I'm tired of unreliable 'all in one' systems to power my fridge!

[mikefitz]

SmartSolar MPPT 100/50 charge controller does not monitor the battery state of charge

Agreed it does not indicate the SOC, but it records the duration of charge, absorbtion and float for the day. With the low charge currents of the proposed system, by the time the battery reaches absorbtion volts, 14.2 default value, and drops to float, you can be quite confident the battery was virtually fully charged .

PWM solar charge controller will work better for you than an MPPT one

Not with the 200 watt , 48 volt panel the OP has already mounted on his vehicle.

 

[wheelman55]

This doesn’t need to be complex.

I’ve had ARB fridges (similar to Dometic) for 12 years now. The fridges are on their own battery.

If I’m driving a lot this battery gets charged by the vehicle’s alternator.

If I’m not driving, the battery gets charged by a ZAMP folding solar panel that has a PWM charge controller. Renogy markets similar units to ZAMP.

The battery charges while you drive to camp. When you get to camp you unfold the panel/controller, put it in the sun, attach it to the battery and you are good to go.

I’ve been stationary for weeks at a time with this setup. 100% reliable.

No need to reinvent anything.

Keep it simple, use quality components and it’ll be reliable.

 

[HarryN]

Agreed it does not indicate the SOC, but it records the duration of charge, absorbtion and float for the day. With the low charge currents of the proposed system, by the time the battery reaches absorbtion volts, 14.2 default value, and drops to float, you can be quite confident the battery was virtually fully charged .


Not with the 200 watt , 48 volt panel the OP has already mounted on his vehicle.

Yes I assumed that it would be tossed because more or less nothing is working.

200 watts is not going to be enough anyway at the Pacific coast.

 

[MrNatural22]

If you let lead acid sit for several hours yes.

LFP in the working range is especially inaccurate between 40 and 70% SoC. If you're okay with the uncertainty zone of 40-70%, then it's fine.

Maybe I'm being a little pedantic, but saying something "monitors SoC" means that anything that can measure voltage monitors SoC. I just can't accept that.

I have always used this chart for a general
12v lifepo battery SOC or capacity.
Is there a difference?
I could be wrong.
Of course I do realize these voltages don’t count if Battery is under load.

 

[sunshine_eggo]

I have always used this chart for a general
12v lifepo battery SOC or capacity.
Is there a difference?
I could be wrong.
Of course I do realize these voltages don’t count if Battery is under load.

View attachment 210418

Nothing wrong with the chart, but as you state yourself, not accurate if under load.

Voltage is a means of approximating SoC that requires:

1) stop using system
2) let voltages settle for about 15 minutes
3) read voltage
4) look up approximate SoC on a chart.

In a lot of cases, this is fine, but it's misleading to say a device that requires the above "monitors SoC"

Monitor SoC = a live SoC value calculated based on Ah used and Ah capacity, accurate under load or charge.

 

[RV8R]

Thank you. can I ask for a few points of clarification?

When you say "A major benefit of the shunt is that it will share the voltage, current and temperature (if probe is installed) data with the MPPT" are you referring to the benefit of using the Victron Smart Shunt and Smart Solar MPPT controller together? And that the MPPT controller will automatically utilize this information to perform better?

When you say "Furthermore, your supply must be able to meet the maximum output power of the MPPT, or it will overload." do you mean that if I decide to implement DC charging from my vehicle's alternator using a step-up converter, that I need to make sure that it can supply the full 15 amps that the MPPT controller is rated to, and if not, it will blow the fuse on that 12v accessory circuit? If so is there a simple way to limit the current draw? (probably not, since it would be using the same inputs on the MPPT controller as the solar panels)

When you say "Additionally, you could not have it connected connected to the PV ports with the panel/array." are you referring to the inputs from the 12v accessory circuit/step-up converter? (they cannot be wired to the same connections on the MPPT controller as the solar panel inputs?)

Thanks again!

The Victron Solar chargers & Battery Monitors that can be networked & are Bluetooth work really well together.

Here is a screen shot of what they look like together on my phone;




I prefer the BM 712 Smart over just a “smart shunt”. There are more capabilities for a few dollars more.

