diy solar

diy solar

Purpose of starter wire in a DC to DC controller

A

Arbee

New Member
Joined
Dec 16, 2020
Messages
176
I'm sure this has come up before. I'm new, including to this forum, and with my search skills limited I couldn't find the answer I strongly suspect is out there, much that I tried.

As many of you I'm sure know, DC to DC solar charge controllers, likes one from Renogy, that charge both a house and starter battery feature the ability, via a wire, to know when a vehicle's engine is cranked, so as to not trickle charge the starter battery during times when the engine is on.

Why is using the solar panel to charge the starter battery at the same time that the engine is on and the vehicle's alternator is doing so as well a bad thing?

Thank you.
 
Oh, and would it be okay if this starter wire....which I think is so that the solar panel doesn't trick smart vehcile alternators, be connected to a cigarette lighter plug that is only energized when the vehicle is cranked?
 
Because it doesn't work like that. The two batteries aren't joined, nor does the charger charge both batteries. The charger only charges the coach battery by using the starter battery/alternator as source and charging the coach battery.

If the engine is on, the alternator is running, so there is no need to trickle at all. The starter battery is fully charged almost immediately.
 
snoobler said:
Because it doesn't work like that. The two batteries aren't joined, nor does the charger charge both batteries. The charger only charges the coach battery by using the starter battery/alternator as source and charging the coach battery.

If the engine is on, the alternator is running, so there is no need to trickle at all. The starter battery is fully charged almost immediately.
Click to expand...

Thank you sir/madam for your thoughts. Here is a link to the device in question: https://www.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

I am a bit confused as to your claim that the (solar?) charger (as opposed to the vehicle's alternator) does not charge both batteries. And when you say the coach battery I am assuming that that is the battery that energizes RV appliances, while the starter battery, under the vehicle hood, the starter solenoid.

I say this because on this link I provide it mentions that it will trickle charge the starting battery via solar panels if the service battery is fully charged. Maybe I am misunderstanding you.

I think the wire from the engine--if I get you correctly--when energized--tells the linked product to not charge the starter battery anymore as the alternator can/will do that. But is that because with smart alternators these days we don't want to confuse it as to how much power the starter battery actually has by adding to the equation the power from the solar panel?

By all means explain this to me like a 3 year old. That's about my solar acumen. My goal is to charge a Lithium Iron Phosphate (LiFePO4) battery in my Jeep Wrangler vabin, whose sole purpose is to energize a 4.5 dash camera in parking mode when the engine is off, AND trickle charge the starter battery when I'm away from home and can't plug in my A/C trickle charger.

When the vehicle is cranked, the dash camera is powered by the vehcile's starting battery.

Originally the dash camera ran off the starter battery with a 12.3V cutoff in winter to preserve the starter battery. I am hoping that using instead the less voltage drop/temperature drop sensitive LiFePO4 battery to energize the dash camera in parking mode that the camera won't shut off at night, like its been doing when the car battery's voltage (an AGM battery) drops with cold temperatures, below the cutoff voltage I set for the dash camera at 12.3V.

Thanks.
 
The Renogy dc2dc is built for vehicle charging the house battery. Ignition signal means it won't steal from the starter to feed the house, it will only charge when the alternator is running.

I don't know if you want to use it in place of a solar charge controller and it might be weird or bad to hook the solar to the vehicle side at the same time the vehicle is.
 
It wasn't clear you were referring specifically to the feature of trickling AFTER the coach battery is full.

The signal "wire" is only for smart alternators. Non-smart alternators charge start/stop on the basis of voltage as linked in the other thread. I've frankly never seen a "smart" alternator, but my newest car is an '09.

The renogy product does not charge the starter battery. It charges the camera battery. It pulls from the starter battery system (battery + alternator) to provide charge current to the camera battery. When both batteries are full, and the voltages are above the thresholds in the manual, the solar will float both. This has no meaning when the engine is running as you can't pour more water into a glass than it can hold. The solar panel makes negligible contribution to the starter battery besides floating it with solar.
 
Thanks wmills. My vehicle is rarely cranked during COVID... it's on a 3 amp shore powered trickle charger right now.

I want to be able to run my dash camera when the vehicle is parked 24/7. Even now, with this trickle charger attached, sometimes when it gets cold out my vehicle's AGM battery can drop below 12.3V--the cutoff I set to turn off the dash camera to preserve the cranking battery.

When the vehicle is cranked I am fine for this dash camera to get its power from the starter battery as it currently does.

The goal (so confused) is to use a 100W solar panel on my roof rack to run the dash camera at all times in parking mode (rather than have that dash camera run in parking mode off the starter battery) and trickle charge the vehicle's started battery--at least during daylight. I may be out on the road and not have access to A/C power to trickle charge the starter battery.

