DIY Electric Car Forums banner

1 - 17 of 17 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
I have a 2018 Nissan Leaf, and a 300 W solar panel. Especially now due to COVID, it sits for days on end without being driven. That single panel could easily put 1-2 kWh into the pack each day, but it's not big enough on its own to power even the 120 V level 1 charge (which needs like 1500 W).

Is it possible to fake out a CHAdeMO charger to charge the pack using DC at very low power?
 

·
Registered
Joined
·
742 Posts
The usual approach is to slow charge / keep topped up, a larger "mothership" bank

which could also be used for other things

And then charge the EV off that.

But I would have thought all the Direct DC protocol specs would allow the vehicle tospecify whatever slower rate they like?
 

·
Registered
Joined
·
4,796 Posts
The usual approach is to slow charge / keep topped up, a larger "mothership" bank

which could also be used for other things

And then charge the EV off that.
That makes sense to decouple the energy source from the EV to be charged, but in this case it seems likely that with only 1-2 kWh available each day it would be entirely consumed by losses in the charger feeding the stationary ("mothership") battery, losses in the charge/discharge cycle of that battery, losses in the inverter powered by the stationary battery, and losses in either the EV's onboard charger (if AC charging) or the external DC charger (if CHAdeMO or otherwise DC charging). Certainly with so little energy per day, no other significant things could be powered from this system.

It would make more sense to me to power something else of lower power demand with the panel to make use of its output.
 

·
Registered
Joined
·
4,796 Posts
But I would have thought all the Direct DC protocol specs would allow the vehicle tospecify whatever slower rate they like?
While the standards might allow that, there is no motivation for charger manufacturers to support trickle rates, and they might reasonably set a lower limit at which the charger (which is sized for tens of kilowatts) is still reasonably efficient.
 

·
Registered
Joined
·
742 Posts
I thought the OP premise was simply keeping a basically unused car topped up and ready to go while off grid.

Presumably public chargers available to support long trips.

Obviously such a small solar setup would just be a playtoy compared to modern needs across the board. Not that there's anything wrong with familiarizing yourself with the tech on a small scale.

And if mains is available at home, hard to justify economically unless taking advantage of subsidies.
 

·
Registered
Joined
·
252 Posts
Is it possible to fake out a CHAdeMO charger to charge the pack using DC at very low power?
That would be quite a bit of work, and most likely it will still not accept something that is only 300 W.

Your best bet is to install a few more solar panels (prices are down to 50 cents a W). If you install 5 or 6 300 W solar panels, you could probably supply the 1.3 kW required for Level 1 for a few hours a day. Currently it takes your single 300W panel about 20 sunny days to fully charge the leaf. Basically your car is unavailable most days.

Alternately, you can charge about 1 kWh of lithium ion cells, and then dump that to the Leaf through the L1 port using an inverter.
 

·
Registered
Joined
·
374 Posts
The only way to charge a battery is with a higher voltage. You solar panel won't supply enough voltage to charge an EV size battery even DC to DC unless you can boost the voltage with electronics.
 

·
Registered
Joined
·
742 Posts
Boost controllers are a thing.

But yes getting up to panel voltages higher than the mothership bank, then going downhill again to the smaller EV pack, really is more efficient
 

·
Registered
Joined
·
68 Posts
From what I've read, Lithium batteries don't like trickle charging. My Calb 100ah LiFePo4 cells are recommended to be charged at 1/3c or 33A on their data sheet. Lead acid likes trickle...
 

·
Registered
Joined
·
374 Posts
From what I've read, Lithium batteries don't like trickle charging. My Calb 100ah LiFePo4 cells are recommended to be charged at 1/3c or 33A on their data sheet. Lead acid likes trickle...
You can trickle charge any battery. What Lithium's don't like is charging after full. A traditional trickle charger for a lead battery hold the battery at 14 volts or so and constantly trickles current to keep the voltage up. You can't do that with Lithium Ion. once it is charged the charger must turn off. Don't get your terms confused.
 

·
Registered
Joined
·
252 Posts
From what I've read, Lithium batteries don't like trickle charging. My Calb 100ah LiFePo4 cells are recommended to be charged at 1/3c or 33A on their data sheet. Lead acid likes trickle...
As Pdove has said, Lithiums have no problem with trickle charging, as long as they have capacity to accept the charge (unlike lead acid or NiMH who when unable to accept the charge will just convert it to heat). In fact the slower you charge Lithium, the better it is and it increases the cycle life. But once the cell gets to 4.2V, you may not raise the voltage above 4.2 and should disconnect the trickle charging, or you will damage the cell. All Lithium chargers will not go above 4.2V and will disconnect when it is reached or when it is timed out or when the current drops below a minimum in CV mode.
 

·
Registered
Joined
·
374 Posts
As Pdove has said, Lithiums have no problem with trickle charging, as long as they have capacity to accept the charge (unlike lead acid or NiMH who when unable to accept the charge will just convert it to heat). In fact the slower you charge Lithium, the better it is and it increases the cycle life. But once the cell gets to 4.2V, you may not raise the voltage above 4.2 and should disconnect the trickle charging, or you will damage the cell. All Lithium chargers will not go above 4.2V and will disconnect when it is reached or when it is timed out or when the current drops below a minimum in CV mode.
Depending on the chemistry! LiFePO4 cells can’t go to 4.2v most say 3.65v. Just follow the manufacturer specification
 

·
Registered
Joined
·
161 Posts
Depending on the chemistry! LiFePO4 cells can’t go to 4.2v most say 3.65v. Just follow the manufacturer specification
Absolutely. OP has a leaf, so the recommendation assumed his vehicle.
Also the leaf might only charge to 4.1 or 4.15, not sure what the numbers are like these days.
 

·
Registered
Joined
·
296 Posts
No free lunch.

You can buy 5 more panels.- I've seen them for $0.15/W if you want to be Mr Cheap with grid powering your always-plugged-in Level 1.
 

·
Registered
Joined
·
742 Posts
From what I've read, Lithium batteries don't like trickle charging. My Calb 100ah LiFePo4 cells are recommended to be charged at 1/3c or 33A on their data sheet. Lead acid likes trickle...
What LI doesn't like is to be Floated, after it has been fully recharged, as Lead requires. In fact you should keep LI at a low SoC unless you will soon need to start cycling, just sitting at a high SoC shortens lifespan.

Very old-school garage chargers used to not only have no Float charge they didn't even have a way to do charge termination, like a dumb PSU

those were also called trickle chargers since they were at a low amp rate.

No battery chemistry should be subjected to such abuse :cool:

So long as your charger has a reasonable algorithm for properly stopping once the bank is Full, ideally user-adjustable,

then charging LI at a lower rate is better for longevity than fast charging for most chemistries,

including both LFP and those more commonly used for EVs, at least until you get down to 0.2-0.3C. The only downside is the cycle obviously takes longer!

LTO is an exception, apparently loves crazy high rates, can refill from empty in 10min. Just low density, no good for consumer EVs
 

·
Registered
Joined
·
742 Posts
Depending on the chemistry! LiFePO4 cells can’t go to 4.2v most say 3.65v. Just follow the manufacturer specification
No the mfg specs are theoretical maximums, for occasional capacity benchmarking, stress testing, etc

not to be used for daily cycling, if you want good longevity.

Best to stay between 3.45 and 3.50Vpc, depending on the C-rate, and Bulk stake / CC-only is fine, no need to hold CV / Absorb stage
 
1 - 17 of 17 Posts
Top