Greetings from car solar land

[amples]

Hello!

I have a car with a 110A alternator. Currently, I have two cheapo 100aH lithium batteries (4s) connected to the starter battery. I initially ran this through one, then two paralleled DC-DC unregulated boost converters (stepping up to lead-acid starter battery) but tried without them and am happy with how BMS CC mode works and can charge <50A (/2 batteries) efficiently with otherwise wasted alternator juice.

I scored some AWFUL 80W CIGS solar panels but, now that they’re glued onto my ride, I’m trying to make the most of it while they last.

To start, I wired them directly to the two auxiliary lithium batteries directly with ring terminals. 3 red and 3 black going to two batteries is odd, but parallel connection is 2AWG so I just split 2+ / 1- to one and 1+/2- on the other.

This is ghetto, but solved an immediate need for power quickly. Glorious when batteries are low, I’m getting <6.5A in so far, but not much sun here yet. Car uses <5 amps in accessory mode so I’m not depleting batteries much when sun’s shining. Feels good!

Question — I’d like to improve this much and document progress, so what are your suggestions?

Details:
Two 100aH batteries are self-heating LiFePo4 batteries with Bluetooth connection to BMS parameters. It’s hokey, but works. It’s cold out, or rainy here for a while so any efficiency gain in appreciated. Looking forward to summer.

Solar: Three <80w CIGS installed panels Vmp ~19, Voc <24, Isc 4.3A. Also one 100w CIGS portable (Vmp 15, Voc 19, Isc 7.8). Not connected yet, gotta figure that out (ring to MC4?). Mostly portable use by why have it sit idle?

Future resources go to: adding raw cells with a decent BMS to avoid pain points like a BLE connection to change undocumented parameters from awful, often crashing and hanging apps written in English-ish. Nice to keep at least one of these pre-built batteries for cold weather reserve.

However I’m stuck on charge controller configuration and purchasing right now.

What gains could I see running these (at least the 3 permanents) in an MPPT controller?

Options I can think of:

Get 100v/30a MPPT and do series connection (panels seemingly have =>2 bipass diodes) (~72v of panels, + accessory ~15v) and stay parallel.

Add 8s lithium and get therial with maybe cheaper 100v MPPT/10-20A to 48v bank and lose my mind attempting to inefficiently buck / complicate with parallel switch for 12v accessories and alternator charging.

I’ll accept much DIY to learn and save money, but figure better to spend on tools / practice that will be useful in future than buy low-grade stuff for current installation specs.

Anyway that’s where I’m starting and hello DIY solar enthusiasts! Ask me anything, I hesitate to elaborate more since this feels long already.

 

[Chuck7454]

with otherwise wasted alternator juice.

The "juice" is technically not waited, it was never there. The mechanical load the alternator puts on the car engine is basically proportional the the amount of electrical power the alternator delivers to the electrical system. The mechanical load is taken from the engine before the engine turns the car tires. As a driver you will adjust the accelerator (a.k.a. gas pedal (we won't be correct if your vehicle is diesel)) to compensate for the Horse Power the alternator takes from the engine without thinking about it.

The term you want to use is "waisted alternator capacity". And hope I did not stray OFF TOPIC too much.

From the language police in the peanut gallery. Chuck

 

[Weekend van]

Alternators run at 100% all the time are typically not long for life. They generally run a short peak output then throttle back for a long happy life at part load.

The only system that isn't a waste is something with permanent magnets. Mercruiser 270 (the diecast half a Ford 460) had them and the regulator shunted excess power as heat into the cooling system. And most old school motorcycles also have a shunt style regulator, but those dump excess power as heat into the air. They are the finned voltage regulators that have good airflow. Those systems generally are not built with a large degree of excess capacity as that would just be more heat generated and needed to be discarded.
The only other excess capacity charging system I know of are small wind turbines, those have a load dump resistor. That is to keep the blades loaded enough they don't over speed.

Beyond that, there is no wasted excess capacity from a charging system. Just more load, more fuel burned, more wear and tear on the alternator along with the added heat load in the alternator.

