Reduce Max. Current while DC Charging with CHAdeMO

Our 2018 Toyota Prius PHEV is an Japanese import and has a CHAdeMO port for DC charging. We have used it once - it charged from 0% to 80% in 17 minutes providing 4.8kWh of power i.e. a rate of 17kW at a current of 74Amp. (I've described this elsewhere in PriusChat.)

Since frequent fast charging is generally accepted as bad for the battery but we'd like to be able to charge quickly e.g. holidays, etc, my question is - can I somehow reduce the max current by 1/3 (for example) e.g. to 50 Amp? This would presumably significantly reduce the damage to the battery but only increase the charging time by a small amount e.g. 8 minutes at 50 Amp.

The in-built current limiter in the PHEV only applies to AC charging i.e. to 8 Amp, but doesn't effect the DC charging rate. (Anyway, a DC limit of 8 Amp would be far too low for our purposes.)

 

Thank you for these insights into the complexities Toyota considers when limiting the DC charging current, drash. Our typical, intended scenario for CHAdeMO charging would be daytime at about 25degC (75degF) after driving for an hour or so in HV mode and a battery depleted for maybe 15 to 20 minutes before re-charging. We would like to almost immediately charge while having a short break then continuing on the journey - so driving both beforehand and afterwards. This would seem to me to be the intended scenario for CHAdeMo charging. If there is time to charge from a 230V AC supply then I'd choose this as it's healthier for the battery and probably cheaper (or free) where I'm likely to be.

I am hoping that there is a hidden setting where the car can be told to never charge above a certain current e.g. 50 Amp, or less if Toyota's algorithm recommends an even slower rate. Such a setting might, of course, only be accessible using an OBD2 connection.

 

The design and build of this device would be beyond me, unfortunately. As mentioned above, I am hoping there is a menu position where I could override the car's automatic current control settings to limit to a max. of about 50 Amp (perhaps only accessible using an OBD2 connection). As noted by drash above, there are many factors to consider - hopefully Toyota's charging regime already adjusts the charging current accordingly, so I' like to be able to limit it's set current to a lower maximum.

With the probable future increase in demand for fast charging as EV use expands it would seem very useful to be able to fast charge with minimal, if any, damage to the battery. As I've described elsewhere, our single trial using CHAdeMO charged from 0% to 80% in 17 minutes. This time was too short to enjoy a relaxed drink, a bite to eat, and a visit to the rest rooms - so after the fast DC charge the car sat around doing nothing for about another 20 minutes. This extra time could have been used to reduce the DC charging current.

Although unlikely to be possible with our current PHEVs, best of all would be if we could set the DC charging regime to be finished after a certain period (set depending how long we're away) and let the car decrease the DC charging rate to the minimum current to charge in that time. That would minimise battery damage (and spread also the loading on the power grid).

 

Hi black_jmyntrn, I'm delighted at your enthusiasm, however, if you did happen to head to Maine you'd be driving in the opposite direction. I'd also suggest a boat or plane as it's a long way ...

Yeap, Elektroingenieur hit the nail on the head - ours is a [2018, Gen 2] right-hand drive Prius PHV car built to Japanese specifications. And there's water between us (... lots of it).

But don't let the distance and waves get in the way of what might be a very interesting bit of fun with really useful purpose. It is amusing that you'd like to speed up charging (a lot) while I'm looking to slow it down (a little). I'm happy to try moving things along.

We have an 8.8kWh battery (giving ca.40km/25mile range) while your Gen 1 Prius has about half this i.e. 4.4kWh (giving ca. 20km/12mile range) according to https://en.wikipedia.org/wiki/Toyota_Prius_Plug-in_Hybrid#Battery_and_range_2. Installing a 50kWh battery is an interesting goal, however, since a battery of this size weighs much more i.e. about 11 times a 4.4kWh battery, then you'd have problems with weight and therefore chassis strength and braking capacity. Also space would be an issue. Presumably you will have to remove the ICE/petrol/gas engine to be able to make your conversion work, so you'd be changing a hybrid into a full battery-electric vehicle. You'd probably be wise to check whether your final design could be certified as road-worthy and insurable by the relevant authorities, etc. before dismantling and modifying. (It might even be cheaper to buy a used BEV and modify that.)

