Is there a use for cheap battery chargers as a second charger?

I am not a battery expert, but there are great resources and threads in the stickies on NiMH batteries and chargers. The reason I'm posting is I saw this at Costco the other day for $25 and almost bought it.

Think about it: Would Sanyo include a charger that destroys their batteries? Yes, you can likely stretch the life of batteries by periodically conditioning them and slow charging , but the included charger is fine. It makes a nice travel charger.

Thanks, I thought so. Rather than a $60 8-slot charger I think a $35 4-slot fancy charger plus this make a lot of sense. You're right, chargers don't hurt batteries, just sometimes they need some testing and conditioning. I'm going to get that.

If you live near a Costco, I think that's a great deal. Appreciate the response.

Conditioning is actually something normally not necessary in the lifetime of NiMH cells. The benefits of a quality charger really are...

• Ability to select a slower charge rate for when you have time, vs. a faster charge rate for when you lack the time. Slower is better, than routinely charging at the fastest rate!
  
• Ability to have charger stop or slow down when it SENSES the battery is full (like when charging a partially depleted cell), rather than mindlessly charging for a fixed amount of time.
  
• Ability for the charger to monitor the temperature of the cell as it charges, so that it stops if the cell has gotten too warm
  

Wilt wrote in post #16616000
As for Sanyo selling a charger which can hurt their cells...one way to look at it is that if it shortens the battery life, that is advantageous that you have to buy replacements a bit sooner!

I think they advertise 1500 cycles. If their charger shortened that significantly, the class action lawyers would be all over it.

mike_d wrote in post #16616006
I think they advertise 1500 cycles. If their charger shortened that significantly, the class action lawyers would be all over it.

I won't dispute that point.
The real disadvantage of the inexpensive charger may be it is set to a relatively slow rate, much slower than a known high rate that works well if the battery is never allowed to overheat.

The good chargers have multiple channels - one per battery - to allow them to individually control the charging.

And they can adapt to the temperature of the batteries.

But a slow 14-hour charger that charges the batteries two-and-two will also do a very good job even if it will overcharge most of the time - the charge current is so low that the battery doesn't get warm when overcharged (i.e. when the charge current converts to heat instead of into chemical energy).

The main issue with batteries is that they age faster when warm. Really much faster when hot. And as soon as they are fully charged, 100% of the charge current will convert to heat. A charger that charges two batteries/channel will not be able to handle the case when one of the two batteries are full a bit earlier than the other battery.

One reason for the big popularity of chargers with discharge function is that it is much cheaper to build a charger that can individually discharge multiple batteries than it is to build a charger that individually charges multiple batteries. So the discharge is used to "cheat" a bit and normalize the charge level before the charge is started.

People have then started to expect that chargers do need a discharge function - so even good chargers must be supplied with a discharage function even when the battery types used doesn't require it.

Anyway - any charger that takes less than 7 hours to fill the NiMH batteries should have individual charge channels. So one LED lit for every battery that is connected and charged. And one LED that changes color for every battery that has reached full. This will work great - extra great if people buy 4-pack batteries and tag them so they continue to use and charge them as a group. So they age similarly over their full lifetime. Having three strong and one weak battery in a battery pack means that when the weak battery has been drained, then the three strong batteries will be able to continue to drive current through that weak battery - which will continue to discharge an already empty battery and reverse the polarity of it. A great way to kill a battery that could have had many charge cycles remaining if used with a couple of pals of similar capacity.

^^^^^^^^^

Yikes! That's a lot of engineering talk! I don't read anything you write there as suggesting I should not get that product, however, if I read you right. I'm off to Costco in about an hour to get this, along with some other stuff.

If I understand you correctly, I'm safe for a while using these in marked groups (keeping them in caddies would be good) together. When I get the fancy charger, I can check the relative charges and pair batteries with close to the same charge for the cheap charger. It does charge in pairs apparently. So I'd use the one with a gauge to pair them up with similar charges, then put them in the cheap charger, while I charge 4 more in the fancy charger. That's my takeaway from all this, if I'm understanding you all correctly.

I just think 8-AA and 4-AAA Eneloops with that charger for $25 is a great deal, and it is a bonus if that means I can charge 8 batteries at one time but only spend on a 4-slot fancy charger. That's what drove this post.

This is the charger in that kit ...

It does take 7 hours to charge, so pairing cells in one charge unit should be OK?

Thanks, guys.

People worry too much about batteries. A pack of eneloops is $10-12 compared to $3 for Alkalines. Even the batteries only lasted 10 charges you just made $20. And then we have people arguing over this brand getting 1000 vs 800 charges in a lifetime or a charger slightly reducing the life of batteries. Just remember that best case you are protecting a fraction of the life of a $10 pack of batteries and typically you won't even notice.

ANY charger is fine, and honestly any brand of LSD battery.

Good to see its a 6-7 hour charger instead of a quick charger. I'm sure they lose some sales because of the longer charge time, buts its better for the battery in the long run.

The only possible issue would be the need to charge in pairs. But most devices take pairs anyway so its probably not that much of a practical issue. I do like my 8 port MAHA charger that can do any combination of AAA and AAA in any quantity. I have a large reserve stock of NiMh batteries so being about to charge quickly or in odd numbers isn't that important.

They would not sell the Eneloop batteries with a charger they didn't think would be good for the batteries - so you are fully safe to use that charger.

Any charger taking 7 hours + can normally be considered safe for use. They are slow enough that they don't overheat the batteries even if they fail to detect "full" and runs until the timer deactivates them after 7 hours.

No - you would normally not need to pair your new batteries. They are quite closely matched from factory so should also age quite similarly as long as you keep them together and don't mix with other batteries.

End-user pairing of batteries is mostly needed if someone have managed to mix multiple sets of batteries. But it isn't easy to do at home, i.e. figuring out batteries that can hold the same amount of charge and have the same internal resistance and that charges at similar speed. It's way easier to put a mark on the batteries directly when you get them to know which is set #1 and which is set #2.

tkbslc wrote in post #16616127
People worry too much about batteries. A pack of eneloops is $10-12 compared to $3 for Alkalines. Even the batteries only lasted 10 charges you just made $20. And then we have people arguing over this brand getting 1000 vs 800 charges in a lifetime or a charger slightly reducing the life of batteries. Just remember that best case you are protecting a fraction of the life of a $10 pack of batteries and typically you won't even notice.

ANY charger is fine, and honestly any brand of LSD battery.

I don't fully agree. Getting 800 or 1200 cycles is just a question of economy. But some chargers may accidentally cook batteries - so a battery can go from "good" to "broken" over a single charge cycle. I have tried expensive microprocessor-controlled chargers that have ended up sizzling batteries. If that sizzling ends (maybe after a very late timer-disconnect) before the user notices it, you can have a real battery killer. And might end up with non-working batteries at the great day. It's more about trusting the batteries than optimizing the lifetime of them. Especially since the really quick chargers feeds enough power to burn your house down if they goof the full detection and there is something wrong with the temperature detection.

pwm2 wrote in post #16616136
End-user pairing of batteries is mostly needed if someone have managed to mix multiple sets of batteries. But it isn't easy to do at home, i.e. figuring out batteries that can hold the same amount of charge and have the same internal resistance and that charges at similar speed. It's way easier to put a mark on the batteries directly when you get them to know which is set #1 and which is set #2.

Excellent advice, thanks!

I have problems keeping batteries paired so I just buy different brands/colorings every time I get a new set!

I was wondering why those batteries were not all the same color in that product photo. Now I know!