Albatross

My Feedback: (7)

I will replace an 1800 mA NiCd pack by a 2000 mA NiMH battery pack on the ignition of my ZDZ50.
Before proceeding with this substitution I wanted to know your experience about it. The receiver of my plane and transmitter have been working fine with the NiMH batteries. For the ignition system I installed a 1800 mA NiCd pack which has been working fine so far as well.

Are the NiMH batteries good choice to supply power to the gas engine ignition systems?

gunny11

My Feedback: (6)

Hi, I switched to a 5 cell 1500 mAh nicad pack and used a 5.2 voltage regulator on my ZDZ. I can fly all day without quick charging the ignition pack. As far as the Nickel metal hydried, I'm not sure what the impeedence is. I use NoBS Batteries. His ignition pack 1500's have low impeedence (which is what you want). Give Steve a call at www.hangtimes.com and tell him you want and he also sells the voltage regulator.

He has sold this to more than one ZDZ owner and the people just love this combination.

Hangtimes hobbies tel. # (631) 610-5169

gunny

Albatross

My Feedback: (7)

Thanks for the advice, I will consider this option.
As far as the Nickel-Metal hydride batteries go, I think they are good for the radio; however seems to be to me that someone in this forum motioned something against using this type of batteries to supply power to the ignition, I can't find that post.
What might be the internal impedance suitable for ignition applications?
Anyone else has installed Nickel-Metal Hydride batteries on the ignition system?

Geistware

My Feedback: (16)

At lower loads, the NiMH are better. As the loads increase and capacity being the same, the NiCad can supply high currents longer than the NiMH chemistry. I have not done the test to see where the crossover point is, and Red may be able to shead more light on this but I know at 1 amp loads, my 2700maH pack can only supply 1600maH before the current drops below 1 amp or the voltage drops below 1.1 volt per cell.

SLINGSHOT-RCU

I run a 4.8 2000 nimh on my zdz160 with no problem. and on my da100 i run a duralite with a 5.1 reg.

Albatross

My Feedback: (7)

I don't know the average current consumption at any given time for the ignition system; however a very rough estimation based on the information from SLINGSHOT-RCU tells me that my ZDZ50 should be happy for a long flying session, more likely next summer.
In effect with my 1800 ma NiCd I am used to fly without recharging "all they long" (meaning all day long up to 4-5 flights) or at least flying with the peace of mind that I should be OK. This is exactly what I expect to see from a 2000 mA Ni-Metal Hydride pack.

Geistware

My Feedback: (16)

I have a 2700maH pack on my engine and usually get over 12-15 flights from it before recharging. I am using it on a BME 100

greenboot

My Feedback: (1)

I'm always surprised to see people spend big bucks on carbon to save a few ounces, then install the biggest battery they can find to avoid charging. What's the world coming to? I have an 1100 mAh NiMh in my ZDZ80 and it makes 5 flights with lots to spare.

Tom

tkg

My Feedback: (1)

Not our ignition but, we have used Nimh batteries with capicity as small as 700mah with out any problem. More than 1 hr flying time. We did have some high speed missing when using smaller 300mah packs, I guess they could not handle the current surges. Most ignitions don't have a smooth current draw, but rather take a BIG gulp, trying to charge the HV cap, just after the ignition fires. The smaller Nimh just didn't seem to be up to the current load and would limit the spark at high RPM.
Our personel choice is a 1650 Nimh 4.8v pack. They are AA size and will last 3+hrs.
BUT never add usless lead to a plane, just use a bigger battery and get some benefit from the weight.

Albatross

My Feedback: (7)

Very useful information, I wish I could know the right battery size for each giant RC application, knowing this factor would save some weight and also some money. I am definitely against overweighted planes. As a matter of fact switching to Ni-Mh batteries was one step toward reducing some weight on my plane; of course I started with the aluminum LG which is 13 1/2 Oz. Along with this I decided to move to a lighter power source for the ignition; my 1800 ma Nicd pack is 7 Oz. Now the new carbon LG is 8 1/2, the new Nimh battery pack weighs 4 Oz (2000 mA NiMh Hydramax). I think this combo is still a winer.

