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[QUOTE=Arceenut;1895089]All sugestions above are good but several comments need a little thought.  Modern NiCd batteries do not exhibit the "memory" that the older technology cells used to have.  Memory effects if in fact they have is very minimal and not a concern.  I agree with th fact that NiMh do not have the high current capabilities of the NiCds and they do sag more under load. I have never trusted the high capacith NiMhs. Re useing LiFe 2s is a good way to go.  The only caveat is that some servos cannot tolerate the higer voltage of a LiFe. Check the specs of the servo. If the servo is rated for 6 volts (5cell nickel*) they will be fine.

All that being said, do A little trouble shooting by eliminating components one at a time.  Ie Replace the battery with a KNOWN good one.  Plug the battery directly into the receiver to eliminate the switch harness as the problem. Make sure the wires in the battery circuit are adequate for the loads,  Some cheap switch harnesses are made with 28Ga wire and are totally useless in a model larger than a park flyer foamy.  5.5 volts is a good set point for a 5 cell NiM* battery.  That translates to 1.1 volt per cell which is the nominal "empty" voltage of a NiM* battery.[/QUOTE]

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Topic Review (Newest First)

09-14-2014 10:23 PM

dashpuppy

Re: Voltage drop

Quote:

Originally Posted by 4*60

Then use redundant life packs.

Glad i didn't have to say it

Life packs can handle the current. NIMH can't probably a reason why not many people use them any more. All the people i see fly small big planes are running LIFe packs, no regulator and just simple setup. Most people these days have a LIPO charger too!

09-14-2014 10:19 PM

4*60

Re: Voltage drop

Then use redundant life packs.

09-14-2014 08:07 PM

luv2flyrc

Re: Voltage drop

Deleted, can't be bothered
Mike

09-14-2014 08:00 PM

dashpuppy

Re: Voltage drop

Quote:

Originally Posted by luv2flyrc

Sorry, don't agree. Redundant batteries are not an option for me in a plane this size.

You will not notice the added 6oz. You have a lot of experience with 96"+ planes?

Mike

So instead of fixing the problem and and using newer batteries, that don't voltage-sag. You want to use NIMH ?

Never said you would notice the 6oz, but why would you want to add TWO older style batteries..

09-14-2014 07:44 PM

luv2flyrc

Re: Voltage drop

Quote:

Originally Posted by dashpuppy

It also adds more weight, best practice DITCH the switch, Ditch the NIMH, and ust buy a Life battery, when you go flying plug the battey in, when your not flying keep it unplugged. Slider / toggle Switches fail and cause other issues.

Deleted, Can't be bothered

09-14-2014 07:40 PM

dashpuppy

Re: Voltage drop

Quote:

Originally Posted by luv2flyrc

You could simply add another 2150 NIMH battery and switch, same as you have now. A single 2150NIMH is marginal for a plane this size...not in capacity but, in current delivery, this is why you are seeing the voltage drop.

Adding a second one not only gives you some redundancy and doubles your capacity but, most importantly it doubles the current capability and you will no longer see the huge voltage drop.

Mike

09-14-2014 07:09 PM

luv2flyrc

Re: Voltage drop

Deleted

09-14-2014 03:05 PM

goneflyin

Re: Voltage drop

How OLD is the wiring between battery and reciever?
Old connectors are a big problem, seen it many many times.

Don

09-14-2014 02:21 PM

Arceenut

Re: Voltage drop

A capacitor is fine for very short duration spikes and dips but is NOT a substitute for proper wiring, components and batteries. A one FARAD capacitor can supply one amp for 1 second before the voltage drops to 60 percrnt of it's charged voltage. A one Farad capacitor capable of withstanding a charged voltage of 5 volts would measure approximately 3 inches in diameter by 6 inches in length. There are "capacitors" of 1 farad capacity used as backups for compueter memories that are much smaller (1" X 1") but would be useless in this application as they have a very high ESR (effective series resistance}and can discharge only at very small currents such as maintaining memory for short (several minutes) in some EProms etc.

09-14-2014 01:25 PM

dashpuppy

Re: Voltage drop

Quote:

Originally Posted by michaely

Hi Cliff,

Interesting. Can you point me to any further information on how to set up capacitators with an airborne NiMh pack to deal with momentary high power needs of servos?

thanks

Ditch the NImH battery, buy a LIFe battery save your self the issues! Adding cap's is just complicating things..

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