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

[sbsyncro]

I carry a Dometic fridge in the back of my jeep and power it with a 1500wh 'all in one' type LifePo4 battery pack that will generally last me about 5-6 days without sun which is never a problem. I have a 200w 48v solar panel on the roof that is used to recharge the pack. I've gone through several such so-called "solar generators" and none of them seem completely reliable. They all have quirks - either they won't restart charging by themselves in the morning or the DC circuit randomly turns off, or they randomly decide to stop charging, etc. The constant vigilance is tiresome. I don't need the AC input or output.

So I'm considering building my own system and paring it down to the essentials of what I need, without spending money unnecessarily. I'm a bit confused as to what components I will require and could use some guidance. My goal is to have a reliable system that takes up the least amount of space and where I'm not paying for features or functions that I don't need.

My list:

• 100ah LifePO4 battery w/BMS - $250
• Victron SmartSolar MPPT 75/15 - $65

Do I need anything else if I just want to charge from the solar panel? I know the MPPT unit has bluetooth and can monitor charging, but does it allow me to see SOC and other important details or do I need to install a shunt and monitor for that? (if so is the "SmartShunt IP65 500" -$110 the way to go to save space and money, or is there something smaller?)

Lastly, if I decided to wire it up to the vehicles alternator for charging while underway, what is the simplest/least expensive way to get maybe around 100w to the battery?

Thanks in advance for any help and expertise!

 

[Vigo]

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.

 

[MrNatural22]

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 if you already have that MPPT 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 Victron smart Solar mppt CC does indeed monitor the battery SOC and other parameters. The bt phone app has many operational features.

 

[bcolins]

The Victron smart Solar mppt CC does indeed monitor the battery SOC and other parameters. The bt phone app has many operational features.

I am also interested in this build. What battery are you thinking of using?

 

[sbsyncro]

I am also interested in this build. What battery are you thinking of using?

I've got two of the AOLithium 100ah units (with Bluetooth) in my camp trailer (along with a Victron MPPT controller) and they are working really well. I'm thinking of the non-BT version for this build and they are only $200.

 

[Supervstech]

Bluetooth equipped bms units usually have a basic state of charge, but i haven't seen one that will track usage.
Most mppt controllers do have a kWh tracking feature.

 

[Checkthisout]

Your refrigerator load is low enough that you can probably just use the load output on the mppt wire up your inverter.

Consumption will be tracked that way if tracking consumption is of interest.

 

[HarryN]

The challenge that you have is that the central coast is overcast, so your system needs to be optimized for low light conditions.

For a system to be reliable in that location, that absolute minimum battery pack size would be 2 x 100 amp-hr batteries or equivalent.

The absolute minimum solar would be at least 300 watts total but 400 would be better. Poly panels will work better for you than mono but it is not super critical.

A PWM solar charge controller will work better for you than an MPPT one, as it will turn on earlier in the day and in less ideal light conditions than an MPPT. I would suggest a bogart engineering setup - that is what I found works well in the SF Bay coastal areas. They also sell a monitor that goes with it.

The bogart will auto re-start charging for you and work in sunlight conditions that the victron can't touch.

Typically people mount panels facing "up" but in addition if you can attach a panel that faces the late afternoon sun ( so vertical facing west ) it will help more than you think. Even if you split the panels up as 200 facing up and 200 facing west.

Put a terminal fuse on each battery and wire every thing in parallel to a fuse block and you are good to go.

Here is a simple example of the wiring.

Small test fixture

Sometimes it is easier to show people things in photos than to describe them. So I made a little test fixture from left over parts, nothing fancy. In this case, some people asked about methods of dealing with pre-charging the capacitors on the input stage of inverters, and I had suggested that...

diysolarforum.com

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Your budget is fairly minimal - my suggestion is to either focus on solar charging or alternator charging and buy decent versions of one or the other, because if you go cheap, you still won't be happy.

A good quality setup for alternator charging is something from sterling.

