A very curious NimH problem...

[PlayboyJoeShmoe]

I keep a holder with 8 nimh in the truck for my GPSr and EDC if needed.

I have several different capacity and a couple different brand but all as pairs.

The GPSr tells me low battery when the cells have maybe 1.22-1.24V.

But this morning I put two 2500 Energizers in the GPSr and didn't get a peep out of it. When I tested them tonight before charging, both were identical at .964V

They were in the case since late last week, and had NOT been in the GPSr since last charged.

All the other batteries had no less than 1.21V each.

The 2500s have me puzzled. They are just about charged on my C Crane (showing trickle at 1.44V) and I will run them first in the morning.

On a related note, two 1850 Energizers showed 1.24V. I placed them in my 15 minute charger. But it didn't like one cell. So I'm going to see what the C Crane does with it next.

Overall though, NimH have given me WAY more runtime than Alks and have been troublefree for the most part.

 

[wptski]

It's always something!

 

[lamperich]

1,2xV
is it under load?

my experiacne with batteries is that it is very inaccurat if you measure the unloaded voltage


extrem example

a 10 year old D size Duracell alkaline
vs a already used AAA size alkaline.

the duracell was stored severel year.
so voltagerecovery was long!


unloaded voltage was High 1,55 vs 1,5 @ AAA
BUT if i put only 50 ohm @ it was like a David vs, goliath battle


the strong appearing duracell drop immediately under 0,9V!!!! and recovers back that voltage i cannot remeber... +1,2V
the resultat that my flashlight 2,4V 0,5A bulb doens´t glow bright wasn´t a surprise.


it´s a bad sign if a intelligent charger doesn´t except a NIMH anymore.

if unloaded voltage was 0,9 maybe overdischarge???
unfortunately it´s a hard time to tell you concret things about extrem situation.


Do you have a power supply with the ability to change the voltages in at least 0,1V steps down? Than you can see what the lowest voltage U(in) is.

 

[eebowler]

Playboy, you sure its not the GPS that's giving trouble and not the cells? How long did you use the GPS? Does it consume power when it's off? (did you forget it on by chance?) Did yo check any of the other pairs of cells charged at the same time with the two dead ones?

 

[PlayboyJoeShmoe]

I'm pretty anal about this. Charged cells face in, dead ones face out. I try to take self discharge into account and usually run the 1850s first, 2100s next day and 2500s last.

The 2500s were in the last pair slot facing in. They had NOT been in the GPSr or in any other conductive device since being charged. I only lack the knowledge of which charger was used.

 

[lamperich]

I'm pretty anal about this. Charged cells face in, dead ones face out. I try to take self discharge into account and usually run the 1850s first, 2100s next day and 2500s last.

The 2500s were in the last pair slot facing in. They had NOT been in the GPSr or in any other conductive device since being charged. I only lack the knowledge of which charger was used.

eeh i forgot to ask

What was the the ambiente temperature when charged and stored ?
iam sure it was cold in the truck... under 0 degree C??


Charging was a day before is that right?

 

[PlayboyJoeShmoe]

Charging could have been a week before possibly. I ran the 2500s in the GPSr today and after about 7:45AM to 5:30PM I see 1.260 and 1.264V.

Last week we had some high 20's F and low 32s F. I tried to put the holder in a warmer part of the truck.

The only really odd thing is all the 2100s and 1850s went through the same temps etc. and they all came out around 1.2V. And they all had a turn in the GPSr.

I'm not absolutely trusting my 15 minute Energizer charger.... It just wigged out on one of the 2500s.

 

[lamperich]

you charge the standard energizer 2,5Ah rech in the 15 min charger???
i read a test about the ansmann and Varta (rov) 15 minutes charger. (not compareable but nearly similar)
the first thing worth to mention is that standard NiMH won´t charge as fast as the 15 min rech.

sec. is that i read on a news page that sanyo designed low restistance NiMH AA especially for 15 min chargers.

it seems to me that it´s a not a good idea charging standard NiMH in ultra fast charger.
they feel good with 0,3-0,5C Charge current. slow charges are recommend.


Are you able to creat shootout like Silverfox did?
Than you would see clearer what the condition of your rechargeables really is.


