AA batteries

[Csail]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

 

[neale]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

Could be a voltage thing. A new alkaline AA battery will give out around 1.6v. A fully charged rechargeable is more like 1.2v.

 

[cliff]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

Dry cell c. 1.5V, rechargable c. 1.2V. Internal resistance is different so rechargable could give higher current even though lower voltage - or so it was explained to me many years ago.

 

[AntarcticPilot]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

The voltages are different - 1.25 V for NiCD and NiMH as against 1.5 for non rechargeables . Another, rare type gives 1.65 V (NiZn).

The difference in voltage may well be significant for some applications; also at the lower voltage the current drawn will be higher.

There may be other factors such as different internal resistance.

 

[elton]

Rechargable AA cells are only 1.2 volts rather than 1.5 volts from normal cells, and the device may not have been designed to work at the lower voltage. This is most likely whan the device takes more cells. 6 rechargable cells give you only 7.2 V compare to 9V from normal cells.

 

[RivalRedwing]

From those responses I would give rechargeables a try - if the unit works then fine, if not then the lower voltage is v unlikely to have done any damage. Fwiw I use Uniross hybrio rechargeables in an old Garmin GPS12, they self-discharge at a much much lower rate than other styles of rechargeables

 

[Nigel_Ward]

I use recgargeables in an old Magellan gps with no problem.

The problem with comparing voltages is that these are with no load. In the past we have had a camera which would work with rechargeables but did not like alkalines because of the large voltage drop under load.

 

[Amulet]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

I use rechargeables in my Garmin GPS's with no problem - and they keep working even if the batteries drop to 1 volt. And yes - I did notice that they are lower in voltage than normal alkaline batteries.

Historically use of rechargeables was discouraged for low-current devices (e.g., clocks) because they went flat from self-discharge. The story (which matches my experience) is that modern "low self-discharge" batteries can be used in such devices. I use Maplin Hybrios. I believe Eneloop were the prototypical high street example (?)

By the way - a report, which I can no longer find, rated Maplin's own brand alkalines better than Duracell - I think they are less than half the price.

[If you followed the last thread I created you'd never take electrical advice from me. But that's another story!]

 

[EugeneR]

Here's my guess on this:

Rechargeables give +- 1.2v when charged; non-rechargeables drop to that level when empty. That means that without knowing the type, the unit cannot determine whether a battery is full, or not.

In turn, that means you might in some circumstances get a false "battery low" alarm when using re-chargeables or, conversely, no alarm when your non-rechargeable runs out.

The latter could be an issue since the user would could reasonably be used to getting an alarm before the battery goes dead, and might then sue the manufacturer if it the unit subsequently goes off without any warning at a critical time.

Also, rechargeables tend to self-discharge more so need a lot more replacing in my experience.

 

[Cruiser2B]

I use rechargeable alkalines - have the full 1.5V and are much more economical than regular alkalines. Dunno if you can get them over there: http://www.pureenergybattery.com/

 

[Whiskey Bravo]

Any reason why some kit says don't use rechargable AA batteries, the gps just eats normal ones.

Because they have an interest in battery sales?
We use rechargeables in hand held Etrex gps, last 2/3 days @ appx 7/8 hours sailing per day. Never had a problem.

 

[electrosys]

I've been using Uniross/Encore 2300 and 2500 mAh rechargeables for several years in 4 Lowrance/Eagle handhelds - which each use 4x cells and are a tad 'greedy'. Very happy with setup. Battery indicators show 3/4 full (of course) when fully charged.
Why 4 handhelds ? Well, that's a long story - but their value is now so low, I'd rather keep 'em than sell. But that means having batteries in 'em 24/7/365, or risk gradually discharging their lithium back-up cells.

I tested Uniross Hybrios side-by-side with Uniross 2300's, and when I checked a couple of months later the Hybrios were flat, but the 2300's still had enough capacity to drive the GPS. I then reversed the install, and exactly the same thing happened after another long period.
Can't explain my findings, except it may have something to do with the Uniross Sprint chargers I use - which are supposed to be 90 min chargers, but invariably take a good 2 hrs to charge 4 well-discharged cells.

I've now settled on normal Uniross 2300/2500 NiMH cells, which I have found will guarantee at least a 3 month life between charges, when installed in GPS's pulling less than 1 mA when switched 'OFF'.

I'll put the Hybrios on Ebay if anybody wants 'em - 2 sets of 4, with original packets. They've run less than 10 cycles.

I've also got a small stock of VapexTech 2400's which are the worst rechargeables I've ever used. Hardly a month goes by without one duff cell going into the bin. Not fit to use on anything important, nor would my conscience allow me to sell.

 

[Seajet]

I use rechargeable's on my backup handheld Garmin, no problem except a spare set of batteries ( at least ) should be on hand.

Mind, that was after I found out the hard way that the thing gets through 4 x AA Duracells in 3 hours

 

[DAKA]

Another vote for rechargeable alkalines, full 1.5 volt, good shelf life.

Try not to go below half charge too many times.

http://www.ebay.co.uk/itm/Pure-Ener...rElectronics_Batteries_SM&hash=item2eb7f996ba

 

[ctva]

I have many units that use AA and AAA batteries, Garmin, Sylva, Sony, Pioneer, Panasonic... the list goes on and they all say no rechargables. I've always use NiMH and Hybrid rechargables with no problems what so ever.