Buying my Maxi Joker 2 on Monday - please look this over...

[Hyde]

here is the parts list that i am ordering. i dont know which way i am swinging on the batteries just yet. LiPos would be alot better for weight but take forever to charge. i could conceivably charge the A123 in as little as 15 mins. and they are alot cheaper (if i build them myself). for main blades - i am leaning towards the Rotortech semi-sym 830's for better lift on this already heavy electric MJ2. also - i am kinda torn on the gyro. it's either going to be the Logictech unit or the 611. i am leaning towards the Logictech but that is just based on 2 guys at the field who have one and what i've read online. anyways - I NEED INPUT from you guys before i blindly go off charging the hell out of my credit card.

-

Copter: Maxi Joker 2 ($1300)

Motor: Actro 32-4 ($330)

ESC: PowerJazz ($385)

Swash Servos: Futaba 9351 x 3 ($330)

Gyro (with tail servo pkg.): Logictech 6100T ($290)

RX: Spektrum AR9000 ($170)

Stabilizer: AP2000i ($225)

IR Sensor: FMA ($43)

Main Blades: ??? (Looking at Rotortech semi-sym 830's)

Tail Blades: ???

---

Batteries: ???

LiPo -

10s (1 TP9000-5S2PX 18.5v 9000mAh = $500)
10s (2 TP4600-5SXL 18.5v 4600mAh = $500)
12s (1 TP9000-6S2PX 22.2v 9000mAh = $600)
12s (2 TP4600-6SXL 22.6v 4600mAh = $580)

A123 -

12s (2 6s2p 19.8v 2300mAh = $580 from Tanic - cheaper if i build myself. 24 cells!!!)

LiPo Charger: ThunderPower 1010C ($200)
or
A123 Charger: ??? A123 Systems say the cells can take up to a 10 amp charge. i can't find anything that can charge up to 10 amps / 12s. if i could - these packs could be charged to full capacity in 15-20 mins.

[phil007]

Nice shopping list!

I like my A123 batteries knowing that they won't go up in flames and cost half the price of Lipos for DIY packs. My Orbit Microlader Pro charges them at 8amps. Spartanrc.com should be coming out with their new gyro and it might be worth a look unless you need to buy something now.

The Joker is a solid heli...you'll love it.

Phil

[kgfly]

A123 -

24s (2 6s2p 19.8v 2300mAh = $580 from Tanic - cheaper if i build myself)
2 6s2p can give you either 12s2p or 6s4p but not 24s. I'm going to guess you mean 12s2p since this is a rough equivalent of 10s 4600 lipo.

The implications for charging are interesting.

6s2p 4600 mAh has a peak voltage of 21.6V, 1C charge rate of 4.6A (~100W) and max charge rate of 20A (~400W).

12s2p 4600mAh has a peak voltage of 43.2V, 1C charge rate of 4.6A (~200W) and max charge rate of 20A (~800W).

A TP1010 will charge a 6s A123 pack at up to 10A and a 12s A123 pack at up to 5A. Based on its max lipo rating of 10s=42V peak, it may not be able to get past about 90% charge of a 12s A123 pack. You would need to check if the new v2.3 firmware explicitly supports more than 10s A123. However, since the max rate at this voltage if 5A it is still only approx a 1C charge rate for the 12s2p A123 pack so you are not getting the advantage of fast charging.

The eStation 902 supports A123 up to 12s but the max charge current at that voltage is also about 5A.

One great thing about A123 cells is that they are very robust electrically. This means you can use a CCCV power supply as a charger even though the voltage precision is a lot lower than dedicated RC chargers.

This Mastech 0-50V/0-20A CCCV power supply recommended by Cryofix looks like a good option: http://shop.vendio.com/Evan2002/item/818330695/?s=1183802402

Set the voltage to 43.2V, the current limit to your desired max charge current and away you go. It will behave just like our chargers, limiting the voltage while maintaining the current then as the current drops off, raising the voltage to the target level. You might have to experiment with the settings to get 100% charge, but it should work. I would recommend using a WattsUp meter or similar in series with the battery to monitor the total charge going back into the pack.

[Hyde]

^ fixed

[Hyde]

one day left - needing some input guys!

[kgfly]

If you are prepared to make up your own A123 packs then you can save a lot of money. Typical cost of a Dewalt 36V power tool battery pack on eBay is about $100 to $150 delivered. Even at $15/cell that is only $360 for 24 cells. Add some time, solder, cables and heatshrink and call it $400 for 12s2p. It depends upon your comfort level with building the packs together with the value of your time.

If the battery layout on the MaxiJoker is suitable you can use the MEC solderless-tubes to make up shotgun packs very easily: http://www.modelelectronicscorp.com/products/SPTs/packs.php

I just noticed that MEC sell A123 cells for $20 each or slightly less than $20 each in a premade 8s1p pack. Hmmm, I guess to achieve 12s2p you would have to use 3 x 4s2p which might be more or less convenient depending upon your battery mounting options. The downside of the MEC tubes is that you have to disassemble them every so often to manually balance the cells.