Contra Keelan
Not really contra Keelan, but some pushback on his video that is receiving exuberant praise.
This post intends to discuss the claims made in the video. Althought I might personally be put off by the clickbaity title, clickbaity thumbnail, or manic presentation those are a matter of taste and I will not address them further.
For reference, at @2:40 he describes his travel trailer setup as having
- 600Ah of LiFePO4
- 1,050w of panel on the roof
… with the batteries apparently from this kit ($5,459AUS1 Since the video is featured on that sellers’s page and there is a giveaway associated with that seller, it is not clear whether or not Keelan paid market rate for the gear.
1 - battery capacity
@3:13 everybody says the batteries are the heart of the 12v system
From the solar charge controller’s PoV they are. The bank provides a reference voltage, power for the controller, etc. But this really isn’t what he means.
@3:20 solar is much more important than how you store the energy
This is the first clue that he is generalizing from his use case to a general use case. There are use cases that don’t use solar at all
@3:30 if you can’t even capture the electricity [gestures upward] there is no point in even having these [points to battery bank]
Because solar is the only charging source available? His kit provided a 40A DC-DC charger, so we know that’s not true even in his use case.
@3:38 you see these people putting 900Ah systems in their caravan2, they’ve got 600w of solar it’s just not going to work
Sure it will work. They might not fully recharged off solar but LFP doesn’t require (or even like) full charging.
04:05 after years and years of knowing this stuff I’ve come up with a 2-to-1 ratio
LOL, people have been discussing this and advocating for >1:1 panel-to-bank ratios for a very long time.
2 - solar
Note: @3:18 a drone shot shows the panels shaded by roof A/C
@4:55 solar means absolutely nothing… if you can’t actually regulate that solar
It’s not like people are out there directly connecting panels to battery banks.
@5:10 a solar panel has an output of around 22v… depending on the quality of panels you’ve got
It’s a function of cell count, cell arrangement, and cell output. Panel voltage is not correlated with panel quality.
@05:50 it’s important that you know the max input into a charger like that [MPPT]… we have 2 40A controllers so we could technically have 80A coming from the solar
The 80A (if available) will be on the output side, not the input side.
- his 1,050w rooftop array is made up of 5 panels, so they must be 210w
- using his 22v number, we can back into a Vmp of 17.6v. 210w/17.6v x 5 panels = 59.7A. If 22v is supposed to be Vmp then the max panel current would be 47.7A @6:05 he clarifies he sees ~55A, although this is almost certainly output after DC-DC bucking.
Panel current going into the controller is rarely an issue (see below). Most people will smoke them by overvolting instead.
@6:20 there’s no point having 5 panels if your solar regulator can only regulate 3 of those panels maxxing it out…
MPPT controllers are typically overpaneled (more panel than the controller rating might imply) because panels don’t put out their rated power often (if ever).
@6:30 solar regulators are dirt cheap compared to our solar panels… you might as well overgun your regulators
That is not often the case, unless one got the controllers for free and had to purchase the panels on one’s own dime. Ahem.
The reason MPPT are overpaneled is because upsizing them is $$$, particularly after the 50A mark.
@7:25 if you want to stay offgrid longer all you need to do is get extra solar
That’s quite a claim.
@7:30 I guarantee it’s the cheapest, most simple and easy way
for his use case.
And for mine, too, but that’s not the point.
@8:05 a solar blanket is better than a fix panel in some cases
Yes, when the fixed panels are shaded but there is open sky nearby.
BTW, when the segment @8:155 starts the portable panels are completely shaded. He seems to imply that the panels have built-in controllers, which makes the long leads even more problematic.
@8:50 you can actually pick them up and point them to where the sun is
Not only can you, but you probably must (multiple times a day).
8:55 all day I’ve actually been moving the panels
That is not not my idea of a good use of time
@9:52 get a solar blanket, it’s going to sort out all your needs
Another bold claim.
3 - shore power charging
I agree with this section. People who are have access to pedestal power only need enough converter to
- carry loads
- charge the bank to the desired level during the access to shore power charging
I’d go further and say that when solar charging is present the converter can be a simple, single-stage model set at low Float.
@11:05 every time we pull up a spot where we’re plugging into [shore power] it’s for overnight at least.
