How should I store Ni-MH batteries?

[appar111]

I was wondering what the best way to store ni-mh batteries would be. I'm using the gumstick size batteries with my Sony MZ-R55 and E90 and I've heard mixed things about whether they should be stored after they've been completely run down, or if they should be stored on a full charge. I had heard that when they're stored on a full charge they tend to dissipate slowly and if not recharged, they'll end up going completely dead and then can't be used after that...

So should I store them "on empty" as opposed to "on full"?

Any definitive answers would be appreciated, thanks!

appar111

p.s.
does it make any difference if they are stored in the freezer? I've heard they last longer that way....

 

[Eagle_Driver]

appar111,

It's best to store NiMH rechargeable batteries after charging them fully. However, if you find that they've lost some of their charge, you should run them down fully first, then recharge them before any serious usage. (This assumes that your MD gear's built-in charger has only a timer for charging control.)

On the other hand, if you have a 'smart' charger, simply recharge the batteries even if there's still a little bit of charge left in them.

 

[Watchdog]

Eagle Driver, I thought battery "memory" problems were a thing of the past.

Given your comment, it doesn't sound like it.

 

[Eagle_Driver]

The problem is not memory problems per se, but the bigger problem here is the potential for overcharging the batteries. If there's still a partial charge left in the NiMH batteries, and you simply plop them into a cheap timed charger to recharge them, the batteries will end up being overcharged - and that's what kills the useful lifespan of any rechargeable battery.

The truth is, Watchdog, that cheap timed chargers can - and will - overcharge the batteries.

 

[appar111]

so the chargers that are built in to most Sony MD recorders, such as the R55, are those just simple timer-based chargers?

and what kind are the wall chargers that come with the Sony MD players? The one that came with the E90 plugs into the wall, and you have to actually take the battery out of the player and put it in the charger. Is that a "smart" charger or a timer-based one?

appar111

 

[Eagle_Driver]

Likely a timer-based one, too. That's in order to save the manufacturers some $$$. Good 'smart' chargers are very expensive to begin with.

 

[appar111]

well, I've got enough of the ni-mh gumsticks to rotate-- one for the E90, one for the R55 and a spare... when the one in the E90 goes completely dead, I just rotate it with a freshly charged one. And the one in the R55 I use up fairly quickly around the house (since the battery life in the R55 isn't that great) and then I can charge it up when its empty by using the built-in charger.

so as long as I'm waiting til they're drained, I'm ok, right? I had heard that there was no "memory effect" with the ni-mh stuff. Maybe it's just not as pronounced... so if I top things off from time to time I should be fine, as long as every once in a while I completely drain it down, n'est-ce pas?

appar111

 

[Watchdog]

The overcharging makes sense, but I'm not so sure that the Sony charger that comes with the 707 is a timed charger.

I'm not saying that it isn't but, when I plop my unit down on the stand, sometimes it seems to charge for a long time, other times are shorter. I haven't timed it, but it doesn't seem to be the same amount of time each time, suggesting it's not a timed charge, but I am guessing a bit here.

 

[was ist los?]

in rc cars, for ni-mhs, people usually store them half charged.

 

[gaineso]

I think you'll find that the only controls on most of those chargers is you watching the clock and pulling the plug. I guess you could call that "timed". You can overcharge easily with those chargers, although the really slow chargers frequently don't have the power to seriously overcharge a battery.

 

[krayzie]

Never store the batteries after they're drained... try to store them after a full charge as they would slowly discharge over a period of time when stored...

If your Sony machine only comes with an AC Adaptor, then the charging circuit in the machine is a slow-charging one with a capacity sensing capability. If your Sony machine comes with a NiMH wall charger that has a red status LED, then it's a quick charger also with capacity sensing capability. Now when you start charging, the light would blink very fast meaning it is detecting the current power level of the battery, once it's finished detecting, the light would blink slowly meaning it's doing the 50% capacity quick charge... when the light stops blinking afterwards and just give a steady lid, it means it's doing a full charge. The battery is fully charge once the light goes off.... This is no timed as far as I can tell after all these years as charging time varies...

By no means the circuit has terminated charging after the light goes off... the light is only an indicator... The charging process will continue on until YOU pull off the charger from the wall... Sony recommends in their manual to avoid leaving the charger on the wall over 20 hours as overcharging would result then...

