Robotics battery circuit

[jzedaker]

I am currently building a robot with some class mates in my program at ITT tech. I would like to know if there is a circuit that i can build that will connect both batteries that I have for the robot, and switch between then as one runs low on power, and also has an LED display to indicate the charge left in each battery?

 

[shaiko]

Both batteries are the same voltage?

---------- Post added at 17:58 ---------- Previous post was at 17:56 ----------

I advice you use an 8 bit MCU that can drive an LCD and has a ADC with 2 channels.

 

[jzedaker]

one is 3300 mA and the other is 3000 mA. they are the batteries used for remote controlled cars.

---------- Post added at 11:02 ---------- Previous post was at 10:59 ----------

so yes they are both same voltage

 

[shaiko]

This isn't what I asked.
Are they the same voltage?

 

[jzedaker]

yes. they are same voltage

 

[shaiko]

So why switch between them?
Why not connect them in parallel with a balancer?

 

[jzedaker]

as it stands we are trying to figure out a way for us to improve its battery life while having to ability to roam our school all day. If we connect them in parallel with a balancer, with it provide the same amount of time?

---------- Post added at 11:16 ---------- Previous post was at 11:15 ----------

sorry... * will it provide the same amount of time * is what i meant to say

 

[shaiko]

Yes,
It will.

 

[jzedaker]

thank you shaiko

 

[shaiko]

This is a simple circuit for a battery selection



---------- Post added at 18:35 ---------- Previous post was at 18:33 ----------

This is a simple circuit for a battery selection



But I see no reason to solve it this way if both batts are of same voltage.

 

[dselec]

No if u use both batts.. in parallel each batt will need to give less amp/hrs so the time is the same .
When u mean "charge left" u need to decide if u want low volt indication before robot stops . or like in computer showing 50% or 40% or 30% left and so on...led for each percentage. U can use lm324 quad comparator and attach 4 leds .

 

[shaiko]

No if u use both batts.. in parallel each batt will need to give less amp/hrs so the time is the same.

Why do you say No ?

If you use both batteries in parallel (with a balancer)
or
use battery 1 until empty and than battery 2 until empty.

The time to complete energy exhaustion in both cases will be the same...