Avalon hybrid. What to mod?
 

So I ended up with a 2013 Toyota Avalon hybrid.

• First things first, I want to install a block heater.
• Trailer hitch is also one of the first things I want to do, and then build a small, aerodynamic trailer to pull with it.
• Radiator flaps and wheel skirts would be a nice addon.
• If possible, in the future I'd like to install a heat tank system like on the Gen II Prii.
• A wild idea of mine would be to increase the battery capacity (like with a secondary lithium ion battery) and make it a plugin. There's a company named Enginer that makes kits for this, but they're not cheap by any means.
• An even wilder idea would be to convert to CNG. I think I'd rather mess with the traction battery first though.

Any other ideas of what could and should be modded on a car like this?

Bigger traction battery would be a great start... could do smooth wheel covers and wheel skirts, you know, the low hanging fruit that OEMs seldom touch... belly pan and diffuser if the car doesn't have one already, maybe a lower air dam...

What kind of mileage are you seeing so far? They do pretty good for how big they are.
Toyota ditched the heat tank with the Gen3 Prius and switched to having the exhaust heat up the coolant for faster warm up. Heat tank seems like a complicated solution that only helps in specific use cases. Your Avalon might have a system in place to decrease warm up time, but I haven't looked into them enough to know. If it doesn't, I would lean more towards something like the Gen3 Prius' system than the Gen2.

Does Enginer still actually make kits? Those kits were alright when they first came out, but they don't make sense with all the PHEVs available now.
Unless you have money to burn, I wouldn't mess with adding battery capacity. I think CNG would make more sense and pay off quicker than messing with the battery.

Are there examples of Avalons that have been converted to plug-ins? In other words, is the Avalon designed to run in an EV only mode as it is? If not, I don't see the point in adding battery capacity. If the EV mode is like the Prius, then you'll be limited to very low power and a top speed of something like 40 MPH.

I thought Enginer went out of business due to poor products?

I'm a big fan of all those brave people on here that take on huge projects and would love to see you go forward on such an endeavor, but I wouldn't do it since the money and effort required wouldn't offset the benefit.

That said, there are plenty of projects I take on that have no payback other than increasing my knowledge of how something works. I intend to test the "virtual alternator delete" idea purely for the experience.

I think Enginer bit the dust a while ago, and Plug-In Supply has scaled back these days, if it's still in business at all. The proliferation of viable factory PHEVs has decimated their market.

Whoops, got that backward--looks like Enginer is still kicking (at least, their website is still up), Plug-In Supply is gone.

Thanks!

I get 41mpg. That's nearly all highway. That's what I got when I drove it back home (1,500 miles) going 75mph with the A/C on the whole time. Today I took it on my usual 150 mile route over the mountains. Again I got exactly 41mpg, even with the steep grades. (At least according to the average MPG meter on the dashboard.)

From what I can tell the engine warms up very quickly, so it must have some sort of exhaust heating system. Still, I'd like to warm it up before driving, especially in the winter. We get clear down to -40°F/-40°C on occasion.

A regular block heater would do. I just need to get ahold of a dealer to find out what part I need since I can't seem to find one anywhere on the internet. Then I'd also have to figure out where it goes.

However, something that can heat the engine without being near a plug would be great. And a heat tank doesn't use energy (except the pump). It would add more weight though. I've also thought of a Webasto or Eberspacher fuel burning heater. But those would likely need a small diesel tank to work. There are a lot of situations where I'll have to leave the car for hours where I can't plug it in during freezing weather, hence why something portable would be nice.

I'm not so concerned about heating the engine for comfort or solely for fuel efficiency. I want to make the engine last as long as possible. And cold starts are what do the most damage.

CNG retrofitting doesn't seem cheap either. And yes, the Enginer kits seem quite steep in price. Basically, if I want to save money I'd have to source my own parts instead of using prefabricated kits. And old Chevy Volt batteries seem to be a better bargain than DOT certified CNG tanks. Plus electricity is easier to "trick" into accepting another electric source. Electricity is electricity. But getting the engine to accept another type of fuel is not as easy.


My Avalon with has an EV mode that quits at 25mph, although I can get it to drive with the engine off at speeds below 47mph.

But that's not entirely the point. If setup right the car could run in a gasoline/electric blended mode for long stretches. So instead of 41mpg I might be able to see 60mpg or better. Of course I'd have to figure in the cost of electricity. But with electricity costing 10 cents per kWh around here (and lots of free charging station including at my place of work) I wouldn't worry about it that much.

Also I do a lot of highway mountain driving. Even if I didn't make it a plugin-hybrid, just having enough battery capacity to absorb my descents would be great.

