Nomad Battery

So I really wanna get my NOMAD up and running, but I have the same problem that many other people have. The official SEGA charge pack that I bought acts like it is charging but it apparently doesn't hold a charge. My main question is is there a way to get that puppy working again? I have heard that the Game Gear battery pack can also be used on the NOMAD, does anybody know if this is true? And final question, what rechargeable batteries would be the best for the Nomad? I bought some Li-ion ones but being the idiot that I am I didn't realize that they don't have the little top part like typical AA batteries so they wouldn't work. When running the Nomad with the Big SEGA Battery pack do I also need some AA's in the back as well?

there is 2 game gear packs one is a belt pack that has a rc car 7.2 v batt inside and the other is the back mount type

both will work but will not mount they connect through the powerjack on the top

it is possible to open the rechargable pack you need to break the inner glue holding the 2 pieces together i used a screwdriver handle and tappend around the seam a bunch of times like 20 light whacks per side took out the old pack and used rechargable aas i soldered into a 6 pack you could just remove the innards and fit a 6 aa battery holder and wire it to the connectors and then charge them individually with a battery charger or just use alkalines

a pack like this

http://www.pololu.com/catalog/product/1155

Edited only to add smiley to first paragraph to change it from snarky to snarky-with-a-wink.

Eh, no, the Nomad PowerBack (the Nomad rechargeable battery pack) isn't glued together, you don't need to "tap around" to get it open unless you're practicing the latest witch doctor rituals. ;)

The two shell halves are just held together with tabs-in-holes which are hidden in the seam between the shell halves. The cell pack inside MIGHT be glued to one shell half, it might not; I've seen it both ways. If it is, you can pry it out of the shell without worrying about damaging the cells since you're going to recycle those anyway.

If you want to get the PowerBack open with any hope of it staying closed again, see my post on how to do it. My following post in that thread gives some useful information in case you want to rebuild the pack to as-manufactured condition (but with longer-than original capacity).

Let me know if I can be of any help.

-tet

I kicked the dead elements out of my battery pack and placed some 12000mAh worth of NiMHs in mine and I've been happier than ever :)

Awesome, thanks guys! I'm gonna open her up as soon as I get some rechargeable Batteries to replace in it.

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Originally Posted by TmEE

I kicked the dead elements out of my battery pack and placed some 12000mAh worth of NiMHs in mine and I've been happier than ever :)

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Do you still use the recharging circuit? and how did you get 12000mAh in there? what batteries did you use?

I still use the original charging circuit (you need to wait 12 hours before it finishes charging) and I used 6x 2100mAh AA NiMHs I bought from store... I think they're from Varta

Hmm, so today after reading up a bit on the game gear battery pack (the one that clips onto your belt) I realized that I had been trying to charge it incorrectly and that was the reason I had never gotten it to work on my Nomad. You have to have the switch turned to ON when you are charging the pack, and have it switched to OFF when you plug it into your Nomad or game gear to play. Very strange. I had tried in the past with it switched to ON when I was trying to play and it never worked and I thought maybe the Battery pack was broken.

I charged it for a little over half an hour today and plugged it in to the Nomad and got about 10 minutes of Ghouls and Ghosts before it was empty. Still it was exciting at least to have the system running and to be able to walk around with it. I am going to charge the pack for a long time now to see just how much play time I can get out of this pack.

The pack clipping to your belt is rather nice as it doesn't bulk up the already large Nomad, like the official Nomad batt pack does, but I assume it probably won't keep it running nearly as long either. Does anyone know about how long the game gear battery pack takes to fully charge? I wonder if opening up the GG pack I might be able to update it with more powerful rechargeable batts.

I was thinking about getting one of those new portable genesis handhelds, but Ive decided I'm just going to stick with my Nomad. I like the Nomad and might one day send it off to be modded a little.

Hi TmEE, since you quoted two different capacities I'm assuming you meant the 2100 mAh number because I doubt that strapping your Nomad to a car battery does much for portability... :wtf:

Just a suggestion: I urge you to try charging those 2100's for longer than the 12-or-so hours that the PowerBack's timer circuit goes, because I'd bet Demons to Diamonds that you're not getting all the play time those cells have to offer.

Mmkay, I'm going to go ahead and give a full explanation here even though from reading your posts I know you know your electronic stuff. This is for benefit of the general public, plus just in case you didn't delve too deeply into the PowerBack's charging circuit. :)

The PowerBack's charging circuit isn't a smart charger, it's a dumb slow charger. The timer in that circuit is just that - a timer. It won't know you put higher capacity cells in, it'll just deliver its pre-set slow charge for the pre-set time, then stop. I have found that the most it will give is about a 1800 mAh charge. So unless you charge it longer, i.e. full charge, then pull and reinsert the plug for a few more hours, you aren't getting a full 2100 mAh charge into those cells. By my calculations, 2100 mAh cells on a full charge should give you between 4.5 and 4.75 hours play time on the Nomad.

