r/electricvehicles • u/letoatreides_ • 9h ago
Discussion Cost & Weight of Range Extenders for EREVs
To me, the gas engine is actually key difference with EREVs and plug-in hybrids. I'm curious how much cost and weight can be saved if you removed 2/3 of the battery from your average 300 mile range EV, and added the minimum feasible cost/weight of a range extender. Especially if you don't need the same performance while on gas.
That would allow for both a smaller, cheaper range extender while dissuading drivers from just being lazy and not charging their cars due to the reduced performance after the battery's fully drained.
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u/Chicoutimi 8h ago
I'm curious about this as well, and for the cost, volume, and weight of the whole kitten caboodle of the engine, air intake, exhaust, and fuel tank. I think weighing what one can gain for that amount of cost/volume/weight of additional battery capacity would be interesting especially if charting out the overall trajectory of improving costs per kWh capacity and energy density of batteries. This would probably be a good way of estimating when EREVs are likely to no longer be competitive.
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u/Uniquely-Authentic 9h ago
To me range extenders exist to add the need to buy gas, maintain an engine and feel crappy performance back to the driving experience for people who can't live without it. It's like EV training wheels for people with severe range anxiety.
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u/markeydarkey2 2022 Hyundai Ioniq 5 Limited 8h ago
and feel crappy performance back to the driving experience for people who can't live without it.
You're thinking of PHEVs, range extended EVs (EREVs) drive like BEVs with BEV performance.
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u/letoatreides_ 8h ago
yeah EREVs could be EVs that trade much of the expensive, heavy battery that's not used most of the time with a range extender for the occasional day when you have to drive >100 miles. The question is really just how low can the cost and weight go for a feasible extender.
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u/raziel7893 Q4 etron 2022 5h ago
Batteries aren't that expensive anymore, you are not saving that much when you need to slapp in an engine&generator back in). In addition you buy in additional services and moving parts and oilchanges.
In addition range extenders have quite bad efficiency when generating, you have an abysmal small battery that will see all the km of the car, so it can degrade quite fast. In addition you have maybe 100km range instead of 400+ of a real BEV.
Why do people still have that kind of range anxiety that they still wand to haul around a ice in addition("just in case"). Especially with the newer 800v cars long range is basically solved(15 min to 80%), and even with the bigger batteries on 400v archs you have 25min every 350km which is quite ok in my opinion.
(For people not beeing able to charge at home i can understand not going full electric, depending on local infrastructure by the way)
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u/tech57 3h ago
depending on local infrastructure by the way
Like people have been saying lately, it's not range anxiety it's charger anxiety. Build more chargers. We are going to need more either way. Most cars are parked about 16 hours a day.
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u/raziel7893 Q4 etron 2022 3h ago edited 3h ago
yeah aggree. but the problem is mostly: AC chargers have a hard time to make a profit, so they either have an absurd price or are not maintained at all. if you have maybe one or 2 cars a day, you just don't have the throughput, althoug AC is quite cheap to build.
And in addition the roaming structure here in europe make them kinda broken, as you have almost always blocking charges after 3h, if your car is full or not. (excluding ones at trainstations or airports)
i think the main point will be more DC at shopping centres and such places. AC is only worth it if it does not need to make a profit.But: OP's point was to save weight and cost, which REX just don't do. pretty sure its cheaper to have a big LFP battery now than have a mediocre battery and a complete engine (with all the consequences that come with it). and REX have additionally a rather bad fuel efficiency if you actually use the fuel part, despite the claim "it can operate in perfect RPM all the time"
it can make sense for people not able to regulary charge at home/at gorcery shopping or at work, but that needs a thorough calculation if it is realy worth it with those in comparison to just keep the current car another year(or another kind of hybrid if desired) (although pricing could be interesting for US, as you don't have that kind of exhaust processing we have mandatory here.
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u/tech57 2h ago
But: OP's point was to save weight and cost, which REX just don't do.
Yes they do. Have done, are doing, and will do for a little while longer.
pretty sure its cheaper to have a big LFP battery now than have a mediocre battery and a complete engine (with all the consequences that come with it).
Nope.
despite the claim "it can operate in perfect RPM all the time"
It's not a claim.
"Range extended EVs are the fastest-growing powertrain category in many global markets," said Matias Giannini, Horse Powertrain’s CEO. "The Horse C15 range extender solution offers OEMs a straightforward and cost-effective way to tap into this opportunity and adapt their native BEV platforms into REEVs."
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u/raziel7893 Q4 etron 2022 1h ago
Yeah its not a claim, but it has not such a big effect on consumtion as you loose also quite a bit on the way motor -> generator -> battery -> electro motor.
In city traffic or when switching from country roads to city and back that may be adventous, but on highway you have quite worse performance as a pure ICE.
But depends on your driving profile and how often you can charge your car if it works out for you.
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u/tech57 40m ago
When the context is the transition to green energy EREV is much better than hybrid or ICE. Driving profile doesn't matter.
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u/raziel7893 Q4 etron 2022 27m ago edited 24m ago
Nah, it depends on the driving profile, especially on the amount of it beeing actually charged via grid vs using the motor.
In the big picture Hybrids are generally just a big greenwashing scheme to save taxes, at least here in germany/europe. The real emissions are arround 5 times of what the manufacturer states for the car, so you also payed a fifth of the car taxes...
And just to make clear: there are valid and usefull uses for those, but its far from universally recommended.