 

[Dave911]

I have a BougeRV refrigerator/freezer in my car. I have been out of town 5 days a week for over a year, so having the fridge in the car is a an easy way to move food around without worrying about ice and water leaks, etc. Ice coolers are a giant PIA when traveling a lot. The fridge works great and has been running non stop since last October.
I run it off a 100ah, 12 volt LIFEPO4 battery which is tied to the car battery with some added circuitry. An isolator, a low temp protection thermostat, fuse, etc. The wiring from the car battery is 10 gauge THHN protected by a 30amp automotive fuse. It has never blown. The cars alternator outputs over 14 volts so keeping the battery charged has not been an issue with the isolator. Attached is an electrical schematic setup. The I bought the isolator, thermostat and relay off Amazon. You can find the items via the descriptions on the drawing.
I have the isolator screwed to the inside lid of a marine battery box. The Drok thermostat and the relay all fit into the box as well.
The refrigerator is connected directly to the LIFEPO4 battery terminals. If the battery runs out of power, the fridge shuts down on low voltage.
The cutout voltage on the refrigerator is adjustable. It all works well together.
See the attached drawing in PDF format.
If you add a solar panel/s and solar charge controller to this setup, it would just be better.
I just don't have a practical way to add a solar panel to a Lincoln MKZ sedan.

 

[featherlite]

I just don't have a practical way to add a solar panel to a Lincoln MKZ sedan

if you wanted to, you could add a trailer hitch receiver to your Lincoln, and mount a solar panel to a bike hitch rack. You would be the only guy in town with a solar panel mounted on a Lincoln.
A purple velour suit would also be a nice touch!

https://www.harborfreight.com/two-bike-hitch-mount-bike-rack-63924.html

 

[0truck0]

You would need additional help/instruction with this but... you already have a battery. Can you strip the unit down and use the battery out of it as just a battery? That saves you lots of money. Sounds like you have several batteries, or did you sell the older units?

If 100 amp hours works 4-5 days then it works 4-5 days and is enough, dont go more battery just bc somebody says you need to.

If you go 4-5 days on one charge, then either pwm or mppt will likely work as each day you will get some sun to put amps into battery. How many days you need to go without sun or cranking motor?

A dc-dc charge controller is another option, probably mentioned already, and protects your alternator, but I like the all-in-one charge controller that can handle two sources. Keep in mind, a battery can be charged by two or three+ charge sources at the same time and that is perfectly fine.

Check the solar panel for what the peak voltage is. On many 12 volt panels the peak is 18 volts, 24 panels 36 volts etc, so this info is needed when shopping for a charge controller so you get the right one.

 

[Dave911]

if you wanted to, you could add a trailer hitch receiver to your Lincoln, and mount a solar panel to a bike hitch rack. You would be the only guy in town with a solar panel mounted on a Lincoln.
A purple velour suit would also be a nice touch!

https://www.harborfreight.com/two-bike-hitch-mount-bike-rack-63924.html

View attachment 210479

I seriously thought about putting a panel on the roof. But my wife thought I was nuts ( its possible ). I admit, it might detract from the car, plus they would likely turn me away at the automatic car wash.
Truth is, if I drive the car 45 minutes per day, the alternator keeps the battery charged. If I dont drive it for 3+ days, I plug in a 4amp charger that is kept in the car. So really, a solar panel is not needed for my uses. I did consider some way to make a retractable solar panel that slides into the trunk when not needed. That may still be an option if my driving patterns change. Or maybe glue a flexible one on. So many options.
Purple Velour: I prefer dark blue.

 

[HarryN]

I seriously thought about putting a panel on the roof. But my wife thought I was nuts ( its possible ). I admit, it might detract from the car, plus they would likely turn me away at the automatic car wash.
Truth is, if I drive the car 45 minutes per day, the alternator keeps the battery charged. If I dont drive it for 3+ days, I plug in a 4amp charger that is kept in the car. So really, a solar panel is not needed for my uses. I did consider some way to make a retractable solar panel that slides into the trunk when not needed. That may still be an option if my driving patterns change. Or maybe glue a flexible one on. So many options.
Purple Velour: I prefer dark blue.

Maybe the solution is to buy a navigator or Transit so that there is room for solar panels.

