Does anyone have the Bosch "12V" system?

[Eric The Viking]

If you do, please can you have a look at the data plate on the underside of the charger - what does it say for its output?

It ought to be something like this*, probably at the bottom left of the panel:

                 ___
Output: 10.8V DC --- 3A

If it says 12V DC (or any other voltage), I'm keen to know.

I think I've just twigged why Bosch went through an expensive product repositioning process recently ("10.8V" becoming "12V"), and it may very well not be a positive step (unless you're Bosch).

If anyone has got an older charger that outputs 10.8V (as mine does), you might want to hang onto it.

E.

*('scuse the ASCII art - supposed to be a solid line over three dashes, in line with the lettering).

 

[Rorschach]

What do you think you have discovered?

 

[Sideways]

It's all marketing bull***t !

The generally accepted voltage of a lithium cell is 3.6V so a 3 cell series powerpack is 10.8v and 5 cells series is 18v.
You can have typically one, two or three strings of series cells wired in parallel to give you more capacity (amp hours) at eithor of the standard voltages.

Unfortunately dewalt's marketing department decided to name their 10.8v packs "12v" because it sounds better and customers who don't know any better think more volts = better. They call their 18V packs 20V and their 54v flexvolt packs 60v in the same vein. They aren't any different from anyone else's packs with 3, 5 or 15 cells in series.

The only way they get away with this is that a lithium cell hot off the charger registers about 4.2v per cell, which settles pretty quickly back to 3.6 under load. So yes, there will be a short period when a fully charged "10.8v" pack will meter as above 12v.
The chargers won't be the slightest bit different and it doesn't matter a jot if you were to charge a "12v" pack with a charger labelled 10.8v.

All bosch did was eventually copy Dewalt and then Milwaukee (TTI) in poor practice because Joe Punter doesn't realise they're being manipulated and it must have been costing bosch in sales.

I'll just add that intelligent charging of a lithium rechargeable starts with constant current charging (the voltage varies intelligently to maintain a constant high current into the cell untill it's charged most of the way - with the charge rate reduced if the cell starts to get too hot), then it switches over to constant voltage charging for the last 10-20% (?, I forget the percentage). When full. Charging stops but if the cell is left on the charger long enough and voltage sinks enough, the charger will top it up.

The last gem I recently discovered is that fully charging a lithium pack before putting it away for storage is bad for it. If you limit charging to 65% of full before you put a cell away for storage you'll get between 50% and 100% more charge discharge cycles out of it. I'm comparing like with like. A "cycle" is "full to empty" for that pack whether you do it all in one go or use 1/3 capacity at a time and top up three times.

 

[adt]

I was under the impression (from working with a bit of battery pack design in my day job a couple of years ago) that in the EU companies had to use the nominal cell voltage and couldn’t “trick” customers by using the higher maximum cell voltage.

So in the UK/EU you might find a battery pack as being labelled at 18v when the same thing sold in the USA would be listted as 20v. No actual difference between the two packs (apart from the label), just marketeers knowing that most people will see 20 as being better than 18.

I hope things haven’t changed to allow this sort of stuff over here but if it has I guess it’s not the end of the world as it is only a change to label and not the actual battery.

 

[no idea]

It's just a label change - there was something on the Bosch website when it happened stating the 10.8v stuff was changing over to 12v in name only.

 

[Eric The Viking]

Thanks for all that, everyone.

This was prompted by me finding out that the military spec for using Lithium ion cells is to use at 3.6V/cell, and not to charge 3-cell packs right up to 12V, as doing that shortens their life considerably. And the military want reliability first, with other performance measures of lower importance.

Apparently you can get them to about 4.1 or 4.2V per cell, but this is Not A Good Idea, as the last 4% or so to fully charged is damaging over time.

It's a tiny change to the charger circuit or microcode (probably just one resistor value) to make it work at the higher voltage, pretty much everything else would stay the same, except for two things: tools would apparently be slightly more powerful and/or last longer, and battery lifespans would be shorter. But Bosch tools would do better in reviews/shoot-outs, AND they would sell more replacement batteries.

