Electrical question

[tanukihimself]

Yall have helped me so much, thank you tons!


So, defjr333, what im still unclear on is how the power from a shore plug in gets to your batteries? If the inverter uses the DC from your batteries and makes it into AC, how does a plug from the, just say, campground get power into the batteries? What piece of equipment does that?

Seems that if I get a aims 2-3k watt inverter/charger
A 30amp power control panel
A couple solar panels
a charge controller
And a few batteries
----I should be good. I just still don't understand how to get shore power into those batteries if I go to a campground. Im sure it has been explained to me but I need it in either a simple diagram or very lay terms Haha, this is all new to me. Again, its the part about what actually gets non solar power into the batteries that im missing

[Esteban]

http://amsolar.com/diy-rv-solar-instructions/

[tanukihimself]

Thanks ill watch when I get a sec.

Looks like the aims 2 or 3 k watt inverter/charger also has a built in converter to convert shore power into dc...

[McDave]

That'd be the "charger" part of the inverter/charger.
DA DA DADA DA DA...CHARGE!...............

McDave

[John61CT]

Yes the RV industry's use of the term "converter" for charger annoys me, very confusing.

Do these units do anything special to act as a power supply for House loads, and still keep track of declining current acceptance rates to the battery?

[hankaye]

John61CT, Howdy

... Do these units do anything special to act as a power supply for House loads, and still keep
track of declining current acceptance rates to the battery?

That is exactly what they were designed for and from my experience (8 years of RV full-timing), they do what they
are supposed to do, and do it very well.

hank

[defjr333]

inverter/ charger has an input terminal (hot, neutral, grnd) to wire to a shore input plug mounted on trailer wall. Mine uses a 10/3 awg wire between the two. The inverter/ charger i use passes the shore input straight thru to the breaker panel(pd5000) and devices. Any unused power is converted to 12dc to charge batteries(connected via 00awgwire). When the shore power is unplugged, the inverter/charger automatically switches to pulling 12vdc from batteries and inverting it to 120ac. It does this in .05 seconds. Most electronics wont even notice. In theory i have just built a big a$$ UPS battery backup unit with solar and a generator to boot. Hope that clears it all up. Inverter: 12vdc to 120ac, Charger: 120ac to 12dc, Transfer switch: switches between 120ac sources( shore, generator, inverter) for which ever is best and available.) This unit has all 3 devices inside.

[John61CT]

That is exactly what they were designed for and from my experience (8 years of RV full-timing), they do what they are supposed to do, and do it very well.

So my next question is How?

Do they use a shunt to measure current going into the battery?

What makes them superior to a good quality charger, not garage-style junk, but as used on yacht House banks or off-grid solar?

[defjr333]

While hank will no doubt know the ins and outs of how and why, I only know the inverter/ charger somehow does "look" at the battery and incoming current state and adjusts the charge current and voltages accordingly. It is a 3 stage charger with battery type selectable. As to how it does this...via shunt or a digital measurement thru rectifying diode, I cannot say. So I would think that portion of a good inverter/ charger would be nearly identical to a high end converter.

[John61CT]

Without a separate shunt, I believe there is no way for any charge source to know how much current the battery is accepting vs concurrent load consumption.

I guess that's why most use volt setpoints plus time settings.

[MtnDon]

............ I only know the inverter/ charger somehow does "look" at the battery and incoming current state and adjusts the charge current and voltages accordingly. It is a 3 stage charger .......

Any charger that is advertised as a three stage charger uses battery voltage to determine how long to run the first stage (bulk charge). Current input to the battery should be more or less constant as the voltage rises. Once that voltage set point is reached the unit changes to absorb charge which is usually a time determined event. The charge amps slowly fall while the voltage is held constant. Some,up-scale units may be able to be programmed to terminate absorb charge by the amperage. Amperage input to the battery falls during absorb due to the nature of how lead acid batteries act. The final third stage is float which is both voltage and current controlled.

[John61CT]

The charge amps slowly fall while the voltage is held constant. Some,up-scale units may be able to be programmed to terminate absorb charge by the amperage. Amperage input to the battery falls during absorb due to the nature of how lead acid batteries act. The final third stage is float which is both voltage and current controlled.

Yes, and the question at hand is:

In a context where there are always loads running of unpredictable varying amperage, some proportion of the output is feeding those loads, in addition to that proportion being pulled by the battery.

I am saying that, unless

A all loads are being fed from a separate controller load output, nothing directly fed off the battery's circuit

or B all charge input to the battery is being measured by a dedicated shunt between the battery and a dedicated "charge buss" separated from the load buss

then it is not possible for the controller to know how much current is being accepted by the bank, and therefore the controller will presumably keep output at Vabs rather than dropping to Vfloat, until the Total current (loads + charging) fall below endCurrent.

This will be more harmful to LFP and sealed lead banks, but most of us don't like even FLAs bubbling away unnecessarily.

[hankaye]

Howdy All;

First thanks to MtnDon for explaining the hows.

I have no knowledge of the hows when it comes to electricity and the movement of energy in
that manner. My last statement was only to express that these devices do work and work well
over an extended period of time. I'm an end-user not an electrical engineer.

hank

[MtnDon]

What the charger does when confronted by situations of simultaneous charging and power us is a good question. In particular, let's say the charge system has progressed through bulk and timed absorb and is in float now. No loads or just very small ones. You activate a big load for long enough to cause the voltage to drop to where the charge goes back into bulk charge. Then that load is turned off. My first question is, once the charger raises the voltage enough to complete second bulk charge, is the charger going to go back into a timed absorb? My thoughts are that most AC powered chargers will go through a full absorb cycle if they are using a timed system. In that case you can end up abusing the batteries a little FLA types will handle that okay.

If one has LFP batteries you need a charger that basically stops charging once the terminal (highest) voltage is reached. They don't need to sit in absorb charge.

My solar cabin system uses an end amps absorb termination and in the situation above will not stay in absorb very long the second time. It will be back in float very quickly. But my cheaper solar controller on the trailer will go through a second timed absorb if we use enough power after the system has run through the first bulk-absorb-float cycle of the day and is then used enough to cause a subsequent bulk cycle the same day. Then a second absorb. In this case the charge also terminates or tapers down as the the sun sets so it is not the same as a charger that is plugged in to grid power.

[John61CT]

Yes good points. A large LFP bank makes investment in the proper infrastructure necessary and worthwhile, allowing overcharging will reduce lifetime by a lot.