Ideal Energy/Battery Source for a Battery Powered Lamppost
Cons of lead-acid are that they self discharge, and once they go flat are totally destroyed. In practice, the batteries will be dead next year, so factor that in. 
Or use a medium sized lead-acid battery, and at the end of the job keep it for your car!
(BTW there is now a lead-crystal battery that claims to have long cycle life, and survive discharge. Don't know if it is true)

I am assuming that it is summer when you want to do this. Put a solar panel on the battery. It doesn't need to meet 100% -  A 10W solar panel will greatly extend the time between charges, even a small 5W panel will help a lot.

Alkalines have 3 cons:


only give maximum capacity at fairly low currents - you would need to use lots all at once.
end of life voltage is 0.9V, so you probably need a switching regulator.
good performance warm, but very poor in the cold.


Pros are: 


readily available and cheap
long shelf life > 5 years (-3%/year)


Note that non-alkalines ("Heavy Duty") require even lower currents to give rated capacity. They are not useful or economic for this job.

I will consider D-size alkalines, as I know the data for them.  They are 15Ah, but achieve full capacity at 100mA discharge capacity, and significantly less at 250mA, and 1/2 at 500mA. They have total energy of 75kJ/cell@100mA.

If you wanted a 12V 1A lamp, you will use 432 kJ/10hrs. 

You need


6 cells/10hrs to meet the energy capacity
80 cells for 100mA for best life
40 cells at 200mA for reduced life


So 40 alkaline D cells would do the whole job, probably giving 5 days without recharging, cheapies appear to be about $1 in bulk packs. Make it 36 since they probably come in dozens.

You can slide them into a 2.2m x 1.5" aluminium tube that holds the light up, making 54V as 36x1 or 27V as 18x2, and use a switchmode to step the voltage down to run the leds.

Alkalines are quite rechargeable as long as you only do a shallow discharge (which you would have), so you can still put a small solar panel (5-10W) on to recharge them. With the long shelf life, it will still be working OK next year.



You could probably hugely reduce the required capacity with a PIR sensor, and run the leds at 1/4 power, until movement is detected, then turn them up to 100%.



Other rechargables, to run for only 1 day:


Li 18650's are approx 38kJ (3.6v,3Ah). So you would need 12cells ~ $42
D size NiMH at 11Ah,1.2V = 47kJ, or 10cells ~$65 (if the specs are true)


So alkaline D's at 5 days for$36 look pretty good.