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Old Oct 26, 2004, 08:36 PM
Time Pilot is offline
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What's the difference between these 2 batteries?


I was about to order some GWS batteries from Tower and found that the batteries recommended for the EStarter (300 Version) are discontinued! They do have another pack and was wondering what the difference is besides the obvious size, weight and extra 20mah.

The question is whether the BP7N750AAA will deliver ample amps for my Estarter.

Discontinued Pack:BP7N730AAA (8.4V AAA nimh 730mah) (L X W X H): 72x10.5x46(mm) / 2.8x0.41x1.8(in) Weight: 93(g) / 3.30(oz)
http://www2.towerhobbies.com/cgi-bin...?&I=LXHHU3&P=7


Available Pack: BP7N750AAA (8.4V AAA nimh 750mah) Length: 2-7/8" (73mm)Width:1/2" (13mm) Height: 2" (51mm) Weight: 4oz (115g)
http://www2.towerhobbies.com/cgi-bin...4&I=LXHHU5&P=K

Thanks.
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Old Oct 27, 2004, 02:11 AM
Steven N is offline
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[FONT=Arial]Before I updated my Estarter to brushless and lipo, I prefered to step up the battery to 9.6V AAA and at least 750mA. The performance was much better than 8.4v.
Old Oct 27, 2004, 02:35 AM
busybee is offline
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two left feet
Quote:
Originally Posted by Time Pilot
I was about to order some GWS batteries from Tower and found that the batteries recommended for the EStarter (300 Version) are discontinued! They do have another pack and was wondering what the difference is besides the obvious size, weight and extra 20mah.

The question is whether the BP7N750AAA will deliver ample amps for my Estarter.

Discontinued Pack:BP7N730AAA (8.4V AAA nimh 730mah) (L X W X H): 72x10.5x46(mm) / 2.8x0.41x1.8(in) Weight: 93(g) / 3.30(oz)
http://www2.towerhobbies.com/cgi-bin...?&I=LXHHU3&P=7


Available Pack: BP7N750AAA (8.4V AAA nimh 750mah) Length: 2-7/8" (73mm)Width:1/2" (13mm) Height: 2" (51mm) Weight: 4oz (115g)
http://www2.towerhobbies.com/cgi-bin...4&I=LXHHU5&P=K

Thanks.
Either of those will work for the 300 version, although an 8 cell (9.6v) pack will have more kick. The 20mah doesn't seem worth the extra 22g! I wonder why they discontinued the other pack? Would be nice if you could find it somewhere cheap...
Old Oct 27, 2004, 02:39 AM
busybee is offline
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two left feet
GWS Expert seems to have both.

http://www.gwsexpert.com/index.php?c...3d8cf2d495eff2

If you are willing to try lipo, the 2s lipo pack should be perfect! 1050 at only 1.68oz.
Old Oct 27, 2004, 04:54 AM
GWS4JOYCE is offline
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I have checked your question with our sendior flyer, and provide our answers as below:

GW/BP7N750AAA (8.4V750mAh) will work fine with GWS ESTARTER (300 version). If you would like to have more power, you can use GW/BP8N750AAA (9.6V750mAh).

However, the best choice is to use Li-Poly batteries (7.4V1050mAh).
Model: GW/BP2S1P1050
Size (L x W x H): 63x37x10
Weight: 1.68oz
Connector: JST
Max. charging rate: 1C (C:Battery capacity)
Max. discharging rate: 6C (C:Battery capacity)
Old Oct 27, 2004, 07:09 PM
rkhoo is offline
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Joyce,

What is the max save discharge amp from the 8cell battery GW/BP8N750AAA ? Typical 300C setup with 1080 at 9.6V will want about 9 to 10A. Will the GWS 730mAh (GW/BP8N730AAA) by Sanyo has better discharge curve?

As a side note, what is GWS's recommendation in term of best practiced saftey procedures for your line of Lipo battries? Storage, Charinging, discharge, etc.

May be too many question...

Regards.
Old Oct 27, 2004, 10:29 PM
Time Pilot is offline
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Busybee,

Yes, I noticed the small increase in mah per gram. I'm not thrilled about the extra weight, but the price of the packs are considerably less. If they work, I can get almost 3 750 packs for the price of 2 730mah packs.

