AGMs losing power quickly in 2nd year with Tab400

themcgillcrew

Hello all,

We're into our 2nd year with our 2022 Tab400 with its dual 6V AGM batteries.  Last year we were delighted to find that we could go 2 or 3 days dry camping relying on our battery and solar combo.  This year however, we noticed that after one cloudy day and our battery power drops dramatically to well below 10V causing a scramble to keep our fridge running. 

Our trailer was stored outside, covered for 8 months (Oct - Apr) last winter (Ottawa, ON) with the battery disconnected from the solar.  

Did we wreck our AGMs?

bergger

We are at 3.5 years on our factory 6v AGMs in our 2021 400 and they are still going strong.  We store ours in a similar manner due to our long cold winters.  It is covered from late October until early May with the battery disconnect switch turned off.  This will shut down power to the trailer but will still provide solar to the batteries via the roof top panel.  Is this how you stored yours?  Or did you actually turn off the solar charge controller to keep it from providing solar to the batteries?  Even covered you should get a little solar power.  We did this for the first couple of years but last year I kept the trailer plugged into shore power most of the winter.  I would think your batteries should still be in good shape unless you consistently drain them down below 50%.  The AGMs can be drawn down as low as 80% but if you frequently go down 50-80% you can really shorten the life of the batteries.  It is possible that is what has happened to yours. 

We just got back from a weeklong trip in a very shady site with little solar gain.  We are pretty frugal with our electric when in shady sites but still used our inverter and 800watt drip coffee pot each morning.  The lowest our batteries got down to was 82%.  On that day I did hook up our portable solar panels to help get them back up to 90%.  But we do have the 3-way fridge and run it off of propane so we don't have the large electrical draw that your fridge will have.  Another reason I do like the propane fridge.  With the compressor fridge you may want to upgrade to at least 2 lithium batteries.  Going to 1 lithium won't give you any more usable power that the 2 AGMs gave you when brand new.  

themcgillcrew

Thanks very much for the thoughtful reply.  I didn't turn off the solar when we stored our Tab - just flipped the battery disconnect to the trailer.  I must admit, we did run down our batteries a few times.  The VictronConnect phone app for the solar controller has shown as low as 9V a couple times so we really got down there.  

I took the batteries out this afternoon and will have them tested tomorrow to see if we've done any damage.  I hope it's just us learning to manage things on cloudy days.  If we have to go to a portable solar panel or lithium down the road to keep boondocking, then so be it.

Enjoy your travels!

2022 T@b 400 BD  
2017 Toyota Highlander
Ottawa, ON

Marceline

themcgillcrew said:

Thanks very much for the thoughtful reply.  I didn't turn off the solar when we stored our Tab - just flipped the battery disconnect to the trailer.  I must admit, we did run down our batteries a few times.  The VictronConnect phone app for the solar controller has shown as low as 9V a couple times so we really got down there.  

That's really not great. You'd be better off to shut off the battery switch when you get down to 12.0v and go into tent camping mode than draw your batteries down that far. If you do a lot of boondocking I'd recommend adding a Victron SmartShunt so you can track power going in and out of your battery. And maybe a supplemental portable solar suitcase for when you're under the trees.

themcgillcrew

I removed our AGMs and took them to a batter specialist store.  Going in, they tested at 40% and 60% capacity which had me worried.  But yesterday, they called to say after charging (reconditioning), they were testing at 90%.  So back in they went. 

The only thing is now I can't get the VictronConnect iPhone app to find the solar controller.  I've been through all the usual Bluetooth steps but can't detect it.  I tried another phone, still not picking it up.  Am I going to have to pull out that drawer and hit a reset button?

Any advice would be appreciated.

pthomas745

We have seen the Victron bluetooth suddenly decide to quit when batteries have been reconnected or replaced.  The solar panel keeps the Victron "powered up", it seems, and reconnecting the "main" power to the controller confuses the Victron and...for some reason the bluetooth quits. 

There have been a couple of threads about this, but the "reset" is still a bit vague.  Generally, Victron wants you to disconnect the solar controller completely, and then reconnect with the battery cables to the controller first. (The negative cable from the panel and the battery would be sufficient, but also note the mention of just pulling the fuse from each cable going from the battery/solar panel to the controller would work, too.

There was this thread a couple of months ago.

https://tab-rv.vanillacommunity.com/discussion/16779/victron-connect-problem

themcgillcrew

Thanks!  Today I'll put the rear bed back together now that the AGMs are reconnected and scope out how I'm going to access the controller.  I can get a glimpse of it behind the drawer under our closet (we have the 12V fridge on the other side) but have to figure out how to get at it to perform the reset.

Keeps me out of the malls, I guess.

themcgillcrew

Success! 