 

[Dave in AZ]

I carry a Dometic fridge in the back of my jeep and power it with a 1500wh 'all in one' type LifePo4 battery pack that will generally last me about 5-6 days without sun which is never a problem. I have a 200w 48v solar panel on the roof that is used to recharge the pack. I've gone through several such so-called "solar generators" and none of them seem completely reliable. They all have quirks - either they won't restart charging by themselves in the morning or the DC circuit randomly turns off, or they randomly decide to stop charging, etc. The constant vigilance is tiresome. I don't need the AC input or output.

So I'm considering building my own system and paring it down to the essentials of what I need, without spending money unnecessarily. I'm a bit confused as to what components I will require and could use some guidance. My goal is to have a reliable system that takes up the least amount of space and where I'm not paying for features or functions that I don't need.

My list:

• 100ah LifePO4 battery w/BMS - $250
• Victron SmartSolar MPPT 75/15 - $65

Do I need anything else if I just want to charge from the solar panel? I know the MPPT unit has bluetooth and can monitor charging, but does it allow me to see SOC and other important details or do I need to install a shunt and monitor for that? (if so is the "SmartShunt IP65 500" -$110 the way to go to save space and money, or is there something smaller?)

Lastly, if I decided to wire it up to the vehicles alternator for charging while underway, what is the simplest/least expensive way to get maybe around 100w to the battery?

Thanks in advance for any help and expertise!

1. Too late now, but it sounds like you wasted a lot of $$ buying cr8ppy power stations. In future, watch Hobotech and ReeWrayOutdoors on youtube for power station reviews. They specifically test "Does the station auto wakeup in morning and take solar input?", and also "Does the unit turn off dc automatically if there is nothing running, like a fridge between cycles, and how do you adjust that timer?".
2. There are at least 15 power stations I've watched reviews for that would work for you perfectly, they fail the testing otherwise!
3. You already know 1500 Watt-hrs power station works fine for you for 5 to 6 days. You can use a cigarette port in car for 120W to charge a battery. Cheapest min serup, as you asked, is 1500Wh of battery, car port charger, no inverter, and a solar charge controller to fit that panel's output. Maybe the Victron. If you want to see good state of charge, buy the smartshunt too. Lastly, buy an ac dc charger that works with that battery, and charge it at home every 6 days as needed.

 

[Supervstech]

My ecoflow river max runs 24/7, charges when needed, never sleeps...

Just a point of reference.

And they are in stock nationwide at Northern Tools.
Qualifies for the 50.00 monthly coupon also.

 

[corn18]

My ecoflow river max runs 24/7, charges when needed, never sleeps...

Just a point of reference.

And they are in stock nationwide at Northern Tools.
Qualifies for the 50.00 monthly coupon also.

40 Ah might be a bit meager for 5-6 days run time.

 

[Sparks-n-Splinters]

Will has a video for that HERE
This is the one I patterned my system after except I omitted the inverter and went 12v DC fridge. It is only used for the fridge and charging cell phones and flash lights while camping, and the DC fridge plugs right into the truck while traveling which is fantastic and simple.
I went with the Victron 100/20.

If your interested, I'll grab some pics of my set up and post them. (I keep meaning to make a thread about it "when I have time" LOL)

 

[featherlite]

The Victron smart Solar mppt CC does indeed monitor the battery SOC and other parameters.

My Victron SmartSolar MPPT 100/50 charge controller does not monitor the battery state of charge. However, it will show how many Ah the charger itself is providing to the battery.

 

[Supervstech]

40 Ah might be a bit meager for 5-6 days run time.

I meant, the ecoflow model units don’t shut off the dc, and the solar charging works all the time.

 

[pollenface]

Your refrigerator load is low enough that you can probably just use the load output on the mppt wire up your inverter.

Consumption will be tracked that way if tracking consumption is of interest.

That's what I did with a Victron 75/15 and a 35L dometic/waeco fridge. In my case load was never more than 3A

(running directly from 12v - no inverter)

 

[sunshine_eggo]

The Victron smart Solar mppt CC does indeed monitor the battery SOC and other parameters. The bt phone app has many operational features.

Hate to argue with you bro, but the MPPT does not in any way monitor or track battery SoC. It measures voltage, records daily kWh generated and times spent in bulk, absorption and float, and it does other cool stuff including logging up to 46 days data visible on the Trends tab, but it never has any clue whatsoever about the battery SoC.

