Adding an AC charger to 12V System

dudedogvan

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If I have a 12V system with DIY 280ah LiFePO4 battery, 400w solar panels, 40A-60A MPPT, and a DC-DC charger and I want to add either an AC charger (standalone) or AC charger/inverter combo does the MPPT cut off charge from the solar panels because it senses incoming voltage from AC input when I connect it?
Does it involve an automatic transfer switch? If the AC charger and inverter are separate do I need to install a transfer switch?

I plan to add a manual switch to turn on/off dc-dc charger (most likely 20A) when I'm driving, is this necessary? If the panels are charging while I'm driving and dc-dc is switched on, how does the dc-dc charger know how much to supplement charging the batteries, or does the dc-dc charger supply a constant 20 amps and the MPPT continues to supply max amperage from the panels as well?

How does the BMS work alongside the different charging components? When temps are too low/high (0 celsius to 67 celsius I think) there is a cutoff. Other than that what is it doing in relation to other charging components? Does it just regulate health of individual cells with balance leads?

I'm a newb, basically I'm trying to understand how the 3 different charging sources and BMS will safely work together to charge a 280ah DIY battery properly. For example, if I'm parked idling the engine with the dc-dc charger on, mppt supplying solar in sunny location, and an extension cord plugged into the AC charger from a 110 house outlet, how will the charging components safely charge the 280ah LFP battery together? Please help me understand how it all works together. With that understanding, I can choose the components for my 12v campervan electrical system and draw up a wiring diagram which I can post for critiquing by those of you MUCH more experienced than I, ensuring a safe design and optimal battery health and longevity.
 

time2roll

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First off multiple charging sources are generally not an issue. Each will have a maximum charging voltage and will stop when that voltage is reached. Having multiple sources will not push the voltage higher than any of the chargers is programmed.

Is this an RV? Van conversion? If you add an inverter and want to connect to the existing 120v system a transfer switch is needed and will select power from the main cord or the inverter. Generally inverter-chargers will have a built in transfer switch. If no inverter is being installed then no transfer switch is needed.

No need to turn off solar or the charger while driving and charging through the DC-DC charger. These all can operate together or separate depending on which have a power source to charge. BMS is the last stand of safety to protect the battery. The various chargers should never trip the BMS even when used together.
 

camelCase

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A transfer switch is only required if you have 120v outlets/devices that can get power from more than one source. In my camper I have some 120v outlets that are only hot if shore power is plugged in. I also have an inverter which is not wired to any of those outlets, so I do not need a transfer switch.
 

dudedogvan

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A transfer switch is only required if you have 120v outlets/devices that can get power from more than one source. In my camper I have some 120v outlets that are only hot if shore power is plugged in. I also have an inverter which is not wired to any of those outlets, so I do not need a transfer switch.
Thanks, that clarification provided a new perspective on how I may design the system.
 
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An inverter/charger combines 3 functions, 1: inverter 2: ac2dc charger 3: automatic transfer switch.
If you need any 2 of the 3 I suggest you get an inverter/charger.
The inverter/charger is destroying the market for the discrete alternatives for a reason.
Because of the economy of integration these units are better at each function than their discrete counterparts.

I have written quite a bit on this subject here on the forum.
If you are really curious I will write a bit more about it here.
 

dudedogvan

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An inverter/charger combines 3 functions, 1: inverter 2: ac2dc charger 3: automatic transfer switch.
If you need any 2 of the 3 I suggest you get an inverter/charger.
The inverter/charger is destroying the market for the discrete alternatives for a reason.
Because of the economy of integration these units are better at each function than their discrete counterparts.

I have written quite a bit on this subject here on the forum.
If you are really curious I will write a bit more about it here.
Ok I haven't made up my mind on whether I'm gonna just do a 110v shore plug (not RV style, just regular house 110v) or get an inverter/charger so I can charge house batteries with AC if I need to. The inverter/chargers are cool, but a rather expensive component to add in.

