Renogy DC-DC Battery Charger D+ connection.

[maJer]

I am converting my boat to AGM Start/ AGM House to AGM Start/LiFePo House.
I intend to set it up the following way:
I have a 55 A alternator and 100W Solar Panel charging the AGM Starting battery.

I have 4 - 100W solar panels charging a 300 AH Lithium house battery.

I plan on using the Renogy 20A DC-DC battery charger to allow the alternator and solar to charge the Lithium while underway and at anchor.

I want to know if I could use a Blue Sea Systems ACR to activate the Renogy DC-DC battery charger instead of connecting it to my ignition circuit?

My connections are as follows:
Alternator to the AGM battery and Solar to the AGM battery.
AGM Battery to the ACR and ACR to the D+ terminal on the Renogy DC-DC chargery.
AGM battery to DC-DC charger input side and connect the output of the DC-DC charger to the Lithium house bank.

The reason for this is that if I use the ignition circuit, then the solar will not charge the house bank unless the engine is on.

Is this safe?

Below are the links to the ACR and DC-DC Charger I am using:

https://www.bluesea.com/products/761...12_24V_DC_120A


https://www.renogy.com/12v-20a-dc-to...ttery-charger/

[newhaul]

Originally Posted by maJer

I am converting my boat to AGM Start/ AGM House to AGM Start/LiFePo House.
I intend to set it up the following way:
I have a 55 A alternator and 100W Solar Panel charging the AGM Starting battery.

I have 4 - 100W solar panels charging a 300 AH Lithium house battery.

I plan on using the Renogy 20A DC-DC battery charger to allow the alternator and solar to charge the Lithium while underway and at anchor.

I want to know if I could use a Blue Sea Systems ACR to activate the Renogy DC-DC battery charger instead of connecting it to my ignition circuit?

My connections are as follows:
Alternator to the AGM battery and Solar to the AGM battery.
AGM Battery to the ACR and ACR to the D+ terminal on the Renogy DC-DC chargery.
AGM battery to DC-DC charger input side and connect the output of the DC-DC charger to the Lithium house bank.

The reason for this is that if I use the ignition circuit, then the solar will not charge the house bank unless the engine is on.

Is this safe?

Below are the links to the ACR and DC-DC Charger I am using:

https://www.bluesea.com/products/761...12_24V_DC_120A


https://www.renogy.com/12v-20a-dc-to...ttery-charger/

Why not just hook the solar controller direct to the LiFePo4 . As to the renogy 20 amp dc dc just hook it up according to the instal instructions no need to spend extra cash and over compllicate the setup

[maJer]

That was my initial thought, but I really want solar to keep my starting battery charged since we are not at the boat for up to 4 months at a time.

I already have the ACR on hand, since it was used for my previous set up.

[motion30]

If it were me I would hook the solar directly to the lithium batteries. Maybe source is small 50 watt solar panel. To the Start batteries

[newhaul]

Originally Posted by maJer

That was my initial thought, but I really want solar to keep my starting battery charged since we are not at the boat for up to 4 months at a time.

I already have the ACR on hand, since it was used for my previous set up.

How much solar do you have and what controllers?

[wholybee]

I understand what you want to do. I would start out just connecting it to the ignition switch as the manual describes. I have the 60A version and just connected it to the ignition switch, but also through an on/off switch that is normally off unless I need the charging.

The reason I say do it this way is because even though the manual doesn't mention it, it seems to also require a certain voltage on the start battery side to turn on- at least the bigger 60A version seems to. So, I would test it and see what it does first.

You could use the ACR, but would need to be careful how you connect it. It might work better to use a relay output from a BMV meter in series with the ignition switch to check the voltage of the start battery.

[wholybee]

Another idea. Instead of hooking the D+ wire to the ACR, connect the D+ wire as normal. Then connect the ACR between the start battery and the DCDC charger.

[maJer]

Originally Posted by newhaul

How much solar do you have and what controllers?

I have 500W solar total. 400W is connected to the lithium through a renogy 30A MPPT.
I want to connect the last 100W to the AGM. I have a 6A PWM that I have left over for that. I may upgrade to a small MPPT though.

[newhaul]

Originally Posted by maJer

I have 500W solar total. 400W is connected to the lithium through a renogy 30A MPPT.
I want to connect the last 100W to the AGM. I have a 6A PWM that I have left over for that. I may upgrade to a small MPPT though.

If the pwm can be set to properly charge and maintain the AGM use it all good wouldn't change a thing wrt the solar mix other than that.
Sounds like you already have it all figured out. Just install the dc dc unit by the directions.
And your good to go .

[NorthCoastJoe]

My thought is that for a maintenance charger 100 watts is massive overkill.
A small 5 watt panel should be good enough for the start battery.

Even something like this would work.
https://www.harborfreight.com/15-wat...ner-64251.html

I have used those on my tractors and generator at home for years.

[newhaul]

Originally Posted by NorthCoastJoe

My thought is that for a maintenance charger 100 watts is massive overkill.
A small 5 watt panel should be good enough for the start battery.

Even something like this would work.
https://www.harborfreight.com/15-wat...ner-64251.html

I have used those on my tractors and generator at home for years.

Your home equipment uses a much smaller battery than a 250ah AGM that harbor freight unit is to small to even keep up with self discharge .

He has the 100 watt and the controller so it's his best option for now .

[newhaul]

Originally Posted by NorthCoastJoe

My thought is that for a maintenance charger 100 watts is massive overkill.
A small 5 watt panel should be good enough for the start battery.

Even something like this would work.
https://www.harborfreight.com/15-wat...ner-64251.html

I have used those on my tractors and generator at home for years.

Will it do the job without causing issues with the battery? No then it's not overkill.

[smac999]

Get a victron Orion smart instead. You can program it based on input voltage like how an acr does. No extra wires or parts.

The acr will not work it needs power on both sides to turn on. Some of the bep vsrs are only one sided and would probably work.

[maJer]

smac999,

Yep Since the ACR is dual sensing I realized it would not work. Thanks for pointing me to the Victron Orion Smart.