Two fold purpose for vehicle solar panel

[Arbee]

I must apologize. I am trying to solve a problem by asking the question differently when I post, simply as a product of my learning more each time.

I have a 100W flexible solar panel on the roof rack of my Jeep Wrangler.

With the energy it produces I was hoping for it to do two things with it when the vehicle is parked:

1) Trickle charge the vehicle's engine (i.e. starter) battery (type AGM) during daylight, AND

2) Use that solar panel to run a 4.5W appliance at all times, day or night, again, only when the vehicle is parked.

To make a long story short, energizing the 4.5W appliance off the starter battery---even if that battery is trickle charged, is a non starter. At least let's assume that.

Since I wish to run the 4.5W appliance at all times, (I think that) logic would dictate that I use the solar panel to charge an independent battery, dedicated to the task of energizing the 4.5W appliance, with enough energy in that battery to not only compensate for the 4.5W draw of it during daylight hours by the appliance, but give that battery enough power to make it through the evening hours with this constant 4.5W appliance draw.

I thought about using a LiFePO4 battery in the vehicle's cargo area--given their safety record and voltage retention with temperature drops-but as I found out, such batteries can't be charged below freezing. (I live in the Northeast US.)

I thought about using a lead acid battery but have heard (maybe not entirely truthfully) that it's not a good idea to keep such batteries in the interior spaces of a vehicle.

I thought about buying one of those LiFePO4 batteries whose charging source first heats the battery to an acceptable temperature and then charges it, but I don't want to break the bank with such a battery's cost.

From a pure power needs standpoint, I imagine that a 10Ah battery would be adequate to run the 4.5W appliance.

Maybe there is a cheaper battery warming blanket that turns on and off with temperature that I can use to heat a LiFePO4 battery while its charging. It would seem that my solar panel would produce enough power to trickle charge the vehicle's battery, warm the LiFePO4 battery, and charge the LiFePO4 battery.

Any recommendations on components to do this, other than the solar panel I already own, would be greatly appreciated. I guess a controller with temperature settings would be useful.

Is there a controller that can handle charging two batteries, let alone of different types? Am I approaching this problem the wrong way? Can I split the cable coming off the solar panel to have one side trickle charge the starter battery with one controller, and the other side charge the battery for the 4.5W appliance?

Please explain to me at the newbie level.

 

[snoobler]

I must apologize. I am trying to solve a problem by asking the question differently when I post, simply as a product of my learning more each time.

I have a 100W flexible solar panel on the roof rack of my Jeep Wrangler.

With the energy it produces I was hoping for it to do two things with it when the vehicle is parked:

1) Trickle charge the vehicle's engine (i.e. starter) battery (type AGM) during daylight, AND

2) Use that solar panel to run a 4.5W appliance at all times, day or night, again, only when the vehicle is parked.

To make a long story short, energizing the 4.5W appliance off the starter battery---even if that battery is trickle charged, is a non starter. At least let's assume that.

Since I wish to run the 4.5W appliance at all times, (I think that) logic would dictate that I use the solar panel to charge an independent battery, dedicated to the task of energizing the 4.5W appliance, with enough energy in that battery to not only compensate for the 4.5W draw of it during daylight hours by the appliance, but give that battery enough power to make it through the evening hours with this constant 4.5W appliance draw.

I thought about using a LiFePO4 battery in the vehicle's cargo area--given their safety record and voltage retention with temperature drops-but as I found out, such batteries can't be charged below freezing. (I live in the Northeast US.)

I thought about using a lead acid battery but have heard (maybe not entirely truthfully) that it's not a good idea to keep such batteries in the interior spaces of a vehicle.

I thought about buying one of those LiFePO4 batteries whose charging source first heats the battery to an acceptable temperature and then charges it, but I don't want to break the bank with such a battery's cost.

From a pure power needs standpoint, I imagine that a 10Ah battery would be adequate to run the 4.5W appliance.

Maybe there is a cheaper battery warming blanket that turns on and off with temperature that I can use to heat a LiFePO4 battery while its charging. It would seem that my solar panel would produce enough power to trickle charge the vehicle's battery, warm the LiFePO4 battery, and charge the LiFePO4 battery.

Any recommendations on components to do this, other than the solar panel I already own, would be greatly appreciated. I guess a controller with temperature settings would be useful.

