Final answer:
To safely handle a suspected frozen lead-acid battery, initiate a trickle charge and observe the battery's response, avoiding high amperage charging or heating, as these can be dangerous.
Step-by-step explanation:
If you suspect that a lead-acid battery has frozen, you should not attempt to charge it at high amperage or heat it with a propane torch as these actions can be very dangerous. A frozen battery can cause the acid to expand, potentially cracking the battery and creating a risk for a hazardous spill or explosion, especially if there is a presence of hydrogen gas from electrolysis of water. The safest first step is to carefully trickle charge the battery and observe its response. Trickle charging gently introduces a small amount of current that could help the battery to gradually warm up and recover, if it's not already damaged. However, if the battery's case is distorted or cracked from freezing, it would be safer to replace the battery rather than attempting to charge it.