 

[JWLV]

Most charge controllers that show the battery SoC is wildly inaccurate because it is just derived from the battery voltage. Many of them have the SoC display because it was originally used with lead acid batteries.

 

[sbsyncro]

Thanks everyone that has posted so far - there has been a lot of great information up to this point! My biggest remaining question is about whether to use a Victron smart shunt vs. something cheaper from another brand, and I guess it boils down to whether I want a visual display or want to rely on Bluetooth to my phone. Does anyone know if I have both the Victron "smart" BT version of the MPPT controller and the "smart shunt" whether they share data and consolidate the information into a single view in the Victron app, or do they just appear as separate components with different information? (if the latter, there is little value in staying within the Victron family I suppose).

My planned build at this point:

• AOLithium 100ah LifePO4 battery - $200
• Victron Smart Solar MPPT 75/15 - $70
• AiLi Battery monitor & shunt - $35
• Panel Mount APP connectors (solar input/fridge output) - $20
• Fuse Box (smallest I can find) - $12

Total project cost - around $350. No AC charging. No AC inverter (neither are needed). 200w of solar input @48v. Max 70w draw when fridge cycles (typically more like 40-50w for 3 minutes every 30 minutes @75º ambient temp and 3/4 full).

If I decide to introduce DC-DC charging in the future I may try the step-up converter method into the MPPT controller, as I already have a 10 amp 12v accessory outlet that I wired up in the back of the jeep, and I could just build a 12v ciggie plug-to-APP adapter cord and add an additional APP plug wired to the step-up converter. This seems like the easiest and lowest-profile method to accomplish this. (120w of input would probably be more than enough for this purpose)

The biggest challenge will be to find or buiild an enclosure that will fit on a custom bracket I built that sits above the rear fender and hangs from the roll bar (I have the rear seats removed). it is more or less the exact width of the battery, but about 4" longer; I will need to get pretty creative.

 

[sunshine_eggo]

A major benefit of the shunt is that it will share the voltage, current and temperature (if probe is installed) data with the MPPT to provide actual open circuit voltage and net current flow to/from the battery rather than what the MPPT measures. It will maximize charge speed and accuracy. There's also something to be said about seeing the two devices in the same app.

The MPPT is only a step down device, and it must see +5V above battery voltage to start and maintain +1-2V above battery voltage to maintain charging. Furthermore, your supply must be able to meet the maximum output power of the MPPT, or it will overload. Additionally, you could not have it connected connected to the PV ports with the panel/array.

 

[sbsyncro]

1. Too late now, but it sounds like you wasted a lot of $$ buying cr8ppy power stations. In future, watch Hobotech and ReeWrayOutdoors on youtube for power station reviews. They specifically test "Does the station auto wakeup in morning and take solar input?", and also "Does the unit turn off dc automatically if there is nothing running, like a fridge between cycles, and how do you adjust that timer?".
2. There are at least 15 power stations I've watched reviews for that would work for you perfectly, they fail the testing otherwise!
3. You already know 1500 Watt-hrs power station works fine for you for 5 to 6 days. You can use a cigarette port in car for 120W to charge a battery. Cheapest min serup, as you asked, is 1500Wh of battery, car port charger, no inverter, and a solar charge controller to fit that panel's output. Maybe the Victron. If you want to see good state of charge, buy the smartshunt too. Lastly, buy an ac dc charger that works with that battery, and charge it at home every 6 days as needed.

the one I'm using today was actually reviewed by ReeWrayOutdoors and he gave it a very good review. I have two of them that I bought on a "flash sale" deal last July for about $700 each. Neither will charge reliably and after about 9 months of use, one of them started intermittently shutting off the DC circuit. The solar charging will work fine for a week or two, auto starting each morning, etc. Then suddenly for no apparent reason they just stop charging for a few days. I have not been able to identify any consistent situation that causes the charging to stop. I have tried multiple solar panel arrays (including one provided by the manufacturer!) and when it stops charging via solar, I have to "bump' the charging circuit by hooking it up to AC for a few minutes then switch to solar and it will normally begin charging again via solar. Really weird behavior!