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External Battery Pack Option

Wayne or anyone,

Hi,

I finally bought the Introcircuit 26000mah. I have tested its battery life. I couldn't fully charge my SP2 twice.

I can fully charge my SP2 once from 5-100%. Then, another charge from 5-75% and the battery is dead.

So it gives me total around 175%, is it normal?
Is it suppose to provide alittle more than two fully charges? I only can have one fully charge and 75% for second charge.

Is my battery defected? Anyone who has this Introcircuit battery. Do you have better charging result or it's the same?

Thank you so much,
 
I can fully charge my SP2 once from 5-100%. Then, another charge from 5-75% and the battery is dead.

So it gives me total around 175%, is it normal?
Is it suppose to provide alittle more than two fully charges? I only can have one fully charge and 75% for second charge.
,

That is probably normal. I've never done what you are doing. I keep my Surface close to 100% and simple run it from the exterrnal battery. I've never run either one totally flat. (that just shortens their life)
But the Surface Pro is roughly 42 watt hours. The Intocircuit is close to 100 watt hours (26A x 3.8V). BUT, you have to figure in the conversion efficiencies. (you need to convert UP from about 3.8 to 12 volts. Then convert DOWN from 12 volts to 7.6 or so volts) Figure 90% efficiency per step, or about 81% total. So the 100 watt hours is now close to 81 watt hours. Now you are just under two full charges. My 90% efficiency is a wild guess and it could be less. Charging batteries is also far from 100% efficient.
In the end, basically it is very close to what you are seeing.
So I think you are close to the max.
 
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That is probably normal. I've never done what you are doing. I keep my Surface close to 100% and simple run it from the battery. I've never run either one totally flat. (that just shortens their life)
But the Surface Pro is roughly 42 watt hours. The Intocircuit is close to 100 watt hours (26A x 3.8V). BUT, you have to figure in the conversion efficiencies. (you need to convert UP from about 3.8 to 12 volts. Then convert DOWN from 12 volts to 7.6 or so volts) Figure 90% efficiency per step, or about 81% total. So the 100 watt hours is now close to 81 watt hours. Now you are just under two full charges. My 90% efficiency is a wild guess and it could be less. Charging batteries is also far from 100% efficient.
In the end, basically it is very close to what you are seeing.
So I think you are close to the max.

Wayne,
I reallay appreciate your info. Thank you so much. I was worry about getting the defected battery while it is over a $100. I would exchange with the seller while it is still under warranty. I know alot of people getting Introcircuit battery withthe cable but noone share the charing result on this forum. I heard some people are getting a defected battery and needed to exchange. That's why I am asking. Thank you,
 
Wayne,

May I ask what is the best way to prevent shortens the battery life on SP2? You suggested not to charge in full 100% and use it on battery instead with wall charger?? Then, before it reach to 5% charge it again to around 95%? Is it what you are doing?
I thought people are suggested to run it totally flat at least once a month. Is it truth?

Thanks,
 
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Wayne,

May I ask what is the best way to prevent shortens the battery life on SP2? You suggested not to charge in full 100% and use it on battery instead with wall charger?? Then, before it reach to 5% charge it again to around 95%? Is it what you are doing?
I thought people are suggested to run it totally flat at least once a month. Is it truth?

Thanks,

I may have sounded confusing when I said 'run from the battery'. I mean, I keep my Surface Pro close to 100%, and run from the external battery (or of course the normal AC adapter).
Cycling the battery, up and down, shortens the life. So I just keep it at 100% as much as I can. Theory goes that you should keep it close to 45%, but there is no way practical to do that.
Generally, don't cycle the battery much if you can help it. Charging and discharging the battery also generates heat. Heat is very bad for the battery. Just leaving it at 100% reduces the heat.
BUT, if you feel that the battery meter isn't accurate, THEN you may want to do a full cycle. That can re-calibrate the battery gauge. Some people recommend a full cycle monthly to keep the system calibrated. I only do it when I feel it is needed, which is almost never.

In the end, I don't worry about it much. I bought it for the portability, and I use it as needed. If that empties the battery, so be it.
 
