VSR Batt relay question

Ya know... I would not think significant, but I let the truck and camper sit overnight and it was still drawing in the morning with the house batt at 12.8. I think cutoff is 12.7. My trimetric says I had 80% charge. And the truck was still drawing.

I really don't know if this is a problem or is it something that it always did and I just didn't know the VSR was drawing.

Maybe I'm just counting pennies, but I don't like to lose amps!

acudr wrote:
K Mac, The VSR - Voltage Sensing Relay is a small box like device hidden in your camper that allows the truck to charge your house (camper) battery when the truck is running and the voltage is above a certain level due to the running of the alternator, which is charging your truck batt. Somewhere above 13volts. Then when you turn your truck off, it is supposed to not let the house battery keep drawing from the truck while at rest. At rest, the truck batt should drop to 12.x below the voltage the VSR looks for to open. BEP is a brand name.

Apparently there are single and dual sensing VSR's. I believe mine (and probably most of ours) is a dual, which means if the house batter is charging, from being plugged in, the truck battery will charge also. My issue is I don't think this is a good idea as it seems, after charging, my house battery seems to stay at 13v for a while, so the VSR is letting energy leak out to the truck battery. My guess is and I am waiting and watching, is that when my house batt goes below the threshold, the VSR should shut off. I am certainly hoping this is the case as I am very miserly with the house batt and am not happy it's drawing.

The thing is, is that I don't think I would have ever known this is happening if I had not looked and wondered what this box was and why it's red light was on. Now that I know, this may have always been happening and I just didn't know it and thought the .3-4 amps was being drawn by the fridge or something else.

If this is the case, I will be looking for a single path VSR. However, these things are not easy to find and are typically dual sensing.

Hooking it up in the right direction matters too.

This is the single sense BEP model I installed under my hood. The dual sense is p/n 710-125A-DS.

I kind of wish I had the dual sense one because my truck sits for weeks/months with the camper on board, plugged in to shore power but the truck battery isn't getting topped off. I would think the residual charge would pull the voltage down below 12.8 soon enough without losing any significant capacity.

Thanks guys (acudr Kayteg 1) Electronics has never been my forte (retired mason), but now that I've got time , I plan on doing some mods to my toys. I try to school myself somewhat through various internet searches, ( which is a learning process in itself ), I appreciate the feedback. K Mac

My combiner (used on motorhome) is set to connect at about 13.5V and that voltage is present only when charging.
Meaning each time you stop the engine, or pull the cord on charger it disconnect immediately.
Than you have circuit that draws some current, but that should be minimal.

K Mac, The VSR - Voltage Sensing Relay is a small box like device hidden in your camper that allows the truck to charge your house (camper) battery when the truck is running and the voltage is above a certain level due to the running of the alternator, which is charging your truck batt. Somewhere above 13volts. Then when you turn your truck off, it is supposed to not let the house battery keep drawing from the truck while at rest. At rest, the truck batt should drop to 12.x below the voltage the VSR looks for to open. BEP is a brand name.

Apparently there are single and dual sensing VSR's. I believe mine (and probably most of ours) is a dual, which means if the house batter is charging, from being plugged in, the truck battery will charge also. My issue is I don't think this is a good idea as it seems, after charging, my house battery seems to stay at 13v for a while, so the VSR is letting energy leak out to the truck battery. My guess is and I am waiting and watching, is that when my house batt goes below the threshold, the VSR should shut off. I am certainly hoping this is the case as I am very miserly with the house batt and am not happy it's drawing.

The thing is, is that I don't think I would have ever known this is happening if I had not looked and wondered what this box was and why it's red light was on. Now that I know, this may have always been happening and I just didn't know it and thought the .3-4 amps was being drawn by the fridge or something else.

If this is the case, I will be looking for a single path VSR. However, these things are not easy to find and are typically dual sensing.

Hooking it up in the right direction matters too.

google VSR

Or try VSR switch

I think it is the same thing what battery combiner.

Ok, I'll be the dumb one. What are VSR's & BEP's. Thanks

No.... I have not been plugged in for about a day. That is what is baffling me at the moment. My trimeric meter is showing 90%. I would think the voltage showing would be lower than 13v. My previous experience and when we're camping is that it is, unless I haven't paid close enough attention until now as I am setting up the camper etc, and have not looked at the relay to see if the red light is on or not. .

My concern is the house battery not plugged in is losing amps.

Is your RV plugged into shore power? It must be if your battery is at 13v. If so, if that's above the cut-in voltage then yes, it will be engaged and charging the truck battery too.
This is how mine works. I like it that way. When I'm camped the RV converter keeps the truck battery topped up.

Thank you. I have a BEP. I did just find an installation sheet and I believe I have the wiring correct. I left it connected last night and the red light is still on, drawing .39amps. It is warm to the touch. I am confused as to why it is still on as the truck has been sitting all night and not charging. My house battery is at 13v

This is what I am thinking now... After looking at the instructions, there seems to be a single sensing type and a duel sensing type. I am wondering if I bought a duel sensing type. If I am not mistaken, the duel sensing type will charge in either direction. Not sure why my house batt is 13v, but maybe the truck is drawing from the house batt.

What do you think?