Blue Sea ACR (humm)

JWL

Senior Member
Joined
Feb 25, 2020
Messages
312
Location
Texas
I have a Blue Sea ACR in my 2020 Hawk Shell. Last year I installed a 100 AH Lithium in the camper. Knowing that the AGM in the truck and the LiPo4 charge differently I disconnected the wires at the truck batt and at the ACR. I have minimal power usage in the camper and the 200 watt solar here in the South has never not been able to keep up. I did anchor the wires from the truck and the camper in case I needed to get a recharge sometime while driving and reconnect them. The other day while in my garage I heard a high pitched hummmm. (At my age ear ringing is not unusual) I thought it was from the fluorescent lighting, but no. In the camper I discerned it was coming from the ACR. Bat was at 13.27 v, camper power/relay switch was off and everything seemed as usual. So, is the ACR dying? Is it trying to connect to a nonexisting battery? (Although in the last year we have never heard it) Is there something wrong with my thinking on leaving it partially connected? We thought maybe because it was so quiet that is why we heard it but I just wanted to make sure there was not a problem lurking.
And yes I know the best solution is to get a DC-DC charger, but I’m not in a position to replace the wiring and as stated our needs don’t justify it.
Thanks!
 
Do you need to charge the battery from your truck any more? It sounds like you are doing fine just with solar. Maybe you could just disconnect your camper-truck connector.
 
If you want to leave the ACR in place partly connected in case you ever want to connect it for a truck charge, I would suggest one additional disconnection step:

Disconnect the ground wire to the ACR by pulling its in-line fuse. On my Grandby it’s around a 16 gage wire that is yellow, and it has a rubber covered in-line fuse holder right near the ACR. Pull that fuse. That will prevent the relay coil from being energized and it will depower the control electronics, which are probably the source of the noise. Save the fuse for reactivating it later if needed.
 
If Y’all are talking about the ground off of the ACR (and yes Jon it does have the fuse holder) it is still connected. I thought I needed that to ground everything like porch light. But I can easily pull the fuse and check…
 
That was it! Thanks! I guess that will teach me to “think”. And the fuse is safely stored with my spare fuses.
 
That was it! Thanks! I guess that will teach me to “think”. And the fuse is safely stored with my spare fuses.
Fyi that ground and fuse is ONLY for the ACR relay coil and its internal control electronics. If you pull the fuse to disconnect it the relay will stay open and you could actually leave the 12 volt positive connections to the ACR in place. Then all you would need to do is insert the fuse to restore the ACR function.

The rest of your camper grounds are still connected to camper battery negative via the negative bus bar and do not rely on that ACR negative fuse.
 
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. The other day while in my garage I heard a high pitched hummmm. (At my age ear ringing is not unusual) I thought it was from the fluorescent lighting,
I feel your pain on not hearing well…. While at the campground last week I drove to the shower house. After shutting the truck off I heard this humm. I couldn’t pin point the noise, it seemed to change as I moved around the truck. Checked my Victron App …. .0 amp draw, but I still disconnected the Anderson plug….it was still there.🧐 I turned off the 60A breaker feeding the smart charger, still there🤨

I thought, I’m going mad- then I remembered……I have since put a note inside my cabinet box:

IMG_2626.jpeg


🤣🤣🤣
 
I feel your pain on not hearing well…. While at the campground last week I drove to the shower house. After shutting the truck off I heard this humm. I couldn’t pin point the noise, it seemed to change as I moved around the truck. Checked my Victron App …. .0 amp draw, but I still disconnected the Anderson plug….it was still there.🧐 I turned off the 60A breaker feeding the smart charger, still there🤨

I thought, I’m going mad- then I remembered……I have since put a note inside my cabinet box:

View attachment 181466

🤣🤣🤣
You’re not alone.
 

