Rappy 50 - converting RX nimh pack to lipo.....

[v2kdj]

Hi guys n gals
What would i need to convert the 4 cell 'c' NIMH battery pack in my Raptor 50 to a Lipo RX pack..
and could you post any links to said items i may need...
Would there be any benefit to this or am i just lookin on spending money i dont really need to...LOL

Cheers, Karl.

[Planehazza]

LiPos are lighter and have no memory effect. What capacity do you require? Do you have a regulator installed?

NRGRX-36002 OUTRAGE NRG XPRX 2S1P 7.4V 3600mAH

[sacko]

LiFe packs are the future

Just plug them straight into your Rx.

[Steve]

LiFe packs are the future

Just plug them straight into your Rx.

Yes, but make sure all your servos are 6V compatible first.

[Mark_T]

Raptors are not exactly blessed with space on the radio tray so need to pick what you use quite carefully and that is not a small lipo in the link above.

NiMH don't really have a memory effect like the older NiCad and 'C' sized cells are pretty good providers of power anyway, so unless the pack is giving you cause for concern I wouldn't rush to replace it.

There won't be a regulator already installed with a 4 cell NiMH so room for that would be needed as well if you go with a Lipo.

I wouldn't rush to do this until the pack you have shows signs of old age.

[NoFixedAbode]

I have a I have a 4800 fromeca slung under mine with a duralight 7.5 amp reg. Works a treat can fly just shy of a gallon before charge.

Sent from my GT-I9100 using Tapatalk 2

[spillage]

Hi guys n gals
What would i need to convert the 4 cell 'c' NIMH battery pack in my Raptor 50 to a Lipo RX pack..
and could you post any links to said items i may need...
Would there be any benefit to this or am i just lookin on spending money i dont really need to...LOL

Cheers, Karl.

Hi Carl - for starters are you running 401 with futaba matching servos these need 4.8v to 5.1v max otherwise you will burn the gyro and servo... I have battery monitor inline now with my raptor titan...

Purchased the following from around the web

Turnigy 5v/6v 5amp bec which plugs straight into ar8000x receiver.... this is connected to a loong max 2300 which is shorter than a std 2300 3 cell lipo....

I made a holder to fit in where the 4 cell nimh was... I am running gv1 governer on mine and when checked after two flights of 8 minutes last week there was 94% left in battery.... on the nimh an 8min flight with futaba digis all round was drawing 350 mah with normal std flying....

If you are on spekky you have to bear in mind the voltage cut off which for the current dsmx recivers is 3.95v - turnigy bec was purchased from stormrc on ebay - £7.00 - two lipos were approx £26.00 delivered.
the small box to slide lipo into was made from the hard packing you find in pkg for tv's/computor peripherals etc.... balance is about the same as 4 cell 3700 nimh..... but i was only flying two flights on nimh them recharging.... now i can fly all day on two batteries!!!!!

any more info or pics email me

kind rgds

John

[v2kdj]

Sorted thanks all.
The battery pack at the moment is fine but now i know i need a regulator as well as the lipo to get it converted.
I'll hang on a while though till the nimh starts playin up.

[trillian]

Just to add, I had a few helis running on large NiMh packs and they worked fine but there are a few things to be aware of. First of all, there is no way I know of to accurately guage the remaining capacity so the only safe approach is to make sure it is fully charged before flying. I learned this the very hard way when I did a quick voltage check and thought the pack was charged well enough but it quickly dropped off in flight causing a brown-out of the RX and a crash. After that I changed out any remaining NiMh packs for LiPos with regulators. They can show a workable voltage at rest but then drop off drastically under load when they're getting low on capacity.

So you have to calculate how long it will take to charge based on the capacity as you can only trickle charge them at very low power. The ones I was using took many hours to fully charge.

If you're quite strict about it they will do the job.

The nice thing about a Lipo and regulator setup is you can easily monitor the pack for remaining capacity and they can be charged very fast. On my Raptor 50 I have a Duralite regulator and use 1900 / 2500 mah LiPos and this fits comfortably and is still lighter than the 4300mah NiMh packs I used to use.

[spillage]

Sorted thanks all.
The battery pack at the moment is fine but now i know i need a regulator as well as the lipo to get it converted.
I'll hang on a while though till the nimh starts playin up.

are you cycling your nimh - should do at least a couple of cycles every 6/7 charges to make sure nimh is holding charge - never wait till there is a problem always anticipate to save your heli from problems/crashes////

john

[Mark_T]

So you have to calculate how long it will take to charge based on the capacity as you can only trickle charge them at very low power. The ones I was using took many hours to fully charge.

You don't have to trickle charge a NiMH pack, you can use a peak-detect charger and do the job a lot faster, just watch for false peaks.

Using a Lipo is no guarantee of safety either.

I went through the annual ritual of testing my Lipo rx packs last night and ended up binning two of them for unaccaptably poor performance. They appeared fine if you just used a voltage checker, but under load the voltage sagged very badly and the total capacity was down to 50% of the rated value.

[trillian]

You don't have to trickle charge a NiMH pack, you can use a peak-detect charger and do the job a lot faster, just watch for false peaks.

Using a Lipo is no guarantee of safety either.

I went through the annual ritual of testing my Lipo rx packs last night and ended up binning two of them for unaccaptably poor performance. They appeared fine if you just used a voltage checker, but under load the voltage sagged very badly and the total capacity was down to 50% of the rated value.

Yeah, now I have a more sophisticated charger and it would probably be different but at the time I found I couldn't rely on the charger I had to detect the peak and stop. It would stop before a full charge was reached sometimes.

I use a Fromeco 8-Ball checker with my 2 cell Lipos. It shows the voltage at rest, at 1amp load and 1.5 amp load. That combined with the Hyperion charger gives me as good an idea as possible if the RX pack is charged and is holding a charge properly. Then after a while I know how much is drawn on average per flight anyway. It's just one of those things you have to be pretty diligent about whichever way you go.

For electric helis you have the option of using a BEC and as yet I have only used the built-in BECs in the small electrics and stuck with a separate RX power setup for my first larger (30 size) electric. I'm also trying the LiFe route on a new heli using an AR7100 RX so we'll see how that goes.