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SERVICEMAN’S LOG Power tool batteries, part two Dave Thompson If you read my November 2023 column, you will recall that I have recently had some run-ins with troublesome power tool batteries. I might have opened a can of worms by relating what I went through with my yellow power tools to my friends! You may recall me going through the motions of jump-starting some dead cells in my less-than-two-yearold battery pack and having some success in getting it working again. By working, I mean it was at least working enough for me to keep using the garden tools in their intended roles. Sadly, while it appeared the resurrection was at least partially successful, the rosy after-glow didn’t last, and soon the pack was back to its old trick of not lasting for more than a few minutes in the tool, and worse, nor was it being ‘seen’ by the charger. There was only one possible recourse: to take it back to the big-box vendor I’d purchased it from and thrash it out with them. Surprisingly, I met with almost no resistance (pun intended!), and they openly acknowledged it was a known problem. Even though the pack was literally one day out of the two-year warranty (pure coincidence – I had no idea, and thought it was a lot younger than that!), they said they’d put it back through the repair system with the caveat that it was entirely up to the yellow tools manufacturer as to whether they would honour the warranty. They also warned that obtaining a resolution could take up to four weeks, whichever way it went. However, being the good retailer they are, they gave me a loaner battery from their pool of spares in the meantime. This involved digging through a rather large box of batteries designed for various tools from many different manufacturers until we found an 18V version of the 54V battery I’d be leaving there. 82 Silicon Chip This was fine by me; the tool I needed to use (a weed whacker) would run on 18V anyway. I was mildly concerned when the woman dealing with this process informed me that this box of loaner batteries was never charged, with the store relying on people bringing them back after borrowing with some level of charge in them. I very briefly considered going into why that might not be a good idea and that leaving them to discharge in the box for what could be considerable lengths of time between charges might hurt them, but I wisely considered against doing so. It was simply not my place. All I cared about was that the loaner battery they gave me worked, and as a press of the onboard test button showed one bar of residual charge, I thought it would be fine after a decent time on my charger. And it was. Being the smaller type of battery for this range of tools meant it likely didn’t suffer from the design flaw that left the three cells buried furthest into the three chains of cells in the 54V version vulnerable to failure. I got the work done (that was my priority), and a mere three working days later, I received a text message saying that the battery I’d dropped off had been replaced under warranty and was ready for me to pick up. Could I please charge and bring back the loaner battery? I duly did that the following day. It was a good result, then, and a lesson for me to try to remember to keep my new 54V battery topped up to minimise the chance of a repeat performance. It is also good to know this new battery also has a two-year warranty, so if it happens again... Professional tool batteries fail too Since all that occurred, I related this tale of battery challenges to a few friends in the building trade as I was interested in their experiences with their cordless tools. Especially given that they usually use ‘professional’ level tools that are typically much more expensive compared to the lowly DIY versions the rest of us buy. I found their comments fascinating, and it seems that suddenly, I’m a local expert in battery tools, ready to be consulted! Of course, I’m no such thing, but this is very flattering. What I got from talking to these guys is that certain tools within the building and construction industries are well known for having inherent faults – and not just batteries. Most avoid them if they possibly can. Of course, manufacturers want people to ‘plug in’ to their Australia's electronics magazine siliconchip.com.au Items Covered This Month • Power tool batteries: electric boogaloo • Sometimes all a tractor needs is a good whack • Repairing a Dell power cable adaptor Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com range of tools, but it can be a considerable investment in plant and machinery only to discover that all might not be right in the state of Denmark. Nothing is worse than that feeling of remorse we get after spending thousands of dollars on a tool ‘system’ to find that the gear we’ve just purchased might not actually live up to the marketing hype. For example, many ‘sparkies’ here use a particular brand of drill/driver because it has a movable, asymmetric chuck assembly that allows holes to be drilled very close to a wall, off-centre from the centreline of the drill. That is a very cool feature. However, the batteries in these things are notoriously unreliable, and many of these guys now have their drivers lying useless in their toolboxes because the batteries are dead. The packs are no longer widely available, and those that are can sometimes cost half the price of a whole new tool, which comes with two new batteries! That is just another example of companies making consumable products with built-in finite lifespans (commonly known as ‘planned obsolescence’). Many of these guys either don’t know about repacking the battery pack