Is there a controller that can handle charging two batteries, let alone of different types? Am I approaching this problem the wrong way? Can I split the cable coming off the solar panel to have one side trickle charge the starter battery with one controller, and the other side charge the battery for the 4.5W appliance?

Please explain to me at the newbie level.

As has been identified, you likely have serious problems with either 1) your existing vehicle batteries and/or 2) your trickle charger, and your perceived solution is based on those factors, so your perception is skewed and is forcing backward thinking.

You've been given:
Diagnostic recommendations to address your vehicle's problem.
A very simple inexpensive solution that literally solves all your problems IF you have reasonably healthy vehicle batteries.

You need to FIX the problems.

THEN you can implement a solution.

 

[Arbee]

Yes, I've been given your answer sir previously, but I can't implement it. I'm sorry if you think you're the final word. Hence my desire for another opinion.

I respectfully disagree with you on there either being a problem with my trickle charger or the vehicle's batteries, and unless you are truly proficient in the electrical system of a 3.6L JL Wrangler, with 2 batteries, I'd suggest you not be so quick to rush to that judgement.

Both batteries were load tested by the dealer (showing me video of same) to be fine. Despite that fact it is not uncommon for their composite voltage to get to 12.3V or lower when it is cold out, which will shut off my appliance, despite the presence of a mere generic trickle charger. Granted, I could set the appliance threshold for shutoff lower, but I don't want to risk getting to a voltage that might not crank the engine.

Your answer was: you connect your appliance to the vehicle's batteries and call it a day. Charge the batteries from a better trickle charger or the solar panel. Again, I can't do that within the design parameters of a vehicle Chrysler says is operating just fine electrically.

I'm sorry if you're offended that your solution won't solve my problem. I'd be happy to follow it if it did. I'm sorry you feel offended--if you do--that I can't follow that advise or that someone else might have (gasp) another way to address this.

This is why I was looking at the dedicated LiFePO4 battery route, whose "achilles heel" is the ability to charge--as you probably know better than I do--in below freezing temperatures.

Have no solution there--I respect that. But get annoyed that I'm not following your advice when I can't, or that it's the only way to solve this problem....that's harsh.

Wanna get mad at the way FCA (i.e. Chrysler) designed the batteries in a JL Wrangler 3.6L vehicle: you're preaching to the choir.

It would be one thing if you offered a solution I could follow and then didn't do it. Then I'd see your frustration.

We also have a saying in my family for someone who can't accept that their solution isn't being followed: "answerhole."

It's not that I don't appreciate your help. I do. It's that I can't use it and you can't seem to accept that.

Your being forced to reply?

Thoughts?

 

[snoobler]

Having repaired over 400 vehicles and dealt with all kinds of 12V automotive battery issues and tested literally over 11,000 batteries of various types, I can confidently say that you are wrong. The dealership has NO interest in saying anything is wrong as they are on the hook for it if it's still under warranty. I have seen dozens and dozens of dealership incidents where they try to weasel out of responsibility for an issue or recommend unneeded repairs.

My favorite is a local dealership insisting a vehicle needed $3800 in repairs. I got him going with a jump start and 5 gallons of gas. That was 3 years ago, and he contacted me a year ago to let me know everything was working great. The dealership grossly misdiagnosed the issue and likely took advantage of this gentlemen because of his broken English and strong European accent.

Next favorite is a dealership who voided an owners warranty because he didn't disconnect his 12V battery as specified in the owner's manual when parking for 6 months (snowbird). They charged him $1000 in diagnostics with no fix and quoted him $8000 in repairs. I got him going for $800. This exact issue on this particular model of vehicle has repeated itself 9 times in the last 4 years with the same dealership behavior from multiple dealerships across the Phoenix metro area. The next 8 folks only got charged $400 since I got it down to a much shorter job.

Rule 1: Never trust a dealership.

There is NO WAY a battery with a 3A charger on it can drop to 12.3V unless it has a VERY heavy load on it, OR the charger is malfunctioning and not supplying 3A.

Given:
Cold climate
2-3 years old
Batteries subjected to abusive conditions (constant load, infrequent driving, questionable battery maintenance)

The three factors above SCREAM your batteries are likely at end-of-life.

My motivation is to help you and offer you an inexpensive solution and keep money in your pocket.

The dealer's motivation is to extract as much cash from you as possible and avoid any kind of liability.

Good luck.

 

[Freep]

Given:
Cold climate
2-3 years old
Batteries subjected to abusive conditions (constant load, infrequent driving, questionable battery maintenance)

The three factors above SCREAM your batteries are likely at end-of-life.

