I broke down and bought the Hobbico Quick field charger MKII, and an ESV with leads to match all of my JR and Hitec gear.

I read through the instructions and it is still unclear to me exactly how to quick charge a NiCd battery.
they dont say what Mah setting to use, it will charge from .02 Mah to 2.0 Mah.

These are the batteries I want to quick charge can someone tell me what settings to use?

4.8v 600 Mah RX bat.
9.6v 600/700 Mah TX bat.
1.2v 1200 Mah glow starter bat.

The instructions say to plug in the battery select the charge rate and push the yellow button once for nicad, it says when peack charge is complete it will switch to trickle charge for the last bit of charging.

How do I know its done other than taking the battery off and checking with the ESV?
Does it sound an alarm when done?
How fast can I charge my batteries at the field?

Is there some sort of referance guide that I can print out and keep in my flight box, or is there a formula to go by?


Anyone with experiance on the MKII? Ant help would be appreciated, thanks.

Charge rates are usually talked about in terms of "C". C is the capacity of the pack in mAh. Charge rates are measured in mA (note the lack of "h"). A 1C rate is a 1 hour rate, and a pretty fast charge. So, to charge a 600mAh pack at "1C", you charge at 600mA. 2C is 1200mA.

For most packs, C is a nice safe rate that gets it charged fairly quickly. Nicads can usually be charged faster, but you do reduce the lifespan of the pack by charging too fast. I usually won't charge my Nicads at the field faster than 2C, but I have gone up to 4C for a "need a charge RIGHT NOW" situation (at a competition, it was charge fast or "0" the round, I opted to charge fast and accept that the pack might not live to see the end of the season).

I'm not familiar with your particular charger. The ones I have have either an alarm or a light that does something to tell you when it goes from full charge to trickle.

A single 4C rate charge is probably not going to harm the battery pack enough to measure IF you don't overcharge. A good peak detecting charger will prevent the overcharge. (I bet you used one too. )

If the NiCd is manufactured for high rate charge/discharge, such as the RC car 7.2 volt power packs... then it will do fine at 4C rate for its expected life. These type cells typically don't last as many cycles as the type cells used in a TX or RX pack. So... the type of battery we are talking about matters.

That Hobbico charger should have an LED for the TX and one for the RX. When the LED is glowing bright... it is quick-charging. When it is flashing it is on the trickle rate for the settings. If it is off, nothing is happening.

***********

NEVER quick charge a hot battery and if it gets hot... get it off the charger. Hot battery plus fast charge = boom.

Fred, I was hoping you would show up on this one.
the batteries are JR and Futaba 4.8v and 9.6v standard 600 Mah.

Which C should I charge at" 1,2,3,4?

I am gathering that a C means double the Mah of the battery.
so 600 mah would be 1.2 @ 1C and so forth.
I think I am confusing myself even more.
Am I on the right track?

Fred would you take a look at my other post? I am having problems with a hitc TX, thanks.

For TX and RX batteries... you do want to stay at or below C rate. C EQUALS capacity... for a 600 mah pack C = 600 mah and C rate = 600 ma.

I generally "accelerated charge" (not a real term... I just made it up) at C/4 if I have the time for that but not the C/10 overnight rate.

Slower (up to a point...) is better. C/20 is about as low a rate as can be useful for anything. and not many people like a 24 hour charge time.[&:]

btw, you don't have to have even multiples either. I often charge at anywhere from 1.2 to 1.5 C on my RX packs (on a 500mah pack, anywhere from 600-750ma). Gets you done a litte faster than an hour, but less abuse on the packs.

As you can see, the rates aren't "fixed", the key is to avoid overheating or over charging the batteries.

"C" stands for Capacity.

OK getting a little clearer.
Would it be ok to charge my 600 mah packs at 2.0 a? If so how long could I expect it to take?

2.0 A rate is essentially 4C for a 600 mah pack... that is the extra-fast rate we have been saying to AVOID!

In a case of emergency recharge... then the 2.0 A rate would be a 20 min charge.... generally there is no emergency that warrants doing it. These things are not providing life-support for someone.