with better cells, or if they do, they just can’t be bothered waiting and, in a fit of remorse, simply go and buy a new and likely different brand of tool. Of course, they probably believe that the new tool will come with a better generation of batteries and chargers, but we all know that is not necessarily the case. And the cycle continues. My neighbour kindly came over the other day to trim some of the wayward branches of the bushes growing on his property that overhang my fence. I sometimes get my manual loppers out (no batteries!) and knock back some of the bigger ones that get in the way of my bins. Still, he has one of those dayglo-green tool systems, including a rather tasty extendable and powerful hedge trimmer. Since some of these bushes are more than three metres tall, it’s a helpful tool to have. I’d love one of them in my yellow brand system, but I checked, and the cost is prohibitive for the amount of time I would use it. I asked my neighbour about his batteries, and being an 18V system, he commented that they seem to be OK. He has had the batteries since new for several years and keeps them refreshed religiously. They hold their charge, and as I hear his range of tools doing a lot of work over the fence; perhaps that is what keeps them healthy. I don’t use mine a lot; maybe once a month in the garden. Either way, it’s interesting... Repairing another failed battery pack I now have several packs and chargers in the workshop. The packs all come apart easily enough; while a siliconchip.com.au Australia's electronics magazine April 2024  83 the chips, a data sheet may have sample circuits that can be very similar. Thankfully, spares seem to be available from various sources. It also seems that a BMS from one pack can sometimes be used in a different brand of battery pack as well, but I have not fallen down that rabbit hole... yet. So it isn’t just about dead cells, although that’s where most problems seem to start with these packs. The electronics are robust since they have to be, but if a cell dies through not being charged properly, the whole pack is ruined. Simply replacing the cell(s) may not fix ongoing problems; the same cell could just fail again. Perhaps the manufacturers assume or hope that by then, the tradies will just buy another updated version of the tool instead. Welding in new cells couple had those Torx-type security screws buried down in the plastic moulding, the long bit for my driver easily reached them. They must be done up by a robot or someone with a mechanical driver because many were screwed in very tightly. There was no evidence of Loctite, Nylock or other type of adhesive on the screws, so I guess they were just done up very well. All the pack clamshells split apart to reveal the train of cells and a PCB of varying quality inside. I could see straight away that a few cells had vented – no prizes for guessing which ones could be dead! This is a pervasive problem with these 18360-type cells. They are the most-used cell in battery packs for tools because they are widely available and, if pushed, can deliver a very respectable 20A of point-load current when the tool is under stress. The problem is that the quality of these cells varies widely between manufacturers, and just because a cell has 2500mAh printed on it doesn’t necessarily mean it can deliver that promise. I have purchased many of these ‘replacement’ cells over the years from various vendors; honestly, some are just not worth the money. The problem is, as an end-user, how do we know? I guess all we can do is swallow the much higher prices of local vendors in the hope that the cells are of better quality than what we can buy from cheap Asian sites. There’s also the advantage that we can return them in case of premature failure. There isn’t much solace in that, though, when our customers come back complaining that the quality of the repair I carried out doesn’t live up to expectations! The other concern is that most battery packs now include a Battery Management System (BMS). It is usually in the form of a circuit board stuffed with surface-mounted components. It is there to regulate charging by apportioning the right current to the banks of cells themselves and to protect the cells in case of a short circuit, or if someone stalls the tool in use and the cell temperatures skyrocket. This PCB can also fail, causing the pack to no longer work or be seen by the charger, and this can be a trap when troubleshooting battery problems. As is typical, no circuits exist for these boards, although if you can identify 84 Silicon Chip For those of us who want to keep our existing tools going, though, repacking is the only viable option. Of course, there are plenty of local companies who do that kind of work, but it is well within the scope of the DIYer, as long as we can get good replacement cells. It also helps to have a spot welder because soldering to these cells is often problematic. I’m not saying it can’t be done; I imagine we’ve all done it or at least tried it at some point, but we have to be very careful of imparting too much heat for obvious reasons. I’ve also come across cells that must use a different type of metal on the caps, because no amount of sanding or application of flux will allow solder to stick; it annoyingly just beads and falls off. The splat welder method is achievable because they sell these relatively cheaply over on the likes of AliExpress, eBay and Banggood. They typically run from a high-­current model plane or car battery and do the job quite well. Editor’s Note: for a more capable version, see our Capacitor Discharge Welder project from March & April 2022 at siliconchip.au/Series/379 Mine