 

[amples]

I’m noticing a lot of alternator charging hate. What gives? Yes it’s a brushed alternator in a POS car, but it’s running anyway right? It’s not charging in CC mode long due to the LiFePo4 chemistry’s relatively flat voltage curve so the BMS switched to CV pretty quickly.

I think the load at 50A seems fine, but in practice it’s usually <<30. Car uses <40A driving, and I rarely will discharge these batteries so much other than testing cutoffs and for Coulomb counting calibration.

Wasted power — I’m defining it in this context as power generated by alternator that doesn’t sag voltage to the system. Turning HVAC on sags voltage, by comparison, and lessens charge to BMS (checked with clamp ammeter and accurate on cheapo, presumably shunt resistor measurement reported by BMS).

Now if I had regulated DC-DC boost converter stepping up voltage to the batteries I’d understand the concern. Am I just ignorant?

In general, I’ve often wondered why there’s, seemingly, so much overuse of inefficient and redundant conversion in setups I’m seeing. DC>inverter> AC wall wart>DC for charging batteries kinda thing … I charged a 20s4p scooter-type device by setting pots on a boost converter and spared the waste power (>15%)of the in-built car inverter, and the power brick rectifier (+>>30%) for instance.

With greater clarity on these things, I find much added safety is just inefficient. Happy to be wrong, I rather not blow things up, but far as I can tell there’s no problem there and same with alternator charging. I’ve been viewing it as capturing the alternator’s excesses.

Appreciate the feedback. Seriously though, you’re not going to yell at me about the pile of ring terminals on an m8 connector first though?

 

[timselectric]

They are correct.
There is no excess wasted energy available from an alternator.
Whatever you pull from it, must be created by burning fuel. The more you pull, the more fuel you burn.

 

[Enketchum]

Are you running those panels directly to the batteries? No charge controller?

 

[meetyg]

You mention the BMS doing CC/CV charging modes. I'm not aware of a BMS that does this. What kind of BMS is this?
Are you mixing up a BMS with an SCC (solar charge controller)?

 

[amples]

Are you running those panels directly to the batteries? No charge controller?

Yes, for now, pending a permanent design that makes sense to me. Thinking series connecting to MPPT makes sense but there’s inefficiencies stepping down to nominally 12v etc. Just trying to empirically show what’s right here and get through the opinions.

Previously I’d hooked up a portable 12v 70w folding panel to batteries without problem and pulled more power than the PWM controller put out so that got me curious.

For larger installations this is probably silly, and for my current aspirations I’m thinking it’s probably still silly. Edit: I’m just not clear what’s ideal here.

 

[amples]

You mention the BMS doing CC/CV charging modes. I'm not aware of a BMS that does this. What kind of BMS is this?
Are you mixing up a BMS with an SCC (solar charge controller)?

Good question, it’s whatever’s on Himax’s variously labeled batteries. I’d deduced this in the past but can’t find my notes.

Pretty sure I inferred a Texas Instruments BMS (e.g., BQ769x0 series) paired with a cheap Bluetooth chip (likely a generic HC-05 or similar). The protocol between them is likely a proprietary UART or I2C implementation, common for low-cost BMS designs, and so all the apps hang when reading numbers that vary much (3A goes to 13A while voltage goes down .1 etc). The chip may send corrupted or unformatted data (e.g., invalid packets, buffer overflows), causing app crashes. Firmware bugs in the BMS or app misinterpretation of proprietary UART/I2C data exacerbate this, and the common rants about these BMS was a clue for me trying piles of other apps that worked in varying degrees but all suffered similar glitches.

Very powerful platform if setup correctly. The enormous documentation page for developers is crazy and inaccurate though in real-world tests.

In brief IDK and didn’t wind up tearing it open. For personal reasons I wound up having to just use these as-is

 

[amples]

They are correct.
There is no excess wasted energy available from an alternator.
Whatever you pull from it, must be created by burning fuel. The more you pull, the more fuel you burn.

