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Batteries, again

9617 Views 85 Replies 26 Participants Last post by manokaiser, Jul 15, 2011

emu26

Discussion Starter · Feb 28, 2011

Sorry but I find the need to discuss batteries yet again. I know, I know, hundreds of threads etc etc but with the lflex available and the best pairing being a single xml and single cell li-ion / li-po I've been looking for some 3.7v batteries.

DX and KD obviously have loads of 18650 batteries and picking one out of the bunch as better quality than another is liking finding the proverbial needle. (happy for recommendations here people) and then you have to fashion a holder or get something like sdNatives and waterproof that

Anyway what has got me thinking is lots of RC hobby places sell 2, 3 and 4 cell batteries with reasonable capacity but I can't find a single cell one above about 850mAh and that obviously just doesn't cut it for run times. Why can't I find them? Where are they all, surely thses bigger packs are made up of 2, 3 or 4 cells of capacities between 2000mAh and 2600mAh so why can't I find any?

I'm trying to avoid places like batteryspace because of the now prohibitive shipping costs.

If I buy a 3 cell battery like this one from hobbyking can I pull it apart to get three 2650mAh 3.7v batteries? what do I need to be careful of? What do i need to do to get three individual, usable batteries?

Any other suggestions?

FTR this is the only large capacity single cell I can find

1 - 20 of 86 Posts

bravellir

· #2 · Feb 28, 2011

I think that's because most 3.7 v rc machines (helis, plane, commands) are very sensitive to weight or have very low consumption.

You can go the other way around. Buy 4 850mAh cells and put them together as a large 3,7v 3.4 mAh pack

I made a few batteries using a single 18650, water proof and its rather easy and cheap to build. Even if you use a pair of protected 18650, you can put together a 3,7v +-5000 mAh pack without any holder at all and that can be charged by a "vulgar" 18650 charger without problems with balancing ( not sure about the balancing but if I'm wrong someone will set me right )

mfj197

· #3 · Feb 28, 2011

emu26, I think you can pull apart an RC battery with no problems at all. I've never done it as I've needed my packs intact, but I can't think of any reason you couldn't. The only thing you'll need to do is disconnect the balancing leads. Of course they aren't protected, but then the LFlex should take care of that.

The reason you can't find large capacity single cells is as bravellir says. There are very few motors which run off a single lipo, and those that do are very limited in the power they generate and therefore the lifting capability they have. Therefore any single cells need to be very lightweight - the likes of the Silverlit Picoo Z use a 3.7V but it's absolutely minute. Most motors for larger helicopters use 7.4V or 11.1V as a minimum, simply to provide the power required.

By the way, I've been using quite a few of the black and red Trustfires from DX and they've been pretty good.

MtbMacgyver

· #4 · Feb 28, 2011

Yes, you can pull a larger RC pack apart. It's really very easy. You just have to be really careful not to short the cells during the process. The lflex really doesn't provide battery protection. Personally, I would spend the few bucks for a protection PCB to put inside the pack. You can also take something like a 3s 2200mah pack and reconfigure it to a 3p 6600mah pack.

Personally, I would also want to put lipo cells in some kind of hard case for bike light use, since they are very susceptible to puncture damage. Actually, I use 18650 for bike light use because of the physical protection of the metal case. I use lipo packs for my RC planes and helicopters. I've been using the Panasonic 2900mah 18650 cells with my lflex and XML single light wired into a 2p pack which makes it a 3.7v 5800mah pack. So far I'm really happy with that setup. Extremely small and light and gives runtime close to 2 hours on full and 4 hours at 1.4amp which is a very use-able amount of light. It's light enough that I'm experimenting with the battery on the helmet, which is something I never thought I would do.

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klynk

· #5 · Feb 28, 2011

7,4 V 5000 mAh LiPo:
http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9437
There are 2 long flat 3,7 V 5000 mAh batterys inside. BUT they're without protection.

Vancbiker

· #6 · Feb 28, 2011 (Edited)

I'm not sure how much they will charge for shipping to the lucky country, but these are looking interesting to me.

http://www.allelectronics.com/make-a-store/item/LBAT-55/3.7V-2650-MAH-LI-ION-BATTERY/1.html

MtbMacgyver

· #7 · Feb 28, 2011

Vancbiker said:
I'm not sure how they will charge for shipping to the lucky country, but theses are looking interesting to me.

http://www.allelectronics.com/make-a-store/item/LBAT-55/3.7V-2650-MAH-LI-ION-BATTERY/1.html

I've ordered lots of stuff from All Electronics in the past. They've been around forever and I have always been happy dealing with them. I don't know if they ship internationally or not.

There isn't a bunch of detail in that spec sheet, but it sounds like the "charge control board" is simply a thermistor on the little connector PCB soldered to the leads of the cell. There is a third wire in the pack connector that I assume is connected to thermistor such that the host device or a protection PCB can measure cell temperature. A high quality protection PCB will use the thermistor to prevent pack charging when the pack is too cold or hot.

P220C

· #8 · Feb 28, 2011

I have some 18650s on order from AW to use in my lFlex build. I think they were ~$19 each, with a total of $4.50 in shipping (no haz-mat fees).