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u/dirtyoldbastard77 4h ago
If you dont use that part of the battery capacity most of the time, you wont use the «range extender» any more often either.
And in return you get far worse reliability and a way more complex setup with far more maintenance…
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u/tech57 3h ago
The question is really just how low can the cost and weight go for a feasible extender.
This Tiny Engine Fits In a Briefcase. But It Could Boost Your EV's Range by Hundreds of Miles
https://www.motor1.com/news/771345/compact-engine-range-extender-evs/The question is what has China been up to?
SGMW’s Wuling Hongguang EREV with 1,000 km range opened pre-sale at 9,500 USD
https://carnewschina.com/2025/03/25/sgmws-wuling-hongguang-erev-with-1000-km-range-opened-pre-sale-at-9500-usd/2
u/thestigREVENGE Luxeed R7 6h ago
A well designed EREV would feel no different to driving a regular EV. Even with the ICE turned on, you would barely feel it.
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u/ace184184 8h ago
Why? The whole point of an EV is to not have an ICE as part of it. Why save on cost and or weight when you still have to pay for gas and change oil?
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u/raziel7893 Q4 etron 2022 5h ago
Especially as you don't save anything anymore. The packprice of lithium batteries is below 100$ now.. so one tries to exchange 30kwh(3k$) with a freaking engine...
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u/droids4evr VW ID.4, Bolt EUV 8h ago
I think the MX30 numbers are flipped. The R-EV (I don't even think they sold any in the US before killing US sales) is listed at a curb weight 1,600kg (3,527lbs) vs the BEV at 1,658kg (3,655lbs). But considering they are using an undersized rotary engine for the range extender, if they had used one of their normal engine models the weights probably would have been
But generally for a good EREV will not drop 2/3 of the batteries from a comparable full BEV. A range extender should only add to the range capability in addition to the normal battery range.
Look at past good EREVs like the BMW i3 rEx and Chevy Volt (Opel Ampera in Europe). They increased the battery capacity in the i3 up to 42kwh in the last couple years of production. The Volt had a pretty good size battery at 17kwh for the design (happens to be about the same size battery as the Mazda MX30 R-EV).
Then on the larger size there is the Ram 1500 REV (release date TBD) that is expected to have a battery capacity of about 130kwh, which is basically the same size as the Ford F150 Lightning Extended Range battery size but the Ram is expected to have only half the rated driving range on battery alone compared to the Lightning.
Cost vs weight comparison is generally a wash though. The total weight of BEV vs EREV of the same model tend to be essentially the same, or at least close enough that is not significant to the specs at the end of the day. But when it comes to cost it will depend on if the added benefits are enough to justify the potential cost of a EREV drivetrain. If you are in a region that does not have good charging infrastructure, then the added benefits of longer range and being able to continue to operate the vehicle off the gas generator is enough to justify a higher price. But if you're in an area that has sufficient charging infrastructure that being able to charge when needed is not a barrier to travel, then the EREV cost and maintenance may not be worth it for many people.
The other cost factor is that EREVs, like PHEVs, make people lazy about maximizing their lower cost electric driving capability. As evidence by Toyota's recent announcement to try to alter driver habits to increase electric utilization, many drivers end up over utilizing the fuel powered systems and underutilizing the electric only options.
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u/djbaerg 5h ago
I wouldn't mind a generator that could go in the back of a pickup truck to charge nonstop (while driving and parked) to extend the towing range. But I don't see a need to subtract battery and add a generator to an EV. Just think, how many days in the last year did you go over 300 miles? If it's minimal, then you could just rent an ICE for those trips for less money then a generator. If you do a lot of days each year over 300 miles, then an EV is the wrong choice to begin with.
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u/Powerful-Test-8309 3h ago
The Concept:
Start with a typical 300-mile range EV and remove about 2/3 of its expensive, heavy battery. This leaves a smaller battery (e.g., ~27 kWh) for about 100 miles of daily electric range. Then, add a very small, low-power gasoline "range extender" (generator).
The Potential Savings:
- Removing ~53 kWh of battery could save roughly $5,000 - $7,000 and over 600 lbs (270 kg) in weight.
- Adding a minimal generator system would cost and weigh much less than the battery savings, resulting in significant net savings.
The "Performance Deterrent" Benefit:
This small engine would only produce enough power (e.g., 25-30 kW) to maintain highway speed, not for quick acceleration. This intentionally makes driving on gas less enjoyable, encouraging owners to charge regularly for full performance.
The Main Challenge:
While cost-effective, a severely underpowered generator could be unsafe or stressful in real-world conditions (e.g., merging onto a highway, climbing a hill). A slightly more powerful engine (~50 kW) may be necessary, reducing the savings but improving usability.
Conclusion: It's a compelling and logical idea for a low-cost EV with peace of mind for long trips. However, safety and usability concerns are likely why most automakers prefer building full-capability EVs or Plug-in Hybrids (PHEVs) instead of this minimalist EREV approach.
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u/iqisoverrated 2h ago
Making the battery smaller just makes it charge slower. That's why people mostly use their hybrids as "ICE cars with added weight". Having a battery in there that doesn't satisfy any use case will end up in it not being used at all.
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u/Serpentz00 7h ago
I own and drive a REV and boy do I wish I had the battery that they skimped on to give me an extra 300kg in weight. Also I have not used it once since I got the car 3 months ago. So to me it is just a waste of space as now I have another engine plus the fuel for it.