There is no reason why it shouldnt work? its intended to take a DC input and put the DC Back out, Where the power comes from shouldn't matter. There is a review on the product where someone put in solar, and had it charge a lead acid battery.
Using a Solar Charged LFP to Charge a SUV Lead acid Starter Battery?
- Thread starter Ang429
- Start date
Parallel for shade ,
Van Life Solar Setup | Wire Solar Panels in Series vs Parallel
Solar panels perform best when configured in the most optimum way for your combination of panels. Not all wiring setups are the same. So how do you decide if you should wire your panels in series or in parallel?
mowgli-adventures.com
It looks like Parallel will give me the full 135W Where as Series will only give me 70W, so then I guess Parallel should work fine even though they are a different wattage.Parallel for shade ,
Van Life Solar Setup | Wire Solar Panels in Series vs Parallel
Solar panels perform best when configured in the most optimum way for your combination of panels. Not all wiring setups are the same. So how do you decide if you should wire your panels in series or in parallel?
I bow to the calculators superior knowledge , if you've put the figures in right it should be spot on
mikefitz
Solar Wizard
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The MPPT controller section will work, no problem, but for solar controller as a stand alone unit, are are better engineered products on the market.
Take a step back and look at your requirements.
1, 200 watt panel to charge a LFP battery.
2, LFP battery to maintain starter and power starter battery loads
3, Hood panel to charge starter battery.
Rather than trying to use less than ideal products consider each task separately.
1, use a quality solar charger rated for 15 or 20 amps,
2, fit a program able DC to DC converter between LFP battery and starter battery set to 13.4 volts output. This unit has a control input so could be disabled / enabled as required. Not realy necessary as 13.4 volts is an ideal long term maintaining voltage.
3 fit a solar controller for the hood panel to starter battery, could be any type including a low cost PWM.
Yes but it needs something to tell it to start and stop working. Normally this is voltage changes due to alternator increasing the starter battery volts.
The MPPT controller section will work, no problem, but for solar controller as a stand alone unit, are are better engineered products on the market.
Take a step back and look at your requirements.
1, 200 watt panel to charge a LFP battery.
2, LFP battery to maintain starter and power starter battery loads
3, Hood panel to charge starter battery.
Rather than trying to use less than ideal products consider each task separately.
1, use a quality solar charger rated for 15 or 20 amps,
2, fit a program able DC to DC converter between LFP battery and starter battery set to 13.4 volts output. This unit has a control input so could be disabled / enabled as required. Not realy necessary as 13.4 volts is an ideal long term maintaining voltage.
3 fit a solar controller for the hood panel to starter battery, could be any type including a low cost PWM.
starting battery.....
If you added loads like big lights , amplifier or camping stuff
remove them and put the loads on your HOUSE (Lithium)
Your SUV was designed to run just fine with the existing starting system.
UNLESS you let it sit for weeks/months . Then you need to add a solar maintainer just to replace the normal SUV power drain.
HOUSE battery now has all major loads... makes it so much easier to maintain,design and install .
use a DC-DC charger to connect Lithium to the lead acid if you want to charge Lithium from alternator
Limit the size of the DC-DC to what your alternator can happily handle, (30 or 40 amps)
Solar charger to the lithium will help keep it charged , if you are not driving every day or so.
If you want to add a emergency battery combiner... use jumper cables to send some power from HOUSE to the Starting
If you added loads like big lights , amplifier or camping stuff
remove them and put the loads on your HOUSE (Lithium)
Your SUV was designed to run just fine with the existing starting system.
UNLESS you let it sit for weeks/months . Then you need to add a solar maintainer just to replace the normal SUV power drain.
HOUSE battery now has all major loads... makes it so much easier to maintain,design and install .
use a DC-DC charger to connect Lithium to the lead acid if you want to charge Lithium from alternator
Limit the size of the DC-DC to what your alternator can happily handle, (30 or 40 amps)
Solar charger to the lithium will help keep it charged , if you are not driving every day or so.
If you want to add a emergency battery combiner... use jumper cables to send some power from HOUSE to the Starting
Vigo
Solar Addict
One simple way to do what you’re talking about is simply to use a large diode between the LFP and FLA. It will cause a .7v drop which means if your LFP ‘rests’ at around 13.2 to 13.4 it will automatically hold the FLA at 12.5-12.7v. Downside is if you charge the LFP to 14.6 it will simultaneously raise the FLA to 13.9 which is not damaging but will represent a small ‘drag’ on your LFP charging efforts.
