Part to use for solar charging terminal
If you have only 3.3 or 5V logic high to switch on a 12Vdc motor, You may want to consider short circuit overload, thermal overload and inductive turn off effects. The better FETs with low Ron resistance usually require a bigger gate voltage to perform this. There are some chips which generate this internally using a voltage pump (MOS charge pump cct) to generate this higher internal gate voltage.

Conclusion 
I recommend the TPS2204  chip, capable of 2A sustained in an 8 pin DIP package.

Additional precautions are given here and buy here for $2 /1pc or $1 /1kpc


You can put an Alum.elect. cap. (>=16V) on the output to suppress commutation noise and use twisted pair wire. This driver can handle large capacitance and surge currents.