Disabling DC/DC Converter Fuse Removal

That equation is entirely unrelated to this topic. The power required to drive a vehicle at a constant speed (15.2kw) is unrelated to a power draw on an electrical system measured in watt hours.

 

It is only relevant during ICE operation during cruising or acceleration. Maybe it is not entirely irrelevant, and you are correct that it would technically be a 4% increase in that condition, but the reason it is not entirely relevant is because nobody spends 100% of their drive time cruising with the ice on at peak efficiency.

In my 33 mile commute, I have 10 miles on a highway, and 20 miles in stop and go traffic with many lights where the ICE is off. For those 10 miles on the highway I would be getting about 4% as you said, however a 600 watt drain on a car going 0MPH has a much greater effect. On top of that, cruising at 15kw is the ideal power band for best efficiency. You cannot say that if you spend 3 minutes at at light and lose 1.5% SOC that your engine is going to run at that same peak efficiency to replace that lost charge. In fact, if you get caught in a situation where the ICE kicks on to replenish the battery while you are at a light, then that 600whr has a much more devastating effect on mileage considering the ICE is running far more inefficiently to work to replace that power.

To digress, I appreciate your input, and this experiment is one of the reasons I am trying to get your Priidash up and running (laptop crashed and I have not been able to upload those files!). None of this would be possible without the use of Priidash I would add.

 

Vertex you are 100% correct about the efficiency and heat. My power supply design would only be 50% efficient, and probably less since I will have tons of heat to remove. However, the sense line does not determine whether or not the DC/DC runs. It simply tells the converter what voltage to work at based on battery charge state. The only proper way to run this system would be with a disable Prius converter. It would be nearly impossible to do a current sharing system with the prius converter. In order to force the Prius coinverter to NOT provide power, my system would need to run at a higher voltage than the Prius converter. This is dangerous and could easily backfeed into the Prius converter and destroy it. I would need to install a blocking diode which is simply to much work. It would be easier to just disconnect it, or preferably install a relay to connect/disconnect it. In the case that my unit runs out of power. Your idea about the LiOn batteries is a good one, but I am trying to keep this as cheap as possible simply to get my results. Depending on the results will depend if I want to permanently implement this in my car. So far my costs are as follows:

3 x 105Ah 12V SLA Batteries: $25/ea (brand new)
Electronic Components: $30 total
24V Charger: $80

 

There is a scrapyard near me that sells the batteries. They get about 3 in per week. They are SLA industrial type. Where they get them I do not know, but everytime I've bought batteries from them, they give you a 90 day warranty as well as the warranty on the battery itself, and the date of mfr is always within 2 months.

 

I am not quite sure I understand your suggestion here. You can't really ONLY connect the DC/DC to the battery. The battery is tied in with the entire system including the DC/DC. The battery has only one positive connection and it runs to the DC/DC as well as the junction box to power everything else. The only way to run two systems at the same time effectively is to run them in parallel and run MY system at a higher voltage than the Prius' converter. In theory this seems like it would be fine since the car would eat out of whichever converter is at a higher voltage and the other would sit idle. However, it is impossible to properly current share the two converters thus making it possible for my system to backfeed into the Prius DC/DC potentially damaging it. I would need to put a blocking diode on the Prius converter, which is a really big undertaking....Could you explain what you are talking about a little clearer?

 

To test the mod, I would absolutely do an objective test. I would do both tests in the same day to keep the wind and temperature roughly the same, on the same road, at the same speeds for the same amount of time. I would also do a mixed driving test (city/hwy) in where I drive the same route making the same stops and I will have set speeds at which to drive and a specific RPM range to stay within. The whole purpose of this is to get real results. I would be doing myself and the test a great injustice by being biased just to get a desired outcome. Again I state my projections to be:

5% all highway
10-15% mixed
15-20% all city (lights, stop signs, etc

I would assume an additional 3-5% for cold, night time, or rainy conditions or a combination thereof.