external battery??

Though I don't know that model, I'm sure the 8890 pulls too much power for that. We're working on an external battery option with no ETA. We're confident it will work out though, it's just how long testing will take to make sure a safe product is released.

I believe the 8890 and 5680 top out at 130 Watts.

Yep, and the 8886 & 8887 are 120W (I think the 5660 is, too). So this thing (referenced above) probably won't power those, either.

-myrkat

Yeah, 130watts on a 95watthour battery is about 45minutes of juice.

Whilst wattage is important it is Amperage and Volts.

Power (watts) = V (volts) * I (amps)

The voltage is fixed by the electrical specifications of the internal power converter (the 8890 is set to 20V DC input) and the current (I measured in amps) depends on the amount of work (or power) that the laptop is doing at any given moment. The current draw will also be affected by how much the battery is drawing in order to recharge itself (note: these external batteries work better if you remove your internal battery btw).

The power adaptor for the 8890 provides 20V DC output up to 6 amps.

If the external battery can deliver enough amps at 20V then you are set (I could not find any specs on this) but then you have the issue of finding a suitable plug that is compatible with the ones that Sager use.

Sure, that's why the battery is rated in watt hours, 1 watt=1 volt * 1 amp.

but watthours does not give you the full story because:
1000V @ 1mA still gives you 1 watthour.

It is more important to know the voltage required (hence why the product mentions you have to be very careful about which adaptor you choose - it can't just "look" like the right one - the little plug in connectors actually alter the output voltage).

Once the voltage is set then you can estimate current draws and thus wire guages, connector types, insulation. Wattage is only a derived figure.

Yes batteries are rated in watthours so you can compare power densities (ie oranges to oranges) for any given weight/size of battery, but that does not indicate their current or voltage ratings. Battery pack output voltages are a function of the number of piles (ie chemical cells) and the chemistry involved (some chemistries produce lower voltages due to the electrical characteristics of the anode/cathode/ion solution). So when manufacturers specify their batteries they will normally go for voltages that provide a good power density vs weight tradeoff.

There is a bit of confusion here.

Firstly the spec mentioned is amp-hours. It does not tell you much at all. For example can the battery produce 18amps for 30 minutes or 36 amps for 15 minutes? Current draw depends on the connectors and other factors inside the battery itself.

Unfortunately most retail sites will not give you proper/useful information wrt battery packs because most of them are clueless as well.

What you need in selecting a battery is:
1. What is its output voltage - the 8890 needs 20V DC
2. What is its rated current - the 8890 power adaptor can produce 6 Amps continuously.

Other figures such as Amp-hours, Watts etc are useless figures unless you are just comparing battery power density (ie. how long a given battery will last if I draw "X" amps at "Y" volts).

Edit: To give you an idea of how clueless these places are, this comes from their FAQ:
"NiCad batteries are rechargeable, whereas Lithium and alkaline batteries are NOT". Well they are sort of right. When you are dealing with electrical systems, sort of right does not count. I can imagine Shockley at Bell Labs going "well it sort of works" when they were testing the first transistor - not. I wish people would gain a more rigourous understanding of things... but maybe that is why they employ me...

Guys.. as has been said ALOT before, there are NO protable external batteries that are compatible with the currect sagers. They are being made, but right now, none will do it...

Divine_madcat is right (hey we agree there). If you take a look at the specs on the AC adaptor that powers that unit you will notice that it is only rated for 3.1A. If that is what is recharging the battery, it would have a problem even keeping up with the 8890's.

"M'am could you switch off your car, the bowser can't pump gas that fast..."

Aw, come on.. we cant disagree that much..... do we??

Okay, kids, gather round.

A battery pack is rated three ways and it needs the appropriate connection to fit your computer. The connection is probably the simplest to deal with, its a common connector, so its just a matter of figuring out what wires go to what pins. There are schematics available so that can be figured out as well. Not a big deal. Actually, a bit of checking with a multimeter would do as well, but the schematics would help eliminate some of the options.

