Li-Ion multi-cell UPS?


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Li-Ion multi-cell UPS?

Postby bits_for_brains » Tue, 20 Jan 2004 02:46:29 GMT

Q:  Do off the shelf standalone incircuit charge/discharge controllers
exist for multicell LiIon packs?

I have a dated laptop (Compaq M300) for which replacement battery are
hard to find or $$$.
The cheap solution seems to be a d-i-y external battery pack which
connects to the primary DC input of the laptop.   (Yes I do lose the
power management features, but interconnections are simpler)

Two battery technologies are in consideration.   
The NiMh which has a better shelf life but has a higher size/weight
due to the required 10-14 cells.
The LiIon required specialized smart charge/discharge controller plus
extra safety monitoring, but the 4 required cells offers a distinct
size advantage.

Before I persue building my own LiIon incircuit charger (based on TI
family chips), I would like to know if there are any "off the shelf"
solutions for the battery monitoring.   To me, it looks like a
homebuilt solution (effectively an UPS) would occupy the footprint of
my AC adapter.
The AC adapter (18V out) connects to the battery pack which connects
to the laptop primary input.

Re: Li-Ion multi-cell UPS?

Postby H. Dziardziel » Tue, 20 Jan 2004 11:50:13 GMT

On 18 Jan 2004 09:46:29 -0800,  XXXX@XXXXX.COM  (Help)

Some laptop models e.g. some IBMs, have SMB stand-alone chargers.
But  anything would cost more totally since they are matched to
pack types.  Not sure if that is what you mean?

A somewhat better shelf life but much higher self discharge.  Good
choice for heavy (no pun intended) use..

The Li-ion cells (which are not sold to consumers anyway for
safety reasons) cost,and the electronics needed along with the
real safety considerations needed during the building and checking
makes the far simpler, albeit bulkier, safe NIMH the route to take
-- my advise.

New MiNh have energy densities nearly equal to Li-ion (e.g. Sanyo)
so the bulk may not be all that much more and partially offset by
the simpler charging circuit design.   A set of 20 readily
available consumer AAs provide >4000mAh@12v, are pretty compact
and easy to charge with off the shelf chargers.   And simple to
fix.  Just keep possible reverse voltage during discharging in

Similar Threads:

1.Li-ion 14.40V 4000mAh Equivalent to IBM ThinkPad R32, R40 Series Laptop Battery

2.Li-Ion Batteries loose 20% of Capacity Per Year If Kept @ Full Charge

Barry Watzman < XXXX@XXXXX.COM > wrote:

>What can kill a battery is a 
>combination of overcharging and heat (either from within the battery or 
>from external sources).  Some laptops are well designed in these 
>regards, others, however are not.

>(I'd say that most are not, based on experience). 

Rather a poor supposition don't you think? The number of laptops that
are poorly designed in your "experience" must be minuscule compared to
the thousands of other models in service.

But if you disagree I'll just add that in my 'experience' I've never
had to replace a laptop battery, and I usually leave them plugged in
all the time. When I want to pick up and go, I want to pick up and go,
and not have to hunt up a battery that I probably forgot to charge
recently... ;)

3.Li-Ion Batteries loose 20% of Capacity Per Year If Kept @ Full Charge

4.Li-Ion Battery Care

Barry Watzman, M.I.5 others and myself have talked about Li-Ion 
battery care in the past. Although I also fly RC electric helicopters 
and airplanes. Some of them also use Li-Ion batteries. And RC electric 
people seem to know more about batteries more than anybody else I know. 
As they build their own chargers, etc. And one thing is clear as a bell 
for me lately about Li-Ion batteries.


What seems really clear is when you are using them on battery power, 
they might get warm. That is okay it seems. So use your laptop on 
battery power and not too worry. Although the worst thing you can do is 
to use your laptop on battery power and then charge it with AC power 
right afterwards. Let the battery cool down for 10 to 15 minutes first 
(or pull it out during this time to cool down).

Those that doesn't wait will find their RC Li-Ion batteries will go down 
really fast, as the capacity drops off drastically. Even with a brand 
new Li-Ion battery. They seem to drop 25% or more from the get go if you 
charge them while they are warm (or hot).

I hope this information has helped those that want to get 10 or more 
years out of their Li-Ion batteries. And it seems best if you recharge 
sitting Li-Ion batteries about once every 6 months. Well you can go 
longer, but every 6 months seems pretty safe.

email: change kom to com 

5.Min Li-Ion Volltage and Character Map - [ Alt Gr key]

M.I.5wrote on Fri, 14 Nov 2008 07:51:58 -0000:

>> ... and if you only need them occasionally, cheaper still is
>> file://%SystemRoot%\system32\charmap.exe

Yes, I have been using Character Map since '93 (Windows v3.1) when there 
is no easier or other way. It gets the job done but very annoying if you 
need it say more than a few times a week. It also seems there was a 
Windows version that it was missing from. Maybe I'm mistaken or it could 
have been an OEM version which sometimes doesn't include everything.

Say does this look like a degree symbol to you ? Geez yesterday it 
looked like a square box on this 7 inch screen. Now it looks round like 
it is supposed to be today.

I am trying to get used to this US International Keyboard with the extra 
characters. Now I have to figure out why some keys doesn't type like " 
when I hit them. Is this what is called dead keys? lol

Say M.I.5 what did you say the bare minimum voltage per cell for 
Li-Ion should be (2.8 wasn't it)? This EeePC range is from 3.02 to 4.18 
volts per cell. Some claims that the EeePC battery is more on the 
outside of the case and it doesn't pickup the heat from the laptop like 
most brands. So you can leave them in and they don't degrade from the 
heat like most. I have 5 EeePC batteries and I leave one in all of the 
time. So I guess time will tell if it is true. :D

Of course there is the damage of the laptop always tapping it off to 
full on a daily bases. My Palm IIIc does that too. Although the Palm 
IIIc creates no heat and I get 5 years out of an Li-Ion battery here. I 
am on my 2nd one and it is 3 years old now and still going strong. I 
worry a bit with it, as it is a cheapo from China and they didn't add 
any of the safety circuits with the battery. I've been meaning to add 
the ones from the old original battery. :P

Asus EEE PC 8GB 1GB SoDIMM Adata 16GB
Windows XP SP2 and Xandros Linux

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7. Li-Ion Battery Strategies (Thinkpad)

8. NiMH -vs- Li-Ion

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