Charging with external battery - possible?
 

Hi,

I`m going on a 2 week bike-travel in summer and want to use my N810 for navigation. The Problem is, I won`t be able to charge it so I need some kind of external power.

My charger has an output-Voltage of 6,15V (without the device connected to it) - So I asked myself if it is possible to charge the n810 (and run it directly) with an external 6V Battery (like this: http://www.online-batterien.de/shop/...erie6Vlose.jpg), just connected to a 2mm charging-Plug - without any electric circuit between.

What do you think? Could I demage it by doing that?

Re: Charging with external battery - possible?
 

Actually, you need a regulated 5v supply to plug in to your power jack. A battery may start out at 6v, but it drops in voltage as you use it. What I suggest is using a 12v battery with a simple circuit that gives you a regulated 5v output. You can buy them in the form of an adaptor that plugs into your 12v power outlet of your car which has a dc output of 5v rated at a current of 1amp. I would buy a lead acid (rechargable) battery rated at 17 ampere hours.

Re: Charging with external battery - possible?
 

Here's a novel answer to biking holidays:

http://www.voltaicsystems.com/
( solar powered backpacks with batteries built in, designed to charge mobiles.)

Don't have one and they're a bit expensive but I'm sure there will be lots of cloned products in no time at all.

Re: Charging with external battery - possible?
 

The 2mm charging spec has a current and voltage window of acceptable electrical supplies. At 6V the maximum current is somewhere around 1000mA. That 6V battery you linked probably consists of 4 cylindrical D or F size alkaline or heavy-duty batteries. It's capable of providing far more than that. So no, I wouldn't use that.

If you get two of them you can get 12V out of them, and use a car charger. Those I've tested even work when supply voltage drops below 12V, the better ones are still working at 6V input, so it would extract most of the juice out of the alkaline/heavyduty based batteries too (when connected in series to start off at 12V).

Just a guess, but two of those non-alkaline batteries you posted could probably when combined with a reasonable efficient car charger power GPS+display use for 50 hours.

You might also be interested in devices such as the Tekkeon MP1550 which can charge your N810 from 4 AA batteries. Maybe 4-8 hours of power per set of 4 AA NIMH. Would be less with alkalines.

Re: Charging with external battery - possible?
 

First, thanks a lot for your answers.

The solar-stuff looks cool. But: too expensive and bad for cloudy days.

A lead acid battery with 12v and 17 Ah is too heavy (about 6kg). Even two of the 6v batteries I supposed and a car-charger are much - I`ve lot of other gabbage to transport. But if theres no other solution its a good idea! I even have a car charger here - but no Idea if it`s efficient... but I don`t think so... its a cheap 4€ part from ebay.

What if I use an 1A low drop regulator like this: http://www.national.com/ds/LM/LM2940.pdf, together with 2 capacitors as voltage regulator between the battery and the device? Then there are 5V and max. 1A Output - enough for charging?

Re: Charging with external battery - possible?
 

That voltage regulator will do the job. Yes, use the 5v output device. You still have to decide on a battery. Is it for just all-day use and can be charged at night? If so, you don't need the 17 Ah battery. Half of that will do.

Re: Charging with external battery - possible?
 

I use and always recommend the Tekkeon - TekCharge MP1550 for applications like that. Oddly enough though, if a DoubleA battery powered solution won't work for you, then try out one of the 18000mah Energizer battery packs. You'll get a crazy amount of recharges off of it, and it'll work well for when you have to be in the wild and still use your GPS.

Re: Charging with external battery - possible?
 

According to Nokia 2-mm DC Charging Interface Specification Nokia N810 can use different voltages. So yes - an external charger is possible. On the other hand this is not what you probably want. If you buy 2-3 cheap Chinese batteries you will have more energy than most external chargers can provide (because during the charging process most of the energy is lost in the air as temperature).

Re: Charging with external battery - possible?
 

Note that the spec has 5V as an unacceptable voltage. Though with luck inaccuracies in the regulator and inaccuracies in N810's voltage measurement add up and make it work anyway..

Re: Charging with external battery - possible?
 

From 4,65V to 5,2V "Special Chargers" are accepted...

I saw there are USB-Cables for charging like this one: http://www.amazon.de/gp/product/B000...pf_rd_i=301128

USB has 5V. I suppose this will work. Parts are ordered - I`ll try to build an external charger for with usb-port now. Into the box will be enough space for 4 AA batteries. Also there will be a possibility to connect an external battery like the big 6V mentioned in the first post. This will give me the additional possibility to charge my mobile phone and my Ipod with it.

