Re: Way OT, but maybe interesting: Li-ion battery observations and questions


Pete Lancashire
 

I know this thread is getting pretty long here but I'll also toss in my
vote for Makita. They're one of the few independent companies that still
make design and manufacture their own tools and the one time I had problems
with a model that had a brushless motor Makita of America sent me a
replacement with an RMA tag and told me to return the defective one one at
my leisure.

On Mon, May 7, 2018, 12:19 PM stefan_trethan <stefan_trethan@...> wrote:

I just bought a Makita DUC353 (XCU03 in the US) and I'm also happy with it.
Compared to other battery saws it uses a different concept, it runs at
high chain speed (similar to a gas powered saw) but has less torque.
With the narrow chain this works out fine as long as it is sharp, but
you can bog it down if you push hard.

It uses two 18V batteries, I use 5Ah ones (different ones are
available), so 180Wh which makes it 10 minutes runtime at 1kW (full
power). This seems short, but you don't always use full power and my
Stihl saws will do maybe 15-20 minutes a tank at full throttle so not
such a big difference.

Don't get me wrong, the Stihl saws work great. They start easily and
plenty of power, no issues at all. But for a few small cuts it is a
hassle to get one ready, get your hearing protection, it's still
noisy, smelly, and I really don't like loud motor noises and the smell
of petrol (other men may differ).

I wouldn't expect to use only the battery saw for a large tree, but
for small stuff, especially intermittent work, it is ideal because you
don't have to pull the cord all the time, you just push the buttons
and it cuts. Also if you have to climb something it's an advantage for
sure. I think it is somewhat more dangerous than a gas saw because it
is so easy to use, but I bet it'll cut you just as bad, so don't get
careless.

I already have _a lot_ of Makita 18V tools so I didn't have to buy the
batteries or charger.
Bosch is better quality in the 3 cell (12V) range, but the Makita
concept using one or two 18V batteries is superior for high powered
tools. 500W with one battery and 1kW with two, you can do some real
work with that.

I would say that brushless motors made a similar difference as lithium
batteries over Nickel.
Combine the two and you don't really need a cord for most things.

I really want to make a battery powered soldering iron with a JBC
handle and a 18V Makita battery, anyone up for a challenge?

ST

On Mon, May 7, 2018 at 8:18 PM, Ed Breya via Groups.Io
<edbreya=yahoo.com@groups.io> wrote:
I've been up at the farm this weekend, and decided to take down a
medium-sized, ratty old dying tree in the vineyard. Last year I took a
chance and bought one of these 40V Li-ion battery powered small (14")
chainsaws to try out on small, sporadic trim work. I've used successfully
it a few times on fallen branches and small stuff, but was dubious about it
holding up on "real" work.

I've had many gas saws and weeders etc over the years, and invariably
they are out of commission after a couple of seasons and over-wintering
storage, so need to be cleaned up and worked over or fixed to get going
again. The thing I've noticed recently is that the rubbery material primer
pump bulbs deteriorate rapidly and crack, so you can't prime the carburetor
to get started after storage. It seems that a lot of plastic and rubber
materials nowadays that should be permanent, are almost biodegradable and
crap out way too soon.

Of course, my last previously working gas saw has its primer bulb shot,
so it was time to try the new battery one, and give it a real workout. I
don't know what kind of tree this is - it's more like a giant bush, with a
number of large trunks ranging from maybe 4-10" diameter at the base,
reaching about 25' high. The wood is fairly hard and dense, so the fatter
sections had to be chunked out from firewood-sized to a few feet long for
lifting. The branches are gnarly and viney, and all intertwined, including
deadwood and fresh shoots, so it took a lot of cuts just to separate and
trim down to manageable pieces for moving and piling up.

Sorry for the highly detailed description, but I just wanted to
emphasize that although this was nowhere near the largest tree I've fallen,
it was perhaps the most tedious for its size, in terms of getting it down
on the ground and manageable for moving out the debris. Anyway, the saw
worked great! I had to do perhaps 100 large cuts of 2" and up, and 200
small ones, over about an hour and a half. It runs much slower, but
"torquier" than a gas saw, so cuts slower, but just keeps on going and
going. I figured I would quit when the battery ran out, but I ran out
first. I got it all down and now have a huge pile of debris. The saw
apparently still had plenty of juice!

Now for the technical part. Many modern battery packs have a "gas gauge"
indicator built in, like a few LEDs that light up when you press a button.
When I was done with cutting, I pulled the battery, and was shocked that it
read 3 out of 4 bars, so to speak - I had only used up a small fraction of
the capacity, if this was correct. So now I'm wondering just how accurate
and/or linear this indication is. I assume that the Li-ion charge-discharge
management ICs nowadays have plenty of smarts built in, including capacity
level.

The question is, is it a measured and calculated indication of actual
remaining joulage, or just a rough estimate based on the battery
voltage/discharge curve? This pack is rated 40V, 2.5 A-h, so 100 W-h. I'm
amazed at how much work I got done with this much available juice, let
alone a fraction of it. So, does anyone know much about the character of
these battery management ICs, especially the indicator part?

In conclusion, I'm very impressed with today's Li-ion technology. I will
be getting at least one more of these saws and some spare batteries. They
will be my go-to saws from now on, although I'll still fix and keep the old
gassers for seriously bigger stuff.

Ed




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