Weird battery question

[Randy Powell]

OK, I admit it. I'm an idiot when it comes to batteries and such. I understand the basics, but am sometimes stumped by the weirdest stuff.

So I'm using a glow driver with a replaceable, sub-C sized battery. I been using a 1.2V, 1300mAh battery in it. They are Ni-Cads and probably due to my own stupidity, they don't tend to last all that long. I don't have a cycler and don't really allow them to run down enough before I've recharged them. So they tend to die early deaths.

I though, with the coming season, I would replace the batteries (I usually keep 3 of them re-charged for the field, one in the pipe and two in the box, just in case). My thought was to replace them with Nickel Metal Hydride batteries so as to avoid the charging issue. But all I've been able to find in this type of battery are 1.2v, 3500mAh. If I get these, will it be a problem? The voltage is the same, but the amps are quite a bit higher. Will this level of amperage blow out the plug?

It would be easier if Duracell would just sell alkaline batteries like this, but I haven't seen them either.

[Howard Rush]

The NiMH oughta work just fine.  The capacity difference will let it go longer between charges: about an hour's worth of plug lighting, compared to a little more than half that for the NiCad.  How hot the plug gets depends on voltage across the plug, which is a function of battery voltage and battery internal resistance.  

[Randy Powell]

Howard,

Well, that's what I thought, but as I said, sometimes I assume this stuff then find out that I'm not as bright as I thought.

Thanks.

[Garf]

I use mostly recycled Ni Cads from where I used to work. When the battery pack on their 2 way radios fail, they throw them out. Usually the batteries are fine, but the circuit board in the pack fries. I rip open the pack and test the batteries, then recycle the cells that are still OK. I've got 2 lifetimes supply of batteries. I still take 3 batteries to the field, because every so often, I catch a wire in a prop.

[Randy Powell]

Followup question: I assume I can use the same charger, it will just take longer to charge the batteries. Correct?

[Andrew Borgogna]

The Ni-MH is a perfect replacement for Ni-Cad the main reason is the come in higher capacity 3500mh compared to 1200mh and they don't have the memory issue that Ni-Cad's do.  If you have a charger intended to trickle charge a 1200mh Ni-Cad it should work just fine for charging a 3500mh Ni-MH. 
Andy

[Brett Buck]

OK, I admit it. I'm an idiot when it comes to batteries and such. I understand the basics, but am sometimes stumped by the weirdest stuff.

So I'm using a glow driver with a replaceable, sub-C sized battery. I been using a 1.2V, 1300mAh battery in it. They are Ni-Cads and probably due to my own stupidity, they don't tend to last all that long. I don't have a cycler and don't really allow them to run down enough before I've recharged them. So they tend to die early deaths.

    I am not sure why they would be dying earlier than anyone else's. I don't generally cycle mine, either, and they last plenty long enough. The only thing I do even a little bit different from anyone is that I don't regularly charge them. I can usually charge them at the start of the season, and they will stay good enough for the rest of the year. I usually take the one I think is the lowest SOC and charge it for 6-8 hours the night before Top 20 day but other than that there's not a lot to do. I think my oldest battery is about 10 years old, with maybe 25 cycles.

     Brett

[Mike Anderson]

Followup question: I assume I can use the same charger, it will just take longer to charge the batteries. Correct?

It will take longer if you are starting with a completely discharged cell (assuming your charger is limited in the current it can supply).  So if your charger is a 130 mah source, (C/10 for your 1300 mah cells), then you will need almost 3 times as long to charge a completely dead cell (3500 mah/ 1300 mah).

But once fully charged, if your normal usage is only 1000 mah - like 20 starts at 3 Amps for 60 sec. - then you only have to replace that 1000 mah, so your normal charge (overnight at 130 mah) would top off the cell.

[Peter Ferguson]

I had a glow plug ignitor that was killing nicads. Turned out it was dirty at the plug contacts which was providing a load and draining the batteries. Take the battery out and clean the contacts with electrical cleaner. You may have one that is draining the batteries. Keep the charge rate low if you go to the NIMh. They don't tolerate fast charging like Nicads do.

