[Project] Extending EV range by offsetting auxiliary 12v loads using solar

cosmicosmo4

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I have a BEV (totally electric).

I suppose that thos i3 owners do that in order to get better battery life than lead-acid. But I'm not worried about that, the car is fairly new.
I'm just looking to extend the range a bit using solar. I'm keeping the 12v lead-acid (SLA) because I'm trying not to make any permanent modifications, and it won't help extend the range anyways.

Replacing the 12v lead acid battery with LFP increases the range because it decreases the weight of the vehicle.

Adding solar panels, a charge controller, and an additional battery decreases the range because it increases the weight of the vehicle.

If range is the goal, you really should measure the amount by which your range changes for every kg added or removed. You'll have to get enough solar input to overcome this loss. Also aerodynamic loss if you're adding things to the outside of the car.

If playing around is the goal, then continue enjoying yourself.
 

Hedges

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when you don't make cross country road trips the BMW i3 120ah with an REX (range extender) sounds the perfect fit for your. (gets about 220miles of EV Range)

I think that's the one brought to U.S. deliberately crippled to snag California financial incentives.
Usable capacity of gas tank was reduced by software so ICE range < all electric range.
Battery SoC at which engine starts was reduced, leaving marginal charge to help with hills.

I don't want to replace an ICE vehicle having 300 ~ 400 miles range with a car having 140 miles electric + 130 miles gas range. (220 EV a bit better)
On a trip, that would mean only 2 hours driving from full to empty. And see above abysmal performance with "limp home" ICE mode.

Volt seemed like a good fit, given < 40 miles commute. It didn't fit the bill when I suddenly thought I was in the market but would today. There was i3 (I think) with crippled performance. Honda Clarity, the "Volt" from Honda, had issues of functional failure reported by many owners. Maybe fixed by now.

A Tesla with small battery and range extender could be really nice. Or an EV/ICE design with redundancy in the power train, so either system could completely fail and it keeps working. Don't know of any designed for that.
 

eXodus

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I think that's the one brought to U.S. deliberately crippled to snag California financial incentives.
Usable capacity of gas tank was reduced by software so ICE range < all electric range.
Battery SoC at which engine starts was reduced, leaving marginal charge to help with hills.
yes it's crippled by software, but you google a little into "i3 Coding" it's stupid easy reversed to the European specification which is much more capable.

Which makes a very attractive used car for those who know that a phone app can change the capabilities of the car within a few minutes.
For everyone else it's a quirky little car with little use.
 

eXodus

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Or an EV/ICE design with redundancy in the power train, so either system could completely fail and it keeps working. Don't know of any designed for that.
the BMW i8 - front electric Motor - rear internal combustion engine :p It's sports car
 

Bluedog225

Texas
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Why not simply offload the load to a stand-alone solar system. Panel, controller, battery. Do not connect to the existing system. Power the radio, phone charging, etc.
 

curiouscarbon

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For now I’ll be doing the auxiliary battery to power other stuff because direct integration with the rest of the vehicle’s systems is too complex for my taste at this time.

This is for fun and to observe in practice what is possible with current off the shelf components. In my case.

I plan on targeting 1500W AC charging from an aux pack in the boot. Flex panels on roof, charge controller, battery, (HF) inverter in boot. thermal management shall be interesting. lots of supplemental temperature sensors going in there. probably will run a small air tube ~1-2 inch diameter and activate a blower to exchange air with the rest of the vehicle air supply.

