|wise owl||09/02/2018 20:22:25|
|221 forum posts|
Have a couple of 4.8 v receiver battery that have seen better days and could be putting the model they are in at risk so time to replace them .It has been a while since I replace my receiver batteries and was thinking it is time to replace all my receiver batteries in my models and was thinking of replacing them all with 6v instead of 4.8 v .What is the opinion is 6v better then 4.8 ?
|Paul Marsh||09/02/2018 20:56:21|
3288 forum posts
If using 2.4, then you have to use 6V, that's a must.
On 35mhz you can get away with 4.8v, but for what it's worth, go to 6v, unless your servos (usually JR) support 4.8v only.
|Tom Sharp 2||09/02/2018 21:03:32|
3024 forum posts
Not on Futaba 2.4
|Paul Marsh||09/02/2018 21:16:17|
3288 forum posts
Both Spektrum and Futaba will cut (brown out) off at 3.5v, so 4.8 does not give you much headroom. Best to play it safe, then you have at least 2.5v headroom, not 1.3v, which is not much, although that is at a discharged battery, which you should not be flying at that point.
|1718 forum posts|
Why not on Futaba 2.4 Tom ?
322 forum posts
I'm looking for advice in this area as well. My systems are Spektrum, usually with Orange receivers.
By 6V, do you mean 5 NiMH cells?
What 6V receiver packs are commercially available?
I should mention that I'm still using 4-cell Nicad receiver packs, which haven't seen much use but have been in my possession for a few years(!).
Perhaps I should be replacing my Nicad packs, but I test them regularly and I've never had the slightest problem.
|Tom Sharp 2||09/02/2018 21:43:20|
3024 forum posts
I have been flying Futaba 2.4 since 2.4 started always on 4.8v using standard sevos. Spectrum was advised to use 6v but not Futaba.
Edited By Tom Sharp 2 on 09/02/2018 21:44:34
210 forum posts
Futaba receivers can go down to 2.6V I believe. So a lot more headroom.
I would use 6V - more torque from servos!
|john stones 1||10/02/2018 07:49:03|
9682 forum posts
If servos can handle it and the little extra weight/size isn't a problem, 6v every time.
|Martin McIntosh||10/02/2018 08:02:35|
2485 forum posts
Having been caught out twice with the same model when a cell failed in flight on 4.8, I changed everything to 6V Eneloops (JR gear). The exception is if using servos such as JR 591s, 4.8V only, in which case a 5V regulator must be used; not practical with only a 6V input unless you use something like a FRS Failover switch, in which case you may as well go for a pair of cheaper, lighter and much more reliable 6.6V LiFe packs to doubly insure against a failure. Quite a common set up these days.
|Dave Bran||10/02/2018 08:18:15|
1892 forum posts
All you people ceasing 4.8v packs can help the kids and donate them to my school club where they will be used with RC cars, boats, etc.
Oh, and BTW, historically a lot of Helicopter tail servos were voltage limited.
|1212 forum posts|
I generally use 6v but I have a couple of models on 4.8v and I use Spektrum and never had an issue.
|Denis Watkins||10/02/2018 08:59:10|
|2906 forum posts|
As you say, " never a problem " most sport set ups, with standard servos, normal surfaces, and flying without making the pilot unwell in the cockpit, the equipment was designed to run on 4.8v 4 cell packs.
6v 5 cell packs are commercially available from the same 4.8v supplier.
Do not just carte blanc fit 6v packs
If you fly larger surfaces, on a model like you stole it, with larger servos and 6v RX with 6v servos, then fit 6v 5cell RX pack
Check your equipment recommendations and decide.
My own set ups, like yours are 4.8v, with proper charging and checking are as manufacturers recommend and no problem
Edited By Denis Watkins on 10/02/2018 09:00:40
|204 forum posts|
I use Spektrum and have many models on 4.8v (2600 NiMh) which of course start at 5.2/5.5v when fully charged without any issues. Mixture of Spektrum, Lemon, Redcon & iRangeX receivers. Admittedly they all use 3-5 std or smaller servos. My 63" hack has 5 servos and runs on a 6v sub c 3300 purely for duration. The additional speed and power from 6v AAA / AA I understand comes at a price, in that they draw more giving reduced duration assuming of the same capacity. Once over 5 std servos then its either sub c or 3.0 LiFe for me. From experience I have never been able to drag down a NiMh 4.8v sub c in any aircraft using 5 std servos.
