Using an NiMH battery with Picaxe

Hey everyone, this is my first post. I'm new to picaxe and have a basic understanding of how they work and how to set them up. I'm designing a little robot that avoids obstacles and generally roams around on its own. So far I've set up the srf005 ultra sonic range finder and it works perfectly and I can control motors and servos too. What I was wondering is can I use an NiMH battery to control just the motors and then a 4.5v battery pack for the picaxe?. I have a 1500mAh 7.2 Volt battery that I'd love to use but I think I've read picaxe can only handle around 1 amp. I'm using the picaxe 18m2. I have the 18m2 starter board (CHI030) and I understand you can cut off a resistor and add a second battery source for your outputs but I'd just like to know if its possible to add such a high battery without damaging the board.

Thanks everyone

Sam

Welcome to the forum.

samh93 said:

I have a 1500mAh 7.2 Volt battery that I'd love to use but I think I've read picaxe can only handle around 1 amp. I'm using the picaxe 18m2.

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You could connect a 1000000mAh battery to the PICAXE and it won't damage it as long as the voltage is less than 5.5V. If it's not then you should use a voltage regulator.

samh93 said:

I have the 18m2 starter board (CHI030) and I understand you can cut off a resistor and add a second battery source for your outputs but I'd just like to know if its possible to add such a high battery without damaging the board.

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1500mAh isn't high - and it wouldn't matter anyway as current passing through the traces on the board all depend on how much current is being drawn by whatever's connected to the board.

I dont know the CHI030 board, but do it have the L293 motor driver chip on the board?
If so and your question was related to using the 7.2v battery through the L293 to supply the motors only, than the answer to your question is yes, but both battery grounds must be connected together to form a common ground.

If you are not using a L293 than you will need to post a schematic of your circuit so we can see what it is you intend to do with the second battery and driving the motors.

Thanks for the replies everyone. I'm really happy the battery will work fine. I just wanted to check incase it destroyed my board. Yes it has an L293 built onto the board so it should work fine. Thanks for your help everyone, really appreciate it.

Sam

Even though you have a current limited regulator, I would suggest you also connect a fuse right at the battery + terminal in case of wiring problems. A 1.5Ah battery can do a lot of damage to a miss-wired or faulty regulator and other circuitry.

Speaking of batteries -primary types anyway- check this recent AA cell showdown.

Thanks Manuka. That's great information.

Yes, Manuka, thanks for the link.

For me, that the Costco "Kirkland" brand of alkaline scores near the top in both performance and cost/benefit for low- and high-drain may be all I need to remember about the 25 batteries tested. Much easier than trying to remember which of the multiple Duracells and Energizers is best, not to mention the pathetic Panasonic.