Soak energy during the day and deliver it while parked via 1500W AC charging. it will look quite silly but maybe if i go out the rear window rather than the boot for the charge cable it would be less ugly. Either way, the aux battery will probably only be able to be 1000-2000 watt hours which is 2.3 miles of range in the worst case but nearly 6 miles in best case.
 

meetyg

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when you don't make cross country road trips the BMW i3 120ah with an REX (range extender) sounds the perfect fit for your. (gets about 220miles of EV Range)

With the tiny batteries in the i3 - that car would be the ideal candidate for a Solar Roof, when you park outside

what EV are you driving? Why not get a flexible panel with magnets to the roof?
I'm driving a fully electric BEV, an Opel/Vauxhall Corsa-e (probably not sold in the U.S.). It's It's small hatchback.
20210116_225137.jpg

The reason why I don't want panels on the roof (or anywhere else on the car) is because of added drag and therefore loss of efficiency. Also, the panels will need constant cleaning laying flat outside the car. I also don't want them to get stolen, if I mount them with magnets.
Another disadvantage of mounting them on the car rather than inside is that I would have to solve the wiring going into the car.
When everything is inside the car uts alot easier to manage wiring.

If I get really low efficiency overall, I might change my mind. But for now these are my plans.
 

meetyg

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Why not simply offload the load to a stand-alone solar system. Panel, controller, battery. Do not connect to the existing system. Power the radio, phone charging, etc.
In order to power the radio, I would need to disconnect it from the 12v system.
The reason I want to integrate it with the existing 12v is that there are more loads, like lights, A/C fan etc... which take more energy than just the radio and/or phone charging.
 

meetyg

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For now I’ll be doing the auxiliary battery to power other stuff because direct integration with the rest of the vehicle’s systems is too complex for my taste at this time.

This is for fun and to observe in practice what is possible with current off the shelf components. In my case.

I plan on targeting 1500W AC charging from an aux pack in the boot. Flex panels on roof, charge controller, battery, (HF) inverter in boot. thermal management shall be interesting. lots of supplemental temperature sensors going in there. probably will run a small air tube ~1-2 inch diameter and activate a blower to exchange air with the rest of the vehicle air supply.

Soak energy during the day and deliver it while parked via 1500W AC charging. it will look quite silly but maybe if i go out the rear window rather than the boot for the charge cable it would be less ugly. Either way, the aux battery will probably only be able to be 1000-2000 watt hours which is 2.3 miles of range in the worst case but nearly 6 miles in best case.
What EV do you have?
Sounds like alot of weight to be added.
 

meetyg

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Replacing the 12v lead acid battery with LFP increases the range because it decreases the weight of the vehicle.

Adding solar panels, a charge controller, and an additional battery decreases the range because it increases the weight of the vehicle.

If range is the goal, you really should measure the amount by which your range changes for every kg added or removed. You'll have to get enough solar input to overcome this loss. Also aerodynamic loss if you're adding things to the outside of the car.

If playing around is the goal, then continue enjoying yourself.
OK, you've got a point there...
But, from my gross calculations, I will be adding around 7.5kg of weight.
If my calculations are correct, that will be consuming about 0.7Wh per kilometer.
If I multiply that by my 70km daily drive, that's only 50Wh added to energy consumption.
Having that my car's consumption per KM is 155Wh on average, I will still benefit from this setup (as long as I will be able to produce around 200-300Wh a day).

I am not planning to mount anything outside the car, so aerodynamics/drag shouldn't be affected.

But if I see that my total output isn't enough, I have a fallback: Not mounting the panels in the car, but taking along a 100w flexible panel and slapping it on the roof on when the car is parked. The advantages are more power, but the disadvantage is that I would have to figure out a way to wire that panel I to the car (without permanent changes), and making sure it won't get stolen.
I suppose that I could just close the door on the cables, but that would probably harm the cables of the panel and the rubber fittings of the door, in long term.
The other disadvantages are that it won't charge the car while driving, and would be a bit of hassle to take out/put in every time.

Anyways, changing the 12v to LFP may be a good idea to save weight, but I would need an automotive grade LFP for that, which would be fairly costly.
 

curiouscarbon

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Sounds like alot of weight to be added.
Indeed. But everything in life comes at a cost :)

for a 2kWh LFP+2000W HF inverter and charger, the mass maybe equivalent to having a passenger? I’m ok with that personally. When I drive with a passenger the change in momentum is usually noticeable.