Thanks Joyce for the quick reply. I am a bit concerned that these packs will drop voltage prematurely and cause continual cutoffs from the ESC. Still wondering why they are so cheap. You know what they say, you get what you pay for. But if you say they are okay....
Old Oct 28, 2004, 02:15 AM
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I do not think you will have a problem with the AAA packs on a 300C motor, especially with something like a 5.3:1 ratio and 9x7 prop the 300 E-Starters would typically come with.

It is the 350C, which is a hotter wind (more RPM/V), that might have a problem with the high internal resistance (and hence lower discharge rate) of the AAA cells. But with the 300, you shouldn't have a problem with the ESC cutoff on any of those packs. And while those packs are not overpriced, they aren't really cheap either.

If you plan to replace your motor with a 350 when it wears out, I'd go with the GWS 1300 lipos, or some 2/3AA cell packs. Check out CBP (same as KAN) cell packs (650 and 1050 nimh) at cheapbatterypacks.com.
Old Oct 28, 2004, 04:35 AM
GWS4JOYCE is offline
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Quote:
Originally Posted by rkhoo
Joyce,

What is the max save discharge amp from the 8cell battery GW/BP8N750AAA ? Typical 300C setup with 1080 at 9.6V will want about 9 to 10A. Will the GWS 730mAh (GW/BP8N730AAA) by Sanyo has better discharge curve?

As a side note, what is GWS's recommendation in term of best practiced saftey procedures for your line of Lipo battries? Storage, Charinging, discharge, etc.

May be too many question...

Regards.

The maximum discharging rate for GW/BP8N750AAA is 10C (C: Battery capacity).

Handling precautions and prohibitions for Lithium-Polymer batteries:

General information:

Lithium-Polymer ( abbreviation : LiPo) batteries require particularly careful handling. Mishandling these batteries may lead to explosions, fire, smoke and a risk of poisoning.

Donít series or parallel connect battery packs since the cell capacities and the charging condition may be too different.

Therefore , battery packs we supply are selected.

1. Charging

1-1 Charging voltage :

These batteries should charged with a charger that is specifically designed for LiPo cells, charging at above 4.25V per cell , which is the absolute maximum voltage. It must be strictly prohibited as higher voltage causes permanent damage to the cells and causes fires.



1-2 Charging current:

The GWS LiPo batteries can be charged at a rate of max. 1.5C (1C corresponds to the cell capacity).

Charging with higher current than recommended may cause damage to cell performance and safety features deeply, and can lead to heat generation or leakage.



1-3 Charging temperature:

These batteries shall be charged within a range of temperature 0℃ to 50℃. If these batteries are charged at the temperature out of the specified range, leakage, heat generation or other damage may be caused.



1-4 Prohibition of reverse charging :

Reverse charging is prohibited. These batteries shall be connected correctly. The polarity has to be confirmed before you make wiring.The reverse charging may cause damage to the cells which may lead to lose cell performance, and may damage to the cell safety which can lead to heat generation or leakage.

2. Discharging

2-1 Discharging current :

The GWS LiPo batteries can be discharged at continuous currents of around 10C (with 70~80% capacity).High discharging current may reduce the discharging capacity remarkably or cause overheats.



2-2 Discharging temperature :

These batteries shall be discharged within a range of -10℃ to 60℃.

At a temperature of -10℃ or less, the battery will show a significant decrease in discharge capacity.

The battery temperature during the discharging should not exceed 70℃.



2-3 Over-discharging

Normally, LiPo batteries start to discharge at 4.2V and terminate at a cut-off voltage of 3.0V.

Discharging these batteries to a point below 2.5V per cell causes permanent damage to the cells, and this must be avoided.

3. Shipment

For transport of lithium cells and batteries, the battery shall be shipped in 30% charged state for the safty reason.

All GWS LiPo are charged in 30% charged state at the original manufacturer.

Please refer to united-Nations UN3090.


Best regards,
Old Oct 29, 2004, 02:41 AM
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Joyce,

You wrote: "The maximum discharging rate for GW/BP8N750AAA is 10C (C: Battery capacity)"

Is the 7 Cell pack of the same is also rated at 10C discharge rate?

According to your site, the 350 with a 8.4 Volt battery, 5.3:1 gearing and a 10 x 6 prop pulls max 8.8 amps. The 300 with an 7 cell battery and a 9 x 7 prop pulls 7.7 amps. Either can't be good as the 8 cell pack, at least, is rated for max 7.5 discharge rate!

If I purchase that pack, are you sure I'll still be a happy GWS customer?
Last edited by Time Pilot; Oct 29, 2004 at 03:08 AM.


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