Low Solar Yield Solved? ('22 AI GT)

[WBB]

I thought I would share my experience in (potentially) solving my solar charging mystery. (Sorry, this is a bit long)

Caveat – I am not trained in solar systems and certainly not an expert. Read your manuals, check with Airstream, check with Battle Born to make sure you don’t have other issues and/or avoid damaging your system.

We have a 2022 Airstream Interstate GT with 300 watts of solar for the house batteries and 200 Ah of batteries and no shunt. We generally drive every day in the van, but when we do not drive for more than a day we never seem to generate enough solar for more than two days parked, even though we rarely watch TV or play the house stereo. Recently, the batteries cut off due to low voltage in the morning after two nights parked in Crested Butte (75 degrees) with very bright sunshine and no clouds all day every day. The history showed daily yields from the solar ranging from 0.030 to 0.070 KWh, with one day being 0.220 KWh. So enough energy to power a 60 Watt light bulb for 0.5 to ~3 hours. Not much.

When we arrived home after a five hour drive, I left the fridge and freezer on, cleaned the panels and parked in the sun. The third morning the batteries cut off due to low voltage. In addition, the Bulk charge time was less than two hours and in the early morning when the yield was pretty low. Here are the results

Bulk time 1:37
ABS time 0:03
Float time 11:15
Battery current max 2.3 A
Panel power max 70 Watts
Yield 0.050kWh (<4 Ah)

After looking at the Battle Born manual, I noticed the absorption voltage (the voltage at which the Victron system switches from Bulk to Absorption) was set to the minimum recommended of 14.2 Volts (Battle Born recommends 14.2 to 14.6). I changed the Absorption voltage to 14.5 volts and the first day I did not see much change I assume because the charge controller resets the charge algorithm daily. The second day, there was a HUGE improvement:

Bulk time 11:20
ABS time 0:54
Float time 00:00 (system did not fully charge batteries in a day)
Battery current max 14.4 A
Panel Power Max 214 Watts
Yield 1.000kWh (~75 Ah)

So this change improved my yield from enough energy to power a 60 watt light bulb for 50 minutes, to 16.7 HOURS. It took a few days to fully charge the system with no power on, but it seems, under very good conditions, the 300 Watts of solar can replenish about 75 Ah, or 38% of the batteries’ 200 Ah capacity.

If you have suggestions to generate more power from the system, please let me know.

[SSquared]

Welcome to Airforums! We are glad to have you with us.


What a big difference a small change made! I'm glad you are finally getting some decent output from your panels. I hope it was just a mistake Airstream made configuring your one coach, rather than something the do to every AI they ship.


My Airstream is an older trailer with aftermarket solar, so I don't have any suggestions that relate to your van.

[3OnOurWay]

Hi there, thank you for posting this and explaining it so thoroughly for us to consider in our own systems.

I have the same MH as you just in the GL configuration

welcome to the Forums.

[JeffKim]

Welcome as well!

I'm a little puzzled about why changing the absorption voltage a bit made that much difference and it might be hard to know for sure without a shunt. It sounds like your batteries might have been fully charged and so the solar charger was not doing any charging then the batteries got discharged and then the charger kicked in and you saw a big increase. But then you say the batteries cut off. How low was the voltage? Do you mean you had no DC power? Without a shunt it's really hard to determine the state of lithium batteries just looking at the voltage.

The way the solar charge controller works with a lithium profile is it will charge increasing the voltage and maximizing the current until it reaches the bulk/absorption voltage (14.2V in my case), then it switches to float. When it reaches peak voltage, the batteries are pretty much charged. BB has a good explanation here. So changing this voltage shouldn't make a huge difference in the output of your solar panels.

We have a trailer so we might be a different animal and I'm not sure how your camper is set up. We have 4x100Ah lithium batteries (not BB), shunt, and 300W of rooftop solar. Our solar controller is a Victron Smart 100|30.

As an example, I went out to the driveway (on a sunny day here in pleasant 78F Minnesota) and here are the readings I'm seeing with our rooftop panels. You should be seeing something like this if everything is working as it should when charging. I haven't had the trailer plugged in for a while and the shunt says were down to 70% or so. So, the panels are charging at the maximum they can in bulk. Note the voltage is 13.43V and the controller is delivering 15.2A.

The history shows that over the last several days it never reached 14.2V so it's been charging in bulk and an average of 1kWh or so. One battery is 1.2kWh so, a little less than one battery/day. Last are the settings I'm using. I used the default Victron lithium battery settings, I could probably optimize better for my particular batteries.

[WBB]

Jeff,

Thanks for the thoughts. The low voltage cut off for my BB batteries is 10.6 Volts. For whatever reason, before I changed the absorption voltage the solar charger would change from Bulk wat to early when the batteries are deeply discharged (less than an hour or two). Before going to bed each night when camping, I would check the battery voltage and it was always 13.1 Volts or so every morning. This is only 40% charged according to BB. After increasing the ABS voltage, I am seeing 13.3 Volts (90% charged). All estimates of course.

