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Old Oct 18, 2007, 01:20 PM
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can I use Lipos to power my receiver packs??

Is this possible?

Thanks

Tim
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Old Oct 18, 2007, 01:23 PM
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Bien sur! http://www.rctoys.com/rc-products-ca...EGULATORS.html Assuming you do not have a regular BEC
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Old Oct 18, 2007, 01:26 PM
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Cool

What voltage can I use from the Lipos? , as I have 11.1s sitting around.
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Old Oct 18, 2007, 01:28 PM
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You will need to use a regulator - the drop the voltage to somewhere between 5v-6.5v

Many out there - and yes they would support 3s voltages.

Mike
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Old Oct 18, 2007, 01:38 PM
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Quote:
Originally Posted by roundthebend
Cool

What voltage can I use from the Lipos? , as I have 11.1s sitting around.
The first one in the link i showed you has this spec:

Input Voltage: 5.2 volts to 32 volts
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Old Oct 18, 2007, 01:53 PM
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Excellent guys thanks alot

Is there much advantage before I order some Nimh 6v 2000mah cells to use normal over Lipos?
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Old Oct 18, 2007, 01:58 PM
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A 2s 2000 mAh lipo will weigh a great deal less - if that is an issue for you.

Not a huge advantage otherwise.

Mike
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Old Oct 18, 2007, 03:39 PM
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LVC is an issue so watch that on lipos.
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Old Oct 19, 2007, 12:44 AM
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Don't waste your time with LiPos -- go LiFePO4

These lithium phospate cells have the advantages of LiPo/LiIon cells but without the problems.

They deliver around 3.1-3.2V per cell under load (meaning a two-cell pack is ideal for your RC gear), can be charged at very high rates without damage, won't go bang or burst into flames if overcharged or physically damaged, can be discharged to below 2V per cell without damage, and seem to have a life of about 2,000 charge/discharge cycles.

The most widely used of these LiFePO4 cells are the A123 cells (2300mAH) but now there's a growing number of different sized ones coming on the market.

I just picked up enough of these (1350 mAH cells) to make six flight packs and ended up paying just $6.90 a pair -- which means the entire flight packs (including lead, heatshrink and plug) cost me about $7.99.

The total weight is 90 grams (about 3.3oz) which is lighter than 5-cell NiCd or NiMH packs of the same capacity.

So why mess around with dangerous and fragile LiPos plus the extra weight, cost and complexity of regulators when you can use LiFePO4 cells?
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Old Oct 19, 2007, 02:00 AM
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Depending on the RC gear...

Some stuff doesn't like over 6 volts, so the 3.2 v/cell 2 cell packs can be a problem... Especially since the peak voltage is higher than 3.2v/cell.

Check the specifications of the receiver and servos (and other equipment in your model) before supplying other than 4.8v nominal (4 cell NiCd peaks appx 5.4 v) or 5.0 v regulated to the RX

**********

I am using LiPos to supply electricity the RX in a gasoline powered model.

SmartFly Sport Plus regulator, which gives 5.0 v to the RX and 6.0 to the servos (and filters feedback interference out so long servo leads don't cause issues)

2 cell 800mah Lipos...
2 packs for the receiver (the regulator is auto-switching taking power from the pack with higher voltage)
1 pack for the engine's electronic ignition... via a regulator that supplies 5.7v.

All of my equipment is rated to work correctly on the voltages supplied.

Most of my receiver systems get powered by 4 cell NiCd or an ESC's BEC. I plan to phase out all of the NiCds. LiPo saves significant weight and there's essentially no battery self-discharge to worry about.

The A123 and similar... are fine. But they don't save as much weight.
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Old Oct 19, 2007, 04:13 AM
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Quote:
Originally Posted by fhhuber506771
Depending on the RC gear...

Some stuff doesn't like over 6 volts, so the 3.2 v/cell 2 cell packs can be a problem... Especially since the peak voltage is higher than 3.2v/cell.