Regulations would probably require them to change the label on the charger if they had done that, hence my question.

I'm very much hoping , apart from the silly branding thing, they have otherwise left well alone.

E.

PS: I've left it too late for Santa now, so after Christmas I need to buy a few replacements. I also intend to have a go at re-celling at least one of my existing packs. There are some how-tos on the net, and I've done it before with NiCd packs and NiMH. The difference with rechargeable Lithium packs is that there is a final cell balancing step before reassembly, which is really important. You need current and voltage meters and ideally a current-limited power supply, all of which I have, so it's worth a go.

 

[Rorschach]

Problem with the modern smart chargers/tools is that when you re-cell they sometimes just don't like it.

I re-celled a pack that fully discharged itself, I am guessing a cell was faulty and pulled power from the other 2 resulting in a pack voltage that was too low and then the faulty cell let it's juice out and that was that.
I re-celled the pack and it charges up ok but it refuses to work properly in the tools, the chip inside them doesn't like something about the new cells.
Luckily as part of that kit I have a torch which is a "dumb" unit as it only draws a fraction of the current of a drill so there is no need for fancy circuitry inside, the re-celled pack works fine on the torch so it is now dedicated to that tool.

 

[adt]

You might find that you’ve used the wrong type of 18650 cells when rebuilding your battery pack and have some which can’t handle the high discharge current that most power tools require.

There are some fairly large differences out there in terms of 18650 cell capacity and discharge current rating. For a power tool I would guess that you would need cells with at least a 20A rating; there are plenty of these out there but (unfortunately) there are also a lot of counterfeit cells that have lower rated parts with new wrappers on the market.

You might find that you would get a working pack again if you swapped out all of the cells for something like Samsung ina18650-25r which seemed to be fairly common in big brand packs.

 

[Rorschach]

I took the replacement cells from a NOS battery pack as it was cheaper to buy a battery pack than it was to buy the cells on their own, and they came pre-welded. All I had to do was swap over the other internals and re-solder the wires to the pins.
If I recall correctly the cells were samsung.

 

[Eric The Viking]

... and, as I said in my PS, it is essential to balance the battery before use.

Basically this is charging the cells individually, stopping at a predetermined endpoint, and only then using the battery, so that in service the cells reach "full" charge together.

Lithium ion systems are picky. This will be my first attempt at re-celling one: I'll report back on anything that proves "interesting", but it won't be until Jan-Feb '19 at the earliest.

 

[Sideways]

This was prompted by me finding out that the military spec for using Lithium ion cells is to use at 3.6V/cell, and not to charge 3-cell packs right up to 12V, as doing that shortens their life considerably. And the military want reliability first, with other performance measures of lower importance.

Apparently you can get them to about 4.1 or 4.2V per cell, but this is Not A Good Idea, as the last 4% or so to fully charged is damaging over time.

Hi Eric, can you share a link or whatever to this. I'd be interested to read up on it.
In light of the research paper I read about storage at full charge shortening the life of lithium cell , it sounds very plausible. At least it will be easy enough to do. Just set a timer and take your packs off charge after (say) half an hour - forty five minutes instead of leaving them on indefinitely.

 

[AES]

Errrrr, Ummmmmmmm.

Sorry to be a dummy (it comes naturally to me) but I can't see the practical reality of how to do what you're all recommending.

Not being a professional I buy my battery drills on price. That means I have a Bosch (10.8V Lion) drill, a DeWalt drill (also marked 10.8V Lion), and an Aldi drill (marked 18V Lion). All (of course) have their own chargers (apart from the voltages, the contacts aren't compatible with either of the others).

But that's no problem, I have 3 chargers in the shop and use whichever is required.

Each drill has 2 battery packs per drill, and simply enough, as each battery runs down (drill slows down) I simply change the battery and put the "flat" one onto the appropriate charger.

Each charger is a "simple" one, i.e. there's a light that flashes when the battery is being charged and which changes to steady (or in one case simply goes off) when the battery is "fully" charged.

