diff --git a/interfaces/cython/cantera/onedim.pyx b/interfaces/cython/cantera/onedim.pyx
index e3a3f48bd..505ad13f8 100644
--- a/interfaces/cython/cantera/onedim.pyx
+++ b/interfaces/cython/cantera/onedim.pyx
@@ -23,7 +23,7 @@ cdef class Domain1D:
 
         self.gas = phase
         self.gas._references[self._weakref_proxy] = True
-        self.have_user_tolerances = False
+        self.set_default_tolerances()
 
     property index:
         """
@@ -140,6 +140,14 @@ cdef class Domain1D:
         for name,(lower,upper) in kwargs.items():
             self.domain.setTransientTolerances(lower, upper, self.component_index(name))
 
+    def set_default_tolerances(self):
+        """
+        Set all tolerances to their default values
+        """
+        self.set_steady_tolerances(default=(1e-4, 1e-9))
+        self.set_transient_tolerances(default=(1e-4, 1e-11))
+        self.have_user_tolerances = False
+
     def bounds(self, component):
         """
         Return the (lower, upper) bounds for a solution component.
@@ -576,6 +584,18 @@ cdef class IonFlow(_FlowBase):
             else:
                 (<CxxIonFlow*>self.flow).fixElectricField()
 
+    def set_default_tolerances(self):
+        super().set_default_tolerances()
+        chargetol = {}
+        for S in self.gas.species():
+            if S.composition == {'E': 1.0}:
+                chargetol[S.name] = (1e-5, 1e-20)
+            elif S.charge != 0:
+                chargetol[S.name] = (1e-5, 1e-16)
+        self.set_steady_tolerances(**chargetol)
+        self.set_transient_tolerances(**chargetol)
+        self.have_user_tolerances = False
+
 
 cdef class Sim1D:
     """
@@ -898,8 +918,7 @@ cdef class Sim1D:
             rtol_ts_final = [dom.transient_reltol() for dom in self.domains]
 
         for dom in self.domains:
-            dom.set_steady_tolerances(default=(1e-4, 1e-9))
-            dom.set_transient_tolerances(default=(1e-4, 1e-11))
+            dom.set_default_tolerances()
 
         # Do initial steps without Soret diffusion
         soret_doms = [dom for dom in self.domains if getattr(dom, 'soret_enabled', False)]
diff --git a/src/oneD/IonFlow.cpp b/src/oneD/IonFlow.cpp
index 860b2cb09..f7dd79e51 100644
--- a/src/oneD/IonFlow.cpp
+++ b/src/oneD/IonFlow.cpp
@@ -43,9 +43,13 @@ IonFlow::IonFlow(IdealGasPhase* ph, size_t nsp, size_t points) :
     // no bound for electric potential
     setBounds(c_offset_E, -1.0e20, 1.0e20);
 
-    // Set tighter negative species limit on electron concentration to avoid
-    // instabilities
-    setBounds(c_offset_Y + m_kElectron, -1e-16, 1.0);
+    // Set tighter negative species limit on charged species to avoid
+    // instabilities. Tolerance on electrons is even tighter to account for the
+    // low "molecular" weight.
+    for (size_t k : m_kCharge) {
+        setBounds(c_offset_Y + k, -1e-14, 1.0);
+    }
+    setBounds(c_offset_Y + m_kElectron, -1e-18, 1.0);
 
     m_refiner->setActive(c_offset_E, false);
     m_mobility.resize(m_nsp*m_points);