How efficient is Charge Mode in Gen 5 Prius Prime?

Generally, it's more efficient to not use it. The function is there for when you decide you will want to have a period running on EV in the future, with low battery now and no access to external charging.

If you're using it, it could well mean you didn't manage your charge effectively - it would have been better to not discharge in the first place, and to have been running in HV mode to save the energy for your planned EV period.

But if you do find yourself with low battery, unable to externally charge, then maybe it is worth running charge mode if you can build up enough EV to avoid a number of warmups. Maybe you're doing a long trip now, and you know there will be a bunch of small trips over the next few days that could be done in EV.

 

If you drive somewhere and cant charge at the destination AND want to use remote hvac before getting back to your car, you must use charge mode beforehand. But then you have to get the battery > 30% so I'm not sure how realistic this use case is.

this is more about convenience than efficiency though but so are half of the extra features anyway.

 

I have to charge the battery out of necessity. When I try to remote start the car, it says something like: "car can not be started because the charge level is too low." This happens unless I put about a third of a charge into the battery.
Seems wrong, is wrong; I hope it gets fixed with an update.

 

Again assuming you had charge to start with, would be better to hit the HV button to stop the charge dropping below 30%.

Never used this function (do we even have it Europe?) So I gather the remote AC won't start the engine and runs only from the battery. Therefore, if you intend to use it, you just shouldn't let the battery drop that low while driving. Switch to HV mode. Letting the battery discharge and using charge mode to refill it is less efficient.

 

It could be a good way to burn off old gas, if you find you're doing most driving in EV.

 

I used the charge mode yesterday on a trip to the Salem Costco. I forgot to charge the EV battery the night before and had only 8 miles of EV range starting out. By the time I left town, I was down to 4 miles of EV range. Using charge mode got it up to 12 miles of EV range which was enough to use driving around in Salem. Driving back, I used charge mode again until I had enough to use for the remainder of the drive home. It works faster than standard 120V charging but your MPG in HV mode will take a minor hit.

 

Someone should actually do a real test on this, but that should be less efficient than the alternative of using HV mode until you had enough to use for the remainder of the drive home.

(This is akin to what the European Auto EV/HV mode effectively does for you with "Predictive EV Drive", alternating between HV and Auto, keeping an eye on the remaining charge versus remaining route to final destination - but it would never go to "Charge").

 

Charge mode is effectively a fast DC charge for those concerned about battery life.

 

That would be interesting to see what the difference is.