New DC to DC Charger From Renogy-20 amps or 40 amps-Flooded/AGM/GEL/Lithium

[Hillbilly Heaven]

Can anyone recommend an appropriate relay that would send signal to converter when car/alt is running and voltage is higher?

The big idea here was to have everything self contained in an battery box, so that It could move car to car.

If practical, would have a 12v power input from alternators/starter battery into battery box, then into voltage relay to turn on,and then through converter to battery. That make sense?

I’m new at this and have built a Pelican 1600 box with 100Ah AGM, AC battery charger, solar controller (w/200W solar), and 12v outputs to fridge and other uses. Will also add an inverter. It works great so far.
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Any pics of your case setup? Sounds like something I may want to do as well.

 

[AlumniCU]

Any pics of your case setup? Sounds like something I may want to do as well.

On right side bottom, input for AC extension cord to charger, above that ARB fridge socket. On side of box is connector for MC4 to solar panels. Haven’t installed venting yet.



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[john61ct]

You don't need a relay, just a switch and voltage that meets the unit's specs,

a voltage-sensing controller would trigger the charger, in the same way it would close a relay - contactor is a more precise term.

Check out the manual for the switching specs.

 

[john61ct]

Can't say for sure, but there are five variables, if you can get a detailed answer out of them, please post it publicly.

it is Normally Open for sure

Most likely Positive side

Likely in a range centered on nominal 12V range, ideally something like 3-30V

and some range for available current, ideally from very tiny up to reasonably high.

Finally, self consumption to hold it Closed hopefully very low.

 

[continuecrushing]

Can anyone recommend an appropriate relay that would send signal to converter when car/alt is running and voltage is higher?

The big idea here was to have everything self contained in an battery box, so that It could move car to car.

If practical, would have a 12v power input from alternators/starter battery into battery box, then into voltage relay to turn on,and then through converter to battery. That make sense?
...

Do you have a line going to the back already? I was thinking you could use existing wiring back there if it starts/turns off with the vehicle. That way it automatically turns "off" the charger when you're not driving.

I'm looking into voltage specific on/off relays right now. This would do exactly what you described-always have a "hot" wire in the back, but depending on the voltage it turns on/off the charger.

 

[Hillbilly Heaven]

Here is a simple VSR that activates when voltage is 13.4 volts and above and deactivates at 12.8 volts. Deactivation maybe a little low for resting starter battery voltage but would save from draining starter battery.
Consumption at 5ma.
https://www.hella.co.nz/en/products...lays/voltage-sensitive-relay-relay-1224v.html

Don't know if someone like Victron, Sterling. or Blue Sea has something similar.

 

[Hillbilly Heaven]

Here is a Redarc that is adjustable energize point with a (set point - 0.7) volt de-energize point.
https://www.redarc.com.au/voltage-sensor-12v

 

[continuecrushing]

Here is a simple VSR that activates when voltage is 13.4 volts and above and deactivates at 12.8 volts. Deactivation maybe a little low for resting starter battery voltage but would save from draining starter battery.
Consumption at 5ma.
https://www.hella.co.nz/en/products...lays/voltage-sensitive-relay-relay-1224v.html

Don't know if someone like Victron, Sterling. or Blue Sea has something similar.

This is perfect. Too bad I can't find it anywhere lol. Closest thing I can find is the 30ish dollar relay used for charging batteries, which would work-but there must be something cheaper (plus we just need it as a trigger, we don't need high amperage). But it would work.

 

[baltik]

Doesn't look like there is a way to get this DC/DC converter to output a constant current in the desired 13.8-14 range and then have it shut off. Is Sterling the only unit that does that? I hate paying for all that extra complexity in dollars as well as size....

 

[spikemd]

Based on readings from Redarc, 20A might not be enough for 100ah battery. I would go with 40A. I will be buying DC to DC charger wih Redarc or Ctek being competitors but more expensive. What I like about Redarc is integrated solar MPPT so everything plugs into one unit. I will be running 2, possibly 3 yellow tops.

 

[john61ct]

Optima doesn't make proper deep cycling batts anymore.

If in NA market, look for Lifeline, Odyssey or Northstar, if you really need sealed / AGM.

The amps rate will be fine for FLA but yes AGM likes higher.

Getting a dedicated SC will extract better efficiency from your panels.

Sterling makes great DCDC units, BB series offers user-custom setpoints.

 

[AlumniCU]

Just an update - have this now installed in my battery box in the back of the 4Runner. Seems to work well, but the 100Ah AGM battery has been pretty much full so it hasn’t had to work too hard.






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[continuecrushing]

Just an update - have this now installed in my battery box in the back of the 4Runner. Seems to work well, but the 100Ah AGM battery has been pretty much full so it hasn’t had to work too hard.

Nice! Do you have a plug in the back that's OEM, or did you run your own wiring?

 

[AlumniCU]

Nice! Do you have a plug in the back that's OEM, or did you run your own wiring?

Ran my own wiring. Tapped 12V ACC line in rear to signal unit on.


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[RigidYota]

Ran my own wiring. Tapped 12V ACC line in rear to signal unit on.


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On the fence to grab this, was install as straight forward as it looks? Did you get the 40amp one? What kind of charge rates are you getting? I have a 100ah battery charging via cigarette plug power (7amps) and its slow as hell and inconsistent.