Not sure why a guy who plugs in regularly is an expert in offgrid power, but here we are.
4 - LiFePO4 in the engine compartment
Heat absolutely clobbers lithium calendar and cycle life. This is why EVs have thermal management systems. Some Li chemistries are less susceptible but I would not mount LFP underhood if there were any other option.
all [itechworld] orange-top batteries… are underbonnet rated
The orange tops are rated 4,000 cycles to 80% DoD (a reasonable number if charged gently) but are only warranted for 1,095 days (3 year, source). The mfg recommends use of a heat shield. I think they understand that underhood use is brutal and will shorten the life of the battery.
@13:25 we actually run an itech 120x all around Australia
I’d love to see a capacity test of this battery at the 3-year mark. I’d also be interested to know what he paid for it.
@15:29 itechworld are offereing a 5-year warranty
The 5-year warranty is on the Pro line, which costs ~10% more. It would be interesting to see the actuarial numbers on how much more it would cost to extend the warranty from 3 to 5 years.
5 - charging LiFePO4 with AGM chargers
#12:21 now there’s technology in BMSes that allow you to charge a lithium battery off an AGM charging profile
It depends on the battery and the charger.
Generally speaking, AGM profiles Absorp at ~14.4v and Float at ~13.6v. Both of these values are too high for LFP in my opinion.3 Voltages that high are probably ok to make it though the warranty period but lower voltages can help the bank last longer, improve cell balance, and therefore preserve/improve apparent capacity.4
design segment
@17:00 everyone’s needs are different
Glad to hear you say it.
daily power assessment
This section is reasonable.
- @17:05 - tabulate DC loads
- @19:18 - tabulate AC loads - does not include inverter losses, unless I missed it
- select battery capacity on this - does not include charging losses5, unless I missed it. Does not address days of autonomy, although he did oversize the bank 50%.
solar requirement
@24:20 solar panels are horribly inefficient
Panel efficiency is a function of power harvested under lab conditions / meters squared of area.
I think he means “they don’t often make rated power”, which is true enough.
24:35 you’re going to get no charge, 200w solar panel is actually 80w when heated up
- 80w != “no charge”
- other factors are in play here, the cells would have to be be ~304deg F to derate that far. On the upside, you could cook on them.
@24:45 I 100% suggest you get a proper [unintelligible] panels have a proper heatsink on them
He seems to think the aluminum frame is a heatsink. While the frame might wick some heat the interface between frame and cells is minimal. The majority of added cooling will be from underside airflow.
@25:15 you’ve only got six hours a day where there’s optimal sun angle
He goes on to multiply 6 hours x 11A per 200w panel. We don’t have to guess here, we can model it in PVwatts or similar tools.
@25:50 as soon as they get any dust on them, not to mention a rogue pigeon… you’re going to get 2A less
This is really hard to quantity. Sandia labs has measured 5-6% reduction from a heavy dust coating, which would be ~0.6A less. I don’t think dust is worth removing unless one has easy access. Localized opacities like bird poop are worth removing.
@26:33 shade is the biggest nemesis of solar panels
Agreed.
I do my best to avoid shade but this entire spot is canopies. Here is a description of how my system is coping.
multiple charging sources
@27:40 simultaneous charge is the bomb
Agreed.
@28:00 we’ve split up the MPPT regulators so the solar coming into the batteries is on a totally different system than the car alternator charger
IOW, a totally normally setup where both feed that battery bank.
Systems that allow only solar or alternator charging are a minority, only seen on a few DC-DC/MPPT combo units. To with, the Kisae and Sterling that switch to DC-DC-only and the Ring which might switch to solar-only; the documentation on the latter is ambiguous.
conclusion and thoughts
I don’t think this kind of overconfident and oversimplied issuance of “truth” is very helpful to newcomers. There was nothing new or insightful in the video and I’m surprised people are reacting to it so positively.
I suspect beginners want a confident, attractive person to tell them what you do. It’s certainly easier than learning it for yourself. Samuel Butler wrote:
“The public buys its opinions as it buys its meat, or takes in its milk, on the principle that it is cheaper to do this than to keep a cow. So it is, but the milk is more likely to be watered.” – Note Books, 1912.
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