Is it possible to charge a lead acid battery(12V) with float voltage(13.6V) instead of charge voltage(14.4V)?I understand it will take lot of time to charge if we charge with float voltage.
If you charge at float voltage, not only will it take a long time to take as much charge as it's going to get, it will also not reach 100% charge.
It depends what it's going to be used for.
If as a mains failure backup battery for something like a burglar alarm or safety lighting, then floating it is a sensible thing to do, as it maximises life of the battery under those conditions, and makes for a very simple charging circuit, one voltage regulator and you're done.
If as a camping/caravan battery where you do want to know that you are up to 100% SOC, no, it won't give you that.
A word about lifetime and battery chemistry. Lead acid doesn't like being discharged to below 50% SOC, it shortens its life significantly if you do this repeatedly. It therefore makes a good alarm standby battery, but not such a good camping battery, where you might be tempted to run your peltier fridge up to 100% of the Ah claimed on the battery.
There are better battery types for deep discharge, NimH and LiPo to name the obvious ones. Neither are as cheap as lead acid (if you have a vehicle to transport the weight). If you want a long lifetime from your lead acid battery, then double the Ah you buy initially, so you don't need to fully discharge it.
Yes, it is possible but it takes a lot of time, first your battery will be charged at the constant current until the folat voltage (13.2) is reached (75%) then it will take a lot of time to charge the 25% (low current).
The best way to charge your battery is the 3-stages charging it like the float charging and continues to charge until your BOOST voltage (14.4V), then the current is reduced to 1/4 of the maximum to the 90% then the 10% are charged slowly by the float charging.
I believe it will work fine. The battery should last for years if you don't over-discharge it. An AGM might be the best choice due to low maintenance requirements. The exact float voltage depends on battery type and temperature. You need to reduce the float voltage at higher ambient temperatures. For me, it would be worth the money to buy a multi-stage charger intended for RV's or boats. Then it will re-charge quickly when needed, but also float at the correct voltage. Some chargers also have temperatures sensing. If the battery will be exposed to a wide temperature range, I think a temperature sensor should be considered a requirement.