Do you really mean a "non-isolated" SMPS, working from the 230V 50Hz ac mains, delivering 16V dc output and load current of 50A ? Then after rectification, the dc bus voltage is around 325V and simplest is a 'Buck' converter. However, remember that if the device becomes shorted under fault condition, the entire 325V dc will be fed to load continuously ! This situation can be prevented by using any isolated version, in which the device will blow itself up due to saturation of the transformer.

sujit k biswas is absolutely right isolated power supplies should be preferred for larger ratings.If you are so sure to move ahead with non isolated you can consider interleaved converters

OK, with your question modified now, I can recommend to use a two-transistor Forward converter for applications upto about 1.5kW, which is popular in industry due to various reasons: 0nly 2 devices are needed, can be controlled from standard low cost IC's, voltage rating corresponds to dc bus voltage plus margin (not double + margin), Of course drive isolation is needed and if interested, interleaved structure can be used.

The solution is in DC-DC converter. At first you need to specify input voltage

and ripple of output. DC-boost or DC-buck or buck-boost will be OK

isolated DC DC power converters are suitable, but you need to mention input voltage...

Best choice for such rating will be Isolated Sepic or Push-Pull DC-DC Converter.  Normally till 1KW, Push pull gives good performance.

Muhammad, remember that push pull converters need semiconductor devices with voltage rating at least twice that of the dc input bus voltage ! Hence, they are not well suited for mains operated SMPS, but may be ok for a lower input dc voltage application. At 230V ac input and 325V dc input bus, the MOSFETs need to be of at least 650V rating. With safety margin, they will be about 1000V rating. Such high voltage devices will have high voltage drop [due to higher Rds(on)] and hence higher steady loss.

There is no AC input.The only input is from the 4S Lithium polymer Batteries.

OK Raj, then this cannot be called as a SMPS but a DC to DC converter ! Sorry that I misunderstood it due to the name. Then it implies that the input is 13.6V to 16.8V dc and the output is to be 16V dc.

Then I agree with Muhammad that for an isolated version, a Push Pull topology will be best suited due to ease of driving directly.

If you choose a non-isolated version (since the voltage difference is small now) then a Buck-Boost converter is the best, but remember output voltage polarity will be reversed, so take care in power and feedback connections. A non-isolated version will of course, give the highest efficiency.

What about SEPIC and ZETA converters they are ideal for high power ratings and also  they have a non inverted output.

Also are buck boost converters suited for such high power rating ?

I cannot comment on SEPIC or ZETA converters since I havent worked with them but Buck-Boost converters are used at more that few kW rating. There is no problem except the size of the inductor. Since all the load energy requirement for the entire cycle time is stored in that inductor during ON-time, and is used to supply the load during the OFF-time only, the inductor size is larger than that of a Boost converter for same input current ripple.

I understood you have 4s batteries for input and want constant, stabilized 16Vdc at output. If this is the situation I'd make a push pull converter with high current power mosfets. Maybe a multistage converter could be a solution, by adding power modules in parallel, using the same control and drive circuitry, like totem-pole drivers. Regards.

This, of course is dependent upon the other application parameters: Input voltage (AC or DC), rate of charge, etc. This application appears to be within the realm of a full-bridge converter topology, but its design is complicated and dependent upon its input voltage. You really need to provide more environmental application information.

The world is a continuum. One must first understand the continuum, then impose ones specific needs upon it. There are many references in the field of power supply design and battery charging. You should do some Google research.