NiMH Battery for RX, the achilles heel of your model
 

Not really a beginner post but new modeler should know and could gain from some of the responses.

This weekend I was all set to participate in a contest. I charged my rx battery (hydrimax NiMH 1600m, 4.8V) for 11 hours at 0.2A Thursday night. It ended then trickle charged. My TritonEQ charger put 840ma in the battery. When I got to the contest field Friday, I did a range check, then I checked my battery again. 4.44 volts:( So I hooked it up to my quick charger run off of my 12V car battery set at 0.6A. After an hour, I discovered I had a frayed negative charge lead:( I borrowed another pair of leads and charged it at 0.6 for another hour and a half. Still 4.44 volts. Did not fly.

When I got home, I put on a new out of package battery I purchased in Feb that I was going to use for another model. 2000ma 4.8V NiMH., charged at 0.2A for 13 hours. The next morning it had put 1730ma in, but when I check with my meter it was 4.56V. No fly for me.

I put the 1600ma battery on tritoneq charger again, 0.2A, completed charge and meter read 4.67 volts, still not flight worthy.

I either have extremely bad luck with batteries, a bad charger, or a bad meter.
I have some trusty old nicad 4.8V 700ma n charger now. If they don't charge I'll have my answer. They did read 4.9 on the meter.

Battery 1 was about 4 years old Had 8 discharge cycles on it and was always charged at either 0.2A at home or 0.6A at the field. Battery two was 4 months old but never used.

I guess my point is, check your batteries often. I would have lost my favorite model if I had tried "just one flight" on these packs. Don't risk your model, yourself, others. If you have a doubt about your batteries, don't fly. Not worth it. Dumb thumbing a model is one thing, a preventable mishap shouldn't happen.

I used NiMH for years mostly bought from Overlander.

I used to fly a LOT and on my 3D hacks would often have 6 or 7 flights.

On my small packs used for pylon and combat I replaced them every three years. On the larger ones every 4. I always cycled them once at the beginning of the season.

I can only ever recall one RX pack going bad on me and that was in a Zagi and I had forgotten to change it. It was 9 years old when it failed.

I have always used 6V NiMh packs (to avoid brownouts issues with 4.8V packs and some of the older DSM2 receivers I have), and my charger put them around 8+ volts fully charged last time I checked. That said, I've never been a fan of low mah packs, and only run higher capacity 2400mah packs.

I never trusted any of my NiCad batteries and that has carried forward to my NiMH. I always check at the pre-flight.

But I have to say I have had very good luck with 1450 and 2000 mAh HydriMax packs. I double cycle all of my battery packs a couple times a year. My most flown models I keep on wall-wart chargers on a timer equipped powerstrip and give then an hour of charge every day.

Unfortunately, I've had the opposite luck with Hydrimax packs. They went bad in a hurry.

I'm in the process of moving over to eneloop packs. http://www.electrodynam.com/store/eneloop.html

I'm going to check all the packs on a new meter. That will tell me if I have a bad meter. My old nicad on a wall wart only read 4.74 this morning after 18 hours. It went down?

At this point I'm also about to scrap all the stuff (charger, meter, rx packs) and just start fresh with LiFe or eneloops.

When I had a bunch of battery packs fail, in a short period, I checked my charger. It was at fault. The batteries were fine.

Yeah I'm taking 4 packs (1600ma, 2000ma NImh and 2 700 ma nicad) to the hobby shop tonight. I'm thinking meter. That or charge leads (again). They are the only common links now.

So tell me about LiFe? Look pretty good, no muss no fuss.

LiFe looks to be a great alternative to NiMH.

6.6v so you don't need a voltage regulator and great life and a self-discharge in storage somewhere between NiMH and LiPo. Downside is they cost another 50% over NiMH.

I'll probably be switching over my gas and glow models to LiFe through attrition when my NiMH packs peeter out.

IMO NiMh batteries are pure crap...terrible calendar life, terrible self-discharge issues and the rated "capacity" often does not translate into longer flight times. Frankly, you're better off IMO sticking with NiCad batteries, just remember to discharge them before re-charging. Total solution? A123 systems Life P04 batteries

I have had a lot of trouble with NiMh, as well. Especially once I moved over to 2.4 when it came out. I am now moving all of my battery needs over to A123, after switching to the Eneloop packs. The Hydramax gave me the most trouble. Too much internal resistance.

I have had good luck with Hydrimax packs but know two club members who have not. Could be the treatment of their packs or could be I am really lucky. I have two planes using Lipo and one using Life. I like many things about these but I DO NOT charge them in the plane. On some of my smaller glow powered stuff it just does not seem worth the hassle of pulling the packs after each session.

David

I have used a couple of Life hobbico packs on my receivers including 1 Pattern plane. Not running a voltage regulator. If memory serves me correct they were the 1100mah. packs. They weigh 3 ounces. instead of four ounces for a 600mah 4.8v Nicd. can't remember what the Nimh batteries weighed. Have not had any problem at all with them.
I did have to buy a different charger to charge them. I tried the hobbico charger for the life's but did not trust it.