So we go to how to determine if the pack has the goods. The SAGERs currently are using an adaptor that puts out 6 amp at 20 volts, that's 120 watts. It can do it for ever, well, as long as you pay the bill. So anything that can deliver at least 20 volts and 6 amps will do. If it can deliver a higher amperage, not a problem. Perhaps a tad less will do, but that's iffy. If anything, your battery would probably charge slower than it does now. Operating power for these buggers is probably around 90 to 100 watts.

The watt hours or amp hours are sort of similar measurements. The watt hours is the more correct rating, what it means is how many watts the battery can deliver for how long. So an 100 watt hour battery would produce 100 watts for one hour or 1 watt for 100 hours or 10 watts for 10 hours. But when you add in the wattage rating for the battery, ie - volts time amps, in the case of the SAGER, 120 watts, a 100 watt hour battery would deliver its 120 watts for 0.833 hours.

Amp hours short circuit the rating, so to speak, they take into account the voltage the battery delivers its power at, in this case, 20 volts, so if you have a battery rated at 8 amphours, it means it will deliver 8 amps at the required voltage for one hour.

The battery in my 8886, which I believe is the same as the 8887, is rated at 6000 mAH with 14.6 hours. That means it puts out 87.6 watt hours. I think the 8890 is 6600 mAH and the voltage is the same so its good for 96 watt hours.

You will notice that while the charger is rated for 120 watt hours, the batteries are only 87 and 96 watt hours. That's because the charger is also charging the battery in addition to running the machine.

I don't know if this means you can could use a battery pack that puts out 14.6 volts, though if you have a plug that matched the battery itself and you removed the battery and plugged in there, you definitely could get by with 14.6 volts as long as it can put out 6 amps or so.

So, to recap, you are going to have to have something that puts out 20 volts. Its going to need to be able push 6 amps. You can figure of about an hour per 100 watt hours of listed capacity when you are cranking, give or take. If you are just cruising, surfing, doing email, you would probably get 1-1/2 to 2 times that. With 140 watt hours (again, assuming its putting out 20 volts) you should get 1.4 hours of cranking and 2.1 to 2.8 hours of cruising. If your battery is already charged, you won't be drawing for that, so maybe more time. The battery charging looks like it takes about 30 to 35 watts or about a quarter of the power the AC adaptor puts out.

One of the reasons for the 20 volts on the charger vs the 14.6 volts for the battery is it takes a higher voltage to drive the juice into the battery.

Hope this little primer helps out.

Well explained Marquis.
There is one thing you did overlook, is that not all of the 6 amps that the power adaptor puts out is used to run the laptop per se.

Once DC (20V at up to 6 amps of current) arrives inside the laptop there is a power supply (of sorts) which has to distribute that power. Some of it goes to run the electronics, diskdrives, LCD backlight, etc etc., the other goes to recharge the battery IF IT REQUIRES it.

So what we need to find out is how much power (in watts) the laptop itself uses without having to recharge the batteries. It will be a fraction of the total 120W (20V @ 6A) that the power adaptor can put out. That will then give you the current (amps) required to power just the laptop (remember the voltage is fixed at 20V).

If those power pads can deliver the required amps fast enough (and that is the key question) then they will work with our laptops. If they have current limiters or in-line fuses on the DC side that are short of our laptop's requirements they will not work. Worse still they will blow fuses or shut down to protect themselves (oh no, not the Sager, not the Sager. Arrrggghhh ).

I don't think anyone is willing to volunteer. PLEASE KEEP AWAY FROM DOING THIS. Although the volts are low the currents invovled are reasonably dangerous.

Firstly it would require a high power mulitmeter (most only go up to 1A on the current setting - you would need one capable of measuring at least to 10A). Next it would involve patching into the DC power lead (current measurements are "in circuit" unlike voltage measurement which are across two points).

Personally I think it would be easier to ask Sager themselves as they would have the design specs on the laptop's internal power distribution circuit.