Solar Trickle Charger Setup (with Black Friday deals)

[hemiarch]

You can have multiple charging windows ...
Settlable SOC on the battery would be great, even better if time limited so it doesn't stay off because it's one percent under the threshold.

Now…if I could only schedule for it to FSD its way to the free supercharger, plug in and FSD its way back to the house, I’d be all set.

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[mongo]

Sweet! Is that new? I was looking for something like this earlier this year (my TOU has two windows) and became convinced it was not possible.

I don't think it's new. Haven't tested the behavior, but per the manual it should work. Key is setting start and end times. Otherwise, it doesn't fully respect them.

 

[hemiarch]

I don't think it's new. Haven't tested the behavior, but per the manual it should work. Key is setting start and end times. Otherwise, it doesn't fully respect them.

Our trucks have a bit of a problem with authority it seems. Schedules, speed limits etc.
Maybe that’s why I get along so well with them.

 

[mongo]

Our trucks have a bit of a problem with authority it seems. Schedules, speed limits etc.
Maybe that’s why I get along so well with them.

It's the spirit of the thing
You say you want 80% and you say you want it by 7am
Well, it's 6am and you just plugged in at 50%...
I could stop at 7, but maybe you would rather I kept charging until you leave?

 

[HaulingAss]

Yah, and the F3800 has no such instructions nor warnings. (At least in the downloadable manual nor FAQ).
It has been done: https://diysolarforum.com/threads/will-the-anker-solix-f3800-operate-laying-on-its-back.84419/

We already knew the F3800 didn't have any such warnings in the Owner's Manual, probably because they didn't try to cover every possible way the device could be used. I bet there's no warning against stacking them 8 units high or using one in the shower either for your corded beard trimmer either.

I was simply pointing out that the fact that it can be transported horizontally does not mean it's a good idea to use it horizontally. I'm sure it would work, the question is whether it would cause some components to get hotter than they should, and hotter than the components got during manufacture stress-testing. EV charging is not exactly a low-impact use case. The best-case failure could be a bricked unit, worst case is it catches itself on fire (and whatever else it burns down along with it).

I wouldn't do it, even if it works. Because it likely hasn't been tested in horizontal operation and I wouldn't want to be the person doing that testing.

 

[HaulingAss]

I ran a couple experiments the last two days. Charged overnight at 240V/10A and again at 240V/5A. Compared those to a prior 20A charge. Mongo is (surprise) right - doing the math it comes to about 500-700W power being wasted just to charge. So 1300W in will be only 50% efficient.

I tried to break down the losses to static and IR but ended up with a resistance of -10 (yeah negative 10) Ohms resistance when I fit the data. So wire loss is insignificant and the increased efficiency at higher current is not just the reduced impact of a static load. It appears the DC converter is tuned for higher current (truck wastes not just less energy for the same charge but less power at 5kW rate than at 1.4kW)

Avg A

Avg V

Avg P

Used kWh

Added kWh

Time

%

hours

Avg P In

Avg P add

P waste

linear loss (R=-10)

static loss

19.9​

242.2​

4819.8​

27.8​

24.8​

5:44​

89%​

5.7​

4848.8​

4329.1​

519.8​

-199.0​

718.8​

9.9​

245.8​

2443.3​

32.3​

23.9​

13:09​

74%​

13.2​

2453.2​

1815.2​

638.0​

-99.4​

737.4​

5.7​

245.8​

1396.1​

15.4​

8.2​

10:57​

53%​

11.0​

1409.1​

746.1​

663.0​

-56.8​

719.8​

There are three solid state charging modules in the Cybertruck's on-board charger. Each module can add up to 16 amps, combining for the full 48-amp capacity.

Such modules typically reach peak charging efficiency at around 90% of their design capacity (and their lowest efficiency when very lightly loaded). Assuming charge levels under 16 amps (where only one charge module would be powered), peak charging efficiency would likely occur at around 14-15 amps. 5 amps would be very inefficient.

Likewise, moving from 16 amps to 17 or 18 amps would likely involve a drop in efficiency because it would activate another charge module at very low loading. Of course Tesla might activate both modules at 60% capacity (if that had higher efficiency than one module at full capacity and the second module lightly loaded). Some testing would be needed to find the efficiency "sweet spots" in terms of charging power.

I'm curious if you used the new low-power mode for your recent tests.

 

[mongo]

There are three solid state charging modules in the Cybertruck's on-board charger. Each module can add up to 16 amps, combining for the full 48-amp capacity.

Cybertruck has two 24A AC/DC modules and two DC/DC modules.
Other models have three modules in part to support three phase AC charging in other markets.

 

[hemiarch]

Cybertruck has two 24A AC/DC modules and two DC/DC modules.
Other models have three modules in part to support three phase AC charging in other markets.

So based on @HaulingAss ’s logic above, the optimum charging efficiencies are at about 20-22 amps and 42-44ish amps?

 

[mongo]

So based on @HaulingAss ’s logic above, the optimum charging efficiencies are at about 20-22 amps and 42-44ish amps?

Using their logic, it would scale like that.

 

[hemiarch]

So I bit the bullet and got an apex 300 system yesterday. I ordered from Home Depot so I could return it if it doesn’t work as expected. Nice to still be able to charge on solar even when using the cybertent and not the coody koala 7. I do love my delta pro 3’s, I just wish they were an inch and a half shorter.
First world problems, am I right?

 

[TickTock]

I'm curious if you used the new low-power mode for your recent tests.

Yes, I did turn that on.

 

[HaulingAss]

Cybertruck has two 24A AC/DC modules and two DC/DC modules.
Other models have three modules in part to support three phase AC charging in other markets.

Good to know, I wasn't aware of the change!

 

[HaulingAss]

So based on @HaulingAss ’s logic above, the optimum charging efficiencies are at about 20-22 amps and 42-44ish amps?

I would think so, very disciplined and controlled testing would be needed to confirm, because various non-charging steady or periodic loads could really throw the results.

 

[HaulingAss]

Yes, I did turn that on.

Given that, and assuming all doors, etc. were closed and not periodically activated, the largest uncontrolled variable would likely be the state of charge of the 48V battery at the beginning of the testing. Because I think the BMS would likely tend to charge that whenever plugged into AC power, even if it was not at the bottom of it's normal SOC range. That would make sense from an overall system efficiency sense, but it would throw off the charging overhead during the first hours of charging by absorbing some of the charging energy without accounting for it in the high voltage battery SOC (or miles remaining) figures.

 

[TickTock]

Wow. That’s better than I thought for one unit.
Think you’d have to add the little solar controller unit thing they sell to come close to matching that output with solar input but that would make sense if you had a bed cap.hmmmm
Seriosuly though, check out those allpower panels they are pretty great. Had them for about a year and a half now.

Thanks for the suggestion, @hemiarch!
I decided to grab three of those 400W Allpowers since they are a LOT cheaper than the 350W Bluetti and did a comparison. Despite my confirmation bias really wanting to come up with a good reason to pay the extra for the Bluetti if I had it all to do over, I would have only bought the Allpowers and saved my money. That said, if money is no object and you don't mind paying double for a miniscule improvement, the Bluetti are slightly better in terms of durability and ease of use. If they were the same price or maybe only a $50 difference, I would favor the Bluetti.
Side by side:

Bluetti fit a little better. Here's four - could easily stack six.

Unfortunately, the Allpowers were just a little too wide to fit landscape:

Also too tall to fit two portrait:

The Bluetti did come with a longer cable which is really useful connecting them in parallel (but you can get an extension for $10 so hardly justifies the price):

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