Dennis I was about 5 seconds from fueling the Venus when I checked the batts. Would have been a shame to watch it fly away...

ACE RC used to be the leader in battery maintenance technology with a wide variety of chargers for NICADs/NIMHs. Do a goggle search and you can download their technical papers. I'm still using these batteries for both fixed and rotary wing models. One last though to be aware of is that these batteries are not all alike just like servo leads. With the advent of the Chinese clones we are being flooded with inferior products.

Can you elaborate on why you are switching from the eneloop packs ?

I have two packs, now, which I haven't yet used, but I am getting ready to purchase more.

What do you think of them for use in a TX ?

Best choice
TX- eneloops
Rx-A123
Plane power- Lipo

All you need to know right here. www.hangtimes.com I switched to the A123 cells and what a difference. Set it and forget it. Charge today and fly next week still just as good. I had 2 hydramax packs go bad on me and when I ripped of the shrink wrap I found a piece of foil thin metal connecting the cells and it was broken in two. Good thing I was using them for ignition and not the radio.

Same with me. There are other brands besides eneloops but I really found a good deal on line. For some reason the Hydramax didn't last very long at all? About a year was all the use I got out of them.

That would have been a shame forgot all about the ketchup until you mentioned the Venus. Glad it is still flying good for you. Only thing about a LiFe is make sure you can get to the balance leads for charging. my Pattern Plane is real easy to remove the battery, my sport plane it is buried in the plane and cannot remove it for charging.

Just looked and i am using the hobbico LiFe 1300mah pack. The Hobbico part # is HCAM6411 Tower is out of them at this time. but maybe the Hobby store by you may have them. If not try Prop Shop Hobbies in Warren he has everything. Just don't forget about using a charger for them. I still use some nimh packs but have gotten away from most of them, have had problems during charging and corroding. they are just dirty nasty things.

I fly mostly .40-to-.60-size sport planes, and I find that the 6V NiMH receiver packs work well for me. I've been buying a fair number of the 1600Mah Duratrax packs from Tower to use with my airplane receivers. When I first switched to 2.4Ghz, I used the regular old 4.8V 600Mah NiCd receiver packs I'd been using with 72Mhz radio systems. My Airtronics RDS8000 and my 92824 receivers worked flawlessly at 4.8v.

The price of 6V NiMH packs has gotten so low, however, I've been buying them instead. The Duratrax packs are $14.99 before any discounts, which is cheaper than many of the 4.8v 600Mah NiCD packs that are available from Tower.

These batteries can't reliably provide enough current for high-torque or digital servos in any kind of elaborate setup. I'm happy with them because I'm flying them in planes with 4 or 5 standard sport servos. I can show up at the flying field, top up the receiver pack with my Quick Field Charger II, and I'm ready to fly all day.

I still have to top up the batteries before I fly with them, even if they've sat for just a few days. NiMH packs just self-discharge too rapidly to be counted on unless you've just topped them up. Other than that characteristic, I find them to be cheap and reliable.

That having been said, I regard my receiver and receiver battery as the most important components of my aircraft. If I were working on a project with high torque or digital servos, or an aircraft with 7 or 8 servos in use, I wouldn't hesitate to spend the little bit of extra money required for a top quality battery, heavy duty servo leads, and a heavy duty power switch for my aircraft.

Like most purchases in this hobby, it usually boils down to picking the right part for the project in question. Smaller NiMH receiver packs aren't necessarily a bad choice, but there are plenty of applications where they aren't the right fit.

I had poor luck with the Hydromax nimhs. As GB said they are only good for about one season. One thing I noticed is that the self discharge rate seemed to increase dramatically after that first year. I had better luck with the Duratrax Nimhs at about half the price.
I think also these Nimhs set on the shelf for an extended period of time before they are sold since not many people are using them so they are already on a downhill slide.
I am now out of the Nimh business and have switched to Life batteries. You can charge them fast and if you don't get to fly for some reason they will be ready for use tomorrow, or next week, or even next month. They really hold their charge.

I have used the 4.8V and 6.0V Hydrimax NimH for years with no issues ever. I charge them overnight in the plane with the wall charger from my old Futaba 7CAP radio. As long as I use them a few times each month they are fine but If they lay around unused for several months they will self discharge and die.

I monitor the voltage before I leave for the field, before I fly, and maybe even after I fly.

+1 on the LiFe batteries. They are well worth their money. One thing to watch out for is the extra voltage - receiver and servos need to be rated for this, or you might burn them up sooner or later.
Most newer systems can handle the voltage, for everything else you can use a voltage regulator.

Yeah, some people just hook it up and 'never had any problems', under high load conditions you might loose a plane, not worth the risk.