Check my work

[Albatross Adventures]

Was wanting this community to critique my diagram for my electrical set up I’ll be beginning to install.

I want to be sure that the shore power goes straight into the invert/charger (with auto transfer switch) as well as be sure I need nothing else added or moved around. Thanks!

If it matters, the inverter/charger is a 2500w AIMS and I plan to have 400ah.

 

[Rucker]

Definitely a good start.

With this setup you'll be running lights, fan, water pump off the battery only, so if you drain the batteries you may be SOL until they recharge.

Consider having some way to run those devices off shore power as well. A more versatile setup.

 

[Rwnielsen]

Definitely a good start.

With this setup you'll be running lights, fan, water pump off the battery only, so if you drain the batteries you may be SOL until they recharge.

Consider having some way to run those devices off shore power as well. A more versatile setup.

Shouldn't the "inverter/charger" take care of that?

 

[dzl_]

Shouldn't the "inverter/charger" take care of that?

Yes, it should. The inverter/"charger" name throws a lot of people off, who are more used to the traditional RV setup where a direct connection between the AC system and shorepower is more common.


The way you have it in your conceptual diagram, is to the best of my knowledge how inverter/charger's are designed to be wired. And is not a limitation in the way that many unfamiliar with inverter/chargers assume it will be.



But, there are specifics that may be unique to your model/brand inverter/charger. And there are surely pros/cons to the different approaches that I am unaware of.


I think Rucker's assumption is that (A) invert, or ( charge the battery when connected to shorepower. But I think this is mistaken. Considering the scenario they set out (depleted batteries, connected to shorepower), I believe your inverter/charger would be capable of (1) powering AC loads directly from shorepower (passing it through), (2) powering DC loads and charging the battery at the same time up to the limit of the charger (85A @ 12V in your case I think).



I think the misunderstanding is assuming the charger can only charge the battery. But to the best of my understanding electricity has no awareness of or bias toward where it flows, its like water or wind, it takes the path of least resistance, and just because its called a charger doesn't mean it can only charge the batteries, if there are hungry batteries and hungry loads in the same circuit, the charger will supply power to both, just as the solar charge controller would, despite the name charger in the titles. Its quite possible I am understanding something (of a technical nature, or the implication of Ruckers comment, I'm a little dense sometimes, so set me straight if I've misunderstood anything).

 

[dzl_]

I can't seem to find any schematics in your inverter manual which is not confidence inspiring

https://www.aimscorp.net/documents/PICOGLF12W-25W12V120V 042121.pdf


Aims more expensive UL listed inverters do have schematics, but idk how comparable they would be.

 

[Rwnielsen]

Was wanting this community to critique my diagram for my electrical set up I’ll be beginning to install.

I want to be sure that the shore power goes straight into the invert/charger (with auto transfer switch) as well as be sure I need nothing else added or moved around. Thanks!

If it matters, the inverter/charger is a 2500w AIMS and I plan to have 400ah.

That looks fine to me, I'd go with it. :wink1:

 

[Albatross Adventures]

Yes, it should. The inverter/"charger" name throws a lot of people off, who are more used to the traditional RV setup where a direct connection between the AC system and shorepower is more common.


The way you have it in your conceptual diagram, is to the best of my knowledge how inverter/charger's are designed to be wired. And is not a limitation in the way that many unfamiliar with inverter/chargers assume it will be.



But, there are specifics that may be unique to your model/brand inverter/charger. And there are surely pros/cons to the different approaches that I am unaware of.


I think Rucker's assumption is that (A) invert, or ( charge the battery when connected to shorepower. But I think this is mistaken. Considering the scenario they set out (depleted batteries, connected to shorepower), I believe your inverter/charger would be capable of (1) powering AC loads directly from shorepower (passing it through), (2) powering DC loads and charging the battery at the same time up to the limit of the charger (85A @ 12V in your case I think).



I think the misunderstanding is assuming the charger can only charge the battery. But to the best of my understanding electricity has no awareness of or bias toward where it flows, its like water or wind, it takes the path of least resistance, and just because its called a charger doesn't mean it can only charge the batteries, if there are hungry batteries and hungry loads in the same circuit, the charger will supply power to both, just as the solar charge controller would, despite the name charger in the titles. Its quite possible I am understanding something (of a technical nature, or the implication of Ruckers comment, I'm a little dense sometimes, so set me straight if I've misunderstood anything).

I think the problem might be that the 12v fuse box is in line after the battery bank so that the only source for power is from the bank. I’m thinking maybe to put the fuse box before the battery bank and somehow have it set up to where while the batteries are charging on shore power the fuse box only takes power from the inverter/charger rather than from the battery bank, mostly to extend the life of the batteries. Any suggestions on reconfiguration for this?

 

[Rucker]

I think Rucker's assumption is that (A) invert, or ( charge the battery when connected to shorepower. But I think this is mistaken. Considering the scenario they set out (depleted batteries, connected to shorepower), I believe your inverter/charger would be capable of (1) powering AC loads directly from shorepower (passing it through), (2) powering DC loads and charging the battery at the same time up to the limit of the charger (85A @ 12V in your case I think).

Thanks Dzl, I remember this conversation from another thread. And AC should not be an issue b/c it passes through.

For DC, I'm guessing that you are right, that the DC output will feed whatever, up to the max current output of the device.

