Last post by FlyinBrian - June 29, 2020, 18:06:23 pm
Two 1500 pack will fit where needed but a 3000 will not. Cells are actually 2/3 AA but I have tested the packs separately at 3A discharge and they stay above 5V until well over 1000Mah has been used so even with heavy use I should get a few flights out of them.
The two switches is just a convenience rather than make up a wiring loom.
Re Diodes and s/c - I can not remember ever having a NiMH (or NiCad ) cell go s/c and am not aware of anyone who has??
I recall ( I think ) someone called "Red" who used to work for a cell manufacturer used to write about batteries in an online forum c1998 - 2000 and he reckoned s/c was a rare form of failure - occasionally dendrites? may cause a short inside a cell but they were very tiny and the current flow from regular use cleared them. They could build up to the point of damaging the cell if the pack was idle for a long time.
According to most of the LMA friends I have, the 'dragging a battery down' thing is a fallacy. It is fine to use two batteries without any diodes or nonsense. I prefer to use sub C cells, but often room dictates the use of AA cells, of which I have never had a failure. If the batteries you normally use have been reliable, then two batteries seems overkill. I am a great advocate of two switches wired to the battery and Rx to give redundancy, as the switch is the weakest link, and failures are common, but a 5 cell NMH already has a bit of redundancy in that, if one cell goes down, the battery will function as a four cell adequately. Its your choice however, the ultimate being two switches, two batteries and two receivers. The dual switch thing will cost a bit of soldering, and a normal switch. I do that on all my IC models, even the Acrowot. Cheap for peace of mind.
Is there a reason why you want to fit two 1500mAh batteries rather than one 3000mAh one?
What type of batteries are you using? (hopefully not AA size!)
As a general rule it's a bad idea to connect batteries in parallel without isolaion/management because any single cell failure will drag both packs down, and could draw enough current from the "good" pack to start a fire. So if it's capacity (or current) you're after it's better to have a bigger single battery. If you want increased reliability from having two batteries you must have either passive (diode) or active (power management unit) isolation - as a failure in either battery will drag the other one down as well. So without the isolation fitting two batteries makes it HALF as reliable, not twice.
If you don't want to fit an overpriced management unit you could always fit one that isn't overpriced.
Last post by FlyinBrian - June 29, 2020, 13:13:26 pm
To help with the CG on my Giant Aeromaster I need to use two 1500 mAh NiMH 5 cell batteries and am planning to use two switches into one Futaba Rx. I don't really want to mess about with diodes and from what I read many years ago there is no need.
The model has 5 x Hitec 625 heavy duty servos and a Futaba 3010 on throttle. I also do not want to use Lipo batteries and regulators or overpriced power management boxes if possible. Just two identical batteries, two switches and two leads into the Rx.
I am using a 2cell 2200 Lipo for the ignition on the MVVS 40cc petrol but only because I have one.
For my Horus I found the printed manual offered by T9 to be invaluable. They do a Taranis T9D version of it (here) and I would recommend buying it, There are other on-line resources and pdf manuals, but they aren't as clear or useful IMHO. It's also properly printed on heavy-grade paper with a spiral binding so it has lasted weeks of heavy use without even a hint of pages coming loose!
OpenTx is extremely powerful but it can be bit of a steep learning curve if your previous transmitters were JR/Futaba/Spectrum etc (less so for those migrating from Multiplex). But it is logical and once you grasp the basic idea you find there is very little you can't do!
Thanks for the replies, actually the latest X9D Plus 2019 has Access protocol included; so bit of a mystery why BangGood offer the option. I think I might be here quite often while I set up some programes for the little beastie!
I did get into quite serious discussions with a gun club to do exactly this but not using machine guns
A sales rep for one of my suppliers was a very keen clay-pigeon shooter (12-bore etc) and I happened to have a SPAD combat plane in my office and one thing led to another.
The idea was to use the same sort of safety precautions we used for combat flying combined with the discipline of clay-pigeon shooting. The shooter would be in a small fenced enclosure, with high sides and rear to reduce the available aiming arc, the plane would fly in a nominal "box" in front of the shooter (our combat matches were held within a 100m square "box", you lost points if you flew outside it consistently).
The SPAD planes were made from Correx, PVC drainpipe etc so cheap as chips to build, and the radio gear would be protected with aluminium sheet (no, not the antenna!)
Ultimately, we concluded that 'elf n safety people would probably not approve and a "£responsible" club would not allow it, so it went no further