Now that the 4.0Ah and 5.0Ah batteries are the same price, which are you buying?

[onocoffee]

I'm all for small batteries on hand tools like drills etc but I'd rather buy the older 3Ah batteries than those modern high power 4Ah ones. I've had a 100% failure rate on them after about 3 1/2 years each - right out of warranty. My 3Ah, 5Ah and the ones for my CXS are between 5 and 10 years old and work like a charm. Guess what they all have in common? They were not yet produced in China...

Oddly enough, I've got a bunch of DeWalt 20v batteries that are well over a decade now (that still work very well) that were also made in China...

 

[COBill]

I've had a handful of Milwaukee batteries die but by far the most robust batteries I have are Makita's.

I regularly use LXT batteries that are almost twenty years old with no real loss of capacity.

 

[Coen]

I don't get why people love the smaller batteries.

I'd run everything with an 8.0 attached if I could afford them;

Why would you? Festool is about ergonomics. The 8 Ah battery is just too much weight and bulk in most tools.

I've had zero failed 4.0 Ah batteries and have eight.

I have the similar Bosch packs. I have 8;
1 I got broken (I rebuild entire pack)
1 had leaking cell (I replaced 1 cell)
Then another one with leaking cell
And the one I replaced a cell is again leaking

All with Samsung 21700-40T cells. At least they are only €3/ea.

Never had such a failure rate with 18650 based packs. Especially not the nasty leaking variety.

They were not yet produced in China...

That isn't really a thing anymore.

My "American" Fluke 179 multimeter came with a soft case (probably made in China too) that didn't even fit it's super thin TL910 measuring leads properly. The leads suffered internal breakage in no-time too by the way.
My "Chinese" UNI-T UT161E at less than half the sticker price 15 years later came with a soft case too... it doesn't feel as high end but at least it fits the measuring leads and the leads don't break. And also these leads are better than those supplied with an earlier UNI-T purchase. It also came with a nice block with sockets to easily test resistors, capacitors, etc. Something Fluke apparently didn't even bother to even design.

I've had a handful of Milwaukee batteries die but by far the most robust batteries I have are Makita's.

I regularly use LXT batteries that are almost twenty years old with no real loss of capacity.

Oh they definitely have loss of capacity. Even when not used they degrade.
In the past Makita used to feed it's BMS from once cell... causing it to deep-discharge and brick the pack when stored too long.

 

[Cheese]

I don't have any tools that would work with those.

I've had zero failed 4.0 Ah batteries and have eight.

Consider yourself fortunate... ...I have 4 of those batteries and I'm at the 50% level.

 

[COBill]

Why would you? Festool is about ergonomics. The 8 Ah battery is just too much weight and bulk in most tools.

I want the most power available without worrying about the battery.

I do the same with other tools - I have some Milwaukee M18 tools and they all have 12.0 FORGE batteries attached, and I use the biggest available batteries on other tools.

 

[COBill]

Consider yourself fortunate... ...I have 4 of those batteries and I'm at the 50% level.

I buy all my Festool tools in the "Plus" packs, so they each have their own dedicated charger and batteries.

I believe in being able to grab the Systainer and go without having to dig for batteries or a charger.

 

[onocoffee]

Outside of drills and drivers, most of my tools are corded. I do have a Hercules compact router that I got with their 5Ah battery. That works fine but the battery makes it top-heavy, so as soon as they had them on sale, I got the 2Ah batteries. Much more comfortable to operate.

 

[Imemiter]

I got two of each when the price dropped. Two 4.0s as backups for the CTC-Sys, and the 5.0s in anticipation of buying a SCMS or the CSC Sys 50. Then something snapped and now I think I'm going to ride out what work I've got in the hopper and retire to the odd door job or two a month. I had a couple of those 3.1s but gave them away with my T18+3. I never really noticed them being all that light. But I gave the drill to my brother so I could always trade him some 4.0s and get them back I suppose.

 

[Cheese]

The 3.1's are really nice on a small, light tool such as the OSC 18.

 

[Coen]

I want the most power available without worrying about the battery.

I do the same with other tools - I have some Milwaukee M18 tools and they all have 12.0 FORGE batteries attached, and I use the biggest available batteries on other tools.

In most tools it won't even yield you more power. Just more runtime. But either way it takes you more power to lift them.

In fact; I have wanted to get a (Bosch pro) 18V 2 Ah (single row 18650) pack for a while now. But never did so far. Just to save the ~160 grams compared to the 4 Ah (21700-based) packs.

 

[Michael Kellough]

A little off topic but I have several 18v Metabo tools (made in Germany Metabo) and batteries ranging from 2 amps to 8.
One thing that puzzles me is that the 5 amp and 8 amp batteries are exactly the same size form and weight.

So naturally I use the 8’s.

However, yesterday I was using the Mafell cordless saw to rip a 3/4” pine board (using an appropriate blade) powered by an 8 amp Metabo battery that indicated a roughly 50% charge via two of the four leds lit. The saw went a couple feet and stalled. Twice, so I swapped in a fully charged 5 amp battery and the saw was productive.

Maybe you explain that Coen?

 

[Coen]

One thing that puzzles me is that the 5 amp and 8 amp batteries are exactly the same size form and weight.

Probably 5.5 and 8?

There is a 3000 mAh version of the Samsung 21700 cell (the INR21700-30T) that does slightly better under extreme discharge currents than the 4000 mAh (INR21700-40T) one that is used in the 4, 8 and 12 Ah packs. If you use two rows of the 3000 mAh cells you would get a pack that is nominally 108 Wh.
However, if you then program the BMS to not fully charge it you can put 99 Wh on the label (18V x 5.5 Ah) and stay under the TSA limit of 100 Wh.

Bosch has the same thing. Then the smart charger has issues with it not seeing the 5.5 Ah ever as full. Lool

However, yesterday I was using the Mafell cordless saw to rip a 3/4” pine board (using an appropriate blade) powered by an 8 amp Metabo battery that indicated a roughly 50% charge via two of the four leds lit. The saw went a couple feet and stalled. Twice, so I swapped in a fully charged 5 amp battery and the saw was productive.

Maybe you explain that Coen?

There is a low-voltage protection in the battery in the sense that if one cell pair gets too low it either cuts the connection completely or it tells the tool to stop draining it (differs by brand, generation, etc.). And if indeed they used the cells that perform better under extreme load the voltage sag of the 5.5 Ah pack will be less than the 8 Ah in same conditions. And when it's full vs half empty then there is no real competition.

When batteries degrade and their internal resistance increases, the voltage sag also becomes bigger. A worn out battery may present the same no-load voltage, but under load it will sag more.

By the way; it seems Metabo now also has a 2-row 10 Ah pack. I wonder if that is using the Samsung INR21700-50S cells. I have contemplated using those in rebuilds of Bosch 21700-based 4 Ah packs but didn't because of the already tight press-fit and the slightly larger listed dimensions of the 50S cell vs the 40T.

 

[Michael Kellough]

Thanks Coen! I like to read about tech stuff and your writing on the subject of batteries is better than what I find elsewhere.

You’re right, the 5.5 amp batteries are engraved to say 99wh. I