There is one situation I can think of where my assertion may be inaccurate: If the internal resistance of your 2100 mAh cells is different (lower?) than the 1800 mAh cells I use in my PowerBack rebuilds, the longer charging I mentioned may need revision.

Since the charge-delivery part of the circuit isn't power-regulated, everything in the circuit affects how much charge current reaches the cells, including the internal resistance of the cells themselves. This is the part of which I am uncertain. I can't remember offhand if a higher-capacity cell has higher, lower or generally the same internal resistance, or if internal resistance merely varies with cell chemistry between brands/models etc.

The definitive way for you to determine the optimal charge regime for your cells is to measure the charge current during charge. Consulting my notes, the 1800 mAh cells I use draw about 150 mA during charge. A little more at the beginning and a little less when they're full, natch.

I have found the easiest way to measure charge current without opening the circuit is to measure voltage across R9, the blue ceramic power resistor. That part is easy to spot (thus easy to probe) because it's one of the most prominent parts on the board. Electrically, it's in series with the cells so it's a perfect place to get an accurate measurement.

If you do go as far as taking measurements, I would be interested in the results.

HTH,
-tet

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Originally Posted by snume

Do you still use the recharging circuit? and how did you get 12000mAh in there? what batteries did you use?

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I want some of those 12000mAh cells, too!

So the capacities of individual elements is not summed together ? In that case it is 2100mAh...

I did make a schematic of the charger part, but I never looked up what the chip is that it has.

I do get 8 or so hours of playtime on my Nomad from a 12 hour charge. I also decreased the value of the current limiting resistor which may also have an effect on how things go... When I got my pack, it had the fuse blown and that resistor dead, since all the cells were dead and shorted out.

...And your (Tetrode kink) electronic skill surpasses mine for sure :P

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Originally Posted by nathanallan

I want some of those 12000mAh cells, too!

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i made a batt pack that holds Ds

http://www.batteryjunction.com/tpeh-td12000.html

Quote:

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Originally Posted by TmEE

So the capacities of individual elements is not summed together ? In that case it is 2100mAh...

I did make a schematic of the charger part, but I never looked up what the chip is that it has.

I do get 8 or so hours of playtime on my Nomad from a 12 hour charge. I also decreased the value of the current limiting resistor which may also have an effect on how things go...

...And your (Tetrode kink) electronic skill surpasses mine for sure :P

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The chip is just a timer. It uses an RC pair for a timebase. It's no longer in production. I have the datasheet for it, I'll e-mail it to you if you want. I'd post it here but at over 500 KB it's too big for the board's file size limit for .PDFs.

8+ hours on one charge? From 2100 mAh cells? :shock:

OK, I'm going to have to call you on that claim! :) It just defies all logic, not to mention mathematics.

I can imagine a scenario where you might get 5 hours per charge. This would require two conditions to be met:

1. You actually get the full 2100 mAh from your cells, AND
2. That play isn't one continuous run, i.e. you use your Nomad the usual way where there are breaks when you turn the Nomad off.

In most cases, you never get the advertised mAh capacity from rechargeable cells. It's just the way it is. Some brands are better than others, but it isn't even predictable within the same brand :!:.

Also, like with most batteries, if you give them a rest period they will actually "recover" some charge, such that the total play time over several sessions until full discharge will exceed the total play time for one marathon session until full discharge.

If both of those conditions are met regarding your cells, you may well exceed 5 hours play on one charge.

But eight hours? It just doesn't compute. The Nomad uses about 385 mA. So if your cells truly deliver the advertised 2100 mAh, that's just under 5½ hours' play.

OK, so as not to be a hard-head about it, I'm prepared to believe the 8-hour figure under any of the following circumstances:

1. You fibbed, and instead of one string of six 2100 mAh cells, you have two strings of six 2100 mAh cells in parallel.
2. You modified your Nomad in some way to reduce its power consumption. Maybe you trashed the flourescent/inverter backlight in favor of a white LED backlight?
3. You really, really insist that that is the real number! :)

OK, that last one means I'm prepared to take your word for it, but if so, I'm going to have to re-learn everything I thought I knew about rechargeable batteries! :wtf:

Just out of curiosity, what value of resistor did you use in place of the 20-ohm R9? I'd be interested to know what the charge current is under your replacement.

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Originally Posted by bohokii

i made a batt pack that holds Ds

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Wow, how do you use that pack? Do you sling it on your belt or do you have it Duck-taped to the back of your Nomad? :D

-tet

my Nomad has a backlight mod, I couldo nly get 5 hours off single run with power comsumption held artificially at maximum, after backlight mod, under same circumstances, 8 hours. With normal playtime and me not having my headphones at max volume, the time might be a bit longer......

The resistor is 11ohms now (2x 22ohm ones in parallel).

He replaced the flourescent tube with LED's. I did the same with my Game Gear and essentially doubled the playtime from my battery pack as well.