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kamondelious
01-30-2010, 10:49 PM
Hi All,

I'm in the market for a LiPo charger & batteries for my project, but am just learning about the glory of LiPo batteries.

This seems like a good bit of information to me :
http://thetoyz.com/forums/index.php?showtopic=26695

I am planning to go with two 11.1V 2200mAh LiPos at around 20C-25C.

I'd like to hear about people's brand preferences and why. Or even just LiPo experiences in general.

Yay learning. :D

Cheers

billyzelsnack
01-31-2010, 12:19 AM
This is the best place to do research on lipo chargers..

http://www.rcgroups.com/batteries-and-chargers-129/

mannyr7
01-31-2010, 12:57 AM
The first question is what are you planning to running off this?

kamondelious
01-31-2010, 01:46 AM
Hi billyzelsnack,
Thanks for the link. I've been following your uninterruptable LiPo thread with great interest. http://forums.trossenrobotics.com/showthread.php?t=3799
I am also keen to see what Jon's new board is like.

Hi mannyr7,
My project is a Bioloid Humanoid. I started a blog about my endeavors with it here :
http://forums.trossenrobotics.com/blog.php?u=2294

JonHylands
01-31-2010, 10:29 AM
Just for reference, I use an 8C Lipo (2000 mAh, 3S) to power Roz. With all 12 servos going at once, the maximum current draw I've seen is about 4 amps.

20-25C is way overkill for a 2000 mAh battery for a bioloid-based humanoid... With an 8C battery (which is about 1/2 the price), you're looking at being able to draw 16 amps, which is a lot of power, certainly way more than I need. Perhaps Snoopy's CPU draws a lot of power, but from what I've seen they are pretty efficient, so I can't see it.

- Jon

kamondelious
01-31-2010, 10:59 AM
Excellent point Jon.

My thinking was simply that since I'm using 27 servos with a max rated draw of 900mA each, I'd want at least 20C to not have issue with many of them under load at one time. Which is probably not likely to happen.

I haven't purchased any LiPo's just yet though. ;)

billyzelsnack
01-31-2010, 11:19 AM
There are two C ratings for batteries. Continuous and burst. Manufacturers often fudge with the truth on both. The only way to really know ahead of time is to look in the forums and see the actual graphs. The people in that rcgroups battery forums are completely ridiculous about such things and that's why it is such a great resource.

When walking all 18 AX-12's in my robot pulls an amazingly low 2.5 amps continuous. That can burst, but if it does it is for a very short time. You can always protect your batteries with a fuse too. So a proper 2000mah 8C continuous ( that's 16 amps continuous ) should be fine even with 27 servos. If you put the same batteries in parallel it'll double that too.

JonHylands
01-31-2010, 11:20 AM
I would be very surprised if you ever draw more than 10 amps with Snoopy. You should invest in one of these:

http://www.all-battery.com/valtagewattmeter01019.aspx

It will tell you exactly how much current your robot is consuming at any given point in time (while you have it plugged in)...

- Jon

kamondelious
01-31-2010, 12:09 PM
billyzelsnack & Jon,

Thanks for the excellent input!

Now I get to re-consider my LiPo plans. This is great. The ones I was looking at are listed to weigh around 165g. The stock bioloid battery is 242g, so I was going to be over that by 90g which I didn't like too much. Now I get to explore lighter battery options. I love it.

Thanks again

:D

JonHylands
01-31-2010, 04:17 PM
billyzelsnack & Jon,

Thanks for the excellent input!

Now I get to re-consider my LiPo plans. This is great. The ones I was looking at are listed to weigh around 165g. The stock bioloid battery is 242g, so I was going to be over that by 90g which I didn't like too much. Now I get to explore lighter battery options. I love it.

Thanks again

:D

This is the battery I use:

http://www.commonsenserc.com/product_info.php?cPath=37_35&products_id=48

Not much lighter, but only $24...

- Jon

kamondelious
01-31-2010, 05:09 PM
Smaller form factor is good too.

Thanks again Jon.

Cheers!

billyzelsnack
01-31-2010, 06:00 PM
I've been considering using "transmitter" lipo packs. They are usually 2C, but I've seen higher.

CSRC has a 4C one..
http://www.commonsenserc.com/product_info.php?cPath=37_27&products_id=32
146 grams for 2500mah is pretty light and that's even a CSRC pack that usually are quite heavy. For instance.. A Thunder Power 15C 2100mah is 142grams and they are the lightest brand as far as I know.

