Do rechargeable nimh batteries improve with age?

[Banjo]

I use rechargeable NIMH AA batteries in my Garmin Dakota GPS .I have had the same batteries for 2 and a bit years now.

When new I was getting about 100 kms per pair of fully charged batteries this crept up to 130 kms and yesterday set a new record of 168 kms before the battery warning came on.

I never use the backlight ,in the dark I use a headtorch instead.

 

[Yellow Saddle]

I once had to study a few battery technologies to find a suitable one for the job at hand. That was 10 years ago and the then current NiMH batteries certainly didn't improve with age. There was a slight improvement after the first four charges, then some stability and then pretty rapid decline. The lights that indicate that a charge is required work on voltage - of the voltage drops below a threshold, then it triggers. In the charge cycle it works differently. It had to do with the change in voltage, not ultimate voltage. I can't explain your case, but I'm watching this thread with interest, because your finding is counter-intuitive.

 

[Alan O]

When new I was getting about 100 kms per pair of fully charged batteries this crept up to 130 kms and yesterday set a new record of 168 kms before the battery warning came on.

Are you sure you're not just getting faster?

 

[keithmac]

Are you sure you're not just getting faster?

That was my thought as well!.

 

[Banjo]

Definitely not getting faster unfortunately.

One thought occured to me.I have started reducing the gpx file size to speed up loading it onto the gps and avoid having to split the route on longer routes.Would the gps use more battery processing a bigger file?

Typically the original gpx would be 600 kb after putting it through Simple GPX it is reduced to about 50 kb

 

[Yellow Saddle]

Definitely not getting faster unfortunately.

One thought occured to me.I have started reducing the gpx file size to speed up loading it onto the gps and avoid having to split the route on longer routes.Would the gps use more battery processing a bigger file?

Typically the original gpx would be 600 kb after putting it through Simple GPX it is reduced to about 50 kb

There we go. Mystery solved.

 

[Banjo]

An unexpected bonus to Simplifying the GPX file then.

I have been using this to reduce the file size.
https://simple-gpx.herokuapp.com/

 

[Hacienda71]

Temperature also has an effect on battery life. In colder temps they discharge quicker.

 

[Wobblers]

In a word, no. NiMH cells don't improve with age. How quickly they decline depends on the type - low self discharge types, particularly the Eneloops are longer lived - and more importantly, how well they're treated. A good charger is essential: overcharging is a sure fire way of killing NiMH cells.. My oldest Eneloops still have over 90% of their original capacity after 10 years. None of my conventional NiMH batteries have done that well. Typically, you'll see a slow decrease in capacity over time, accompanied with an increase in self discharge rate (meaning it's more likely that the batteries will be flat when you come to use them).

 

[the_mikey]

In my experience NiMh cells degrade with each charge, usually not noticeably unless they're overcharged, some cells will discharge themselves quite rapidly also.

 

[froze]

In my experience NiMh cells degrade with each charge, usually not noticeably unless they're overcharged, some cells will discharge themselves quite rapidly also.

This is mostly correct. The overcharge thing shouldn't be happening with modern circuitry in the charger designed to prevent that. What I noticed is that NiMhs don't last as long (terms of life expectancy not time to discharge) as other types especially NCad; my experience has been about 3 years with heavy use on small batteries found on bike stuff, vs 5 to 7 with larger drill or weed eater batteries. The only trick to making them last is to recharge then after EVERY use no matter how little it was used, they hate being discharged more than 50%. Anyway as time goes on the battery won't be able to hold a charge for as long as it did new, and it just keeps degrading till it no longer holds a charge.

 

[Blue Hills]

Are you sure you're not just getting faster?

Yes, exactly. For batteries have never been measured in distance for obvious reasons.

I got around 30 hours from a pair of 2500 lidl batteries last week in a garmin Etrex 20.

Pretty impressive/satisfactory I think.

The main thing is to use a clever/kind charger and charge them slowly.

I ignored this advice when I first went to rechargeables and used a fast charger.

Pretty rapidly fried my first set of Maplins rechargeables - most are now wrecked/seriously dying.

 

[Blue Hills]

overcharging is a sure fire way of killing NiMH cells.. My oldest Eneloops still have over 90% of their original capacity after 10 years. .

Good advice (and I should have read more of the came-to-late thread before posting above) but doesn't that somewhat depend on the charger? I thought quality chargers such as the Technoline

http://www.batterylogic.co.uk/technoline/technoline-BL700.asp

reduced charging once full to a tiny trickle.

By the by, does anyone have any opinion on Lidl low self-discharge batteries?

I think they tend to have a green stripe/somewhat green logo/marking or whatever.

I have the impression that they are not half bad.

Tend to be sold a couple of times a year or so.

 

[Blue Hills]

The only trick to making them last is to recharge then after EVERY use no matter how little it was used, they hate being discharged more than 50%. .

Interesting. So the old advice with many rechargaebles to deep discharge them at least every so often is a real no no?

I tend to let my light and gps batteries go to the bottom before recharging and otherwise just recharge them whatever state they are at before a major away from home trip or a long overnight ride where I want to avoid battery swapping.

 

[Alan O]

I've had a set of Eneloops for powering my computer keyboard, mouse and trackpad for probably around 8-10 years. I always run them until the computer complains they're down to a few percent (so they get deep discharged every time), I use a cheap old Jessops charger for recharging them, and any capacity they might have lost in all this time isn't enough for me to really notice.

And to add, I use my computer around 8-10 hours a day, every day.