After a few days, the charger is in Float mode most of the day and the yield is down substantially because the batteries are fully charged.

I can't explain why this small change made such a big difference, but I am happy with the results. (Of course, I would love to have a shunt for a better understanding of what is actually happening!)

We are camping again this weekend so hopefully I will continue to see better production from the solar system.

-Bill

[GOUSC]

FYI - attached are pictures of AM Solar’s recommended settings for Battleborn batteries using the Victron BMV or Victron Solar MPPT. You’ll see 14.4V is the recommendation for Absorption and 13.5V for Float. It also shows all the other settings.

[WBB]

Thanks for this. I’ve got the Victron MPPT unit, so lower tech and no Bluetooth, but I’ll go through all the settings tomorrow. I really appreciate your help.

Bill

[3OnOurWay]

Originally Posted by WBB

Thanks for this. I’ve got the Victron MPPT unit, so lower tech and no Bluetooth, but I’ll go through all the settings tomorrow. I really appreciate your help.

Bill

Bill,

we did both upgrades. We did the Bluetooth MPPT controller and the Bluetooth smart shunt. Between the two I would say spend your $200 on the smart shunt and not the Bluetooth solar.

How has your buck boost been treating you? I’m considering changing it for the orion XS once it comes up on Amazon.

[WBB]

Yes, for $200 it would be great to have the shunt and know much more accurately the state of charge. Unfortunately, I've looked at the wiring diagram and Airstream routed ground wires from both batteries in different directions. This means, to install a shunt, I'll have to join them and route the ground through the shunt. A little more complex than I would have thought. (I'm a DIYer mostly). If you have pics of your installation, please share them.

As for the buck boost, I am not sure what it does so I can't comment. What does it do and how would I know if it is performing well?

Thanks,

Bill

[JeffKim]

Originally Posted by 3OnOurWay

Bill,

we did both upgrades. We did the Bluetooth MPPT controller and the Bluetooth smart shunt. Between the two I would say spend your $200 on the smart shunt and not the Bluetooth solar.

How has your buck boost been treating you? I’m considering changing it for the orion XS once it comes up on Amazon.

If you have the standard issue 150|35 Victron Blue controller, it can be replaced with the Bluetooth Smart 100|30 which is more than sufficient and you can sell the 150|35 on ebay and it's about a wash. That's what I did.

[uncle_bob]

Hi

When you mount the shunt, you *must* get a short cable to go from the battery negative to the shunt. The wires that are now on the battery simply move over to the shunt. Since you typically mount the shunt next to the batteries it's sort of no big deal.

Assuming it *is* a big deal, then the answer is to join the existing wires to the battery to another short cable and run that to the shunt. Yes, this depends a lot on just how your van is wired.

If you get the "cheap" shunt, it talks to your phone via Bluetooth. There is no display to wire and nothing to mess with that way. Most folks just use the phone app anyway so not having the display (and saving $70) works out pretty well.

Off to the voltages ....

The batteries are pretty much fully charged at 13.6V. Anything over that "bleeds down" fairly quickly after the charging is done. The only thing that really happens when you get up around 14.x volts is that the batteries go into equalization mode.

That all *assumes* that the voltage is being measured at the batteries. If it is being measured somewhere else you have to worry about current and loss in the wires. With a loose connection somewhere, you could easily have 14.6 "over here" and not have made it to 13.6 "over there". Welcome to why you need a multimeter

Fun !!!

Bob

[WBB]

Bob,

Thanks for the advice. You guys are re-igniting my desire for a shunt. Wish Airstream had put that in in the beginning. I think the dealer wanted $2k to install one which I thought was pretty ridiculous to install a $250 shunt.

The van has a negative cable running from each battery in opposite directions. If I go the shunt route, I have to combine them, run the combined negative though the shunt, then separate the negatives again to go to wherever the go in the van. I was thinking of using two bus bars to combine the negatives before and after the shunt. Sound correct?

Also, it seems like a good idea to have an enclosure for all of this. The batteries are located on the frame rails under the van. If anyone has done this, I would love to see pics of your installation.

Thanks,

-Bill

[JeffKim]

Originally Posted by WBB

Bob,

Thanks for the advice. You guys are re-igniting my desire for a shunt. Wish Airstream had put that in in the beginning. I think the dealer wanted $2k to install one which I thought was pretty ridiculous to install a $250 shunt.

The van has a negative cable running from each battery in opposite directions. If I go the shunt route, I have to combine them, run the combined negative though the shunt, then separate the negatives again to go to wherever the go in the van. I was thinking of using two bus bars to combine the negatives before and after the shunt. Sound correct?

