The Strobl system used by Schleicher will work fine with the LFP batteries. The only catch is the LFP's need 14.6 V to fully charge and unless the voltage regulator on the Strobl is adjustable, it will likely produce the 13.75 V required by SLA's.

This means that you can connect the Strobl to the LFP's and it won't harm them, but it also won't charge them to full capacity. It will help prolong their working capacity during flight.