[Randy Powell]

According to the directions that came with the charger, you had to initially charge the batteries (1.2v, 1300mAh) for 24 hours before use. So I assume that a new, drained NiMH (1.2v, 3500mAh) battery would take as long as 72 hours to initially charge. I wish I had an indicator that showed, hey dummy, the battery is now charged!

[Clancy Arnold]

In reply # 5 above, Andrew Borgogna mentioned the "Memory Issue."

The "Memory Issue" is a function of the chemical makeup of the NiCad battery.  I have had dealings with them since they were first introduced over 30 years ago.

What happens is the battery, as built, has a specified capacity but if you only discharge them "Repeatedly" to a partial discharge they will develop a memory of that capacity and soon will only store that amount of energy.  The Memory can be removed by deep discharging them to about 1.0 volts, Recharging them and again deep discharging them again.  (This process may have to be done 3 or 4 times to save some batteries.)  Then they should accept a full or nearly full rated charge.

Recharging a NiCad battery with out fully discharging it, down to near 1.0 volts, is not good for the battery.  You need to rotate your NiCad batteries so that they get different loads and discharges each time.  That way they do not have a chance to develop a "Memory Issue."

Clancy

[Bob Reeves]

Hey guys hate to bust any bubbles but Ni-cads haven't had a memory problem for 15 years or longer. Yes the early ones did but when I left Motorola 15 years ago technology had eliminated the problem. The most common destroyer of Ni-cads is over charging.

[Mike Anderson]

At one time (early '90s) I had quite a lot of manufacturers literature from Panasonic, Sanyo, Varta and others -- EVERY ONE of those had a statement similar to:

"We have not been able to reproduce the phenomena known as 'battery memory' in any laboratory setup or experiment"

ONE of them, Sanyo I believe, had a reference to a very slightly depressed peak voltage on cells that were repeatedly discharged to some partial level, but capacity was not affected.

[Clancy Arnold]

My information is dated as I retired in 1990 but.

While working for the US Navy in Indianapolis, I was asked to look into a problem affecting the guard force.  They were buying extra Battery Packs but the problem did not go away. Their two way radios were going out just when they needed them the most.  That was when something unusual came up and the guards had to talk more than normal on their radios.  The battery packs were removed from the radios each night and placed in a charging rack.  Each battery had a user number on them so that each guard got "His" battery back with "his" radio.  I had them remove the tags from the battery packs and the were to issue the battery packs consecutively as they were in the charger rack.  We deep cycled the packs and in two weeks the problem was gone and the plant had an excess of battery packs.  There were very few battery packs that did not recover their proper capacity.  These were Motorola radios with Motorola NiCad battery packs but I do not remember who was the manufacturer of the NiCad cells in the battery packs, it was not Motorola.

I have NiCad cells in use that are over 20 years old and still work fine.  I care and feed them properly.   
Clancy

[Randy Powell]

I suspect it's good to have a system that discharges the battery then charges it.

[Paul Wood]

Randy,

NiMH will work just fine.  I use them all the time.  But FYI, a new NiMH needs about 5 charging/discharging cycles to fully "form" the cell.  I doubt that you will notice this if you're just using them for glow ignitors, but the more you use them the longer the maintain a charge.  And definitely slow charge.  Over charging at a low rate is not an issue, but fast charging at a high rate is a no-no.

Paul

[Warren Leadbeatter]

NiMh cells are typically higher in capacity but their self discharge rate is also higher compared to NiCd.  Self discharge will occur over 30 to 60 days making them useless for things like clocks and smoke detectors.

I have a 2700mAh NiMh D cell glo driver and I charge it the night before I go flying. It has never let me down yet.

Cheers

[Randy Powell]

I'm starting to think I'll just pick up one of those glow drivers that take a AA battery and buy one of those big packs of Duracells.

