There is no limit to how many Chipolos you can connect to your Chipolo account, however, Bluetooth does have a limit on how many active connections it can sustain at once.
Both on Android and iOS devices Bluetooth generally can only keep an active connection with a maximum of 7 devices at once. This varies from device to device, so some devices may be able to handle more.
Please note that this limit includes all Bluetooth devices you connect to your phone. For example, if you use Bluetooth earbuds, those will represent one connection and you will only be able to actively connect to 6 Chipolos at once. Any new Bluetooth device you connect to your phone will restrict the number of Chipolos you can keep connected with your phone.