Is there an electrical question you have been afraid to ask? Type it below and a real Electrical Engineer will answer it and post the response below.

6/20/2022

Question: I saw in your FAQ that your systems don’t incorporate a ground connection. Can you explain why? I’m seeing a lot online that grounding to a van chassis is essential. Is that not the case?

Answer:  It doesn’t hurt to ground the frame of the inverter to the chassis of a vehicle, but in order to create a situation where the lack of that connection created a dangerous scenario, you would have be knowledgeable, creative, and malicious. When you are sitting on rubber tires, the need for this connection is greatly diminished.

9/1/2020

Question: The Digital Multicontrol, is this required for all multiplus/quattro applications? If a customer wanted to only use a bluetooth dongle, what would they be missing from the digital multi control? I would assume the current limiter is the most important function of this?

Answer:  You need the Digital Multicontrol in all systems using Victron lithium batteries.  If you are using other lithium batteries, you can do without it and use just the Smart Dongle, Cerbo, Venus, or CCGX.  With Victron lithium batteries you can add the Cerbo, Venus, or CCGX.  Yes, it is confusing.

7/31/2020
Question: Does a shunt based battery monitor’s State Of Charge percentage tell you how much is usable, or total?  For example, you aren’t supposed to go below 50% SOC on a lead acid battery.  At that point, will the monitor show 50% or 0%?
Answer:  It will show 50%, because technically you can go deeper, you will just harm the battery.

4/22/2020
Question: Assuming you want to connect 8 Lithium cells in series to get a 24v battery. Since the voltage increases between each battery connection, for example 12v at midpoint, can the cable size be decreased in each cell connection down the line as your bank increases in voltage?
Answer:  No, voltage isn’t a point measurement, it is the difference between two points, so our calling something 0V is just arbitrary and it only means it is 0V from the chassis.  It may be 24V from another point in the system.  Also, the cables are sized to handle current, and the same current would flow through every cable.  Also, a little more challenging to wrap your mind around, but the same voltage would be driving that current, no matter where you were in the system.

4/13/2020
Question: If I have 2 awg THHN cable in a 2.5 foot run from battery to inverter, and I have a 2000 watt inverter (~170A draw), is it really a problem that the ampacity of the cable is rated for 130A? Should I use the higher value for a breaker, or the lower one? What's the worst that could happen if I use a 170A breaker? Would the cable really blow first?
Answer: It would probably work, but I wouldn’t attach the AM Solar name to it. We recommend 2/0, not 2ga for 2000W inverters. If you only use <1500W of that invert you would be fine, but we can’t guarantee that our customers would do that. I would use a 130A breaker on that setup.

3/11/2020
Question: I've heard of customers getting more than 100% of a panel's wattage when conditions are perfect. Suppose you are in ideal conditions with peak sun, in a valley with snow reflecting down, mirrors pointed at your panel (etc etc). What is the maximum wattage a panel can produce above it's rating in more-than-ideal conditions? Is this something that can be calculated or is in any way consistent, or is a function of the panel manufacturer's quality?
Answer: It would be limited by the panel’s ability to handle heat.  If you mounted the panel on a spaceship and flew toward the sun the output would increase until the panel broke down due to heat or in the case of Zamp panels, the fuse blew, which is rated at 10A or 15A depending on the panel.  Solar output is directly proportional to irradiance and the temperature coefficient, with the rating being based on 1000 watts per square meter at 25 degrees C.  If you get 1200 watts per square meter and the panel is 25 degrees C, a 100W panel will give you 120W of output.

3/11/2020
Question: In your previous answer to the VA versus W question, the question asks, "Why is the VA number always less than watts?" Actually the VA number is usually more than the rated continuous watts. Given the math discussion and the various load-types of appliances, the tell might be in the Peak Watts Rating of the inverter in question. However, if there is no time element stated, is it safe to say that the inverter can only hit that Peak Watts Rating for a few milliseconds before failure or cutoff?
Answer:  I had watts and VA switched in the previous response.  I think I have it corrected now.  This has nothing to do with surge rating.

