Is there such thing as a "D" cell NIMH "battery bank"
 

Hi,
folks on here seem to know a lot about batteries and im wondering
if there is such a thing as a "D" cell NiMH "battery bank" where you
just plug in rechargeable D - NiMH batts into some kind of a case
that would power/charge a Nokia N800 or even a laptop computer..

These D cell NiMH rechargeables are up to 12,000 mAH capacity
now, just four of them would equal my laptop's standard battery
and would be fairly convenient to use for that application or
for charging my N800....i have searched the internet, cant find
or dont know what they would be called, anyone have any
thoughts?

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

You can make one yourself if you want by frankensteining some D cell holders from radioshack and the circuitry from a 4xAA "battery bank".

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

It would make for an interesting project to be able to cobble 8 'D' cells together with the AA battery bank and run it as a mobile power pack from one's backpack/knapsack. I wonder how many hours of power that would provide with video running.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

24000ma

The included batter is 1500ma, so that is 16 times as much. If the standard battery does 2.5 hours of video, this would give 40hours. So you could basically run it straight for 2-3 days.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

Right, so 4 'D' sized batteries would be just about right for a full day's travelling. I'm assuming that video playback causes a spike in power consumption, so choosing the right kind of battery (Li-ion? NiMh? Alkaline) would play a part in day-long video playback.

What do you think?

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

My newest rechargable D cells have less total energy storage than my newest AA batteries. It's counter intuitive. But the industry seems motivated by volume to work on AAs, and so D cells haven't moved forward as fast.

I wish my electric socks used a pair of AAs instead of a single D. That would give me more than twice the endurance. They'd last all night (i do astronomy). And, they wouldn't stick out from my legs so much.

The battery inside the Nokia is 1500 maH. One might think that a single AA, at 2400 maH is better. And it might be. But energy is watts * time, and watts = amps * volts, and i have no idea what voltage the internal battery generates. Why does it have 4 pins? If it were just a battery, why not have two? Anyway, at the moment, all i know for sure is that i don't know the answers. Usually, you don't know what you don't know.

This rating in maH drives me nuts, since i think i'm interested in total energy. For example, AA disposable batteries say that they're 1.5 volts. If you measure a new one you often get 1.6 or more, and an older one might be 1.1 volts. Rechargable NiMH say they're 1.3 volts, but a new fully charged one might be 1.7 volts. And, under high load, NiMH holds voltage better than disposables, which makes a difference in cameras. But is it 1500 maH at 1.3 volts or 1500 ma at whatever the voltage happens to be? I generally punt the math and just see how long it lasts in a real device. That was the real question anyway.

I probably do know what the voltage is. It came up in another thread.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

Only if your laptop battery is 1.5V instead of ~12V (typical from back when they were all NiMH, not real sure what voltage they stack Li-ion cells to). I guarantee they're NOT 1.5V, though.

TANSTAAFL. Did you really think something that's smaller than your laptop battery and costs less would give better performance? ;)

But as drizek points out, a 1.5V cell's a 1.5V cell, so substituting C or D for AA or AAA cells will work. Substitute parallel gangs for single cells if you need more...

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

Either you've got a magic source for AA's or you're not buying full D's. If you can get 10,000mah AA's do tell where you're buying them! I suspect you just got ahold of some of those lame D2 batteries that Energizer is foisting on us.Don't buy D2's or C2's! They're not full capacity batteries!

Dig around on the web. You can get 12K mah D cells, and C cells that reach up int the 8-9k mah range. They cost about $10 per cell, though.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

Really? 12K? Time to build my own 4xD charger then. I'll keep the circuitry from my 4xAA charger and just cobble a bigger housing together.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

Here is where I get all my NiMH batteries. I pop for the low discharge type since it can be weeks to months between uses on some devices.

Here are some D-cell 10,000mA NiMH:

http://thomasdistributing.com/shop/a...ni0cci7f6g3n90

I have never used that brand nor ever used D-cells. I recently read some info on using them instead...it was one of the "...wow, I could have had a V8..." moments...

I always use the Sanyo Eneloop batteries, AAA & AA, and they will hold almost a full charge after a year on the shelf.