I thought of using a LiFePO4 battery to run the dash camera in parking mode, thinking it less susceptible to voltage drops with temperature drops but I hear that below 32 degrees you can damage a LiFePO4 battery.

The dash camera uses 4.5W.

So lost...any suggestions I am all ears!! : - )

Thanks.
 
Ok, i read the link. Dual dc input is kinda sweet. So then yes the ignition wire prevents stealing from the starter and the solar probably works any time. That unit is probably smart enough to use solar first and fill in from the alternator if say your max charging amps is like 50 and its getting 20 from solar and so it would pull 30 from the engine.
 
Hi snoobler. I was only making reference to that feature of trickle charging AFTER the coach battery is full because I was confused between what you said and the product I was referring to can do.

Ideally, I just want, as I'm sure I've said (sorry) to use a 100W solar panel to make sure I can run a dash camera at all times when the vehicle is parked, and trickle charge my starter battery.

Maybe, like you said elsewhere, the solar panel can keep my starter battery above the 12.3V cutoff of the dash camera even on cold days where my current 3 amp shore power trickle charger cannot.

Maybe I need a heating system for a LiFePO4 battery as I drift further into the weeds of complexity!!! (lol)

I would love to have the solar panel just charge the starter battery and have the dash camera (4.5W) run off the starter battery at all times, parked or engine cranked. I just get the idea that in the cold that AGM starter battery isn't going to register, when parked, above 12.3V, and the dash camera, set to shut off at 12.3V to preserve the cranking battery will shut down.

Thanks.
 
Your "interesting" ideas are making more sense now. If this is happening with the trickle charger attached, you need a new 12V battery, or your trickle charger is junk. Here's why:

A proper "trickle charger" should "float" the battery at a voltage around 13.2V at 25°C. Period. If it's colder, it should float HIGHER, about 0.03V/°C and LOWER by the same amount in heat. If it's freezing outside, it should float at 13.95V.

12V/4.5W = 2.7A
Your car probably consumes another .05A maintaining the memories of the various system.

So, your overnight draw is 2.75A. This is below your trickle charger's 3A limit.

There is no way your voltage is dropping to 12.3V if the trickle charger is working and your battery is healthy.
 
Look at the forums for battery warmer stuff. If it's cold then keeping above 32f is better for either type of battery.

That said the post above about your charger or battery being a problem sounds right.
 
snoobler said:
Your "interesting" ideas are making more sense now. If this is happening with the trickle charger attached, you need a new 12V battery, or your trickle charger is junk. Here's why:

A proper "trickle charger" should "float" the battery at a voltage around 13.2V at 25°C. Period. If it's colder, it should float HIGHER, about 0.03V/°C and LOWER by the same amount in heat. If it's freezing outside, it should float at 13.95V.

12V/4.5W = 2.7A
Your car probably consumes another .05A maintaining the memories of the various system.

So, your overnight draw is 2.75A. This is below your trickle charger's 3A limit.

There is no way your voltage is dropping to 12.3V if the trickle charger is working and your battery is healthy.
Click to expand...

I hear that. The trickle charger is a 3amp from Battery Tender by Deltran--it has no temperature gauge. I'd think they know their stuff. The vehicle battery (actually there are 2 hooked up in parallel when, among other times the vehicle is parked---the second battery is for the engine start stop (ESS) system (2018 Wrangler JL--engine shuts down at traffic lights to save gas) Chrysler tells me both batteries are fine.

Funny, the ESS wouldn't engage as a safety mechanism UNTIL I put the trickle charger on the vehicle--something I did before COVID but glad I have now especially in light of the vehicle's infrequent use because of COVID.

I hear you sir. You're saying, "the problem is your starter battery son." Message received. : - )

Maybe I need a temperature aware solar charge controller to get that starter battery up to snuff to run the dash camera--keeping that starter battery above 12.3V, and trickle charge the battery. Might that be an approach?
 
Battery Tender is mostly hype. Basically, they do just well enough to notably improve life of a battery vs. someone who never does anything. That creates the illusion of expertise. Their hands are tied in reality. Since all batteries are made a little different, charge voltages are a little different, so they pick something that won't hurt batteries and cause them to age out faster, but they don't pick something optimal as they don't want to get too close to that line and risk ruining a battery that's slightly off the beaten path.

If someone was to maintain their battery according to the manufacturer's recommendations, they would last a lot longer than with a battery tender, but nobody (including me) wants to invest that many hours of life to save $200.

If you're now saying you have 2 batteries in parallel, this is mind boggling.

According to batteries plus:

Duracell Ultra Platinum AGM Battery for 2018 Jeep Wrangler V6 3.6L 650CCA Car and Truck - SLI48AGM at Batteries Plus Bulbs

Duracell Ultra Gold group 48 replacement battery designed for low maintenance and dependable engine starting power. Perfect replacement battery for Ford, Volvo, Mercedes and more
www.batteriesplus.com www.batteriesplus.com

A 2018 Wrangler has 70Ah AGM batteries. I can't isolate the SJ specifically.

