50+AirYears

I know, it's old fashioned non-2.4 GHz radio, but it is working just fine and there is absolutely no reason to pitch the system. I had to replace the radio in a Venom Island Hopper, so I used one of the Tower 5 ch recievers on 72 MHz, the one with an on-board brushed ESC. The original 9.6 V battery that came with the plane is going flat, so I would like to try modifying the plane's battery compartment to use LiPo. I no longer have the paperwork for the reciever, but I seem to remember they listed a 10.0 V operating max for this system. Does anybody know if this system can be safely operated on the nominal 11.1 V from a 3S Lipo? Some years ago I had a similar question on Futaba's MCR-4A, and was told in no uncertain terms that 8.4V was an absolute, when I had wanted to go with a 9.6 V pack. I am not a smoker, so I don't want to smoke a perfectly good reciever.

Zor

50+AirYears,

Someone may feel differently but the 11.1 volts is a reference for 3 lipos in series.

In reality the voltage is higher than that particularly when the battery pack is full or nearly full charge.
You are looking more something like 12 to 13 volts.

I would suggest you go for a 2S pack that will run in the 8 to 8.5 volts range.

I am using some NiMH packs and I just measured two different packs 6S referred to as 7.2 volts.
They were fully charge a week ago today and one just measured 8.2 and the other 8.3 volts.

Lipos behave similarly.

Anyone who thinks I am wrong or has a better idea can of course give better advice.

Zor

50+AirYears

Thanks, Zor. That's the kind of thing I was thinking in terms of. Most references to battery Voltage are about a nominal Voltage, not peak. Like a 12 V car battery will often measure close to 14 Volts when the car is first shut off after an exended trip. I was thinking I remembered that the Electrifly 5 had a maximum rating of something like 10 V, while the plane in question originally operated on 9.6 V. That would give a peak after charge around 11.2-11.5 V. I worked a long time around electrical circuits, some of which had a maximum rating of say 5.2 and could take 6.0 or more Volts, while others with the same rating would release the internal smoke at 5.21 V. I worked in automotive electronics, and our 12 V circuits were designed around a nominal 12 V, but by design would maintain normal operation to something over 16.0 V, even though most 12 V charging systems were regulated to no more than about 14.2 V. We could also survive short term transients of over 1 KV, and static electricity of at least 12 KV. I was just hoping to find out the Electrifly unit had something similar to this kind of margin built in.

Zor

50+AirYears,

Based on your memory of that 10 volts max rating and if you feel that a 2S is not quite enough you can always add in series a single cell of NiMH giving you an additonal 1.5 volts or so (referred to a 1.2 v). This cell should have a mah equal or higher than the lipos.

Electrical circuits are dumb, they do not know what is pushing the electrons around. LOL.

Zor

50+AirYears

Yep, all they know is that they are either getting none, too little, just right, or too much, in which case they have to let the magic smoke out and stop working.

Zor

Zor

50+AirYears,

I hope you did not find my previous posting offensive.

I found this smiley with the light bulb showing, in my viewpoint, an enlightment.

I though your previous posting is very well written and entertaining and enlightening.

Zor

50+AirYears

Not at all, Zor. It fits right in with my sense of humor. It was actually mentioned in a couple performance reviews at work over the years. Matches the exact response I got out of a project engineer once. He was getting very stressed out. Typical in today's work environment, wher the lower you are on the management totem pole, the more work you are expected to do with fewer resources. He had a deadline to finish a report on a design, and was waiting for me to finish the testing and file a report on the results. I figured he needed something to break the tension, so I wrote the first draft in Portuguese (not great Portuguese, but readable!) and handed it to him as he was walking down to the print room to get some documents. He actually walked over 100' down the hallway reading the report, stopped, looked around, just like that emoticon, then suddenly got it, shook his fist at me, and broke down laughing. He was relaxed for at least a couple weeks after that. Finally quit and went into business for himself. Less stress and fewer working hours.

Byt the time he got back to his desk, I had the English language translation ready and waiting for him. He was still laughing as he threw the original at me.