This is something i know incredibly little about, i am designing a robot and are using three 9v batteries to run it off, these batteires control the motors, a metal detector and a microcontroller individually, i was wondering how simple it is to create a circuit so i can plug a mains adapter straight into the robot instead of having to remove the batteries to charge them, this is something i have no experience on so i am completly in the dark.

It would be ideal that the batteries charge however without damaging rest of circuit. Is such a thing possible.

Thanks

James

 

Are the 9-volt batteries you are using of the rechargeble type?

hgmjr

 

http://www.batteryuniversity.com/

This in an valuable resource for batteries and battery related info.

You can learn everything you need to know about using batteries in you designs, how yo calculate and find different specs on the batteries being used, and charging techniques.

But most importantly, DONT recharge non-rechargeable batteries.

You can incorporate a charging circuit that you can switch the robots circuits out of the mix and the charging circuit into it. That is the easiest way.

Read up on required voltages and current for charging the types of batteries you have, and the dangers of reducing battery life and more importantly, fire and safety.

Dont burn your project and maybe more, just to save the time of pulling the batteries.

You already took the first step by asking for help. Good.
After reading the link, you may want to look up battery charging ICs. It all depends on the chemistry of the batteries you are using. i.e. You cant charge lithium-based batteries with a niCad charger and so on.

 

You are going to be rather disappointed in how poorly 9v "transistor" batteries will perform in a robot. They are fine for things like small transistor radios, that only draw a few mA current. However, when you start drawing more than 20mA current, they run out of power pretty quickly.

Consider using something like NiMH AA batteries instead. You will have much more power available, and you can be a lot more flexible with configuring them to output just the voltage you need.

 

You may also consider a Sealed Lead Acid (SLA) battery. They will provide a lot of current, and are relatively easy to recharge.

You can get them pretty small now-a-days. Albeit not as small as a 9v-transistor battery, but then again, what size is your robot?

SgtWookies NiMH is the way to go for longer drain applications in a small package, but if you have the room, SLA is a good option.

 

okay, after reading all these comments i need to do my research into battaries and choice of, would a recharging circuit but generic (as regards layout) and if so how complicated are they.

thanks
james

 

The charging circuits change complexity with battery chemistry and the speed you are trying to charge them at.

You really need to choose a battery that can offer you the proper runtime and voltages with the space you have available.

Charging circuit will be determined by that.