For RX ot TX packs rated 600 mah... you want to avoid charging at over 0.6 A rate. If you have a choice of 500 ma rate or 1.0 A rate... then go with 500 ma.

Sit back... yack with the other guys at the field... and wait an hour or two for the batteries to charge at 600 ma or 300 ma charge rate.... If you ever fly enough in one session to actually need to fast charge...

You can do the math on it:

battery capacity in mAh / charge rate in mA = hours to charge.

600mAh / 2000mA = .3 hrs, or 20min.

To calculate what multiple of "C" you are charging a:

charge current / battery capacity

2000mA / 600mah = 3.33, on the high side.

If you combine all that together, you can see that the rate expressed as a multiple of C is really the same as saying how much time it will take to give the pack a full charge. C is 1 hour, 4C is 15min(or 1/4hour), C/10 is 10 hours.

As FHH said, when given the choice between two rates, take the lower one, your batteries will thank you.

(btw, charging isn't 100% efficient, so a charge calcualted to be 1 hr long will actually take a little longer)

I have the same charger you have. I charge my 600 Mah batteries at 1 amp at the field. Takes about 30 minutes when the battery is not fully discharged. I usually recharge after about 4 flights. The charger will beep loudly when the battery is charged. It will then switch to a trickle charge and the light will continue to flash until you remove the battery or push the button again to stop the charging. I do this only for "quick" charging at the field. I always charge overnight with the wall wart before I go flying.

Is the assuming the battery is fully discharged? Say the safe voltage on the rx is 4.8 and you decide to charge when your at 4.8. It will be much less than if the battery were completely dead, right?

Yes... and that's one of the problems with high rate charges. You have a higher probability of overcharge. The peak detecting chargers help reduce the damage.... but don't prevent it completely.

well guys,
I'm sorry to say that despite your eforts to help a dummy, and before the last several posts. I went out and smoked the battery.

I put a 600mah battery on a 1.2A charge I thought this was 2C and a safe charge rate.
the first charge went ok about 15 minutes, the battery was partially charged already.

I took the plane up for about 10 minutes, landed and checked the voltage again this time it was still in the green, but a little low so I thought I would charge it up a little and go back up.

After 30 min with no beeps I checked it again with the ESV, and found that I had lost some voltage.

At that time I convinced myself that I had hooked the leads into the meter ports of the ESV and the simulated load for 30 min had drained some juice.

I hooked everything back up and tried again after a few minutes I heard some sizzeling coming from my plane I quickly started removing radio gear and when I got to the battery found that it was frying.

It was wrapped in about two inches of foam and got to hot. I guess Im lucky to still have a plane. Please take it easy on me I already know I'm an idiot. I am going to get some more help with charging before trying again.

Did I ruin my on off switch, is there any chance I damaged more than just the battery?

I'd replace the on/off switch to be safe, and be sure to do a range check before you try to fly with that receiver again, but it's likely that it's okay.

1.2 mA's IS 2C for the 600 mAH pack, and it should have been a safe charge, but as FH mentioned in his last post, a peak detect charger will reduce the likelyhood of an overcharge, but not prevent it.

Re-charging too soon was probably what caused your problem, because the closer the pack is to fully charged, the less likely the charger is to see the peak, and the less expensive the charger the more likely it will also be to miss the peak.

Sorry about your pack, but it was a relatively cheap lesson.
Dennis-

I think we forgot to mention something else too...

ANY fast charge heats the battery.

Without any airflow ... the battery can't cool off. The foam is a great insulator... like a thermal blanket. Keeps the batterys warm and toasty. (so they can fry easier.)

I never charge at above C/4 with the battery in the airplane.

I now never charge the TX battery while it is in the radio AT ALL! (I used to charge with the Wall-Wart leaving hte battery in the TX... had one vent. THAT was a mess.)

