Just in Time for Aldi Saturday’s battery sale.
I bought some sets off flexible LED labels for video work. Unlike most other video lights, these ones work with 24V DC instead of 12V.
They do come with power supply bricks but I was interested in finding a solution to run them on batteries.
The manufacturer does offer such solution but it consists of a bank of 4 L type (Sony or aftermarket) batteries connected in series to create a 28V power supply.
While it is a great solution, I only have one tiny light in my kit that runs on those batteries, so for me it would have meant to get the battery holders plus a whole heap of batteries and chargers that I have no other use for.
In the USA they sell a lipo pack for these lights but it is over 100Wh so as of today you can only take two of these packs on a plane.
Making my own batteries or using e-bike ones was also considered but the fact that they don’t really have a hard carcass also discouraged me as I know that video gear isn’t always babied when on a job.
I thought about what other solutions could be for this problem while fixing a fence with a friend. I was driving screws with my Makita impact driver when it hit me.
What if I was to repurpose the tool batteries?
I mean, they are rugged (check), lithium based (check), under 100Wh depending on the capacity (check), chargers tend to be quick and charge multiple batteries (check) and I can use them for my tools when not in a job, and even during a job.
It will somehow rationalise the type of batteries and chargers that I have to carry and keep at home.
So I started researching and I found out that I wasn’t the first person to think of alternative uses for tool batteries, I found some great projects realised by very talented people. The highlight would be the DeWalt e-bike that someone did in the USA with 6 batteries in a 3s2p configuration. Find the videos I’m YouTube. That bicycle is a thing of beauty.
I have two different tool sets a 12V and a 18V (or 20V depending on the marketing) so I started thinking about which to use. In principle I decided to go 12V. I could just put 2 of these in series and have the 24V. So I hooked two batteries this way and set some tests up.
The lights do run but I was having two issues here.
First, The intensity of the lights was diminishing proportionally to the voltage on the battery bank. So the lights were only at a real 100% brightness for minutes.
The second problem is that I came to the realisation that the tools have the smart electronics in the Milwaukee M12 range, so the batteries just kept draining until it was dangerously low for lithium batteries. So this was going to really be killing my batteries if left to run for long.
To overcome the first problem I bought some 150W DC-DC Boost Converter 10-32V to 12-35V 6A from core electronics
The lights use approx 2A so Stephen suggested this type of booster instead of the boost/buck pololu one I was looking at just to have some headroom.
I received the boosters and hooked one with the batteries in series and it worked exactly as it should. It kept the voltage a constant 24.2V through the whole battery cycle. So that was a solution for the first part of the problems. But the batteries kept draining too low.
I continued my research about ways to overcome this issue and found a company in the UK that sells done very clever low voltage disconnector devices. After some emails and some brainstorming they agreed to create a custom solution for me that would monitor the state of each battery or pair of batteries in series and disconnect the circuit if they went under a certain voltage threshold, that I can select, for more than 10 continuous seconds.
That was problem number two resolved.
I was then on my way to have everything sorted. Except that I now needed to figure the sockets for the batteries and a way to put the booster and the LVD device in a case. Not too much of a problem.
While waiting for the LDV devices to come from the UK I kept thinking about this and decided to try with the Makita 18V batteries.
I hooked the booster and yes they did but they also have the issues with overdischarging and with these batteries choosing between $120 and $140 each I really didn’t want to be risking battery damage.
Makita tools also have the smart part in the tool via a third shorter contact next to the positive pole. So that was that and the Milwaukee tool batteries were to be the chosen ones. Or were they?
Enter the Aldi XFINITY battery line.
I went to do grocery shopping at Aldi and noticed that they had a big pile of XFINITY rapid chargers reduced 50% to $10 each. I thought to myself that is cheap. Next to them were the XFINITY 20V 2.0Ah batteries also reduced to $20 and I thought that is cheap for lithium batteries.
I went home and kept thinking about the batteries and chargers. I googled the batteries and found some photos of them opened by people. I saw that the cells inside are Samsung 18650 20Q. So doing the maths 20V is 5 cells at $20 that is $4 a cell. That is very cheap for Samsung cells.
Then I started looking at the XFINITY tools photos. I noticed that they only seemed to have two poles postive and negative. So I thought that they must have the overdischarge controller in the battery. Could it be?
Back to Aldi I went and bought a charger and a battery. With Aldi’s 60 day money back guaranteed it was all good.
$30 later I came back home and hooked the battery to the booster after a charge. The light ran at 100% for 57 minutes and then it turned off. I gave it a bit of charge again and tried while monitoring the voltage. When the voltage hits 10V under load the battery cuts off and the voltage bounces back to 15V. So the battery has its own protection. Nice.
Then I started thinking about the socket for this batteries and found some 3d printable files on thingiverse. so I thought. 3D printing + cabling + time…
I realised then that the chargers were reduced to $10 and they are the perfect fit and have contacts and cables already 3d printing them would be more expensive. The chargers are very light and I can keep the PCB as spares for my practical chargers.
Also the 4.0Ah batteries are going on sale this Saturday 14/07/2018 for $40. That is 10 Samsung 18650 Q20 at $4 a cell. So even for harvesting cells is economical.
Now for the technical of sorts part
These chargers are really light and easy to work with. Once you have them opened you only need to disconnect the three pole cables from the charging poles and relocate the “T” pole to the outermost positive. The pole marked with a plus (+) in the charger is a charging positive, not the one to tap from. This one can be completely removed if you wish, or can be left in there as a dummy pole. Your choice.
Unscrew the charger PCB and save it as a spare or cannibalise it for components.
The 150W DC-DC Boost Converter 10-32V to 12-35V 6A from core electronics fits perfectly inside the charger housing, not only that but the screw holes in both the booster and the housing actually line up so you can even reuse the screws and don’t need to modify anything in there. Make sure your connections are correct and close the housing. For my project I screwed two boxes together but only one contains a booster, the other one only has the battery poles connected to the first box in parallel. So positive to positive and negative to negative. I did this to increase my running times if I need to. I can actually run the lights using only one battery or two.
Also here is an image of the LVD (low voltage disconnector) that I got to use with the 12V batteries.
Now. Most of you would at this stage think that by using the Aldi XFINITY batteries I defeated the purpose of using a battery that I have other uses for. In principle it may look that way but once again at $40 a piece for a 20V (18V) compared to $120 for the Makita ones of the same capacity is a considerable saving and now I will just 3d print some adaptors to run these batteries on my Makita tools as well so I don’t have to pay those prices for a battery that does the same thing.
So even if I ended up spending a bit more now. I will be saving in Makita batteries in the long run.