never had any wear problems in many packs over many years.
However, if concerned, 3" duct tape between different parallels should provide an extra degree of safety ... or assurance.

If run at ≤1C continuous there is negligible heat production ...

 

[ASK1]

Cool. Went ahead and did that.

I'm going to go ahead and make all the series connections next.

Do I need to be careful about how I connect my BMS? I'm going to do that after everything is connected in series.

 

[DrkAngel]

Cool. Went ahead and did that.

I'm going to go ahead and make all the series connections next.

Do I need to be careful about how I connect my BMS? I'm going to do that after everything is connected in series.

Use proper care during assembly. ... ?
Fuse recommended also.

 

[ASK1]

Sorry that was a pretty vague/dumb question of mine. I checked the wiring diagram for the BMS, and I now understand how it is wired, but I think I have a problem - my 13S BMS has only 13 balance wires whereas its wiring drawing indicates 14. And any BMS should have N+1 balance wires (where N is the number of cell groups) - right?

Wiring diagram: https://imgur.com/8UG8Z64
^ (My BMS is missing one wire from the first group, there are 10 on mine instead of the 11 pictured)

The pack is assembled (absent BMS). I seriously need to improve my soldering technique/process. I caused 3 (!) shorts between adjacent parallel cell groups when the iron slipped from the tinned braid I was pressing down on and into the space between the cells. What are the likely consequences of this to be? Is there some risk that damage to the outer polymer coating (which did happen to a small extent) could lead to another short between these cell groups? I can live with some capacity loss, but I want to ensure my pack is not a risk. The cells are NCR18650A, FWIW.

Edit: I also was wondering, if there were some issue in some cell(s) one of my parallel groups (for whatever reason, bad soldering, the shorts I caused), how could I detect this? If I leave the pack and monitor the voltage of each parallel group, if the idle voltage loss over time is slow then I am probably okay (minus the potential risk of additional future shorting incidents), right?

I am fusing the positive end of the battery about 2" down.

 

[ASK1]

I've been monitoring the pack voltage and it has stayed constant since I built it... I'm probably going to proceed with wiring it up to my bike tonight.

Edit: Successful first ebike build (for now) and ride!

Now I need to figure out how to wire the charger tomorrow (maybe after I figure out how to remove the speed cap on my BBS02) :lol:

 

[rurbano]

Hi all, sorry if this not the right place to post this.

I'm looking for a easy-realiable-simple no welding built to power a 2000W motor (3kw cyclone).
Found some good ideas her on ES but was wondering if anyone tried one of these:

http://www.keyelco.com/category.cfm/Cylindrical-Cell-Clips-THM-and-SMT/For-17-19mm-Dia-Lithium-Ion-Batteries/p/404/id/943/c_id/1207

The basic idea is to have one of these at each end of a 18650 cell then srew it/solder it to a cooper busbar.

Would it work?

Thanks in advance.

 

[DrkAngel]

#1
I would like to Lithiumize my Homelite 20" mowers 24V 20Ah battery.
I have large quantities of 3s2p Lipo!
Tested with a 6s 22.2V RC LiPo pack but motor speed and torque in the high grass was unsatisfactory.

#2
Recently purchased my 2nd electric lawnmower.

• $35 for for a $600 Neutron CE6 with all the extras ....
• Mulcher plug
• Bagger
• Spare blade
• and a corner mount trimmer-edger

Bad 36V 10Ah battery, but fortunately I saved 10Ah SLAbatts from upgraded eZip packs.

I really dislike the weight and inefficiency of Lead Batteries ...
But I balk at the thought of dedicated LiPo builds, with my good cells, for lawnmowers

Fortune shines ... In the form of the test results of my recently tested SONY LiPo.
Instead of the capacity bulge present near 4.15V as in my present eBike batteries, the SONY cells have a nice hefty bulge near 3.80V that diminishes nicely towards 4.20V

This means reducing charged voltage, to prolong usable life, loses a comparatively minor amount of capacity!

