over charging with smart charger.

[happykal]

It's happy kal once again with another battery/charger related question. I've tried to find my answers online, but no joy. So I bought a intelligent charger/discharger. I've read the manual (which left many questions un answered) and figured out how to set up and charge my nimh batteries. But When I tried to charge it for an hr i found it got hot and said the voltage of the battery was 11.25V. I thought this charger was supposed to stop at full charge and then beep like an oven timer. No?

I went to "save data" put in the info of the battery. "NIMH 1600 mah, 9.6 V. and saved it.

I go to program select "NIMH BATT"

next select cur. limit. i used 1.6 A hold the button 2 sec. and it picks up the battery info and starts charging.

Awesome, easier then I thought'd be. But i check on it in an hour and the Voltage read 11.25V and the battery was hot.

EX: NIMH 1.6 A 11.25V I can't remember what the capacity of charge said.
CHG 065:45 00000

I tried it with my other NIMH battery, loaded the data for a 8.4/ 1200Mah and it read battery voltage was 9.4V and kept charging.

I know there's got to be something I've over looked or misunderstood. if you could help me with my dilemma or point me to a tutorial. Because I couldn't find it on youtube and the forum. Thanks.

On a happier note I've changed all my connectors to deans. They are alot nicer and don't come apart in my handguard.

[JonsM4]

I believe you should be setting it at 1.2A.
Is this an iMAX charger?

[coach]

just as a note, you can use your old thread to continue a discussion of the same topic.

Now, what brand battery do you have? 1.6A is okay but you are ramming the battery with 1C of power and if it is of inferior quality, it will do as you noted and heat up. Excessive heat will slowly kill your battery if it is repeated regularly.

dial back your charging specs to max 1.0A, less if you have time to let it charge slower. The higher your charging amps, the faster the battery will charge but the trade off is heat.

what you are seeing with an over voltage is fine and common after a charging session. what you should focus on is the number of mAh the battery took. if the battery was dead or near dead, it should have an mAh similar to the mAh rating of the battery. if the battery had a charge and you were just topping it up, it will obviously result in a lower value.

eg:
1600mah battery that you used a little to plink but have a game tomorrow, only charged to 800mah is fine.
1600mAh battery that was completely dead, charged to 1500mah.

[Lucuis]

The higher voltage your reading isn't wrong, it's how batteries are rated. Generally each nimh cell is rated at 1.2 volts, hence 9.6v for 8 cells. However fully charged they generally read 1.5v if i'm not mistaken, which is actually 12v 100% charged up. It's the same with Lipos, each rated at 3.7 volts, but charged to 4.2v per cell. So your 7 cell battery, 8.4v will actually peak charge up to about 10.5v.

As already stated as well, if it's getting hot, turn down the charge rate. Some nimh cells can handle charge current better then others.

[L473ncy]

Here's an experiment you can do, if you have one a multimeter. Take some regular batteries in your house (Energizer or Duracell AA, AAA, or whatever). Set it to detect voltage on a fresh battery, do the same on a half dead battery, and a dead battery and what voltage will it tell you the battery is? Now what does it say on the packaging?

By definition voltage is the potential difference in something (also the amount of "push" it can push current through a wire). Therefore when it's full of juice there is more potential difference hence more voltage, if there is less juice there will be less voltage and hence will not be able to push current fast enough to power your motor which is why at the end of the day (or middle of the day if you shoot a lot) you'll start to notice when your battery is starting to die.

FYI my 9.6V 2800 mAh NiMh batteries will say something like 11.5V after a full charge.

Also it should "trickle" charge when the battery is done fully charging. I don't know how much it is but I think it was something like it will push 50 mAh into the battery to keep it fully topped up when it's done fully charging.

[ThunderCactus]

You need to put more voltage into a battery than what it's output is in order to charge it.
An 8.4v battery typically charges at ~9.6v, and around 11.0-11.5v for a 9.6v
And all NiMH batteries will get hot when charging, depending on how you set your delta peak (topping off the battery), they could be REALLY freaking hot.
There's nothing wrong with your charger.

[happykal]

@ JonsM4 It's an EV-650W Intelligent deluxe charger/discharger

@ Coachster: I agree I should have used my old thread to continue the discussion. my bad. The battery is a G&P intellect 9.6v 1600mah. the 8.4v 1200mah is I'm assuming ICS because it came with my mp5. Thanks for the advice on the charger.

@L473ncy Voltage is push,power,energy, force, drive however you want to put it. Amp is current, ohms is resistance. I retained the basic knowledge of electrical theory from when i studied my gas technician modules 6 yrs ago. Never understood why current is represented by I in ohm's law. My 9.6 peaked at 11.6 V. lmfao

well thank you every one for clearing up this misunderstanding. I finally have this thing figured out.

[bigbuzz666]

Originally Posted by happykal

Never understood why current is represented by I in ohm's law.

For what I remember from my electronics class 10 years ago, "I" stands for "Intensity of the flow", direct translation of the french term "Intensité du courant"...

[happykal]

Originally Posted by bigbuzz666

For what I remember from my electronics class 10 years ago, "I" stands for "Intensity of the flow", direct translation of the french term "Intensité du courant"...

Well, that makes sense. Another mystery solved.

[ILLusion]

Your only problem was that you set the charge current too high. 1600mA is too hot (IMHO) for a 1600mAh Ni-MH pack. Try half of that.

Lower is always better for your battery. It takes more time, but plan for that, and you'll have longer lasting batteries. I personally don't charge any of my batteries higher than 500mA. In some cases, I'll even do as low as 150.

[coach]

Originally Posted by ILLusion

I personally don't charge any of my batteries higher than 500mA. In some cases, I'll even do as low as 150.

150mA is pretty conservative but then again, it helps preserve batteries with an extremely low chance of even getting the slightest bit warm.

(or you do what I used to do with my old TLP charger and NiMH cells @1C or higher and build a cooling box with surplus computer fans hahaha)

[happykal]

Originally Posted by ILLusion

Your only problem was that you set the charge current too high. 1600mA is too hot (IMHO) for a 1600mAh Ni-MH pack. Try half of that.

Lower is always better for your battery. It takes more time, but plan for that, and you'll have longer lasting batteries. I personally don't charge any of my batteries higher than 500mA. In some cases, I'll even do as low as 150.

I charged the batteries at .5Amps (500ma) the 2nd time around. The first time i used it i charged at1.6amps. The battery was way to friken hot.

[kalnaren]

I charge my 1.6A batteries at 1.0A. From dead takes about 90-100 minutes. Battery gets warm but nowhere in the realm of hot.

The only batteries I charge at 1C are lipos.