Battery Selection

[OldGuy]

I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

What is the best battery to use with this other than a full size car
battery.

I have been looking at closed cell 12v 18AHr batteris as a possible
choice. not sure is these are deep discharge.
Or maybe a motorcycle battery.

Suggestions please.

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[Jasen Betts]

On 2015-01-30, OldGuy <OldGuy@spamnot.com> wrote:

I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

What is the best battery to use with this other than a full size car
battery.

A spill resistant 12V lead-acid battery (eg AGM or gel-electrolyte
construnction) would be compatible with that charger, and more
conveniently portable.

there's probably a compatible lithium battery too, but I don't know
the detaqils of that laptop charger or which lithum battery to
reccomend, but, it would likely be more portable than the equivalently
capable lead-acid battery..

I have been looking at closed cell 12v 18AHr batteris as a possible
choice. not sure is these are deep discharge.

check with the maker, some are designed for portable devices others
for backup power.

> Or maybe a motorcycle battery.

A motorcycle battery is not spill resistant, not designed for deep
discharge either. sulphuric acid fumes/seepage from that battery will
destroy cotton etc.

--
umop apisdn

 

OldGuy <OldGuy@spamnot.com> wrote:

I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

One thing you can experiment with at home is to turn up the power-saving
settings in the OS, get rid of programs that run in the background, etc,
to maximize the runtime on the laptop's internal battery. If you don't
need WiFi, and you have the "WiFi off" switch on the outside of the
laptop, use it. This will help reduce the size of the external battery
you need.

> I have a Enercel AC/12VDC to laptop power block cord.

Do you know what the DC output capacity of either the Enercel or the
original adapter that came with the laptop is? This can help you decide
how big of an external battery you need.

A lot of recent Dell laptops come with 60 W power adapters; some of the
"big" ones come with 90 W adapters. The laptop doesn't need this much
power all the time, unless you are doing something compute intensive,
like rendering HD video. I haven't measured but I would guess that a
modern-ish laptop would "idle" in the 15 to 20 W range (screen backlight
on, HDD spinning), before power saving features kicked in. This is
around 1.8 A at 12 V, after allowing for a little loss in the adapter.

What is the best battery to use with this other than a full size car
battery.

A "gel cell" or AGM battery, with whatever capacity you need to meet
your run time requirements. This can range from the ones that go in
an alarm system or small UPS (5 to 12 Ah or so) all the way up to ones
that are the same size as a car battery.

I have been looking at closed cell 12v 18AHr batteris as a possible
choice.

Keep in mind that the amp-hour rating is usually over a period of 20
hours. That 18 amp-hour battery will give you 0.9 amps continuously for
20 hours. It's not quite linear; if you take 1.8 amps, you'll get a
little bit less than 10 hours, and if you take 3.6 amps, you'll get
rather less than 5 hours.

> not sure is these are deep discharge.

They are.

> Or maybe a motorcycle battery.

No. These will be designed for starting (short bursts of very high
current, then immediate recharge) rather than deep-cycle use (lower
current but over a long period of time).

Other advice...

Charge the laptop's internal battery all the way at home before setting
forth. That way, all the juice from the external battery goes to
running the laptop, and not to charging its internal battery. This
also gives you some margin if you manage to run down the external
battery.

Use a fuse between the external battery and the input to the Enercel
charger.

Depending on how much battery capacity you need, one of the "jump
start" boxes might do what you want. These have a battery packaged up
with jumper cables; if you look around you can find one with a
cigarette lighter socket already on it. It will also come with a (not
very good) charger for use at home. The trouble here is that these
tend not to list the amp-hour capacity of the battery; they give some
wildly inflated claim about how many cranking amps it can deliver. You
can kind of tell by weight, but the only way to know for sure is to take
the thing apart and look.

Think about how you will charge the external battery when you get home.
Connecting it to a car while you drive around isn't actually a horrible
idea; the car's electrical system is *designed* to charge a lead-acid
battery, although it may not get a sealed battery to 100% charge. A
"dumb" high-current car battery charger is probably not a good idea; its
voltage output will be too high for the sealed battery. (High current
means more than about 20% of the amp-hour rating; for an 18 amp-hour
battery, that's more than 3.6 amps.) A "smart" and lower-current car
battery charger can work OK. The deluxe way is to get a charger
specifically made for sealed batteries.

