| Author |
Message |
Pam Russell
Unregistered guest
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| Posted on Thursday, June 22, 2006 - 1:22 pm: |
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My 9 year old son has a 4WD featherweight built by Jonno which we are trying to upgrade without troubling Jonno. It currently has 4 12V drill motors, 2 12V batteries made up from drill NiCad batteries at 1.2 amps and 2 electonize FR30HX microprocessor systems. We want to increase it to 18V. We have enough NiCads but do we need the battery bars? (Jonno seems to have soldered thin strips of metal when he made up the current packs). Also, on the FRA forum somebody has suggested including a fuse and fusebox between the servo and the motors - do you think we should be doing this and if so, what amp fuse do we need? Sorry if all sounds a bit daft, we are new to roboteering! |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 218
Registered: 10-2004
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| Posted on Thursday, June 22, 2006 - 7:20 pm: |
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Hello Pam,
Not having seen the packs that Jonno used I cannot be sure if he has used 'proper' battery bars or it could have been the spot welded tags that many battery packs use.
I should make you aware of the consequences of doing what you suggest. Increasing the battery voltage will make the robot faster, more pushing power, typically more difficult to control and more likely to burn out the drive motors or blow the speed controllers. However, just about all combat roboteers have to over-volt their motors, it's just a natural progression!
18V will increase each motor power by a factor of 225%, increase current through the speed controllers by 50% each and increase the stall current by 50%. You will also reduce the potential running time for each battery charge. So bottom line is you run the risk of burning out the motors, over-heating the batteries, over-heating or blowing the speed controllers / relays. Drill motors are quite variable in their power / current rating so I am unable to say if the controllers will cope.
Assuming you want to carry on, you need to solder links to the batteries to series them up pos / neg etc. Keep heat to a minimum when soldering, if the connection takes longer than typically 3-5 seconds to solder then you run the risk of damaging the battery. For featherweights, you should be using at least 2.5mm2 wire although our battery bars at 6mm2 are commonly used.
I, unlike many robot builders always use fuses between the batteries and the speed controllers. You mention between the servo and the motors, not sure what you are referring to here as I cannot see why you would have servos in there.
Hope that helps a bit and good luck. |
Admin (Admin)
Board Administrator
Username: Admin
Post Number: 220
Registered: 10-2004
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| Posted on Friday, June 23, 2006 - 6:01 pm: |
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That helps alot, thanks. Having read all that I think we'll just upgrade the batteries to 14.4 or 15.6V instead and hope for the best. I will use your battery bars so I'll order those online.
Thanks again for your time,
Pam |
