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Solar panels on an EV roof

Posted: Sun, 23 Dec 2018, 13:17
by Hanzieo
Moderator note: this series of posts was split off from the Aftermarket iMiEV battery upgrade project thread, at the request of a reader.

End moderator note.
=================

Hello,

I have a minicab on the Central coast and will also be very keen on a battery extended. I am planning to place 3-4 solar pannels on the roof and top up the battery. 1.4kw will deliver 5kwh per day in good sun in summer and about 3kwh in winter

It's only an idea in my head at the moment, currently I'm stuck with the 140vdc out of the pannels to 316v of the battery. One of my ideas is to have a second battery of say 5kwh @48v getting charged from solar all day and then dump it in the traction battery via a 10A 240v inverter using the cars standard charger. I think this will only work when the car is parked. Any thoughts?

Regardless of the solar I would still be keen on buying cells if there is a group buy

Re: Solar panels on an EV roof

Posted: Sun, 23 Dec 2018, 15:02
by jonescg
Hanzieo wrote:
Sun, 23 Dec 2018, 13:17
Hello,

I have a minicab on the Central coast and will also be very keen on a battery extended. I am planning to place 3-4 solar pannels on the roof and top up the battery. 1.4kw will deliver 5kwh per day in good sun in summer and about 3kwh in winter

It's only an idea in my head at the moment, currently I'm stuck with the 140vdc out of the pannels to 316v of the battery. One of my ideas is to have a second battery of say 5kwh @48v getting charged from solar all day and then dump it in the traction battery via a 10A 240v inverter using the cars standard charger. I think this will only work when the car is parked. Any thoughts?

Regardless of the solar I would still be keen on buying cells if there is a group buy
Solar will be a lot of hassle for mot much gain. If we can get the 100 Ah cells to fit inside the iMiEV enclosure we will effectively double the range, so solar panels on the roof would be better on top of the garage. I hope to get an empty Leaf and iMiEV battery box (complete with BMS) next month so we can start mapping out some replacement cells.

Re: Solar panels on an EV roof

Posted: Sun, 23 Dec 2018, 15:47
by Peter C in Canberra
Hanzieo wrote:
Sun, 23 Dec 2018, 13:17
...I am planning to place 3-4 solar pannels on the roof...
Depending on how you mount them, extra wind resistance might off-set a large part of any benefit.

Re: Solar panels on an EV roof

Posted: Mon, 24 Dec 2018, 05:08
by Hanzieo
Thanks guys ,
The van will get a roof rack anyway for ladders so pannels won't add much extra resistance. I know there prob won't be much financial gain and that's not my motivation. It's about the idealism of a solar powered car that can drive around the country without adding fuel if one has enough time. There isn't many other EV's where this is even possible and this car is probably the best candidate out there. Big flat roof, small motor ect.

If is sortof educational and fits well with my role at the Central coast makerspace and my business as a solar installer.

Anyway I am keen to join the group buy for $6K or the option that just get the factory range back again. That's is the MOQ doesn't have to be identical cells and we can get a mismatch.

Re: Solar panels on an EV roof

Posted: Mon, 24 Dec 2018, 05:29
by tonyw
@Hanzieo
currently I'm stuck with the 140vdc out of the pannels to 316v of the battery
There is also the possibility of using micro-inverters to deliver 240V AC directly from each panel. Here I have 16 panels with µ-inverters. I charge the MiEV during the afternoon once the Powerwall is full at about lunchtime. Even with less than full conversion efficiency, it's free - 105% of nothing is nothing!

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 07:43
by T1 Terry
What are the dimensions of the roof area you have available or could get away with if there was a little bit of overhang each side? How many panels 1060mm x 540mm could you fit on the roof? It is possible to boost the panel output to charge the battery pack direct but the real issue will be weight, so you would need to go with light weight semi flexible panels like these
1900w semi flexible solar completed job small.jpg
1900w semi flexible solar completed job small.jpg (80.65 KiB) Viewed 1655 times
To do the job without a voltage booster you would need 19 panel the same as on this 5th wheeler roof, but I doubt you have that much area. The ideal way to build it would be as a false roof above where the ladders etc would be loaded on the roof, it could be enclosed on the sides and front to improve aerodynamics and even a lock up rear door for added security.

T1 Terry

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 08:47
by Hanzieo
Terry,
The flat box above the ladders is what I am planning. There is not enough roof space to get to the voltage required. I think I can fit 4 x 360w LG pannels on top of a roof rack.

I will have to boost it. The one way I see is a MPPT converter/dc-dc converter to Up the voltage/Li charger. This will need to be a custom build board and prob high losses.

Or dump the solar into a secondary battery via a MPPT charger. Then run a 2.4kw inverter to 10A 240v and use the standard 10a charger to dump the content of the secondary battery into the traction battery when parked.

Not super efficient but open up lots of choices for the voltage of the secondary battery. I'm thinking 5-6kwh of Li-ion 18650's @48v.

This is all stating to take up a lot of room.

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 12:15
by T1 Terry
I'd look at a boost unit to lift the voltage up to the required charging voltage for the on board battery as you already have that and it is the item you want to recharge in the long run anyway.
The LG 360w panels are good but they are heavy. A 2.5 times voltage booster would give you roughly enough voltage to recharge the traction battery and use a simple solar output cut when/if a cell reaches the max safe voltage. You are only looking at harvesting 6kWh at best so you need to minimise the losses.

