I've built a charger for my batter (NiMh 6-cell 7.2v) using MAX712 IC.

The problem I'm facing is that it's in a linear mode which requires either a huge heatsink or a heatsink with a fan (9W). See my previous question - MAX712 charging circuit - diode gets too hot

The charger has to be a part of a robot, so size does matter.

I was looking at using MAX712 in switch-mode, which is possible, but requires substantial work:

Someone suggested to use DS2715 instead which is switch-mode natively.
This charger uses temperature change (Dt/dt) for detecting charge termination instead of voltage drop that MAX712 uses. My battery doesn't have a thermistor built-in.

So my questions:
1. Can I just glue thermistor on top of the battery pack so it would allow me to use DS2715?
2. What is a better method - voltage drop detection or temperature change (Dt/dt)?
3. Any other battery charging ICs I should consider?

Cheers, Leonti

  • \$\begingroup\$ What's your DC input voltage? How many mA? Sounds like your DC in is too much higher than the charge voltage. \$\endgroup\$ May 15, 2017 at 3:41
  • \$\begingroup\$ My input is 15v, 1A current charge. Input has to be at least (1.9v * 6) + 2v = 13.4v according to datasheet, so 15v is pretty close. Even if I manage to get a power source down to 13.4 I will still have 7.4W to dissipate which is still a lot. \$\endgroup\$
    – Leonti
    May 15, 2017 at 4:31
  • \$\begingroup\$ If you look at most commercial laptop battery packs, they do indeed just use some form of temperature sensing device glued to the battery. I would still like to point out that you shuold be cautious doing this tho, and advise you to verify the performance with a second thermometer during testing. I do believe that temperature (or if my memory serves me right, the change \$\frac{dT}{dt}\$) is a better way of checking charging, but I'm not confident enough to put it in a answer. \$\endgroup\$
    – Joren Vaes
    May 15, 2017 at 6:30
  • \$\begingroup\$ @JorenVaes yes, I meant temperature change, not the temperature itself. Thanks for pointing it out. \$\endgroup\$
    – Leonti
    May 15, 2017 at 7:03

1 Answer 1


Any other battery charging ICs I should consider?

This one is worth a look. I'm not saying it is better, it is a switcher and appears simple.

The TI BQ24115 appears to be capable and not too complex with minimal external components given the feature set.

For NiMH you would need the "System-Controlled" (i.e. host controller) version. It cannot do NiMH as a stand alone charger.

  • Integrated Power FET
  • Thermal Pad
  • 2A @ Up to 15.5V (Vin(max)=20V)
  • Built in Battery Detection
  • LED Drivers for Status Indication or Host communication
  • 1.1Mhz fixed switching with 0-100% duty cycle
  • Precharge and Fast-Charge Control
  • Charge Termination and Safety Timers

enter image description here


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.