has seen some use, and I much prefer this method to soldering because it is fast, easy and more permanent. The nickel strips can be purchased very cheaply too, in a roll, with different thicknesses available. It’s just a matter of cutting them to size, touching the welder to the strip once it is in place and ‘zap!’, it’s done. Another customer’s battery won’t charge I also had a case recently where a customer’s battery charger stopped working. That’s also a showstopper for many because a new charger can be expensive, especially if it is part of one of these ‘systems’ that use one battery for every tool in the range, which seems to be all the rage now. In this case, the battery checked out OK, with all the cells carrying a reasonable charge and being within 10% of each other in voltage, but the charger didn’t show any lights at all. The owner said he put the battery on to charge as normal, but nothing happened. The usual lights and fans didn’t come on, so he put it to one side and assumed that the battery had tanked. The charger comes apart as easily as the packs after removing the usual security screws. Since everyone has these bits now as part of kits we can buy from the local big-box store, what is even the point of using them? The fact is, these days, they present no real problem to even the most inexperienced DIYer. Australia's electronics magazine siliconchip.com.au As expected, the PCB inside is stacked with the usual mix of surface-mounted and through-hole components. As you’d also expect, there is very little information about these things online from the manufacturer. However, many people have delved into the inner workings and have posted their findings on the likes of YouTube. This is gold for those looking to repair the most common problems. Of course, some of the information isn’t relevant at all, but some is, and that’s what I was looking for. Apparently, with this charger, a couple of resistors can fail and replacing them can restore functionality. I checked and discovered one had been blown off the board. It was a surface-mounting device, but I replaced it with a standard 1/4W axial resistor, as suggested in the video. I also replaced the other prone-to-fail resistor and followed other recommendations to check the input power diodes, which look to be old-school 1N4007s or similar but, in typical fashion, have had their designations removed. They were all OK, as was every other component I could ring out with my multimeter. I reassembled it, installed the battery and was welcomed by the lights and a fan kicking in. It was a simple enough fix, but you’d think the people who make these things would have tested them thoroughly and known this could happen (basic engineering should have also revealed whether the resistors were undersized for the job). The issue is that by the time they sell these tools in stores, they’ve already made a million of them, and there’s likely a new model already being manufactured. There would be no recalls of such products unless there were a threat to health and safety. Still, all in all, there is a reasonable resolution for most of these jobs. The repacked or replaced batteries keep the tools going, while the dead charger is now charging. The customers are all happy, so job done! The tractor that dropped in its tracks R. M., of Scotsdale, WA found that even elementary electronics can have gremlins lurking. Sometimes, you must attack every possible failure point before you can evict the gremlin! On a farm, even a small one like ours, the most useful tool is the tractor. The compact three-cylinder diesel fourwheel-drive with power take-off, three-point linkage, dualrange continuously-variable hydraulic transmission and 4-in-1 front-end bucket is a modern marvel. Think of it as a 30 horsepower (22kW) Swiss army knife! We have a Korean-made “KIOTI” CK3010H tractor (pronounced “Coyote”). It’s a clever marketing strategy since Kioti sounds better to Western ears than “Daedong”. It even has a small bushy-tailed canine howling at the moon as its logo. I have had it for nine years and it has never failed me. That is until... I had driven it down to the lowest and most remote paddock (isn’t that always the way?) and turned the engine off. I did the required work, loaded the bucket, got back in the seat, pressed down the clutch pedal and turned the starter key. There was plenty of vigorous cranking but no starting. With a diesel engine, there is no ignition system to worry about and no electronic fuel injectors either. Just a mechanical high-pressure pump that squirts fuel into the cylinders as required. siliconchip.com.au Diesels are very fussy about the cleanliness of that fuel and I had been a bit slack with maintenance. I had bought a new filter kit, changed the engine oil and filter, but I hadn’t gotten around to the fuel filter. So I trudged back to the shed, got the new filter and appropriate tools and replaced the rather mucky filter in the field. The engine started without any delay! As you’ve probably guessed, that wasn’t the fix because the story doesn’t end there. It wouldn’t start again a couple of days later. Could the injectors be clogged? They can’t all block simultaneously. So it had to be the engine stop/ start solenoid. For petrol engines with spark plugs, stopping is not a problem. You can stop sparking, and the fuel cannot ignite; it’s also possible to close the throttle butterfly to cut off the air intake to the cylinders. Diesels don’t have throttles; their power output is controlled by fuel metering. With a diesel, because the fuel is ignited by cylinder compression, the only way to stop it, short of stalling it, is to cut off the fuel or, failing