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LiPo Charging - new SR120 battery question

Old 08-17-2010, 06:07 AM
  #1  
Jazzman
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Default LiPo Charging - new SR120 battery question

Hey all,

Just picked up my Blade 120sr today (and also picked up a fresh MSR while I was at it). Perhaps this question belongs in a different forum, but as many of us will have both the MSR and 120sr, this seemed an appropriate place:

The 120sr comes with a 500ma 3.7V li-po, plus a single-port Celectra charger. As part of this set-up, there is an adaptor cable from the charger to a JST connection for the battery. The "charger" side of the adaptor is the same size plug used for the MSR / MCX 110/120ma li-po cells.

The new charger is capable of putting out up to .7A, and it specifies that for the 500ma battery included with the 120sr, .7A is the required amperage.

The multi-port Celectra charger which comes with the MSR is rated at .3A.

My goal is to minimize the amount of chargers I carry with me if I want to take both helis somewhere. Do you think it's possible (or safe) to use the multi-port Celectra charger, with the adaptor cable, to charge up the 500ma li-po. I suspect it would take longer to charge the larger capacity battery, but I'm not sure if I would be shortening the life of the battery in some way.

Any thoughts?

Brian
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Old 08-17-2010, 08:34 AM
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vortex05
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You can always charge safetly at a slower rate. Charging past the lipo's recommended c rating will shorted cycle life however.
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Old 08-17-2010, 03:23 PM
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Thanks Vortex,

I guess the charge will just take significantly longer to complete. More time to fly the MSR I suppose.

The LHS didn't have spare batteries for the 120sr in their first shipment.

Brian
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Old 08-17-2010, 04:48 PM
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Generally what I do is measure the size and dimensions and weight then find an equivalent flight pack at hobby city.

Zippy, Turnigy, or Rhino batteries are often many times better than e-flite for less a cost.
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Old 08-17-2010, 06:38 PM
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hobby city - is that the online source? I think it re-directs me to Hobby King.

or are you referring to a local brick and mortar shop here in the GTA (I noticed you're in the same city as me).
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Old 08-17-2010, 06:49 PM
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Yup hobby king.

I haven't found a good local shop I use hobbyhobby and john's hobby when I can
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Old 01-08-2011, 01:10 PM
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Hi, fairly new at all this but has anyone found a turnigy or similar battery pack that will successfully run my 120SR. I got some for the Msr from hobbyking and they work great and last much longer. I'm not sure what 12c and all that actually means so i'm reluctant to plug anything in in case it goes pop. I just want a bunch of spares so i can get cracking. I followed Hobbykings advice for the msr but as yet i cant find one for the SR120.

Cheers

Last edited by Callerz; 01-08-2011 at 01:20 PM. Reason: amended details
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Old 01-08-2011, 02:31 PM
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Nothing will go pop provided you stick to the same voltage/cell count. The 120 SR uses a 3.7V lipo (Single cell). Therefore ANY single cell lipo will be able to safely power it, provided it can handle the amp draw. To find out how many amps a battery can deliver, you multiply the milliamp value by the C rating... so a 12C, 500mah cell is good for (12 x 500ma) which equals 6000ma, or 6A. So any single cell LiPo which can handle at least 6A of discharge current, and is not too physically large for the heli, will be fine. Going higher in Mah rating won't hurt the heli, but it will be larger and heavier so there's a limit to what it will fly with. Higher than neccesary C ratings will mean the battery will be struggling less, and may deliver more power (It's not forcing the heli to take this power, it's just not struggling to deliver what the heli wants). So you may get a bit more 'punchy' performance with a higher C rating. It won't hurt the heli. The only thing that WILL damage the heli, is plugging a battery which is higher voltage than a 1S pack (3.7V nominal). Ie a 2S, 7.4V pack will just burn things up.

So go looking for a cell on HobbyKing which is around the same Mah value (to keep within the same ballpark weight and size) and find one of a C rating which will provide 6A or more of safe discharge current.

Hope that makes sense.
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Old 01-09-2011, 03:41 PM
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Thats great info thanks. Why don't they just put 6amp instead !. I took a look on hobbyking but couldn't find much for 500mah. Too many options and I dont really trust my judgement. I might wait to see what other are buying, cheers
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Old 01-10-2011, 05:39 PM
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I found these, what do you think?
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Old 01-10-2011, 05:39 PM
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http://www.overlander.co.uk/batterie...harge-807.html
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Old 01-10-2011, 11:47 PM
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That looks fine. Battery selection really isn't that tricky, and often finding the best cell is just trial and error.

The reason for mentioning C rather than actual amp draw, is that allowable amp draw, as I mentioned before, is related to capacity as well as C rate.

So looking at just C rate assures you're doing an apples-to-apples comparison. When you see a cell rated to 30C, you know you're getting a decent quality cell (provided it lives up to the claims). Whereas a value like '6 amps' could mean anything from a very high C rate, with a small capacity cell, to an exceedingly low C rate, on a higher capacity cell. It's much harder to get it through your head which cell is rated for a harder discharge, in relation to the capacity.
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Old 01-11-2011, 01:59 AM
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It's true also to keep in mind Higher C cells generally will last longer because it's harder to reach those high amp draws and thus your not damaging the cells. Heli's especially that tend to just go full or close to full load the entire flight it's a good idea to buy a over C rated battery if you want to see more than a year of life out of them.
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Old 01-11-2011, 10:20 AM
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Great , that's it then, might.have to buy a load. I haven't checked the physical dimension yet. Do u know if overlander are reputable?
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Old 01-12-2011, 02:03 AM
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I've got no clue. What you might want to do, (given the relatively low cost of cells), is perhaps buy one of each type you're considering... try them all, decide on one you like, and then buy more of that one if you still want more cells.
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Old 01-12-2011, 07:53 AM
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I will, I haven't had much luck in finding any others yet, I ordered 2 yesterday so ill report back on my very amateur findings. I'm not the most efficient flyer yet so it could all end in tears. Well see. I'll keep looking for more in the meantime. I thought hobby king would have something!
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Old 01-12-2011, 02:28 PM
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Ok so they arrived in super fast time, they weigh .9 of a gram more and are a tiny bit fatter. They do fit tho. They don't have the plastic end cap so I'll have to guess on the balance. I'll report back later once I've had a good go.
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