There are supposed to be built with the new 2900 mAh Panasonic 18650 along with the PCB. I've used AW 17670s in the past with good results, and I expect the same here.

I really wanted to go with a Li-Po pack, but the weight and hassle of physically protecting the from puncture made the single 18650 make better sense in this instance.

I am under the impression, that if you are quick with it, that you can solder leads directly to the positive pip, and to the back plate of the PCB (seen as the negative post of the cell) of these protected 18650. Obviously, one could also damage the cells or PCB with careless soldering, but I think (hope?) I'm going to be OK.

Toaster79

· #9 · Feb 28, 2011

I've ordered this one to rip it apart for single cells.

desolder

· #10 · Feb 28, 2011

I believe all-battery.com doesn't charge the ridiculous haz-mat fees which batteryspace does, and their prices are comparable.

If you want to go with DX, the Trustfire True 2400 cells with the red and black label are generally considered the best they have to offer.

Like MtbMcGuyver, I also prefer 18650's over Li-po's because of the protection from the steel can. I use a 4-cell pack which is hot-melt glued together, then dipped three times in Plasti-Dip to give it a tough, waterproof coating. I use a TwoFish LockBlock to strap it underneath my handlebars.

mattthemuppet

· #11 · Feb 28, 2011

I'm happy with the 6 Uniquefire unprotected 2500mAh cells I got from DX, capacities were in the 2250-2290mAh range, which isn't bad. I bought 6 grey 2500mAh Trustfires, again from DX, whose capacities were 2230-2270mAh. Both types charge and discharge fine at high rates on my AC6 charger, so they seem decent quality, although time will tell. I'm using Digikey 18650 holders, soon to be balance wired and plastidipped.

One thing that seems clear from CPF about DX batteries is that there's no point paying for the higher capacities as the fudge/ lie factor is even higher. If you need >2500mAh real capacity, you're better off with Sanyo/NCR/Samsung cells.

emu26

Discussion Starter · #12 · Feb 28, 2011

Thanks for all the replies and recommendations.

As always tends to be the case when post a "Where can I find" type thread, I find. Did another fleabay search and came with a couple of options similar to this

http://cgi.ebay.com.au/Team-SILVERB...ntrolled_JN&hash=item1c19246fdf#ht_2178wt_905

yetibetty

· #13 · Mar 1, 2011

Free woldwide shipping, bigger than 18650 but a couple of these in parallel should do the job:

http://www.4sevens.com/product_info.php?cPath=53_57&products_id=2585

langen

· #14 · Mar 1, 2011

bravellir said:
.... you can put together a 3,7v +-5000 mAh pack without any holder at all

Care to share some details?

It's the "without any holder at all" part I'm interested in...

Ofroad'bent

· #15 · Mar 1, 2011 (Edited)

Here's a battery pack from All-battery online for a reasonable price, wired and protected:

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=290444000004&ssPageName=STRK:MEWAX:IT

I just got one of these holders, wired for 1S2P with protection: They appear to be identical to the Batteryspace ones:
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=220714539203&ssPageName=STRK:MEWAX:IT

and I plan to use the black-and-red Trustfire Dx batteries, once they arrive. I also have some of the unprotected Digikey battery holders, but the protected ones are smaller and pre-wired.

I just couldn't source any plasti-dip near where I am in Caledon, and the shipping was murderous online, so I got some self fusing silicone tape and will dunk or paint on liquid electrical tape which I did manage to find.

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bravellir

· #16 · Mar 1, 2011

langen said:
Care to share some details?

It's the "without any holder at all" part I'm interested in...

What I mean is that since you don't need to worry about balancing, you can get 2 protected 18650 cells, wired them in paralell, solder, glue and water proof them with plasti-dip or tape and you can charge the pack with a simple 18650 charger .
You dont need the holder because you don't have to pull them apart from the pack to charge.

I did a few of those packs.

http://forums.mtbr.com/showpost.php?p=7010455&postcount=1
Here ( video 3,4 and 5 ) you can see an example I did but with a single cell. You dont want the button if you are using the lflex.

Ofroad'bent

· #17 · Mar 2, 2011

Watch out for ordering battery holders from Digi-key if you're not in the US.

I ordered a couple of Reginas and some $2 battery holders. The shipping was a horrific $35 on the first order, and they had the chutzpah to charge me another $30 to ship 2 Reginas. $65 shipping on a $9 order. Sigh- live and learn.

The protected battery case I got on eBay was $10 including shipping, and it got here fast.
That's the way to go.

emu26

Discussion Starter · #18 · Mar 2, 2011

Thanks for the info and feedback Ofroad'bent.

If I were to use that holder can you use protected cells or should they be unprotected?

If I were to tape and plastidip two cells into that holder what could I use to charge them? Do I need to be concerned about balancing cells in parallel as I would in series?

savagemann

· #19 · Mar 2, 2011

It's always been my understanding that parallel cells balance themselves.

emu26

Discussion Starter · #20 · Mar 2, 2011

I wasn't sure if it was possible for one to drain down or charge at a faster rate than the other and thus leading to problems

1 - 20 of 86 Posts

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