The cheap chinese batteries are REALLY cheap, thats right. But some days I will need the 810 for more than 12 hours (GPS for Navigation but even more important: Tracking with maemo mapper). And if theres no possibility to charge for 3 days I allready need about 10 of them. And then a break with the duration of 10 charging-cycles (at night I want to sleep and not get up every hour). An external solution is just best for me. Even with bad efficiency.

Is there a possibility to run the 810 without the battery inside it, just with external power? I tried it with my charger, doesn`t work. Maybe it`s more efficient to run it directly with the external device than the way round the internal battery...

Re: Charging with external battery - possible?
 

I just use an external battery pack, the predecessor to this one:

http://www.amazon.com/GearPower-Port...8592231&sr=8-2

Instead of charging off a computer, I usually use a little AC USB charger, like this:

http://www.dealextreme.com/details.dx/sku.19242

Works great. Simple. Small to carry. On airplane trips, I leave the external battery connected; I don't know if that's more efficient or not.

Have a good trip!

Re: Charging with external battery - possible?
 

This device is very nice :D
http://europe.nokia.com/find-product...specifications

Re: Charging with external battery - possible?
 

I don't believe there is an external portable charger that will provide you 3 days work-time.

You don't have to use your N810 in order to charge your batteries - you can use a separate charger and charge them simultaneously - these chargers are also cheap. :)

Re: Charging with external battery - possible?
 

thats right... but If there are 4 one-way AA Batteries inside which can be changed it should work. Back in civilisation after 3 days I have to buy new ones... Not eco-friendly I know... But an acceptable solution for for exceptional circumstances.

I`ve never seen an external charger for a BP-4L battery. But you are right - http://cgi.ebay.de/Akku-Ladeger%E4t-...100312138004r5... Now the parts for my diy-project are ordered. Doesn`t matter... I surely will have fun building it :)

Another possibility could be this: http://nokiaport.de/index.php?mid=5&pid=akkuersatz - on this site is a circuit diagram for externaly powering Nokia devices without a battery inside. Do you think that it ist possible to use 3 AA reuseable AA batteries with 1,2V (maybe a bit more...) each - 3,6V together and this diagram but without the diodes D1 and D2? Or will the current be to high without the low drop regulator?

Re: Charging with external battery - possible?
 

There is no way 4 AA batteries could provide enough work time because most of the energy will be used to charge the battery inside the N810, so it will go in the air as temperature. For example the Nokia emergency charger (a link was given before in this theme) is 1500MAh (i.e. = the BP-4L) but provides only 3 hours work time (according to the official specifications). However, (see below)

I didn't know that such things exist. I can not tell anything about the diodes but if you manage to somehow use directly AA or other batteries with no battery inside N810 then I think you will have good work time because all energy will be used by N810.

Re: Charging with external battery - possible?
 

I just contacted the author of this article. He`s sure this works for every Nokia device. The 75k resistor makes the device think that there`s a Nokia battery inside. The 2 diodes are only neccessary if the input voltage is 5V - so that the output voltage is about 3,7V. I will try this, too...

Re: Charging with external battery - possible?
 

I've found that my MP1550 doesn't do a very good job of charging my n810, as with any other USB based charging device.

Re: Charging with external battery - possible?
 

notnarb, you need a decent set of rechargeable batteries in it. If you use off the shelf AA's you will only get about a 50% charge before the MP1550 dies. And it's not the charger's fault. Normal, generic AA's just don't have the umph to do the job. It's why I switched to using 2500mah NiMH batteries in mine. One set of those is enough to charge the NIT from dead to 100%. And if you look at the numbers, 2500mah at 1.2 volts is about right to achieve that.

1.2v*4 = 4.8v
2500mah*2 = 5000mah / 2.5 = 2000.

The NIT battery is 1700mah. If you remove 300mah for overhead, that's just about spot on to completely recharge a NIT from dead. 2.5 is the average power to charge ratio on most batteries. It varies depending on battery type (like Lithium Ion I believe takes 2.2 times the amount, whereas lead acid is 2.9 or something like that. The way to calculate it is to determine the total amount of power needed to charge the battery from dead to full divided by the size of the battery.

I've done numerous tests myself, and the charge rate is about exactly 2.5 to 1 for the NIT at 5v, 500ma, which is the standardized bar by which I do all my testing.

Re: Charging with external battery - possible?
 

Funny, I also just did some look around for an external battery-pack. And in the end I came to similar results: a 12V supply with a car charger would probably do the best job. Batteries are available in different shapes and sizes and might be tight to any part of the bike or your backpack. And when using some kind of universal car charger with many adaptors you could even charge other devices too.

Another idea would be this little thing. A solar charger with one great benefit over other solar chargers: you may line up several of them to increase power output. As usual you can directly use solar plate for charging (not recommended at night!) or fill it up with rechargeable batteries.

