Astrovan solar diagram - does this look right?

[PrimalScream]

Hey folks

I am working on an Astro van camper build and have been doing some research on solar setups.

I want something that is fairly simple and lightweight as I don't intend to use very much power and or be off-grid for more than a couple days at a time.
I also want to be able to charge the auxiliary battery with the van's alternator. I only want to run one 100W panel and it seems like charging with the alternator could help keep the battery topped up during rare/unexpected periods of extended use when the panel isn't getting enough sun.
The Renogy DCC30S seems like a good, simple way to get an MPPT to maximize the potential of the single 100W panel and also incorporate the alternator into the charging circuit. It would also be nice to have the Renogy use the panel to help keep the starting battery topped up with the vehicle off, but maybe one panel doesn't really have enough amperage for this?

I made a diagram of a possible system, I'm wondering if anyone can give me some feedback on its viability

some of the main things I'm confused about are where to put the megafuse that protects the inverter circuit and if the 40a breakers protecting the DCC30S are necessary. I included the circuit breaker between the van battery and the DCC30s because someone else had an 80a one in their RV circuit, but I would think that it could trip the breaker every time you start the car...
Also: Do I need a fuse between the renogy and the panel?

astro solar diagram

Best
Mitch

 

[Rocketman]

Here are my thoughts…

Instead of having at least three lugs directly on the positive lug of the 200ah battery, add a small bus bar.

Also, add a small (15a or so) circuit breaker between the solar panel and the SCC (DCC30S). This is just so you can “turn the sun off” for maintenance and testing.

With Lead batteries (including AGM) it is important to very regularly get them completely topped off. I would consider adding at least another solar panel. And if possible designing so you can add up to four (in the future if you need it).

Battery Monitor. Look for a shunt based battery monitor like Victron Smartshunt or BMV712 (there are other brands too). This way you know if your battery is mostly full or mostly empty. You will also know if you are taking your battery down to low into the damage zone.

When boondocking I look at my Smartshunt just before bed every night to make sure I have not left a load on somewhere and the “time remaining” is longer than the night will last (so the solar will kick in).

You may also want to redo your drawing and list the size of wires- I have seen mistakes made where wires were the wrong size.

Good Luck - looks like a fun project!

 

[PrimalScream]

Here are my thoughts…

Instead of having at least three lugs directly on the positive lug of the 200ah battery, add a small bus bar.

Also, add a small (15a or so) circuit breaker between the solar panel and the SCC (DCC30S). This is just so you can “turn the sun off” for maintenance and testing.

With Lead batteries (including AGM) it is important to very regularly get them completely topped off. I would consider adding at least another solar panel. And if possible designing so you can add up to four (in the future if you need it).

Battery Monitor. Look for a shunt based battery monitor like Victron Smartshunt or BMV712 (there are other brands too). This way you know if your battery is mostly full or mostly empty. You will also know if you are taking your battery down to low into the damage zone.

When boondocking I look at my Smartshunt just before bed every night to make sure I have not left a load on somewhere and the “time remaining” is longer than the night will last (so the solar will kick in).

You may also want to redo your drawing and list the size of wires- I have seen mistakes made where wires were the wrong size.

Good Luck - looks like a fun project!

This is exactly what I needed to hear, thank you much.

I was planning to monitor the battery with renogy BT2 and my iphone but forgot to include it in the diagram.
Intending to leave a space for a second panel on the roof and see how it goes with just one. I have to save space for a cargo basket that will mount the spare and aux fuel.
My thinking was I only need one panel for the fridge, which is the only continuous draw, so with the frequency of driving that I will be doing the alternator may make up the difference (especially if I charge devices using the car circuit while driving). But you're right, I might have to add a second panel.

As far as wire sizes, I havent figured that out yet haha. I know its going to be alot of 10AWG. I need to do some research and figure out the wire gauge connecting the starting battery to the SCC.

Mitch

 

[John Frum]

1500 ac watts / .85 conversion factor / 10 volts low cutoff = 176.470588235 service amps
176.470588235 service amps / .8 fuse headroom = 220.588235294 fault current

The means pure copper wire with 105C insulation and a 250 amp fuse for the main circuit.