 

[Ruff]

You may want to look at this Jeep option from Cascadia 4X4. I have the 100 watt solar panel and MPPT charger for my Land Rover and it has been running a Snomater 65L fridge at 34 degrees F 24/7 for nearly 2 years. The SUV is driven 2-3 days a week (maybe). I am using a second AGM battery in parallel with the main battery with a Traxide Aux battery kit in the engine compartment. I want to use LifePo batteries but engine compartment heat is too high, and I need all the space in the car that I can get for gear when we go overlanding.

One of the main arguments seem to be that the heat on the hood will degrade solar panel performance while driving, but they say if your hood is hot from the engine running, you don't need the solar panel as the engine can charge your battery. This system is for when it sits around in the sun at camp all day when you are not driving it.

Not the most powerful, complex, eloquent, or technologically advanced system, but is works for me.

Jeff

 

[Vigo]

"Additionally, you could not have it connected connected to the PV ports with the panel/array." are you referring to the inputs from the 12v accessory circuit/step-up converter? (they cannot be wired to the same connections on the MPPT controller as the solar panel inputs?)

Not at the same time.

Maybe im missing something but i dont see the problem with this. They could be connected at the same time, they just wouldn't be utilized at the same time. The 24v converter, although probably not isolated from the 12v system on the negative side, would not allow the solar to 'backfeed' the 12v system as long as the positive poles of the lifepo4 and lead acid systems are not joined anywhere. Since 24v is far below the Vmp of the solar panel, the mppt would not pull the circuit down far enough for the 24v converter to do anything as long as solar power was available. When solar power was not available, the MPPT would take power from the converter. Let me know if im missing something.

 

[sunshine_eggo]

Maybe im missing something but i dont see the problem with this. They could be connected at the same time, they just wouldn't be utilized at the same time. The 24v converter, although probably not isolated from the 12v system on the negative side, would not allow the solar to 'backfeed' the 12v system as long as the positive poles of the lifepo4 and lead acid systems are not joined anywhere. Since 24v is far below the Vmp of the solar panel, the mppt would not pull the circuit down far enough for the 24v converter to do anything as long as solar power was available. When solar power was not available, the MPPT would take power from the converter. Let me know if im missing something.

Can you be certain the DC-DC converter can tolerate PV Voc on its output?

 

[Vigo]

Actually, given that a "48v panel" probably has a 60-70 Voc, that's a good point. I've noticed that among the listings that actually specify operating ranges, the range is usually much more than the actual nominal input/output voltage (ive seen 12v converters say they can handle up to 90v), but without a spec i couldn't say for sure that a 24v converter could handle the Voc of that panel. So, point taken!

 

[theoldwizard1]

Probably the absolute cheapest way to get alternator charging (that will actually charge the LFP to full and not just to alternator voltage) is to get a 12 to 24v step up converter slightly bigger than your MPPT (example), wire it to a source that is only active with the key on or engine running, and feed the 24v output to your MPPT in parallel with the solar panels. Any time the solar panel is exceeding 24v the converter will be ignored, but when the solar is making less than 24v the MPPT will treat the converter as the solar panel and charge from that.

The referenced 12V-24V step up converter will NEVER create sufficient voltage to FULLY charge any type of 24V battery bank. Simple lead-acid batteries need AT LEAST 26.4V (closer to 28V) to charge. LiFePO4 require about 29V. These really need a "smart" charger to fully either type of battery bank.

 

[ShirBlackspots]

The mppt itself will not monitor battery SOC. You would need to install a battery monitor. Given the fairly small amperages we are talking about here, there are options as low as $20 that have the shunt and screen all built together (example), or have the shunt as a separate component.

Probably the absolute cheapest way to get alternator charging (that will actually charge the LFP to full and not just to alternator voltage) is to get a 12 to 24v step up converter slightly bigger than your MPPT (example), wire it to a source that is only active with the key on or engine running, and feed the 24v output to your MPPT in parallel with the solar panels. Any time the solar panel is exceeding 24v the converter will be ignored, but when the solar is making less than 24v the MPPT will treat the converter as the solar panel and charge from that.

The BMS itself monitors SoC and charge levels (Apparently JK BMS's are the best). If you get the JK BMS inverter model, it will communicate with the Victron equipment.