Another cheap option is to use a <$20 ‘VSR’ or voltage sensing relay. Theyre typically used to have a starter battery system charge into a house battery system but then automatically isolate them from each other when the engine stops to prevent the house batt from draining the starter batt. In this case you could use it ‘backwards’ so that any time the LFP batt is above 13.3v it will connect to the lead acid and disconnect when the LFP drops to 12.8 (which is pretty low SOC). It still has a manual engagement wire (could be hooked to a switch or just put an alligator clip on it and ground it by hand, etc) so even if the lfp drops to 12.8 and disconnects, you could manually reengage it in case of needing it as a ‘booster pack’ to help start the truck if the starter battery is too drained to crank the truck.
Just some cheap thoughts. ?
Another cheap option is to use a <$20 ‘VSR’ or voltage sensing relay. Theyre typically used to have a starter battery system charge into a house battery system but then automatically isolate them from each other when the engine stops to prevent the house batt from draining the starter batt. In this case you could use it ‘backwards’ so that any time the LFP batt is above 13.3v it will connect to the lead acid and disconnect when the LFP drops to 12.8 (which is pretty low SOC). It still has a manual engagement wire (could be hooked to a switch or just put an alligator clip on it and ground it by hand, etc) so even if the lfp drops to 12.8 and disconnects, you could manually reengage it in case of needing it as a ‘booster pack’ to help start the truck if the starter battery is too drained to crank the truck.
Just some cheap thoughts. ?
Its not easier because Like i said its in the trunk, So it means a lot more wiring going through the car. If I do choose to go this Route though, it would be significantly Easier if I could just run the LFP Positive and Negative through to under the hood, and Connect everything to that under the hood rather than running multiple Lines back to the battery. Would I be able to Hook up Charging and Discharging all to these two cables under the hood?
Vigo
Solar Addict
You can ‘chassis ground’ your LFP so that you really only need one long wire for positive, with your negative lead being fairly short. If you think about stereo amplifier installs this is typically hows its done and in fact you could use a stereo amifier wiring kit for this if you wanted to. Just make sure its sized for whatever your max continuous amperage would be. If you have no intention of charging the LFP from your alternator or using the LFP as a ‘jump pack’ that doesnt require hooking regular old junper cables to it, you could honestly get by with a fairly small wire.
If you never planned to do more than 10amps or so you could even ‘backfeed’ through a rear 12v accessory charging port. Granted, some of them aren’t powered when the key is off, but you can probably fix that pretty easily in whatever fusebox contains the fuse for that circuit. An easy and reversible mod would be to simply add two ‘fuse taps’ with their wires hooked to each other. One would go into the spot where the 12v port’s fuse is and the other would go to some other spot which has power when the key is off (and preferably a larger fuse is already in it, or its an empty spot, indicating adding <10amps of current would not overheat the wiring). This would act like an ‘external jumper’ that didn’t require splicing and would make your rear power ports ‘always on’ and also able to be used to charge the start battery (at <10 amps).
If you never planned to do more than 10amps or so you could even ‘backfeed’ through a rear 12v accessory charging port. Granted, some of them aren’t powered when the key is off, but you can probably fix that pretty easily in whatever fusebox contains the fuse for that circuit. An easy and reversible mod would be to simply add two ‘fuse taps’ with their wires hooked to each other. One would go into the spot where the 12v port’s fuse is and the other would go to some other spot which has power when the key is off (and preferably a larger fuse is already in it, or its an empty spot, indicating adding <10amps of current would not overheat the wiring). This would act like an ‘external jumper’ that didn’t require splicing and would make your rear power ports ‘always on’ and also able to be used to charge the start battery (at <10 amps).
mikefitz
Solar Wizard
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What happens when the starter motor fires up?
Dagoth Ur Does Solar
Solar Enthusiast
Good lord that thing is expensive.
Isn't this just a wimpy buck converter with an inline fuse?
Vigo
Solar Addict
The LFP will share the starting load for the very brief time it takes to start the engine. This would consume single digit watt hours, so basically inconsequential in my opinion. If the wiring in between the LFP and lead acid were fairly small, it would reduce this even further while having no real effect on the LFP’s ability to hold the lead acid @ >75% SOC until the LFP itself were to drop below say 20% SOC.
A combination of a diode AND a $13-16 ‘vsr’ bypassing said diode would allow the LFP to hold the FLA near fully charged, assist in engine starting (if diode and wire were sized for it) AND allow the truck’s charging system to automatically charge the LFP (up to the mid-13s, anyway) only when the engine was running.
The reason i cant really recommend simply using a PWM charge controller between the two batteries is because it doesnt inherently prevent an engine-start scenario from over-currenting the SCC and blowing it. You’d have to implement your own circuit with a relay under the hood to isolate the two batts during engine cranking. The diode and VSR can be done directly at the LFP and even mounted to it, requiring no truck mods at all and ‘automating’ some basic functionality.
Ok so we are not talking about a stock vehicle with from the factory hazard lights and "bright lights". That changes things quite a bit.
No, These are additional Lights.
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