Charge the external battery as soon as you can once power is available
again. If it has to sit for a day or two before getting recharged, OK.
Even a week isn't too bad, but a couple of months is a bad idea.

If you're going to do this a lot, and your laptop has a hard drive, it
may pay to replace it with a solid-state drive. They aren't cheap, but
their power consumption is lower.

If it's something you can do on a smartphone or tablet instead, you
might consider that. Full-size Bluetooth keyboards are available if you
can't deal with the tiny on-screen keys on a phone.

Matt Roberds

 

[David Eather]

On Sat, 31 Jan 2015 07:16:27 +1000, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2015-01-30, OldGuy <OldGuy@spamnot.com> wrote:
I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

What is the best battery to use with this other than a full size car
battery.

A spill resistant 12V lead-acid battery (eg AGM or gel-electrolyte
construnction) would be compatible with that charger, and more
conveniently portable.

there's probably a compatible lithium battery too, but I don't know
the detaqils of that laptop charger or which lithum battery to
reccomend, but, it would likely be more portable than the equivalently
capable lead-acid battery..

I have been looking at closed cell 12v 18AHr batteris as a possible
choice. not sure is these are deep discharge.

check with the maker, some are designed for portable devices others
for backup power.

Or maybe a motorcycle battery.

A motorcycle battery is not spill resistant, not designed for deep
discharge either. sulphuric acid fumes/seepage from that battery will
destroy cotton etc.

The SLA cells are designed to deliver power and is a much better choice
than a car battery which is designed to deliver cranking current. You
might also consider a honking great string of NiMh cells in battery
holders. This might have an advantage in that you could reduce the amount
of them you have to lug around if you only need to work for an hour or so.

 

On Fri, 30 Jan 2015 10:41:56 -0800, OldGuy <OldGuy@spamnot.com> wrote:

I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

What is the best battery to use with this other than a full size car
battery.

I have been looking at closed cell 12v 18AHr batteris as a possible
choice. not sure is these are deep discharge.
Or maybe a motorcycle battery.

Suggestions please.

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

If you have the proper charger then the best would be lithium ion
batteries. They pack the most power, size and weight wise, of any
commonly available consumer battery. Maybe you could get some of the
batteries that power your laptop and that way you would have the
proper charger available. Power your laptop with the power block while
changing batteries, that way you won't lose very much power in the
power block since it will only be used during battery swaps. So use
one small battery to supply power to the power block because it is
only used briefly. If you can't swap batteries for whatever reason
then find a lithium ion battery to power the power block. They are now
available as substitutes for motorcycle batteries. I know a few guys
who have ditched their old lead acid motorcycle batteries for lithium
ones because they are lighter. As if they could really tell the
difference when riding.
Eric

 

[whit3rd]

On Friday, January 30, 2015 at 10:42:17 AM UTC-8, OldGuy wrote:

I need to run my laptop for many hours and in a mobile state; i.e. no
AC Power available not car available.

I have a Enercel AC/12VDC to laptop power block cord.

First thing, consider the energy-save options on your laptop. Finding
a power-stingy model or making power-management settings properly
can give you a big boost. You might even consider buying a longer-battery-life
laptop or tablet, it'd be easier than lugging lead/acid outboard batteries.

Second, many laptops can hotswap batteries (and the energy in an expensive
Li-ion laptop battery is greater than an equivalent weight of lead/acid motorcycle
battery). A vest with four pockets, and a laptop with 5 hour battery life,
gives you better than 24 hours before you need recharging. No dangling cables on
the laptop, this way.

If you do need to lug batteries, find a marine supplier and get a battery box
with sling (the box will protect the battery from bumps and the sling will give
you a handle). Marine 'deep-cycle' batteries are pretty rugged, but
if it might tip over, you'll be better off with sealed lead-acid.