Battery will not fully charge - Piranha Charger.

[McKee]

I have a piranha digital charger and there are 3 settings on it.

Battery Type
Capacity
Current
Delta Peak


I have 2 1900 mah 8.4v NiCad batteries, and im charging them with the following settings.

NiCad
1900mah
2amp
6 mv/c



It will charge usually up to about 800mah then it finishes. I have tried varying the amps and changing the peak from 6 to 8 but i cant figure out whats going on with these batteries. Can anyone with experience with this charge help me out? The batteries were stored for a little while uncharged.
Thanks.

[Styrak]

A higher sensitivity setting (lower numerical value) instructs the
charger to be more precise when detecting peak. This is often
most accurate when charge current is set at a low rate. If charge
current is set at a high rate, the charger could possibly terminate
fast charge too soon as voltage fluctuations on the battery and
power source are more dramatic at high charge rates.

A low sensitivity setting (higher numerical value) instructs the
charger to be less precise when detecting peak. This means the
battery will likely be less full when fast charge is terminated, but
the charger is less likely to prematurely terminate fast charge as
a result of possible voltage fluctuations. A low sensitivity setting is
usually unnecessary when a low charge current is selected, but
could be more beneficial when a high charge current is selected.

That's from the manual. So I think they're basically saying that you should use a lower sensitivity (higher number) of mv/c so that it doesn't stop charging so soon. And don't take my word for it, but I think 2A is a pretty high setting.

[McKee]

Well im trying charging it at .2 amps seems to be working albeit very slowly. Im just worried that the batteries have been damaged somehow.. they used to charge in about an hour with these settings and it never prematurely ended...

[Styrak]

Actually I just read NiMH batteries like to be charged 1:1. So 2A is about right.

[Mysteryfish]

They're NiCad...

Sounds like they need conditioning -

I don't know how much time you have to spare, or whether or not you have a discharger, but I've brought a handful of really shitty batteries back into service by doing roughly the following:

- Charge at a low setting until they have taken all the charge they'll hold
- discharge (with discharger) until properly dead
- Charge at low setting (very slow is better) again until they've taken as much charge as they will
- Repeat a couple of times

Re-conditioning the batteries can help reverse the effect of the NiCd 'memory' effect.

I don't claim to know the science behind it, nor will I stand behind my procedure as the best method. All I can say for sure is that it worked for me, more than once. Remember to charge them at a very low setting. It'll take a full day to get a charge into the battery.

[ThunderCactus]

yeah my pirahna works flawlessly on all my NiMH batts, fills to 100% capacity, but NiCd batts can cause problems with any charger

[Mantelope]

I recommend changing the current setting to Auto, it's one setting past 5A. If you're decreasing the peak sensitivity, make sure you monitor the batteries for heat. If they're getting too hot to hold continuously, there's something wrong. You should be able to keep the battery in your hand for the entire charge, hypothetically.

[McKee]

Ok i'll try one of them on the auto setting and i'll try charging slowly and discharging. Charging at .2 amps with a peak of 8 m/vc got it up to about 1500 mah then it died on me, so i'll discharge and try again and see if i get anywhere. Thanks for your input everyone I don't know much about battery science so thank god for this forum.

[LeGROS]

For sure it a trouble with the the memory here!! You have to charge and discharge it to re init is memory... and the trouble with NiMH batts is they are very fragile!!! Never keep for long a batt you don t used charge!! Better to keep it dead!!!

The price to build a new one is very low!! About 15$ box!! You just have to buy 7 cell (charge batt) 1,2v at 2000 amp you place in line than your in!!!

I made All my batt my self now and it very effective!!! And save a lot!!

[McKee]

Well thats the thing my batteries are NiCad.... basically I used them a few times never had a problem with them, discharged them and they remained stored for about a year.

I tried using the auto setting, no luck it didnt even get past 80mah

[Drake]

Yeah I have one of these chargers too, and had similar problems when trying to charge a battery that was stored for a long period (actually found it easier to stick it into my old timer fast charger/discharger for a couple of cycles).

Like Styrak said, use a very lower sensitivity since it's NiCad, and use a lower amp setting (try 1 or 1.5, which is what my crank charger puts out while charging them). Check time yourself and watch the batteries for overheating (you're looking at about 45 minutes of charging at those settings, for 1900mah packs).

If the pack gets more than just warm, stop it.

Then discharge the battery.

You may need to do this a couple of times, but the pack will eventually get back to normal. And NiCad memory is a near-myth (it's been highly exaggerated by people who hear about it and don't fully understand what's going on).

[Spa]

Originally Posted by Styrak

Actually I just read NiMH batteries like to be charged 1:1. So 2A is about right.

when you start gonig below 1800mAH the ratio is around 0.75:1