With those givens, absolutely. It's also a relatively cheap and easy fix.

 

[HRTKD]

A friend of mine had electrical problems with his pickup truck this week. The local auto parts store tested his battery and pronounced it OK. I pointed out the signs to him that his battery was not OK. He replaced the battery today and that cleared the electrical problems.

In one of the truck forums that I'm on, we have a saying, "It's always the battery."

I have a 2017 F-350 that will sit for a couple months without starting. It goes on the smart battery charger within a day after parking it. I expect the batteries to last for at least a couple more years with the TLC they get.

Most flooded lead acid car batteries are good for three years.

It sounds like you're starting with a weak foundation.

 

[Arbee]

I have additionally had the batteries (again there are two in the JL Wrangler) individually tested at an auto parts store since last writing and those guys also found them to perform adequately, if not, to be fair to facts and the above posters, with raving reviews.

(FWIW I'm very conversant in what wires to disconnect on the vehicle to test each battery separately and in unison and did this at the auto parts store for the associate there who connected his tester.) The batteries are normally in parallel, as per the vehicle electronics, 99.9% of the time but for an instant prior to cold crank, and during engine start stop (ESS) events when the smaller of the two batteries runs appliances while the engine/alternator is off at a traffic light, preserving the larger battery for engine cranking after the ESS event is over.

Perhaps those batteries are on their way out. Perhaps just the smaller of the two is. Lord only knows how many owners have had one or more of these batteries replaced under warranty and complained about the design of the ESS system--which FCA (Chrysler) themselves changed (through downloads/flashes) since the JL's release in 2018 to not cripple the vehicle if the smaller battery lacked charge upon engine crank. Purists have complained about the inherent problems of two batteries with such dissimilar amp hour ratings being paired. After market vendors have devised upgrades and made good money selling them despite their price e.g.

I don't deny or dispute the knowledge of those above as it relates to auto mechanics, and within this realm, batteries. I do wonder how many have worked on two battery ESS systems, particularly the 3.6L JL Wrangler's.

So, independent of your thoughts, as I carefully monitor those batteries, yesterday morning their composite voltage was around 12.5V resting. I have a mere 3 amp trickle charger on them from Deltran at all times during when the vehicle's at rest: a device that paradoxically would enjoy rave reviews on a Wrangler forum, but on a Solar one be critiqued due to its generic lack of AGM battery specificity and lack of temperature sensitive logic, etc. It is conceivable at night that this voltage drops below 12.3V, where my dash camera (the subject of all this effort) is programmed by me to turn off.

Sure, I could make that dash camera parking mode battery voltage threshold lower, or replace those vehicle batteries out of pocket--heck, buy one of those aftermarket kits...

I may have to. But in the meantime here is my plan:

I am splitting the power off my 100W Solar panel on the roof rack into two 2 charge controllers, one designed for multiphase charging of the vehicle's AGM batteries, provided the engine is not on, and the other designed for a dedicated LiFePO4 battery that resides in my cargo area.

I bit the bullet and bought RELion's LT 20 amp unit, which is suppose to first divert charging power, as I suspect many of you know, to heating the battery to adequate temperatures, if necessary, before charging it, while it runs my dash camera at all times day or night, except for when the vehicle is cranked: where the camera will get its power from the vehicle's batteries. One would hope the LiFEPO4 battery more resistant to voltage drops with temperature drops than the vehicle's AGM type batteries, combined with my relaxing the voltage cutoff threshold for the dash camera in parking mode once hooked up to the LiFEPO4 battery, having no fear of it affecting the vehicle's batteries for cranking.

Is this a bit of a Rube Goldberg device ? Maybe. Would it have been cheaper to run the dash camera off the vehicle's batteries after replacing them? Maybe (although perhaps not while that vehicle sits distal in some parking lot to shore power, like in some outdoor parking lot near the airport.) All said and done this solution provides never ending power to the dash camera when the vehicle's at park compared to this alternative which neither does, nor can be charged in cold weather or when the vehicle is off dash cam battery.

If this fails--I've known worse in life. I don't think I'm being defiant. I am all over checking those vehicle batteries like you're suggesting, replacing them if need be. I am though about avoiding them for other things while the vehicle is at rest precisely for the concerns you raise about their reliability. And I do appreciate the good intentions and time of those above.