Check the specifications of the receiver and servos (and other equipment in your model) before supplying other than 4.8v nominal (4 cell NiCd peaks appx 5.4 v) or 5.0 v regulated to the RX
Virtually all modern RC gear (with the exception of a few very small or specialist servos and some heli-gyros) operate just fine on 6V. Lots of people have already made the switch to 5-cell NiMH packs which have a peak voltage of about 6.7V when hot off the charger and I've never heard of anyone having a problem.

The higher voltage of a 5-cell/LiFePO4 pack is actually very beneficial if you're flying with the latest 2.4GHz stuff because it is far less likely to suffer a low-voltage induced reboot than with a 4-cell (4.8V) pack.

Quote:
I am using LiPos to supply electricity the RX in a gasoline powered model.

Most of my receiver systems get powered by 4 cell NiCd or an ESC's BEC. I plan to phase out all of the NiCds. LiPo saves significant weight and there's essentially no battery self-discharge to worry about.

The A123 and similar... are fine. But they don't save as much weight.
However, the *big* things in favour of LiFePO4/A123 packs are simplicity, reliability, safety and robustness.

Do you remove your Lithium batteries from the plane to charge them (as I believe the AMA recommends/mandates)?

And what's the life of a LiPo pack in terms of charge-cycles? LiFePO4 cells are generally rated to between 2,000 and 3,000 charges whereas your average LiPo (even in light duty) is lucky to get 200-300.

Regulators are just extra weight and something else to go wrong. As a growing number of 2.4GHz users are also finding out, if your regulator isn't up to the task (particularly if you're running digital servos) then you can end up with a total loss of control if/when the receiver reboots due to regulator overheating or simply a lack of current capacity.

Many of the guys flying giant scale stuff (TOC, etc) are rapidly switching from LiPo/regs to A123 with great results. They wouldn't do that unless there were some real benefits -- remember that some of those planes are 40% or larger and worth many, many thousands of dollars. They want *reliability* and that's something greatly enhanced by *simplicity*.
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Old Oct 19, 2007, 10:02 AM
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Quote:
Originally Posted by XJet
Many of the guys flying giant scale stuff (TOC, etc) are rapidly switching from LiPo/regs to A123 with great results. They wouldn't do that unless there were some real benefits -- remember that some of those planes are 40% or larger and worth many, many thousands of dollars. They want *reliability* and that's something greatly enhanced by *simplicity*.
Giant scale is a whole different game. They can give up a few ounces on their batteries. What works with one type of craft is not always the best solution for others. For weight savings and energy delivery, nothing beats lipos. They and brushless motors are what have made electric flight fun and accessable to everyone.

If lipos are so dangerous, why do we not worry about our cell phone and laptop batteries?
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Old Oct 19, 2007, 11:13 AM
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Depending on how you use them...
LiPos get 50 to 2000 cycles.

I have a cell phone with LiPo that has over 1500 charge discharge cycles.
I have one model that uses LiPo for the electric drive with well over 700 charge/discharge cycles.

The weight of LiPo is so much lighter than the A123 that the addition of a regulator means the LiPo is still saving 1/2 the weight difference between equal capacity 2 cell packs.

I;m sorry that you think that the A123 and similar are the ONLY answer... They aren't.

Which vendor of A123 cells do you work for?
Tell them that their reps need to be more realistic.
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Old Oct 19, 2007, 02:45 PM
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Is your mobile using LiPo or Lithium Ion???

There *is* a difference.

And speaking of smaller models... how much does your LiPo/Regulator system weigh?

The latest lot of LiFePO4 packs I've looked at weigh in at 3.2oz and that's for 1350mAH capacity. Is a LiPo/reg setup with the same capacity that much lighter? They also cost under US$10 - how much does your LiPo/reg setup cost?

And no, I don't work for or sell any kind of batteries -- I just find it amusing that people seem hell-bent spending more money than they have to and introducing extra complexity/risk for what may be no gain.
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Old Oct 19, 2007, 03:29 PM
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What I'd like to know is where the heck to get A123s for under $7.00!!!
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