Here's where it gets fuzzy: the device is designed primarily as a charger for the battery. I believe the charge profile determines when you will get max current-probably only during the bulk charging phase. It is unclear to me what will happen at absorption or float, but with high current loads I could imagine there's a risk of voltage sag because the device is feeding constant voltage not constant current.

Maybe it's not even an issue.

Maybe others have an inverter/charger and can weigh in.

 

[Rwnielsen]

I think the problem might be that the 12v fuse box is in line after the battery bank so that the only source for power is from the bank. I’m thinking maybe to put the fuse box before the battery bank and somehow have it set up to where while the batteries are charging on shore power the fuse box only takes power from the inverter/charger rather than from the battery bank, mostly to extend the life of the batteries. Any suggestions on reconfiguration for this?

Interesting concept. I think you'd have to include an isolation device of some kind for that to work.
On my bus, currently, I'm using the 2 starter batteries along with a 35a converter. I don't have any electrical service where I'm parked. I go in the bus a turn on the lights and start up a generator then power up the converter. Then fire up the heaters. The converter powers everything and (should]) keep the batteries topped off. The batteries alone will run everything for a short while but they're more of a buffer. I actually have the converter output and battery positive tied together at a little 12 volt fuse block. I would think an inverter/charger would work the same way

 

[dzl_]

I think the problem might be that the 12v fuse box is in line after the battery bank so that the only source for power is from the bank.

I think that won't matter (and isn't really accurate).

First, while I can't see how you plan to wire anything from your conceptual diagram, I don't believe that the fuse box is 'inline' after the battery, or at least it doesn't need to be.

For one, you could just use positive and negative busbars, which consolidate and link all connections before getting to the battery, this is a pretty standard method.

But even if you didn't, the way I am looking at it you have two circuits (1) the charging circuit, and (2) and the loads circuit. While they are logically separate, they are physically not separate, they are connected to eachother at the battery terminals or at the positive and negative busbars if you go that route.

This is how I'm picturing it (purple dotted line = flow of electrons during battery charging, yellow dotted line = flow of electrons from inverter/charger to 12v loads, blue thing in the middle is a 4 cell lifepo4 battery):

Additionally here is an example of how busbars are often used ot consolidate connections before the batteries:

I’m thinking maybe to put the fuse box before the battery bank and somehow have it set up to where while the batteries are charging on shore power the fuse box only takes power from the inverter/charger rather than from the battery bank, mostly to extend the life of the batteries.

I'm not 100% positive, but I think that this is most likely unnecessary complexity for little or no gain.

The most important things you can do to extend the cycle life of a LiFePO4 battery is to (1) keep tour batteries in the same temperature band that humans are comfortable in, and especially avoid prolonged high temperatures above 90*F or so. (2) Don't charge at or near freezing (cell temperature), (3) Use a charge profile specific to LiFePO4, most importantly use a low float voltage, or no float, and a short absorption time, (4) Don't cycle 0-100% (5) Keep max continuous C rates reasonably low, most batteries are rated for 1C discharge (that means 1A per 1Ah capacity) but most are happier in the longterm below 0.5C (0.5A per 1Ah capacity).


Same disclaimer applies though, I misunderstand things all the time and I'm not an electrical expert.

 

[dzl_]

Here's where it gets fuzzy: the device is designed primarily as a charger for the battery. I believe the charge profile determines when you will get max current-probably only during the bulk charging phase. It is unclear to me what will happen at absorption or float, but with high current loads I could imagine there's a risk of voltage sag because the device is feeding constant voltage not constant current.

Maybe it's not even an issue.

Okay, so disclaimer, my depth of understanding with CC/CV and the math of figuring out current in practice beyond the basic theory of I = V/R is quite quite limited.

Here is my best limited understanding of 3 stage charging:
Stage 1 Constant Current "Bulk" -- Charger will increase/adjust voltage to attain a certain current level until the target voltage is reached.
Stage 2 Constant Voltage 1 "Absorption" -- Charger will remain at the target voltage, current will taper as resistance (of the battery) increases as it nears full
Stage 3 Constant Voltage 2 "Float" (as it relates to lifepo4 specifically) -- Charger drops down to a lower voltage, so as not to overcharge the battery while still being able to power loads.

You bring up a good question about what the dynamics of stage 2 and 3 would look like. I think that you are correct that:

Maybe it's not even an issue.

But I can't say I have the technical depth of understanding to know/prove it with certainty.

I think its either a small issue or a non-issue for a few reasons.
1. In other forums I'm on, the approach in the OP is the default, and the hypothetical problem you identified would be true of any charge source (solar, alternator, inverter/charger, dedicated charger, they all use 3 stage charging algorithms) with the exception of devices with a dedicated load output but these are usually meant only for smaller loads.
2. Float (with regards to lifepo4) is used to power loads when the battery is full (it has other purposes with lead acid, but with lifepo4 this is the only reason to use float at all, as far as I'm aware). The fact that it exists at all, is at least roundabout evidence that its possible to power loads directly during CV.

However, even if we both can accept/agree that you can power loads during CV, the question of 'but how much current?' still applies. And that is where I just don't know. And I also don't know in that situation what % would come from the battery and what % from the charger. These are good points you bring up that I don't have answers to.

But my question to you is, if we assume that this is a problem with a 3 stage charger (and this would be as true with solar or alternator charging or a dedicated charger as it is with an inverter/charger then) what alternative method/arrangement/component would sidestep this hypothetical issue?