Probably much larger than you need, most cruisers are fine with 5 Ah. Buy if you have the weight then go for it.
Is this better? I would only need 1? or 2? and a charger, obviously, right? http://www.batterymart.com/p-6v-7ah-sealed-lead-acid-battery.html
Cruisers are allowed to change batteries between sorties since they cant carry as much weight. I would suggest you take advantage of that. (that means you need 4 batteries and either 2 or 4 chargers depends on how clever you are.) If you have enough weight to carry a 7Ah brick then go for it, with cruiser batteries it pretty much all comes down to weight.
I only had two for NATS and charged them during each sortie so while I was using 1 I was charging one I had no problems
An sla battery will not take a 1 hour fast charge like a nihm will. I think you will find that the 7ah lead acid is to big and too heavy for a cruiser.I run 2 3000 nihms in my suffren and put them on fast charge between sorties. they last all day.I have 1 5cell 6volt 10 amphr nihm in my other cruiser and I hit it between battles it also lasts all day
Rick from BC runs both his Scheer's on 6v, 7ah SLA's with no problem. In the new one, we even used 2 Kips solenoids which is a bit of weight themselves, but made sure we kept the weight down with a very clean build. The pocket BB's have just enough hull volume to do it. My Mogami was overweight with the SLA, so I had to go to Nmih's.
I ran SLA at NATS and was a tad heavy but now I run NIMH and it works much nicer weight and space wise but other that that no different in performance seeing as I was out of or under the water in short order so no endurance issues []
http://www.all-battery.com/two72v4500mahflatnimhhighpower40adrainratebatterypackswithtamiyaconnectorsforrccarsandsumorobots.aspx
If you want a better price, use the same store Powder does, but buy from their E-bay store. The same battery packs Powder listed for $64.99 are only $44.99. I have been getting all of mine this way. Visit this site Or even better price, with a little less capacity for 2 packs, $29.99. And with a charger for $46.99. Visit this site
how many sets of batteries do i need? do you use both packs at the same time Monk? http://www.all-battery.com/two72v4500mahhighpowernimhbatterieswithasmartcharger.aspx