Front A/C while driving using SOLAR + ALTERNATOR

[joes2901]

C.Martin,

Does your solar controller have the ability to act as a slave power source that matches the voltage from a master source like the MS2812 charger or the alternator?

That may solve the problem seeing a higher voltage from another source and shutting off. You would also want AGM batteries that could accept all the charging power available to them.

I set my Outback solar controller to operate in slave mode. Outback's design allows multiple solar controllers to work together as a team. Multiple controllers work well when the available solar power is more than a single controller can handle.

[followingsea]

Originally Posted by garyspang

The soft start computer controlled start circuit, instead of quick start, is the solution I did not know about at that time. This is definitely the way to start any mobile A/C unit.

I would think that any one with this costly damage would be a little more skeptical of slick sales people selling you expensive gear.

Clearly soft start has the same failure mode.

The old school solution is to match the generator to the load.

So if you are in the middle of the ocean, drop the load, scram the reactor, and dead in the water what do you want? I want a f'n diesel generator with muscle to restart my reactor coolant pumps.

Air conditioning requires muscle. It has mass. So if you bought a very expensive Japanese gen set that purrs, junk it! Go buy something with muscle.

I have an hard time understanding folks with a 450 HP Cummins with muscle to spare opting for silly stuff. Be skeptical of slick sales people selling gadgets.

[followingsea]

Originally Posted by C.Martin

..but it’s fun experimenting and learning more and more.

I understand and can respect that. Certainly a cheaper and safer idea than sky diving. Of course that is the case of justifying one bad idea by comparing it to an insane idea.

I met my first Tesla owner. He told me that it accelerates faster and cheaper than the Camero he was looking at. This like the time I drove my wife's Corolla to work. The young German engineer had the hood up on his new Mustang. Parked next to him was an old engineer with the hood up on his new Camero. I parked next to them and raised the hood. Want to see a good engine?

My son did not like driving his mothers car. That is until he had to start buying his own gas and no car payment.

My toy is solar powered too. The sun creates wind. The wind creates a differential pressure on the sails and drives the boat down the water.

I also think experimenting is fun. Not a hobby, I got paid. I did have to report the results. One experiment I did not get paid for was the solar system I designed and built. What did I learn? I learned I could not make an honest living in the US. Find me a country with no lawyers, no worker safety, and cheap labor but who wants to live in China.

I like redundancy too. My redundant system for air conditioning is Hampton INN. We were boat camping when there was a heat advisory. On the way to the hotel we went to the ER and DW got her first stints put in.

So yes I think air conditioning is important especially for older people. While you may love the concept of solar it is not going to get the job done.

[C.Martin]

STOP

I just want to share my latest data collection...and raise a few flags.

Does this mean that running the A/C off solar plus Alternator isn’t viable??? I leave it to you to do your own research. This is what concerns I have to address.

I attached the Clampmeter on the cable going from the House Bank to the bi-directional relay. I had a few cycles that were well within what I would consider to be very reasonable parameters. But I had some interesting excursions.

For around twenty minutes...170 to 180 amps were being transferred to the house bank from the Alternator. I had a peak reading of 210 amps.

I knew from looking at the ME-ARC meters that the Inverter would be drawing around 160A with the A/C running. I display my solar output while driving on the Victron Connect App...and I routinely get over 75 to 85 Amps of Solar contribution. This, in theory, means we should only require another 80A from the Alternator to balance the load. The theory, however, doesn’t translate to the data I have collected.

I do believe the MS2812 can handle the load...I believe the Alternator can handle the load. My concerns now lead to two other areas.

Batteries. Flooded Lead Acid batteries aren’t the best for sustaining high rates of charge/discharge. When the A/C makes it’s demand the Inverter battery amp draw spikes. One was -177A...the other -185A. It doesn’t last very long...but it’s more than 100A for about four minutes in each recorded spike.

Cables... we have a rather long cable that goes from the House Bank to the Chassis Bank with the Bi-directional relay in the middle. This cable is carrying more Amperage than I originally anticipated. It was really designed to share charging duties...not an air conditioner load. What gauge is the cable? What ampacity? What is protecting it? Each coach can be different. Our 40ft coach has 2/0 welding wire rated at 105 degree C. It looks like it should handle 225A...and we are good there.
The relay should handle 225A. We are operating within these limitations...BUT have you noticed that this cable run has ZERO catastrophic fuse protection??

The Inverter is fuse protected, the House Buses are fuse protected. The bi-directional relay line does not appear to have a fuse.

I have had zero problems running the Air Conditioner this way...I just was hoping it would stay in the more conservative area with regard to ampacity. I wanted to share the results I found so you can be better informed...perhaps take readings on your own...and make a personalized decision.

I would like to have some type of catastrophic fuse. Our bank is capable of a whole lot of short circuit amps. Can’t imagine it would be a pretty thing.

[NealC]

Charlie, I'd love to see the same tests with GEN + AC's and see if the same current is flowing through the lines. I'm not sure this is an isolated issue to SOLAR. Or is it?

[C.Martin]

Originally Posted by NealC

Charlie, I'd love to see the same tests with GEN + AC's and see if the same current is flowing through the lines. I'm not sure this is an isolated issue to SOLAR. Or is it?

