Tag Archives: Charging

Running on Light

The weather is getting colder and the daylight is getting shorter, especially with daylight savings time. The garage is a bit cold to work on the car. I’ve been staying inside focusing more on the solar system and some custom software I’ve written.


An inverter capable of charging the CitiCar

In my previous post, I ran into problems charging the car with a 1000 watt inverter powered by the lead acid batteries that came with the car. I went ahead and purchased a cheap inverter that was capable of continuously delivering 3500 watts.

The inverter had no trouble while charging the car. I thought it may only last a half hour at first, then an hour, and another hour… eventually Teddy and I had to take the car down to the Fireball Arcade. We had exclusive access while they were closed to play some games, show off the CitiCar, and talk about maybe driving it in the Christmas parade. The batteries in the car went from a 76% charge to 93%.

The charger had a draw around 850 watts for almost three hours. Ignoring the efficiency of the inverter, charger, EVSE, and working with ballpark figures, it turns out the batteries can store at least 53 amp hours each. However, keep in mind the batteries were still running fine when I had to take off. I may end up getting a capacity monitor for the battery bank as well.

inverter voltage120
watts (volts * amps)850
watt hours (watts * hours)2,550
battery voltage12
battery bank amp hours (watt hours / volts)212
battery count4
battery amp hours (battery bank amp hours / count)53

I have a few inverters now.

BrandSign WaveWattsSurgePer OutletDirectEfficency

There are a few things I’ve learned about inverters over the years.


The first time you connect the inverter to the battery, you’ll see and hear a spark. An inverter has capacitors that will fill up fairly quick. If you tap the wire against the post again, you’ll probably see that there are no longer any sparks.

It’s a good idea to have a switch to cut off the battery from your inverter. A switch is meant to handle these sparks. Not probable, but in a worst case scenario, your cable will be fused to the post, or you’ll have melted bits of metal flying into your eye.

When I disconnect an inverter from a battery, I usually turn it on afterwards to drain the capacitors. It will come on briefly and beep to warn you about low voltage. Afterwards, I turn it off again and set it to the side.


The watt rating is often misleading, representing a sum. My Sunforce 1000 watt inverter could only deliver 500 watts per outlet, and therefore would not allow me to charge my car with 850 watts.

If the inverter pulls more current than your batteries can handle, it may also appear that the inverter is unable to support its advertised wattage since it may shut off as a low voltage protection feature to prevent damaging your batteries.

You may want to tear your inverter apart and verify the wire to the outlet can support the amps needed.


Grounding is specifically used to protect your equipment from surges.

A receptacle tester indicating an open ground

Using a receptacle tester, some inverters will show that you’ll have an open ground fault. My Sunforce inverter showed that it was wired up correctly, even though I didn’t wire it up for grounding. The Cen-Tech and EDECOA inverters had an open ground fault.

Inverters will usually have a specific area to connect a ground wire to them, or to simply connect to the body. The EDECOA inverter simply says to connect it to the body and gives you a little grounding clip. The Sunforce inverter has a labeled screw on the back. The Cen-Tech inverter has nothing on it’s plastic shell that would be conductive.

Inverters are used in two places – vehicles and structures.

The rubber tires on a vehicle will cause too much impedance to reach the ground, so it’s often recommended to connect to a specific part or the body of the inverter to the frame of a vehicle – but only if its a negative ground. A vehicles frame is often connected directly to the car batteries negative terminal to cut down on the wires needed to be ran through a car.

For structures, you’ll often have at least one eight foot grounding rod driven vertically into the earth. You’ll often be connected from the inverter to the ground rod to lower impedance.

Sometimes it’s a losing battle trying to figure out how to ground an inverter. The EDECOA inverter was a head ache, and still boggles my mind. The only way I was able to get the open ground fault to go away was when I probed the ground and neutral terminal screws for continuity. I tried connecting my houses grounding rod to various parts on the inverter without any luck.

Sign Waves

AC (Alternating Current) electricity is provided by the utility company. The voltage flip flops between negative and positive, and shows up on an oscilloscope as a bunch of round hills. An inverters job is to convert DC (Direct current) electricity into the same wave form, at the same voltage and frequency.