Downside is the price of course. 30€ for one piece and probably best useful when lining up two or three pieces ....

http://www.conrad.de/ce/de/product/200285/

Re: Charging with external battery - possible?
 

Btw the small Nokia tip adapter I received with my Tekkeon MP1550 is very inefficient, atleast it gets very hot, and there's only about 250mA-300mA charge current going to the N810. I just used another tip/cable/adapter thing I got with some emergency chargers from certain chinese discount online shop, gave about 500-800mA, depending on the strength of the AA batteries inside.

Re: Charging with external battery - possible?
 

The following is a thread for people who have some time to kill: http://talk.maemo.org/showthread.php?t=14139

The following is one interesting comment from the same thread: http://talk.maemo.org/showpost.php?p...&postcount=165

Re: Charging with external battery - possible?
 

I now started building my selfmade charging device. The electric-circuit is finished (and works) but there are problems with the case... (This f*****g german electronic online shop has wrong descriptions of its parts and now the battery pack is some mm too big for the case and it has to be external.)

here a pic:

http://www.unika04.de/priv/ex_usb_chargr.JPG

The good thing: with the snap-fastener I can connect every size of battery-holders.

I even could test it: 3:05 hours runtime with a completely empty internal battery, 4 external AA batteries, display and gps running. I noticed, that the internal battery doesn`t get charged - its power level is at about 0% all the time (read out with kcbatt).


Thats really bad efficiency. I`ll have to try the direct version. Just ordered two verry cheap BP-4Ls from Hongkong (just for the connectors to build a dummy for the internal battery leading out the cables to power it external).

In theory (I know there can be other loss or the device shuts down before the batteries are completely empty if the voltage drops to low) 3 AA batteries with about 2800 mAh should be able to run the device 1,8 times as long as the internal battery (1500 mAh). With the internal battery its runtime with display and GPS on is about 4 hours. So it should be 7,4 hours (connected directly without charging-loss)... I`ll give it a try.

Re: Charging with external battery - possible?
 

I think the following are the formulas one can use to compare the energy a battery can hold: 4 external AA batteries of 2100 mAh can produce 4*1.22V*2100mAh/1000 = 10.3watt-hours while a 1500mAh Lithium battery can produce 3.7V*1500mAh/1000 = 5.5watt-hours. On the other hand the voltage of the alcaline batteries drops a lot so much of the energy can not be utulised.

Notice that these connectors are often very bad - one have to use additional support for the battery to make the electrical connection stable. And I have had a cheap battery that I was unable to use even with support.

Re: Charging with external battery - possible?
 

Basic linear regulators are really bad for efficiency (since they basically feed all the extra voltage to ground...), you need step-down/step-up regulator.

For my experiments on the subject see this thread.

And a picture of one of the results: the frankencharger

edit: also this from DX might be a interesting to you

Re: Charging with external battery - possible?
 

Ya know, you bring up an interesting concept. I've actually been working on a design for a bike powered battery charger. It's right now only for use with my bike, as it'd charge a bank of super capacitors that would then be used to power lights and other necessities. But in time it'll be modified so that I can prop the bike up on an improvised rear kickstand and use that to power or charge other items. And the capacitors *should* have enough power to give me 30 minutes of power for most devices with only 3-5 minutes of hard peddling. At least in theory. Reality may end up being a different story, but we'll see. ^_^

Re: Charging with external battery - possible?
 

Mhm... Let`s hope I get them working. I think direct powering the device with a battery adapter is the only efficient, cheap and realizeable possibility for my needs. Every device that can be built or bought that gets connected to the charging-input will waste over 50% of the energy.

Does someone know, at which voltage of the internal battery the N810 shuts down?
And what do you think is the maximum voltage that the internal battery can do before the N810 gets demaged? A full charged BP-4L hat 4,1V... Max should be at least 4,2V - the end-of-charging voltage for Li-ion - or not?

Re: Charging with external battery - possible?
 

Sorry for coming late here, but a few comments:

- the N8x0 (like any modern gadgets) have their own built-in regulator, so it would be ideal to avoid needing a second external regulator.

- I read the Nokia 2mm spec, as linked above by Fontus, allows up to 9.3V, so a 2-cell Li-Ion battery should work fine. However it appears that Nokia do not follow their own standards. Connecting one (7-8V) results in a "not charging" message on my N800 and on my Nokia phone
Note that this does not damage the tablet - it simply refuses to charge.

- But 5-6V in does work on my N800 and phone. A 4xAA NiMH pack can be directly connected to the 2mm Nokia plug.

- to enable hot-swapping internal batteries, you could add a capacitor inside the NIT across the battery terminals. e.g. 0.1F 5V. A software hack to make the screen stay off when battery cover is open would help.
Might need a small resistance in series (if lacking Ri) to limit current when the new battery is inserted.

