Running a CL0116 solar light controller with two NiMHs instead of one - Page 1
Forum section: electronics / projects

author: 5U4GB
author_rank: Super Contributor
timestamp: August 28, 2024, 07:26:08 am
content: The ChipLink CL0116 solar light controller is always shown as using a single 1.2V NiMH cell, which isn't surprising given itsone-page data sheetcontaining next to no information which means you're pretty much stuck copying their design for lack of any further information. However I recently came across a circuit that used two 1.2V cells in series, so it would be charging to 2.4V instead of 1.2V. Does anyone know how this would work?

author: SeanB
author_rank: Super Contributor
timestamp: August 28, 2024, 11:23:40 am
content: Well Vdd, which is Vbatt, is 3V, and this is within the voltage range of 2 AA NimH cells. Solar panel will need to have a voltage output of around 3V to charge it, so you will probably be using a 6V panel, and relying on the battery to absorb excess charge. As to the LED you want 2 in series, and size the inductor to have around 100mA of current through the LED's, as the main reason to go to a series connection is driving multiple LED's, so a 2S arrangement of the LED's is used, and you need a higher power output in the same package. 3S might work, even though it means the inductor pin will see around 9V peak voltage, which is a little above the 5V rating of the part, and some might fail long term.

author: 5U4GB
author_rank: Super Contributor
timestamp: August 28, 2024, 12:47:40 pm
content: I was more wondering how the charge controller works when it's being asked to handle charging at a very different voltage than what it's apparently meant for. So using voltage-based termination wouldn't work... unless it uses something fancy like -dv/dt-based termination, but I can't imagine that from a 30-cent IC.Or maybe there's barely any "controller" actually present and it just continuously trickles the solar cell output into the battery/batteries on the assumption that you won't get more than 8-10 hours of usable sunlight so it'll cease charging by itself at some point.

author: edavid
author_rank: Super Contributor
timestamp: August 28, 2024, 02:25:32 pm
content: Quote from: 5U4GB on August 28, 2024, 12:47:40 pmThe QX5252 datasheet just shows a diode between SBAT and BAT, so I think this idea is correct. If you want overcharge protection, you have to add it yourself.

author: 5U4GB
author_rank: Super Contributor
timestamp: August 29, 2024, 12:02:21 pm
content: Ah, well spotted!So the over-discharge protection shown in the QX5252 data sheet, if present in the CL0116, probably won't work because by the time both cells in series drop to the never-exceed limit for a single cell it's already too late.

author: 5U4GB
author_rank: Super Contributor
timestamp: August 29, 2024, 12:40:41 pm
content: Googling around a bit more, it looks like there's an entire class of these devices, almost all TO-94 and with identical circuits so possibly all cloned/copied from each other. There's the CL0116 I ran into, the QX5252, YX805, YX8018, and no doubt many others. For operating at a higher voltage the very common QX5252's less-common cousin QX5253, for which I've only found Chinese data sheets so I can't get more than the voltage and circuit diagram, would seem to be the way to go since it's specced for two cells and 1.8-3.0V operation so you'll get proper discharge protection when using two cells.Apart from the use of the cheapest possible parts, this may also explain why solar garden lights are so failure-prone, you're mostly relying on cell chemistry to manage the batteries.I also foundthis page which describes the circuit's operation:Quote

author: spa2036
author_rank: Newbie
timestamp: March 13, 2025, 04:10:35 pm
content: I was searching for information about the CL0116 when I came across this thread.Recently I refurbished an old solar panel with 2 NiMH batteries in series.After reverse enginering the circuit I came up with the following schematic.This is completely different as the schematics you'll find on-line.Still trying to wrap my head around the LED parallel to the inductorSolar cell is 4.5V.Maybe it is of intrest to someone.