I am doing some upgrades on a customer’s brand new Keystone 5th wheel. It came from the factory with a Smartshunt and SmartSolar 100/30 along with 440 watts of solar on the roof. I am adding another 380 Watts of solar, MPPT, and LFP batteries.
The problem is the shunt isn’t recording all the charging amperage coming in from the solar.
I can start with all loads off and the shunt shows -.05 amps.
Turn on the solar and its charging at 12 amps. But the shunt is only showing 8 amps. Turn off the solar and the shunt goes back to -.05 amps.
I did all the obvious stuff. I have verified that ONLY the battery negative is connected to the battery side of the shunt and nothing else. I have verified NOTHING is connected to the battery but the shunt cable. I have disconnected the loads from the shunt and did a zero calibration.
I also have the MPPT and the Smartshunt networked.
My next step tomorrow is to verify good chassis ground and perhaps upgrade the cable from the MPPT to the battery bus bar. The MPPT cables do go to a factory installed switch with integrated bus bars. I’m thinking of bypassing this completely and going directly to the battery bus bars.
I recall one case on here a good while ago where there was a parallel negative path to the battery through the chassis and the chassis grounds. I can not recall the detail must have been a chassis connection to the battery but you said you have checked.
Another thought if the starter battery is common negative, is there anyway some of the charge from the MPPT is ending up there, VSR, trickle charger.
The chassis grounds are a mess. From the factory shut off/bus bars the negative side goes to chassis ground and then from there back to the shunt load side. The MPPT and other loads are on this bus bar. Also they don’t appear to be attached to the chassis as thoroughly as I would like. Theoretically this should be working but I am going to put in my own bus bar, run a big cable to the load side of the shunt and then run the MPPT to it rather than relying on the messy, questionable connection at the frame of the rig. Then I will make my own chassis ground from the newly installed negative bus. At least this will ease my mind about the poor job done from the factory on the chassis ground side.
Missed the 5th wheel bit, not on my radar in the UK.
OGPS
(Ed @ Off-Grid Power Systems - offgridps.com)
5
I was talking with one of our new dealers the other day and he told me of the very poor chassis bonds they see even on high-end Class A motorcoaches. I tell him we see it all the time on RV’s that come into our shop. The RV OEM’s seem to think a simple star washer is enough. I told him we grind down a spot on the frame (that is welded to other frame members, not just bolted) and bond using a tin-plated copper lug with some NoOx or carbon conductive paste between them and then a heavy welding cable to a bonding point on the Lynx system. However, we don’t chase down every bonding issue already present on the coach. The more rocks you turn over the higher likleyhood of encountering a snake underneath. Sorry, that was the best analogy I could come up with
Well, I disconnected the main chassis ground that I could see. It was pretty suspicious. A bunch of large cables bolted to the powder coated frame with a star washer. In fact the bolt threads were stripped.
I installed a bus bar, installed a cable to the load side of the shunt, installed all the MPPT and other present load negatives to the bus bar. I then ground down a spot on the frame to bare metal and installed a new chassis ground to the bus bar. Still the Smartshunt is not recording all the charging amps. The batteries I installed have Victron comms so after talking it over with the client we decided to set the BMS as the battery monitor and abandon the smartshunt, as apposed to chasing down more elusive issues. We planned on using the batteries as the battery monitor anyway I just really wanted to find the issue for the customer.
Its really sad that this is a brand new rig. Problems like loose and messy connection abound. Two plumbing fittings in the basement where visibly leaking. I was able to tighten them up. But come on, seriously? The more I looked the worse it got.
You guys should do it like a final acceptance test of an airliner before deliver/flying it to the customer!
Turn over every rock, open all doors, cabinets.
Count the snakes you found and set a time frame to remove them (for the reader, the snake stands for a bug or problem, e.g, leaking pipes, jamming doors,…).
Zero current calibration?
Is the mV set correctly? Can you set that on a smart shunt?
Usually though the assumption would be when a solar is producing 12amps and its not all reaching the battery a load is using the missing 4amp part. But i guess ot in this case.
Even a zero current calibration doesn’t make sense if that is accurate.
OGPS
(Ed @ Off-Grid Power Systems - offgridps.com)
9
Customers can be quite cheap and unwilling to spend money for things like this. We’ll do what’s needed to make the power systems we install function correctly and charge more for unexpected or out of scope repairs needed to do so. And, we’ll alert the customers to other issues we noticed along the way. Sometimes they’ll ask us to remedy the other issues, but often they choose to deal with it themselves. You learn a LOT about a person when money is involved.
OGPS
(Ed @ Off-Grid Power Systems - offgridps.com)
10
A couple of years ago we took in a new Solitude. The customer wanted the system installed in the pass-thru storage compartment rather than the front compartment. When we opened up the false wall and exposed the front landing gear we saw sticky pink goo everywhere. From the factory, the hydraulic lines had been spraying hydraulic fluid all over the compartment. Yet they claim every unit that leaves the factory undergoes extensive pre-delivery testing. Riiiight.
Of course the manufacturers could spend more time to build a quality product, but there is a cost to that and, well, see my other post about customers being cheap. It’s not a business modeI I can accept so I probably won’t be building RV’s in this lifetime
I agree, zero shunt calibration didn’t make sense but I was grasping for straws at that point. -.05 amps with loads off is pretty normal in an RV where there are things that are always on despite the main house power being disconnected. A smoke detector for example.
The full charge of 12 amps is reaching the battery. It is clearly going to the batteries and can be observed on the GX touch. Its just the shunt is not seeing all of it. If there is a mV setting for a SmartShunt I don’t know where to find it.
If I posted a picture of the wiring on this rig you would say, “Of course something is wrong”.
All is running well, DVCC is enabled, the battery is set as the battery monitor. SmartShunt is a glorified bus bar at this point. The customer is thrilled.
