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Old Dec 19, 2014, 07:05 AM
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Which Battery !!!

Hello Everyone,

Merry Christmas.

I have brought a small electric glider with a Grauper Speed 400 Plus motor in with a BEC, Brake fitted to the rear of it, it also says6 ... 9'6v/15a and it has a Cam prop 15-8 or 6-3", what size battery would i need to power it ?

Thanks.
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Old Dec 19, 2014, 07:26 AM
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It looks like it is this one, with Kv around 3000. 2S max! it was designed for 6 or 7 NiCd. Even on 2S it will likely get fairly warm if you run continuous full throttle
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Old Dec 19, 2014, 07:46 AM
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Originally Posted by scirocco View Post
It looks like it is this one, with Kv around 3000. 2S max! it was designed for 6 or 7 NiCd. Even on 2S it will likely get fairly warm if you run continuous full throttle
Yes that's the 1 by the looks of it

So a 2s i will get, will a Ripmax Pro Peak Prodigy 12v charger be ok with a Lipo ?
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Old Dec 19, 2014, 03:55 PM
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Only if it specifically says on the charger that it can charge LiPo batteries. If there is no explicit mention of LiPo capability, do not assume!
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Old Dec 20, 2014, 04:37 PM
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I would be worried about running such a high kV motor with a folding prop.
Most of mine are around 900 to 1200 kV.
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Old Dec 20, 2014, 07:32 PM
Lou
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Yep ... kind of leary of the high kV on that folding prop. Not to mention that a brushed motor can be kinda hard on a lipo.

What is the plane that you are flying? Any pictures?
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Old Dec 20, 2014, 07:49 PM
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I can't see where the product details or instructions say it's a 3000kv motor. There is one spec - No-load speed 18000 m-1 - whatever m-1 means (?). It does specify that it's for 5 - 8 cells (6v - 9.6v) so perhaps the kv is 18000/max voltage - i.e. 18000/9.6 = 1875kv.
Be that as it may, I used to run a similar speed 400 on 7 or 8 cells nimhs with grey Graupner 6x3 folding prop & sometimes on a non folding Master 6x4 ic prop. Current draw was around 10.2A with 7 cells & 12A with 8.
I used this set up in Henry, an OD model, that had previously flown using a Cox 049. With EP the model was about 100g heavier & overall the performance was similar. When it was Cox powered the model was flown more often as a slope soarer with prop removed than it was flown under power. Henry was published as a free pull out plan in the old Silent Flight mag about 15 years ago.

If you use the combo with 2s lipo the current draw (& therefore power) would be well down compared with using 7 or 8 nimhs but it could be improved by using a larger prop to get the current draw up to around the 12 - 15A range. The achievable power with 2s lipo would be about 15 - 20% down on what it would be with 7 or 8 nimh cells but there would be a significant weight saving.

The 8 cell nimh batteries I used were 1050mAH & weighed about 180g, for the equivalent energy from 2s lipo would need to be around 1300mAH but would only weigh about 75g. This should allow about 5.5 - 6 mins run time per charge which could be upwards of 30 mins flying time depending on thermic conditions etc.

The Pro-Peak Prodigy is able to charge lipos, AFAIK there were two versions . The first could only charge up to 3s lipo the second version could charge up to 5s but neither had a cell balance function. I used the early version without any problems (still do occasionaly).

As an addendum Henry was later converted to a 1100kv outrunner weighing 57g using 3s 2500mAh early lipo that were only rated at 8C (but only weighed the same as the nimhs) driving a 9x5 folder. Performance was transformed & a single charge was enough for over 90 mins flying time with no thermal assistance.
Personally I'd dump the Speed 400/esc combo & replace it with a 50 - 70g 1000 - 1500 kv outrunner & 3s lipo.
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Old Dec 20, 2014, 09:17 PM
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Personally I'd dump the Speed 400/esc combo & replace it with a 50 - 70g 1000 - 1500 kv brushless outrunner & 3s lipo.

