Transmitter Batteries

[redboat219]

What batteries do you often use in your transmitter, alkalines or rechargables like Nimh/Nicads/Li-pos?

[trout]

I have been using these and like them so far:

http://www.horizonbattery.com/batteries/rechargeable-batteries/ansmann-2850-mah-aa-rechargeable-batteries-4-pk.html

[Subculture]

I use Lithium Ion batteries, the type used for mobile computing, radios etc. They can be run down to 2.5 volt per cell without damage, unlike lipo, so are compatible with my TX's low voltage alarm. I use a pack made up of three cells, which gives me 10.8 volts, which the TX takes in it's stride.

Other batteries good for TX's are LiFE A123, and the low self discharge NiMH batteries (e.g. Sanyo eneloop), as they can sit for months and hold their charge, unlinke conventional NiMH batteries.

[greenman407]

I went the Rechargeable battery route before on AA size batterys. By the time you buy the charger and the batterys your in for a pretty good amount. You also have to wait for them to charge and in the back of your mind you know that they are 1.2 volts instead of 1.5 volts. However, Home Depot sells a 48 pack of AA Energizers for $12.99. At that price, after you have used them for a while, if there is any doubt in your mind, just throw them out and put in a new set. No waiting.

[KevinMc]

My preference has always been to use NiMh packs in transmitters. They have better energy density than NiCd but still retain the "right" voltage/cell and form factor to pack in the most capacity in the available battery compartment space and you don't foul up your transmitter's low voltage warning and can still use the same "wall wart" charger that came with your Tx. If anyone's heading off the to Weak Signal's show in Toledo have a peek at the Batteries America booth (assuming they're still there) and look for their 1650mAh transmitter packs. They have larger capacity ones, but I've found the 1650's to be the best "bang for the buck" and I can go at least an entire day without flattening one even in my 9ZAP.

(@Andy - I still have to try out the eneloop cells. They sound like a great idea, I've just not committed the time to tracking them down. It'll happen though, I swear!)

[trout]

I do not work for this company, but I have ordered from them for work and home.
Here are some of the low self discharge batteries:

http://www.horizonbattery.com/batteries/rechargeable-batteries/max-e-low-self-discharge-1.html

Mark, I did the other way around. I bought regular batteries and went to rechargeable. I was burning through set of batteries (8) in a week's time, it was getting costly in the long run. So I turned tree hugger..... makes me want to buy some Birkenstocks, tie dye shirt, and ....... :-)

[redboat219]

How many mAh rating for rechargeables would you recommend.

[trout]

Kevin explained it this way: "You could think of the fuse rating like the maximum safe speed a car is allowed to travel at, your battery capacity then becomes the size of the gas tank. A bigger gas tank (battery) would allow you to drive for a longer period of time without affecting how fast you may drive. "
So the higher mAh the longer you can run. I believe Kevin likes the 2100 mAh, I apparently went for the biggest gas tank - in hindsight, the 2100 mAh would have been cheaper cost wise and more than sufficient.

[redboat219]

Somebody told me years back that too much capacity just make your wires run hot so that excess energy just gets wasted, any truth to this?

[trout]

As I understand it, no. That would not be true. Capacity is the amount available. Using Kevin's example, putting a larger gas tank in my car will not make it run faster, just longer. Having larger capacity in batteries does not change the volts it puts out, it changes how long it can put out that voltage.

[redboat219]

Wouldn't an engine running for 3 hours be hotter than one running for just an hour?

[trout]

Maybe.....but the heat generated has nothing to do with the battery mAh (except the battery supplies the power). I agree having more mAh allows longer runs, that means more fun (for some) by the waters edge (unless you are like me and cursed - just a joke) The heat build up in any electrical motor is from friction, resistance (that can also include the electrical flow through the windings)and lack of heat dissapation. Going back to a car analogy, my engine after 15 minutes is hotter than after 1 minute, but after traveling one hour it is not any hotter or cooler after 4 hours of driving (presuming no change in external environment). The heat curve levels off.

Let me take this a different route. Heat in the wire.

