Apart from needing 14 - 14.5 V output, the SMPS must also be able to deliver constant current, it must have a current limiter rather than a overcurrent shutdown. Some SMPS can, some can't. A PC powersupply probably hasn't a usable constant current mode. The SMPS must also allow increasing the output voltage, e. g. by an adjustment potentiometer. A lot of industrial single voltage SMPS can be used as a battery charger, but it must be checked with datasheet first, if it's possible at all and also if this operation is allowed permanently by design, and then verified empirically.