that, block off the air intake by jamming something into it. On the old machines, there was a lever on the injector pump and a bit of fencing wire that came up to a knob on the dashboard. Modern key-starting diesels use a hefty solenoid to perform this function. I knew where that solenoid was, so, assuming it might just be stuck, I gave it a sharp rap with a large wrench (I didn’t have a hammer handy). Editor’s note – any tool is a hammer when you need it to be. The tractor started first go. Problem solved? Oh no, it wasn’t! The misbehaviour continued intermittently. But a smart tap with whatever weapon was available did the trick. But that isn’t a proper fix, so I went a-Googling. I found a replacement part from an Australian source that wasn’t outrageously expensive and ordered one. It turned up two weeks later, and I swapped it out; an easy job with a three-pin waterproof plug making the connection. Ah, that fixed it! Australia's electronics magazine April 2024  85 Two weeks later, at another remote location, “whirrwhirr-whirr-whirrrrr”, but no start. And this time, a rap with a spanner didn’t help. I trudged home uphill and went back to Mr Google. And for $20, I got a full 400-page PDF workshop manual instantly delivered to my computer. This showed that the solenoid had two windings: a strong pull-in winding and a light-duty hold winding. The engine management computer feeds voltage to the hold winding and then puts a one-second pulse to the pull-in winding. With a hefty dose of amps, the solenoid plunger thumps in, the holding winding keeps it in, and the fuel flows until the ignition key is switched off. Now that I had a spare solenoid, I was ready to find out if the fault was the solenoid or (shudder) the injector pump. All I had to do was wait until it failed, swiftly switch the connector over to the spare external solenoid and watch the plunger pin. Sure enough, I confirmed that the plunger was not pulling in. So it was an electrical fault! That was a relief of sorts; it is much easier to deal with electrics than the very complex and fine tolerances of a fuel injector! The pull-in solenoid was fed from a relay that was, in turn, fed from a 25A fuse. That could be the problem. A bit of corrosion and a heavy current demand can result in a big voltage drop. I needed to find the fuse box. By rights, it should be on the firewall. The thing about compact tractors is that they are compact; everything is crowded together, especially under the bonnet. Also, the wide arms that raise and lower the bucket pass close by either side of the bonnet. Raising the bucket to its height limit and fitting the safety bars gave a bit more access, but lifting the bonnet didn’t help that much. A generously proportioned air cleaner obscured my view of the firewall. After much struggling with hidden clips and twisting hoses, I had a partial view of the firewall. And there was a fuse box that appeared not to be completely closed. Was water getting in and causing a bit of corrosion? Working primarily by feel and bright torchlight, I managed to open the box and extract a fuse: 15A. Okay, not the right one. More wiggling and swearing, and I had a 25A fuse in hand. It looked fine. No sign of corrosion. I gave it a squirt of contact cleaner anyway and put it back. I did to all of them, just in case. 86 Silicon Chip That didn’t help, but the problem intermittency got a bit longer until the rains came. Now this malignant fault had a new trick! The probability of failure was directly proportional to the distance to shelter and the volume of wetness. And then I had a breakthrough! When I turned the start key, just before the starter motor spun up, there was a faint click. I had assumed this was the starter solenoid, but what if it was the fuel stop/start solenoid? By locking the clutch pedal down, jacking up and securing the bucket out of the way again, and contorting myself, I could get one hand on the solenoid and also reach the starter key. And that was it! That click was the fuel solenoid, and sometimes it didn’t click. When it didn’t click, the tractor wouldn’t start! Going back to the wiring diagram, I found another diagram that showed more detail. The relay was fed from a 25A fused circuit, but the power it switched came directly from the battery with a 60A master fuse. The relay was situated on the firewall (of course it was). Still, at least this time, it was reasonably accessible. I managed to unbolt it and bring it out into daylight, dragging the wiring harness behind. I also found a damper diode effectively across the solenoid but packed away in its own little box taped into the harness. It checked out okay. The relay was a standard four-pin 70A type. Using the same hold, feel and activate technique, I determined it was working, but the solenoid wasn’t always complying. Obviously, the relay contacts were burnt out. A new relay from our friendly auto parts shop and, finally, no more no starting problems! The engine compartment of the tractor is packed with parts, making the fusebox and relay hard to get to. Australia's electronics magazine siliconchip.com.au So the 25A fuse I had struggled to access was just the relay activator, and the heavy current that operated the solenoid came directly from the battery via the relay. Now, there is a loud, healthy clack from the solenoid when the ignition key is turned. But here’s the catch. I performed bush surgery on the relay, and the internals looked okay – clean contacts and good snappy action when fed with 12V. So, is the gremlin still lurking, waiting to trap me? Three months and a lot of rain later and, fingers crossed, it hasn’t failed once. But is it still lurking? Time will