#3
So 2 new 25.9V 25.92Ah eBike battery builds using SONY cells.
and
recycled 25.9V 25.92Ah (~20Ah actual capacity) battery to replace 24V 20Ah SLA in Homelite 20" mower.
and
25.9V 25.92Ah + 11.1V 25.92Ah addition cells (~20Ah actual capacity) = 37V 25.92 battery to replace 36V 10Ah SLA in Neutron 20" mower.

Win-win-win!

2 new eBike batteries with greatly prolonged life at minimal capacity loss
and
2 decent runtime mowers with minimal maintenance requirements and extreme battery life
200 annual cycles reduced to maybe 30 ... with a long off season storage at cool temp and partial charge, should last many, many years!

 

[DrkAngel]

Direct comparison of the cells in my old eBike batteries and my new.

• SONY chemistry supports decreasing charged voltage to increase usable life much more efficiently:
• (new) 10% capacity loss for 200% life cycles vs (old) 20% capacity loss for 200% life cycles
• (new) 17% capacity loss for 300% life cycles vs (old) 30% capacity loss for 300% life cycles (life cycle percentage not exact but comparison valid)
• (new) 26% capacity loss for 400% life cycles vs (old) 37% capacity loss for 400% life cycles

- (note 4.18v as 100% on "old" non-SONY graph)

 

[ridethelightning]

im loving this stuff about the lawnmowers.
any plans to turn one into a hovercraft?

btw, how do the samsung Q and R range compare with the sonys, regarding reduced charge voltage vs prolonged lifespan?just wondering if youv tested any.

cheers.

 

[DrkAngel]

Samsung INR18650-25R
Shows a substantial capacity bulge near 4.10V.
I recommend charging to ~4.12V as optimal.

Let me check if graphed data is still in my database ... if so, I will post up percentage lines very soon.

OK ...

Being derived from discharge data, though minimal, accurate data would be represented by shifting graph lines slightly higher.

Shift graph line (Pink) to the right slightly or
Shift percentage lines slightly left ... possibly .02V?

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[Hummina Shadeeba]

Where'd u get Sony lipos. Never seen them and they sound good

 

[DrkAngel]

Recycled from Dell Media Bay auxiliary batteries. Swaps with removable cd-rom.
3s2p, cells with individual fuses.

I lucked into multiple "Lot" purchases, haven't seen any good deals lately ...

Fuses removed for use in cordless power tools, I've rebuilt 18V and 19.2V 1.4Ah ni-cd as 18.5V 4.32Ah LiPo and 14.4V 1.2-1.4V as 14.8V 4.32Ah LiPo
But recommended for low drain devices.
Building high capacity 5s(18.5V)-6s(22.2V) switchable hip pack, (possibly 4s also, or separate, for 14.4V circular & reciprocating saws) , corded into empty battery casings.
6s6p 22.2V 12.96Ah for 18V-19.2V-24V
Large Ah expected to offset lower voltage in 24V tools!

Note: Sony cells are in model with metal lids and small screws on top. All plastic are the other listed LiPo - small tri-wing screwdriver bit in VSR drill works nicely.

Index Updated - 6/16 - No longer able to update links in Signature = Format changes!

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[ridethelightning]

thanks for posting the 25R data. im having a little a ponder figuring out what im looking at...

 

[Lory]

Thanks for all the information. They was very helpfull to get my DIY Powerwall project work.

[youtube]bBzPAQejyTA[/youtube]

 

[Hummina Shadeeba]

Haha. I was expecting to see a massive vehicle but no it goes on shelving. What is the purpose of the power wall? Maybe put the shelf on a hotrod.
the connection is just awhisker on the one side that would fuse at 2.5 amps?

I was confused by the writing and the goals and the writing disappeared too fast. Fantastic visuals otherwise.

