It dawned on me after I bought a voltage sensing battery combining relay that solar panels might interfere with the voltage sensing circuit of the ACR. Am I correct? I was thinking a solution might be a relay to disconnect the ground of the ACR. The coil of this relay would be controlled by the manual battery selector at the electrical panel. However, the solar panels would still be active and would combine the two batteries whenever there's sunlight and the battery switch is on. Any ideas would be appreciated
Auto charge relay with solar
- Thread starter Project_Mayhem
- Start date
It won't be an issue. When the ACR senses a charging current, it will allow the Start battery to receive a charge that will slightly decrease the available current for the house battery. However, since the start battery is almost always at 100% SOC, it won't accept much if any current.
Another, slightly more expensive way to charge the start battery is use a DC-DC charger, the Victron Orion 18a model is perfect for this application. When the battery is fully charged, it shifts into a float mode which uses very little current. The Orion will only charge the battery when the input voltage is high enough so it won't drain the house battery. The Orion works especially well when the charging profiles of the 2 battery systems are different, such as LFP and AGM, or FLA and AGM because it will provide the correct voltage for charging the specific battery. The ACR does not do this which is OK if the batteries have the same charging profiles.
The batteries are matching FLA's. I have a dual Morningstar controller that I bought a few months ago. I picked up the BlueSea ACR for meager $30 so I couldn't say no. The battery on my last boat was eight years old and still running strong so I think I'm good without the DC-DC charger. It would be ideal but not worth the expense at the moment
The answer to both questions lies in the ABYC Ampacity tables and how big a line loss you are willing to accept. For charging circuits the conventional wisdom is to keep the line loss as low as possible, 3% or lower. Two factors determine line loss, i.e., voltage drop due to the inherent resistance in the wire, length of the wire run (both directions) and wire size. Skinnier wires have more resistance and the longer the wire run the higher the resistance, thus, short runs and fat wires are best, within reason.
Each 100w panel will peak out at about 5a at 20+v. To have a 3% or less loss for a roundtrip distance of 60' 10 ga will work well. The ampacity rating for 10 ga105°C boat wire, i.e., the most current the wire can safely carry, is 50 to 60a, thus the current from one panel is well within the safety margin and will have minimal line loss if 10 ga is used.
Applying the same method to the ACR, the wire must be able to safely carry 65a. The Ampacity chart tells us that 8ga 105°C boat wire can safely carry the 65a. However, the loss table shows a 6ga cable is required to keep the line loss to 3% for a round trip distance of 10 feet. Thus, while 8ga can carry the current, 6ga would be a better choice.
I can be a bit of a fanatic when it comes to line loss. When there is a voltage drop over a wire the lost energy is manifested by warming the wire. It seems sinful to spend money to simply heat a wire up for no good reason. The cost difference between a smaller less efficient wire and a larger more efficient wire is minimal, especially when buying wire in long lengths, the benefit is a more efficient system and fewer wasted electrons. Almost all the new wiring on my boat is 10ga or 14ga and I tend to buy wire in 100 ft rolls. If the circuit can use 12, I up it to 10, if the circuit needs 16, it gets 14ga. The cost of having 2 big rolls of 10 and 14 is not that much different from having 3 smaller rolls of 10, 12, and 14 ga.
I have some 8 awg tinned lying around. It's only going a foot so line loss is negligible. I'm wondering how much current would actually go through this relay in the real world. It's supposed to switch itself off during starting so I can't image it's much.
Any thoughts on auto resetting breakers?
Any thoughts on auto resetting breakers?
My understanding (based on Nigel Calder’s book, not actual access to the standard) is that ABYC requires overcurrent devices to be manual resetting, not automatic. If the breaker trips you should need to take some action to figure out why and remediate that condition before the circuit resets.
The entire point of a VSR is to connect the batteries in parallel when a charging source is present, so I'm a bit confused on why you would want the VSR switched off when the solar panels are charging? Also don't understand the talk about DC-DC converter, as that would be redundant to a VSR.
Mark
Mark
The suggestion to use a DC-DC converter was instead of a VSR not in addition to. VSRs are not a good choice in mixed battery systems, such as FLA start and LFP house because they only support one charging protocol. A DC-DC charger can be programmed to provide the correct protocol to the battery being charged.
In a real world setting a stock internally regulated alternator will rarely if ever generate its rated. output and if it does it will be for a very short time before the internal regulators reduces the output because of overheating.
No, to auto resetting breakers. They might be ok to protect from a surge, however if there is a short they will cycle through tripping and resetting which is definitely not what you want to happen. The simplest solution to overcurrent protection on a battery is MRBF and if being used with a ACR, a double pole MRBF.
I ended up buying 4awg tinned wire with a single non-resetable fuse. The two cable runs are less than a foot. If it was longer I could see the justification for two fuses.
The solar controller has independent charge circuits for each battery or at least it's supposed to. Can these be charged as one bank? Yes, but charging them independently is a bit better as there are differences between every battery, even if they are the same model, age, etc
OK, I'm understanding your setup better, but I think you are making a mistake or misunderstanding what your Morningstar Sunsaver Duo is doing. That regulator splits the solar output into two banks, with each bank taking only the current it needs. This is exactly what a VSR does. There are only two settings on it - flooded and sealed, and since you will have both on flooded, you will not get any benefit from charging them independently over what a VSR provides.
By connecting both batteries to separate controller outputs AND using a VSR, you are just being redundant. Not a bad thing, and the solar isn't going to interfere with the VSR at all. What will happen is the possibility at any time that the VSR will not be combining because it senses the batteries are not charging, then the solar will charge one battery enough to trigger the VSR to combine, which will tell the Morningstar that it can put all of its current into only one battery now. In the end, you will effectively have the Morningstar charging only one battery with the VSR charging the second one off of it. You could just set it up that way from the beginning, or let your proposed setup do its thing naturally.
Mark