How does one test this? If anything my mileage has stayed the same or actually improved slightly, so I’m running out of ways to understand this opinion in the context of a whole system. RPM same, system voltage same. Hmm… I’m stumped

 

[Enketchum]

Yes, for now, pending a permanent design that makes sense to me. Thinking series connecting to MPPT makes sense but there’s inefficiencies stepping down to nominally 12v etc. Just trying to empirically show what’s right here and get through the opinions.

Previously I’d hooked up a portable 12v 70w folding panel to batteries without problem and pulled more power than the PWM controller put out so that got me curious.

For larger installations this is probably silly, and for my current aspirations I’m thinking it’s probably still silly. Edit: I’m just not clear what’s ideal here.

You lose a lot of power in a PWM controller because it's stepping down the voltage and keeping the same amperage. An MPPT will convert the dropped voltage into amperage and push most of the wattage into the battery, at least as much as efficiency losses will allow.

If you really are pushing ~18 volts into your batteries, I'm surprised the BMS isn't shutting them down early when it sees higher voltage incoming. I would definitely get a solar controller.

 

[rogerheflin]

How does one test this? If anything my mileage has stayed the same or actually improved slightly, so I’m running out of ways to understand this opinion in the context of a whole system. RPM same, system voltage same. Hmm… I’m stumped

You will not be able to measure it. The difference lost in the normal variation of mileage/gasoline/temperature affects on how much fuel the engine burns. You might be able to successfully measure it if you had the engine idling and had access to the fuel injector timing/throttle because then you would be able to see a slight increase in the time the injector was open and/or a tiny bit more opening of the throttle when the alternator is running. But even with access to that data it may be lost in the noise.

Too many people have confidence in being able to test something and get meaningful results when there are too many uncontrolled variables to make the test (and any conclusions) basically useless.

When it was first tested to see if a steam engine consumed heat to make work it was determined that heat was not consumed simply because the steam engine was so inefficient that heat in was with measurement error of heat out.

 

[Enketchum]

How does one test this? If anything my mileage has stayed the same or actually improved slightly, so I’m running out of ways to understand this opinion in the context of a whole system. RPM same, system voltage same. Hmm… I’m stumped

You are already using fuel to idle or drive the vehicle. Adding a few horse power with load on the alternator will not require much more fuel as you are already wasting a lot of fuel just to make the engine spin at idle. I don't see the big concern these commenters are having with charging from the alternator.

 

[amples]

You lose a lot of power in a PWM controller because it's stepping down the voltage and keeping the same amperage. An MPPT will convert the dropped voltage into amperage and push most of the wattage into the battery, at least as much as efficiency losses will allow.

If you really are pushing ~18 volts into your batteries, I'm surprised the BMS isn't shutting them down early when it sees higher voltage incoming. I would definitely get a solar controller.

Under load, voltage is much less as tested to the BMS in its CV mode (it manages this). There’s a 15v cutoff and 13.8v full voltage profile set up.

I shared your concern initially. In fact there’s still some worry I have given how heretical this seems to be! If anything, the problem winds up being unable to reach 100% SoC because the voltage is too low without MPPT. At 70w, a controller’s overhead made no sense and I didn’t want need these charged to max voltage anyway.

Moving forward, MPPT makes sense (either series the 80w horizontally (+~5° slope) roof panels at ~72v plus occasionally add the 100w in parallel to batteries / car or determine whether putting those in series makes sense. Having an optional add-on to a series connection honestly seems troublesome, I’m not quite conceptualizing how that would even work with DIY parts. Maybe a switch to an open pair of MC4 connectors?

 

[amples]

You will not be able to measure it. The difference lost in the normal variation of mileage/gasoline/temperature affects on how much fuel the engine burns. You might be able to successfully measure it if you had the engine idling and had access to the fuel injector timing/throttle because then you would be able to see a slight increase in the time the injector was open and/or a tiny bit more opening of the throttle when the alternator is running. But even with access to that data it may be lost in the noise.

