Hi,
I want to build a garden solar light solution using NiMH battaries and a charging module, with the idea, that the sun panel charges batteries when there is sun, otherwise the batteries light the diode.
Is that possible to use this module for the case https://www.aliexpress.com/item/1005007011582257.html
I want to check if it’s possible to connect this module to both solar panel, battery and to load at the same time, or I need another module?
It does depend on the solar panels you want to use.
That said, NiMh batteries are a very poor choice for this kind of project due to their memory effect.
NiMh (and Nicad) batteries work best if they are discharged almost completely and then recharged fully. A solar panel light will not do this and therefore the batteries will wear out really quickly. LiPo batteries are already a better choice, but require a more complex charging system. If weight is not a restriction then lead-acid batteries are the best. they don't mind charging in an irregular way.
Load-sharing is not going to happen anyway (normally the solar panel can be used to detect darkness) but NiMh batteries are not as sensitive to over-charging as LiPo batteries and there isn't much risk of explosion.
Again Lead-acid batteries are the best for this kind of purpose.
I was using a relatively small solar panel that gives 5V (3W) according to specs. Was testing it on full sun and it gave 5.7V.
I am not sure it will really give 3W. Probably less.
Regarding the battery type, I was thinking of taking a solar garden light I have and kind of add more capacity to it, so it has larger panel + more cells. I was wondering if I can use NiMH batteries as more safe/common option in small garden light solutions
According to Wikipedia
Loss of capacity
Voltage depression (often mistakenly attributed to the memory effect) from repeated partial discharge can occur, but is reversible with a few full discharge/charge cycles.
So there is an effect that may look like the permanent memory effect that plagued NiCd cells. It doesn't damage the cells and is reversible, and so may not make NiMh unsuitable for your project, but you need to try to ensure full charge/discharge cycles every time.
Solar garden lights often use NiMh, but the cell capacities are low, and are not expected to light up for more than a few hours, so that there is a good chance of full charge & discharge cycles over 24 hours.
Aha, so in general the idea of adding more capacity to these cells, is killing the idea of low capacity cells. Now I understand why they all have one tiny battery :(. Just to be able to charge it fully.
So If I want more capacity I should switch it all to something like 18650 cell?
The garden lights I've taken apart to try to fix all had NiMH cells. They seem to work ok, and may even have an advantage in very cold weather. And they don't really need to be protected for over-discharge.
You should find a number of sample circuits online when searching for solar garden light circuits.
I don't think load sharing makes sense for these lights. The lights should never be on when the cells are being charged. So the lights should always be off in the daytime, even on cloudy days. And they should turn on only at night.
As long as you increase the charging capacity as well.
Li-ion cells have great power but with great power comes great responsibility.
Li-ion cells can be genuinely dangerous if not treated with respect, which means preventing over-charging and over-discharging.
Specialist charging circuits/modules are required to prevent over-changing, and some but not all these modules also have over-discharge protection. So choose your module carefully.
Another option is Li-Po cells, which often have over-discharge protection circuits built-in. But check that, don't assume.
18650 cells mostly do not have built-in over-discharge protection, but a few do, so look out for those. You can usually spot those by the metal stripe running the length of the cell, which allows the built-in circuit to measure the cell's voltage.
