Hello all, I am working on a project with Gen 4 Prius Prime cells and I would like to know if anyone knows what the terminal voltage is at full charge for Prime cells? I'm guessing it will be conservative close or equal to 4.10v but I would really like to know if anyone has scanning software and thus has a hard number for me. I do not need nor want general numbers. I need an exact number hot off the charger. Trying to estimate range in my application based on comparison or Prime to my car at full charge voltage. I cannot divulge what I am working on. Thanks! Jim
It conservative for a reason. It's a small pack for a car of it's size that'll drive at 84 mph in EV mode, if you don't care how long the pack is gonna last. It's not to hard to get the numbers when DrPrius, ScanGauge, Hybrid Assistant or Car Scanner is connected.
Thank you. So, so helpful. Based on measurements I have taken, most manufacturers charge up to 4.07-4.17v to use more of the battery capacity. It isn't too surprising that Toyota is being conservative. It's just how conservative is that which surprises me. They don't want that battery to sit with a high state of charge, ever.
If watching close enough with an app that shows SOC accurately you'll see the first 10% SOC gets used faster than the second 10% SOC and the second 10% gets used up faster than the 3rd 10% SOC. The Primes last 10% SOC flattens out the discharge curve quite noticeably especially when compared to the first 20 or 30%. Not that knowing this would mean much to a normal driver, though could shine some light for somebody interested in pack internals and performance.
OK, I have the Prime pack working in my car. What I would like to know now is at what cell voltage (or pack voltage/95) that the car switches to hybrid mode and fires up the ICE. Can I place a bet on 3.60v? I put 21.1 miles on the pack last night starting at 4.10V and running it down to 3.66V resting voltage. I know that different conditions can result in the Prime kicking on ICE earlier but in easy, local driving what is the transition voltage? You've been super helpful! Jim
My Gen 4 (95 cell pack) consistently fires the engine ( -- SOC on the dash gauge) at 330 volts when the car was new, and now at around 331 volts. 3.4736 empty ( -- SOC engine starts ) I've seen the voltage as low as 325 volts with a tiny couple amp draw on the pack in creep home mode. But the voltage rebound needs to be able to meet the 330 volt minimum when that couple amp load is removed or the engine fires as soon as the sensor determines the rebound wouldn't return to 330 volts. At normal driving speeds with higher loads the system calculates the switchover differently.
Hi vvillovv, I cannot tell you how much I appreciate your responses. They're super! I feel pretty good now that I am running the cells not too far off of what Toyota does. I got 31.3 miles out of a full charge today in non-highway, 45 mph average speed driving. 15C with slight drizzle. Finished with 3.52v/cell, more or less. The weird thing is that I have a digital meter on the dedicated 240V circuit for my evse and it took just less than 7 kWh to fill 'er up (6.7). I am not using a full 95 cells but just shy of that. I expected to use 8.5 kWh with charging losses. It also only took three hours to charge. Jim
6.7 is actually hi for from the wall. A few other members tracked per charge using a kilawatt and - IIRC like - 3.6 was the highest I've seen. And it varies quite a bit in the .range. As the pack ages and or gets abused that number drops into the 5.xx range. You'll see what happens and the range your setup produces if you keep track for a while.
I don't own a gen 4, but from what I understand, the voltage level is restricted to 70% of full charge to preserve battery longevity. This works out to roughly 3 volts per cell, but I'm sure that information is in some technical manual.
It has been posted here in this thread that the range of operating cell voltages for the Gen 4 Prius Prime run from 3.4736 to 3.936 volts per cell. The high end is very conservative to preclude that the car never sits at a high state of charge which can degrade the cells. This is my opinion but that is based on 15 years of experience handling lithium batteries. I have found that you can store lithium at 4.0v for a very long time without significant degradation. That said, I would never leave the cells discharged to 3.4736v for extended periods. 3.85v/cell is storage voltage for lithium that is not LifePo4 or lithium titanate, neither of which Toyota uses in the US.
Ah, I must have missed the part you mentioned above about the Prime pack in your car. I'd be interested in anything you'd like to share about your car, how it works and/or what you like about it.