Since your are using an agm battery you will want a shunt to keep track of state of charge

Here is take on your setup.

 

[PrimalScream]

1500 ac watts / .85 conversion factor / 10 volts low cutoff = 176.470588235 service amps
176.470588235 service amps / .8 fuse headroom = 220.588235294 fault current

The means pure copper wire with 105C insulation and a 250 amp fuse for the main circuit.

Since your are using an agm battery you will want a shunt to keep track of state of charge

Here is take on your setup.

Im sorry I dont know how to view that .txt file. when i downloaded it and pulled it up in textedit I got lines of code, is there a program you guys are using to create wiring schematics?

I know that the shunt is better because it measures the actual discharge of the battery as opposed to the MPPT which just measures the voltage, I'm just wondering why the voltage reading from the MPPT isnt a good way to monitor the state of the battery.

thanks for your help

Mitch

 

[John Frum]

Im sorry I dont know how to view that .txt file. when i downloaded it and pulled it up in textedit I got lines of code, is there a program you guys are using to create wiring schematics?

Its human readable.
Have a look at the legend block it explains the dc_domain block.
Hint: typically the systems we make are a ladder where the busbars are the risers and the circuits are the rungs.

I know that the shunt is better because it measures the actual discharge of the battery as opposed to the MPPT which just measures the voltage, I'm just wondering why the voltage reading from the MPPT isnt a good way to monitor the state of the battery.

Voltage alone is not a good way to judge the battery SOC, because during load or charge the voltage will register low or high respectively.
That AGM battery is going to sag like a bad mattress when you run your electric kettle.
For longevity AGM batteries should not be discharged below 50%.

 

[PrimalScream]

Its human readable.
Have a look at the legend block it explains the dc_domain block.
Hint: typically the systems we make are a ladder where the busbars are the risers and the circuits are the rungs.

Voltage alone is not a good way to judge the battery SOC, because during load or charge the voltage will register low or high respectively.
That AGM battery is going to sag like a bad mattress when you run your electric kettle.
For longevity AGM batteries should not be discharged below 50%.

Ok thanks for that. Ill give that text file another shot.
Its funny i forgot to check my kettle, I just did and its 1500W. I'll have to pick up a half liter kettle that consumes closer to 700w.

That makes sense re: voltage drop, it looks like renogy also makes a 500A shunt with a digital readout.

 

[John Frum]

Here is another version that uses the vehicle chassis as the negative busbar.

 

[John Frum]

Suggest you use both a fused positive and un-fused negative busbar.
Also suggest you do the "big three" upgrade.
Battery.positive to alternator, engine block to chassis and chassis to battery.negative.

 

[PrimalScream]

Suggest you use both a fused positive and un-fused negative busbar.
Also suggest you do the "big three" upgrade.
Battery.positive to alternator, engine block to chassis and chassis to battery.negative.

sorry for the confusion but what are you referring to as dc.distribution.feeder in the schematic you sent?
seems like this is an additional component.
Also, you are referencing fused buss bars, do you have a link to these that support the kind of amperage we are talking about. I am used to the little buss bars you pick up for like $10 that don't have fuses.

Mitch

 

[John Frum]

sorry for the confusion but what are you referring to as dc.distribution.feeder in the schematic you sent?
seems like this is an additional component.

Its the fuse panel in your diagram

Also, you are referencing fused buss bars, do you have a link to these that support the kind of amperage we are talking about. I am used to the little buss bars you pick up for like $10 that don't have fuses.

Mitch

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder, 7 Stud Assembly with Bolts and Bus Bars, 400A is in stock and ready to ship. Order today!

www.waytekwire.com

I would use this for both positive and negative busbars.
The fuses are so cheap that for the negative side I just put the fuses underneath the busbar.

ZCASE-Series: Blade Fuses | Waytek

Bolt-down fuses provide protection from 30A to 600A and are ideal for battery and alternator circuit protection. Order from Waytek today!

www.waytekwire.com

Use m8 fuses as the studs on the busbar I linked are m8.