Modulated Sign Wave

The cheaper inverters often generate a modulated sign wave. They are simple to make and don’t require much hardware. The signal appears to look like stairs going up and down – or outlines of 8-bit hills. The more steps you have, the better the inverter is for your equipment. However, not every modulated sign wave is a perfect set of stairs.

This can run things like motors in a fan, drill, table saw, and incandescent light bulbs. Unfortunately a modulated sign wave can damage electronic equipment such as computers and battery chargers.

Modulated sign wave from 400 watt CEN-TECH inverter

Pure Sign Wave

Also known as a true sign wave, this signal matches what a utility company provides. Your devices may depend on a pure sign wave that looks like smooth curves to regulate clock cycles, capacitors, and trigger events when various voltages are recognized. Inverters will use more components to smooth out the stair pattern into a gradual curve. Inverters that advertise that they offer a pure sign wave, may still appear to be stepped, but at a very refined scale.

Pure sign wave from 1000 watt Sunforce inverter
Pure sign wave from 3500 watt EDECOA inverter

How to choose

To avoid any potential problems, it’s usually best to go with a pure sign wave inverter, as that is what the manufacturer of your devices designed it for. If you are in a pinch, you may want to try the modified inverters. I would only recommend it if you are using simple equipment that doesn’t have a computer in it (power tools, coffee maker, incandescent lights). I’ve had electronics damaged from using the CEN-TECH inverter from Harbor Freight.


Rigol DS1054Z oscilloscope testing EDECOA 3000 watt inverter

I used a Rigol DS1054Z digital oscilloscope to capture the sign waves from each of my inverters. The lines appear “fuzzy”. I believe this is because my scope is not isolated from the noise on the houses AC power from the utility company.

Plug with terminal leads for testing

I also made my own plug to test the signal. I had an old plug from a battery charger that went bad. I stripped the wire and put male blade terminals on the end to prevent the two wires from touching themselves or me. I marked the hot wire (thin blade) in red electric tape. From here, I was able to connect my probe to the hot wire and attach the probes grounding clip on the neutral wires terminal.


It’s been a week, and my battery bank is still recovering. At first, I was using the solar panels to charge up my battery bank. I have a few things going against me.

Amorphous Solar Panels
  • 200 watt array
  • Amorphous
  • Approaching shortest day of the year
  • Moved about 350 miles towards the north pole
  • Area has shadows throughout the day
  • Bad vertical/horizontal angle & no sun tracking
  • A few days of rain and overcast
  • Long cord
  • Batteries are cool (60 degrees Fahrenheit)

I started to charge the battery bank with a 12v 4amp trickle charger when the sun is down. With MPPT, my solar panels can make better use of the voltage during the day.

Solar charger only reports charging via panels, but recognizes voltage increases

When the batteries were in the car, I could recharge them in eight hours with the same charger – but each battery in series had its own 12 volt charger. In this setup, I can’t hook up four 12 volt chargers in parallel.

Five trickle battery chargers for motor and accessories

I’ve adjusted the panels to draw more power from the sun, but I’m fairly limited in where they are located at the moment. I’ve ordered 500 watts of polycrystalline solar panels. On days with rain, I didn’t bother hooking up the panels and stuck with the trickle charger.

I’m a bit interested in how to track the sun as well as putting a shed in the back yard for the panels.

Erratic Temperatures

When I first started charging the battery bank, I noticed the charge controller was reporting temperatures that were jumping up and down on a graph.

The remote battery sensor starts jumping up and down overnight

Initially, I thought this was a result of the battery trickle charger being too close to the temperature sensor and moved it further away. It had no effect on the temperature.

After a little research, what I found out is that the signal from thermocouple temperature sensors are affected by coupling from AC power running along in parallel. Sure enough, as soon as I unplugged the battery charger, the solar charge controllers remote battery sensor went back to a strait line.

Noise from AC coupling has been reduced after movements

I went ahead and started moving wires around to see if I could remove the coupling. When I moved the heat sensor with my warm hands, it showed up as a peak since the garage is fairly cool this time of year. It gave me a good point of reference.

I was successful in reducing the coupling noise when moving wires perpendicular to each other. I went back and tried to improve the position of everything a second time, but I suspect that maybe the trickle charger itself is having an affect in the signal of how it charges, some coupling is getting through regardless if the wires are parallel, or works from a greater distance than I realize.

The good new is that I understand what is causing it, and that the temperature sensor is still fairly close to the temperature without affecting the charge controllers charging voltage.