Are there any inverter/chargers under 1000w? I seem to only be able to find 1000w+ units... I'm not opposed to 1000w, but I don't necessarily need one that capable based on my power needs. I have looked at the AIMS 1250w inverter/charger, and in my other thread you linked the Samlex EVO 1200w ($160 more than AIMS). Is the KISAE Abso 1000 inverter/charger worth it for $330 or too low quality, not recommended?
Any other suggestions on ~1000w inverter/chargers? Anything much above 1000w really isn't necessary.
 

dudedogvan

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My gut says its crap.

Gotcha.

Joey, I found this comment you you made in this thread https://diysolarforum.com/threads/what-are-the-tiers-of-brands-for-inverter-chargers-mppt.29232/

So thinking of brands like: TrippLite, Growatt, PowMR, MPP, Victron, AIMS, Sigineer, Midnite, Schnider, Outback, Xantrex, Spartan, etc....
Comparing inverter/chargers and all_in_ones from each company based on my best guess for quality regardless of price.
Based on the excellent judgment of my diaphanous friend and his Sherpa.

Its a stack-rank with tiers.

Victron
Midnite
Schnider

Outback
AIMS
Sigineer
Spartan
Xantrex

Growatt
MPP

TrippLite
PowMR

Is this ranking of brands still accurate? Anyone have any recommendations on an MPPT, DC-DC charger, and inverter/charger that's solid quality and reliability for the best price? I was gonna go with a rich solar 40A MPPT and 20A Renogy DC-DC charger (based on Will Prowse's videos), but after reading through some threads, other knowledgeable members do not recommend these brands. I'm not trying to break the bank, but I do want peace of mind. I'm really trying to nail down what components I'm gonna use so I can tally it up, draw up the wiring diagram, and move on with the rest of the van build!
 

sunshine

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I want to add either an AC charger (standalone)
I use a 1500watt (0-15v) variable PSU set at 12.6v


connected through diodes and is left on.

You get a lot more power/$ from the variable PSU and set the V to just above the low battery cutoff.
The solar CC supplies the daytime power and battery charging.
I also have a 300w battery charger connected, also through diodes, but turned off. The higher voltages over rides the solar input.
 
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rmaddy

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Anything much above 1000w really isn't necessary.
It's a pleasure seeing someone be reasonable about their power usage in a van.

But I'd like to point out that depending on what you wish to run on AC with your inverter, you might need a higher wattage inverter due to startup power of some devices. For example, an 800W microwave might need a 2000W inverter due to the startup surge. Anything with a motor will also have a big startup surge even if the running wattage is much lower. I'd suggest carefully reviewing the list of items you will use with your inverter and verify whether it actually needs a bigger inverter to handle its startup.
 
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Is this ranking of brands still accurate?
In hind site that list of brands was ill conceived.
Different brands target different applications and different price points.
For example Schneider makes great inverter/chargers but they don't make anything for mobile applications.
I suggest you determine your requirements and then we can suggest components that meet those requirements.
Anyone have any recommendations on an MPPT, DC-DC charger, and inverter/charger that's solid quality and reliability for the best price?
For a solar charge controller for mobile, Victron is my goto.
For DC-DC charger it depends on what alternator you have and how much of its capacity is available.
I was gonna go with a rich solar 40A MPPT and 20A Renogy DC-DC charger (based on Will Prowse's videos), but after reading through some threads, other knowledgeable members do not recommend these brands. I'm not trying to break the bank, but I do want peace of mind. I'm really trying to nail down what components I'm gonna use so I can tally it up, draw up the wiring diagram, and move on with the rest of the van build!
Before you make the diagram determine your needs(yes I am repeating myself).
Suggest you make the diagram with generic components after determining your needs.
 

time2roll

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For example, an 800W microwave might need a 2000W inverter due to the startup surge.
MW is probably the largest load in van living and might be used frequently due to limited space. I recommend a Panasonic inverter series microwave. This unit actually draws lower power when a lower power is selected. Very different from the typical MW that always runs at full power but cycles the magnetron when using lower power levels. The Panasonic goes down to about 500 watts before the magnetron cycles.