P.S: I know such problems. 2 years ago i bought my first Digicam. with 4AA.
The "Power-On" led glows for a sec. that´s it. Was that a bad dissappointment.
Since i got my Akkutrainer3 (like a BC900 but with less Charg curreent functions) i see what happen if a digicam won´t wort.
Sometimes digicam stops working but in the rech. there is still plenty of energy left. -> very bad for high current timer charger (my 5 hour timer has only a 250mA charge curent but the cells GP with 1,8Ah (printed on the cells) become pretty hot. but not all.
other have totally different self discharge rates. What the exact reason is is hard to say whithout good equipment.
i recomm at least a charger with capazity check.(not pretty accurat but you see if one rechargable has a higher self discharge rate and if there is engery left in the cell) and of course slow charging. 4-3 hours. for a full charge.

Since i know that it works fine.

 

[SilverFox]

Hello Lampe,

It seems the Energizer 15 minute charger is using a very advanced charging algorithm. I have tried it with over 30 different brands and capacities of batteries, and it does a good job on them all, including the 2500 and 2600 mAh high capacity cells.

This new generation of pulse charging seems to be able to charge a higher rates and still keep the cells cool.

Tom

 

[wptski]

Hello Lampe,

It seems the Energizer 15 minute charger is using a very advanced charging algorithm. I have tried it with over 30 different brands and capacities of batteries, and it does a good job on them all, including the 2500 and 2600 mAh high capacity cells.

This new generation of pulse charging seems to be able to charge a higher rates and still keep the cells cool.

Tom

Tom:

MAHA had a pulse charger on the market years ago, it was a C210 and I have one. They then cam out with the C777PLUS without the pulse charging, so I asked why no pulse on this model. They said that the benefits of pulse charging was minimal! How things change.

 

[lamperich]

@ Joe:
due to i live in Europe we use degree C
32 degree means Freezing point of water (0 degreeC)

First of all i hope you didn´t charge your rechargeabels in such conditions a couple of times.
look: http://www.sanyo.com/batteries/pdfs/twicellT_E.pdf
Page 11 Verifying Batt temp...

Than typ. discharge voltage @ different temp.
Page 6 Fig.11
Iam sure NiMH´s of different Manufacturs will behave similar.
That´s exactly what the problem is with extrem situations.

@ SilverFox:

glad to hear...
but did you have longtime experiences with that??

Since it is possible to be very frutrated already with a 250mA timer charger iam not really convinced.
sorry

 

[SilverFox]

Hello Lampe,

No long term data yet... but I am working on it.

So far, I have over 60 charge cycles on my test cells utilizing the Energizer 15 minute charger. No problems so far...

Tom

 

[PlayboyJoeShmoe]

No, my cells always get charged at 75-83 (slightly more or less - room temp).

My Energizer 15 minute has problems with too many batteries these days. My C Crane handles it just fine.

A couple 2100s that were charged a few days ago did the GPSr just fine today.

 

[jayflash]

In spite of trying to pay attention I've goofed up and later realized I didn't really charge some cells that I could have sworn I did. See how those cells do after a few more cycles. I number or code my rechargeable cells to help ID and rotate their use.

Good luck PBJS & Happy NY to everybody!

 

[PlayboyJoeShmoe]

Man here we go again...

Two 2500 Energizers that along with two others spent quite a bit of time at 50mA on a slow charger. These two were third day rotation in my GPSr. They were out of steam before 11am today. EDIT: I was out of the truck doing service from about 9AM to 11AM when I discovered the GPSr dead.

Just checked 'em. 1.17ish V each. 1.32ish Flash Amps each. One is not any worse than the other.

Number 4 pair (also 2500s) worked the rest of the day until about 7:30P when I shut the GPSr down for the night.

These are NOT the same batteries as before either. They are marked different.

This is getting bothersome!

 

[PlayboyJoeShmoe]

Okay. The two problem children 2500s spent the night in my Energizer 15 minute charger. And I found the culprit. One has 1.42V 6+ Flash amp. The other has 1.29V and about 4 FA.

Only thing puzzling is how they come out even when discharged.

 

[lamperich]

flash amp?