Such a system would be for camping, so the added weight at this scale seems insignificant given that a full fridge of water based refreshments might outweigh the auxiliary battery. Probably pack solar panels to set up on ground.

Full disclosure: haven’t built anything yet.

Using an HF inverter ought to cut down on weight. Don’t see the need for heavy copper coils in this situation.

I do a lot of custom thermal regulation tinkering so having it in a small enclosed space feels tractable.
 

curiouscarbon

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OK, you've got a point there...
But, from my gross calculations, I will be adding around 7.5kg of weight.
If my calculations are correct, that will be consuming about 0.7Wh per kilometer.
If I multiply that by my 70km daily drive, that's only 50Wh added to energy consumption.
Having that my car's consumption per KM is 155Wh on average, I will still benefit from this setup (as long as I will be able to produce around 200-300Wh a day).

I am not planning to mount anything outside the car, so aerodynamics/drag shouldn't be affected.

But if I see that my total output isn't enough, I have a fallback: Not mounting the panels in the car, but taking along a 100w flexible panel and slapping it on the roof on when the car is parked. The advantages are more power, but the disadvantage is that I would have to figure out a way to wire that panel I to the car (without permanent changes), and making sure it won't get stolen.
I suppose that I could just close the door on the cables, but that would probably harm the cables of the panel and the rubber fittings of the door, in long term.
The other disadvantages are that it won't charge the car while driving, and would be a bit of hassle to take out/put in every time.

Anyways, changing the 12v to LFP may be a good idea to save weight, but I would need an automotive grade LFP for that, which would be fairly costly.
I’ve considered flat wires before. Have considered running a few parallel insulated flat cables through a door or back hatch seam and maybe put some silicone down to keep it flush.

like this

1635025468843.jpeg
 

meetyg

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After all of the discussion here about swapping the 12v LA to LFP, you guys have convinced me :)
The weight reduction is nice, and having less self-discharge should also be beneficial to saving some range.

But, I'm gonna save it as a future improvement. My 12v LA is in good condition, as the car is pretty new.
Maybe in a year or so, I will swap it out.
Hopefully by then prices of LFP will also be cheaper.
 

curiouscarbon

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Cool, do you have link for this?
can’t find the original one but this one is very similar https://www.amazon.com/FRANKEVER-Adhesive-Conductor-Electrical-Connectors/dp/B07K84VBZ3/

terms used to find: flat wire

adhesive being too weak and routing seem to be two of the challenges i saw pop up in reviews for this type of tape. personally i would maybe just try to do straight run as much as possible and then solder onto the endpoints to convert back to normal wire. still haven’t experimented with the white tape for electrical entry yet. also to be careful to avoid electrically conducting to chassis

good luck!
 

meetyg

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can’t find the original one but this one is very similar https://www.amazon.com/FRANKEVER-Adhesive-Conductor-Electrical-Connectors/dp/B07K84VBZ3/

terms used to find: flat wire

adhesive being too weak and routing seem to be two of the challenges i saw pop up in reviews for this type of tape. personally i would maybe just try to do straight run as much as possible and then solder onto the endpoints to convert back to normal wire. still haven’t experimented with the white tape for electrical entry yet. also to be careful to avoid electrically conducting to chassis

good luck!
Thanks!
I found it on Aliexpress too.
Those darn connectors are expensive though :confused:
But I ordered some 5 meters to play with.
It could also help tidy up the connections inside the car for some points.
 

eXodus

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can’t find the original one but this one is very similar https://www.amazon.com/FRANKEVER-Adhesive-Conductor-Electrical-Connectors/dp/B07K84VBZ3/

terms used to find: flat wire

adhesive being too weak and routing seem to be two of the challenges i saw pop up in reviews for this type of tape. personally i would maybe just try to do straight run as much as possible and then solder onto the endpoints to convert back to normal wire. still haven’t experimented with the white tape for electrical entry yet. also to be careful to avoid electrically conducting to chassis

good luck!
that's awesome stuff - thanks.