 

[snoobler]

It is not recommended to attach a single solar panel to two different charge controllers. That may not be what you're describing, but that's what it sounds like. Results are unpredictable at best. MPPT charge controllers vary voltage and current to find optimal power. If two are trying to do that at the same time, performance will suffer. The charger capacity battery may get all the charge while the other gets none.

To reiterate:

Panel ------> charge controller ------> healthy chassis 12V -------> Dash cam

Would ensure the ability to 1) fully charge the battery on a day with clear skies and continuous solar exposure and 2) sufficient voltage to run the cam and start the vehicle for up to 3 days without sun. It wouldn't care whether the engine is running or not.

I know you don't want to hear it, but your AGM batteries should never be under 12.8-12.9V if fully charged. If you see them sitting at 12.5V, they are discharging and/or the tender isn't supplying 3A. My 936Ah (about 12 times the size of your battery) 12V bank sitting 7 feet from me is being floated at 13.5V with 0.6A. Your Tender could float my 500# of lead-acid batteries if it's functioning properly.

There's a perceptual difference between something that only starts a car and something that's 25% of a system that powers your life. That's why automotive toys get panned on a solar forum for their inadequacy. Solar forums view batteries as critical. Wrangler forums view batteries as critical when their car doesn't start. Are better then nothing for keeping an automotive 12V battery charged? If functioning properly, absolutely. Are they optimal? Not at all.

 

[Arbee]

It is not recommended to attach a single solar panel to two different charge controllers. That may not be what you're describing, but that's what it sounds like. Results are unpredictable at best. MPPT charge controllers vary voltage and current to find optimal power. If two are trying to do that at the same time, performance will suffer. The charger capacity battery may get all the charge while the other gets none.

To reiterate:

Panel ------> charge controller ------> healthy chassis 12V -------> Dash cam

Would ensure the ability to 1) fully charge the battery on a day with clear skies and continuous solar exposure and 2) sufficient voltage to run the cam and start the vehicle for up to 3 days without sun. It wouldn't care whether the engine is running or not.

I know you don't want to hear it, but your AGM batteries should never be under 12.8-12.9V if fully charged. If you see them sitting at 12.5V, they are discharging and/or the tender isn't supplying 3A. My 936Ah (about 12 times the size of your battery) 12V bank sitting 7 feet from me is being floated at 13.5V with 0.6A. Your Tender could float my 500# of lead-acid batteries if it's functioning properly.

There's a perceptual difference between something that only starts a car and something that's 25% of a system that powers your life. That's why automotive toys get panned on a solar forum for their inadequacy. Solar forums view batteries as critical. Wrangler forums view batteries as critical when their car doesn't start. Are better then nothing for keeping an automotive 12V battery charged? If functioning properly, absolutely. Are they optimal? Not at all.

Maybe I am missing something but your suggestion seems to propose the energization of my 4.5W dash camera with no battery in between it and the charge controller---or perhaps in my ignorance are you saying that the dash camera connects to the vehicle's battery positive terminal, and simply a body ground on the negative side? Maybe that is what you mean by "healthy chassis 12V."

If so, my bad.

Thank you for acknowledging that I don't want to hear that my AGM batteries should not, fully charged, be below 12.8V. I say that humbly, not arrogantly. Nobody I know with a 3.6L JL Wrangler though is getting that. It's one of the most hotly discussed things about the vehicle on its most predominant forum...that and the engine start stop system related to it, particularly in colder weather, for example: https://www.jlwranglerforums.com/forum/threads/battery-voltage-driving-me-crazy.11219/ .

Just as assured as I am from your peers here on a solar forum for being unreasonable for not subscribing to your thoughts on full charge AGM battery voltage, if I came to the aforementioned forum espousing your ideas on voltage on the 3.6L model I'd be flamed no less, likely more. (My discussion does NOT include other battery systems in this product line like mild and soon to be full hybrid product offerings, for example.)

You disagree with splitting my solar panel into two charge controllers. At least on this we have something to work with, maybe.

Could you "meet me in the middle" and propose a situation where a single charge controller energizes the aforementioned RELion 20 amp LiFePO4 LT (low temperature) battery, which in turn both energizes my 4.5W drawing dash camera, AND trickle charges--with hardware you suggest (I honestly don't know--a DC to DC converter???) --off of this RELion battery, the vehicle's batteries, as along as the engine is not cranked (so as to not interfere with the smart charging aspects of the vehicle design and trickle charge the vehicle batteries at the same time that the alternator is feeding them?)

