EEVblog Electronics Community Forum
Electronics => Open Source Hardware => Topic started by: Michaelbradford on February 24, 2017, 03:19:49 am
-
Hi can anyone help me can I charge a 18 v Li-po battery with a DC power supply if not what route would be suggested thanks
-
You can find plenty of info on LiPo charging online. Basically it is a combination of constant current and constant voltage charging. Due to the high voltage, you must have multiple cells. In that case it may be trickier to balance the cells. Also be sure to monitor temperature to avoid something catastrophic while charging. I'd say use a charger designed for it. Presumably you will want to charge it multiple times right?
-
You'll need to make sure you have the full spec of the battery, max charging current (can be specified as a multiple of the battery capacity) and the float voltage.
-
Balancing is an important consideration when charging Li-Ion cells in series. It's possible to pack charge with just two wires, but imbalances occur that can cause premature wear and in the worst case can result in a safety hazard. You generally don't see consumer products charging that way, they normally balance the cells, but you can get away with pack charging if you balance every few cycles. Of course if a proper balance charger is available there's no reason to ever charge the pack with only two wires, just balance charge every time.
-
The easiest way to safely charge a multi-cell lipo with your dc power supply is to put a real lipo charger in between the supply and the lipo.
I recently upgraded my lipo charger to this (http://www.banggood.com/ISDT-SC-620-500W-20A-MINI-Smart-LCD-Battery-Balance-Charger-p-1060646.html) and are very happy with it. You also have less powerful versions like this (http://www.banggood.com/ISDT-Q6-Plus-300W-14A-MINI-Pocket-Battery-Balance-Charger-p-1103946.html) and this (http://www.banggood.com/ISDT-SC-608-150W-8A-MINI-Smart-LCD-Battery-Balance-Charger-p-1057271.html), in case you don't have a very powerful dc power supply to fully make use of it.
The main difference between the newer and older lipo chargers in the budget-range is the way they balance the cells. The typical four-button chargers like the B6/B6AC charge the whole pack until one cell is 4.2 volts, then discharge the cell to the level of the next highest cell, charge the full pack again and keeps at it until all are equal. The isdt chargers actually charges the cells individually instead of discharging them, which makes balancing faster and probably more accurate (?). The balancing current is not as high as the rated charge current, but keep in mind that the balancing current is only used at the very end of the charge cycle unless you have a very badly unbalanced pack.
You can see Dave's video on charging a single cell to get an idea of what is happening per cell when balancing a multi-cell pack:
https://www.youtube.com/watch?v=jNmlxBXEqW0 (https://www.youtube.com/watch?v=jNmlxBXEqW0)