Too many people have confidence in being able to test something and get meaningful results when there are too many uncontrolled variables to make the test (and any conclusions) basically useless.

When it was first tested to see if a steam engine consumed heat to make work it was determined that heat was not consumed simply because the steam engine was so inefficient that heat in was with measurement error of heat out.

This is an excellent point that rings true here. Complex and complicated systems require some systems theory and consistent notes to even get a basic grasp of fundamentals.

I’ll say this though: all initial testing was done at idle as a control. I’d like to take some more measurements, and your feedback on fuel injector timings etc are appreciated. That’s a big clue there so cheers. I’ll note to figure out if there’s a way to log this automatically. I’m NOT a car guy but grateful to learn!

That’s why I thought to test this and solicit responses — piles of uncontrolled variables, limited tools on hand, uncertain what’s cost effective to purchase, and conflicting opinions clouding my initial strategy (battery balancers, lots of expensive blue boxes, all money, time, and energy sapped by them didn’t appeal — I’d just not use a solar panel!) So I started small and am judging future improvements by what’s demonstrable.

 

[timselectric]

How does one test this? If anything my mileage has stayed the same or actually improved slightly, so I’m running out of ways to understand this opinion in the context of a whole system. RPM same, system voltage same. Hmm… I’m stumped

The only way to verify it is to measure fuel consumption accurately in a controlled testing environment.
But it should make sense to you that energy isn't free. Something must be consumed in it's creation/transformation.

 

[amples]

You are already using fuel to idle or drive the vehicle. Adding a few horse power with load on the alternator will not require much more fuel as you are already wasting a lot of fuel just to make the engine spin at idle. I don't see the big concern these commenters are having with charging from the alternator.

Agreed. I’m not going to idle this just to charge batteries regularly, hence installing solar panels, and the overhead is minimal from my limited observations.

So far I’m excited and pleased with results from this classless setup, and very happy to have all this stored power when parked. Keeping things topped up with the new panels is already living the basic dream. Right now as I type this, with partly cloudy morning skies, far from the equator, and after a bird took a massive dump on my panels, I’m not even using battery power while car’s accessory mode is on (load: stereo going, 50w electric blanket, fan, and charging this phone I’m typing on). Power windows etc draw amperage from batteries (currently +.5-2A, dipping to -10A spikes during that).

In summer there’s a chance of testing car’s voltage transient protection, in theory, if batteries are all 100% and there’s no load for a while. But that’s pretty abstract still given the voltage sag etc, though I’ll hopefully have a better grasp on this all by then. So far the system is not getting >14.4v and I’d think cars should be able to handle transient voltage spikes ok. I can disconnect starter battery for now, and possibly replace the group 86 tray will LiFePo4 cells at some point even. These two 100aH batteries already can start the car in a pinch! Adding capacity there makes sense. Ok I’m getting ahead of myself now

 

[amples]

The only way to verify it is to measure fuel consumption accurately in a controlled testing environment.
But it should make sense to you that energy isn't free. Something must be consumed in it's creation/transformation.

Literally this is true, and I started with much caution so I’ve been tad surprised and happy with results. My worry was bearings seizing and alternator grenading on the freeway because batteries drew 50A each (BMS upper CC limit).

Kind of you to offer insights on alternator load and wear— appreciate the seasoned perspectives. To the points about “wasted alternator capacity” being a better term than “wasted energy” etc — I was attempting to be brief and conversational, but you’re obviously correct. I agree that high loads draw engine horsepower, increasing fuel burn and potential wear etc. I’ve been monitoring the charging dynamics closely. Typically the voltages for LFP are so stable across 20-80% SoC that the problem is actually wasting running alternator time by drawing only a few amps.

Details: The 50A peaks I noted earlier lasted under 10 minutes during CC mode (e.g., first drive hit 47.78A, most of that idling before driving while I set multimeter on dash for reading), dropping to ~8A/batt in CV mode (~27A to packs for 18 minutes driving, per notes, 18-22A with HVAC on, then always <<18 after that, and ~4A between >85% 4s SoC).