[Brett Buck]

Hey guys hate to bust any bubbles but Ni-cads haven't had a memory problem for 15 years or longer. Yes the early ones did but when I left Motorola 15 years ago technology had eliminated the problem. The most common destroyer of Ni-cads is over charging.

   And, importantly, for it to manifest itself, you had to repeat the same cycle darn near exactly over and over - which is where they found it. Some satellites are in orbits that repeat the same sun/eclipse schedule over and over, say, 50 minutes of sun, and then 40 minutes on the batteries, within seconds. As long as the load stayed the same, that creates a perfectly even charge/discharge cycle. Turn something new on, and at whatever depth of discharge it was used to, the power would drop. Discharging it all the way every so often cleared it out.

    This is all the good old days, 40 years ago stuff, only in aerospace-quality parts, not now.

   That doesn't mean that discharging them periodically doesn't do something. They do slowly lose capacity that can be restored to some extent by a complete discharge cycle. But it's not really a memory issue.

      Brett

[jim gilmore]

The number 1 killer of nicads is heat. often caused by over charging. I know this because I have done it enough.

[Jim Kraft]

Since I fly a lot of ign. planes, I bought a fast charger and 4 NIMH AA batteries at Walmart several years ago. This charger is only for NIMH batteries, and chargers them in 15 minutes or less. They are 2500 mah, and can also be used as a glow driver. The charger has a green and a red led to let you know when charging is complete. They do get rather hot when you take them off of the charger, and they only seem to last around 3 to 4 years. But the convenience, and current capability, are very nice.

[Don Hutchinson AMA5402]

There is a new Ni-MH cell by Sanyo called ENELOOP. They are AA size 2000 MAh cells that will retain the charge level seemingly forever. The package says cells will only lose 15% of their charge in 12 months. I have them in my ignition Dragon and they will provide a good spark after sitting for a year between VSC contests. Don't know if they come in other sizes but if they do would make a great glow driver.
Don

[Peter Ferguson]

"I'm starting to think I'll just pick up one of those glow drivers that take a AA battery and buy one of those big packs of Duracells."

Randy I have one word for you "Costco".

[schuang]

This is just my personal experience and opinion.  Nicad is the way to go for the glow driver.  The biggest problem for NiMH is self-discharging rate. It is at least 3 times higher than that of Nicad.  NiMH in general has higher capacity, but it has higher internal resistance comparing to Nicad, therefore the instant discharge current is somehow limited.  Also, the capacity over time is decaying so usage time is getting shorter.  Also, overcharging and heat can damage damage both Nicad and NiMH rapidly so be careful don't abuse them.

For the ultimate Nicad cell, pick Sanyo Sub-C rapid charge series.  It costs more, but not every brand created equal though.

Sean

[Randy Powell]

I've been looking at battery chargers. I was looking for something that will charge sub-c batteries with some sort of indicator or cut off when the thing is charged. I've found a few universal chargers (say they charge NiMH and NiCad batteries and all sizes listing AAA. AA, C, D, 9V etc) but don't specifically list sub-C. I suspect it wouldn't matter, but any thought a chargers?

[Paul Wood]

Randy,

Tower Hobbies carries more chargers than anyone else I've seen.  They list the specs in the "tech features" of the charger listings.  I would suggest you stay away from the ones that charge multiple cells/packs at the same time.  Those are expensive and really designed for the electric plane and car guys so they can keep multiple packs charging while using other packs.  As for the sub-C.  Isn't that just a smaller version of the full size C?  The capacity/voltage should not be any different than the full size C cell...I think.

Paul

[Perry Rose]

For my money it's the McDaniel NI-STARTER. Now made or owned by by Sonic-Tronics.

[Mike Anderson]

I've been looking at battery chargers. I was looking for something that will charge sub-c batteries with some sort of indicator or cut off when the thing is charged. I've found a few universal chargers (say they charge NiMH and NiCad batteries and all sizes listing AAA. AA, C, D, 9V etc) but don't specifically list sub-C. I suspect it wouldn't matter, but any thought a chargers?