If plugged into utility power or enough generator it can be run at full power.
 

dudedogvan

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MW is probably the largest load in van living and might be used frequently due to limited space. I recommend a Panasonic inverter series microwave. This unit actually draws lower power when a lower power is selected. Very different from the typical MW that always runs at full power but cycles the magnetron when using lower power levels. The Panasonic goes down to about 500 watts before the magnetron cycles.

If plugged into utility power or enough generator it can be run at full power.

TBH I don't plan on having a microwave in there ever. Propane stove is good enough for me, but I appreciate your point. Startup power is probably commonly over looked.
 

sunshine

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Startup power is probably commonly over looked
With generic hf inverters there isn't usually much difference in price and the capacity and the standby loads are often quoted to be the same.
One thing to lookout for is making they are up to standard with the proper safety label for your locale.
 

dudedogvan

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In hind site that list of brands was ill conceived.
Different brands target different applications and different price points.
For example Schneider makes great inverter/chargers but they don't make anything for mobile applications.
I suggest you determine your requirements and then we can suggest components that meet those requirements.

For a solar charge controller for mobile, Victron is my goto.
For DC-DC charger it depends on what alternator you have and how much of its capacity is available.

Before you make the diagram determine your needs(yes I am repeating myself).
Suggest you make the diagram with generic components after determining your needs.

Something I'm wondering: I want to build a DIY 280ah LFP (cheapest/wh). It was gonna be a 206ah SOK but I found I could get that extra 74ah for $300 less. I still want to stick with 2x 200w rich solar panels (I don't want another panel to take up roof rack space and was already settled on the 400w of panels). I know 600w would be optimal, but will the 400w of panels suffice? My logic is, even if I can't charge the full 280ah with 400w it will still suffice for ~200ah worth of battery, still meeting my power needs (my power audit yields an estimated peak power demand of ~145ah/day). Roughly, this equates to 400w panels charging the batteries to a ~70% SOC (following the simple rule: panel wattage=2X battery ah). With my logic the EVE cells will remain healthy because they have no issue with being partially discharged consistently, correct? Or am I way out there? If my power needs ever increase, I will already have invested in the extra 74ah capacity and saved money. Logically, it seems like best use of my resources.

I also plan to have a DC-DC charger to supplement when driving. The van's alternator is 115A and the starter battery is a FLA 650CCA.
Is a 20A DC-DC charger what I need? 30A? 40A? suggestions please.

Looking at Victron SmartSolar mppt, the 200w Rich Solar panel specs are:
  • Maximum Power(Pmax): 200W
  • Maximum Power Voltage(Vmp): 20.4V
  • Maximum Power Current(Imp): 9.80A
  • Open Circuit Voltage(Voc): 24.3V
  • Short Circuit Current(Isc): 10.2A
  • Maximum System Voltage(Vmax): 1000VDC
If I wire the panels in series, the amperage should still be 9.8A correct? Will the 100/15 suffice? 100/20? 100/30? Or should I just get the 100/50 in case I want to add a panel or 2? (down the road it's possible I remove the system to reinstall on another van, bus, or for a homestead, which may require a larger system, therefore a larger controller). Thoughts and suggestions?

I know I have a lot of questions because I'm a newb, so I very much appreciate everyone taking the time to help me learn. I'm very interested and I've already learned so much from the forum and Will's videos. It's been very enjoyable and I'm so grateful.
 
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dudedogvan

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Something I'm wondering: I want to build a DIY 280ah LFP (cheapest/wh). It was gonna be a 206ah SOK but I found I could get that extra 74ah for $300 less. I still want to stick with 2x 200w rich solar panels (I don't want another panel to take up roof rack space and was already settled on the 400w of panels). I know 600w would be optimal, but will the 400w of panels suffice? My logic is, even if I can't charge the full 280ah with 400w it will still suffice for ~200ah worth of battery, still meeting my power needs (my power audit yields an estimated peak power demand of ~145ah/day). Roughly, this equates to 400w panels charging the batteries to a ~70% SOC (following the simple rule: panel wattage=2X battery ah). With my logic the EVE cells will remain healthy because they have no issue with being partially discharged consistently, correct? Or am I way out there? If my power needs ever increase, I will already have invested in the extra 74ah capacity and saved money. Logically, it seems like best use of my resources.