If your Sony wall charger is NiCd and doesn't even have a LED, then it's a slow charger like the built-in machine ones...

Hope that helps! (all these info is from the manuals of all my machines I've owned over the years... check out my profile LOL!)

 

[appar111]

I have the wall unit Ni-MH charger with the LED light, but I've never seen it blink-- it simply stays solid red for about an hour and a half (during the quick charge cycle) and then the light goes off, but the manual states that you should leave it on for at least another hour afterwards for maximum charge, but as you stated, not to leave it plugged in for too long (i.e. over 20 hours).

 

[Eagle_Driver]

Quote:

Originally posted by krayzie Never store the batteries after they're drained... try to store them after a full charge as they would slowly discharge over a period of time when stored... If your Sony machine only comes with an AC Adaptor, then the charging circuit in the machine is a slow-charging one with a capacity sensing capability. If your Sony machine comes with a NiMH wall charger that has a red status LED, then it's a quick charger also with capacity sensing capability. Now when you start charging, the light would blink very fast meaning it is detecting the current power level of the battery, once it's finished detecting, the light would blink slowly meaning it's doing the 50% capacity quick charge... when the light stops blinking afterwards and just give a steady lid, it means it's doing a full charge. The battery is fully charge once the light goes off.... This is no timed as far as I can tell after all these years as charging time varies... By no means the circuit has terminated charging after the light goes off... the light is only an indicator... The charging process will continue on until YOU pull off the charger from the wall... Sony recommends in their manual to avoid leaving the charger on the wall over 20 hours as overcharging would result then... If your Sony wall charger is NiCd and doesn't even have a LED, then it's a slow charger like the built-in machine ones... Hope that helps! (all these info is from the manuals of all my machines I've owned over the years... check out my profile LOL!)

Actually, I go by this definition:

Slow chargers: Require at least 10 hours to fully charge batteries
Quick chargers: Fully charge batteries in more than 3 hours but less than 10 hours
Rapid chargers: Fully charge batteries in three hours or less

By that definition, the charger built into most recent Sony players is of the quick-recharge (but not rapid-recharge) type, since they charge for between three and five hours, depending on the condition of the batteries. And the 'capacity sensor' built into Sony stock chargers doesn't kick in until the batteries have already been overcharged to a certain extent. Thus, Sony's stock chargers are 'smart', but not smart enough, in my book. A true smart charger has what's called 'delta-slope' and reverse-pulse termination that actually works to prevent overheating and overcharging - but Sony's stock chargers lack such 'smart' features other than an 'overcharged' sensor.

Quote:

Originally posted by gaineso I think you'll find that the only controls on most of those chargers is you watching the clock and pulling the plug. I guess you could call that "timed". You can overcharge easily with those chargers, although the really slow chargers frequently don't have the power to seriously overcharge a battery.

Fortunately, most of those chargers in which you have to watch the clock and pull the plug have all but disappeared from the market, except for trickle chargers that run at a much lower current than the C/10 from a typical slow-charger - and such a trickle charger is recommended only for maintaining a fully-charged set of batteries. A 'timed' (timer-controlled) charger simply runs for a fixed number of hours for a given battery type (i.e. a 3-hour charger with only timer control will run for the full three hours), regardless of the condition of the battery.

 

[krayzie]

I think those Sony rapid chargers that you plug into the wall by itself I talked about only come with older North American models and all current and past Japanese models... I forgot to mention this fact as I just remember a few domestic Sony portables I've bought which came with crappy quick chargers instead of the nice rapid ones (you know those with folding prones and a swinging door over the battery)...

 

[Eagle_Driver]

And on top of what I've said, the chargers that are built into most Sony CD and MD Walkman units (activated by either plugging the Walkman unit via wall-wart to a household AC outlet and then pressing Stop OR by placing the unit onto its charging stand) are also classified as 'quick chargers' with a 'capacity sensor', too. As such, they share the same problem as other Sony stock chargers - 'smart', but not smart enough.

Panasonic portables' built-in chargers, on the other hand, cut off a bit too soon, based on my experience with those units - even though they're still 'quick chargers with capacity sensors'. So, if Sony's built-in chargers overcharge the batteries somewhat, Panasonic's built-in chargers consistently undercharge the batteries. That's too smart, IMHO.

Either way, the useful life of the rechargeable batteries in either brand's players is shortened.