Here's another. This one is 3C. ( Not that you can actually trust that number. )
http://hobbycity.com/hobbyking/store/uh_viewItem.asp?idProduct=7346&Product_Name=Rhino_2620mAh_3S_11.1v_Transmitter_Li poly_Pack

I was thinking that if I could get a 3000mah 2C pack it'd be just about perfect for size/weight and fine because 6 amps continuous is double my usual operating load. I am going to incorporate a current sensor at some point soon so I can see what the bursts really are. My meter gives mins/max, but I don't really trust it 100% and realtime graphs are so much cooler anyway.

kamondelious
02-01-2010, 06:31 AM
Here's the pack I was looking to get a couple of :
http://cgi.ebay.com/2200mAh-25C-30C-11-1v-3s-LiPo-Battery-Align-Trex-450-RC_W0QQitemZ170399981729QQcmdZViewItemQQptZRadio_C ontrol_Parts_Accessories?hash=item27aca160a1

I mean at $9 it's tempting to get just for the crap shoot that they turn out to be alright. The seller has a good rating, so maybe.

He's also selling this charger :
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=170423893346

I know cheap has a nasty tendency to === bad in this department, but it's tempting. I read a few reviews for that charger that said it was decent. Sounds like it's just some generic type that gets re-branded a bunch.

I think hobbyking.com is blocked in Hong Kong/China. I can never seem to view anything on their site. Nothing but 404's. Even if I go the main page or hobbycity.com directly. :mad:

That transmitter pack looks pretty sweet too. Are those 11.1V? Sorry for the ignorance. I mean I would assume so since you're thinking about trying them out, it just isn't listed.
2500mAh and 142g is a pretty nice bundle.

Cheers and thanks again!

billyzelsnack
02-01-2010, 08:27 AM
The battery is probably fine for our uses. Especially if you don't have to pay that high shipping rate since you're in HK. A lot of the cheapo lipos are just under rated and not so good for RC, but fine for what robots. I'd expect in actuality it be not exactly as advertised.. So.. under capacity, under C rating, larger in size, and more weight.. It'd still be the same voltage though. haha.

http://www.bonanzle.com/booths/heliquarter/items/2x_2200mAh_25C_30C_11_1v_3s_LiPo_Battery_Trex_450_ _164g

Is hobbyking.com blocked for you?

As for that charger.. It's been around for a long time. Look at the reviews for it on RC groups. There really is no technical reason why a charger needs to be expensive.

fyi, that same guy sells here..
http://www.bonanzle.com/booths/heliquarter/items/2x_2200mAh_25C_30C_11_1v_3s_LiPo_Battery_450__T_pl ug_

kamondelious
02-02-2010, 06:37 AM
I saw the bonanzle booths link in another thread and contacted the guy that runs it. He is willing to give me a deal on shipping. He also pointed me to his ebay store when I inquired about chargers.

Yeah no hobbyking.com for me. :(

Maybe I'll contact that guy again and see if I can swing a deal. :)

kamondelious
02-16-2010, 11:32 AM
Yeah, got what seems like an alright deal to me.

Two 11.1V 2200mAh 8C LiPo's, that B6 charger, a fireproof LiPo bag and a LiPo tester for about $70US. All from that guy selling out of Hong Kong.

Are the fireproof bags a worthy investment? I don't have a garage or anything and can't exactly charge it outside. Figured I'd best be safe than sorry.

The LiPo's each weight in at 112.5g which is 225g for the pair, which comes in at 17g lighter than the stock 242g Bioloid battery pack. That's a definite score there.

What's an acceptable variance in voltages between cells in a pack?

:D

DresnerRobotics
02-16-2010, 11:48 AM
With a balance charger it will bring all your cells to 4.2v, so you shouldn't have to worry about it. I don't bother with the charging bags but I guess it couldn't hurt.

That deal you got is an absolute steal. The B6 balance chargers are rock solid.

kamondelious
02-16-2010, 11:51 AM
Excellent to know on all points, thank you!

:D

Robert
02-18-2010, 12:37 PM
I'm a big fan of hobbyking.com for batteries. As for chargers, we have a few of these: http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5548&Product_Name=IMAX_B6_Charger/Discharger_1-6_Cells and they seem to balance charge quite well.