I also plan to have a DC-DC charger to supplement when driving. The van's alternator is 115A and the starter battery is a FLA 650CCA.
Is a 20A DC-DC charger what I need? 30A? 40A? suggestions please.

Looking at Victron SmartSolar mppt, the 200w Rich Solar panel specs are:
  • Maximum Power(Pmax): 200W
  • Maximum Power Voltage(Vmp): 20.4V
  • Maximum Power Current(Imp): 9.80A
  • Open Circuit Voltage(Voc): 24.3V
  • Short Circuit Current(Isc): 10.2A
  • Maximum System Voltage(Vmax): 1000VDC
If I wire the panels in series, the amperage should still be 9.8A correct? Will the 75/15 or 100/15 suffice? 100/20? 100/30? Or should I just get the 100/50 in case I want to add a panel or 2? (down the road it's probable I remove the system to reinstall on another van, bus, or for a homestead, which may require a larger system, therefore a larger controller, which I will already have if I size up). Thoughts and suggestions?

I know I have a lot of questions because I'm a newb, so I very much appreciate everyone taking the time to help me learn. I'm very interested and I've already learned so much from the forum and Will's videos. It's been very enjoyable and I'm so grateful.
 

camelCase

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LiFePo4 chemistries actually prefer being at lower states of charge, so you don't need to keep them fully charged all the time. The question is if you can live with the power that 400W of panels plus whatever the alternator can provide with the amount of driving you do.

The second number in the Victron naming scheme is the rated charging current to the battery, not the amps in from the panels. The 100/30 supports ~440watts of panels (though you'll never likely see the full amount for flat mounted panels) and would maximize the amount of power from your panels.

For the DC-DC charger sizing, the general guidance that gets tossed around is to keep the continuous load on the alternator at 50% or less of it's rated maximum. Draw too much too long and it tends to get hot and let out the smoke sooner than one would prefer. With a 115A alternator, I'd err on the side of less. The 40A and larger Renogy DC-DC converters have the option of switching to half power mode so that is something to consider.
 

dudedogvan

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LiFePo4 chemistries actually prefer being at lower states of charge, so you don't need to keep them fully charged all the time. The question is if you can live with the power that 400W of panels plus whatever the alternator can provide with the amount of driving you do.

The second number in the Victron naming scheme is the rated charging current to the battery, not the amps in from the panels. The 100/30 supports ~440watts of panels (though you'll never likely see the full amount for flat mounted panels) and would maximize the amount of power from your panels.

For the DC-DC charger sizing, the general guidance that gets tossed around is to keep the continuous load on the alternator at 50% or less of it's rated maximum. Draw too much too long and it tends to get hot and let out the smoke sooner than one would prefer. With a 115A alternator, I'd err on the side of less. The 40A and larger Renogy DC-DC converters have the option of switching to half power mode so that is something to consider.
I can live with 400w and a DC-DC charger.

Ok, but if the Max Power Current of the panels is 9.8A and the panels are in series, doesn't that negate the capability of the mppt to charge at 30A since the panels can only push the 9.8A Max? Please explain. Thank you.
 

time2roll

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I can live with 400w and a DC-DC charger.

Ok, but if the Max Power Current of the panels is 9.8A and the panels are in series, doesn't that negate the capability of the mppt to charge at 30A since the panels can only push the 9.8A Max? Please explain. Thank you.
The MPPT pushes the full wattage. After correcting the voltage the rest becomes amps. 400w / 14 volts = 28.5 amps. That controller is close to maxed out.
 
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