Real Ampdraw discussions etc.

[Thos]

Just a quick question to that chart Tony. I see it uses 7,4V, 11,1V etc, but isn't it more correct to use the peak charged volt when calculating RPM for a setup?

[JIM MARCUM]

Just buy an eagle tree or similar. That will give you all the real world data you need on your setup.

That, or buy a Castle ICE-2 200HV. It logs everything but top speed. JIM

[JonD]

That, or buy a Castle ICE-2 200HV. It logs everything but top speed. JIM

I've been thinking about adding a data logger to my Genesis. The Castle unit looks good, as nearly everything is integrated in to it, as opposed to using separate sensors for RPM, current etc... with the Eagle Tree. But one thing it falls short on is a temp sensor or input for the motor temp. That's a shame. I already have a separate temp logger that I have been using for the motor, so no big deal I guess.

Why would Castle not include a BEC in the unit? It does just about everthing else. I am not going to add a separate battery pack for the reciever and servo, so I will have to make up regulator circuit to power the reciever and servo from the main batteries. Just seems uneccesary when Castle could have easily included a decent BEC circuit in the design.

Jon

[Fluid]

OP, this is about as good as you're going to get: http://forums.offshoreelectrics.com/...l-program-file

If a BEC was as "easily included" as the poster suggests, then Castle would certainly do so. None of their HV controllers have BEC, apparently it is due to cost, temperature effects on the ESC (BECs get hot), and limited amperage output at voltages over 8S.



.

[properchopper]

Just a quick question to that chart Tony. I see it uses 7,4V, 11,1V etc, but isn't it more correct to use the peak charged volt when calculating RPM for a setup?

Thos,

You're correct in the respect that the "off the charger" nominal voltage is somewhat higher than the voltage points on the chart, but here's my take : Once you get on the throttle the voltage will dip well below the nominal voltage; how much depends on load and battery condition. The chart is just a basic guide to help choose the correct pairing of motor KV vs. operating voltage. Your target rpm within these limits is a function of setup - hull type, prop and such.

[TheShaughnessy]

well below nominal? A decent battery should hold close to its nominal voltage. My 4s2p 6600 mah gens ace set up held voltage around 15 for the first min and 45 sec and by the end of 4 min they were still holding at 14.4. On the other hand i've seen a slightly puffed turnigy 4s 5000 mah pack sag to 11.5 volts under a 50 amp load, needless to say i clipped the connectors off that batt and no longer run it.

It would actually be less correct to use 16.8( fresh off the charger 4 cell) instead of 14.8. 1. the battery will sag to nominal voltage if not below and 2 a motor under load isn't going to reach 14.8 * xxxx kv. Rpm sensor is o the way so don't know exact numbers, but you will turn less rpm under load

[JIM MARCUM]

Never argue about FE boats with a guy who has won over 14 NAMBA FE records. Or an Irishman.

I just hope the pile of Turnigy Nano Tec LIPOs I bought will last through this season. Michael, where did you buy those GENS ACE LIPOs? JIM

[keithbradley]

well below nominal? A decent battery should hold close to its nominal voltage. My 4s2p 6600 mah gens ace set up held voltage around 15 for the first min and 45 sec and by the end of 4 min they were still holding at 14.4. On the other hand i've seen a slightly puffed turnigy 4s 5000 mah pack sag to 11.5 volts under a 50 amp load, needless to say i clipped the connectors off that batt and no longer run it.

It would actually be less correct to use 16.8( fresh off the charger 4 cell) instead of 14.8. 1. the battery will sag to nominal voltage if not below and 2 a motor under load isn't going to reach 14.8 * xxxx kv. Rpm sensor is o the way so don't know exact numbers, but you will turn less rpm under load

I think Tony meant that the voltage will drop well below resting voltage when under load, that's why we use the nominal voltage figures instead of the fully charged/resting voltage.

[properchopper]

I think Tony meant that the voltage will drop well below resting voltage when under load, that's why we use the nominal voltage figures instead of the fully charged/resting voltage.

Exactamento. Here's a picture (my ET file got corrupted) of a Turnigy vs Hyperion - Old stuff - IIRC it was a Titan29 - 9XL on 4S.

The Hyperion dropped less; the Turnigy dropped more but held the lower voltage without further degradation. Remember that for each volt dropped you lose 1 KV at the prop.

(Turnigy on left)

DSC01735-1.JPG

[TheShaughnessy]

Never argue about FE boats with a guy who has won over 14 NAMBA FE records. Or an Irishman.

I just hope the pile of Turnigy Nano Tec LIPOs I bought will last through this season. Michael, where did you buy those GENS ACE LIPOs? JIM

I get the Gens ace from hobbypartz.com Free shipping for orders over 50 bucks. Those numbers were also on a spec motor so a 1515 1y may tax them a bit more.

I wasn't arguing by the way. That is info from eagle tree so pretty hard to argue that. I greatly respect tony's advice on anything, but also realize he is as human as the test of us.

[JIM MARCUM]

Thanks Michael. Not so sure Tony's human. Have you ever seen him running around Legg Lake after midnight wearing purple go-go boots, pink pokadot tights and a pink Superman cape? I think he arrived here from Krypton as a baby in a little pink rocket.JIM