3/10/2020
Question: Why is the VA number always less than watts? Which one is proper to refer to when discussing inverter sizes?
Answer:  VA stands for Volt-Amps, and volts x amps = watts, so basically, they are VA and W are the same thing.  But here’s where it gets tricky.  When you are dealing with AC power, the volts and amps cycle up and down 60 times per second.  If you have an inductive load (heater) or capacitive load (brushless motor) the Voltage peaks will not always occur at the same exact instant as the Amperage peaks.  The difference in peak times is measured as the “Power Factor”.  If a load is purely resistive, it will have a power factor of 1, meaning all the power is “real”. A capacitive or inductive load creates a perpendicular vector to the magnitude of real power.  Apparent power (measured in VA) is the hypotenuse for the triangle formed by the real and reactive vectors.  Real power (measured in Watts) is always less because the side of any right triangle is always shorter than the hypotonus.  With most loads, the average ratio of Real to Apparent power is about 80%, not so coincidentally, 1600 / 2000 = 0.8.

The concept of Power Factor can take you into some crazy math using imaginary numbers like the square roof of negative one.  This is significant, because when you square any number, positive or negative, you always end up with a positive number.  So, the square roof of a NEGATIVE number is impossible, but somehow the math works out and it explains Power Factor.  To learn more, try digesting this:  https://en.wikipedia.org/wiki/Power_factor

3/09/2020
Question: Can we use the Color Control GX with a non-Victron brand inverter or non-Victron brand charge controller?
Answer:  The CCGX will not communicate with non-Victron inverters.  But, if you were weird, you could put in a system and have it just talk to your charge controller and battery monitor.

2/28/2020
Question: What's the difference between amps and amp-hours, and watts and watt-hours? I've never heard of volt-hours. Does that exist too?
Answer:  Amps is how many electrons pass through a plane at the measured instant.  Amp-hours is how many electrons pass through a plane over a given period of time.  Watts is those same amps multiplied by Voltage, which is the pressure driving the electrons.  Watt-hours is those same amp-hours multiplied by the voltage.  There is no such thing as volt-hours because voltage is just a force, not something moving that can be measured or summed as the quantity of something.  An Amp is a flow rate one coulomb per second.  A coulomb is 6.241 x 10^18 (or 6,241,000,000,000,000,000) electrons.  An Amp hour is 3,600 x 6.241 x 10^18 = 2.247 x 10^22 electrons moving through a plane.

2/26/2020
Question: Suppose I have a 350W appliance to power. A fully charged Battleborn at 13.7v would require 26A to power the load. Does the current draw increase to over 28A as the load continues to pull power and the battery voltage decreases to 12.5v? W=A x V
Answer:  If a load draws 350W exactly and continuously, it’s power supply will draw current at a rate that maintains the P in the P = V x A formula (Power = Volts x Amps).  In other words, if the battery voltage drops, the current will have to increase to keep up with the wattage demand.  It doesn’t matter what type of battery is being used.

2/26/2020
Question: Are your solar panels rated for a marine environment?
Answer:  The Zamp panels that we sell are not marine rated, but if we found a good deal on marine rated panels, and there was a market for them, we might sell them.

2/25/2020
Question: Why don't we use marking paint on nuts and lugs? Shows when they have been tampered with.
Answer:  This would be a better question for the Installation Manager, but my thoughts are:  We could, but if we did, would that information be very useful?  I don’t know of many people that monkey around with their systems if they work properly.  Even if they did, we should be able to tell them what they did wrong.

2/24/2020
Question: I have two 100W panels and two 170W panels. Can I wire a 100W panel and a 170W panel in series parallel or do i need to keep the 100W and the 170W in their own series pairs. Why?
Answer:  Assuming all the panels have a similar Vmpp, they can all be connected in parallel.  The only other option would be series pairs, with the 100W panels in series, paralleled to the 170W in series.  You can’t put a 100W panel in series with a 170W panel because they have vastly different Impps.