Solar Pi

I’ve been taking a closer look at my old software and found that the real-time data was in a separate folder.

RS485 Logger and Wi-Fi devices

The first round of the software was working from a static CSV file that involved a manual process to retrieve the data and publish in the repository. The device was an eLOG01 and even had its own CR1220 backup battery.

Initially I tried a little device to let me access the data over Wi-Fi. The eBox-WIFI-01 device had its own Wi-Fi network to connect to. I ran into a few problems and ended up looking into other options.

Real-Time Logs

Raspberry Pi with battery backup connects to the solar charge controllers data port

The next round made use of a Raspberry Pi and connecting to the data port via RS485 using the modbus protocol. I then started polling the controller every minute and saving its settings to a MySQL database.

It’s this website that I’ve been monitoring quite closely with temperatures and power with the load, pv array, and battery. The only issue is that I keep modifying the code to show the last hour, three hours, and 24 hours. I need to setup the interface to give me an option to do this within my browser.


The battery tab lets me see how the trickle charger is doing compared to the solar panels. I was debating if I should keep the trickle charger on during the day instead of plugging in the panels. It looks like the panels are a little better than the charge controller.

Battery voltage and charging graphs over the past 24 hours


The load tab lets me see the draw of power by devices connected to the charge controllers 12 volt power supply. The charge controller can be configured to turn the supply off based on the current time, or the sun has risen/set. The raspberry Pi was powered by a usb port from this power source in my original configuration.

With my LED Christmas lights draining a 50 ah wheel chair battery overnight a few years back, I hooked the Raspberry Pi up to a 6000 mAh Jackery Portable Travel Charger as a backup solution. Once the loads power is cut off, the Raspberry Pi is still able to read information from the controller such as how low the battery is, and associated warnings before/if the controller shuts off.

Once this USB battery was connected to the load, I could see its effect on the load. It draws six watts briefly about once an hour, and then it draws six watts over two and a half hours once a day.

Load discharge graphs over the past 24 hours

If you look at the voltage, you’ll notice it also drops a little for a brief moment every hour as well, as it’s tied directly to the battery voltage lowering during its draw.

I’m debating if I should upgrade to a higher voltage battery bank so that the load will have a consistent 12v power supply that does not decrease as the batteries are discharged.

Solar Array

Lately, I monitor the solar array to determine if I should switch over to grid power to continue charging the battery bank. I can set it up to show me how the panels have been doing over the past few days. I’ve been pulling 55 watts at most on a 200 watt system. Notice the peak on the third day is much thinner. I had left the solar panels disconnected in the morning due to rain until things cleared up.

With the low wattage and a larger battery bank then when I first setup the system, I decided to purchase some new panels.

Solar panel power generation graphs over the past five days

Usually I’ll flip between the battery, load, and solar tabs to review where the watts are coming from, and where they are going. I’ll need to setup something that’s a bit more easier to compare the information I’m looking for.


Currently I modify settings on the controller with a device called an MT-50 Remote Meter. I end up removing the raspberry pi data cable and losing track of data while I’m plugged in.

I’ve started working on an editor to modify the settings directly through the raspberry pi website. I’ve got most of everything working to read the data and display lookup lists and input boxes. I’m on the cusp of the actual goal to send write requests to the solar charge controller. The new setup is pretty powerful.

MODBUS interface to configure EPsolar Tracer4120A charge controller


Solar EVSE

With the old CitiCar batteries laying about, I decided it was about time to embark on a side project to charge my CitiCar with the power of the sun.

Three years ago, I started a little off-grid solar project. I already had everything tucked away in the garage. I brought everything out and started connecting the batteries in parallel, and then to the inverter.

I did a test and verified I could use the inverter to plug things in and power them on. It was only 1000 watts, but I decided to attempt to charge the CitiCar. The inverter started beeping and stopped supplying power.

I thought there was a chance of that happening. It looks like I’ll need an inverter that can supply a minimum of 1800 watts with 15 amps.

Solar Panel Array

I continued to setup the solar charge controller and the solar panels to start charging the battery bank. I had trouble getting the 8-way splitter to work, and ended up using two 4-way splitters to connect seven of the eight panels.

The last part was to connect the Raspberry Pi to log data. I was able to get it up and running on the network over wifi and view the dashboard.

