[Strogian]

All right, I was just looking for some NiMH 9V batteries, and found the actual 9.6-volt batteries at thomas-distributing. However, they say that you should have a charger that has an output of at least 10.5 volts in order to charge them fully. I looked at my Rayovac PS9 9-volt battery charger, and it is labeled as a 9V/10mA output. Hoping that this is just a "conservative" spec, I measured it with my multimeter, and found that the actual output is more like 13.3 volts. This, however, is while they are not in a charging mode. (i.e. the red LED indicator does not come on) I then tested for the output of current, and it came up to be .100 A. When I tested for current, it was in charging mode -- the red LED indicator lit up. So, how would you suggest that I find the actual output voltage when the unit is in charging mode? Does it not even matter whether the light is on or not? Also, isn't .1 A equal to 100 mA, making it 10 times the output printed on the charger?

Or am I just doing something incredibly stupid here, by trying to measure it in this manner?

 

[Hirsch]

Search for the thread in the cable forum on rechargeable batteries. I posted a formula I got from Plainview for computing the time to charge an NiMH battery. Best bet is to get the Plainview charger, if you want to get them charged in a reasonable time period (takes about 8-9 hours)

 

[Strogian]

I think that formula assumes that you're using the Plainview charger, though. (or at least it assumes that you've got enough voltage to fully charge the battery) I'm trying to find out if this Rayovac charger has enough voltage to fully charge the Plainview batteries. I just bought it a couple days ago and burned the box, so I'd rather not have wasted that $10.

 

[Hirsch]

It's not a matter of voltage. It's a matter of amperage. Simply find the amp/hour rating of the charger, and plug it into the formula. Your charger will eventually charge the Plainviews, but it's a question of figuring out how much time it will take to do it.

 

[Nezer]

I'd highly recommend getting an intelligent recharger. One that looks at DeltaV with a safety timer.

I have yet to have a set of NiMHs last more than 10-15 cycles due to cheap-ass chargers. What happens is something will happen and the battery charger will get unplugged while in trickle mode and then replugged-in thus starting the whole cycle over on a fully-charged battery.

This causes a LOT of heat which leads to venting and potentially an explosion. Regardless the battery is shot after a stunt like this.

Thomas Distributing has some decent intelligent chargers for as low as $25. I would highly recommend you drop that POS Ray-o-Vic charger like a lead brick (which is not intelligent).

 

[Strogian]

Hirsch, why does thomasdistributing recommend that your charger output at least 10.5 volts, then?

 

[Hirsch]

Quote:

Originally posted by Strogian Hirsch, why does thomasdistributing recommend that your charger output at least 10.5 volts, then?

Their page may not be up to date. When I spoke to a technician at Thomas-Distributing, he mentioned the Energex Tri-Charger as a possible alternative to the Plainview charger, but that one is only rated at 9 volts. That's when I got the formula for computing charge time, which I confirmed through Plainview.

I think the problem comes when trying to use a "smart" charger with the Plainviews. The Plainview has a unique output voltage that "smart" chargers may have problems with. In addition, the "smart" chargers are putting out a much higher current than the trickle current in a slower charger, and if they get it wrong, the risk to the battery is much higher.

Note that Thomas doesn't offer a smart charger for 9v rechargeables, as far as I can tell. I compute the charge time, and then put the charger on an appliance timer so that it won't overcharge the batteries. However, Thomas told me unofficially that the Plainviews can stay in their charger for as long as 24 hours without damage.

The Plainview charger at 25 ma will get you the fastest charge time. The Energex at 16 ma is the next most powerful 9v NiMH charger they have, IIRC, but will take much longer to reach a full charge. You might want to contact tech support at Thomas Distributing if you want more information. They're pretty responsive, and Plainview is good at answering e-mail also.

 

[DarkAngel]

Quote:

Originally posted by Nezer I have yet to have a set of NiMHs last more than 10-15 cycles due to cheap-ass chargers. What happens is something will happen and the battery charger will get unplugged while in trickle mode and then replugged-in thus starting the whole cycle over on a fully-charged battery.

I have a "cheap ass" Ray-o-vac charger and 9 volts with @40 cycles on them for Grado RA1 and no problems. I just charge overnight and don't worry about formulas.........literature claims
500 cycles are expected life so in 10 years I will report back