TRUTH or fiction

[BBQ]

Originally Posted by fratermus

/squinting

I don't think that is a supportable position.

Experiments:

1. attach loads direct to panels; see if loads run off solar
2. Assume battery at 100% SoC. Run CC output, battery, and loads to the same bus. Does power come from the CC, hit the bus, run down to the battery pos terminal, back up the same wire back to the bus and out to the load? If so, why?

You have a DIY. What appliances in your RV run directly off solar?

[fratermus]

Originally Posted by GeorgeRa

I have some difficulties understanding why this statement has being questioned.

Here is the statement being questioned:

"Nothing really runs off the solar... You use the solar to charge the batteries, which in turn provides power to the appliances."

In my reading that posits some kind of PV->battery->load linear path the power must follow, and I think that's misleading to onlookers who are envisioning their own systems.

Originally Posted by GeorgeRa

I have never seen RV or marine installation with solar panels directly connected to loads

Agreed; it would be impractical.

Originally Posted by GeorgeRa

Batteries are used as energy buffer to provide stable energy source.

Agreed. And if BBQ had claimed that I wouldn't have objected.

Originally Posted by GeorgeRa

Perhaps someone can
provide a concise point what is the issue with the above statement.

I tried to do that in my original reply.

I hope this will illustrate my objection:

given this configuration

• Nominal 12v PV with sufficient output
• Nominal 12v lead-acid bank
• cc with sufficient output
• initial inrush / MPPT hunting effects ignored for simplicity

no load
PV: producing .2A
Bank: consuming .2A
Load: consuming 0A

load added
PV: producing 10.2A
Bank: consuming .2A
Load: consuming 10A


So the question to be answered is this: In the "load added" scenario is the load running off solar?

I suggest it is "running off solar"; PV are powering the load. The CC is holding the Vfloat setpoint and the battery is acting as an energy buffer.

[BBQ]

.

LOL

OP who asked a simple newbie question on solar and AC.
I gave a simple easy to understand answer
and you went all out off on a tangent to prove your superior knowledge in P & V.


You are brilliant.

*smh*

???

[Davydd]

Originally Posted by wincrasher

The max I've seen installed on a Sprinter van from Roadtrek is 600 watts. Before Davydd chimes in, yes ARV's Solar Womp had much more, but that's an abberation IMNSHO.

So you tell me, how much AC can run off solar. Answer: NONE. It runs off the inverter fed off the batteries.

Ya'll can head out to recess now...

Since you assumed I would chime in the Solar Womp is probably the maximum solar you can get with any Class B van and still only gets you about 1200w with an extraordinary super structure. On the roof van itself Roadtrek managed about 900w with Mike Wendland's beta van. Still no cigar in running an air conditioner.

I took the original question of whether solar makes a blippin' difference in running an air conditioner and the answer is no but the brouhaha over this got sidetracked.

[GeorgeRa]

Originally Posted by Davydd

..................the answer is no but the brouhaha over this got sidetracked.

Great description.

[GeorgeRa]

Originally Posted by fratermus

Here is the statement being questioned:

In my reading that posits some kind of PV->battery->load linear path the power must follow, and I think that's misleading to onlookers who are envisioning their own systems.

Agreed; it would be impractical.

Agreed. And if BBQ had claimed that I wouldn't have objected.

I tried to do that in my original reply.

I hope this will illustrate my objection:

given this configuration

• Nominal 12v PV with sufficient output
• Nominal 12v lead-acid bank
• cc with sufficient output
• initial inrush / MPPT hunting effects ignored for simplicity

no load
PV: producing .2A
Bank: consuming .2A
Load: consuming 0A

load added
PV: producing 10.2A
Bank: consuming .2A
Load: consuming 10A


So the question to be answered is this: In the "load added" scenario is the load running off solar?

I suggest it is "running off solar"; PV are powering the load. The CC is holding the Vfloat setpoint and the battery is acting as an energy buffer.

Thank you, still trying to see an actual value of what I would call in my simplistic language analysis paralysis or splitting hairs. Nice entry to this forum, 4 out of 9 your first posts related to this.... I hope to see at some point pictures of your DIY van.

[gerrym51]

Solar Womp is a great name though

[DCHitt]

I've enjoyed the debate. So to get air conditioning we:

Charge the batteries with solar.
Convert the battery power to AC power.
Run the air conditioning for a little while using battery and solar power.
Start the engine to charge the batteries and run the Air Conditioning.
It can't keep up so we then get hot.

Why not use an air conditioning compressor that is driven directly from the engine rather than engine-alternator-battery-inverter-compressor. Oh.... the compressor is already there and is used with the dash AC. So all we need is an evaporator in the back of the van. Oh... it turns out to be an option in most van's.

Either way you end up idling the engine to get air conditioning, only the directly driven compressor works, is less expensive, has less losses. Some side effects is that you don't need big batteries and that the batteries you have get charged as you run the Air conditioning, and your water can get heated also.

Don't get stuck with the big battery/generator approach.

[booster]

Originally Posted by DCHitt

I've enjoyed the debate. So to get air conditioning we:

Charge the batteries with solar.
Convert the battery power to AC power.
Run the air conditioning for a little while using battery and solar power.
Start the engine to charge the batteries and run the Air Conditioning.
It can't keep up so we then get hot.

Why not use an air conditioning compressor that is driven directly from the engine rather than engine-alternator-battery-inverter-compressor. Oh.... the compressor is already there and is used with the dash AC. So all we need is an evaporator in the back of the van. Oh... it turns out to be an option in most van's.

Either way you end up idling the engine to get air conditioning, only the directly driven compressor works, is less expensive, has less losses. Some side effects is that you don't need big batteries and that the batteries you have get charged as you run the Air conditioning, and your water can get heated also.

