Can you explain the use of battery isolators and automatic charge relays in a 2-battery bank system and explain why a DC-DC is advantageous?

Isolators “isolate” the starter and house batteries and have a VSR to ensure no draining of the starter battery. The isolator diverts energy to your house battery only when the vehicle battery is at an adequate voltage. However, they are considered dumb chargers and not multi-stage charging potentially reducing battery life. 

 ACRs and VSRs are also “dumb” chargers in that they don’t provide your batteries with the specific voltage at the specific times that they need for longer life. Either a dumb ACR or VSR won’t deliver the specific voltage over the various periods of the charging cycle. 

 DC-DC Battery to battery (B2B) solves the problem so far unaddressed: delivering electricity in a special way (voltage specific over time) to your batteries. B2B chargers are “smart” chargers. Using a smart charger means that battery life is prolonged. We recommend DC to DC chargers over isolators because they protect the vehicle’s alternator and maximize the battery’s lifespan. DC to DC chargers provide a multi-stage charge to the house battery and push more charge current than an isolator.

Would you please explain what a DC/DC charger is and how it works?

DC-DC are used in 2 x battery systems where the starter battery charges the house battery to 100% in vehicles or boats. They take the voltage and current of the input and transform it to a usable voltage/current for the output. Depending on the specifications, the DC-DC may power limit or power increase to output the correct voltage. The DC-DC make it easy to get just the right amount of DC voltage for 3-stage/4-stage battery charging logic and continuing to adjust the voltage based on the battery state.

What fuse size would I need for my DC-DC charger?

You can refer to the following table below for recommended fuse sizes based on DC-DC charger type, cable type and cable length:

 Is the BT-1 compatible with the DCC50S? If not, is there another monitor?

The BT-1 is NOT compatible with the DCC50S. However,  the BT-2 is compatible with the DCC50S, as it has an RS485 port. You can connect to the BT-2 Module by using the Renogy DC Home App available on IOS and Google PLay Store only. 

Is my battery compatible with your 20A, 40A, or 60A DC-DC Model? Which do I choose?

To determine compatibility, you have to look at the battery's maximum charging current specification. A single Renogy 100Ah AGM battery has a max charge current of 30A so it would NOT be compatible with the 40A DC-DC, however, it would be compatible with the 20A DC-DC. 

Can I connect my Renogy 100AH AGM battery with a 40A DC-DC battery charger?

A 100AH AGM  battery has a maximum charge input of 30A, so using a 40A DC-DC battery charger would be too high. However, if connecting more than one battery like these in parallel, say 2 for example, the charge current increases from 30A to 60A and now you can use the 40A DC-DC or even upgrade to the 60A DC-DC.

How do I set my dip switches on a 40A DC-DC charger?

To get started you have to determine whether your 12V battery is Lithium or Non Lithium as well as know the charging voltage. This is found in the manufacturer's specification. Start with SW5 ~ Turn ON if your battery is Non-Lithium, or Turn OFF if your battery is Lithium. 

Non-Lithium have a Boost Voltage and Float Voltage while Lithium Batteries only have a Charging Voltage and No Float. If SW5=ON then set SW1/SW2 to determine the Boost Voltage and SW3/SW4 determines the Float Voltage based on this chart. 

 If SW5=OFF then you must set SW3/SW4 to ON, and then use SW1/SW2 to determine the Charging Voltage based on this chart. 


How can you determine the size of the DC-DC charger you would need?

To determine compatibility, you have to look at the battery's maximum charging current specification. A single battery might have a max charge current of 40A so it would NOT be compatible with the 60A DC-DC, and only compatible with the 20A or 40A. 

Can you have different battery types connected on a DC-DC charger?

Yes. Your starter and house batteries may be different. You are primarily charging and setting the type for the house battery.

 What are the specifications of DC-DC terminal screws?

The screw specifications of the input and output terminals are: M8*10mm

What is the function of DC-DC DIP switch?

The DIP switch control the battery type setting, the battery charge setting, and the battery float stage if applicable. 

How to restore the factory settings of DC-DC?

You can reset the DIP switches to their factory position be turning them all ON.


During the use of DC-DC, how do you determine its working status?

According to the DCC indicator, during normal operation, the power light is always green and the fault light is not red.

What is the nominal voltage of input and output during the use of DC-DC?

Only 12V nominal voltage may be used with the DC-DC. 

When DC-DC is in use, what happens if the positive and negative poles of the are reversed at the input or at the output, is there a difference?

When the input battery terminals are reversely connected, the built-in fuse blows and will not allow the DC-DC to turn on anymore; when the output battery terminal is reversely connected, the DC-DC will shutdownthe relay will stop operating, and a red fault light will turn on.

Which temperature sensor do I use for my DC-DC Charger?

Only use the DCDC Temperature Sensor (Model: RTSDCC) as it has an RJ12 head interface. 

Are there any requirements for the DC-DC installation environment?

The waterproof and dustproof level of DCC is low, IP32. The installation environment requires dry and ventilated areas.

Can a DC-DC charger ever deplete a battery?

The DCDC use a voltage start relay connected into the ignition circuit so the DCDC only starts when the vehicle alternator is charging the starter battery so it will only operate while driving and not drain your battery. Incorrect placement of the D+ wire may lead to a depleted battery. Check out “Connecting the D+ Article for more information”. 

DC-DC is connected to the input and D+ signal lines, but not to the output. Will there be voltage at the output?

When the input and D+ signal lines are connected, and the output is not connected, the output terminal has voltage. The voltage parameter is the boosted voltage point voltage set by DC-DC at this time.

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