Please appreciate I am not stubborn, obstinate defiant, overconfident, trolling, or narcissistic. Rather I am caught between two worlds with different battery philosophies. If you have no answer that's fine. If you feel it indicated to reply to the effect of having no suggestions within the model I've laid out for myself that's fair too. Maybe you feel that only a separate solar panel dedicated to trickle charging the vehicle's batteries is my only play within the framework I've established for myself.

But please, don't throw flame--I'm already getting that from the Wrangler forum side of things.

 

[HRTKD]

Just for the record, I agree with snoobler that 12.5v is not a fully charged (lead acid based) battery. If I saw that voltage reading on my Trojan T-105 6v batteries (two, cabled in series to 12v) I would wonder what was going on. I also agree that using two solar charge controllers on the same solar panel (or set of solar panels) is at the very least uncommon and at worst likely to not give you the results you want.

The simple solution is one controller that charges your existing battery system, with the dashcam wired from that same existing battery system. If I was in your situation, this is what my first implementation would be. If it didn't work, only then would I consider a more complicated design to include an additional battery.

 

[snoobler]

Just for the record, I agree with snoobler that 12.5v is not a fully charged (lead acid based) battery. If I saw that voltage reading on my Trojan T-105 6v batteries (two, cabled in series to 12v) I would wonder what was going on. I also agree that using two solar charge controllers on the same solar panel (or set of solar panels) is at the very least uncommon and at worst likely to not give you the results you want.

The simple solution is one controller that charges your existing battery system, with the dashcam wired from that same existing battery system. If I was in your situation, this is what my first implementation would be. If it didn't work, only then would I consider a more complicated design to include an additional battery.

That is exactly what I have proposed.

Maybe I am missing something but your suggestion seems to propose the energization of my 4.5W dash camera with no battery in between it and the charge controller---or perhaps in my ignorance are you saying that the dash camera connects to the vehicle's battery positive terminal, and simply a body ground on the negative side? Maybe that is what you mean by "healthy chassis 12V."

If so, my bad.

I am showing how components are connected, not wired. I trust you to figure out that both (+) and (-) have to be connected at each stage.

"heathy chassis 12V" = your starter battery using RV terminology.

Thank you for acknowledging that I don't want to hear that my AGM batteries should not, fully charged, be below 12.8V. I say that humbly, not arrogantly. Nobody I know with a 3.6L JL Wrangler though is getting that. It's one of the most hotly discussed things about the vehicle on its most predominant forum...that and the engine start stop system related to it, particularly in colder weather, for example: https://www.jlwranglerforums.com/forum/threads/battery-voltage-driving-me-crazy.11219/ .

Just as assured as I am from your peers here on a solar forum for being unreasonable for not subscribing to your thoughts on full charge AGM battery voltage, if I came to the aforementioned forum espousing your ideas on voltage on the 3.6L model I'd be flamed no less, likely more. (My discussion does NOT include other battery systems in this product line like mild and soon to be full hybrid product offerings, for example.)

Unless the Jeep battery uses a custom AGM battery with completely unique chemistry that no other 12V lead-acid AGM battery on the planet has ever used, 12.5V on full charge is not possible. It is at a lower state of charge, or it has a significant net current flowing out of it. In your case, this notably exceeds 3A, or your tender is not flowing 3A (all of which can be confirmed with measurements.

Note that manufacturers have been mucking with charge profiles for some time to "tweak" fuel efficiency. Honda is the worst and has been doing it the longest. They do not follow a traditional bulk/absorp/float, but they seek to "float" the battery at a lower voltage to eek out a slightly higher efficiency and maintain the battery at a lower state of charge. As a result, they NEVER get fully charged. The only way to defeat this is put a significant load on the battery to force it to run a traditional float. Fortunately, it's as easy as turning on the headlights with the older Hondas.

I've seen this on other models, and it wouldn't surprise me if Jeep is doing the same thing, particularly when implementing other "safety" features.

EDIT: The first post in that Jeep forum with the 12.7-12.8V running voltage pretty much confirms they're doing the same.

If you still have the port, consider:

https://www.amazon.com/LIHAN-Charger-Display-Voltage-Compatible/dp/B01JA627KU

You can watch what your battery does.

You disagree with splitting my solar panel into two charge controllers. At least on this we have something to work with, maybe.

