Is the system waterproof ?

Yes the system is IP65 standard

How many TT devices can I connect to one router TT CLOUD ?

In principle 256 but in reality to avoid collision of data packets we suggest 20 devices

How long batteries will last ?

Batteries pack comes with a built in solar panel. They are high efficiency Li-Ion rechargable batteries.Typically for TT models with heating probe (TT-F, TT-W) battery life can be considered more than 30 days. For TT without heating probe (TT-S, TT-R) the battery life extend more than 60days. For TT-G battery duration extended over 5 years All the specification may vary due to solar radiation regime available within the canopy. We suggest to buy one fast (3 hours) TT CHARGER for every 20 devices