[blessingx]

Bought a couple Plainview 9.6 batteries to run a Meta Mint. I also bought the recommended charger from that page. Problem is the site says "Overnight Charger - 8 to 10 hour charge time", the batteries say "charge @17 mA (max) for 14-16 hours", and Thomas Distributing's customer service person said "12-15 hours for a full charge with that charger". How long should I leave these things plugged in? And for those who use the recommended charger is there any indicator with light when it is fully charged, or should I just unplug it after X hours?

Thanks,
Ric

 

[HighwayStar]

Hey Ric,

When I was using them (dual 9s in a Meta) I'd pop'em in the chargers before I left work around 4pm and pulled them out in the morning 8/9am. I don't think they actually need that long but it was convenient for me. They didn't feel like they were heating up so I wasn't worried about damaging them. There's a single LED on the single chargers and it only indicates power not charging status. Just unplug'em after X hours... however long you decide. I'd imagine anywhere between 12-16 hrs would get the job done...

 

[Hirsch]

The dedicated Plainview charger should be able to charge the batteries from dead empty in about 8.5 hours. For the calculations, do a search on rechargeable batteries in this forum.

 

[laevi]

What have been the maximum voltages that others have been able to recharge the Plainview batteries? I think Plainview's own site recommended 1.45-1.5V per cell. I've only been able to get around 1.40V per cell max (11.20V total) using a Radioshack's cheapest universal NiMH/NiCd charger, which provides 23mA. I'd appreciate hearing the results others have achieved. Thanks.

 

[TheReaper]

Well just today I forgot to unplug mine before I went to work. So they got overcharged for around 20 hours. That gave me 11.35 volts on both batteries using the Plainveiw charger. I try to charge them usually for 12 hours. This gives me anything from 10.8 to 11.2 volts depending how dead they were from the start.

 

[Hirsch]

It is a BAD idea to routinely overcharge NiMH batteries. That said, the Plainviews should survive it. Thomas Distributing told me unofficially that they can go up to 24 hours in the charger without damage, but also discouraged the practice. Optimal charge time from dead empty is about 8.5 hours in the Plainview charger. OK to go a little past that (particularly if you measure the output current and it's not as high as it should be (25 ma)), but not much more. Extended charge times will eventually cause damage to the batteries.

Using the 23 ma Radio Shack charger increases the optimal charge time to 9.2 hours. The slightly lower trickle charge should in theory reduce the chance of damage if overcharged...but when I measured currents, the Plainview was accurate at 25 ma, while the Rat Shack was actually putting out 26 ma + of trickle charge (higher than it was supposed to). Not good, and could lead to unpleasant surprizes if the batteries were routinely left in the charger for very long periods.

The maximal voltage after charge is fairly immaterial, as that voltage will drop precipitously as soon as you start to use the battery. What's more important is that the battery be able to maintain its optimal voltage over a long period of time. If you damage the battery so that it can't hold a charge as long, it won't matter that the initial voltage is higher.

 

[laevi]

Hirsch, do you you know if draining a battery by connecting its two terminals will damage it? I'm a bit concerned about the memory effect of rechargeable batteries and would prefer to have the battery run down before I recharge it. However, I am concerned that "fast-draining" will damage the battery. Thanks.

 

[Hirsch]

Quote:

Originally posted by laevi Hirsch, do you you know if draining a battery by connecting its two terminals will damage it? I'm a bit concerned about the memory effect of rechargeable batteries and would prefer to have the battery run down before I recharge it. However, I am concerned that "fast-draining" will damage the battery. Thanks.

There is no reason to worry about the memory effect with NiMH batteries. The absence of that effect is one of their biggest advantages over NiCad. There are FAQ's at thomas-distributing.com on this. If you absolutely must drain a battery, there are chargers that have a "conditioning" circuit that will drain the battery safely. I wouldn't run a battery into a dead short, myself, but would put some sort of resistor inline at least. What I don't know is how much resistance (if any) is needed to prevent damage to the battery.