I’ve checked alternator temperatures after drives and haven’t noted a meaningful difference—surprisingly, my mileage seems to have stayed the same or even increased slightly, which has me stumped still. Maybe the stable, slightly higher voltages improve timings? Complex system here, hard to pinpoint.

I’m not dismissing your expertise; I’m just trying to reconcile this with your concerns about lifespan and heat load as isolated factors. Could the brief spikes and low CV currents (e.g., 0.618A/batt at 14.259V for last hour of drive) be less taxing than expected?

At first batteries were connected on scrap ~18awg speaker wire, and CV mode handled that fine (drawing measly 8A), but this is now on existing 4AWG CCA (awful aluminum!) that came with car for a subwoofer that I’ve ditched. I’m planning to upgrade wiring to 2 AWG copper in future. Might test those 30A boost converters configured in opposite direction to optimize charging without overloading, but then I’d need to setup a relay to cutoff starter so auxiliary use isn’t a drain (or switch to LFP there too, with discharge FETs set off >13v or whatever)

Your thoughts are relatable—it’s my default understanding of how the world works, but hope my results are curious and warrant exploration. Any specific heat thresholds or load patterns to watch for? Your experience could help me fine-tune this setup safely. Thanks again.

 

[Enketchum]

Agreed. I’m not going to idle this just to charge batteries regularly, hence installing solar panels, and the overhead is minimal from my limited observations.

So far I’m excited and pleased with results from this classless setup, and very happy to have all this stored power when parked. Keeping things topped up with the new panels is already living the basic dream. Right now as I type this, with partly cloudy morning skies, far from the equator, and after a bird took a massive dump on my panels, I’m not even using battery power while car’s accessory mode is on (load: stereo going, 50w electric blanket, fan, and charging this phone I’m typing on). Power windows etc draw amperage from batteries (currently +.5-2A, dipping to -10A spikes during that).

In summer there’s a chance of testing car’s voltage transient protection, in theory, if batteries are all 100% and there’s no load for a while. But that’s pretty abstract still given the voltage sag etc, though I’ll hopefully have a better grasp on this all by then. So far the system is not getting >14.4v and I’d think cars should be able to handle transient voltage spikes ok. I can disconnect starter battery for now, and possibly replace the group 86 tray will LiFePo4 cells at some point even. These two 100aH batteries already can start the car in a pinch! Adding capacity there makes sense. Ok I’m getting ahead of myself now

How are the car systems handling the increased voltage from the solar panel? What are you seeing at your connection point? 15-16 volts?

 

[amples]

How are the car systems handling the increased voltage from the solar panel? What are you seeing at your connection point? 15-16 volts?

Everything in the car functions better. Windows roll faster, starting car is much faster and cleaner (especially noticeable when left parked for weeks at 14°F), and mileage is same or slightly higher. That’s all due to extra batteries.

Solar is putting a measly >2.5A per panel in without controller, but nice improvement. Sun just poked out again and my starter battery is disconnected so I’ll check voltage now… 13.3v

 

[timselectric]

Literally this is true, and I started with much caution so I’ve been tad surprised and happy with results. My worry was bearings seizing and alternator grenading on the freeway because batteries drew 50A each (BMS upper CC limit).

Kind of you to offer insights on alternator load and wear— appreciate the seasoned perspectives. To the points about “wasted alternator capacity” being a better term than “wasted energy” etc — I was attempting to be brief and conversational, but you’re obviously correct. I agree that high loads draw engine horsepower, increasing fuel burn and potential wear etc. I’ve been monitoring the charging dynamics closely. Typically the voltages for LFP are so stable across 20-80% SoC that the problem is actually wasting running alternator time by drawing only a few amps.

Details: The 50A peaks I noted earlier lasted under 10 minutes during CC mode (e.g., first drive hit 47.78A, most of that idling before driving while I set multimeter on dash for reading), dropping to ~8A/batt in CV mode (~27A to packs for 18 minutes driving, per notes, 18-22A with HVAC on, then always <<18 after that, and ~4A between >85% 4s SoC).