Enginer seems alive, well, and making outlandish claims: Enginer | Solar Powered Prius Plug-in PHEV Conversion Kit with Lithium-Ion | Hybrid

If better highway mileage is your focus, I’d start by improving aero... I’m sure Toyota left some fruit on the tree... smooth wheel covers and rear wheel skirts would be a great start, could maybe get you to 43-44 highway...

Messing with the battery sounds much easier than a CNG conversion, plus IIRC any alternate fuel system needs to be EPA-certified. That's why aftermarket CNG conversions might not be so popular there as they are in less-regulated markets.

Ya. With CNG the tanks are expensive, take up a lot of room, and need to be changed (according to DOT regulations) every 10 to 15 years. Also to be able to use my home natural gas I'd need a way to compress it to 3,600psi. I've been looking for such a compressor and they are hard to find. Then there's integrating it into the engine control system. I could do a non-certified job and probably get away with it seeing how there's no emissions check where I live. Of course that could change some day.

Making a battery that falls into the same voltage range as the NiMH traction battery shouldn't be that hard. IIRC, NiMH cells range from 1.0V empty to 1.4V full. Three NiMH cells would be identical to a typical Li ion cell, going from 3.0 to 4.2V. The auxiliary battery could be connected in parallel and have some sort of BMS that could disconnect it in some extreme case or when not needed.

The only problem with this idea is that the hybrid system seems to want to keep the traction battery at around 70-80% charged, from what I gather on the dash board. Going up mountains it doesn't let the charge drop below what the dash indicates as around 50%. Driving my Leaf over these same passes I saw the batter SOC increase as much as 10 percent going down these hills. That indicates to me that I'd need to absorb as much as a 2kW of energy going down a typical mountain pass. But if the hybrid system keeps the battery voltage up near 75% SOC, I'd need 8kW of capacity to make it useful. Of course this is all just guessing. I'd need to track actual battery voltage and current before deciding on how an auxiliary battery should be constructed.

Of course it would be even better to have a system like Enginer's that has an inverter between the two batteries. That way you could chose how the energy in the auxiliary battery is to be used.

Just doing a little math here.

The Avalon's battery is made of 34 7.2V (nominal) modules which in turn are made of 6 1.2v (nominal) NiMH cells. At full charge (1.4V per cell) the total voltage would be 285.6V. If you charge Li ion batteries up to 4.2V per cell that would be the exact equivalent of 68 Li ion cells. (Of course keeping it down to a more reasonable 4.1 or 4.0V max per cell wouldn't be hard to do the bigger the battery is.) Coincidentally the minimum and nominal voltages are exactly the same too.

However, NiMH batteries can be charged at a higher voltage than their max voltage (due to battery resistance, kind of like charging a lead acid battery to 14V and taking it off the charger and seeing 12.8V). So in reality the Synergy drive system could possibly put out up to 326V! That would fry a Li ion battery of 68 cells connected in parallel, expecially if it were near full charge (like in a plug-in hybrid)! Some sort of battery management system would have to protect the Li ion battery under regen near full charge.

According to Car and Driver, the Avalon's battery is capable of delivering some 141hp. That puts us at around 500A. Of course the Li ion and NiMH batteries would be helping each other. But it would be best to match the current since the Li ion battery may have less resistance than the NiMH battery.

So for a parallel LI ION battery, we need 68 in series capable of delivering close to 500A. Maybe 1,700 of 20A rated 18650's? It seems like I've seen some 1300mAh 20A cells on eBay before for some $150 per 100 box. That would put me at some $2,550 for just the cells (if I could find them for that price) but would add nearly 8kWh. I need to check out the Chevy Volt battery specs too.

Not sure if increasing the voltage while keeping this very same battery pack would be worth the endeavour. Eventually looking at larger-capacity cells with the same voltage, even though they would naturally become bulkier, might not harm the overall durability of the system. But you should always keep an eye for temperature and other factors that might affect them.

Isaac, After following your other thread I think you arrived at a great choice in vehicles. My recommendation of “what to mod?” would be to start with low cost/best return mods. It looks like Toyota has done a good job with aerodynamics but the underside may be an area to clean up. I have a full, front to rear coroplast belly pan, side skirts and rear diffuser, with extra insulation under the engine to retain heat when parked. You may be able to block the upper grill and still stay cool enough, especially in winter. (Make sure you have a digital temperature gauge to monitor temperature.) I use a tank style engine heater and a stick-on Katz heater on the oil pan. On cold mornings I will use both. The Katz was added later and I was amazed how quickly it warmed the whole engine compartment.

A small ice chest with multiple pre-dampened “cooling towels” can help you run longer without A/C in summer. Tint as much of the glass as you can.

To retain efficiency and handling on our mountain roads, adopt the Lotus philosophy and “add lightness”. I have removed the rear seats and spare tire to take over 100 lbs from my car.

