A communication with an electrician made me somewhat unsure about my installation. I am 70% through installing a new system on a sailing boat, as schematically illustrated in the attached document. My question concerns the Orion XS: can that be installed after the FET?
I like the Orion to be at the FET because a shore powered charger on the starter battery will then never activate the Orion. With the alternator running, the other (non-lithium) batteries will act as a voltage buffer, so that the Orion XS can be activated based on a sufficiently high voltage. Most of the time, i.e. when the alternator is not running, however, the Orion will not have an input.
This is not a great idea, since by definition the ArgoFET outputs are separated from each other, which means that the Orion XS will not have the required Pb battery on its input as a “buffer”.
It would likely work in this configuration for a while, but the Orion XS is likely to suffer non-warrantable failure in this proposed non-supported installation.
hmmmm, I would like to argue that the battery serves as a buffer to the Orion despite both being separated by a FET (provided the difference between “shutdown voltage” and “start voltage” is not chosen too large).
Here is my rational: when the alternator is running, there is a voltage at the battery of about 1.0 to 1.5 V above the current the battery would/will acquire without an alternator. For all currents within that window of current, the FET is “open” towards the Pb batteries. That gives a window of, say, 0.7 V (between “start voltage” and “shutdown voltage”) for the Orion XS to safely operate. The Orion XS, once it starts to draw current (during charging), will lead to a drop in voltage on all FET outputs. If the voltage drop, however, is kept within the window of (say) 0.7V, there will always be a counter current on the conventional Pb batteries (i.e. the FET is open towards the Ph batteries). This is what I referred to as ‘buffer’, because the current/voltage control of the Orion can operate with sound current stability due to the other Pb batteries. Do I make a mistake in this thought (you are an Expert and I value your response)?
By definition the ArgoFET Battery Isolator prevents the Orion from being connected to the Pb batteries, so by connecting the Orion to one of its outputs you’re isolating the Orion from the Pb batteries. Something that it’s isolated from can’t be a buffer for it. I understand the rationale that the batteries present on the first two outputs will help stabilize the input voltage, but that’s a theoretical approach that depends on the operation of those two batteries, whether they’re fully charged or not, whether their main fuses are intact, and doesn’t assist in the event of voltage spike caused by sudden output cessation from an instance like the BMS shutting off the ATC.
Why not just connect it from one of your start batteries, and use an ignition trigger so that it doesn’t turn on unless your ignition is on?
yes, I assume (one of) the two Ph batteries are intact. If they wouldn’t my alternator would overheat and blow.
Wiring the ignition trigger is quite some effort on my boat, but earlier, I considered an electronic switch, which turns the Orion XS off, once AC current for the shore power charger is on. I would like a set-up without an additional switch, according to the scheme attached in my initial post - but based on your comment I might reconsider this concept. Thanks for your answer.