New lipo Battery for my stock SC (red)

[d22av]

Hey everyone,

After flying my cub 6 times, getting comfortable with learning to fly it, and reading a lot about upgrading to lipo batteries I decided to purchase 2 lipo batteries and a lipo charger.
I wanted to double check to see what you guys had to say.

I don't want to change anything on my cub other than the batteries right now and I just want to make sure everything will work fine and not burn out....I don't want to give the system too much power and hurt the motor or the RX and ESC. These are the batteries and charger that I'm thinking about buying.

Charger---- www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7028

Battery( I'm planning on buying 2) ----- www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6306

PS- I know that I will need to switch to a 10 x 6 prop and have already bought two.

Thanks in advance for any input

[flydiver]

Good choices. You'll need new connectors. You don't want to stay with Tamiya. EC3 seems to be the up and coming ticket with Deans maybe losing some favor. Both are good, either are way better.

[ginginho]

One thing that everyone should have when they fly lipo is one of these if you haven't got one already. It makes checking your packs at the field a doddle and could save you draining a pack too far.

[gagallagher04401]

I have that charger, got it when going to Lipo's I like it. WOrks good for me. Only thing I charge with it are lipo's but has many capibilities which is nice. I also likes it size.

[belem]

You'll need to cut up your battery box if you go with those lipos. Not a big deal, but it can be unnerving your first time.

[d22av]

Thanks everyone who responded. I love how quickly people try to help out on this site, it's really great.

So i think i will order the following batteries and charger.

Can anyone give any advice on how to break in lipo batteries when you first get them, i really want to take good care of them so that they last.

Thanks

[flydiver]

1. Don't believe the LVC on the Cub-it's too low (~8.8-8.9v). That's poor.
Fly by time, stop when there is 20% of the lipo left. That translates to ~ 10.1v RESTING (not flying).
For the first several outings keep your thumb out of the throttle-fly gently, keep the amps down, only fly to 50% before recharging. That's about 11.5v RESTING.

NEVER discharge it below 3.0v/cell.
Do not charge and store in the heat (hot car, hot garage, etc).
If you are a sporadic flier best practice is to charge to 50% and store in a ziplock in the fridge. Personally I do that almost everyday but I recommend that if over 2 weeks and certainly if it's going to set a month or more.
Rewarm to room temp in the ziplock (prevent condensation) before charging normally.

This is just one of a myriad of lipo care FAQ pages. Good basic 1 page read.
www.maxamps.com/lipo-care.php

If you want a mess of info start reading here:
www.batteryuniversity.com/partone.htm
This site has a lot of very useful information on rechageables of all sorts.

[patmatgal]

ginginho
Picked up a couple of those, figured if one didn't work the other one would. Both worked so I used one at home and the other in the field, then ended up giving the one in the flight box to another flyer and the remaining one to my brother. Ordered 3 more, wonder how long I"ll be able to hold onto one... They are great!

[d22av]

FlyDiver I am confused about how you got those numbers....any way i tried i couldn't replicate so I've been trying to figure it out on my own..

This is what i got after doing some research and calculations....
Please correct anything you think is wrong....

Ok I want to cover everything so I'm going to start with the basics.
Please correct anything you may see that is wrong.

My lipos are 3 cells

Each lipo cell has a minimum safe discharged level that is 3v/Cell and 9v for the pack

Each Lipo Pack, according to my Turnigy Accucel-6 ( www.hobbycity.com/hobbycity/store/uploads/ACCUCEL_manual.pdf ) PG. 5 of manual, has a maximum charged level of 4.2v/Cell

Considering those numbers the working range on my 3 cell lipo packs is 1.2v/Cell and 3.6v/Pack

So....(hoping I'm right on this ) that would mean that 50% would be 3.6v/Cell and 10.8v/Pack

and 20% would be 3.24v/Cell and 9.72v/Pack

Ok I hope my logic makes sense to everyone....i really need some help on this as I have never used lopos before and i really don't want to ruin these.

Thanks a lot everyone for all the help so far

[flydiver]

The discharge is not linear. It is a modified 'S' shape.

The [minimum safe discharged level that is 3v/Cell and 9v for the pack] is considered by most lipo aware folks to be no longer prudent. I don't use it.

I have no idea where you got these numbers:
[Considering those numbers the working range on my 3 cell lipo packs is 1.2v/Cell and 3.6v/Pack]
Working range will be about 3.6v-4.2v/cell > 10.8 -12.6v/pack.
I just remember 11.0v. It's easier and keeps some capacity left.

Yes-full is 4.2v/cell > 12.6v for 3S.

Below about 3.6v/cell RESTING there is voltage but essentially no amperage (current)
Study this graph.
www.rcgroups.com/forums/attachment.php?attachmentid=705206

Note that it is a WORKING graph, the lipo is under LOAD. Remove the load and the voltage pops back up. Since we cannot check voltage while flying we have to check while resting. Doing bench testing with monitoring equipment we can see graphs like that.

