Charger for an 18V Li-ion battery pack?

[PhilO]

I have a pair of cordless tools from Aldi which I’m very pleased with. But the bundled charger recently expired in a puff of smoke, and a replacement is not available so I’m looking at alternatives.

I reckon that if I can find a suitable universal charger for a 5-cell (18-20V) Li-ion battery, I should be able to connect it to the terminals on the existing charger so that I can still use that as a docking station.  The original charger only has two contacts (although the battery has 4) so I assume that it doesn’t have any fancy-pants cell-balancing features or anything like that.

Can anybody suggest a suitable charger?

[grams]

Have you checked eBay? There are usually scalpers on there with Aldi/Lidl power tool stuff.

Any bench power supply set to 21v max will do the job. I never bought a charger for my Aldi power tools.

[Kim]

Power tool batteries without cell balancing don't tend to last very long (DAHIKT), but it's entirely possible that the electronics for that are in the battery, and the charger does little more than supply voltage.

I'd probably use a bench power supply for this sort of thing too.  Not least because I've already got one, but the ability to set voltage and current limits means you shouldn't need the Explosion Containment Pie Dish™

[PhilO]

Sadly, I haven't been able to find what I want on Ebay, or anywhere else.  It's Work Zone branded, but made by Walter, and I'm 99% sure that I need this charger: https://www.walteronline.com/en/accessories/charger/21v-battery-charger-p10875 which is listed as 'not available'.

A bench power supply is an interesting idea...  That's a more expensive solution than I was looking for, but but 'future proofs' me to some extent which might justify the extra expense.

So if I was to take that approach, would I be right in assuming that setting the power supply to the settings indicated on the label of the original charger (in this case 22V* DC, 2.3A) or slightly lower current** would be the way to go?

If the power supply is regulated to a fixed current, is there an increased risk of over-charging? Should I use a timer?

Just picking something at random off Amazon, are we talking about something along the lines of this?  https://www.amazon.co.uk/Variable-Digital-Adjustable-Regulated-Switching/dp/B08MXK4T6Z/ref=psdc_1938320031_t1_B08L8SHMKC


* I notice that another charger (nominally 20V) I have states an output of 21V, as mentioned by Grams.
** Given slow-charging generally AIUI is better for the battery.

[grams]

Lithium cells are fully charged at 4.1-4.2v, 21v would be a reasonable maximum for five in series. 22v seems a bit high. It may be that the charger never outputs that much to the cells.

Current isn’t particularly important as lithiums can generally take as much as you’re likely to point at them without exceeding the voltage limit. A rule of thumb for maximum charge current for unknown cells is 2C = twice the capacity in Ah = 4A for 2000 mAh cells.

[PhilO]

*Makes a note*

Ta! 

[BFC]

What color are the tools.

I have a spare charger for the blue version, but I don't remember them doing bundles in that version (which is why I have a spare charger and a another that I am willing to pass on!).

[PhilO]

Thanks for the offer! Unfortunately it's the red 'Workzone' branded one. The blue one is a slightly more sophisticated charger and doesn't quite fit.

[Kim]

If the power supply is regulated to a fixed current, is there an increased risk of over-charging? Should I use a timer?

The way a typical bench power supply works is you have a knob for voltage and a knob for current.  Typically, you'd turn the current limit up high enough that it doesn't come into play, set a voltage and treat it as a voltage source (think thing-that-behaves-like-a-battery), supplying a regulated 5V or whatever for your circuit.

Alternatively, you can flip this on its head, turning the voltage right up, then (probably with the output terminals shorted, so you see something on the current meter, unless it's a funky digitally-controlled one) twiddling the current knob to set some value.  Then it behaves like a current source, with the voltage rising to whatever value is needed to push the desired current through the load.  Sort of thing you might want to do to heat up some nichrome wire to cut foam, or drive some sort of electro-chemical reaction.

For battery charging, you'd do a combination of both.  Starting with the output shorted, you'd turn the voltage right up and set some desired current.  Then you'd disconnect the output, and twiddle the voltage down to whatever is the safe limit for the battery.  Now when you connect the battery, the voltage will rise as high as needed to push your desired charging current, but only up to the point where the voltage limit is reached, at which point the current will start to drop.  Effectively, it acts as a constant-current source, then switches to being a constant-voltage source as the battery voltage rises.  Which is about 95% of what a battery charger does (the rest being things like temperature monitoring, cell balancing, timeouts and clever cycling modes to rejuvenate the cells).

