battery: weigh voltage based estimate more when it's low

This is a minimal change to make it harder to crash a
vehicle with an empty battery if the capacity was set wrong.

The disadvantage is that the state of charge estimate will
fluctuate more under load.

We need better documentation and improvements to the estimation.

src/lib/battery/battery.cpp

@@ -239,10 +239,10 @@ float Battery::calculateStateOfChargeVoltageBased(const float voltage_v, const f
 void Battery::estimateStateOfCharge()
 {
 	// choose which quantity we're using for final reporting
-	if (_params.capacity > 0.f && _battery_initialized) {
+	if ((_params.capacity > 0.f) && _battery_initialized) {
 		// if battery capacity is known, fuse voltage measurement with used capacity
 		// The lower the voltage the more adjust the estimate with it to avoid deep discharge
-		const float weight_v = 3e-4f * (1 - _state_of_charge_volt_based);
+		const float weight_v = 3e-2f * (1 - _state_of_charge_volt_based);
 		_state_of_charge = (1 - weight_v) * _state_of_charge + weight_v * _state_of_charge_volt_based;
 		// directly apply current capacity slope calculated using current
 		_state_of_charge -= _discharged_mah_loop / _params.capacity;