lead acid battery charging, will this work

We have an electric fence on our allotment, it has what I think is a 7 AH sealed battery supplying it with 12 V. It is charged from a small solar panel via a Schottky diode to prevent the battery discharging through the panel at night. The fence unit is continuously connected so always drawing current. The panel (about 300 x 200 mm) keeps the battery topped up and has done for well over a year without attention. You might need to have some kind of charger circuit for intermittent usage.

It's all a bit irrelevant now as we invested in another solar panel, which gave all sorts of other problems now hopefully solved, but the original idea was to connect the extra battery to the outlet in the boot and leave it connected whilst driving around during the week, not to attempt to do when engine not running.

In brief the solar anel issue is that it charges the battery so well that it is outputting over 14v. The chip didn't like it, it was OK on 12, but 14.4 was too much for the little things.

Assuming the battery is a Li-Ion You probably need something like this.

18650 Charger Protection Module 5S 10A Li-ion Lithium Battery BMS 18.5V 21V Cell | eBay

They are specific to the number of cells. 20V suggest a 5 cell battery.

You will need to get inside to connect the individual cells to the control module. If you can get inside you might find the module is a generic one like this. They are usually installed in the battery rather than the device to allow them to function in a charger.

E bay

This is what we use when doing camper conversions to charge the leisure battery.

Split charger

Steve.

My next door neighbor has a van that doesn't get used much, and he has a solar cell array stuck to the roof that keeps the battery charged.

Thank you, Robert and Peter - The grinder is a Lidl branded 20v item and dismantling it (VERY tricky) shows a compact installation with a thin oblong completely sealed unit between the battery and the on/off switch. This, I assume, contains the monitor and balance functions and is (for all practical purposes) internally inaccessable. The monitor item I was considering was somewhat simpler than your item, Peter, having built-in digital voltage read-outs and (I assumed) intended to be wired directly between the battery and on/off switch to give real-time battery voltage state. The thought was to monitor this value and stop using the grinder when the indication was at an appropriate (rechargeable) level. The supplied charger has all the necessary protection circuits and is fully serviceable, as is the battery pack (at the moment). There are probably difficulties which I haven't appreciated due to lack of knowledge - hence the call for advice.

rgds

Bill

At our club, even though we have mains power, all our loco batteries are recharged by a solar charger on the roof of the storage shed. Only a small solar panel, with controller, will keep the batteries topped up forever.

Although it varies with temperature the normal charge voltage for lead acid batteries is 2.45V per cell, or 14.7V for a nominal 12V battery.

Andrew

Very hard to tell what that component is without information or disassembly. Likely not a typical lithium battery protection circuit though. These are normally inside the battery pack. It could be over-current protection, over discharge protection, over temperature protection a combination or something completely different.

Does it have any markings?

How mainy wires ? all the same size?

Robert G8RPI.