IIRC don't Eneloops / Instants because of their chemistry struggle to deliver the same current when loaded as a NiMh? If so then that is a good case for using 5 cell if using these.
|Peter Christy||10/02/2018 09:41:33|
|994 forum posts|
There is a lot of rubbish talked about receiver voltage requirements. I've used Spektrum receivers since they first became available. I must have 7 or 8 of them now, ranging from the tiny 4-channel ones up to the top of the range JR 9 channel ones. I've always used 4-cell NiCads or NiMhs, and never once suffered a brown-out.
Every case of brown outs I've investigated have been caused either by poor (old) switches, poor (old) connectors or poor (old) battery packs. In fact I've seen far more issues cause by voltage regulators and battery backers than I have by 4-cell pack use.
Not all servos can tolerate operation at 6 volt (JR have already been mentioned).
The only proviso I would make is that AA or AAA cells should ONLY be used in small, light models. For anything greater than about 1 meter in span, or fast and heavy, I would strongly advise the use of Sub-C cells.
Frankly, if you your packs are dropping to 3.5 volt under load, you shouldn't be using them!
To the OP I would say that if your gear has worked OK in the past on 4-cells, then keep calm and carry on!
|2031 forum posts|
At risk of repeating myself, no matter whether you run 4 or 5 cell RX packs, regularly perform a capacity test to check for dead or weak cells. With a 5 cell pack one can be blissfully ignorant of a dead or failing cell for ages and this will almost certainly never give trouble until a second cell weakens. A weak/dying cell in 4 cell pack will quickly reveal itself in the post crash investigation, and the make of radio will make no difference.
The C rating of AA type cells is actually very poor and I've been shocked to find several brands that are barely able to provide little more than 2.5C before collapsing. Even the simplest four button chargers usually have a discharge setting, it's easy to do and may well save a model. BTW, Beware power hungry digital servos.
For normal sport models I use 5 cell 2/3A size packs and for bigger stuff sub Cs. Echoing Pete's comments, avoid complication and additional points of failure. I always employ genuine Futaba switch harnesses rather than the cheap 'compatibles' and have never had one give trouble or doubt.
Edited By Cuban8 on 10/02/2018 09:58:59
|Martin McIntosh||10/02/2018 09:53:19|
2485 forum posts
The whole idea of using five cells is, as I said above, to insure against a cell failure as you have one in reserve.
Losing one from a 4.8V pack drops this to 3.6V and probably nearer 3V when all the servos start to move/glitch.
Eneloops are capable of higher discharge currents than the earlier chemistry cells. I was once at my wits end trying to solve a glitching problem on a 35mHz model, having done several Rx and servo changes, all of which performed correctly in any other model. The culprit was the 2600 NiMh pack which was totally incapable of handling the current demands (two of the servos were digital). Don`t touch these super high capacity things other than for Tx use. Replacing with 5 cell Eneloops cured it.
|481 forum posts||
This assumes the cell fails short circuit, if it fails open circuit or goes high resistance then the extra cell offers no advantage. In fact you have more chance of a cell failure in a 6v pack as there are more cells in the pack.
322 forum posts
Thanks Denis. My flying is fairly sedate, so I'm reassured by yourself and PC.
210 forum posts
Rocker, let's keep this simple (KISS).
As long as you're not using JR591 servos or digitals go with the 6V Panasonic AA 2000mah eneloop rx battery pack. No need for subC's and standard Nimh's discharge just looking at them. Also, wingspan has no revelance - I fly my 72" models with 5 standard servos no problem. Have no 😱.
Edited By ASH. on 10/02/2018 12:08:25
Edited By ASH. on 10/02/2018 12:09:17
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