Also, it seems like a good idea to have an enclosure for all of this. The batteries are located on the frame rails under the van. If anyone has done this, I would love to see pics of your installation.

Thanks,

-Bill

I'm just a trailer guy, so not sure how things are wired for you. Not sure I understand if you have a 12V system with 12V batteries, the batteries are in parallel and the negatives should be wired together at some point. Do the negatives terminate at a negative bus bar? If so, then that's where the shunt can go if you combine them on one side of the shunt.

The Victron Bluetooth shunt is $100, and there's a IP65 version if you do end up putting it outside, but not sure if it's waterproof enough (@UB has said no, in comments elsewhere).

[3OnOurWay]

Good evening I will dig posts of mine. W everyone here was a lot of help though there are extensive conversations about smart shunta on here and Airstream interstates.

One of the easiest videos to orinetate yourself is to take a look at actually is Bam Bam YouTube video AI 19 install. The video is useful only to gives you a visual of where the components / wires are laid out. It’s possible your GT is wired similar. Our GL was similair to their AI 19 don’t know how the GT wiring is different.

[uncle_bob]

Originally Posted by WBB

Bob,

Thanks for the advice. You guys are re-igniting my desire for a shunt. Wish Airstream had put that in in the beginning. I think the dealer wanted $2k to install one which I thought was pretty ridiculous to install a $250 shunt.

The van has a negative cable running from each battery in opposite directions. If I go the shunt route, I have to combine them, run the combined negative though the shunt, then separate the negatives again to go to wherever the go in the van. I was thinking of using two bus bars to combine the negatives before and after the shunt. Sound correct?

Also, it seems like a good idea to have an enclosure for all of this. The batteries are located on the frame rails under the van. If anyone has done this, I would love to see pics of your installation.

Thanks,

-Bill

Hi

Real simple answer to the wires:

Get a very normal ground bar connector. You see them all over the place in cars , trucks, and RV's.

Tie the two existing cables to that ground connector (out in the muck).

Tie a new cable to it (so it needs to have at least three positions ... ).

Run that cable inside the van and the new cable to the battery negative to the inside of the van.

Mount the shunt there.

Why?

1) Even the "waterproof" shunt really isn't designed for getting road muck / salt / water / mud / debris all over it. Much easier to move it "indoors".

2) If you mount the shunt under the van, the Bluetooth signal will be fine as long as you are lying under the van next to it. Go inside the van and the metal floor of the van will do a fine job of blocking the signal.

3) You just *might* (hint .... hint ...) want to spend $30 on a full disconnect switch. That sorta kinda needs to go where you can get at it. It would go in the same wiring you are "adding on" ( = goes in that ground lead).

Fun !!!

Bob

[wordenjt]

A possible cause could be a poor measurement of battery voltage at the controller. I would check to see that a meter directly on the battery agrees with what the controller thinks.

[3OnOurWay]

@WBB
I wanted to follow up because it seems like our solar was operating correctly up until beginning of July. I think we did a new SmartSolar software update then. For the last few weeks, we’ve been making 1/10 daily average

I think the software update did require me going into the expert settings and verifying that the settings were all correct for lithium batteries, that you have listed here and that I verified on Victron and BB.

I immediately saw my solar providing back to pre-July levels
Hope this helps someone

[WBB]

Interesting. A couple of questions.

How did you do the software update? I assume you must have plugged a laptop into the charge controller or used a USB thumbdrive?

Just curious. Even after driving quite a bit, the display in the van normally reads 13.1 Volts in the evening when we go to bed. From what I have read, it seems like it should be higher (13.5 V or so), but it could be the fridge is running or something that is lowering the voltage. So if you are dry camping, not plugged in, what voltage do you see at say 9:00 p.m. after the van has been sitting for the afternoon?

[3OnOurWay]

Hi
Hope this helps.

The software was iPhone based on the app.
Options seemed to be moved around or opened up under Expert which perhaps weren’t there before. My settings changed I now for sure between the multiple upgrades Victron pushed out.

I am not aware sure if there are separate device / hardware upgrades but I think those come from the software app upgrades .

Your 13.1 readings don’t seem correct. Do you have a smart shunt ? Our DCDC buck boost started acting odd ( would register a charge and then back off ) I have researched setting on Victron and Battleborn and gave up. We went to Orion xs. I can’t deal with a Windows laptop cord to update settings.

I can mimic the 9:00 pm sitting in my driveway / with / or without solar? I have. shut done solar b/c I am in midst of a cable change Orion upgrade.

[3OnOurWay]

I came out to our van, batteries that I haven’t been the best to in the last six months.

We are currently at 13.07 it was 24 hours ago, I took it off shore power The fridge has been running at setting four I believe and that’s all.
I am rerouting grounds through shunt and so could be missing a phantom load though in a few days I will know 100%