- if you do want a cheap, light 5V regulator, see http://www.dealextreme.com/details.dx/sku.29208
(has micro-USB plug, so needs cut/solder the cable)

- you could add one or two 18650 cells in parallel with the cell of the standard battery, and attached to the back cover. I don't know how well the battery electronics would cope with re-charging, but it would be slow at best. You might need an external charger.

riderman, where do you get the <50% efficiency from?
I'd have thought 4xNiMH, or 2xLiIon+switchmode reg would do much better. Are you assuming the N8x0 uses a linear regulator?

That guy using a 7805 to convert 12V->5V made me shudder.

> Does someone know, at which voltage of the internal battery the N810 shuts down?

The battery has a safety cutoff (~3V?) but the tablet will shut down before that happens. You could just run the device flat, then measure the voltage. Why do you ask?

Re: Charging with external battery - possible?
 

Do note that the spec has current limits that are pretty low at 7-8V. If you connect 2 Li-Ion batteries in series, they're able to provide several Amps of current, which exceeds the maximum specified in the charger spec. This is likely why you get "Not charging" message.

Battery low warning comes at 3.5V on internal battery, there are atleast 2 layers of sofware shutdown, with the first one happening shortly after battery low, and the second (backup?) shuts down the device at 3.2V..

Re: Charging with external battery - possible?
 

today the china batteries arrived. Okay, they won`t win a price for their connectors... But it works.

I just opened one of them, removed the inner li-ion cell form the electronics, connected the cable to extern batteries with it and putted some plastic in for replacing the cell.

For security there is a schottky diode in the cable - this changes the voltage by -0,3V and secures it against inverted voltage.

Tomorrow I`ll test how long this will run the gps and the display.

http://www.unika04.de/priv/N810AA.JPG

Yes I know... I still need another battery holder :D


Because I did noth think about it myself before writing :)

Re: Charging with external battery - possible?
 

riderman,
are you planning to use NiMH cells? You will not get so much runtime from the alkaline ones.
Some 18650 Li-Ion cells (e.g. from DX) would be even better.

I don't know: it's nice to have room in there for the 500A fuse.

Here is my on-the-road charging arrangement for the N900. You could change the connector to suit N8x0.
The small regulator is http://www.dealextreme.com/details.dx/sku.29208~r.60561251

http://media.share.ovi.com/m1/s/1893...c1ae1afaf1.jpg

Re: Charging with external battery - possible?
 

That is not clear to me.
Isn't it up to the device to draw it's desired current? The charger cannot choose both voltage and current.
Are you saying that the charger is expected to enforce the 950mA current limit? I thought the device would do that.
OK, it is making a bit more sense as I think about it.

Re: Charging with external battery - possible?
 

i use a sonyo eneloop externel battery http://www.eneloop.info/index.php?eI...729fcc5b6fc3a1

that has 2usb out ports. Using an Y-usb cable from a external harddrive with an adapter to micro usb i get up to 1000 mA out of the battery which seems to charge the N900 the same way the Nokia charger does, at least according to batterygraph. The battery has 2000mAh and was about 35€ on amazon, the adapter and the Y-cable should be about 10€. And my impression is that the battry holds the charge without much loss, i left it for about two weeks in my pocket and the recharged th N900 one time without a problem.

Re: Charging with external battery - possible?
 

No, my main goal is to be independent from charging-possibility for some days. Okay - I could buy me about 20 of them...

Let`s see, for how long 3 AA Alkaline run the device...

Re: Charging with external battery - possible?
 

From my observations of N8x0, the charge regulation is done through a slow PWM (about 1Hz). Even if the software set it to the lowest, 1/255, there'd still be a huge current flowig into the battery for 4msecs every second or so..

Re: Charging with external battery - possible?
 

You seem to be under the impression that primary cells last longer. That was true once, but I believe that rechargeables now have a greater capacity than alkalines.
The 1.8V lithium AAs have good capacity, but are expensive.
If you want to keep the weight down, just use Li-Ion.

Re: Charging with external battery - possible?
 

actually, a few days ago i saw a tv-report on useful gadgets, and they were testing a solar-charger. it was basically just like the official external charger form nokia, just that you dont load that on the wall, but by the sun. and even though it was cloudy, it was loading the battery with full 5V.
i guess its worth a try.

i think the other dead sure solution would be one of those devices you have to wind up to generate electricity. takes a lot of time though...^^

Re: Charging with external battery - possible?
 

Li-Ion vs alkaline is a nobrainer, Li-Ion wins.. In extremely low-drain situations, it might be a dead race..

Not sure about the situation with primary 3.6V lithiums.. But I'd be nervous about using those anyway due to safety..