From bigclivedotcom.

A look at the 100A (LOL) version of the very common solar charge controllers.

These are cheap and basic control units designed to facilitate the charging of a battery from a solar panel, and then control an output with protection against overdischarging the battery.

On a previous video where I did a full reverse engineering of the circuitry, many of the comments suggested that people who had connected high current or high open circuit voltage solar panels to these units had issues with them getting hot and failing.
They also mentioned water ingress causing issues and that’s definitely going to damage these units. They should be mounted in an enclosure that can breathe. Even just an inverted box over them to protect against direct rain exposure would be good.

I’d only suggest these units as a cheap option for simple applications like a small solar panel being used to top up an old car battery for off-grid or garden shed lighting.

Many of the listings for these units imply that they are MPPT units. They’re not. MPPT (Maximum Power Point Tracking) is a system where the efficiency of the output of a solar panel can be optimised.
A simple way to explain it is that if you had a solar panel capable of putting out 20V at 1A and used it to directly charge a 12V battery, the voltage of the solar panel would be dragged down to 12V but still deliver around 1A. An MPPT system would use a buck converter to convert the 20V at 1A (20W) to around 12V at 1.5A to allow more current to be delivered to the battery.

There is no MPPT circuitry in these units at all. They just use simple low speed switching of the solar panel to the battery depending on the charge level.

One possible benefit of this simplicity is that these units are less likely to produce electrical noise when powering remote radio equipment.

An instant upgrade (and repair) for these units is to substitute in new MOSFETs, noting the polarity.
Someone mentioned their unit being fitted with HY1707 MOSFETs which are rated around 75V with an on-state resistance of just 6 milliohms. The gate drive voltage is around 10V in these units, so most generic N-channel power MOSFETs should be OK.

The terminals are OK, but not rated for very high current. Also note that they are rising clamp terminals and it’s important to unscrew them fully and make sure the wires go into the clamps properly when you tighten them. It’s very easy to slide the wire underneath the rising clamp resulting in it being loose.

Don’t use the USB sockets for anything. Many of these units use an older buck converter chip that can’t deliver much current and unfortunately also powers the rest of the circuitry.

Although these units can auto detect a 12V or 24V system based on the voltage of the battery (always connect the battery first and disconnect it last) I recommend against using the unit as a 24V system. I also strongly recommend against using a solar panel with a voltage rating much higher than the battery it’s charging.

The full video about these chargers (with schematic) is here:-

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