7 cell or lipo
01-09-2007, 01:07 PM
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7 cell or lipo
would a gp 3800 7 cell battery give me more speed than say a 4000 mah lipo battery i know that lipo are better all around but for speed which is better? thanks
01-09-2007, 02:32 PM
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RE: 7 cell or lipo
A 2 cell lipo will give you a nominal voltage of 7.4 V so will likely be a bit slower than a 7cell nimh pack (8.4v). A 3S lipo will be 11.1v and so be considerable faster. But there are other things to consider. First, a fully charged 2S lipo will top out around 8.1v (give or take a tenth of a volt) while a 7 cell nimh pack will top out at 9.8v but the nimh will start to fall off much quicker than the lipo. The lipo will keep a pretty constant voltage (and thus performance) untill it is nearly discharged. Then there is the weight difference. A nimh pack is considerable heavier than a lipo. Lipo's do have some downsides though. You need an ESC that can be programed to quit drawing current when pack voltage drops below a certain point. The exact voltage depends on the pack configuration and voltage but is usually 3.0v/cell. You also need a lipo charger, you CANNOT use a nicad/nimh charger (not easily anyway). And Lipos are very finiky about overheating and charging. Improper charging and / or inattention can lead to explosions and fires.
If you're willing to deal with them though, lipos are great batteries. Lots of power, a great discharge curve and light weight too.
If you're willing to deal with them though, lipos are great batteries. Lots of power, a great discharge curve and light weight too.
01-09-2007, 03:37 PM
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RE: 7 cell or lipo
ORIGINAL: DaveG55
A 2 cell lipo will give you a nominal voltage of 7.4 V so will likely be a bit slower than a 7cell nimh pack (8.4v). A 3S lipo will be 11.1v and so be considerable faster. But there are other things to consider. First, a fully charged 2S lipo will top out around 8.1v (give or take a tenth of a volt) while a 7 cell nimh pack will top out at 9.8v but the nimh will start to fall off much quicker than the lipo. The lipo will keep a pretty constant voltage (and thus performance) untill it is nearly discharged. Then there is the weight difference. A nimh pack is considerable heavier than a lipo. Lipo's do have some downsides though. You need an ESC that can be programed to quit drawing current when pack voltage drops below a certain point. The exact voltage depends on the pack configuration and voltage but is usually 3.0v/cell. You also need a lipo charger, you CANNOT use a nicad/nimh charger (not easily anyway). And Lipos are very finiky about overheating and charging. Improper charging and / or inattention can lead to explosions and fires.
If you're willing to deal with them though, lipos are great batteries. Lots of power, a great discharge curve and light weight too.
A 2 cell lipo will give you a nominal voltage of 7.4 V so will likely be a bit slower than a 7cell nimh pack (8.4v). A 3S lipo will be 11.1v and so be considerable faster. But there are other things to consider. First, a fully charged 2S lipo will top out around 8.1v (give or take a tenth of a volt) while a 7 cell nimh pack will top out at 9.8v but the nimh will start to fall off much quicker than the lipo. The lipo will keep a pretty constant voltage (and thus performance) untill it is nearly discharged. Then there is the weight difference. A nimh pack is considerable heavier than a lipo. Lipo's do have some downsides though. You need an ESC that can be programed to quit drawing current when pack voltage drops below a certain point. The exact voltage depends on the pack configuration and voltage but is usually 3.0v/cell. You also need a lipo charger, you CANNOT use a nicad/nimh charger (not easily anyway). And Lipos are very finiky about overheating and charging. Improper charging and / or inattention can lead to explosions and fires.
If you're willing to deal with them though, lipos are great batteries. Lots of power, a great discharge curve and light weight too.
