station240's 18650 projects

S

station240

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Joined
Oct 9, 2016
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177
Small pack I'm working on.
For now to be 12V nominal SLA battery replacement, for my under desk UPS.
These are A123 LiFePO4 (lithium iron phosphate) cells, recovered from faulty drill battery.

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Long term projects/plans.
These mostly involve Project UPS aka Project Fridge
This should give you some idea of how large and heavy this UPS is.
a) 12/48V battery for DC Contactors, cell/voltage monitors, other electronics.
b) Powerwall for big UPS, which didn't come with any batteries. Did however come with a complete set of unused high current battery cables.
c) Project MPPT, inject power into the UPS from solar panels. Re purposing a mostly functional Grid Tie Inverter, which isn't able to be used for it's original purpose.
Could be repaired fully, but I'm not interested in spending the $40 needed to repair the inverter output.

Completed sub projects:
a) Teach the fridge to not require 3 phase power, my tricking the low voltage electronics. Suspect it may not power up with only battery power.
b) Disable the inbuilt charger for Lead Acid batteries. Turned out to be as simple as unplugging the connector to that half of the PCB.
 
If anyone in Australia has any of these A123 cells they would like to donate, let me know.
They are 3.2V cells rather than the usual 3.7V.
My internet is too shit to have a youtube channel, so everything has to be photos or text.
 
I think I've ditched quite a few of these.. I'll keep an eye out for more for you .. they are no use to me :)
 
Found the TP4056 doesn't do LiFePO4 cells, so looking at either an alternative module off ebay or further modify a PSU to be a dedicated charger.
 
station240 said:
Found the TP4056 doesn't do LiFePO4 cells, so looking at either an alternative module off ebay or further modify a PSU to be a dedicated charger.
Click to expand...

I use a computer psu with a 'step up converter' so it can be done.
Why not switch to 18650 before the project gets to big?

Good luck with the project and keep us up to date

Cheers
 
Still pondering what charger to use for individual cells, there are boards that use the MAX1879 IC, which also come with a polarity switching system so it doesn't matter what direction the cell goes in.
The reason for the MAX1879, is it has multiple charge voltages (select using wire jumpers), of 4.35V 4.2V 3.6V. The 3.6V is needed for LiFePO4.
Basic idea is to use those boards for charging untested cells, and build a higher current charger that can do multiple cells.

The A123 cells I have are good for 30A discharge, I'm going to have to devise a way of testing that.
 
Been working on various things, so far this is the only 100% finish part.
This transformer like part is an inductor from some Industrial equipment, which I kept for some reason.

Was difficult but I managed to dismantle it, without damaging the copper in the process (stretching or scratching).

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dimensions: 1.2mm thick 28mm x 77cm

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I really should have tried not to bend these connections.

My DIY battery charger, built almost entire from ATX PSU parts, mostly works.
However it's not stable at 3.6V needed to charge LiFePO4 cells, is perfect on 4.2V so can charge normal Li-Ion cells.
Todo is to add circuitry to add a max and min current cutout.
eg max current 1A min, min current 75mA.
The min current being how you are supposed to determine if an 18650 is fully charged.

The charge process for LiFePO4 cells is rather different, still trying to wrap my head around that.
 
If you are intending to use these packs within an existing UPS, how are you intending to alter the UPSs' charge process to suit the new chemistry ?
 
Sealed Lead battery: 6x 2V cells 12V battery 14.4V charge
LiFePO4 battery: 4x 3.2V cells 12.8V battery 14.4V charge

So the issue is not charging the new battery, but having the correct low voltage cutout.
This of course is the small UPS, which has a weird charging circuit.

The big UPS is no issue at all, I disabled the internal charger months ago, simply by pulling a plug out of the PCB.
 
Concept for battery charger for LiFePO4 pack.

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For a single cell just connect a 5V switchmode PSU (eg ATX computer powersupply) to the input of TP5000.

However I want to charge the 4S 12V pack without needing a BMS, so I came up with this.

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T2 is simply a transformer constructed with an equal number of turns for each of the 5 input/outputs.
The original output components are either re-located or tossed into the junk box.
I've got some pre-dismantled transformers that will suit.

In reality the PSU output has extra parts, filter inductors, feedback components etc.
The feedback circuit just needs to be tied onto one of the new outputs.


Why I chose the TP5000
a) Has the ability to modify charge current and voltage. 4.2V or 3.6V, 100mA to 2A
b) Found some cheap here http://www.ebay.com.au/itm//351913464091 I ordered 5 so asked for and got a small discount on top of that.
c) Uses an inductor so it's a buck based circuit, hopefully more efficient and less heat.
d) Has a full size LED, and pads to solder it into. Hence can be made neater and easier to see the status.

Plenty of time to construct the extra circuitry needed, which I plan to bolt to the output of an ATX PSU.
 
Did a high current discharge test on a 18650 A123 cell the other night.
Cells are rated for 30A continuous discharge current, so that what I did.

Used 82cm length of 0.36mm copper wire, a calculator I wrote was used to work out if it was suitable.
Cell got barely warm, the wire got very hot.

Safety followed for this test:
1) Conducted outside on concrete path.
2) Bowl of water next to cell.
3) Wire soldered to positive end of cell, left unconnected to other end.
4) Other end of wire gripped by pliers and touched against negative of cell.

All in all successful test, cell did not overheat, nor did the wire unsolder itself. Both things I was worried about.
Will repeat with a second test, one I have the charger to fully charge the cell, and because I forgot to attach the multimeter's temp probe.
Should also measure the voltage under full load, see how it compares to the datasheet.
 
Hi
Are you still looking for these cells?
I think I have at least 4, although some of the text on the cells is slightly different. They were out of a dewalt power tool battery.
They are dame colour as your photo and have following text.

They have LR1865AM APR18650M1A
R

They were all harvested at 3.29 volts.
Let me know if they are useful to you.
Cheers
Phil
 
Yes still after more cells, need a few hundred more.
LR is Lishen, somehow involved in the new owner of A123.
 
Gotten a few things over the past few months, been too busy to document it all properly.

Got given a very rusty ammo box with random tools in it, no prizes for guessing what that is used for.
Big box of random cables, three big AC contractors to re-purpose, and some new electronics I ordered.

got six 36V Dewalt packs off ebay, didn't expect to get 1x A123 pack, 2x Samsung pack, 3x Sanyo pack
So end up with:
9x A123 26650m1-N LiFePO4 3.3V 2.5Ah (one had leaked and is dead)
39x Samsung IFR18650-11Q LiFePO4 3.3V 1.1Ah (one has clearly overheated and is dead)
30x Sanyo UR18650RX 3.7V 1.95Ah in varying poor states of charge (some already binned)

The one A123 pack is good, bar the mess the leaking cell made. I will rewrap the cells later.
The Samsung packs are wired in 10s2p, so the current is shared over two cells.

The Sanyo cells have issues, for a start they were wired in 10s1p with 10 dummy cells. Probably had a hard life. They are also 3.7V Lithium cells, so not much use to me at the moment.

So far I have recharged all the LiFePO4 cells, and didn't that take ages. Not capacity or resistance tested them yet. The TP5000s arrived obviously.
 
Going to shift all this onto twitter, the almost complete lack of interest here is depressing.











< twitter link there
 
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