A timer's not a bad idea, because there are battery failure modes where it keeps taking power, but does unhelpful things with it like boiling the electrolyte or generating hydrogen.  See also: Explosion Containment Pie Dish™.  I wouldn't charge a lithium-ion battery like this unsupervised, at least not unless you've done it several times before without issue.  Also note the hazard of inviting twiddly knobs that can cause Bad Things to happen if there are other people around (especially those prone to unthinking Tidying Up or who don't respect "Nicht gefingerpoken!" signs).

[PhilO]

Thanks Kim! That's an excellent explanation, as ever! 

[quixoticgeek]

And for everyone else, this is a lesson in why when ever we have a "What battery power tool?" thread, we all say get a named brand like Makita. Cos sure, the lidl/audi/gamma stuff may be good to use, and work well enough. But will you be able to get any parts for it in 6 months or 2 years time?

J

[grams]

I think my collection of Aldi cordless stuff (3x batteries, jigsaw, drill, multi tool) cost around £100 all in, which is likely around the entry cost for one proper brand tool and battery.

They all take generic blades/bits. I am knackered if one of the tools packs up, or I decide I need a cordless toothbrush or food mixer or whatever.

(though there are 3D printable battery adapters if I want to switch to something green or teal)

[Kim]

Adaptors do seem to be making the buy-in-to-a-battery-system thing less critical than it used to be.

Obviously the Aldi tools aren't up to the quality of Makita et al, but they're still good value for money.  If they were compatible with a mainstream brand's batteries, they'd be ideal for light use.

(I killed my Aldi oscillating multi-tool by using it for too much sanding.  Replaced it with the Makita 18V to match my Makita drill, which was a revelation in terms of how much vibration it doesn't channel directly to the user's median nerve, even if it is designed for enormous builder hands.

[iandusud]

I have used many power tools for decades and I have learned that you can get away with some very cheap mains powered tools that work remarkably well but cheap cordless tools can't hold a light to good ones. I have found Makita cordless tools to be excellent and in the long run cheaper than replacing cheaper inferior ones. I have recently bought a Makita DMP180Z cordless compressor as I'm having difficulty using my track pump due to a wrist injury. It's fantastic bit of kit as you would expect from Makita. It wouldn't be a cheap option if you don't already have Makita LXT kit and needed to buy it with battery and charger, but if you already have a charger and batteries it's a great buy.

[tonycollinet]

does this one hack it?

https://www.zoro.co.uk/shop/not-categorised/not-categorised/battery-charger-20v-lithium-ion-for-cp20v-series/p/ZT1225213P?utm_source=cj&utm_medium=affiliate&pub_w_id=8739971&utm_campaign=affiliates&cjevent=019cf5cada3811eb825d73bd0a18050f

[PhilO]

Well, it's been a while (which says a lot about how much I use these tools!) but I finally got around to recharging these batteries with a cheap bench power supply as suggested by Grams and Kim. Worth the £60 spent, I reckon, as it'll be useful for so many other tasks and at least delays needing to replace the tools. 

The charger output is only two pins, so I assume cell balancing (if any!) is done internally.  I simply removed and binned the internal circuit board and recycled the mains cable to connect the pins to the power supply.  With V set to 21V, current slowly dropped to zero and the batteries both indicate full charge. They may or may not last as long as with the original charger, but will certainly keep going for longer than they would have with the charger broken! 

Thanks all! 

[sprogs]

Chargers for RC model batteries are good value and also charge lithium, nimh, nicd, lead acid and such.
If you send me a pm I'll find out what mine are and let you know.
Liz

[lissotriton]

Chargers for RC model batteries are good value and also charge lithium, nimh, nicd, lead acid and such.
If you send me a pm I'll find out what mine are and let you know.
Liz

I have a SkyRC charger. It has plenty of options for different battery types, up to 22V. And a variety of connections, include balance and temperature monitoring.
Something like this. SkyRC Imax B6 Mini. https://www.aliexpress.com/item/32847556295.html