Inverter/charger .. where to ground?

[VanKitten]

So...I have confused myself.

So..I have an inverter/charger.   It is "smart".  That is..it will run directly from shore power if it is available, sending any extra to the battery.    otherwise it runs as an inverter from battery.   

So..it seems to me that the ground has to go the the shunt and there to the battery monitor.

Here is the confusion.     The matter monitor would "See" more power going through the ground than was drawn from the battery when the inverter is running in charge mode...driving the 120v outlets then only giving the extra to the battery.   Wouldn't the battery monitor think there was a lot more load on the battery than is real in that case.

I think the 120v breaker panel must be hounded thru the shunt as well?

Ok.  I am worried that there is more load than charge since the monitor would not see the charge going directly from shore power to the 120v panel than can be accounted for in the ground.    

Ok..I am confused.  Someone straighten me out 

One guy says I should ground the inverter to the shore power outlier??.  What...that makes no sense...that ground goes nowhere when the system isn't plugged into short power.

 

[highdesertranger]

there should be 3 grounds. the 12v ground to the battery should go through the shunt. the chassis ground should go to the chassis. the 120v ground floats. the 120v ground is provided by what ever 120v source you are connect to. do not bond the 120v ground and neutral together like you would do on a house. highdesertranger

 

[John61CT]

What make / model kombi unit?

12V is not a true ground, let's call that negative return. Should be same length and gauge of wire as positive, both direct back to charge source (battery bank, return outside of the BM shunt).

The unit's case, check its manual, if grounded, go to nearest negative buss, or chassis if you're sure it has clean path to engine block, I prefer to avoid that latter approach with modern build methods. This can often be left isolated NP but check the docs.

Now the built-in AC shore power transfer switch is a completely different and dangerous matter. Follow the unit's wiring diagrams and instruction very carefully.

Better to get a pro in on this last if you aren't sure.

 

[VanKitten]

I am sorry to be dense. Let me try again....this is the whole thing..

Case one...running just the inverter to power 120v outlets from battery

All power from the battery. Ground then the common ground to the shunt...(of course shunt to battery, battery ground to chassis).
Battery monitor "sees" when battery low and contactor shuts off load to prevent low discharge.
BUT... then....

..... running inverter charger from show power. Outlet in use but is only taking 50% of available power..remainder goes to charge battery

Battery monitor "sees" more drain via the ground than is really happening and directs contactor to shut off load because it believes it is seeing too high a drain...so it prevents damage from load drain that isn't actually happening. The charging to the battery isn't balanced by the output from battery. So how do I disregard the power flow to the 120v when it is from shore power...versus watch the power flow to the 120v when it is from battery? One positive line and one negative line connect inverter to the circuit panel.


Ok..case two

Ground is directly from inverter to chassis.

Everything the battery monitor sees is inaccurate...if running from shore power...the charge does not agree with ground. If running directly from battery through inverter...still inaccurate reading by battery

So..I feel that I have to ground that inverter to the common ground that goes through the shunt that is used by the battery monitor...but..then what happens in the case of running from shore power?

See my confusion?

HDR.... where do I connect a floating ground? I don't understand that...sorry to be dense.

 

[highdesertranger]

can you post a link to the inverter/charger you are using. highdesertranger

 

[VanKitten]

Yes...

https://www.amazon.com/Renogy-2000W...eywords=2000w+inverter+charger+pure+sine+wave

 

[highdesertranger]

ok you have 120v outlets on the inverter/charger. so disregard any 120v grounds and floating grounds. now look at page 10 of your instruction manual it shows the 12v hook ups. the positive(upper right of your pic) goes to 12v battery positive, the negative (upper left) goes to the load side of the shunt. the grounding terminal(lower right) goes to chassis ground. read the last paragraph on page 12 that refers to the grounding terminal chassis ground. does this clear it up? highdesertranger

 

[highdesertranger]

oh I forgot, on the 12v charger side the positive goes to battery positive and the negative goes to the load side of the shunt. highdesertranger

 

[rvpopeye]

Ohhhh Ayuh ^^

 

[Weight]

I'm confused. My battery monitor reads amps in and amps out for the battery. It doesn't care the amount of amps, it doesn't shut anything down. My inverter will shut down if the battery voltage drops too low. My charger shuts down if shore power is too low. My shore power line has the green safety attached to the van chassis. My chargers and inverter have a safety ground from their chassis to the vans chassis. My generator has a lug for a safety ground which gets connected to the van chassis or not. Mostly not. One side of my shunt has only the battery negative. The only way the battery grounds is through the shunt. The other side of the shunt has all other negative connections. Chargers, inverter, all the stuff that runs on 12 volts and the chassis return to the battery. Some of my 12 volt stuff returns ground by way of chassis connections. If there is a dedicated return ground wire, it has to be the same gauge as the positive, but does not need to be the same length. It helps with voltage drop if the wires are as short as possible. I have a terminal bar to keep all the wires neatly organized with one wire to the shunt and all other to the bar.

 

[highdesertranger]

Weight FYI the grounding lug on your generator is for earth ground(a rod driven into the ground). I don't believe you should connect it to the vehicle. highdesertranger

 

[Weight]

It depends on what expert I talk to. I, my self, don't use it. btw, I usually believe Mike Sokol. He kept our band stuff safe. http://noshockzone.org/generator-ground-neutral-bonding/

 

[VanKitten]

Sorry to be so long getting back to this thread. Nothin but mechanical problems has prevented me from getting back to all this

Let me explain.