I’ve checked alternator temperatures after drives and haven’t noted a meaningful difference—surprisingly, my mileage seems to have stayed the same or even increased slightly, which has me stumped still. Maybe the stable, slightly higher voltages improve timings? Complex system here, hard to pinpoint.

I’m not dismissing your expertise; I’m just trying to reconcile this with your concerns about lifespan and heat load as isolated factors. Could the brief spikes and low CV currents (e.g., 0.618A/batt at 14.259V for last hour of drive) be less taxing than expected?

At first batteries were connected on scrap ~18awg speaker wire, and CV mode handled that fine (drawing measly 8A), but this is now on existing 4AWG CCA (awful aluminum!) that came with car for a subwoofer that I’ve ditched. I’m planning to upgrade wiring to 2 AWG copper in future. Might test those 30A boost converters configured in opposite direction to optimize charging without overloading, but then I’d need to setup a relay to cutoff starter so auxiliary use isn’t a drain (or switch to LFP there too, with discharge FETs set off >13v or whatever)

Your thoughts are relatable—it’s my default understanding of how the world works, but hope my results are curious and warrant exploration. Any specific heat thresholds or load patterns to watch for? Your experience could help me fine-tune this setup safely. Thanks again.

Not much to add to your situation. But it's possible that you are operating in the efficiency sweet spot for your alternator. And this is possibly why you aren't seeing much difference.

 

[Enketchum]

Everything in the car functions better. Windows roll faster, starting car is much faster and cleaner (especially noticeable when left parked for weeks at 14°F), and mileage is same or slightly higher. That’s all due to extra batteries.

Solar is putting a measly >2.5A per panel in without controller, but nice improvement. Sun just poked out again and my starter battery is disconnected so I’ll check voltage now… 13.3v

Oh wow, I was expecting a lot more voltage. I guess that's why everything is peachy. Nice

 

[rogerheflin]

Oh wow, I was expecting a lot more voltage. I guess that's why everything is peachy. Nice

The battery will pull the voltage down. Basically the voltage will be battery voltage + resistance of wire from battery to where your voltmeter is * amps into the battery.

Where you will have an issue is when the batteries charge and the BMS disables charging, and then the voltage will quickly approach Voc of the panels on the car electrical system (since there is little current flow) and that may not be good for the car depending on how high Voc is, and what voltages a car is normally designed to survive.

 

[amples]

Hoped so!

Grenading alternators from battery draw or damaged IPM from Voc numbers was a concern, but so far so good. I tried to calculate for this but manufacturer data for panels was incomplete so I winged it based on my experience with the “70w” (was rebranded 60w) solar panel hooked to starter before this and data sheets from the low-grade Vietnamese exporter of the cells.

So far seems I’ve paneled correctly. Will holler if I go kaboom, though hopefully I’ll figure out right-sizing an MPPT for this purpose and get more juice out of these panels in summer. Right now, the added idle overhead (>.5-2w) and step-down costs aren’t even necessarily beneficial (think rain, clouds). Sure, an MPPT could squeeze 15A vs. 12A—call it inefficient while I’m testing real-world output while I shop for a controller and study car electrical design.

Thinking the spendy Victron 100v/30 covers me at 12v nominal parallel connection, but in the real world this is likely overkill. In theory, the 20A model would limit my watt output if I stick with 12v.

Midnight Solar or one of the domestically built devices seem far better value, but the second hand market is risky and the various Arlington, WA manufacturers have been acquired by global energy corporations now it seems. Same with CIGS panels locally, not produced here for over a decade now, so rapidly delaminating imports were the only option.

Made in India Victron, especially for their prices and low gauge connections, and risking more vendor lock-in with their Bluetooth connections irks me but may be suitable here.

The battery will pull the voltage down. Basically the voltage will be battery voltage + resistance of wire from battery to where your voltmeter is * amps into the battery.