When electricity is going through wires, there is a resistance (nature of metal used). That resistance generates heat. Again not mAh of battery, but flow of current (which is the amperage used) through wire.
Further clarification - Voltage is how much electricity there is and amperage is how fast it is moving as it relates to current flowing through a wire. in other words, my motor runs on 12v. in my sub. The sub is floating with no props moving that would mean my system is at 12v and 0 amps. Now I gun it, the system is still 12v, but my amps go from 0 to 2 amps (so far we are not talking about the battery rating, just about what my motor needs to run). So let me go back to wires getting hot and then finish with the battery rating.
Two wires of different gauges, I will call one small (thin) and the other large (thick), both have equal current (amperage) going through them. The small wire will get warmer faster than the large wire. Why? because the larger wire has more surface area to distribute the load (meaning less resistance) and therefore generate less heat. Which is why we must consider wire gauge carefully when building a sub.
A properly sized wire will not get hot no matter how long you run it.
Back to the battery, let us say I have a 12v 2850mAh battery (and we are assuming the battery can handle the discharge rate (different post))
1 Amp = 1000 mAh (mAh means milliamperes X hour) I have my sub cruising fast, 2 amps are being used how long will my sub run? Take amp rating of battery divided by amps used - 2850/2000=1.425 hours of fast cruising time. All my wires are cool because they are sized correctly, I just can run longer because my battery has a larger gas tank.
I hope this diatribe has helped. If not, I am always willing to make things clear as mud. :-)
So, can you tell me why an electric motor generates heat? think amps and wire size.

Someone else can confirm or correct what I have typed.

Is this what you meant when you mentioned wires getting hot?

[Subculture]

I run 1700mAh batteries in my rig, and have never run them down. Consider that only a few years ago 700mAH was an average rating for AA rechargables, and that was sufficient for a day at the lake.

[KevinMc]

Maybe.....but the heat generated has nothing to do with the battery mAh (except the battery supplies the power). I agree having more mAh allows longer runs, that means more fun (for some) by the waters edge (unless you are like me and cursed - just a joke) The heat build up in any electrical motor is from friction, resistance (that can also include the electrical flow through the windings)and lack of heat dissapation. Going back to a car analogy, my engine after 15 minutes is hotter than after 1 minute, but after traveling one hour it is not any hotter or cooler after 4 hours of driving (presuming no change in external environment). The heat curve levels off.

Let me take this a different route. Heat in the wire.

When electricity is going through wires, there is a resistance (nature of metal used). That resistance generates heat. Again not mAh of battery, but flow of current (which is the amperage used) through wire.
Further clarification - Voltage is how much electricity there is and amperage is how fast it is moving as it relates to current flowing through a wire. in other words, my motor runs on 12v. in my sub. The sub is floating with no props moving that would mean my system is at 12v and 0 amps. Now I gun it, the system is still 12v, but my amps go from 0 to 2 amps (so far we are not talking about the battery rating, just about what my motor needs to run). So let me go back to wires getting hot and then finish with the battery rating.
Two wires of different gauges, I will call one small (thin) and the other large (thick), both have equal current (amperage) going through them. The small wire will get warmer faster than the large wire. Why? because the larger wire has more surface area to distribute the load (meaning less resistance) and therefore generate less heat. Which is why we must consider wire gauge carefully when building a sub.
A properly sized wire will not get hot no matter how long you run it.
Back to the battery, let us say I have a 12v 2850mAh battery (and we are assuming the battery can handle the discharge rate (different post))
1 Amp = 1000 mAh (mAh means milliamperes X hour) I have my sub cruising fast, 2 amps are being used how long will my sub run? Take amp rating of battery divided by amps used - 2850/2000=1.425 hours of fast cruising time. All my wires are cool because they are sized correctly, I just can run longer because my battery has a larger gas tank.
I hope this diatribe has helped. If not, I am always willing to make things clear as mud. :-)
So, can you tell me why an electric motor generates heat? think amps and wire size.

Someone else can confirm or correct what I have typed.

Is this what you meant when you mentioned wires getting hot?

You're spot-on with this explanation Tom. By the way, my benchmark for how to choose a battery is "the full-day test". As long as I can get a full day's use (not to be confused with Tx on all day) out of the battery pack with some margin to spare then I'm happy. Swapping out/recharging mid-day is unacceptable, being able to go for two days is nice but unnecessary because topping up over night with a wall-wart is easy to do. I've found with my 9ZAP that this requires 1500mAh or so.

[redboat219]

Ok, thanks for the info guys. Thinks the overheating mentioned to me was more about the motor/esc not electronics.