I wanted to get some additional speaker wired and need to get to the door - underneath the door seal - and I didn't wanted to drill a hole in the carbon Fiber i3 frame.
 

curiouscarbon

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Thanks!
I found it on Aliexpress too.
Those darn connectors are expensive though :confused:
But I ordered some 5 meters to play with.
It could also help tidy up the connections inside the car for some points.
the connectors seem to be the easiest way to terminate the wire. maybe most expensive

some reviews say they are bulky and look bad and sometimes design flaw can result in high resistance connection.

if you are comfortable with a soldering iron, maybe an option to consider. could crimp a fork style connector at the end of normal wire and the solder that into the copper tape run. i like to use gorilla hot melt glue to seal in connections like that. fragile and stuff. just some random thoughts good luck with your hacking!

1635109060184.jpeg
like this thing on end of normal cable and then tin it with solder and then solder it to the copper sort of dealie
 

sunday

New Member
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Oct 22, 2021
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7
After all of the discussion here about swapping the 12v LA to LFP, you guys have convinced me :)
The weight reduction is nice, and having less self-discharge should also be beneficial to saving some range.

But, I'm gonna save it as a future improvement. My 12v LA is in good condition, as the car is pretty new.
Maybe in a year or so, I will swap it out.
Hopefully by then prices of LFP will also be cheaper.
What I would do in the meantime is measure the current draw on your current battery. Maybe do some digging/reading in to what your actual electric car requires. I know at least some Tesla cars have lead acid 12v batteries in them because when developed they had some 12v requirements, legal and regulatory. There are some advantages in lower temps with lead acid as well, but the weight is something worth getting rid of.

Car batteries were always measured in CCA, and to get that same rating in lifepo4 you'd need a huge battery. But your car may pull nothing like that. It doesn't have the same requirements as internal combustion engine. My guess is most of the expensive lifepo4 batteries for automotive use are made for the requirements of ICE cars rather than electric cars.

4 headway 38120 cells make 12v and are only 8ah, but they can do 200a. Would any electric cars need anything close to that?
 

meetyg

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What I would do in the meantime is measure the current draw on your current battery. Maybe do some digging/reading in to what your actual electric car requires. I know at least some Tesla cars have lead acid 12v batteries in them because when developed they had some 12v requirements, legal and regulatory. There are some advantages in lower temps with lead acid as well, but the weight is something worth getting rid of.

Car batteries were always measured in CCA, and to get that same rating in lifepo4 you'd need a huge battery. But your car may pull nothing like that. It doesn't have the same requirements as internal combustion engine. My guess is most of the expensive lifepo4 batteries for automotive use are made for the requirements of ICE cars rather than electric cars.

4 headway 38120 cells make 12v and are only 8ah, but they can do 200a. Would any electric cars need anything close to that?
I did do some testing not long ago.
I was able to see up to 20A draw, but I suppose that the DC-DC converter was supplying it, not the battery.

Unfortunately my clamp meter doesn't have an "inrush" or peak function, so I couldn't check what the peak draw was on the battery when the car was "started" (only checked after the car was on). But I suppose that the draw should be fairly low, as when starting and EV, it only has to supply power to the HV battery contactors/relays.

So I think you are correct in that we don't need high CCA batteries.
My question is, how will Lifepo4s handle heat under the bonnet/hood of the car in the hot summer.
Fortunately, EVs don't produce much heat under the hood, but still it can get pretty hot when the car is parked under the sun.

Are headways more resilient to hot weather than the prismatic cells?

Maybe if I will be able to find a good price on some headways, I will build my own Lifepo4 🙂
That way I would be more confident putting something in my vehicle (rather than some unknown quality product).

You got me thinking now!
 
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