Let's Make Robots!

Charging batteries

Hi I would like to make something which can be charged Without taking the batteries out of the robot. I am thinking of using nimh batteries as I have heard that lipos are crazy and hard to do. I have read bait about this but all I have heard how powerfully to charge them and things to d with trickle charging and making sure u don't over charge the batteries but I don't anything about the very basics, like I have absoloutly no idea what I'm doing How can I charge the batteries whilst they are in the robot with out applying all the power to the robot? In most things the batteries go alternate ways but in charging I've seen the all the same way And just the general basics like actually getting the batteries to charge (hooking them up the right way e.t.c.) Thanks for any thing you can sayall help would be appreciated.

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The Max chips are what you need, specifically the Max713. It is a great chip, able to be configured for just about any size pack, you can adjust chargetime, current, trickle, etc etc etc.  It even handles an external temp probe if you want to use one.

Now, the cool thing is that it can source and charge at the same time. There are connections for pwr_in, battery and load (the load would be the robot itself). Everything can remain connected and in place only needing access to a barrel jack. 

Want even more good news? There is an incredibly well written and complete write-up here:



Boom. Done.

thanks that was just the kind of answer i was looking for (Wow that looks awful complicated which should keep me amused and hopefully not too confused for quite a while :D )
Ooh urr sorry there's loads Do u know the difference. There max713c/d, max713cpe,max713cpe+ e.t.c. Any ideas

I got the version of the Max713 that was available as a free sample. Dunno which one it was.

Don't let all the math and stuff scare you off. In the end, it is really just 2 inputs that need to be jumped correctly and you have to do a little math on a couple resistors --these things determine charge rate, tells the chip how big your pack is, max charge time etc. Ezekiel did a really good job laying everything out --just copy his stuff and substitute your values. 


no free samples oh well

WTH this was a most useful chip. There better be a good replacement for this thing. I hope it's not another good component that gets phased out inexplicably.

does anyone know any cheeper options as these are not availible for sample anymore

what do u think about battery packs and other things should i just use some regular nimh batteries in a battery holder?