Everready NiMH D cells in 6D ROP?

[MikeLip]

Hi. I have been gathering together the parts for my first homebrew and started easy with a 6D ROP. However, I ordered Everready D sized NiHM and am a little unhappy about them.

They appear to be nothing more that their AA cells in a D case. mAH ratings are identical to the AA NiMH in both cases - 2500mAH in botht eh AA and D cells.

So, my concern is this; I'm gonna be sucking a LOT of current out of these guys. Runtime will obviously be shorter than I'd like, but will the high current (approx 3.3A calculated of a fresh charge) be too much for the cells in terms of heating?

And is there a REAL NiMH D cell out there? Not just a recased AA?

 

[donn_]

There are a few, including some new low self discharge models:

http://thomasdistributing.com/shop/-nimh-rechargeable--d-nimh-batteries-c-122_104_248.html

 

[leeleefocus]

i would say don't bother with the eveready D cells. You are correct in saying that they are re-rapped AA cells. There are real ni-mh D cells out there but cannot remember the makers name of the top of my head. I'm sure someone will remember the names of some.

 

[Horse]

granted - Im new at this thing - but the link posted above has great sources - and I have had great service and support from this place:
http://www.batteryspace.com/index.asp?PageAction=VIEWCATS&Category=228

 

[MikeLip]

Yeah, OK - I found some real ones at Battery Junction. 10,000mAH. That's a little more like it. Now did I throw away my money on the Everready charger, or would it be able to charge these guys? I suspect it can if it's watching the voltage (which it *should* be doing) since it can charge all cell sizes. It will just take longer.

 

[MikeSalt]

As long as your eveready charger is not timed, it will be Ok. Delta-peak chargers will continue to charge until the cells have reached capacity, so these will work.

However, most D-cell chargers are 'dumb' trickle-chargers. Dumb does not mean they are bad, it just means that it will dump 150-250 mA of current into the cell, regardless of charge state. This is fine, but, for a full charge on those 10,000 mAh cells, you will need 40 - 66 hours charging at that rate!

 

[MikeLip]

OK, I pulled up the specs on the Energizer model CHFC NiMH charger and it is a Delta-peak unit! Charging current is 1100mA/Bay, with two cells max in each bay - so if you have tow cells, charge current is divided between them. This gives me about 550mA/Cell, so for a 10,000mAH cell we are looking at a 18 hour charge. Hmmm. Not completely unreasonable.

 

[MikeSalt]

I remember having some Uniross 2600mAh D cells in my 6D ROP. They were fine for a while, but then the capacity dropped sharply and I had to investigate why. After removing two of the cells, I found they had developed a rattle. Replaced under warranty, another two went a few weeks later. I concluded that, being that the capacity was identical to the AAs, they were in fact repackaged AAs. And the repackaging was poor, failing internally under the 4 amp ROP conditions.

I put the MagNum Star Xenon bulb back into the 6D, which the NiMHs handle easily. Not quite as bright as the same bulb on fresh alkalines, but the brightness is maintained for a much longer period.

 

[Bushman5]

so are there ANY NIMH "D" sized batts out there that are ACTUALLY "D" sized and not repackaged AA's? i dont feel like spending $30 CDN a cell and gettng ripped off. im not made of money

 

[MikeLip]

so are there ANY NIMH "D" sized batts out there that are ACTUALLY "D" sized and not repackaged AA's? i dont feel like spending $30 CDN a cell and gettng ripped off. im not made of money

Yes, there are. Battery Junction for instance sells them. Instead of 2500mAhr, they are 10,000 and over. They are also much more expensive. But for 4X the runtime plus the ability to handle the load better, I suspect they're worth it.

It's good to know that the load won't kill the cheapie cells outright. At least I can play with it until the right ones arrive! I may stick with the "low" output lamp though And if the 2500mAhr Ds die, so what?

Oh yeah - the Energizer charge WON'T charge the real, 10,000mAhr D NiMH cells. It has a shutoff at 6 hours for two cells in a bay, 3 hours for one. This in addition to the delta peak detection - probably it figures if the cell isn't charged by then, it's bad. Obviously not designed for real Ds. I wish there was an easy way to defeat the timeout!

 

[KevinL]

Oh, come on

ROP's require premium cells, yaknow

 

[Bushman5]

ah sorry bout that , i misread about the battery junction batts...i thought they were the ones that were rebadged AA's, my bad...

 

[MikeLip]

Oh, come on

ROP's require premium cells, yaknow

Are you implying that those crappy re-wrapped AAs Energizer is selling are less than optimal for this application?

 

[KevinL]

Are you implying that those crappy re-wrapped AAs Energizer is selling are less than optimal for this application?

As the official creator of the ROP I imply nothing..... one just needs to know that they stray from the prescribed recipe at their own risk

I simply urge people to design around some excellent high-amperage Sub-C cells that have proven themselves to withstand the abuse the ROP bulb throws at them

See if you can get Cheapbatterypacks.com to build you a high-current stick of six. Despite their name, there is nothing low-quality about the top-notch Sub-Cs they sell. Check out some of the Elite cells rated for 30+ amps. Now THOSE are cells that can survive under load.. 4 amps won't even begin to worry them!