All batteries have voltage sag under load. How much depends on the load and the battery quality/ability.
You can see some more here:
www.rcgroups.com/forums/showthread.php?t=374446

I use the chart below as a field guide. Numbers are NOT ABSOLUTE-just a guide but better than nothing. There are too many variables for absolute numbers.

Resting (after flight, no load) voltage versus capacity for a 3s pack
11.05V is the 20% left voltage.
11.4V is about 46%

Resting V % Remaining

11.0 --- 17
11.1 --- 26
11.2 --- 30
11.3 --- 37
11.4 --- 46
11.5 --- 50
11.6 --- 57
11.7 --- 63
11.8 --- 69
11.9 --- 77
12.0 --- 83

[d22av]

Oh...after seeing that graph it makes a lot more sense to me!

The whole problem was that i thought the discharge WAS in fact linear.

Thinks a lot for the help.

[flydiver]

Alkalines are liner(ish)
No rechargeable of any sort I know is (maybe lead-acid?). Most are modified S.

When you are flying you get a feel for power after awhile. In the beginning LVC would take me by surprise. Now I can almost tell when I'm down to 50% just by performance.

If you are flying WOT (wide open throttle) the battery sags more and you actually hit LVC more safely.
If you are flying at 1/4 throttle there is little sag in the battery so when it hits LVC it may well be a lot more empty. NiCads did not care too much about this. NiMh are not as happy. Lipo are definitely not happy about low voltage.

That characteristic and resistance to crash damage are a couple of the reasons NiXX can be a better starting option for new fliers. They often ruin a lot of lipos before they figure this stuff out.

[chops1sc]

You need to down prop to a 10X6 from stock. The stock prop and lipo will kill the motor and possibly the ESC. I have recently made the jump to 3s lipo with mine and the power is amazing!

My friend and I have been doing time runs and seeing how much of the battery we are using. With 1800mAh 3s 20C, we are getting 20 minutes of solid flying. Mostly half throttle with the occasional 5-10 second burst of WOT. With the 20 minute flights we are seeing 1600mAh going back into the batteries.

You wont regret the switch, just remember to down prop and remove the little jumper in the ESC/RX and make sure you dont over discharge.


P.S. I just re-read your initial post and saw where you got the 10X6 props, lol sorry!

[killioughtta]

Sept 7, 2009 20:33:08 GMT 1 chops1sc said:

You need to down prop to a 10X6 from stock. The stock prop and lipo will kill the motor and possibly the ESC. I have recently made the jump to 3s lipo with mine and the power is amazing!

My friend and I have been doing time runs and seeing how much of the battery we are using. With 1800mAh 3s 20C, we are getting 20 minutes of solid flying. Mostly half throttle with the occasional 5-10 second burst of WOT. With the 20 minute flights we are seeing 1600mAh going back into the batteries.

You wont regret the switch, just remember to down prop and remove the little jumper in the ESC/RX and make sure you dont over discharge.

A few notes: I just returned from my first few (10) LiPo flights over the weekend. I started out with a GWS 10x6 but after a horrible crash that severed the prop in half, I continued the rest of the flights with the stock 10x8 and had phenomenal performance and no sign of any damage to the motor, ESC or any other electronics. Am I to expect anything different if I continue on the 10x8? The power IS AMAZING!

I have the same flight times with that same battery! what a deal! The SC is five times the fun using just half throttle, as you said. I can almost climb straight up with those 5-secong bursts.

[flydiver]

You can be an experiment in process. 'Conventional wisdom' has cautioned for propping down. It makes sense. The original/7-cell NiMh put out about 10A. With that prop and 3S it put out about 19A > almost DOUBLE! the power.
The GWS HD 10x6 pulls about 12-13A, a modest but noticeable increase.

Everyone who has had the Cub kinda comes to the realization that the electrics are adequate but certainly not sterling or over engineered. So, it seems reasonable that the doubling of power would be a bit much for some component(s). Which one(s)? If the motor fries, well big deal. You coast it in and get a new one for $10. If the ESC fries while flying well >>>> that's likely a different story.


The new Cub LP is just the same old Cub with a 3S and a 9x6 prop - so they down propped for you. OTOH, you can get floats and the prop for the increased load on the float plane is the OLD STOCK 10x8. That's what THEY recommend.

Near as I can tell the ONLY thing they did to the ESC was pull the jumper and change the connector. For awhile I thought just maybe they actually upgraded it. Given all the recent failures (NOT related to the lipo or prop) I think they've done nothing of the sort and actually have a bad batch making the rounds. Typically, they won't admit to anything of the sort but they'll probably make it right in time. They are replacing bad units it appears.

So, enough information to make an informed decision?
Your call, safe and lame or exciting danger?!?!

Report back. Curious people want to know.