Don't get stuck with the big battery/generator approach.

X2 plus 10 characters to meeeeet the rules

[Davydd]

Originally Posted by DCHitt

I've enjoyed the debate. So to get air conditioning we:

Charge the batteries with solar.
Convert the battery power to AC power.
Run the air conditioning for a little while using battery and solar power.
Start the engine to charge the batteries and run the Air Conditioning.
It can't keep up so we then get hot.

Why not use an air conditioning compressor that is driven directly from the engine rather than engine-alternator-battery-inverter-compressor. Oh.... the compressor is already there and is used with the dash AC. So all we need is an evaporator in the back of the van. Oh... it turns out to be an option in most van's.

Either way you end up idling the engine to get air conditioning, only the directly driven compressor works, is less expensive, has less losses. Some side effects is that you don't need big batteries and that the batteries you have get charged as you run the Air conditioning, and your water can get heated also.

Don't get stuck with the big battery/generator approach.

Or you simply plug into shore power if you truly need air conditioning.

[fratermus]

Originally Posted by GeorgeRa

I hope to see at some point pictures of your DIY van.

I made a dinky intro post just now with a bit of info.

Originally Posted by Davydd

Or you simply plug into shore power if you truly need air conditioning.

That's certainly the cheapest way, and is how I plan to do it.

[BBQ]

Originally Posted by fratermus

I already said I wasn't trying to pick a fight.

My understanding, and I am willing to be corrected:

• given the slow drift of electrons along the conductor no single electron will enter and exit the wire for a long while.
• since electrons do not move in a straight path there is no way to predict which one will come out the end first
• the overall direction of flow of electrons is, by +/- notation, backwards by longstanding convention

I do not think you are acting in good faith, so it wouldn't be productive to continue interacting with you on this forum.

The correct answer is 4.

[obgraham]

The bottom line to this thread, in answering OP, is that the RT system of batteries/solar/engine-genny is designed to allow short term use of the air conditioning. For that, and for all my needs, it works just fine.

If you need more, your choices are:
1.Like Davydd says, plug in
2.Run the engine (not a long term answer)
3.Go where it's not so hot
4.Get hot, with or without fans.

Works for me!

[Davydd]

Originally Posted by obgraham

The bottom line to this thread, in answering OP, is that the RT system of batteries/solar/engine-genny is designed to allow short term use of the air conditioning. For that, and for all my needs, it works just fine.

If you need more, your choices are:
1.Like Davydd says, plug in
2.Run the engine (not a long term answer)
3.Go where it's not so hot
4.Get hot, with or without fans.

Works for me!

The big fallacy in running an air conditioner all night, even if it could be done, is you eventually need a charging source and an Onan or idling in a campground will not be OK and usually against the rules. Then if you are boondocking in seeking solace and nature away from everyone, why despoil it? That leaves a Walmart parking lot and then it makes no difference amongst the all-night diesel semis surrounding you.

What I don't understand with Roadtrek is shutting off multiple battery banks to conserve parasitic loss. Does that mean you have to get up several times in the middle of the night to manually switch them on and off?

[GeorgeRa]

Originally Posted by Davydd

..................
What I don't understand with Roadtrek is shutting off multiple battery banks to conserve parasitic loss. Does that mean you have to get up several times in the middle of the night to manually switch them on and off?

Me neither, if these parasitic losses are due to the high current draw relays than the answer is to use little more expensive bi-stable relays. If ARV can make Li banks without these losses, I assume, than it is possible in the 21st Century.

[Reed]

As noted on another thread, we have 415 W of panels on 2002 19' Roadtrek with 4.5+ kW-hrs of LFP and a 2.5 kW PSWI. We can run the AC for about two hours as combination of solar and battery suite. We have not had to do more than this. It is nice to have the 2.5 kW Onan in case we have to use more AC. We spent 14 weeks in Labrador/Newfoundland last summer and did not require AC. We spent 14 weeks in Mexico (Yucatan, Chiapas, and West Coast) and did need the AC to cool down cabin in the evening for 20 minutes or so in a number of places.
Reed and Elaine

[cruisefx]

Originally Posted by Reed

As noted on another thread, we have 415 W of panels on 2002 19' Roadtrek with 4.5+ kW-hrs of solar and a 2.5 kW PSWI. We can run the AC for about two hours as combination of solar and battery suite. We have not had to do more than this. It is nice to have the 2.5 kW Onan in case we have to use more AC. We spent 14 weeks in Labrador/Newfoundland last summer and did not require AC. We spent 14 weeks in Mexico (Yucatan, Chiapas, and West Coast) and did need the AC to cool down cabin in the evening for 20 minutes or so in a number of places.
Reed and Elaine

How many batteries and why type do you have (AGM or Lithium)? What is the total amp-hours of your battery setup? And this is using the original Kool Cat air conditioner?

[Reed]

Originally Posted by cruisefx

How many batteries and why type do you have (AGM or Lithium)? What is the total amp-hours of your battery setup? And this is using the original Kool Cat air conditioner?

Cruisefx

Edited our original post, it should have been 4.5 kW-hrs of LFP. These are two Manzanita Micro 180 amp-hr (12 V nominal) in parallel so 360 amp-hr, 4.4 kW-hr at 12 V or 4.3 kW-hrs but float is 13.6 V or 4.8 kW-hrs. Manzanita Micro battery is nicely packaged 4 x CALB cells with excellent BMS.

Our 5th wheel has four of these batteries in series (48 V) with 1410 W of olar.

The AC is original. Have note that a lot of folk have gone to mini-splits with far less power requirements
Reed and elaine