Want to charge a little with Solar panels

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DuncanCunningham

Well-known member
Joined
Mar 26, 2015
Messages
528
Location
Bountiful, UT
During my solar install we had a number of issues and delays and I helped out a lot to resolve these, including digging up the 150ft trench twice from the array to my house. Anyway, long story short. I have 2 extra panels that were given to me as a "thank you".

They are Canadian Solar (CS6U-325)

Link: https://www.canadiansolar.com/fileadmin/user_upload/downloads/datasheets/v5.5/Canadian_Solar-Datasheet-MaxPower-CS6U-M-v5.5en.pdf

when I setup the array we used AP systems for the Micro invertors, they change the voltage fromthe panels DC to 240v AC to the house. Each one can host two panels but they have anti-islanding for safety if the power line goes down to safe guard the line workers so it's not for off grid applications without some other equipment.

I'd like to stage the two panels on a little trailer, connect to an invertor of some sort and use a EV connection station, it can do 120v or 240v (it's the Nissan brick that each car gets and it's been upgraded. It can go to 16Amps and as low as 6 amps I think.

Can I do this?

the panels I have on my array pull in 290 Watts each at peak. so peak is about 580Watts from both panels.

Any ideas how I could connect all this up to pull in some free sunlight during the day while I'm at work?


Yes, I could have put the panels on my array but that would require telling the authorities and that would mean a change to my system and i'd get put a on a tiered system of power.. right now I get KWhs in parity to what I pull out. so equal in i get credited back.
 
You could use batteries to store and release the 6 amps needed, meaning you could charge roughly 2/3 of the time the panels spend in full sun, with about a 1 hour lag before starting, and another 2 hours after to let the batteries recover. Better yet, charge the car one day, and the batteries alone one day...
 
yeah if you used the panels to charge some deep cycle batteries and then suck the charge from those into the car when you park (via an inverter), that would be viable. not sure if it would be worthwhile, but it would accomplish what you're trying to do. continuously the cells won't charge the car on their own. I would just parallel them into the system you have.
 
I would suggest leaving the panels in a sunny unobstructed spot to charge the batteries, then when they are almost full charge up the Leaf. Hauling the trailer around will likely consume more power than than the trailer will produce and you likely won't have ideal angles to the sun for the panels. You will need at least a 2000w rated inverter and at least 250 ah of battery if you want to charge for an hour. While 100 ah of battery at 12v would get you the 1200wh you have inverter losses as well as voltage dip. 100 ah of battery will get you about 30 minutes of charge time.
 
BrockWI said:
I would suggest leaving the panels in a sunny unobstructed spot to charge the batteries, then when they are almost full charge up the Leaf. Hauling the trailer around will likely consume more power than than the trailer will produce and you likely won't have ideal angles to the sun for the panels.

I don't recall saying anything about dragging a trailer around behind my car continuously, that would be a little crazy, even for me. I was going to put in on a trailer as a way to get it from home to a location. I have only one location in mind though, my work. The parking spot I have is perfect to collect southern sun angles.

BrockWI said:
You will need at least a 2000w rated inverter and at least 250 ah of battery if you want to charge for an hour. While 100 ah of battery at 12v would get you the 1200wh you have inverter losses as well as voltage dip. 100 ah of battery will get you about 30 minutes of charge time.

now, this is what I'm looking for.

So it looks like I should setup the panels to charge batteries and then use an inverter when they are full to pull DC from the batteries to AC to charge the car using the lowest setting, which looks like it's 6amps. Ok. a bit of free juice maybe once or twice a week, depending on the battery pack I can put together.

My daily commute is about 22 miles round trip so I don't have to charge at home every night. I do get over 4 miles per kWh.

I'm not trying to make all of my charge to come from the two panels, just when they are sat around doing nothing right now and wanted to know if they could be used in such a manner. Thank you for your input.

One thing I have read in previous posts that comes to mind. Is there an issue with the safety ground check during the communication between the car and the station before it starts up charging?
 
Take a look at this thread, I know it is discussion about charging from a genset, but charging from an inverter has similar issues.

http://www.mynissanleaf.com/viewtopic.php?f=26&t=23899

and this one, its longer with a lot of good info

http://www.mynissanleaf.com/viewtopic.php?f=26&t=4047
 
If using lead acid battery you need to deplete them in the morning and then let them charge the rest of the afternoon.
If you deplete them late in the day and leave them overnight they will sulfate a bit each day and lose capacity.
Even a good deep cycle like a golf car battery should only be depleted 50% on a regular basis or you shorten the life significantly.
Or you need $$$ lithium $$$ for maximum performance.

This is why I recommend two more panels. Panels are only about $150 each. This way the battery is just a buffer between the solar and inverter. You would never deplete the battery and would only need one battery instead of six or more. Then you still need an adjustable EVSE to get down to 6 amps.
 
