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DC to DC charger dip switch setting

Posted by baltik

Aug 8, 2019 at 8:57pm

I just installed a 40A DC to DC charger - my dip switch are as folows:
Up Down Down Down Up

which I would expect to put out a constant 14.4 Volts. However, I am measuring a 13.56 at the output terminals. Is it supposed to take a long time to hit the desired voltage? Are my dip switch settings wrong?


Posted by tattoo

Aug 9, 2019 at 5:22am

baltik Avatar

Aug 8, 2019 at 8:57pm baltik said:

I just installed a 40A DC to DC charger - my dip switch are as folows:
Up Down Down Down Up

which I would expect to put out a constant 14.4 Volts. However, I am measuring a 13.56 at the output terminals. Is it supposed to take a long time to hit the desired voltage? Are my dip switch settings wrong?



What was the voltage in the battery when you started? How long is a long time? A day a week an hour?

Posted by bupkis

Aug 9, 2019 at 5:24am

The 'constant' voltage mentioned is only one stage of the charging cycle.
This is explained in section 7.2 page 16
www.renogy.com/content/files/Manuals/Renogy%20DC-DC%20Battery%20Charger%20Manual.pdf

Posted by russ

Aug 10, 2019 at 2:49pm

baltik Avatar

Aug 8, 2019 at 8:57pm baltik said:

I just installed a 40A DC to DC charger - my dip switch are as folows:
Up Down Down Down Up

which I would expect to put out a constant 14.4 Volts. However, I am measuring a 13.56 at the output terminals. Is it supposed to take a long time to hit the desired voltage? Are my dip switch settings wrong?


Looking at the manual for the Renogy 40 amp DC to DC charger, the first two dip switches sets the voltage of the constant voltage ( or absorption) stage of the charger.


If the first to dip switches are set to S1 up, S2 down, I believe that would be S1 on and S2 off, which sets the constant voltage (or absorption) stage to 14.7 volts.


S3 and S4 set to down down, or off off would set the float stage voltage to 13.2 volts.


S5 set to up, or on, would set the charger for lead acid batteries.


What is the state of charge of battery?  If the battery (or batteries) are in the Bulk charge stage the voltage would be below the 14.7 volt absorption stage voltage. When the battery reaches 14.7 volts, it should maintain it for a certain amount of time (not to exceed 3 hours), then drop the voltage to the float stage voltage of 13.2 volts.


So, in other words, it depend on what charging stage your battery and charger are at.


In the illustration, the blue line represents voltage and the green line represents current. You can see how the voltage changes depending on the charging stage.


Posted by js77

Aug 21, 2019 at 3:54pm

I just called support because I had a problem with my switches as well. I'm using the 20 amp DC to DC charger. When I set up my device according to what the manual said it was not charging at all. Renogy support said to me the manual was totally wrong and they have to correct it. Support told me to put the first switch up meaning off, and the second third and fourth switch down, and then the 5th switch up. I'm running a lithium battery that can take a charge at 14.4 or 14.6v constant. lithium batteries are supposed to be charged at constant voltage and they have a built-in battery management system that takes care of everything. My battery has a Bluetooth that tells me it's status and before it was not charging and now it is charging so I think the problem is solved. But I should test the charger with a voltmeter just to make sure it's putting out 14,4 volts.

add just now in a you tube video of Will Prowse, who reviews these thing, i see a commenter posted this


"I purchased the Renogy DC/DC charger 40A model. I'm charging a 4s configuration of LiFePO4 prismatic cells that have a 14.5 charge maximum. I wanted to configure the dip switches correctly, but the manual (page 22) was confusing. After going on the renogy site, I was still confused so I called support. They informed me there is a typo in the printed manual. Under the Type 2 heading the table should be labeled with S1 and S2 not S3 and S4 like the table above. In my case, the Dip switch settings will be S1 - OFF, S2 - ON, S3 - ON, S4 ON, and S5 - OFF.


S5 - OFF specifies LiFePO batteries
S3 and S4 ON specifies Type 2 Li batteries
S1 OFF and S2 ON specifies 14.4V charge mode"

Posted by Admin

Aug 22, 2019 at 10:24am

baltik Avatar

Aug 8, 2019 at 8:57pm baltik said:

I just installed a 40A DC to DC charger - my dip switch are as folows:
Up Down Down Down Up

which I would expect to put out a constant 14.4 Volts. However, I am measuring a 13.56 at the output terminals. Is it supposed to take a long time to hit the desired voltage? Are my dip switch settings wrong?





SW5 dictates LI charging (OFF) or lead acid charging (ON)

in LI MODE (SW5 = OFF), THERE IS NO FLOAT

TYPE 1 S3 = ON, SW 4 = ON, this moves the charging voltage to TYPE 2 if you don't want the 13.0, 12.8, 12.6 V charging

TYPE 2 SW3 IS INCORRECTLY PRINTED, IT SHOULD BE SW1, AND SW4 IS INCORRECTLY PRINTED AND SHOULD BE SW2. SW1 ON, SW2 ON = 14.6V now.


SW5 (ON), the instructions in the manual are correct


-Renogy Team

Posted by Dave

Oct 16, 2019 at 7:39am

I just want to point at this this thread is from 2 months ago, and still there is no updated manual posted on Renogy's site. This is a simple edit. The incorrect table for lithium batteries is more than a typo. It is impossible to figure out how to set up this charger to work with Renogy's LiPo batteries the way it is now.

Posted by Mk

Dec 8, 2019 at 4:37pm

I've had contact with Renogy and they have now updated the manual on the UK website, unsure if they have done so on other countries.

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