Large Model Association Forum

Andy Boylett wrote:It is fine not to fit a seperate switch with NiMh or NiCd but not when using LiPo batteries (I hate NiMh and NiCd !!).

What have you got against NiMh's Andy?

Safe, no need to remove from the model for charging and no need for a secondary switch which eliminated a possible point of failure.

Phil

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Fair points I'm sure for an exclusively electrics builder/flier Andy, but being as the 'majority' within the LMA still live in the dark ages and prefer to burn fossil fuels , I'm not sure your comments will find agreement with the majority. Mike didn't mention he was an electric flier, so I'd assumed he's one of the majority.

Most petrol powered 'large' models have their batteries buried somewhere deep inside the model (Normally for CG reasons). Ease of access to them I'm sure isn't high on everyone’s agenda when building, so access to get them in & out easily for charging is often a problem (certainly is for me). The fact you have to do this is the one main reason why I won't use LiPo's to drive RX's / servos.....it's just too much of a pain in the rear (especially in the field at a show)

Most of you average large models are running 1 RX with maybe 8-12 servos......other than maybe large 3D type machines with multiple high power servos all flapping about at the same time, we are nowhere near the current draw levels you talk of.(I know one of my current 80" Warbirds equipped with 10 servos only used between 3 and 400Mah per flight).....so the ability for a battery to be able to deliver these constant high currents isn't always necessary.....a 'simple' NiMh will suffice. Going back a llloooonngggg time, I remember the day when you could go flying with your .40 size sports models on a 5Ch RX with a 700Mah 4.8v NiCad and happily get 6-7 flights!!!!!!

Weight.....not really important when dealing with models of 20lb+.....what's a few oz difference going to do?

Voltage regulators....another 'possible' point of failure?

With care, NiMh's are very reliable (certainly have been for me over the past 8-10 years). I know approximately what will be taken from the battery per flight, but I run onboard monitors as well, just to check for unexpected voltage drops. I cycle each pack 3-4 times per year to check capacity......something I don’t think everyone does. I also make sure I use the correct settings on the charger....again, I think many just stick any old battery on a fast charge setting and assume it's 'cooked' then the buzzer goes.......far from it!!!

Anyway....this has got WAAYYyyyy off the shiny Lithoplate topic......so I'll shut up.

Phil

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Andy Boylett wrote:It is mainly Sam, with his prop hang antics that takes the current. However, we found by using the Spektrum Data Logger that even a very small current spike for less than a second could drag the voltage down to 5.0v (using a 6v NiMh). The Spektrum receivers cut out below 4.8v so we ditched our last NiMh out of his Supanova.

Don't know where you got that from Andy, Spektrum Rx have been shown to work down to 3.0v and I've seen them running on a 1s LiPo and they weren't falling all over the place.


Mark

Hi all, please can you keep this thread on topic otherwise I will have to remove them.