View Full Version : [Question(s)] Charging computer NIHM battery pack

06-30-2011, 04:37 PM

I just wanted to see what everyone thought of my idea. Seeing as I am not an electronic expert.

I have the irobot create and I have the attached CPU. I purchased a battery set up that pretty much mimics what the irobot uses. 12 subC nihm batteries @ 3800mah.

The create is capable of going to the charging base on its own. So I wanted to see if I am able to hardwire my new battery to the charging terminals that the current battery already uses. My hope is that the charger inside the irobot will be able to charge both batteries.

The only issues I can think of is that it will take longer to charge. Then the more serious one, if one battery is more discharged then another.

Does anyone have any input on this, could offer any advice or solutions?

Having an automated charge process would be golden in my book. So I will be shooting for it.

06-30-2011, 06:36 PM
I was just thinking of running the two batteries in parallel. That way the robot sees one battery, but the capacity is doubled. I'll put the battery in the cargo bay and make one big battery at 14.4 volts with 24 batteries.

11-17-2011, 05:22 PM
I think that's a great idea, in fact, I am trying to do something quite similar. I am trying to add a second battery to my laptop computer, and will have to figure out pretty much the same thing. I am interested to see what you figure out, and if what you figure out will be applicable to my own project. At this point, I have no idea where to start, except for maybe stopping in hhgregg (http://www.indeed.com/cmp/Hhgregg) or somewhere and picking up an extra laptop battery. If I figure anything out, I will be sure to share it here. Thanks.

11-17-2011, 06:23 PM
If you are using the stock power supply from iRobot it is rated @ 1.25 amps and as mentioned in a previous post it may take a little longer to charge both packs. It might be best to charge each pack individually first and then measure the battery voltage of each. If both packs are close in stored voltage then they can probably be connected in parallel, then used where some discharge takes place then try a parallel charge using the internal charging system of the Create. The Create has a pair of charging MOSFETs that might be damaged if the twin packs are allowed to discharge below 12 vdc and charging is attempted.

11-18-2011, 03:57 AM
Charging batteries can really be fairly complicated, and you generally don't want to charge in parallel. The best solution (this still depends on exactly how the robot's charger works though) would be to create a larger pack using higher capacity cells. Using the two you have though, connecting both in parallel might work, but due to the way the batteries are charged and to mismatched packs they likely would not both get fully charged. So charging won't be perfect, but it will likely work.

11-19-2011, 06:59 AM
Alright, well I had it set up. First I took out the battery for the create and charged the added battery pack. It worked fine. With both batteries charging it had a lot of trouble but it appeared to work.

I took the power directly from the terminals off of the charging port of the create.

I ended up having issues with the CPU motherboard I was using. The power drain of the kinect also caused issues.

So, after I got my EEE pc back from my sister and I am using that. Much easier and the battery is way better this way.

With the right CPU my original intention would work, but having the monitor, keyboard and everything from the laptop, made it ideal.

My recommendation is to stick with an EEE Pc if you can get one. Once you add the costs of the batteries, the DC power supply and the actual motherboard, your almost at the cost of an EEE pc.