Rechargeable Battery mAh Questions... **DULL POST**
Discussion
Please note, this is a very dull post.
I need 4 rechargeable 'D-sized' batteries for a portable radio - can anyone with a greater grasp of physics (ie: any grasp whatsoever) help?
I've found plenty around the 3000mAh mark, at around £7 a pair, but they seem to then step right up to around £11 per battery going up into the 10000mAh range - I was hoping to find some Li-ion 'D-sized' batteries, as I assume they would be better / more powerful, but can't seem to locate any.
So, I'd need to spend circa £44 for four (non Li-ion) batteries rated at 10000mAh each.
I have however, found some 9900mAh 'AA-sized' Li-ion batteries, circa £1 each and it seems you can also buy a little converter to turn two of them into a 'D-sized' unit.
My question is, if I have four pairs of 9900mAh AA batteries, inside four 'D-sized' converters, would that make each of my converted Ds 19800mAh? Or would the combined two AAs still make the converted D be rated at 9900mAh?
Even if the latter is the case, this still appears to mean I could buy 16 of the Li-ion AAs for circa £16, to create 4 'converted' Li-ion Ds at 9900mAh...
This would be paying 64% less than if I'd bought the original £44 10000mAh 'D-sized' set.
Or, as I suspect is the case, have I completely made this all up?
Dr Steve said:
If the radio is designed for 'normal' D-size cells (1.2-1.5V) you don't want to be using 3.7V (4.2V when fully charged) cells.
On a second point, 9900mAh for a AA sized cell seems a lot, about 10x what I would expect.
There's several listings with 9900mAh AAs for sale, but possibly I'm rading it incorrectly? Or they are just fake!On a second point, 9900mAh for a AA sized cell seems a lot, about 10x what I would expect.
https://www.ebay.co.uk/itm/UK-20X-UltraFire-18650-...
Sterillium said:
There's several listings with 9900mAh AAs for sale, but possibly I'm rading it incorrectly? Or they are just fake!
https://www.ebay.co.uk/itm/UK-20X-UltraFire-18650-...
That's an 18650 battery, not an AA battery.https://www.ebay.co.uk/itm/UK-20X-UltraFire-18650-...
9900mAh sounds very high even for an 18650 - I thought the best (genuine) ones went up to 3700mAh (ish).
Your radio will probably be combining the 4 D cells to make 6v.
So you either rewire your radio, or you need to put 1.5v batteries in it, in whatever way you convert each D "shape"
The energizers are NiMh - if you are looking for long duration use, they'll disappoint, but they will work. The have the added pain of self discharging quickly. (Unlike Eneloops).
So you either rewire your radio, or you need to put 1.5v batteries in it, in whatever way you convert each D "shape"
The energizers are NiMh - if you are looking for long duration use, they'll disappoint, but they will work. The have the added pain of self discharging quickly. (Unlike Eneloops).
Edited by anonymous-user on Tuesday 18th February 16:16
As said above, don't get confused with Li-ion 18650s. Personally I'd get AA-D converters and just use 4 Eneloops. Buy a pack of 10 and a good quality charger and you'll have a set fully charged and ready on constant rotation. Also useful for other devices.
I've got Fujitsu Pros and they're all a reliable 2400+ mah.
I've got Fujitsu Pros and they're all a reliable 2400+ mah.
timmymagic73 said:
As said above, don't get confused with Li-ion 18650s. Personally I'd get AA-D converters and just use 4 Eneloops. Buy a pack of 10 and a good quality charger and you'll have a set fully charged and ready on constant rotation. Also useful for other devices.
I've got Fujitsu Pros and they're all a reliable 2400+ mah.
Now I'm even more confused... surely I'd need 8 AA Eneloops to create 4 'converted' Ds? So 16 required..?I've got Fujitsu Pros and they're all a reliable 2400+ mah.
And am I right in thinking AA Eneloops would be Li-ions and that you can't get Li-lions in D size?
Richie C said:
Eneloops are a more modern NiMH that discharge more slowly.
Re adaptors, I've seen some that take a single AA, others that take 2 in parallel. Might be a good option as then you'd get double the mAh.
Yep - they discharge so slowly that they guarantee some impressive numbers. I use them in my fireworks business as I need my batteries to not be flat when I need them in a hurry. Worlds apart from regular Ni-Mh.Re adaptors, I've seen some that take a single AA, others that take 2 in parallel. Might be a good option as then you'd get double the mAh.
How big is the radio? As in, when you whack a set of Duracell D Cells in it, how long do they last?
If the answer is "they last forever, I have no idea when I last bought some" then cheap rechargeable D cells will be fine.
A Duracell D is about 15,000 mAh, 1.5 v
A cheap rechargeable D is about 3000 mAh 1.2v. It's actually a C cell in a D cell package.
So if your radio lasts forever on Duracell Ds, it will last for ( forever/5) on cheap rechargeables.
With NiCd rechargeables, you don't want super low drain applications - flattening and recharging the batteries fairly regularly helps them last longer. You really don't want those 10 Ah NiCds to be under used - they fail very fast.
LiIon are generally 3.7V per cell, you could make a pack up, but then you need a separate charger for that pack. 6V is also a bit tricky for LiIon- it's either 7.4 or 3.7. The radio would probably handle 7.4, but maybe not.
If the answer is "they last forever, I have no idea when I last bought some" then cheap rechargeable D cells will be fine.
A Duracell D is about 15,000 mAh, 1.5 v
A cheap rechargeable D is about 3000 mAh 1.2v. It's actually a C cell in a D cell package.
So if your radio lasts forever on Duracell Ds, it will last for ( forever/5) on cheap rechargeables.
With NiCd rechargeables, you don't want super low drain applications - flattening and recharging the batteries fairly regularly helps them last longer. You really don't want those 10 Ah NiCds to be under used - they fail very fast.
LiIon are generally 3.7V per cell, you could make a pack up, but then you need a separate charger for that pack. 6V is also a bit tricky for LiIon- it's either 7.4 or 3.7. The radio would probably handle 7.4, but maybe not.
RogerDodger said:
Trustmeimadoctor said:
Are ikea batteries still the same cells as enloop just alot cheaper?
A quick google - says - apparently so!btw - Panasonic claim they will be 70% full after 10 years, left standing. Impressive. When you buy eneloops, they come charged - that tells you a lot.
edit; removed comment as I'm not sure I understand the technical details to say these are the same battery
https://lygte-info.dk/review/batteries2012/Eneloop...
https://lygte-info.dk/review/batteries2012/Ikea%20...
Edited by Winterway on Thursday 20th February 10:26
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