Yes, the battery can be put in parallel or series, but there are tips we need to pay attention on:
A. Please make sure the batteries with same specification such as the voltage, capacity, charge, etc. If not, the batteries will be damaged or lifespan shortened.
B. Please make operation based on professional guide.
C. Or pls contact us for more advice.

Actually, lead acid charger is not recommended to charge lifepo4 battery as lead acid batteries charge at a lower voltage than LiFePO4 batteries require. As a result, SLA chargers will not charge your batteries to full capacity. Furthermore, chargers with a lower amperage rating are not compatible with lithium batteries.

So it is better charge with a special lithium battery charger.

Yes, Lanke lithium batteries work at -20-65℃(-4-149℉).
Can be charged in freezing temperatures with self-heating function(optional).