I just got in a LiPo charger (ptr-10401) and I want to use it to (yes I know slowly) charge a 24.8 Whr Lithium Polymer battery.

My question is pretty simple. Does this device contain the required logic to safely charge this battery? Meaning, if I were to plug it in and leave it would it be safe (I am not going to do this)

I was looking for laymen documentation or a tutorial but the only thing I could find was the VERY detailed documentation for the LiPo charger.

It's still to far beyond me (but I am trying, I just got Circuit Analysis for dummies)

Below are the parts and the links

I haven't hooked anything up. I want to make 100% sure this is a safe method for charging before I do this.


enter image description here


enter image description here

  • \$\begingroup\$ That is a 24.8Whr battery. Quite a different beast from a 24kWhr battery! Please fix your title. \$\endgroup\$ – Bobbi Bennett Aug 31 '13 at 22:05
  • \$\begingroup\$ @BobbiBennett Oh sorry I thought it was 24,800 Wat Hours so I put 24k for thousand. I will fix \$\endgroup\$ – Anthony Russell Aug 31 '13 at 22:49

Having used the Sparkfun battery charger you listed (and in general designing with the Microchip MCP73831 battery charger), I have found that while it is supposed to be be safe, the Sparkfun device will get alarmingly hot when charging a large, almost empty battery from 5V USB power. I suspect this is simply due to the linear nature of the battery charger and the small un-heatsinked package., but I would be a bit weary of leaving it plugged in unattended because of this.

  • \$\begingroup\$ would you suggest dialing down the voltage from the 5V with some resistors before feeding it into the charging unit? \$\endgroup\$ – Anthony Russell Aug 31 '13 at 23:05
  • \$\begingroup\$ also, given what we know about how resistance works wouldn't you say that the device getting hot is a natural bi-product of it working and controlling the flow of voltage? (not playing devils advocate or trying to snark you I am actually asking because I know nothing about this stuff) \$\endgroup\$ – Anthony Russell Aug 31 '13 at 23:07
  • \$\begingroup\$ In theory the device has an internal thermal shutdown (which is supposed to kick in at 150C) and programmable charge current. The way it is used in the Sparkfun charger, Rprog = 2K, so the charger current seems to be at the maximum specified limit of 500mA. It is probably fine, but for a large battery, you can change Rprog to something bigger to limit the current (Ireg = 1000V/Rprog) \$\endgroup\$ – Zuofu Aug 31 '13 at 23:12
  • \$\begingroup\$ Do you know if there is a suggested operating time frame? \$\endgroup\$ – Anthony Russell Aug 31 '13 at 23:12
  • 1
    \$\begingroup\$ That seems about normal, if the initial cell voltage is low, it will just be current limited. Once it goes into constant-voltage mode, it will slow way down. \$\endgroup\$ – Zuofu Sep 1 '13 at 0:12

LiPo chargers have 3 stages and is completely safe on bigger batteries of same cell voltage.

The CC stage is 1st will limit current and just be a much longer duration. Safe.

The CV stage is 2nd and stay there until current drops below expected leakage thresholds. Safe.

Shutdown or charge-completed is the 3rd stage. Safe.

CC means constant current and some fast chargers will be designed for say C/10 or C/20 meaning Ah capacity /10 or /20, for example. There is no universal current value for all LiPo batteries.

Just be sure the cell string voltage is the same before stage 2.

  • \$\begingroup\$ So what you mean is get out my multimeter after stage 1 and make sure that the reading is equivalant to the labeled voltage of 3.75? \$\endgroup\$ – Anthony Russell Aug 31 '13 at 22:51

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.