Could you "meet me in the middle" and propose a situation where a single charge controller energizes the aforementioned RELion 20 amp LiFePO4 LT (low temperature) battery, which in turn both energizes my 4.5W drawing dash camera, AND trickle charges--with hardware you suggest (I honestly don't know--a DC to DC converter???) --off of this RELion battery, the vehicle's batteries, as along as the engine is not cranked (so as to not interfere with the smart charging aspects of the vehicle design and trickle charge the vehicle batteries at the same time that the alternator is feeding them?)

I'm not the only one who disagrees with you. Putting one panel on two charge controllers is not done. Charge controllers and batteries will fight over the panel, and you won't get the performance you should.

You want something that's backwards from typical. Nothing I can propose has the anticipated reliability and favorable outcome as the simplified system I've already proposed.

The only thing that's close is rather than divide the 100W panel between the two controllers, get two smaller panels and put one on each controller. 50W is 2X what you need for each system provided you get decent sun on a given day.

50W panel -----> charge controller -----> starter battery
50W panel -----> charge controller -----> LFP battery ----->dash cam

Please appreciate I am not stubborn, obstinate defiant, overconfident, trolling, or narcissistic. Rather I am caught between two worlds with different battery philosophies. If you have no answer that's fine. If you feel it indicated to reply to the effect of having no suggestions within the model I've laid out for myself that's fair too. Maybe you feel that only a separate solar panel dedicated to trickle charging the vehicle's batteries is my only play within the framework I've established for myself.

But please, don't throw flame--I'm already getting that from the Wrangler forum side of things.

I disagree in part. You're stubborn, but I respect that. I clearly am too.

 

[Arbee]

Snoobler: in an effort to come to a compromise that doesn't go against all your justifiable best practices when it comes to things solar, and my desire to avoid tapping my vehicle's "under the hood" (your parlance I think: starter) batteries, at least for the time being, unless the engine is cranked and the alternator is feeding them, I was wondering what you think of the following compromise:

I have found two products that perhaps neither of us would oppose, if not think ideal.

You are in the "use solar to charge vehicle batteries, and run appliances like my 4.5W dash camera off of them," school of thought (at least as my vehicle is NOT an RV with a "house" battery is concerned) if I've characterized you correctly.

I am in the "I want to avoid running any appliances off of vehicle batteries when the vehicle is parked, tapping solar power to a dedicated battery to run that appliance---and hey, it would be nice ("when in Rome") to also tap that solar panel to trickle charge the very temperamental vehicle batteries I seek to feed, not feed off of when the vehicle is parked."

(Of course that doesn't mean I don't occasionally turn the vehicle radio on when working on the vehicle parked in my driveway: if you catch my drift. I'm cautious, not nuts.)

That said, what are your thoughts about either of these products being my sole controller--seeing the "two controllers off of one solar panel route" NOT being, as you raise, a solar best practice:

https://www.amazon.com/Go-Power-GP-...1&keywords=GP-PWM-30-UL&qid=1608655624&sr=8-3 (specs are here https://gpelectric.com/products/30-amp-solar-controller-bluetooth/

OR

https://www.renogy.com/dcc30s-12v-30a-dual-input-dc-dc-on-board-battery-charger-with-mppt/

I'm figuring that my 100W solar panel is more than capable of charging my Renogy 20 amp LiFePO4 LT (low temperature) battery, (purposed with energizing the dash camera when the vehcile is parked, day or night) even factoring the additional energy this battery pulls to initially warm itself when cold, prior to accepting charge, and that excess solar capacity during daylight is diverted to trickle charging the vehicle's batteries.

If I take the Go Power controller route I can easily hook up a relay that prevents the controller from trickle charging the vehicle's batteries while the engine is cranked and the vehicle's smart alternator effects this charging task: not confused by the external charge the Go Power might provide while the vehicle is cranked.

Slightly more expensive, the Renogy implementation provides hookups to not only let the controller know to not feed the vehicle's batteries with energy while the vehicle is cranked, but actually allow the vehicle's alternator to charge the LiFePO4 battery as well.

If this becomes a hot mess then either controller can make its primary (and only) battery the two batteries under the hood, and I can run the dash camera off of the vehicle's batteries as you have urged all along. The downside (maybe?) I overspent on controllers and didn't replace the vehicle batteries out of pocket after only 2 years of ownership.

I would love a less problematic electrical power plant in my vehicle and to do things only your way. I am not suggesting this hybrid model to in any way antagonize you and I appreciate your thoughts and time.

