I am trying to recharge my 12V lead acid battery with a 12V DC motor. I am using the battery to power the robot when it climbs. When it descends, I notice that I dont need to apply reverse voltage but the dc motor just backdrives instead. This can act as generator to recharge back the battery, am I right?

I know that i need to step up the low voltage that is generated by the backdriven motor to 12V needed to recharge the battery. This is the board that I think can do the job: https://www.pololu.com/product/799

Is this all I need to make it work? With this method, should I be concerned about the 3 stages of battery charging: bulk, absorption and float?

Please advise. Any feedbacks are greatly appreciated.

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  • $\begingroup$ But I do not need braking. Let me check those links first. Thanks. $\endgroup$ – goddar Sep 30 '15 at 16:16
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    $\begingroup$ goddar, if you draw energy from the motor/generator to charge the batteries, you will slow the vehicle to some extent; which, in effect, is braking. Energy from the motor/generator is not "free"; when you move that energy into the battery it reduces energy elsewhere in the system. $\endgroup$ – James Waldby - jwpat7 Sep 30 '15 at 16:33
  • $\begingroup$ @jwpat7, in this case, it's the gravity that pulls my robot down and also backdrives all the motors. Does repeatedly backdriving the motor wear the gears off? For my application, is it ok to let the gravity repeatedly backdrives the motor or should I apply reverse voltage to make it descend. Which is better to prolong the life of the motor? $\endgroup$ – goddar Nov 8 '15 at 12:15
  • $\begingroup$ To prolong motor life, just let “gravity backdrive the motor”. To prolong gear life, “apply reverse voltage”. What's best depends on motor and gear costs, gearing ratio, load size vs gear and motor ratings, safety issues, etc. $\endgroup$ – James Waldby - jwpat7 Nov 8 '15 at 19:19

This question may be more suited to an electrical engineering site, but one thing to consider is that your batteries will have a maximum allowable charge current.

What this means is that if the wheel is turning too quickly, you will need to either limit the current into the charge circuit, or dissipate it some other way (such as in a resistor).

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  • $\begingroup$ I posted an almost similar question in the electrical engineering site, but they had said it was off topic too before they closed it. That is why I rephrase my question to suit this site. The question asked is pertaining my climbing robot. $\endgroup$ – goddar Oct 1 '15 at 1:12
  • $\begingroup$ There seem to be a bunch of questions there about regenerative braking, which is essentially what you're doing. The high level process is to backdrive the motor, use a boost converter of some kind (e.g. one based on the motor controller), and feed that into the battery's charge controller. $\endgroup$ – Ian Oct 1 '15 at 22:34

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