split charge relay to charge two 6v 4.5ah batteries

[waigy]

I have two maplin 6v 4.5ah batteries wired in series to power my dashcam while parked.
The batteries are similar to this one :

Will this split charge relay be ok to re-charge the batteries while driving?
Maypole 292 20A Caravan Dual Charge Relay Kit: Amazon.co.uk: Car & Motorbike - https://www.amazon.co.uk/Maypole-292-Caravan-Charge-Relay/dp/B008LUK3A8

 

[waigy]

My car is a 2006 Vauxhall corsa C which has canbus electrics.

 

[PEG]

Hi,how is the split charge device to be wired,and from where?

 

[waigy]

The 6v batteries will be right next to the car battery and wired similar to this:

The relay I have ordered is a Tec2 20a so it uses a 15a fuse and it has an extra "ign" connection to connect to a supply that is live when the car is switched on.

 

[waigy]

My main concern is how small the 6v batteries are in ah and physically.
These split charge relays are more commonly used to charge large leisure batteries.