I am sure they will also have some regular, but good quality, D-cells in the 12,000mA range...plus their prices are excellent as far as I can tell. Better than RadioShaft for certain.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

What circuitry? 4xNiMH will put out near enough to 5V for charging,
no regulation needed.
I have a couple of those 7.2V nom. LiIon batteries, which do need a converter to get 5V.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

I too would like a better charging solution.
All the "chargers' I've found recently either use 1 AA or 4 AAA, I want one that uses 2 or 4 AAA, has a meter to tell me what it's status is, and has interchangeable tips.
Any links?
/edit - never mind, found the Tekcharge
does most of what I want.
/edit2- found it at ecost

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

That is the MP1550 that I just ordered. I have read several posts on the sprint board over on http://www.dslreports.com/forum/sprintmb . Overall it seems to get good reviews.

I can mention if you decide on a Tekkeon myPower MP3400/MP3450 make sure you get the newest revision as they had to make a hardware change because there was a very slight voltage spike on initial power up. And if were using a Cradlepoint CTR350 MBB router and the power supply the spike could kill your router. So, the good folks at Tekkeon decided to make a change to their product in order to prevent it from happening. Even though they said it was only the CTR350 that had the problem. But, ya never know...

I was on the fence for getting an MP3450 for the router as that is the more power hungry device. But went with the MP1550 instead because of the weight/portability side of things. I grabbed the 12 eneloop's and should be good for a solid 10+ hrs...probably closer to 12 hrs of moderate to heavy use.

Did you check out what they have over at http://www.batterygeek.com ? It's a good place to find ideas of what is out there in terms of portable power.

Oh, btw, I got the MP1550 on Amazon just recently for $19.99 + like $5 shipping. So with shipping it was $25. I like it because it does have a voltage regulator which for my use, the router, it really important. I am not sure how much the NIT can absorb in terms of flaky voltage. Not sure I wanna find out either.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

yea, my laptop battery is 10.8 Volts, but AC adapter in is 19 Volts,
so i guess an external battery would have to be 19v??
i dont have enough knowledge to make it, just saw that NiMH D
cells get you 14.4 watt-hours per batt for ~$10 each, maybe thought it was possible to rig together 16 x D cells(1.2 volts) for 19.2 volts
and roughly 230 watt-hours for $160 + parts, compared to
what they usually charge, about $100 for an internal ~70 watt-hour
battery....im just tired of these overpriced laptop batteries when
there appears to be a far cheaper solution

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

I reckon you need to weigh in the risk of blowing something up.
e.g. 10.8V is nominal. At full charge it will be 12.6V.
similarly, your 16 D-cells might be 22V at full charge, which is _probably_ OK.

Yuck! There are lots of reasons why everybody uses Li-Ion, even though it costs more.
You know you could run your laptop DIRECTLY off a 12V car battery. Or use a widely-available converter to charge the laptop.
Much cheaper and more capacity than "overpriced laptop batteries".

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

I'd recommend messing with some 18650 Li-Ion cells (I highly recommend protected ones unless you like explosions), at 3.7v 2000mah, that's equivalent to a 6000mah 1.5v cell, but smaller and lighter. Two of them, and a switchmode DC-DC converter (don't use a linear regulator) should last for a fair while.

Batteries: http://www.dealextreme.com/details.d...979~r.45363994

Chargers: http://www.dealextreme.com/details.d...151~r.45363994, http://www.dealextreme.com/details.d...105~r.45363994 or http://www.dealextreme.com/details.d...499~r.45363994

Much smaller and lighter than a D cell.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

For a cheap converter, get a car-charger for nokia phones.

Re: Is there such thing as a "D" cell NIMH "battery bank"
 

yea, i guess others on here know much more than i do on the matter...i just feel like im getting ripped off when im paying about
$1.50 - $2.00 per watt-hour for the standard laptop batts vs.
the NiMH batts at about 75 cents per watt-hour....i guess there
must be reasons though....

charging off a 12V car battery is not an option for me...best option i have is getting about 400-500 watt-hours of batts and recharge them every 3-4 days