Unfortunately for an any given airplane the weight reduction is not a linear function of the cost. For instance you might have to include composites during the building process, lighter engines, lighter pipes, landing gears etc. Now I know that is not neccesary true, at least for the ignition battery since a 1650 mA (or 1100) might have very well done the job at less cost and more likely a bit lighter than the 2000 mA NiMh.

For the sake of simplicity, the fact of not needing any additional equipment support to recharge batteries on the field is very beneficial. I see my fellows flying glow engine powered planes carrying tools, starters, battery chargers, expending $13 plus for a gallon of fuel, etc

I only need a pair of allen wrenches, my globes a can of premixed fuel and I am ready to go!
That's part of the joy of flying planes powered by gas engines!

tkg

My Feedback: (1)

Think of Nimh's as a poor mans li-pos. Their cost/benefit ratio is very good.

ptgarcia

My Feedback: (36)

I use 1650mAh 4.8v NiMH batteries on the ignition of all my 50cc gassers. My packs weigh 4-oz and cost $15 bucks or so. I get them from [link=http://radicalrc.secure-mall.com/shop/index.php?shop=1&cat=19&cart=230570]Radical RC[/link]. I can get 5 flights before recharging. I may be able to get more but thats about all I get in during the day, and I recharge after each day of flying.

rmh

FWIW- the latest batteries used by the hot wind electrics, deliver very well for entire pack charge.
Check with your favorite dealer on the stuff such as KANN cells / Sanyo high discharge types ,etc..
even sub 1000 ma cells deliver like crazy.--and can be blast charged at the field.
I flew my Harrier on 950 ma 5 cell KANN radio pack - amazing batteries.

Hangtime

My Feedback: (19)

Hi Gents!

On some ignition modules there seems to be direct relationship between how hot the spark is relative to the voltage of the pack under load. In Gunny's situation we found that a 4 cell Sub-C sized nicad pack under his ignition load would stop providing a hot spark when the pack was still in the top 25% of it's discharge curve. Despite the fact he still had better than 75% of the packs capacity remaining the partiall discharged 4 cell system wouldn't provide a hot enuff spark to light his engine. We 'fixed' it by switching to a similar capacity but physically smaller and lighter 5 cell pack and a 5.4v regulator. This moderated the voltage down on the 6.0v pack to a the same voltage a freshly charged 4 cell runs at and he was able to use the entire capacity of the smaller pack and thus keep the engine running much longer between recharges... all while providing a big net savings in weight over the heavy 4 cell sub-c system.

NiMH systems, particularly the new High Rate KAN's have impedance values that are certainly suitable for ignition systems; however the NiMH packs don't like being discharged to zero under a load.. something that's not infrequent in an ignition system; I've more than once forgotten to switch the system off and inadverdantly dumped the ignition pack flat. More often than not, with a NiMH pack this does unrecoverable damage to the cells, whereas with a Nicad ignition pack in reasonable shape the pack will usually recover with some TLC (slow charge and cycle recovery testing). Other percieved drawbacks to NiMH in ignition applications are relative to the performance of the cells at high temperatures (engine or exhaust proximity issues) and the somewhat more delicate nature of the cells when faced with constant fast charging, and in particular fast charging a 'hot' NiMH pack.

The advantages to NiMH these days are less relevant with regards to weight or suitability for the moderate ignition loads.. most folks like 'em because they pack more capacity when compared to similar size and weight nicads. As long as folks get 'em installed where they won't be subjected to significant operating temperature issues and don't let them over-discharge or cook 'em with incorrectly set up fast chargers the reports from the field have been pretty good. With regards to overall duty cycle lifetimes and overall reliability in ultra rugged enviornments, Nicad still rules the roost.

Hope this helps..