So what's the next step? Presumably I need to buy a OBD2 connector and install an app onto a mobile phone or to connect to a laptop? I'd need advice regarding which combination connector/software is best. Can you/anybody help with this? Hopefully the Prius PHV/Prime owners have recommendations?

 

Thanks for the tips. The Traction Battery Heater was already ON (and I've left it so). Since it can get a bit cold here in winter it is useful.

There isn't a Traction Battery Cooler setting at all. I assume that means the equipment is not present in this version of the car and so wouldn't be accessible even with OBD2 etc. The air temperature here seldom rises to 30degC (90degF) or above so a Traction Battery Cooler might just be less important than in US e.g. California.

 

I searched again through all the MID settings and couldn't find a setting for the Traction Battery Cooler, which I expected to be in the same menu as the Traction Battery Heater. It wasn't there so I also looked elsewhere without success. I have read somewhere that a Traction Battery Cooler is not fitted in all models of the Prius PHV. (I have a vague memory that it might be the perhaps the English models, but I could be wrong here.)

I'm hoping to get advice regarding which OBD2 connectors and apps/programs are best. Then I will indeed monitor everything I can. Hopefully I can also find a way to limit the max. DC current at about 50Amp instead of current 74Amp - this is my immediate goal to open the way to using fast charging more often.

 

Hi Elektroingenieur, thank you for your earlier post. Unfortunately I can't read Japanese, so I can't read the handbook which came with our car nor the online PDF you refer to. I would certainly like a handbook for our car which I can read but haven't been able to find one for our 2018 Prius PHV import from Japan. (Most online handbooks are for US or English version of the Prius.)

You post elsewhere regarding CHAdeMO charging was interesting especially as it applies to the Japanese version (which we have). So I have a few questions:

1. An online translator converted that short comment in Japanese by Toyota as "There is no problem if you use the quick charge about once or twice a day. However, we recommend that you refrain from excessive rapid charging as it may affect the capacity of the drive battery." Do you know if "rapid charging" refers to DC CHAdeMO charging at ca. 70Amp-75Amp or faster AC charging at 16Amp (maybe 32Amp)? (I wonder what "excessive" means if a daily fast charge is possibly acceptable.)
   
2. Was that comment relevant to a Japanese 2018 Gen 2 Prius PHV or something possibly rather different e.g. the Gen 1 version?
   
3. This comment by Toyota suggests that I shouldn't worry too much about DC fast charging maybe 10 to 20 times a year mainly while on summer holidays.
   
4. Do happen to know where I can a find a handbook in English for our Japanese import version of the Prius (German would also be OK too)? Or a translation of the PDF your link to a Japanese Owner's Manual refers to?

 

Thank you. Could it be that "rapid charging" refers to DC CHAdeMO charging at ca. 70Amp-75Amp rather than just faster AC charging at 16Amp (maybe 32Amp)? (It's probably CHAdeMO charging but I'm just being cautious here.)

In light of the above I would still like to reach my original goal of reducing fast CHAdeMO charging from over DC 70Amp to a max. of DC 50Amp - especially when my driving breaks on trips are longer than just 17minutes anyway and more like about half an hour, so there's absolutely no need to push the upper limits of rate of charging.

 

While researching the OBD2 connector which you indicated I found the following comment: "MX+ supports all legislated OBD-II protocols, plus advanced Ford & GM vehicle networks (MS-CAN and SW-CAN). MX+ works with all 1996 & newer cars and light trucks sold in the United States, and also supports EOBD, JOBD, and all other international variants of OBD-II. If you don’t require access to advanced Ford & GM networks, consider purchasing OBDLink LX Bluetooth." Do you have any thoughts regarding this comment e.g. use instead of the OBDLink LX Bluetooth if there are any advantages?