2/24/2020
Question: A guy on the internet said that current actually flows from ground, negative to positive, and that all our diagrams are backwards. Is this true?
Answer: In the early days of studying electricity scientists had no way to tell which direction electrons actually flowed and they just arbitrarily said they flowed from positive to negative.  Later, it was discovered that electrons flowed from the ground to the positive, but by then it was too late to change everything.  So, there is a compromise, “positive electrical current” flows from the positive to the negative, but negatively charged electrons, flow from the negative to the positive.  In summary, the guy on the internet is half right, but he is also a dork, and we shouldn’t change our diagrams.

2/19/2020
Question: Without becoming an EE, how much electrical theory does one need to know in order to successfully install your kits, and understand how it operates? Further, can you recommend any online courses or videos that teaches basic electrical theory?
Answer:  I don’t think an EE degree is very relevant.  School was mostly advanced math, like calculus and differential equations, which I haven’t used since I graduated.  I don’t even think an Associates degree or any community college classes will be relevant either.  When I graduated, I felt like I didn’t have any real-world skills, so I became a Financial Advisor.  The best thing you can do is start reading here:  https://amsolar.com/diy-rv-solar-instructions/edterminology and go through all the education pages.  Take notes and ask lots of questions.  For example:  What does this part do?  What would happen if I wired it backwards?  What would happen if I shorted it out?  What would happen if I left it off?  What does the programming make it do differently?  Also, get an Instagram account and follow @otgcamper.  I learn a lot from him.

2/18/2020
Question: Why aren't any motorhomes equipped with DC generators like the ones found here, would it be unrealistic to have one custom installed knowing you will have a large solar system? Do any motorhome manufacturers let you choose the genny, or are the fallbacks of not having 120V power on-demand simply too much?
https://polarpower.com/products/dc-generators/8220k-972/
Answer:  I don’t know why someone would want a DC generator, when they already have solar and an alternator.  Most DC loads don’t draw nearly the wattage that AC loads draw.  Air conditioners, microwaves, blenders, etc. all need AC.  A DC generator isn’t going to be helpful for them.  Although I don’t know much about the RV buying process, I imagine they don’t give customers a lot of choice. 

2/18/2020
Question: When series connecting panels, there seems to be some confusion about how best to pair panels in a series configuration. Does the Vmpp need to be close to each other, or does the Impp need to be close to each other, or both?
Answer:  Parallel is to Vmpp as Series is to Impp.  When you parallel panels you want to keep the Vmpp within about 3V (e.g. 18V & 21V).  When you series panels you want to keep the Impp close.  Voltage (Vmpp) is proportional to the number of series connected cells in a panel.  Current (Impp) is proportional to the size of the cells.  For example, you would not want to parallel connect a 60 cell residential solar panel (30Vmpp) to a 36 cell RV solar panel (18Vmpp).  You also would not want to series connect a 170W (Full 6” cells) to a 90W (Half 6” cells).

2/17/2020
Question: Can a lithium battery deliver it's rated peak discharge when drained past 50% SOC, or does it's peak discharge rate decrease with State of Charge?
Answer: As far as I know, the SOC has no impact on maximum discharge current.

2/17/2020
Question: How much voltage should I expect to see from any given solar panel?
Answer:  It depends on temperature, the number series connected cells, and how much current is flowing.  For open circuit (no current is flow), on most panels we deal with, I would expect to see 20V-25V.  Residential solar panels are around 40V.  If you see one of our panels at around 18V, that means current is likely flowing. 

2/17/2020
Question: Can you effectively measure midpoint voltage if there are only two 6V batteries in the bank? 
Answer:  Yes, use the BMV-712.  Instead of using a temp sensor, use the port that would have had the black wire from the temp sensor and connect that to the midpoint on your 6V battery bank.  You will need to program the BMV-712 to read this.