I am installing 12v 400ah lithium batteries. My charging is either 700w of solar panels or 30amp (120v) from the shore power thru the inverter/charger. This device is supposedly smart to know it is driving 120v and charging when on shore power.

Because of the size of the batteries...I could not find a Battery Management System for lithium that would take over 100amps. So... the three functions of the BMS are...equalize the battery cells within the batteries. Charge and load equalize. Ok..got a balancer (actually... 4 of them.. had to wire I got in sequence ) the second function is to stop charging when the temps are too low or temps are too high. I am installing a system to do this manually for now. Finally...and this is the one that counts in this discussion..... stop the load on the battery when batteries hit the low of 10.4 volts....or..stop the charging of the batteries when the battery charge reaches 14.8 volts. (These are the parameters set by the manufacturer).

This final function is performed by a combination of the battery monitor and two contactors... one set to usually open...one set to usually closed. They operate at the direction of the parameters set on the battery monitor.

Ok...so...that battery monitor "sees" the ground via the shunt.

So..what happens when the inverter is running from shore power? It is charging the battery. BUT?.it is grounded to shore power...not the shunt? So the battery monitor is ignorant of the charge coming in? Right? Or..does that inverter have enough "smarts" to know that the ground must be to the main grounding busbar". I see that the one end of the inverter is wired to the shore power...and to the 120v circuit panel....grounded to the shore power. BUT, when the inverter has enough power left to be charging the battery...that is via the other end of the inverter (the charger end) that is 2gauge wire with a 300 amp fuse) to the power busbar.... ground wire the same size to the ground busbar.

Think of it this way...I have three bus bars. One is for ground. One is "power in". Charger and mppt connect here. The third is "power out" bus bar. I did this because I need to connect Load and Charge differently with the contactors.... they control the flow of power from and to them. (Just as an aside here....I have to put a manual switch in...3 way..off, on to the "power in" bus bar...and on to the "power load" busbar. Even though the inverter will do it automatically...I cannot let it. I have to separate the two functions because of the need to have those two contactors control the flow to and from those functions separately).

Is the inverter smart enough to know that when it is charging..it must put that much through the 12v ground system...not through the 120v shore power ground?

And..finally...I was going to ground from the busbar to through the shunt to the battery...then from battery to the chassis frame. Some people feel that is not good enough. I don't see any other way. Should I run a grounding cable to the engine block?
400 amps...maybe that is what they were think about.

Honestly, I have amazed myself. 3 months ago I didn't even know how to splice two wires together. This has been one wicked learning curve!

 

[highdesertranger]

ok don't worry about the 120v. the shunt is for monitoring the battery not the 120v. it will show the charge to the battery. as far as the wiring of the ground. one and only one cable attaches to the negative battery post it goes to the shunt. on the other side of the shunt a cable goes to the negative bus bar, all your grounds go on the bus bar including the chassis ground. highdesertranger

 

[VanKitten]

I thought the ground to chassis comes from the battery...

Common ground bus bar to shunt...to battery...

If I ground to chassis from ground busbar then what? What about shunt?
ok..confused again

I had a diagram a while back that showed the ground from negative battery terminal...one to shunt..one to chassis. No?

 

[highdesertranger]

no, if you have multiple grounds to the battery anything that uses those other grounds will not be measured though the shunt. one ground from the battery to the shunt. all other grounds(negatives) go to the other side of the shunt. that's why it's important to have a shunt and bus bar capable of handling the largest load plus 10% that it will ever see. highdesertranger

 

[VanKitten]

Ok...

If I have all the ground going through a common "ground" bus bar...then to the shunt....
It is then the shunt that the battery monitor "sees" whatnit going on.

If I ground to chassis on the busbar side of the shunt...the monitor doesn't see it.
So...I ground from the battery side of the shunt to both the battery and the chassis?
Two ground wires from the shunt after the monitor.

 

[Weight]

One side of the shunt. Only the battery negative wire. Battery neg to shunt. Nothing else on that side of shunt. The other side of shunt has all the other 12 volt ground wires. From chargers, inverter, lights, chassis, every 12 volt negative wire goes to that side of the shunt. That is a lot of wires so we use a negative buss bar to organize that spaghetti.

 

[VanKitten]

Weight.

Yeah...got that. Of course all the ground wires go thru a bus bar. (See my system description above). Just too many wires unless I consolidate. Then, from the "ground" busbar to the shunt.

Question is...where to run ground cable to chassis

If I attach it the busbar side of shunt... then nothing goes thru the shunt. So it seems to me that the ground has to be in the battery side of the shunt.

 

[John61CT]

Not really a ground, best to call it "negative return" as a reminder.

Large loads both positive and negative wires same gauge and length back to source.

Beware using "chassis" points, often on modern vehicles too much resistance, gets worse with age. Most devices where their metal case is supposed to be "grounded", it's not actually critical, chassis connection is OK for that.

Best main point to tie various negative busses together is the alt/starter/engine block nexus.

All the above is wrt to DC only.

AC circuit grounding is more complex for a van, and critical to get correct.