Dashboard of various measurements that the raspberry pi collected from the solar charge controller.

Unfortunately, I couldn’t see any data since the last time I had the system up and running. I was able to update the date in the charge controller, change the time-zone on the raspberry pi, and confirm that data was being saved into the MySQL database.

It turns out that the code that I had written was in its alpha stage while experimenting with the data being returned. It looks like I was using a separate logger to grab CSV files, and then hard-coding the website to load from them instead of the database.

In summary, I need a more powerful inverter, and I need to wire up the website to a website.

Solar EVSE Charging Station – Part 1


After reviewing a few old videos that I had made demonstrating the solarpi website, I found that I was looking at an older interface. The newer interface is wired up to the database and keeps updating itself to show graphs of the last hour of data for each gauge. In addition, the gauges have colors to indicate ideal areas that the needle should be in. The site still needs plenty of improvement as well as a way to view and compare history.

In other news

The current AiLi battery capacity meter keeps resetting to 0% during my drives. I think it’s due to a loose wire on bumpy roads. As a temporary backup solution, II wired up a previous voltage monitor that gives me a percent and graph based on voltage.

The garage is dark. Both lights have now burnt out.


Dragging Wire

Someone warned me that the wires were hanging from the bottom of the CitiCar when I drove up to a car show (that was canceled) on the weekend. They offered a zip-tie, but I thought I had fixed it by pulling up the wires and rearranging the batteries by time they came back with it. Unfortunately, I should have taken them up on their offer. I noticed the wire had been dragging against the pavement. It’s time to get serious on changing over the powertrain.

Wire exposed within 2/0 battery cables from dragging on asphalt

There are a few reasons why this is happening now. The first is that the speedometer cable had been removed, which prevented the wire from going below the motor. However, the latest change was the most impactful. I had installed the motor controller and contact switches. In doing so, I moved the batteries and their wires out of the way so I could get into the area easier. I have the wrong batteries, so there is plenty of room. I think they are moving around while driving, and the motor cables just move along with them.

This is a serious issue. The cables need to be repaired immediately before I drive the car again. It’s questionable on how much of an impact this will have on the amount of amps that the wire can handle now that it’s lost some copper. There is another concern that when driving in parallel, one set of batteries will have less resistance because it has a bigger “pipe” for electrons to flow through.

The new power train is going to be a tight fit, so this will not be a problem afterwards.

Custom Cables

Now that the motor controller and contact switches are installed in the CitiCar, I started moving onto wiring them together. The wires I had were either too short or a bit too long.

I started creating a custom cable. I’m not sure how good my crimp is, so I kept crimping the lug multiple times until the whole length of it seemed to have been crimped. Luckily, I realized that I needed to get some heat shrink before crimping the next lug.

Big tools to crimp big wire terminals
A battery lug that has been crimped one too many times

Teddy and I took the SUV over to the local hardware store tonight. A pack of 5/8″ heat shrink has two tubes that are six inches long. The instructions said to add two inches to the measurement to handle the 4:1 shrinking ratio, so I picked up four packages.

The heat shrink didn’t really shrink that much in terms of length. It seems like I could have gotten away with much less slack. My custom wire looks a bit more professional – to me.

A custom 2/0 battery cable with right-angled terminals and heat-shrink tubing

After the battery cable cooled down, I installed it into the CitiCar to connect the motor negative terminals between the motor controller and the reverse contactor switches.

Custom cable connected to motor controller motor negative (M-) terminal
Custom cable connected to SW202 motor reversing switch motor negative terminal M-
Installing my first cable

Charging Cycle

I got a charge cycle that stopped due to an over-voltage fault. The high voltages at the end of the charging cycles are fairly concerning. After exhausting the CitiCar batteries on a long trip, I kept a fairly close eye on a full charge cycle, recorded the data, and made a few charts:

TimeMin RemainingAmpsAmp-HoursVoltsSoCPhase
9:3479820.9051.020%Phase 1
9:4580320.6451.720%Phase 1
9:5978920.4952.221%Phase 1
10:1377520.21452.723%Phase 1
10:2676220.11853.225%Phase 1
10:3575420.02153.525%Phase 1
10:4574619.82453.826%Phase 1
10:4974019.82654.127%Phase 1
10:5673219.62854.628%Phase 1
11:0272719.43055.029%Phase 1
11:1071919.13255.829%Phase 1
11:1771218.73557.330%Phase 1
11:2435711.93757.473%Phase 2
11:2735510.23757.473%Phase 2
11:312009.03858.289%Phase 3
11:341989.03860.989%Phase 3
11:371949.03964.790%Phase 3
11:411909.03966.190%Phase 3
11:451869.04066.990%Phase 3
11:501829.04167.390%Phase 3
11:541779.04167.690%Phase 3
11:591729.04267.991%Phase 3
12:051679.04368.091%Phase 3
12:091629.04368.091%Phase 3
12:141589.04468.191%Phase 3
12:191529.04568.192%Phase 3
12:24149.04668.192%Phase 3
12:3279.04768.092%Phase 3
12:4000.04855.8100%Not Charging
12:5400.04854.1100%Not Charging
1:0300.04853.9100%Not Charging
1:1000.04853.8100%Not Charging
1:2700.04853.7100%Not Charging
1:3600.04853.6100%Not Charging
2:0400.04853.4100%Not Charging
The state of charge always jumps by 50% in a short period of a few minutes during phase 2
Estimated time remaining is always off by about 400%
Phase 2 appears to be a very abrupt cross-over compared to charging profiles for lead acid batteries around the internet

Over Charging

The charging voltage maxed out at 68.1, each 12 volt battery got up to 17 volts. I hadn’t gone up past 14.5 with regular car chargers in the past. It seems as if the batteries are being overcharged. If they were being equalized/balanced, it would make a bit more sense. This is during the final phase after it reaches 90% charge.

Exaggerated Estimates

The initial estimate was 13 hours and 18 minutes, where the actual charging duration was three hours and six minutes. As the charger progressed through each phase of the cycle, it was getting better, but still highly exaggerated. The device is not learning from its previous charges.

Huge SoC Gains

The state of charge is sometimes abrupt. The state of charge increases gradually until it is at 30% charge at 57.3 volts. Seven minutes later, the battery state of charge jumps to 73% at 57.4 volts. Another seven minutes and we are at 89% charge at 58.2 volts. We then grow gradually up to 92% over an hour, and then jump directly to 100%.

Short Phase 2

Phase 2 is a very short cycle, that is 20 minutes at most. The cross over between dropping amps and increasing reported SoC by 50% is very sharp.

Charger Conclusion

It seems like the Lester Summit Series II charger may be defective or had the wrong battery profile. The CitiCar has four 12v Interstate 31-ECL in series. The battery profile (22001) description seems fine other than the amp hour rating. When I called up the manufacturer, the amp hours (190 RC@25 amps) wasn’t a problem and I was told that the default profile was fine.

  • Single-voltage mode: 48V flooded/wet lead-acid battery packs with a 20-hr rating of 225-260 Ah
  • Auto-voltage mode: 48V, 36V, or 24V flooded/wet lead-acid battery packs with a 20-hr rating of 225-260 Ah
  • Profile parameters: 22A bulk (48V), 25A bulk (36V), 25A bulk (24V), 2.39 VPC absorption, 9A finish, Progressive DV/DT termination, equalize active

I wish the charging status was more descriptive rather than saying “Phase 1”, “Phase 2”, and “Phase 3”. The phases do not convey any information. It would be more useful to see something like Desulfation, Bulk, Absorption, Float, and Equalize.

Capacity Monitor

The capacity monitor arrived. This was one of the last major components of the new system that I had been waiting for. It was fairly simple to setup and I started getting feedback immediately on the amount of amps the CitiCar motor uses when initially starting or going up hills and cruising.

It seems to go around 250 at most, but occasionally has small spikes at 350. Cruising appears to be around 125 amps. I’ll need to put a camera on it while driving to look back later to get a more accurate reading of data.

One special thing of note is that I’m now aware of how much phantom power is being drained. The battery charger and capacity monitor both consume a small amount of amps.

The capacity is not useful for driving at this point because the detected voltage keep swapping between 24 and 48 volts. Once I upgrade the CitiCar to always use 48 volts, the capacity should become useful. However, it does appear to be fairly accurate reporting the same number of amp hours that the battery charger reported.

The capacity monitor is more precise on the number of amp hours supplied by the charger
AiLi Voltmeter in CitiCar