Thank you.

 

[snoobler]

(Of course that doesn't mean I don't occasionally turn the vehicle radio on when working on the vehicle parked in my driveway: if you catch my drift. I'm cautious, not nuts.)

IMHO, you should never do this. I don't. I've taken too many calls from folks needing jumps because they sat in a parking lot for 20 minutes playing music and can't start their cars. Most folks have devices that play audio and most radio stations have a means of online access of their content. I stream to my phone and play through headphones. No need to pollute my neighbor's ears with my choice of audio entertainment.

That said, what are your thoughts about either of these products being my sole controller--seeing the "two controllers off of one solar panel route" NOT being, as you raise, a solar best practice:

https://www.amazon.com/Go-Power-GP-...1&keywords=GP-PWM-30-UL&qid=1608655624&sr=8-3 (specs are here https://gpelectric.com/products/30-amp-solar-controller-bluetooth/

I don't care for their charge profiles since none are optimal for LFP. You don't want to float LFP at 14.0, so I'm not sure why they would specify 14.0V float. That can damage them. Given that this is a cyclic application with daily nightly discharges, MAYBE the 14.0V float on LFP doesn't matter.

AGM would be a better program for your LFP, BUT it has temperature compensation active, which is good for your AGM and bad for your LFP.

Thank you for linking that product. I don't recall ever seeing a single PV input charge controller with dual output. If the voltages were more optimal, it would be my first choice.

OR

https://www.renogy.com/dcc30s-12v-30a-dual-input-dc-dc-on-board-battery-charger-with-mppt/

I'm figuring that my 100W solar panel is more than capable of charging my Renogy 20 amp LiFePO4 LT (low temperature) battery, (purposed with energizing the dash camera when the vehcile is parked, day or night) even factoring the additional energy this battery pulls to initially warm itself when cold, prior to accepting charge, and that excess solar capacity during daylight is diverted to trickle charging the vehicle's batteries.

Given the heater requirement, being able to pull a higher current from the alternator, that would be very desirable.

"trickle" charging the starter batteries is kinda vague. I would assume it just makes an effort to float them at ~13.2V or so w/o any kind of bulk or absorption charge.

Summary:

1st option will likely result in getting both batteries fully charged unless the heater is required to warm the LFP. If the heater is not required, and there is good sun, very good chance that both batteries get fully charged via solar.

2nd option will certainly get the LFP battery fully charged, but it may fall short on maintaining the starter battery. It has the added advantage of providing a second option for charging the LFP in case you don't have solar.

I would build a small foam box to insulate the LFP to minimize the need for the heater.

I think both options will work. It's hard to say which will work better due to the uncertainties.

 

[Arbee]

Thanks for your thoughts. The "playing the vehicle radio while working on it while parked," is as much metaphor as reality: although I will keep your thoughts in mind when it comes to waiting for my wife at a parked destination. Volume cannot reach anyone but me. My parents trained me and lived by example to care about others, not just myself.

On my driveway, not only is the vehicle concurrently trickle charged, but alternate sources of entertainment independent of the vehicle and its batteries, if desired, is available, as is my battery jump starter--not that I recommend this "run down the vehicle's batteries and bring in the defibrillator" route. : - )

 

[Bill Taylor]

Interesting thread. I always enjoy listening to a couple of hardheads who can still have a reasonable discussion. ?
I will throw my two cents in. What voltmeter are you using to read the voltage on your batteries? Is it known to be accurate? And what voltage is the alternator charging the batteries up to when the engine is running? I can't begin to tell you how many hundreds of hours of my life I will never get back, having this exact same discussion with customers, who's voltmeter is off by a quarter of a volt. Good luck!

 

[cinergi]

Not knowing budget or whatnot, my personal design choice would be to replace the vehicle batteries with deep cycle batteries if they're not already and then make sure there dash cam shuts off at a preset voltage so you'll still have enough juice to start your car. It would be nice if the batteries were joined only during charging or starting so that you could designate one battery as an accessory battery. Then you don't have to worry about heating LFP (it's true you shouldn't put Lead Acid or AGM inside the vehicle .. although sealed lead acid might be an option).

What about running the dash through its own battery like this product (I'm not making a recommendation for this product or its insane price tag): https://www.amazon.com/Cellink-Battery-Supplies-Dashboard-Camera/dp/B06ZZ4W66R/

And connect it to a power source (for charging) that's only live when the car is running.