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Re: Rechargeable batteries for the RCX
Barry,
Although this is a general statement, the rechargeable batteries most people think of for this application are NiCad. Since the terminal voltage is 1.2 volts (NiMH too) instead of the 1.5 of alkaline, the total voltage availabe for the RCX then is a full 1.2 volts less when using the NiCads. With only 7.2 volts available, the RCX gets unstable when using all three motors in high current designs. With good quality alkalines, you should have no problem running a one week camp. This year we had several teams run on the same set of batteries most of the FLL build season.
This from the Tech Support at Midstorms...
The RCX programmable Brick is designed to run at 9 volts. As the batteries drain the RCX programmable Brick should continue to function until the voltage drops to less than 6.7 volts. Please note that intermittent or complete failure of operation including IR communication may occur at any point less than 7 volts. At 6.7 volts the low battery indicator should display and fewer than 6.3 volts the RCX programmable Brick will enter the alarm mode beeping. The RCX programmable Brick does have a Firmware protection mode, which will shut down the highest draw devices as needed to protect the RAM stored firmware. Generally the first device to shut down is the IR Communication, followed by the output ports that motors and lights are connected to.
And...
While it is safe to use any rechargeable batteries with LEGO MindStorms products, they will provide less useable time per recharge than non rechargeable batteries. This can lead to problems with the RCX, Scout, and/or IR Transmitter (Tower). If you do experience problems with any LEGO MindStorms product while using rechargeable batteries, we suggest that you try a set of fresh non rechargeable batteries to see if that solves the problem.
Also, don't be fooled by the DC adapter plug on the RCX. It is not the input for a rechargeable battery pack charger it is merely an alternate DC input..
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.
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