 

[Lory]

The purpose is to charge when the sun is shining and my solar panels generate more power than my house need, store it and use it at night. In Germany i have to pay 30 cent per kWh from grid. sure i also can sell the kwh for 12 cent to grid but it is cheeper to use the maximum by myself.

without a storage 2015 i was able to use 29% of the energy i produced. with this power bank i´ll be theoretical off grid for 8 month per year and use 70% of the self generated power to run my house (heating, warm water, all the electric devices, ...)

yes only the cell fuses are very thin wired. the minus side is wired with 1,5mm coper but still 0,8mm would be enough. i tested the 0,8mm up to 40 amp and it dose not blow or begin to glow.

in practice there would be a max load with 0,9a per cell. so 2,5a fuse are still strong enough.

 

[Hummina Shadeeba]

I really like the idea of a dead weight energy storage using a little motor and a large gear increase or reduction (?) you lift a giant weight, suspend it indefinitely, and then release it to then turn the motor as a generator later when the sun is down. It sounds like it could be really efficient. What's the formula to figure how much energy is stored in a 100 hundred pound weight lifted 10ft above the ground?

https://youtu.be/8DzEUxmiPMA

Figured the math out and batteries are much nicer. To charge my 50 volt 8ah battery using a 100lbs weight it would have to be raised to 9600ft. And that's with total efficiency.

 

[Wheazel]

https://en.wikipedia.org/wiki/Potential_energy

 

[DrkAngel]

7000 Mile Report - 2013 eZip Trailz LS

Passed 7000 miles about 100 miles ago.
Except for a brief sojourn with my 33.3V battery, 7000miles were accomplished alternating with my 2 - 25.9V 25.92Ah recycled Laptop LiPo.
I did test with the 13T motor sprocket with a 23mph cruising speed but decided was too stressful on my Laptop LiPo builds
Rough tally estimates 4500 and 4000 miles on the 2 packs.
Average of possibly 20mph+ - includes 33.3V and 13T sprocket tests, Typical cruising is 19mph+
Just did a metered recharge at .2C to 4.15V per cell with a 19.78Ah capacity on the 4500 mile pack - 1 bank dipped below 3.50V and needs repair.
(Am building 2 new packs with SONY laptop LiPo and will re-recycle present packs into electric lawnmower batteries)

Replaced OEM rear hub-wheel at 2000 miles and have had no problems with broken spokes since.
Built wheel with alloy L\R threaded hub, SS spokes and good rim.
Replaced 9T motor sprocket once, 16T ACS Southpaw freewheel once and motor chain twice.
XYD-16 motor has held up nicely but will disassemble, lube and inspect bearings and brushes.
If in reasonable condition, might retire to occasional use or sell on bike to occasional use customer?

Early Spring 2014 (2008 dated cells) 25.9V 25.92Ah Laptop LiPo build @ 500+ cycles - 4500+ miles

 

[Hummina Shadeeba]

The purpose is to charge when the sun is shining and my solar panels generate more power than my house need, store it and use it at night. In Germany i have to pay 30 cent per kWh from grid. sure i also can sell the kwh for 12 cent to grid but it is cheeper to use the maximum by myself.

without a storage 2015 i was able to use 29% of the energy i produced. with this power bank i´ll be theoretical off grid for 8 month per year and use 70% of the self generated power to run my house (heating, warm water, all the electric devices, ...)

yes only the cell fuses are very thin wired. the minus side is wired with 1,5mm coper but still 0,8mm would be enough. i tested the 0,8mm up to 40 amp and it dose not blow or begin to glow.

in practice there would be a max load with 0,9a per cell. so 2,5a fuse are still strong enough.

On a 2.5 amp fuse if .9 is what I typically pull through it...wouldn't it be inefficient to the point of getting warm? And when the wires become warm or hot they get even more inefficient.


Fuse will only "get warm" when rated amps is neared.
36% of rated and short path help limit heat waste.
dark Angel