LiPo 2s to 3s switching ?

[TacoCrawler]

just curious...

Was wondering if it were possible to run two batteries on board
that could be switched mechanically or electronically...
and would allow a user to choose (switch) between either a 2s or 3s LiPo ?

In theory... the effect would be like have a nitrous switch.
shutting down the 2s connection from the system and alternating to the 3s.

Was thinking of on the fly switching
( ^ tho' stopping momentarily during switching would be acceptable)

Not the same thing as physically plugging in each battery individually when extra power is wanted.
But a different approach with similar results.

Is something like this even possible ?
Or would TX/RX recalibration make this idea a fail ?

[mark32]

you would still have stopping time from esc arming which is usually 1.5s

[Johnnysplits]

Why don't you just run it on 3s?

[TacoCrawler]

Originally Posted by Johnnysplits

Why don't you just run it on 3s?

'cause I don't need the extra power all of the time...
and would think the 2s would offer less wear to the motor's comm/brushes then when using 3s full time.

Maybe it wouldn't be worth the hassle of it...

wuz just curious if it had ever been done before !?

[monkeyracing]

Never heard of it being done, but its possible. There isn't any extra wear to your gear if you run 3s. In any case, it would be easier to just use less throttle when you don't need the power. If your radio has an exponential function, that would help too.

[Greatscott]

I think your looking at more trouble than its really worth. I think cycling your electronics between packs will be a lot rougher on your equipment than 3S will be on your motors.

If you don't want that much power all of the time, don't squeeze the throttle as much.

[skid]

You could run the rx and servos off the 2s battery all the time. then a relay to switch the esc power to either battery. With the relay switched from a rx channel. Possible, yes. Lot of trouble when you could just squeeze half throttle instead.

[Johnnysplits]

Originally Posted by TacoCrawler

'cause I don't need the extra power all of the time...
and would think the 2s would offer less wear to the motor's comm/brushes then when using 3s full time

A: Being that you're questioning it then yes, you need 3s power all the time
B: You're really concerned about brush wear? Then go BL
C: Putting a 3s lipo to a brushed motor is at about the same voltage as a 7 cell nimh pack which takes a while to wear down brushes so you really shouldn't worry about it.

[TacoCrawler]

Originally Posted by Johnnysplits

A: Being that you're questioning it then yes, you need 3s power all the time

We'll see as I just purchased two 3s 2100 mah to test your claim

Originally Posted by Johnnysplits

B: You're really concerned about brush wear? Then go BL

I know how to change brushes...
just don't want to do that often.
I'm not buying into the necessary components for a brush-less system.

Originally Posted by Johnnysplits

C: Putting a 3s lipo to a brushed motor is at about the same voltage as a 7 cell nimh pack which takes a while to wear down brushes so you really shouldn't worry about it.

Actually from what I've gathered...
a 3s LiPo sports 11.1 v (12.4 v full charge)
So a nimh would need be 8 cells to compare (9.6 - 12.8 v) ?

thought nimh were 1.2 v per cell... but could be peaked to 1.6 v ? :duinno:

I'm no battery guru...
so please correct me if I've got it all worng

[Devil Inc]

Having the Drag Brake cranked will create extra wear on the motor brushes. And 3S is FUN all the time.

[TacoCrawler]

Originally Posted by Devil Inc

Having the Drag Brake cranked will create extra wear on the motor brushes. And 3S is FUN all the time.

good to know... thanks.

so with a 3s I would expect more drag braking then with a 2s ?

I doubt muh pos Axial RTR TX will offer much adjustment for that.

[Devil Inc]

The drag brake is controlled via the ESC, but there are variables, such as the design of the motor and how the rig is geared. You would have to adjust the amount of drag brake the esc applies by following the esc's programming steps. Usually, it is done with a CastleLink if it's a Castle based product, Tekin has their HotWire, other manufacturers have field programming cards.

I don't believe the pack voltage has an effect on the drag brake, not 100% on that though.

[TacoCrawler]

yeah I gotta buy into that CC link still

just hooked up my 3s thru my AE-2... no bueno

thought I read that others had gone to a 3s on the AE-2 without issue !?
not the case for me...
seems to starve the servo... or just glitches very noticeably

guess I'll need to install my CCbec to run the 3s LiPo's !?

~I have no excuse for delay, just laziness~


a different topic...

Axial/Hobbico sent me a Fut S3305 servo as a warranty replacement for
my failed AS-3 servo...

Seems the Fut. S3305 is a little underpowered, compared to many...
But seems to net decent reviews...

Think it's a better servo then the AS-3 ? yes-no ?

^ was free to me... (warranty replacement)
so I guess I shouldn't complain unless you all might think I should !? Lol

[scale crawl]

If you don't need 3s power all the time just run 3s' s and learn throttle control.. that way you can run then when you need the power smash it down and go....

[Johnnysplits]

Originally Posted by TacoCrawler

Actually from what I've gathered...
a 3s LiPo sports 11.1 v (12.4 v full charge)
So a nimh would need be 8 cells to compare (9.6 - 12.8 v) ?

thought nimh were 1.2 v per cell... but could be peaked to 1.6 v ? :duinno:

Back in the day when I raced 2wd mod buggy, yes I would peak the pack out to almost 11v then throw it in the car and race. But I was running matched sanyo cells which made a big difference. Don't sweat using a 3s lipo.

[Olle P]

Originally Posted by TacoCrawler

'cause I don't need the extra power all of the time...

You might not need to use it all the time, but you need to have it available for use. (*)

Originally Posted by Devil Inc

I don't believe the pack voltage has an effect on the drag brake, not 100% on that though.

In theory I think there's an effect.
The drag brake operates by providing a voltage to pull the motor in the opposite direction of what it's running.
At times where the 2S voltage is insufficient to hold the motor still a 3S battery should make a difference. Not that this is likely to ever happen though...
_______________

(*) It's a bit like the motor solution for the Swedish MBT called strv 103, or "S tank" as it's more known abroad.
Diesel or turbine engine? Diesel has the advantage of very low fuel consumption on idle, but it's bulky and heavy. Turbine is smaller and light weight but a real fuel hog on idle.
A tank (just like a crawler) spends most of its time on or near idle, with a few instances of need for high power in between, so the tank designers reasoned: "Let's have both types of motor. A diesel to run all the time, and a turbine to add power when needed."
Problem was that the turbine takes a comparatively long time to start, and extra power is always needed at very short notice. ("We're being shelled and need to get away NOW!") Therefore in practice the turbine had to be on (and idle) most of the time anyway...