ONE of those batteries could power your camera for 70/2.7 = 26hr before completely dead. TWO could do it for the same amount of time and easily stay above the 12.3V cut-off WITHOUT a trickle charger attached.

Consider that since you're likely under the typical 3 year/36K mile warranty covering new batteries, your batteries will absolutely, positively be good according to the dealer until they leave you stranded somewhere.

Go for a morning drive, put the trickle charge on for several hours, pull one and take it to AutoZone/O'reily and have them run a test on it. Ask them specifically for the tested CCA, the State of Health and the resistance.
 
snoobler said:
Battery Tender is mostly hype. Basically, they do just well enough to notably improve life of a battery vs. someone who never does anything. That creates the illusion of expertise. Their hands are tied in reality. Since all batteries are made a little different, charge voltages are a little different, so they pick something that won't hurt batteries and cause them to age out faster, but they don't pick something optimal as they don't want to get too close to that line and risk ruining a battery that's slightly off the beaten path.

If someone was to maintain their battery according to the manufacturer's recommendations, they would last a lot longer than with a battery tender, but nobody (including me) wants to invest that many hours of life to save $200.

If you're now saying you have 2 batteries in parallel, this is mind boggling.

According to batteries plus:

Duracell Ultra Platinum AGM Battery for 2018 Jeep Wrangler V6 3.6L 650CCA Car and Truck - SLI48AGM at Batteries Plus Bulbs

Duracell Ultra Gold group 48 replacement battery designed for low maintenance and dependable engine starting power. Perfect replacement battery for Ford, Volvo, Mercedes and more
www.batteriesplus.com www.batteriesplus.com

A 2018 Wrangler has 70Ah AGM batteries. I can't isolate the SJ specifically.

ONE of those batteries could power your camera for 70/2.7 = 26hr before completely dead. TWO could do it for the same amount of time and easily stay above the 12.3V cut-off WITHOUT a trickle charger attached.

Consider that since you're likely under the typical 3 year/36K mile warranty covering new batteries, your batteries will absolutely, positively be good according to the dealer until they leave you stranded somewhere.

Go for a morning drive, put the trickle charge on for several hours, pull one and take it to AutoZone/O'reily and have them run a test on it. Ask them specifically for the tested CCA, the State of Health and the resistance.
Click to expand...
The 3.6L JL which I own has a main 65 Ah battery and an smaller 12 Ah one, both AGM. They are connected in parallel 99.9% of the time but for an instant at startup when the smaller one is tested in isolation (long story via factory design) and during Engine Start Stop (ESS) events when the smaller one runs the show.

Will do on the CCA tests of each...what are suppose to be 600 CCA and 200 CCA respectively. : - )
 
Okay. Even so, 65Ah is enough that you shouldn't need a trickle charger overnight.
 
well....the vehicle isn't being used much and the dash camera is....so there's that : - )
 
BUT... if your battery tender is actually doing what it's supposed to do, a healthy battery shouldn't drop to 12.3V. If your batteries are in bad shape, they may be losing more charge than the battery tender can supply... or ... battery tender broke.
 
Test the accross the terminal battery voltage when the charger is disconnected. Then test with the charger on. I think you will find the trickle charger isn't.
 
Arbee said:
Maybe I need a temperature aware solar charge controller to get that starter battery up to snuff to run the dash camera--keeping that starter battery above 12.3V, and trickle charge the battery. Might that be an approach?
Click to expand...
Why not fit a temperature compensated battery charger from a company like Victron who supply well designed product, with a charge profile suitable for AGM batteries
One of the features is a change to maintenance mode once it regards the battery as 'full'. This avoids the damage caused by leaving the battery continually at high float values.

If you are fitting a 100 watt panel just to maintain the engine battery, then connect to the engine battery, again using a temperature compensated solar controller with AGM charge profile. The practical aspects of fitting a 100 watt panel to your vehicle may be as issue.

Since the vehicle has a smart alternator with computer controlled engine charging, adding external charging may confuse the system, the drivers handbook may offer guidance.

Mike
 
You must log in or register to reply here.

Similar threads

L
Which DC to DC converter to use?
Replies
7
Views
390
time2roll
T
A
Smart Alternator Question
Replies
3
Views
227
mikefitz
mikefitz
T
LiFePO4 'Starter' Batteries ???
2
Replies
24
Views
767
patrickparrott
patrickparrott
xavpil
Battery not getting charged
Replies
1
Views
123
MTM98290
MTM98290
A
Smart alternator alternative
Replies
1
Views
179
Rednecktek
Rednecktek
Back
Top