 

[PrimalScream]

Its the fuse panel in your diagram

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder, 7 Stud Assembly with Bolts and Bus Bars, 400A is in stock and ready to ship. Order today!

www.waytekwire.com

I would use this for both positive and negative busbars.
The fuses are so cheap that for the negative side I just put the fuses underneath the busbar.

ZCASE-Series: Blade Fuses | Waytek

Bolt-down fuses provide protection from 30A to 600A and are ideal for battery and alternator circuit protection. Order from Waytek today!

www.waytekwire.com

Use m8 fuses as the studs on the busbar I linked are m8.

This is great, thanks for all the info. I really appreciate it.

Should I stay away from CCA wire? I saw you mentioned pure copper wire above

 

[John Frum]

This is great, thanks for all the info. I really appreciate it.

Should I stay away from CCA wire?

Yes!

 

[PrimalScream]

Yes!

One last question, John. How do you calculate the bus bar rating that is required? is a 250A bar too small for this application?

 

[John Frum]

One last question, John. How do you calculate the bus bar rating that is required? is a 250A bar too small for this application?

250A would be the bare minimum.
Most of the busbars on Amazon and similar are crap btw.

 

[PrimalScream]

250A would be the bare minimum.
Most of the busbars on Amazon and similar are crap btw.

Thanks so much again for your input John, really brought me up to speed on this stuff.

I placed my first couple big orders. I went with a 100Ah lithium battery and a 100W panel and Im going to be fabricating mounts for both that allow me to drop in a second one of each in the future.
as far as the busbars I went with the littelfuse you suggested for power and a victron bar for the ground.

its been a bigger investment than I predicted with my limited knowledge but I feel like Im doing it right now.. and I probably wont burn my van to the ground

Mitch

 

[John Frum]

A 100ah LFP battery should not be discharged at higher than 50 amps continous(0.5c).
Short surges to 100 amps are ok but your 1500 watt inverter is very likely to trip the battery BMS an over-current.
That is pretty hard on the BMS.

 

[PrimalScream]

A 100ah LFP battery should not be discharged at higher than 50 amps continous(0.5c).
Short surges to 100 amps are ok but your 1500 watt inverter is very likely to trip the battery BMS an over-current.
That is pretty hard on the BMS.

I see. this is just from turning the inverter on or when the inverter is actually sending 1500 watts of power to something?
I don't currently plan to use the inverter for anything over 700W but I bought a bigger one just in case.
The fridge is the only constant current in my setup and I was thinking of running it off 12V power

Also, will running 2 100Ah batts in parallel help with this or do you need a larger singular battery?

Mitch

 

[John Frum]

I see. this is just from turning the inverter on or when the inverter is actually sending 1500 watts of power to something?

1500 ac watts / .85 conversion factor / 10 volts low cutoff = 176.470588235 amps.
That means at full bore your BMS will trip on over current.
I would guess the first level of BMS over current protection would trigger at ~125 amps for 30 seconds.
The second level of BMS over current protection is probably something like ~200 amps for 50 microseconds.
You might hit that by just turning on the inverter which will prime all the capacitors in the inverter.
Often they prime on connect whether power switch is on or off.

I don't currently plan to use the inverter for anything over 700W but I bought a bigger one just in case.

700 ac watts / .85 conversion factor / 10 volts low cutoff = 82.352941176 amps

Also, will running 2 100Ah batts in parallel help with this or do you need a larger singular battery?

2x 100ah batteries in parallel will be able to provide approximately twice the current.

 

[PrimalScream]

1500 ac watts / .85 conversion factor / 10 volts low cutoff = 176.470588235 amps.
That means at full bore your BMS will trip on over current.
I would guess the first level of BMS over current protection would trigger at ~125 amps for 30 seconds.
The second level of BMS over current protection is probably something like ~200 amps for 50 microseconds.
You might hit that by just turning on the inverter which will prime all the capacitors in the inverter.
Often they prime on connect whether power switch is on or off.

700 ac watts / .85 conversion factor / 10 volts low cutoff = 82.352941176 amps

2x 100ah batteries in parallel will be able to provide approximately twice the current.

I see. It isn't an expensive inverter anyway, maybe I will shelve it and buy a smaller one if its too hard on the battery.

Mitch