I'm feeling appreciative of my iPhone/iPad now -- while they have proprietary charging plugs, at least the other end is USB. Now that I have a SP2, 'proprietary' is quite literal. I have found a source for a Surface cable at a reasonable $12: USD$12.00 - Wall Charger Cable for Microsoft Surface RT Surface Pro - lunashops online shop

If I were to get that cable, what battery pack would work with it? I'm not looking for tons of capacity as I don't want to lug a huge battery back around -- possible a 50% to 100% charge of my SP2?
 
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The IntoCircuit 26000MaHr pack is about the only one I would recommend.
I'm certain there are other suitable alternatives, but you would need to do your own experimenting. You might actually be able to get a sealed lead acid gel battery from WallyWorld for $20 that does the job well. But it would be heavy and unregulated, so it would be an experiment.

BTW, That cable is for an RT, not a Pro. The Pro needs about twice the current of an RT. I tried a cheap RT cable myself, and it eventually melted.

Edit. Misread that. It does state it works with the Pro.
 
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I'm feeling appreciative of my iPhone/iPad now -- while they have proprietary charging plugs, at least the other end is USB. Now that I have a SP2, 'proprietary' is quite literal.
Because of the power needed (the Surface Pro charger is rated at 12V 3.6A) you would need a USB port capable of supplying over 8A, and even USB 3.0 is nowhere near to that.
 
Thanks -- guess I'll wait it out until something approved is available -- it isn't really an issue at this point, more of a just-in-case scenario...
 
BTW, That cable is for an RT, not a Pro. The Pro needs about twice the current of an RT. I tried a cheap RT cable myself, and it eventually melted.

The description clearly states "Surface Pro" at the end.

I bought the Lunashops cable on eBay to use with Amazon.com: Anker® Astro Pro2 20000mAh Ultra-High Capacity Multi-Voltage (5V 12V 16V 19V) External Battery Backup Charger Power Pack for Tablets, Netbooks, Notebooks, Laptops and Smart Phones -- Compatible with HP, Dell, Acer, Asus, Toshiba Notebooks which I already had. I didn't test it any further than plugging it in and verifying that the Surface Pro started charging. I bought the cable to use on an international flight I am taking next week. I don't need the extra battery most of the time, but it will come in handy on long flights and possibly other random occasions.
 
May I ask what is the best way to prevent shortens the battery life on SP2? You suggested not to charge in full 100% and use it on battery instead with wall charger??
I may have sounded confusing when I said 'run from the battery'. I mean, I keep my Surface Pro close to 100%, and run from the external battery (or of course the normal AC adapter).
Cycling the battery, up and down, shortens the life. So I just keep it at 100% as much as I can. Theory goes that you should keep it close to 45%, but there is no way practical to do that.
Generally, don't cycle the battery much if you can help it. Charging and discharging the battery also generates heat. Heat is very bad for the battery. Just leaving it at 100% reduces the heat.

Just chiming in on the matter of battery life preservation in response to cedric. I know you acknowledged that 45% would be ideal but I think keeping it at 100% is also fairly damaging to Li-Ion batteries. If your usage behavior supports it, I think it would easier on the battery to cycle from 40% to 80% constantly rather than to be kept at 100%. As a case in point if you look at GM and the Chevy Volt, they discharge the battery pack to only 30% and charge it to only 85% - effectively utilizing only 55% of the battery capacity in order to preserve the battery life as much as possible. GM would be highly motivated to have a further electric range and surely they've done some pretty extensive research on their options, so my rule of thumb is to try to keep the battery below 85%. Granted keeping a 100% charge isn't an option in the case of the Volt...

Anecdotally, I have a Sony laptop that has a "battery care" function that can be set to keep the battery at 50% or 80% charge and after 5 years of daily plugged in use (as my work PC) the battery is still nearly as good as new. On the other hand a previous laptop battery that would charge to 100% lasted only about 18 months before it was totally useless. And my iPhone at about 2 years old and 49 days usage (by the usage stats) now has about 2.5 times the battery capacity of my wife's phone of the same age, which has only about 1/4 the amount of usage time on it; obviously she's less careful than me about her charging habits.

I do concur that running it low is far more damaging than charging full. Only if I really need to will I allow a battery to discharge below 20%, and only in an emergency below 10%. I have the Surface set to warn at 25%, sleep at 20%, and hibernate at 16%... No question that battery life is being taken every time it drops below 10%... But for "ideal" usage, I think the Chevy volt paradigm of keeping between 30% and 85% is probably the way to go...
 
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