If using lead acid battery you need to deplete them in the morning and then let them charge the rest of the afternoon.
If you deplete them late in the day and leave them overnight they will sulfate a bit each day and lose capacity.
Even a good deep cycle like a golf car battery should only be depleted 50% on a regular basis or you shorten the life significantly.

Yes, that was why I suggested letting the panels charge the panels for at least two hours after charging the car. That isn't ideal either though. I like the idea of charging the batteries in the AM from the previous day's charge, and then charging the batteries for the rest of the day.
 
I think you'd want to feed the panels into a DC-DC converter. This is an example of a 1000 watt DC-DC with 48v output, 19-72v input.

https://www.ebay.com/itm/POWERNEX-MEAN-WELL-NEW-SD-1000L-48-48V-21A-1000W-Single-output-DC-DC-Converter/252615070064?epid=662498684&hash=item3ad1081170:g:jrMAAOSwx2dYGDZv

An OpenEVSE could work, dialed-down to 6A @120v = 720 watts current draw. An inverter capable of putting-out 1kw would be able to produce that (but a 1500w inverter would be better). The inverter would have some inefficiency, so you'd want to feed it with 10% extra watts, or 792 watts (= 66 amps).

For batteries, assuming you were using deep-cycle batteries, like this, for $359:
https://theinverterstore.com/product/12-volt-200-amps-agm-deep-cycle-maintenance-free-battery/?gclid=EAIaIQobChMI48TSm5Xe2AIV2rrACh0NqwdwEAQYAiABEgJL1vD_BwE

...that battery has a 200 amp-hour capacity at 12v (when discharged over 20 hours). A 12-hour discharge rate is about as fast as you want to go, or 200 amp-hours/12 hours = 16.7 amps per battery. To add-up to 66 amps of output, you'd need 3.96 of those batteries (so... four batteries, which would work well with a 48v DC-DC converter output).

Assuming that you got four 200-amp-hour batteries, and wanted to limit discharge depth to 30% (nice), that's 60 amp-hours of discharge capacity per battery, at 12v = 720 watt-hours, x 4 batteries = 2880 watt-hrs total stored energy / 792 watts to feed the inverter, = maximum 3 hrs 38 minutes of discharging capacity (to stay within 30% discharge depth).

Looking at the panels, if you think you can capture 1.6 kw-hrs per day of power from the solar panels, and lose 10% in the DC-DC converter, plus 15% storing in the batteries (= 1224 watt-hours per day gain, on average), then you could probably charge your Leaf, at 6A 120v, for about 1 hour 32 minutes per day, on average, based on the weather; and could store up to about three days worth of sunshine (or about 18% SOC gain on the Leaf) in those four batteries.

Using 8 batteries with the 6A EVSE would let you store about 6 days of sunshine / 36% SOC, and would limit you to a 24-hour discharge rate, which is nicer if you want the batteries to last. You'd need to charge them as two 48v strings.

Caveat: I don't actually know what I'm talking about. And electricity isn't safe.
 
can these cars charge at an even LOWER rate? I mean the trickle charger is 1.1kw can you charge even lower?

going pure solar even if you don't get much would be ideal since there is nothing to wear out (namely expensive short lifespan batteries) your never going to recoup the cost of those batteries. ever.

but pure solar with solar you already have and a $100 used trailer is essentially free power even if its just a sip.
 
so. does that mean you can NOT charge lower than 6A?

a designed range is not necessarily a limit. I am curious. WILL the leaf charge at say 3 amps?
 
6 amps at 120 volts is the lowest I can set any EVSE I have and the car pulls 750w at that point. I don't know how you could give it less, I believe the pumps and converter consume about 350 watts? So then you are only putting 350 watts in the battery. At that rate it would take 60+ hours to charge :) But if it is solar power sure.
 
If I were trying this, I'd use an OpenEVSE and write custom software to monitor the Solar inverter and adjust the output of the EVSE accordingly. I'd use a battery just to provide the seed voltage to keep the Solar inverter online and to absorb/provide current while the car changes it's current draw. Just shut the whole thing down when Solar output is too low rather than add lots of batteries or draw the lead acid battery down.
 
davewill said:
If I were trying this, I'd use an OpenEVSE and write custom software to monitor the Solar inverter and adjust the output of the EVSE accordingly. I'd use a battery just to provide the seed voltage to keep the Solar inverter online and to absorb/provide current while the car changes it's current draw. Just shut the whole thing down when Solar output is too low rather than add lots of batteries or draw the lead acid battery down.
~

I've actually done similar to this and it works with my OpenEVSE using arduino/IDE for control. IMHO, considering all losses, my 4000 nominal watt system is marginal as much of the solar day it wants to operate at the 6 amp minimum with a 220 vac inverter (clouds, early/late daytime). The system is basically off-grid with a small battery bank to allow for the solar fluctuations (with intent to keep battery SOC in reasonable range).
 
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