Toyota HSD Batteries

[pugmanic]

Hi, daft question...

According to the link below there are different capacity batteries in the various HSD systems;

https://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

Does anyone know if the batteries are interchangeable? Can a larger capacity battery from an RX450H be used to replace a Prius/Auris battery?

[Daox]

If the pack is the same voltage, I'd say most likely yes. However, that really doesn't guarantee you'll get any better fuel economy. If you're fully discharging and fully charging your pack on a normal basis I'd say it could increase fuel economy, but otherwise I'd say its more weight for no gain. It'll also be larger and not fit properly which I assume you already know.

[vskid3]

The Prius is pretty picky about messing with the battery. If you're very lucky, everything will plug right in and the car will recognize the extra capacity. Look at aftermarket/DIY plug-in setups if you want to see how much "fun" it'll be if it doesn't work out like that. Plus when you're done, you might not even see any fuel economy increase unless you live in a hilly area or are otherwise regularly filling the existing battery using regen.

[Ecky]

My guess is that even if it plugs in and functions, the extra capacity will not be recognized or usable.

[LittleBlackDuck]

RX450h battery is totally different layout - it lives under the rear seats.

Simon

[S Keith]

No HSD pack is compatible outside similar models (e.g., Toyota Highlander/Lexus RX450h) with another when looked at as a whole. Those of different capacities are never compatible.

The internals of just about everything are compatible, i.e., the 6 cell modules are compatible.

The Highlander/RX450h are unique in that they use an 8 cell module.

The battery management requirements of packs absolutely prevent one from interchanging them.

It's also a moot point. There would be zero gains and likely a very small loss associated with increasing the weight of the vehicle.

[pugmanic]

Thanks for all the replies. I guessed it would probably not be as simple swap, but doesn't hurt to ask (most of the time).

I am confused by the statements that there would be zero gains and no economy improvements. I understand that there would be a weight penalty, but it would surely be less than adding a passenger to the car.

My daily drive has a mix of urban and motorway (highway) driving, and so the battery is frequently charged to max (80ish %). The battery capacity currently isn't sufficient to complete all of my town driving, so I assumed that a larger capacity would help this part of the journey.

Again - thanks for the responses.

[ECO-AKJ]

Too bad a person couldn't put a couple batteries together in parallel for the HSD

[S Keith]

You are confused because you haven't embraced the reality that 100% of the propulsive energy used by the car ultimately comes from gasoline. The battery needs to be just large enough to allow the hybrid system to work. Excess capacity is wasted. Additional electricity use necessitates replenishment with gas power.

You further likely don't realize that the amount of energy stored in any of those batteries listed is TINY... about 1-2 miles of SLOW pure EV driving. The Gen2/3 Prius pack usable capacity is almost identical to the total capacity of the tiny lead acid battery in back.

Lastly, passengers can get in an out of cars. Increasing the car's weight permanently by 40# will have a measurable negative impact.

Case in point:

Gen1 vs. Gen2 Prius

Gen1 capacity: 1.8kWh
Gen2 capacity: 1.3kWh

They deliberately downsized it because they realized it was too big and heavy - overkill for the application. The underlying HSD components are nearly identical. Most of the gains came from the aerodynamic improvements.

[S Keith]

Originally Posted by FordMan

Too bad a person couldn't put a couple batteries together in parallel for the HSD

That would actually be a MUCH easier solution; however, putting NiMH in parallel can have catastrophic results should any of the cells wander outside the normal operating range, but again, there would be no measurable benefit and likely a penalty associated with the permanent weight increase.

Now is a good time to mention that anyone deliberately trying to extend EV mode of any hybrid through driving style is likely hurting their mileage (excess battery usage must be replaced by additional gas engine running) and hastening their battery demise due to deeper charge/discharge cycles.