T1 Terry

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 13:19
by Hanzieo
Terry

Very interested. What is a voltage booster? Can you give a example of one in the 1.5kw range?

The Vmp of the 4 LG's will be 144v and the current just under 10A.

Re: Aftermarket iMiEV battery upgrade project

Posted: Tue, 08 Jan 2019, 13:27
by T1 Terry
I think we best ask the admin team to split this off into a separate thread in the lounge area or such like so we don't drag Chris's thread way off topic

T1 Terry

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 14:01
by jonescg
@T1 Terry - I don't think I can move threads, but hopefully Dave, Mike or Rob can.

Re: Aftermarket iMiEV battery upgrade project

Posted: Tue, 08 Jan 2019, 14:28
by T1 Terry
I could give you lessons, but better to not know so you don't get dragged into having to do it :lol: phpBB is certainly easier to work with than Nabble when it comes to spitting up threads to new topics, but I avoid getting any deeper than that so I don't stuff things up altogether

T1 Terry

Re: Solar panels on an EV roof

Posted: Tue, 08 Jan 2019, 19:58
by coulomb
Posts moved as requested, @T1 Terry. I hope I got the right ones.

Edit: @chrisjones, it's a moderation function, so you can. You just click on the "MCP" link with the gavel icon, at the top of the page. Then choose the "Split topic" tab on the right. It's fairly self-explanatory from there. But there are a lot of details, like changing the subject of each moved post manually (surely there has to be a way to do that more efficiently).

Re: Solar panels on an EV roof

Posted: Wed, 09 Jan 2019, 04:25
by nuggetgalore
T1 Terry wrote:
Tue, 08 Jan 2019, 12:15
I'd look at a boost unit to lift the voltage up to the required charging voltage for the on board battery as you already have that and it is the item you want to recharge in the long run anyway.
The LG 360w panels are good but they are heavy. A 2.5 times voltage booster would give you roughly enough voltage to recharge the traction battery and use a simple solar output cut when/if a cell reaches the max safe voltage. You are only looking at harvesting 6kWh at best so you need to minimise the losses.

T1 Terry
Interesting new (split off) thread.
If you have a DC volt supply to charge how are you going to access the the traction pack?
IMiEV traction pack balances at 361.2 V (at least that is what canion and /or EVBatmon tells me).
Plugging into the fast charger port would (I guess) need the proper handshake to close the relay on the traction pack.
I would love to be able to charge directly from solar panels that have less power than the 240 V on board charger needs (via a big enough inverter).

Re: Solar panels on an EV roof

Posted: Wed, 09 Jan 2019, 04:32
by mark_hetho
You can tap into the fast charge relay and trigger it to close manually, which closes the fast charge contactor's and gives a direct connection to the pack from the chademo port. It might confuse the state of charge calculation if the EV ECU isn't active and monitoring current flows though. But I can't see a way to get around needing to boost the voltage to the 360V charging range, even if it didn't balance off solar.

Re: Solar panels on an EV roof

Posted: Wed, 09 Jan 2019, 04:53
by nuggetgalore
mark_hetho wrote:
Wed, 09 Jan 2019, 04:32
You can tap into the fast charge relay and trigger it to close manually, which closes the fast charge contactor's and gives a direct connection to the pack from the chademo port. It might confuse the state of charge calculation if the EV ECU isn't active and monitoring current flows though. But I can't see a way to get around needing to boost the voltage to the 360V charging range, even if it didn't balance off solar.
Thanks for that.
Yes of course the supply needs to be above the pack voltage and some serious thought put into not
overcharge the cells.
Where do you think would be a relatively easy ( and safe ,without interfering with the handshake cicuits) spot to access the fast charge relay?

Re: Solar panels on an EV roof

Posted: Wed, 09 Jan 2019, 06:19
by mark_hetho
On a minicab I'm not sure. On the hatchback there is a relay under the back seat, which fires the quick charge contactor when the coil is activated. The circuit needs to be completed via an earth pin in the chademo circuit. However, this won't trigger the chedemo handshake to get the EV ECU into "ready".

Image

You can also apply 12v into the correct pins on the side of the battery pack (but will need to remove underbody covers to get to that connector)

The circuit diagrams at http://mmc-manuals.ru/manuals/i-miev/on ... 700ENG.HTM show how it goes together.

I'm also trying to find a thread where someone added a second pack to their imiev. That certainly tapped into what you need to.

Re: Solar panels on an EV roof

Posted: Wed, 09 Jan 2019, 11:14
by T1 Terry
That's looks to be an easy way to control direct DC charging, simply open the relay if a cell goes over 3.6v.
As far as the voltage boosting circuit, here is basic tutorial on how the set up works http://www.electronoobs.com/eng_circuitos_tut10_1.php Switching 144vdc @ 10 amps could even use one of the basic circuits to drive a Crydom DC400D20 solid state relay (specs sheethttp://www.crydom.com/en/products/catalog/3rd- ... 20_200.pdf ) and one of these diodes in the output https://au.rs-online.com/web/c/semicond ... 4294874820.
I'm sure the brains trust here could come up with something not quite so "agricultural" that could have all sorts of good stuff in it.

T1 Terry