Primarily for general aviation discussion, but other aviation topics are also welcome.
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By Rob P
#1889872
Ever since acquiring my Lightspeeds about four years back I have used four Eneloop rechargeables, a pair at a time, rotating them every ten hours or so of use. This means that I never have to carry spares, and I have never had to change them in flight, or indeed anywhere other than the comfort of my home.

My co-owner recently purchased two SEHT headsets, and their instructions warn of death, mutilation, plagues of frogs and catastrophic headset damage if rechargeables are used. (The first three options might not actually be in the instructions. I am possibly paraphrasing)

Does anyone to whom electricity isn't a dark art have any suggestion as to what damage could possibly result from multi-use AA cells?

Rob P
By Dino
#1889885
Different cell types have different initial voltage outputs, eg:
NiMH's (a 'typical' rechargable) are rated at 1.2V initial voltage, which is lower than the 1.5V of alkalines (typical non rechargable)
on the other hand NiZn output up to 1.85v initially.
If the equipment is not designed to handle these voltages ..... :oops: :oops:
This site is a bit old school but quite informative about battery types https://michaelbluejay.com/batteries/
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By PeteSpencer
FLYER Club Member  FLYER Club Member
#1889888
I had always understood that rechargeables maintain their voltage till the very end then fall off the cliff within minutes to zero, while yer duracells slowly drop off giving you time to recognise this.

Not that sudden drop off is a such big deal I suppose.:wink:
By PA28
#1889894
I use rechargeable NiMH batteries in my Bose A20. They are fully charged at about 1.3V. They last about 4 days flying 5hrs a day. I know Alkali AA batteries will last longer because they are 1.5V but rechargeable batteries are cheaper in the long term.
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By MattL
#1889897
I just use Duracell ultra in my A20s and they seem to last for ages, it’s no snags to just swap them when I see the light change warning of them going. I’ve never seemed to get the same performance out of rechargeables and the drop off seems less predictable.
By PA28
#1889900
Apparently Duracell AA copper top batteries have a capacity of 2850mAh. This compares to 2100mAh for the Eneloop NiMh. The cutoff voltage for the headset to work will probably be around 2.3V which means 1.15V per cell. It doesn't take much use for the rechargeable to drop to this voltage and the headset to turn the ANR off. This is why they recommend only 1.5V AA batteries. Considering how expensive ANR headsets are it makes sense to run them on Duracells and carry a spare set.
Rechargeable AA at 1.25V will not damage the headset they just won't last as long.
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By Genghis the Engineer
FLYER Club Member  FLYER Club Member
#1889901
I have a pair of SEHT SH40-80s.

I also have loads of high AA rechargeable batteries.

My experience is that I'm lucky to get one flight out of the SEHT headset on rechargeables, so I've given up. I run them on Duracells, who work well and give me 10-15hrs per set.

My assumption, semi-informed, is that it's all basically down to output voltage. The chemistry in recharcheables has a slightly lower and degrading voltage compared to that in standard good quality single-use batteries.

If anybody can recommend rechargeable AAs that work reliably in a SEHT headset, I shall be in your debt, but until then, it's bulk buying Duracells.

After the headset has decided it doesn't like them any more, the Duracells run various alarms and remote controls perfectly adequately, so they don't usually get discarded immediately however.

G
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By Paul_Sengupta
FLYER Club Member  FLYER Club Member
#1889912
Genghis the Engineer wrote:If anybody can recommend rechargeable AAs that work reliably in a SEHT headset, I shall be in your debt, but until then, it's bulk buying Duracells.


I don't know if you can still get rechargeable alkalines, they were available some years back. You could recharge them something like 20 to 25 times but needed a special charger.

https://en.wikipedia.org/wiki/Rechargeable_alkaline_battery

The ASDA website seems to have them but not sure about the charger.

This charger is for recharging standard alkaline AAs (up to 10 times they say):

https://www.ebay.co.uk/itm/184670272998
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By Genghis the Engineer
FLYER Club Member  FLYER Club Member
#1889931
Interesting rabbit hole that just took me down.

1.5V rechargeable alkali batteries seem to have died out.

All my present rechargeable lithium batteries are 1.2V

However, I can see plenty of 1.5V lithium batteries for sale online. Looks like they do need different charging arrangements interestingly.

I'm going to buy a set of four of those, and see if they work in the SEHT. If they don't work, nothing really lost as they'll just go in the pool of rechargeable batteries I have here.

I shall report back.

G
Last edited by Genghis the Engineer on Thu Dec 23, 2021 5:36 pm, edited 1 time in total.
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By PA28
#1889934
Genghis the Engineer wrote:Interesting rabbit hole that just took me down.

1.5V rechargeable alkali batteries seem to have died out.

All my present rechargeable lithium batteries are 1.2V

However, I can see plenty of 1.5V lithium batteries for sale online. Presumably they'll work in my present charger.

I'm going to buy a set of four of those, and see if they work in the SEHT. If they don't work, nothing really lost as they'll just go in the pool of rechargeable batteries I have here.

I shall report back.

G

Those are the ones. Must use the charge lead supplied not a one for NiCad or NiMH.
By rdfb
#1889939
PA28 wrote:It would appear that you can now get AA high capacity 1.5V lithium ion batteries. These are rechargeable batteries.
They charge via micro USB.


This is it. These are voltage regulated to 1.5V so appear to be fully charged alkaline AA batteries until they run out at which point they will just die. So you don't get any warning of battery exhaustion but apart from that they Just Work.

They do have limited capacity but are easy to top up in advance so if you do this the capacity doesn't make a difference. Saves wasting partially used alkaline batteries if you want to avoid an in-flight change.

I already charge my tablet and power bank in advance of flying, so also doing my headset batteries isn't really any additional effort for me. I use a charger with multiple ports and the pair of USB AA batteries came with a splitter lead so only use one port.

And then there's no more waste or anxiety about half used batteries failing at just the wrong time (the radio would be OK but audible alerts for traffic and airspace would stop for me since I use Bluetooth to SkyDemon).

I do also carry a spare set of alkaline batteries just in case. They (unlike rechargeable batteries) have a very long shelf life. Never needed them.
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