Ok. So my first mod to the car. An OEM cartridge style block heater. Installed and ready to use and used already.

I do need a thermometer for monitoring before blocking the grill. I'm not sure how good of an idea that would be with all the mountains I have to climb and descend. I would love to do automated grill shutters. Not sure how easy that would be though.

Belly pan and wheel skirts are on the list. I also want to weld up my own tow hitch. The ones I've seen ready to purchase hang down and would affect aerodynamics. I want one that comes through the bottom of the bumper.

Yeah I'm surprised there isn't more competition for "hidden" hitches (Hidden Hitch the company makes regular hitches that aren't hidden). The only outfit I know of is Torklift, and they have a limited selection, as well as 2.5x the cost of a normal hitch. You'd think with heavy competition for normal hitches, and the prospect of making 2x more for the same amount of steel and fabrication, there would be a market for hiding the hitch behind the bumper. Maybe most people simply don't care if there is a steel bar hanging below their vehicle.

I just uncovered the traction battery for the first time. (Cover is held on by Velcro!) Anyhow, there seems to be a lot of space around the battery where I could add some sort of heating pads. On those -40° days it would be nice to start out with a warm battery and engine.

I also just threw a space heater in the trunk that I will be using to warm the cabin before driving. Some of my drives are very short.

I'd like to add more engine heating/insulation. One idea I have is to install a tank type heater, but with a pump. Normally the problem I have with tank type heaters is that it's hard to install them just right so that they draw water from down low and perculate up high. And usually when you do them right then the flow is backwards from what the engine pumps while running, so they're useless if you're trying to use them with the engine on. But with a pump that problem would be solved. Plus, if I get enough heat, I could turn on the car and heat the interior at the same time. If there's enough heat coming from the tank heater then the engine should not turn on, or not stay on for very long, while I defrost the windshield and heat the interior. I'm not sure if it can be done, but since the engine apparently already uses electric pumps, I wonder how hard it would be to wire it up to turn on the pump that goes to the heater core and put a tank type heater inline with that.

Max battery discharge current is about 150A. Not sure where you got that 141hp number, but that's just not the case.

Heaters that aren't forced-convection based aren't likely to be very effective as you're trying to heat an 82# insulated block of mostly nickel. If you installed some sort of forced air heating that pushes air in from the trunk and exits in the cabin, it would be double plus good as you'd heat the interior as well. This also increases the surface area you're heating by about 30X.

Think multi-speed/multi-heat hair dryer (maybe not strong enough from an airflow perspective).

The thermistors are on the bottom of the pack, so they will be the first to be heated even if the pack itself is notably colder. I suspect it would need to run for quite a while to ensure the pack is truly above 50°F at which point the hybrid system is pretty much unrestricted.

Thanks! I was wondering about that current rating too since 141hp didn't make all that much sense.

Anyhow, one problem I'd have with blowing hot air through the battery is that I don't want to overheat it. It's one thing to set a heating element or light bulb next to the battery all night with a thermostat on the case to shut it off if it ever gets too warm and another to blow high power hot air through the battery and somehow set it up to shut off before it gets too hot.

Plus I got to think about how much electricity I'm using. If I got 200W in the block heater plus another 1000W for a tank heater that leaves me with about 200-300W for heating the battery, unless I shut off one heating system to turn on another.

But I still like the idea of heating the battery more efficiently and quickly. The same with the engine. Ideally it would be best to heat these up quickly right before taking off instead of wasting heat all night through "trickle heating."

The issue is the complete waste of effort with radiant heating. It will be grossly inefficient and slow. You are heating sheet metal radiantly, which then radiates externally (wasted) and internally onto PP/PPE plastic with very low thermal conductivity and a cavity that permits heat escape out the inlet. Furthermore, the temperature sensors are on the outside, which will react relatively quickly even when the cells are bone chilling code. This could permit the car to use full hybrid function on a very cold battery. That will kill it in no time.

I linked a multi-speed, multi-heat dryer. High fan and warm heat is highly unlikely to get the battery too warm. They LOVE to be 90-100°F, and it will likely take many hours to get there.

30-60 minutes prior to start would probably suffice.

Thanks! I'll look into it. I'll have to look and see where the air normally comes out. I assume somewhere on the right side, opposite of where it normally enters on the left side.

Although not related to better fuel efficiency, unless avoiding getting stuck in a snowbank and having to sit for hours with the engine idling counts, I've run into a problem with a set of winter tires I bought and the TPMS sensors. I got used rims for this car with Toyota TPMS sensors and also got a Techstream cable and program to be able to put the new codes into the ECU. But I've run into a problem. The codes are written on the sensors themselves. But the wheels already have the winter tires on them. So now I either have to take the tires back off, or just drive around with the TPMS light and warning beeper on all the time.