tell. I now wait to hear the loud clack of the solenoid turning on the fuel before engaging the starter. Why was the fault originally ‘fixed’ by a tap on the solenoid when the actual problem was in a relay half a metre away? I put it down to pure Sod’s Law! That, and the downright evil malice of your typical intermittent fault. Repairing a Dell power cable adaptor G. C., of Cameron Park, NSW found that Dell laptops use various proprietary charging cables, causing all manner of problems... I recently retrieved a Dell laptop from my daughter that she borrowed a year ago. Annoyingly, it didn’t come back with an AC power adaptor. Naturally, the battery was completely flat, and the laptop wouldn’t turn on for even a second. Adding to my frustration, this laptop used the newer 4.5mm socket, while all of my Dell AC power adaptors had the older and larger 7.4mm connector. I wasn’t sure what to do. I didn’t want to spend a lot of money on a new Dell power adaptor when the laptop might have ‘expired and gone to meet its maker’. Feeling stuck, I decided it was time to do some Google searching. After, as usual, wasting some time on a few dead ends, I discovered that while Dell 7.4mm and 4.5mm connectors were virtually impossible to find, adaptor cables from 7.4mm to 4.5mm were readily available at very reasonable prices. I ordered several from an Australian supplier, which arrived within a week. However, when I connected everything and turned on the laptop, I received an error message that stated, “Alert! The AC power adaptor wattage and type cannot be determined. The battery may not charge. The system will adjust the performance to match the power available.” Annoyingly, the Dell laptop still wouldn’t boot up, most likely due to the completely flat battery that wasn’t charging at all. I verified this by going into the Dell BIOS (press F12) and checking the battery info, which showed it as charged to 0%. It wasn’t charging, and the power adaptor type was listed as “unknown”. Many laptop brands use just two wires in their power cables, but some, notably Dell and HP, use three: ground, power, plus a third ‘sense’ wire via a triaxial connector. Despite the adaptor cables being well made, they hadn’t bothered to include the important third sense wire! 88 Silicon Chip The centre sense pin is used to determine the adaptor’s power rating, allowing it to adjust the charging current to prevent overloading or overheating the AC power adaptor and avoid tripping its 19.5V DC power safety circuitry. Based on my past experience with Dell laptops, I knew this error could be caused by either a non-genuine power adaptor (which wasn’t the case) or a good power adaptor with a damaged sense connection. I knew the AC power adaptor was fine as it worked on another Dell laptop with the larger 7.4mm socket. It appeared that my brand new 7.4mm to 4.5mm adaptor cable was defective. This seemed strange since, externally, at least, the adaptor cable appeared well-made. However, a quick check with an ohmmeter revealed a different story; the sense wire wasn’t connected between the adaptor cable’s male and female ends. The identical issue was present in all three adaptor cables I had purchased. Even more strangely, on the plug end, I measured a resistance of 200kW between positive (19.5V) and the centre sense pin. Since these adaptor cables were less useful than a brick for their intended purpose of charging a laptop, I decided to take a closer look inside (the Serviceman’s Curse). I cut off the soft plastic from the plug and socket using sharp side cutters. It was tedious, but it worked. My initial assessment was accurate, as both the plug and socket were indeed well made. Interestingly, both had the correct three connections. However, in what has to be one of the most nonsensical designs I had ever seen, the wiring loom only had two wires, not the necessary three. The reason for the 200kW resistance on the plug became apparent: some engineer, in a futile attempt to trick the Dell sensor logic, had added a 200kW resistor between + and the sense pin. Needless to say, it did nothing useful, as the Dell BIOS error message confirmed. With the problem laid out before me, the solution was obvious: create a new loom using three wires. As a quick feasibility test, I desoldered the useless two-conductor cable and the kludgy 200kW resistor. I then quickly soldered three insulated wires between the 7.4mm socket and 4.5mm plug. Very carefully, I plugged in my temporary kludge adaptor (with its exposed 19V power) between the Dell power adaptor and Dell laptop and turned it on. Fortunately, everything worked perfectly, even with my dodgy exposed wires. Nothing had come into contact with anything untoward to produce that annoying smoke that electronic devices seem prone to emit. Of course, I needed a permanent and more durable solution. So, I decided to do it properly with 3D-printed replacement covers. I fired up OpenSCAD and designed covers for both the male and female connectors. After careful measurements with digital callipers and a few iterations to fine-tune everything, my 3D-printed replacement covers fit perfectly. After that, it was smooth sailing. I desoldered the three temporary wires, and since I didn’t have any suitable three-core cable on hand, I used a short length of Hakko soldering iron cable, even though it had five wires. After soldering this new cable between the 7.4mm and 4.5mm connectors, I fitted the covers and sealed each end with neutral-cure black silicone. Voilà, I had a professional-­ looking Dell 7.4mm to 4.5mm adaptor cable. Even better, this adaptor cable actually worked. SC Australia's electronics magazine siliconchip.com.au