Hybrid Aligned Nematic (HAN) devices filled with highly ionic liquid crystal materials screen out the internal bias due to surface polarization, making it possible to determine the flexoelectric sum, e(1) + e(3). A transient change is observed in the device response due to differing polarities of an external offset applied to an AC signal, with a time constant similar to the characteristic ion relaxation time in the material. Assuming ions screen out the internal bias, data-theory fits in the low frequency, low voltage perturbative regime gives a value of /verte(1) + e(3)/vert = 10 pCm(-1) for the standard commercial eutectic E70 nematic liquid crystal mixture.