Tech Question regarding ni-cad glow ignitors.

[frank carlisle]

I've always left my ni-cads stewing overnight on the charger and I've always had a good charge. The thought came to mind today that the batteries might be taking a full charge in less time. So----the question is: How long does it take for a ni-cad glow ignitor to reach a full charge?

[Clancy Arnold]

Frank
It would depend on the size and type of battery in the unit.

If you charge them over night and they are not warm when you disconnect them from the charger then they are not being hurt leaving them on charge overnight.  The best charge rate for nicads is 1/10 rated power.  If the Battery is a 600 mAH then they should be charged at 60 mA for 14 hours.  The additional 4 hours is required because of the charging efficiency.

You can charge them faster but you or the charger has to monitor the cell voltage constantly.

Clancy

[Garf]

From completely dead, 1/10 of its ampere hour capacity, in ma, for 14 hours. 2000mah=200ma for 14 hrs. Anything else is guesswork.

[Randy Powell]

I recently picked up a charger that charges Ni-Cads until they reach peak charge then trickles after that. Pretty cool, actually.

[frank carlisle]

I'm trying not to think here guys. Here is a picture of the batteries I'm talking about. I'd specifically like to have just the amount of time they take to reach a full charge from dead flat to full capacity using the charger that comes in the package along with the battery.

[Dennis Moritz]

I have used and abused nicad igniters for the last six years. Charging them up sporadically and unsystematically. There are always two or three of them in my flight box. Every few months I put them on charge overnight. All still hold a charge and glow the plug. Which means at least one is six years old. The only one I had fail had a spring release. It was the spring release that failed not the battery. The twist off igniters are fine.

[Tim Wescott]

I'm trying not to think here guys. Here is a picture of the batteries I'm talking about. I'd specifically like to have just the amount of time they take to reach a full charge from dead flat to full capacity using the charger that comes in the package along with the battery.

Well, without knowing what the charger that comes with the package does, that's kinda hard.  _If_ the charger charges at C/10, then 14 hours, or a good long overnight charge.  If you're not drawing them down to nothing, then 8 hours should be fine.

I've been using one Ni-starter for about five years of light use coupled with abusive charging practices, and it still works fine (but then, I probably only start a plane with it four or five times when I'm at the flying field).

[Neal Beekman]

I find the best charger is from Hughes R/C .Visit www.hughesrc.com for all the information.

[Brett Buck]

Frank
It would depend on the size and type of battery in the unit.

If you charge them over night and they are not warm when you disconnect them from the charger then they are not being hurt leaving them on charge overnight.  The best charge rate for nicads is 1/10 rated power. 

   I would not call it "best". C/10 is generally accepted as a reasonably safe overcharge rate, meaning you can leave it at that rate for a long time without causing excess damage due to overheating. Note the many weasel-words!  The actual charge rate you get from the supplied charger is pretty highly variable as is the actual capacity of the cells.

    To really charge them optimally, you need to keep track of it a lot better than we are going to, like, integrate the amp-hours out , then charge it to something like 115% of the capacity by integrating the charge current. Of course you also need to calibrate the total capacity, and to calibrate the overcharge ratio. The current is not critical - many nicads can be charged very safely at 10 or 20C as long as you don't overcharge them. Of course at 20C (the equivalent of about 20-24 amps for a McDaniel starter!) your tolerance for overcharging is nil, and if you leave it on 10 seconds too long it rapidly overheats and vents out the electrolyte, or any number of other bad things. And some of them *can't * take high charge rates, depending on the brand, and you really have no idea what brand you have nor what it's capabilities might be. Nor are they very repeatable.

    Mc Daniel claims that they are chargeable at 4C as long as you are careful and start with the cell in a known state.

     I think the C/10 should be pretty OK as long as you don't just leave them on continuously and only charge them when they  show signs of being depleted. If you overcharge them for times on the orders of hours it will be safe enough. I don't think it's a good idea to charge them continuously or for overnight before every flying session, but it's arguable if that is going to make them crap out from cell failure before something else causes it to fail. And the some individual batteries will just die early anyway and others will last forever, because the quality control/repeatability is at best "consumer grade".   That fact alone makes it just about impossible to make any strong definitive statements about the perfect methods - all the variables are very poorly controlled.

    Brett

[Clancy Arnold]

Frank
If you still are wondering, then get a remote NiCad starter connector.  Wire a light bulb across it and then before charging your glow plug battery plug in the light bulb.  when the bulb starts to dim the battery is effectively discharged and is now ready for a full charge at 1/10 C for 14 hours.

Clancy

[frank carlisle]

I had the batteries charging when I first posed the question. I ran them down by connecting them to a glow plug. I let them rest an hour or so then charged then overnight. They worked fine today. I rarely discharge them deliberately and just wait till they won't light up the engine before putting them on the charger overnight. I guess I'll keep doing it that way. From Brett's comments I gather that it's a crap shoot anyway.

[Brett Buck]

I had the batteries charging when I first posed the question. I ran them down by connecting them to a glow plug. I let them rest an hour or so then charged then overnight. They worked fine today. I rarely discharge them deliberately and just wait till they won't light up the engine before putting them on the charger overnight. I guess I'll keep doing it that way. From Brett's comments I gather that it's a crap shoot anyway.

   
   Sort of, but fortunately ni-cads are pretty tolerant, much more than a lot of more exotic types. I carry 3 of them, and when one runs down I will just grab another and charge the weak one. If it looks even a little weak, it's almost dead - one of the key characteristics of a ni-cad is that they put out a constant voltage until they are just about dead flat, even under load. That's why its not possible to tell the state of charge by just measuring it. and indirectly why they are prone to getting overcharged.

     Brett

     

     

[frank carlisle]

I left with the two I charged last night and flew a bunch of flights today in Lansing. I made sure to use the same one and keep the other as a back up. I just needed the one. I'll use it till it quits lighting up the plug. One nice thing is---my engines and tanks are well juiced from flying often and they start quick so the batteries are only in use for about 15 seconds at a time.
Are you related to Alan Buck?