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Battery for Futaba Tranny T10J

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Rocker08/03/2018 11:21:47
198 forum posts

The transmitter battery in my Futaba T10J Tranny needs replacing .The battery that came with the tranny is a 4.8 1200mAh battery .I have a brand new 4.8 2000 mAh receiver battery Would this be OK to install into my T10J Tranny or would it be best to buy a new 4.8 12000mAh battery to put in the Tranny .Do not like wasting money ,do not want to buy a new 1200mAh battery if the 2000 would do the job ???

Stuart Z08/03/2018 11:27:06
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280 forum posts

Hi

I’m not an electrics expert, but my T8J has a 2500mah Nimh battery and seems fine.

S

Frank Skilbeck08/03/2018 12:19:52
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3991 forum posts
96 photos

Yep, the only thing to note is that the Tx would run 1.5x longer between charges laugh.

Rocker08/03/2018 15:40:21
198 forum posts

OK so if a 2000mAh battery will last 1.5X longer that has to be better then the 1200mAh so it would be a no brainer not to put the 2000mAh battery in the tranny and leave the 1200 mAh battery out ????

Biggles' Elder Brother - Moderator09/03/2018 11:23:38
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15203 forum posts
1407 photos

Yes Rocker, as long as it physically fits in the Tx OK I'd go for it.

BEB

supertigrefan09/03/2018 13:02:43
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114 forum posts
1 photos

The mAh stated on a battery is the charge rate and capacity of it, so a larger rate in the same application will last longer but also take longer to charge at the same rate as a smaller one, a larger rate is sometimes (not always) physically larger than a smaller rate. It's usually a good idea to go for a larger rate replacement.

It's the voltage you shouldn't deviate from, if it says 4.8v then stick with that.

The Wright Stuff09/03/2018 14:25:03
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1160 forum posts
225 photos
Posted by supertigrefan on 09/03/2018 13:02:43:

a larger rate is sometimes (not always) physically larger than a smaller rate.

I think I read somewhere that higher capacity NiMHs can be less reliable, less long-lived, and have a higher internal resistance than smaller capacity ones of the same package size. This is because to 'stuff' more capacity into the same volume, other components (like insulators, electrode thickness, etc) have to be compromised.

I'm not sure how much NiMH technology has moved on over the last few years, so this advice may or may not be 'out of date' - but make sure you are comparing like with like - you rarely get 'something for nothing'...

For a low power application like this, it probably doesn't matter too much...

Edited By The Wright Stuff on 09/03/2018 14:27:58

Biggles' Elder Brother - Moderator09/03/2018 14:29:06
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15203 forum posts
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Mmmmm. Let's try to avoid confusion here. The mAh figure quoted for a battery is not a "rate" - its a capacity. It is literally a measure of how much electrical charge the batterry can store. Think of it like a petrol tank - a bigger tank holds more petrol and the car can go further without refills.

The nearest thing to a "rate" where batterries are concerned is the "C-rating" - this tells us the maximum rate that electric charge can be removed from the battery - it therefore defines electrical charge flow rate - which we call current and measure in Amps. So, if a battery is rated at say 20C and has a capacity of 2000mAh, then the maximum rate of charge removal from the battery is:

2000 x 20 = 40000 mA, or 40 amps.

Now this battery is a NiMH I'm guessing - so its not usual to specifify the C-rating, for such - they cannot supply current at a level even close to a Lipo - but of course in this application they don't have to.

I'm sorry if this seems nit-picking or pedantic to some - but its important that we maintain clarity and consistency around the basics.

BEB

Peter Christy09/03/2018 16:11:29
934 forum posts

BEB: Absolutely right!

To the OP: If it fits, then use it! As others have pointed out, its the voltage that matters, not the capacity. Just bear in mind that if you are using the charger supplied with the radio gear, it will take correspondingly longer to reach a full charge. If you are using an after-market "peak-detect" charger, simply adjust the charge rate to suit.

The internal resistance of small NiMH cells is only an issue when used in high current applications - such as a lot of digital servos! Transmitters - especially 2.4 GHz ones - have quite modest current requirements, so this is not an issue here.

--

Pete

kc09/03/2018 16:47:47
5464 forum posts
161 photos

What do the experts think about using Vapex Instant or Eneloop instead of normal NiMH?

A set of Vapex Instants in my Spektrum DX6I still shows 5.3 volts after 6 months without use or charging. Same with those used in my cameras - always ready to use.

Peter Christy09/03/2018 17:06:23
934 forum posts

I've been using Eneloops in transmitters for ages without any issues whatsoever. I've also used them as flight packs, but not in models with a large number of "digital" servos, again no issues - even with Spektrum receivers!

Vapextech appear to use the same (or very similar) technology. I've been using one as a "bench pack" for a while, and would have no worries about using it in a model.

--

Pete

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