Homes have breakers that keep the current in a line from going over a certain number of amps. I think that also means protection from “over-current”, “short circuit”, and “ground fault”.

Surge Protectors (SPDs) by Electrician U on YouTube:

Surge protectors divert the current from a voltage spike to ground. So if there isn't a ground in your home wiring then the surge protector is useless. He explains types I, II, III, IV.

Why Whole Home Surge Protectors Are Now Required and How To Install One! by How To Home on YouTube.

High and Low Voltage Protection for your Home - Cost Effective Solution by rtech on YouTube.

Voltage stabilizers are more advanced. Voltage Stabilizer Considerations:

1. Power requirements
2. Voltage range
3. There are two types of voltage stabilizers: Relay and Servo. Relay are more economical, servo more precise.
4. Safety features: overload protection, short circuit protection, voltage cutoff.

I have searched for an accurate battery tester for non-rechargeable batteries. Most battery testers do not apply sufficient load to accurately test a battery. So a non-rechargeable battery with 20% life remaining will still read as “good”.

There are some battery testers for rechargeable batteries that can measure the health of a battery, instead of the percentage of charge remaining. The energy capacity (Watt*Hours) is a health measurement, but knowing this requires a full discharge cycle. Some battery testers are capable of estimating battery health without a full discharge cycle? That would also be good.

One brand of battery tester capable of quickly estimating battery health is ZTS. One must be aware of its idiosyncrasies. Based on Amazon reviews of the ZTS models, it's tricky to seat the battery for consistent results, and batteries that have sat too long may need a workout for an accurate result. But that's not all:

SilverFox in the same thread as above gives an excellent review of the ZTS models.