If they auto-cutoff when the charge state is full, then in "NICAD" mode they monitor for the voltage across the cell(s) to come to a peak and then start to drop - at this point the cell is fully charged and the charger will cutoff.  You want to look for a charger that will "auto peak detect" or a "delta peak detection cutoff" charger.  Single cells are more difficult to sense that peak, because the voltage drop after the peak is much smaller than with 6 or 7 cells in series, but there are chargers that specifically mention single cell or glow-starter ability.  I currently use a charger for LiPo's that has a nicad mode and I tried it on my cordless drill - the only nicads I have left in the house - and it worked pretty well for that, which is a 6 cell "1/2 Sub-C" probably about 800 mah pack.

The charger doesn't know or care what the capacity of the cells you plug into is - it will charge at whatever current level you set until it sees that peak/drop in the voltage level.

I don't know what the charge profile is for NiMH cells but the few I've used I treated like Nicads and kept the charge level to about 1C (or the 1-hour charge rate) where the old "Rapid Discharge" NiCads were happy to accept charge levels of 8-10C (6-8 MINUTE charge rate).


As for the capacity, sub-C's used to be 1300 - 1500 mah and (full) C-cells were 1800-2000.  I am not sure what the presently available sizes are

[Glen Wearden]

I bought 4 Energizer Lithium AA batteries from Batteries Plus.  They connected the batteries and put them together in a pack with a heat shrink wrap and two leads sticking out.  All I do is attach the two wires from my glo plug connector, and I have a full 1.5 volts that will last a long time.  I've used the set up for a full season of RC and CL flying, and am still using it with no apparent loss in ability to really light up the plugs.  No charger, no problems.  The whole rig cost me about $15.  It was in the shop all last summer and winter and is still going strong.

Glen Wearden

[Brett Buck]

I bought 4 Energizer Lithium AA batteries from Batteries Plus.  They connected the batteries and put them together in a pack with a heat shrink wrap and two leads sticking out.  All I do is attach the two wires from my glo plug connector, and I have a full 1.5 volts that will last a long time.  I've used the set up for a full season of RC and CL flying, and am still using it with no apparent loss in ability to really light up the plugs.  No charger, no problems.  The whole rig cost me about $15.  It was in the shop all last summer and winter and is still going strong.

 If you don't mind carrying it around, and the wire, this is an excellent solution, and can be very inexpensive. Just wait for a blowout sale on the cheapest off-brand alkaline D cells you can find. It's a very hot power source, too - you'll get a full volt and a half or so for years.

   The only advantage of nicads (and I use the McDaniel/Sonictronics short orange jobbies like everybody else) is the size/convenience. They aren't generally better or less expensive just because they are rechargable. Not when you can get an 8-pack of alkaline D-cells for $2 if you are a careful shopper. I also don't like having the wires around to go into the prop, but it's arguable if that's a bigger problem than the battery shaking off and going into the prop.

   BTW the old square Cox starting set battery was 4 of the cheapest possible D cells wired in parallel, with the terminals, and a box to cover up the truth!

     Brett

[Randy Powell]

I found a fairly inexpensive charger with an LCD readout. Says it will peak charge and switch to trickle or can be set to shut off when charged (it also cycles Ni-Cads so I support that's a plus). One less headache, I suppose.

Unlike Brett, I mostly use a starting box with a 12volt battery and power panel except when in competition. I like being able to dump the glow starter, flip stick and tach in my pocket then go out to the handle when flying official.

[Brett Buck]

Unlike Brett, I mostly use a starting box with a 12volt battery and power panel except when in competition.

  Right, but you don't have to haul 4-5 of them cross-country twice a year!

     Brett

[Mark Scarborough]

Randy,
just get an Rcats ignitor, and forget about it!

[Randy Powell]

Mark,

Way too upscale for me. Only you high tech types use those.