I'm looking at using a stock Sparkfun LiPo/Li-ion Battery Babysitter to charge an array of four 18650 Li-ion rechargeable batteries (Panasonic) in parallel, keeping the pack voltage at 3.7V. I chose the charger because it has excellent monitoring and control on-board. I read the data sheet for the Texas Instruments charge controller and it had the needed protection for the unprotected batteries (under-voltage, over-voltage), with the over-current protection provided by a simple fast-blow fuse.

The only issue is that the charger only runs at 1.5A max current. Considering that the battery array is capable of taking more than four times that rate, is there going to be an issue charging so slowly? I've seen Sparkfun recommend this charger for their 3.7V LiPo pack that uses three 18650 batteries, so I figured it would be fine and just charge very (very) slowly. If it's necessary, I suppose I could wire up two chargers and split the batteries between them, but I don't mind the slow charging rate if it won't hurt the batteries.

  • \$\begingroup\$ Unless you charger has a timeout "feature", there should ne no problems. \$\endgroup\$ – winny Jul 13 '17 at 5:35
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    \$\begingroup\$ The only very minor point that you might want to consider when slow charging like this is that those chargers usually shut off at c/10 or in your case 1500mA/10 or 150 mA. For a single cell this is totally fine, but when spread over four cells it is really closer to 40 mA/cell (37.5 to be exact). This is fine, but means your cells will be very very full. And the fuller you stuff your cells the faster they start to lose capacity and more likely to burn if abused. But a minor point. \$\endgroup\$ – Filek Jul 13 '17 at 6:21
  • \$\begingroup\$ Ah, very good point, I will check into the documentation for the controller. \$\endgroup\$ – Will Jul 13 '17 at 17:01

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