(fixed it for you..)
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Old Dec 21, 2014, 01:27 AM
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Originally Posted by patmcc View Post
I can't see where the product details or instructions say it's a 3000kv motor. There is one spec - No-load speed 18000 m-1 - whatever m-1 means (?). It does specify that it's for 5 - 8 cells (6v - 9.6v) so perhaps the kv is 18000/max voltage - i.e. 18000/9.6 = 1875kv.
Be that as it may, I used to run a similar speed 400 on 7 or 8 cells nimhs with grey Graupner 6x3 folding prop & sometimes on a non folding Master 6x4 ic prop. Current draw was around 10.2A with 7 cells & 12A with 8.
I used this set up in Henry, an OD model, that had previously flown using a Cox 049. With EP the model was about 100g heavier & overall the performance was similar. When it was Cox powered the model was flown more often as a slope soarer with prop removed than it was flown under power. Henry was published as a free pull out plan in the old Silent Flight mag about 15 years ago.

If you use the combo with 2s lipo the current draw (& therefore power) would be well down compared with using 7 or 8 nimhs but it could be improved by using a larger prop to get the current draw up to around the 12 - 15A range. The achievable power with 2s lipo would be about 15 - 20% down on what it would be with 7 or 8 nimh cells but there would be a significant weight saving.

The 8 cell nimh batteries I used were 1050mAH & weighed about 180g, for the equivalent energy from 2s lipo would need to be around 1300mAH but would only weigh about 75g. This should allow about 5.5 - 6 mins run time per charge which could be upwards of 30 mins flying time depending on thermic conditions etc.

The Pro-Peak Prodigy is able to charge lipos, AFAIK there were two versions . The first could only charge up to 3s lipo the second version could charge up to 5s but neither had a cell balance function. I used the early version without any problems (still do occasionaly).

As an addendum Henry was later converted to a 1100kv outrunner weighing 57g using 3s 2500mAh early lipo that were only rated at 8C (but only weighed the same as the nimhs) driving a 9x5 folder. Performance was transformed & a single charge was enough for over 90 mins flying time with no thermal assistance.
Personally I'd dump the Speed 400/esc combo & replace it with a 50 - 70g 1000 - 1500 kv outrunner & 3s lipo.
m-1 is per minute. While the range says 6=9.6V, that particular motor is known as a 6V S400, hence about Kv of 3000 for 18000 rpm at 6V no load. There are older motor calcs that still have the specs for brushed Graupner Speed motors. S400 6V cat #3321 is listed as 3075

A 6x3 folder on s400 used to be routine, eg it was the stock prop on the Graupner Terry (circa 2000) for 6 or 7 cells, and was used in much more sophisticated setups. And it won't be turning 18000rpm loaded on 2S , maybe 13-14000.
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Old Dec 21, 2014, 02:40 PM
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Originally Posted by scirocco View Post
m-1 is per minute. While the range says 6=9.6V, that particular motor is known as a 6V S400, hence about Kv of 3000 for 18000 rpm at 6V no load. There are older motor calcs that still have the specs for brushed Graupner Speed motors. S400 6V cat #3321 is listed as 3075

A 6x3 folder on s400 used to be routine, eg it was the stock prop on the Graupner Terry (circa 2000) for 6 or 7 cells, and was used in much more sophisticated setups. And it won't be turning 18000rpm loaded on 2S , maybe 13-14000.
Thanks for the explanation. Just had another look at my old notes on this motor, using 8 cells with a little plastic Gunther I recorded 14400rpm but not the current. I think I may have been alarmed that the revs were to much for the Gunther & closed the throttle in a hurry.
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Old Dec 21, 2014, 02:42 PM
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Originally Posted by 320pilot View Post
Personally I'd dump the Speed 400/esc combo & replace it with a 50 - 70g 1000 - 1500 kv brushless outrunner & 3s lipo.

(fixed it for you..)
Do you think it needed fixing ?
I can't think of any brushed outrunners, can you ?
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