Fyi that ground and fuse is ONLY for the ACR relay coil and its internal control electronics. If you pull the fuse to disconnect it the relay will stay open and you could actually leave the 12 volt positive connections to the ACR in place. Then all you would need to do is insert the fuse to restore the ACR function.
It doesn’t seem to be that simple for me, or maybe I’m the one that’s simple. But when I reattach the positive from the ACR to the truck leads I show the 13+ volts at the truck battery connection. So apparently the ACR is not disconnecting. The light is off. Am I missing something?
 
I'm not sure of what you are asking. Are saying/asking that you reconnected the heavy positive wires to the ACR and then measuring the voltage back under the hood to see what's coming back from the camper through the ACR? The ACR does monitor the voltage coming from both sides and connects them if charging is present.
 
If you leave the camper battery side wire connected and the truck battery side wire connected, assuming no other switches or circuit breakers in those wires, you have a hot battery connection to each of those batteries on their respective sides of the ACR. Assuming the truck and camper grounds are tied together, if you put a volt meter on each one at a time using a nearby ground you will measure the associated battery voltage for each battery. If the ACR ground wire is disconnected, the ACR relay will be open, and the two batteries won’t be connected through the ACR. You still will see battery voltage on each side

The LED on the ACR will be off. If the ACR ground was connected, the LED being off would tell you the relay is open. However, when the ground is disconnected all it really tells you is the ACR has no power. The relay contact theoretically could be welded closed and the LED would still be off due to lack of a ground for the LED. Such a failure can happen, but is unlikely, especially on a 4 year old contactor that has probably seen only a couple hundred cycles. You can measure for such a failure by disconnecting all wires from the ACR and putting an ohm meter across the two battery connection terminals.
 
OK thanks guys, I think I got now. I miss understood Jon’s comment about pulling the fuse. I thought that would disable the ACR from passing voltage from one Batt to the other and if I wanted to charge from the truck I would just need to put the fuse back in. Yep wishful thinking again. Or not stopping to think about it, again.
But back to the beginning the humm is gone and nothing is melting so that is good.
And this boys and girls is exactly why this site is priceless!
Thanks!
 
Here is a picture of my unused ACR still in place (I have a dc to dc charger for my camper’s LiFePO battery). The fuse holder for the ACR negative can be seen clearly in the yellow negative wire. For others who might view this thread later, note that, while details may vary, there typically is also a second yellow wire with an identical in-line fuse holder on campers that have running lights. That is the positive wire and fuse for the running lights. On my Grandby front dinette the two fuse holders are right next to each other.
 

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OK thanks guys, I think I got now. I miss understood Jon’s comment about pulling the fuse. I thought that would disable the ACR from passing voltage from one Batt to the other and if I wanted to charge from the truck I would just need to put the fuse back in. Yep wishful thinking again. Or not stopping to think about it, again.
But back to the beginning the humm is gone and nothing is melting so that is good.
And this boys and girls is exactly why this site is priceless!
Thanks!
You wrote: “I thought that would disable the ACR from passing voltage from one Batt to the other and if I wanted to charge from the truck I would just need to put the fuse back in.”

That is the way it should work.

Pulling the fuse in the negative yellow wire to the ACR will prevent the ACR from connecting the two batteries. If you put the fuse back in the batteries will be connected if either side of the ACR exceeds the set point (13.0 volts for 2 minutes or 13.6 volts for 30 seconds).

If you are running the truck to charge the camper battery you will get some charging as limited by your wire size and alternator voltage, but it’s not the ideal arrangement for charging a lithium battery.

If your truck is not running but your lithium battery is at or near a full charge, the lithium battery voltage will cause the relay to close. The ACR will cycle on and off until the truck battery draws the lithium battery below 13 volts when isolated. You don’t really want that, so keeping the fuse pulled unless you actually want to charge from the running truck would be best. Alternatively, you could control the ACR with an ignition on/off wire to only close the ACR when the truck is running. There might be overcharging concerns for the lithium battery with such an arrangement. Others probably can chime in with advice on that.
 

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