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
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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
Despite their ratings being the same, the batteries will be slightly different so there's some benefit to independently charging them. My initial question was in fact, will the solar cause the relay to combine the batteries. These devices are voltage triggered after all. When I install the solar I will likely connect a relay to the negative line on the relay. This way, the relay will only be active when the battery switch is on or if I can find an independent output on the alternator, when the engine is running
The ACR connects the battery when one side of it has a specific voltage applied to it (see linked article for a much better explanation). When there is sufficient solar output and the controller raises the voltage to that level, the combiner will close and the batteries will be connected.
It is correct that batteries will have different charge acceptance rates depending on different ages and conditions, however the charge acceptance is current, not voltage based. The amount of amps a FLA battery can accept is determined by the battery and not the controller, if the controller is set to provide 14.5v in the bulk stage, it will provide as many amps as it can at 14.5v. If one battery can accept more amps than the other, it will accept more than the other battery.
On LA batteries the internal resistance of the batteries will determine how the available amps are divided, the battery with the lower internal resistance will accept more.
In real life, a dedicated start battery will seldom if ever be deeply discharged as the number of ah needed to start is remarkably low, on the order of 1 or 2 ah per start. As a result, it is recharged quickly and the internal resistance goes up, reducing the number of amps it can accept. If the start battery can only accept 1 amp and the controller can provide 5 amps, then the remaining 4 amps will go to the house batteries. There is no advantage, and perhaps some disadvantages to turning the ACR off and on or by passing it under certain circumstances, with one exception* that has nothing to do with distributing power from solar panels.
Making Sense of Automatic Charging Relays - Marine How To
Making Sense of the ACR WARNING: ACR's are not for use with LiFePO4 Batteries! What is an ACR? An ACR is nothing more than a fully automatic, voltage triggered, BOTH/PARALLEL switch that closes when charging voltage is present and opens
marinehowto.com
*The one exception is while starting the engine. When the starter is first engaged the current, the voltage on the start battery can drop causing the a power surge through the ACR that can damage the ACR, that's why there is a start interrupt circuit to protect the ACR.
You will not be charging the batteries independently under your plan. This is the point you are missing. That solar controller does not charge batteries separately - it is in practice a VSR itself, with the two outputs being combined from the single input, and both having the same charging program and profile in your case. That is why the VSR is redundant here. At least for solar charging, as the VSR will also work with other charging sources.
If you had two different types of batteries (FLA and AGM), then there would be merit in using both controller outputs with separate programs and profiles, but then the VSR wouldn't be suitable at all.
To answer your questions, yes, the solar will trigger the VSR. Yes, you can set it up like you plan, but there is no advantage to doing so, it adds complications without fail warnings to a system one usually wants to not have to pay attention to, and it removes the possibility to solar charge the batteries with the battery switch off. If you wire a solenoid to the alternator (a D+ terminal will work for that), then you will have both the solar and VSR active when running the engine during daylight anyway - just the situation you are trying to avoid for some reason.
Mark
I think this is the point that the OP is not fully appreciating. A charge controller only limits voltage, not current, and the batteries themselves limit the current they take naturally. Since the OP has identical types of batteries, regardless of size or age, they will not and cannot be independently charged by his specific solar controller. Nor will combining with a VSR lead to over or under charging one of the batteries. The charging through the solar controller and VSR will be identical and redundant here.
Mark
@colemj I get what you're saying. No matter how these components are wired up, this will be far from an ideal system. For the start of this upcoming season, I will try using the boat without solar. It's a new to me boat and few c30's I see on moorings have solar. For now, this VSR will aid in alternator only charging of both batteries instead of just one and likely prevent me from accidentally running down both batteries while on the hook. This was my original intent but the interference of the voltages generated by solar did not dawn on me until after I had purchased the VSR
@dlochner Would it be advisable to put in a lower amperage fuse to protect the relay? The relay is rated at 65A. Perhaps a 40A fuse would be beneficial during starting conditions if I decide to add solar? I'm not opposed to connecting the start sense terminal if I have time
@dlochner Would it be advisable to put in a lower amperage fuse to protect the relay? The relay is rated at 65A. Perhaps a 40A fuse would be beneficial during starting conditions if I decide to add solar? I'm not opposed to connecting the start sense terminal if I have time
No, because you will be blowing fuses every time you start the motor. Connect the Start Interrupt feature, it is simple, one wire, follow the instructions.
You are way overthinking this and you have gone down a dead rabbit hole. The ACR doesn't care where the power is coming from, alternator, charger, solar, or mysterious forces from the alternate universe. It is solely controlled by the voltage it sees on its terminals. If the voltage rises to the threshold level, the batteries are combined. If one battery needs lots of current to charge, most of the current will go there. That's it, it is that simple. To make it even simpler, put all the loads, charging sources, and ACR on one DC+ bus bar connected to the House bank. Connect the start battery to the starter and the ACR. The wiring is then neat and easy to trouble shoot. That is the basic wiring I've used for the past 10 years or more with no difficulty. When I installed the LFP batteries last year, I replaced the ACR with a DC-DC charger because the LFP and AGM have slightly different charging protocols.