Well...the generator would supply 120v...so it’s only drawing 12-14A thru 12AWG wire, and circuit protected. Running off Inverter...we are using 12 to 14v and reading as high as 210A thru 2/0 cable without protection (Alternator tied)... that’s were the difference lies. Our Solar wiring will protect itself, our House power to the Inverter will protect itself..the Alternator to the House...I’m thinking it won’t protect itself.

[CoreyinWP]

I wonder if the KA has different cable sizing in that area.

[Wbago97]

Originally Posted by C.Martin

Batteries. Flooded Lead Acid batteries aren’t the best for sustaining high rates of charge/discharge. When the A/C makes it’s demand the Inverter battery amp draw spikes. One was -177A...the other -185A. It doesn’t last very long...but it’s more than 100A for about four minutes in each recorded spike.

Is Peukert's law coming into play?
https://en.wikipedia.org/wiki/Peukert%27s_law

I have 1000AH of AGM batteries for a similar project.

[jcussen]

How bout something like this? Maybe a 200 amp model.
Might stop the spikes and give you protection as well.
https://www.delcity.net/store/Del-Ci...93071.h_194987

[C.Martin]

Originally Posted by Wbago97

Is Peukert's law coming into play?
https://en.wikipedia.org/wiki/Peukert%27s_law

I have 1000AH of AGM batteries for a similar project.

I’ve not been able to find any concrete specs that address it for our Lead Acid batteries. Most of the LiFePO4 batteries allow discharge up to their rated capacity. 100A for a 100AH...or possibly 800A for a 800aH Bank. Can’t find those specs for Flooded Lead Acid.

The internal resistance that causes Peukerts effect is what concerns me. I’m sure Heat is generated during high current flow...regardless of wether or not it’s current going in or current going out. Our Interstate’s recommend a max charge rate of C/10...Lifeline AGM’s are something like C*5. They have much lower internal resistance.

Perhaps the only thing I should worry about is putting a fuse on the Bi-Directional relay lines... Seems everything else is fine..just was hoping to balance the amp drain more evenly between Solar and Alternator. I’m sure the batteries can handle the amp spikes. I did see a document where they apply a C*2 load for 15 seconds to load test the batteries. On a 928aH bank that would be a ludicrous amount of amps. (Obviously, they were testing one battery at a time.)

[C.Martin]

Originally Posted by joes2901

C.Martin,

Does your solar controller have the ability to act as a slave power source that matches the voltage from a master source like the MS2812 charger or the alternator?

That may solve the problem seeing a higher voltage from another source and shutting off. You would also want AGM batteries that could accept all the charging power available to them.

I set my Outback solar controller to operate in slave mode. Outback's design allows multiple solar controllers to work together as a team. Multiple controllers work well when the available solar power is more than a single controller can handle.

No...our Victron controller doesn’t have a feature like that. It would be interesting to see how AGM’s effect the balance...having slightly higher charge parameters.

[Wbago97]

Originally Posted by C.Martin

I’ve not been able to find any concrete specs that address it for our Lead Acid batteries. Most of the LiFePO4 batteries allow discharge up to their rated capacity. 100A for a 100AH...or possibly 800A for a 800aH Bank. Can’t find those specs for Flooded Lead Acid.

The internal resistance that causes Peukerts effect is what concerns me. I’m sure Heat is generated during high current flow...regardless of wether or not it’s current going in or current going out. Our Interstate’s recommend a max charge rate of C/10...Lifeline AGM’s are something like C*5. They have much lower internal resistance.

Perhaps the only thing I should worry about is putting a fuse on the Bi-Directional relay lines... Seems everything else is fine..just was hoping to balance the amp drain more evenly between Solar and Alternator. I’m sure the batteries can handle the amp spikes. I did see a document where they apply a C*2 load for 15 seconds to load test the batteries. On a 928aH bank that would be a ludicrous amount of amps. (Obviously, they were testing one battery at a time.)

Whether they are AGM or flooded, you can use 50% of the rated capacity. I've seen conflicting some views on this, but I'll go with considering them the same in that regard for now. However, with Peukert's law, you lose voltage a lot more as you increase current. If you're constantly feeding those batteries enough to cover the it may not matter much until there is no solar, and alternators don't do as well when they get too hot.
Yes with lithium you can use much more of the rated capacity until the voltage drastically drops. They're the best option but a high initial investment. You have to decide if they will last as many cycles as the manufacture says...

[twinboat]

Originally Posted by Wbago97

Whether they are AGM or flooded, you can use 50% of the rated capacity. I've seen conflicting some views on this, but I'll go with considering them the same in that regard for now. However, with Peukert's law, you lose voltage a lot more as you increase current. If you're constantly feeding those batteries enough to cover the it may not matter much until there is no solar, and alternators don't do as well when they get too hot.
Yes with lithium you can use much more of the rated capacity until the voltage drastically drops. They're the best option but a high initial investment. You have to decide if they will last as many cycles as the manufacture says...

You can draw down flooded and AGM batteries to 20% state of charge, just like Lithium.

It just cuts there cycle life in half.

[Wbago97]

Originally Posted by twinboat

You can draw down flooded and AGM batteries to 20% state of charge, just like Lithium.

It just cuts there cycle life in half.Attachment 253728

The low voltage at 80% discharge may cause a problem for the inverter though, so it's not something I'd plan to do routinely.