At no time in any of the charging cycles in any of these 3 different chargers is there any indication at all of "whereabouts in the charge cycle" I am - i.e. the indicators simply says "I'm charging" or "I'm not charging any more".

Similarly, when I stop using a drill, unless it's fully run down (i.e. running very slowly/almost stopped) I have no idea whereabouts I am in the charge state - beyond guessing that it's somewhere between "flat" and "fully charged".

So how on earth do I know when to stop a charge before it stops fully charging, so ensuring that I put the drill away with a battery pack that's not fully charged, as you all recommend?

It's clearly NOT just a matter of "stop charging after X minutes" because I've noticed that sometimes it will take a lot longer to charge a "flat" battery pack than it does at other times (I'm talking about the same battery pack here).

Same question applies to storing the 2nd battery pack for each drill. I can either not charge it before I put it away, or put it away fully charged. But I can't see how to do anything in between.

So without special electronic lab gear like I can see EtV has, I have NO chance of knowing whereabouts in each charge cycle I am with any of these 6 battery packs, not the 3 installed in the tools, nor the 3 spares.

Hence my Q at the start - how in practical reality can I do this, as you recommend?

Signed "puzzled of Woking"!

 

[MikeJhn]

In reality don't bother, I have some Lion (LiFe) batteries, some where put away discharged and some fully charged been out of use for over two years, both sets re-charged perfectly, cycled and checked, but have to add these are Lithium Nano Phosphate cells, ie the original A123 batteries and not the clones that most manufacturers use, except that is DeWalt on their 24volt systems of about five years ago, now also clones.

The better Lion batteries do not gradually diss-charge in use, but will fall off a cliff and stop, its when users do not recognise this and keep using the unit until it will not run, that is when/how the cells are damaged.

Mike

 

[Sideways]

Over discharge kills Lithium cells, so most lithium ion cells (unlike nicads and NiMH) have a small electronic circuit built into the end that shuts the cell down when the voltage falls to a level a bit above what would harm the cell. You can't over discharge these / reverse bias a cell (which is what used to kill so many previous technology battery packs) because the protection circuit in the weakest cell will cut in and stop you doing any harm. Nonetheless as soon as a cordless tool starts to slow down and struggle, it's time to recharge.
Also, lithium rechargeables handle storage relatively well but good practice it to charge them to at least 50% before storing and pull them out for a top up at least every 6 months.

Part charging a battery doesn't seem complicated to me. Run it until empty or down to one bar on the battery/tool gauge. Charge until you get it up to 2 of 3 (or 3 of 4) bars - try 15, 20 or 30 minutes (just try it and see). That should be good enough.

 

[skelph]

No offense intended but I'm totally confused by the contents of this thread.

AES said -

Each charger is a "simple" one, i.e. there's a light that flashes when the battery is being charged and which changes to steady (or in one case simply goes off) when the battery is "fully" charged.

sideways response was -

Part charging a battery doesn't seem complicated to me. Run it until empty or down to one bar on the battery/tool gauge. Charge until you get it up to 2 of 3 (or 3 of 4) bars - try 15, 20 or 30 minutes (just try it and see). That should be good enough.

Where do the bars come in to the equation? The only bars showing in my workshop are on my mobile and I don't see how they are related to the state of my DeWalt NiCad batteries.

We appear to be comparing lemons to melons (same letters but different articles)

skelph

 

[AES]

Thanks for that sideways! There are NO (I presume charge state) indicator bars on any of my tools! The tools either run or they don't, though I must admit, towards the (obvious) end of a charged up pack you can hear the tool noticeably slowing down, especially if under load. But the time that can take (from "full" to "flat") is very variable

Perhaps I've got hold of the wrong end of the stick (wouldn't be the 1st time) and I really am comparing lemons with everyone else's oranges

 

[MikeJhn]

Over discharge kills Lithium cells, so most lithium ion cells (unlike nicads and NiMH) have a small electronic circuit built into the end that shuts the cell down when the voltage falls to a level a bit above what would harm the cell.

Now that made me smile, hyperbole at its best.

Mike