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18650 Projects
I have a few projects in mind. First was a LiFEPO4 12v battery, but I don't want to outlay for new cells at this stage, I'll put that on hold.

I've recently secured a (hopefully) steady supply of cordless tool batteries with my first box count around 350 cells. Whilst these are harder and more time consuming to liberate from the housings, I think it will actually be worth it, as the most common cells seem to be 30Q followed by 25R, with some Sony V and VCT6. Also scored some 21700 40T. Not sure what to do with these as yet!

If the flow of 30Q keeps coming, that will mean a decent wall with less cells and work. I might use the 25Rs for other projects, or backup for a Powerwall.

My next project, using the 25Rs, will be a 36v Longtime 1K UPS. I've placed my first order for holders and a BMS. The UPS houses 3x12v LA. The plan is, to relocate the circuit board above the batteries, remove the Intelligent slot, and fit 10S9P in 3 banks to fit in the space. I might place a connector on the back to expand the capacity.

About 10 years ago, I was given a very large UPS that did not work. I suspect it was just the batteries were dead, and there were a lot. As I had not found a use, nor even attempted to test and fix, I dismantled and disguarded it a couple of years ago. I wish I had kept it as it would have been a ready made powerwall system - Just add 18650s!

For this small UPS, I'll probably just spot weld nickel strip that I've had for years. For larger projects I'm going to research and decide on the assembly method. Spot welding would be my preference, but using standard strip would offer no fuse cell protection. Soldering creates much heat, hazardous gas and I think more time. Perhaps I'll look at the fused nickel strip I saw Pete testing a while back. Happy to consider other methods.

I'm thinking along the same lines as Pete and putting up a slimline shed at the back of the house to keep the danger outside, and ventilated. I just wish I had my 90m2 shed to cover in panels.

Testing method: I've currently got a Nitecore D4 and a LiitoKala 500. Planning on getting an Opus C3100, a Lii-500s and perhaps another 500 and maybe a PD4 or 402, for its 0 volt refresh, and a Nitecore i8 for bulk charging. Open to thoughts, or links to better options. The Lii-500 is doing an OK job, but I want to see if there is more efficient units out there.
I've spend a little over a week shucking cells. Probably close to 400 cells. Whenever I get bored, I go into my office and do another 1 or 2. I've got a couple of Hilti and an EGO left to go. Here's a pic of the results so far. Sorted into manufacturer capacities. Charged upper left, and tested good upper right. Slow progress with only 2 units.

I've actually had good success bringing 0v cells back to life. I first started by parallel'ing a good with a bad for 20 seconds, then on the D4. Yesterday I rigged up a cheap eBay USB powerbank housing to a single cell holder. The readout is wildly inaccurate. It reads 100% when the voltage is anywhere near 4v initially, and goes blank if the cell is depleted, even when powered with USB. I'm using a USB power meter to see what's going on. When I insert a 0v cell, the current increases over a period from 100~200mA, to about 1.5A, then once its returned to a few hundred mA I chuck it in the D4 and put another 0v cell in.

The majority of donors have been Milwaukee 5, 6 and 9AH. Some Makitas, Dewalt, EGO, and a couple of others.

I'm looking ahead to how best utilise the cells. Yes, a Powerwall, but how.

I have a grid tied 5kW PV system that nets me roughly $500/qtr as I get the Govt solar rebate. I believe that if I add a battery system to it, they will reduce my FIT to the current rate (8c?)

So, my plan is to install panels on the shed roof (albeit fairly small ~12m2), run DC cables underground, through a small shed behind the house, (shed to house the batteries, and management), then mount an inverter in the garage beside the existing system. As I build the system, I'd like to move loads, or circuits over 1 by 1. I expect because it is not connected to the grid, that it should not effect my FIT. End game is to feed 100% of house solar to the grid and use second system for household usage with the added benefit of having power during outages. I'll have to look at grid backup and battery charging capability for extended outages or battery maintenance. Not sure how for all of this yet!

I'm looking at second hand panels, or I might consider upgrading the oldest 1 of 2 strings of my house panels to the latest and use those for the shed. The 2 strings are maxed for voltage but current can be increased infinitely I think, because the Inverter just clips it, and I haven't actually reached its capacity anyhow, due mostly to panel setup.

I'm planning on removing the panels, cleaning and painting the roof, and refitting panels, and I'll look at adjusting the angle a bit.
Any thoughts on the above?

I'm well under way in testing and sourcing parts for my UPS build. My next project will be a camping pack. I searched "camping" with "18650" and also "4s" with "mppt", and returned zilch. Not sure what else to search for that.

Using a 4S pack, getting down to 12v is easy. Its the charging from a solar panel that I'm not sure about. I have a functioning solar control box for a 12v AGM that I have been using for years. I built it in a portable tool box with standard parts...
Low voltage cutoff
8 way fuse block
Internal 7AH SLA for short term power
2 x Volt,Amp,Watt meters (for in and out)
MC4 connectors for solar panel
2 x 50A Anderson for main Battery and vehicle battery connection
Attached LED light and switch to use box as setup light
USB, Cig and Engel sockets for output

One thing that always bugged me about the meters, and all similar that I have found, is they are all negative shunt, meaning I can't have a common earth for the whole system.

To use 4S Li-ion - As far as I can figure, all I really need is a DC-DC stepdown to drop the max 16.8v to 12v (or maybe 13.8v) - I can always increase the LVCO to a higher voltage), and a MPPT designed for 4S Li-ion. Wat am I looking for?

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