Nissan Patrol 4x4 (Africa)

I have an interesting problem.
Both batteries fully charged.
When turning the starting motor it clatters as if the battery is flat. Then after a few moment the clattering stops and the engine starts. Second time round the engine starts easily with no clattering of the starts motor. Same thing happens with both batteries connected. I have a National Luna battery pack.The crank battery measures 14.95V and the Deep Cycle measure 14.94.V when not connected to each other.

Any ideas?

Check the positive cable to the starter motor. Outside of that, maybe the starter motor needs a good service.

Thanks Clem. Will check the cable
The starter motor is seven months old.

Could possibly be the earth strap as well?

Bad connection on power circuit check maar jy sal dit kry

Dit lyk asof die battery op die eimde vam sy lewe is. Het hom vol gelaai. Tussem vanoggend 09H00 en 15H00 het die voltage van 14.9V to 12.2V geval sonder dat die battery moes werk.

Kortsluiting wat die battery tap :
Tracking systm [veral TRACKER s'n]
n gloeilamp met n "deadshort"
los draadjie binne starter
een los plaatjie binne jou battery
beskadigde bogy cords [plug drade]
en dan natuurlik daai earth kabel
selfs n los battery pool kan jou so rond erm erm erm mmm

Dankie almal vir die raad.
Dit was 'n interne kortsluiting in die battery. Van volgelaai tot pap vat 2 ure sonder enige weerstand.
Het die battery vervang, nou is alles normaal.

I am sticking to this thread not with an identical issue, I hope that is all right!

From time to time it sounds like the starter relay is not disconnecting quick enough (mainly with cold engine but I must clarify that). I am not sure if it is this problem but after starting I have an unnormal sound for the fragment of a second - sometimes.
So I am thinking of reconditioning the start / it's relays.
Is it manageable without removing the whole engine to access the starter and open it with 'normal' tools?

Yes, just a reasonable selection of socket extensions necessary to reach the top mounting bolt