Where you will have an issue is when the batteries charge and the BMS disables charging, and then the voltage will quickly approach Voc of the panels on the car electrical system (since there is little current flow) and that may not be good for the car depending on how high Voc is, and what voltages a car is normally designed to survive.

Exactly!

A simple 5w load (5w Bluetooth controlled USB fan + the regulator) is bare minimum constant load in this picture.

My operating assumptions and theories followed these details:

Car has transient voltage suppression or it’d be toast before I bought it. 14.8v sustained, <16v occasionally, and 24V max before damage occurs. Then I found SAE J1113-11 which says car electronics tolerate 16V continuous, 24V transients (<1s) which intuitively made sense.

5W fan = 0.4A at 12V. Solar Isc = 12.96A—voltage clamps to ~12V–14V (fan + regulator + >50ma IPM / car draw when parked). Add USB-C (10W = 0.8A) or blanket (45W = 3.75A), even a dash cam, and 25V never happens — panels can’t push past 12.96A. Expected result is car bus stays <15v so TIPM/ECU safe.

Zero draw doomsayer’s scenario is a 25V Voc hitting the bus. That was my 2nd concern after alternator. TIPM/stereo have transient voltage suppression (TVS diodes, FETs)—24V spikes are standard in automotive (jump-start specs for radio confirmed). Sustained 25V could stress regulators so armchair’s napkin shows 5–10% chance of damage over minutes, not instantly, but was worth considering and hoped I was right before plugging this in. Real world odds are <<1% still— IPM death needs no load, BMS C/D MOS off or failed, cold boost (-10°C Voc ~+5%, 0.11V/cell for CIGS, ~25.0V total), max sun (1000 W/m² — I wish!). Anyway figured an additional 5W load alone kills it worst case. This even assumes the buffering starter battery is disconnected! Worst case risk is lead acid overcharge from 12A over days could push it past 14.4V to 15V+, slowly gassing or boiling it if left for days–weeks. Not happening!

Alternator: My 110A alternator’s likely fine—solar’s <12A (240W) runs the show now. Heat and time kill those per industry data and experience. 0.06V drop at 12A (10 AWG), 0.8V at 31A (CCA)—planned it, built it, ran it, no heat. Can show my work if that’s helpful to someone.

I cut the MC4 connectors off the six 2’ 12AWG wires from the panel to reduce bulk and, frankly, a sealed and soldered +crimped connection felt better than brittle no-name MC knockoffs.

Solar run continues to six 5’ >>10 AWG (5.2 mm², high-strand tinned copper, silicone insulator), 0.06V drop to 200Ah LiFePO4 at the ring terminals I crimped / sealed. This is lame and bulky, and overkill, but I’ll redo this when I have a final plan in place. This test gave me much real-world insight.

Driving? 16’ 4 AWG CCA (0.032 Ω) limits it to 31A—(14.8V - 13.6V) / 0.032 Ω—28% of capacity. Copper’s coming (0.00397 Ω, 50A) — BMS-limited, still <<70A safe zone. Solar should cut alternator runtime anyway.

Hot take: After watching a certain company’s ‘smoking alternator’ videos I estimate that’s overhyped garbage for advertising overpriced, blue DC-DC boost converters to people without a spine.

BMS Reality: ‘Faulty? Should’ve shut down?’ Nope—15V cutoff, 23.8V Voc drops to <14.6V under load, alternator’s ~14V is BMS-spec. $100 batteries these days have self-heating mats—charges redirect input at 0°C, re-enabling C MOS per params. No discharge damage, no alternator drain. It’s balancing cells post-charge, not frying them, and balancing alone is second-line defense against TVS. Bluetooth logs prove it works. Not well documented, but not encrypted and obscured either.

Welp that’s a lot, but I’m still wanting to learn about:

Series vs parallel
MPPT options
Streamlining wiring / bus bars / decent DC rated switches that don’t cost more than batteries these days
Questions I didn’t think to ask etc

Looking forward it! Holler if I’m guilty of being wrong on the internet. Thick skin here.