I bought the same charger a couple months ago. Fortunately I havn't fried a battery yet. Is it safe to say as long as you monitor the temp of the battery ever 2 or 3 minutes that it will be ok. I guess what I am asking is, it can't expload the battery unless it gets hot first, right?


Wings,

NiCd's won't explode, but as FH said they can "vent". Essentially expelling their contents and becoming useless. [&o]

But yes, monitoring temperature will help prevent damage.

I first bought the Hobbico Quick Field charger years ago and used it numerous times without any trouble. I've since bought and successfully the Hobbico (I think) 330 Peak charger, and now exclusively use a Super Nova.
Dennis-

Don't say they CAN'T explode... I've blown one pack apart. Fast-charged an RC car pack immediately after running the car HARD (so the pack was hot already) and the charger was of the old timer type. (a resistor and a timer-switch in a box with an amp meter Very common in the late 70's and early 80's for RC cars) The timer picked that charge to fail and at 20 min into a 5C rate charge the pack was swelling fast. We ducked and pieces of batteries were spread in a 20 ft radius.

You do have to REALLY abuse a pack to blow it up... but it can be done.

**********

typoed and typoed correcting the typo.

What should I do to prevent this from happening again?
I am a little scared to try this again, I just bought two JR 4.8v 600 Mah batterys.
I want these to last a little longer.

Another question on batteries, I noticed that the Batteries that came with my flight JR packs are shrink wrapped in black.
The ones I just bought are red, does this mean they are old stock?
They are new in the package, but is there a shelf life on them?
Say they are new never used but have benn sitting on the shelf for a while.
Are they still OK?

DB, The switch looks fine no melted wires.
I tested it out and it works fine. Do you think its okay to use until I can get a new one?
Am I just asking for trouble with this one?
If the RX range checks ok should I still be worried? After your post I am worried about sending this plane up with this radio gear[]

If you are really worried to use the switch just hook the battery straight to the RX untill you get a new switch. It may be a pain in the butt, but it will get you in the air.

I agree with wings, though your switch probibly is fine.

After all, you didn't do anything like short a wire that would cause the wire to get hot and melt, you just over charged the battery. Damage should be localized to the pack.

As for avoiding in the future, as you discovered, and FHH mentioned, there are two "don'ts" with fastcharging:

1) don't charge a warm pack, let it cool, and keep it cool during charging.
2) don't fast charge a nearly full pack, the peak detection of the charger may miss it, and you get a melt down. (what I think happened to you).

In the future, fast charge when you're battery is "empty" or close to it. If you want to field charge after just 1 flight, go slow, like well below "C". But for the most part, why bother charging when the pack is mostly full anyway? If a 4 cell RX pack reads over 4.8v, you don't need to charge unless you want to. If it reads 5.0v or higher, you probibly shouldn't fast charge it at all.

Btw, many fast chargers have a "discharge" function. If you really really want to fast charge a nearly full pack, put it on discarge first. Takes more time, but far better for the batteries than fast charging a nearly full pack.

Montague,

Thanks for the help. I am convinced that I just tried to quick charge a full battery.
I learned a good lesson, and the 20 bucks ( new battery and switch) should help me remember.
I think I got off easy At first I thought I didnt understand the charge settings that you guys were trying to explain to me. Now I realize what happened I really didnt need to charge that battery at all.

What is the absolute lowest you should let a 4.8v get before charging? I am very paroid. If mine gets to 4.9 or below I recharge. Am I being overly paranoid?


Wings

1.1v per cell, or 4.4v for a 4 cell pack is about the lowest you should go, though I've heard of going to 1.0v, or 4.0v. Certainly, at 4.8 you are still on the "flat" part of the discharge curve, but at 4.6 and 4.4 are you are at or over the cliff.

Now, you can actually go a fair bit lower with out damaging the cells, as long as none of them reach 0 before the others.

But you've lost useable power for your system around the 4.6-4.4 point, and many guys recharge at 4.8, which is fine. I'll fly a short flight on 4.8, if I know the pack and the model. At 4.7 or lower I recharge for sure.