I'm still recovering from having to stick my head and shoulders in the back of that drawer cabinet but I can finally see the controller on my phone.  I had to undo the mounting screws and the one wire support to get at the controller though.  Pulling the fuse alone didn't cut power totally so I disconnected the negative side for the PV then battery, reconnected battery then PV and voila!

Now for a beer then put everything back together.  

Thanks to all for your help.

pthomas745

You will be happy to know that "Tab Yoga" is actually a thing here. 

https://www.google.com/search?q=tab+yoga+site:tab-rv.vanillacommunity.com&client=firefox-b-1-d&sxsrf=AB5stBiTuyfunkxQgI_6pmbJ2wGsCqusYw:1691211578739&ei=OtfNZJfjLMXGkPIPvKOomAE&ved=0ahUKEwiX6I-L3sSAAxVFI0QIHbwRChMQ4dUDCA8&uact=5&oq=tab+yoga+site:tab-rv.vanillacommunity.com&gs_lp=Egxnd3Mtd2l6LXNlcnAiKXRhYiB5b2dhIHNpdGU6dGFiLXJ2LnZhbmlsbGFjb21tdW5pdHkuY29tSMwuUP0JWJMocAF4AJABAJgBTKABrAiqAQIyNLgBA8gBAPgBAeIDBBgBIEGIBgE&sclient=gws-wiz-serp

themcgillcrew

We just got back from a 2-week trip to the east coast and once again have doubts our AGMs are performing up to spec.  Is my math correct?

- 2 AGMs should deliver 220 amp-hrs or 220x12= 2640 watt-hours
- maximum discharge of 50% means we have 1320 watt-hours usable charge
- our Isotherm CR65EL fridge uses 23 amps over 24hrs or about 12 watts per hour
- so if the AGMs were performing as expected, I'd expect about 110 hours with just the fridge running
- adding in the water pump, occasional LED lights and other never-off items like radio and detectors, I should be seeing about 4 days without any solar input at all

4 days is definitely not what we're seeing so my concern once again is still we've damaged our AGMs despite what our local battery store says.

Am I missing anything?  

pthomas745

What is missing is the actual battery voltage you are seeing.

Are you watching the Victron app for battery voltage?  Are you taking voltage readings with the battery switch off, and no solar charging coming into the trailer?  There is no need to guess when there is a tool available that will give you fairly accurate "data". 

What did your Victron tell you?  What were your "rested" voltage readings?

manyman297

I’m my experience the refrigerator is the main power hog. Sometimes running constantly in hot weather. I think the Isotherm pulls 45watts max…maybe averages 30watts when cooling. On my last trip boondocking for only 4 days I had trouble maintaining enough charge without having to pull out the generator to top things off. Sun was spotty which was the main cause but you can definitely run these stock AGMs down in a day and a half or so if you aren’t able to get any solar input.

Horigan

@themcgillcrew
Your estimate of frig power consumption is too low. The DC refrigerator uses about 7 amps when running. (You should confirm in their documentation.  If given in watts, divide by 12). Depending on how hot it is, let’s assume it’s on 10 hours a day. That’s 70 amp-hours.  You only have 110 amp-hours available (using the 50% rule).  

rh5555

Also, see my earlier post: AGM battery Depth of Discharge myth busted.  You have more battery capacity than you think...

themcgillcrew

Thank you all for your help.  First off, I apologize for my inexperience with RV solar and electrical basics.  It's a gap I'm planning to work on.

For pthomas745:

Are you watching the Victron app for battery voltage?  
Yes.  I only recently started using the Victron app.  Last year, our 4-dot gauge never went below full but this year things seem to have changed so I downloaded the app.  During our recent trip, after a day of driving, the Victron app showed a full charge of 12.7V.  By 6am, it was about 12.4V and by 6pm it was almost done at about 11.5V.

Are you taking voltage readings with the battery switch off, and no solar charging coming into the trailer? 
That day, the battery cut-off switch wasn't engaged because we wanted the fridge to run.  The weather was very grey so not much solar would have been added.

For other commenters about the 12V fridge, here is what I've found on the power consumption for this model of 12V fridge:

Power consumption: 290W/24hrs with "instantaneous" consumption of 5amps at 12V (I assume that means when running).

What I'd like to do is more testing myself.  I can cover the solar panel to simulate a day of low or no solar input, flip the battery cutoff to the trailer and watch with the Victron app how the batter voltage drops.  Hopefully that will isolate the battery performance.

AnOldUR

themcgillcrew said:

I can cover the solar panel to simulate a day of low or no solar input, flip the battery cutoff to the trailer and watch with the Victron app how the batter voltage drops.

You can turn solar charging off in the app.

pthomas745

@themcgillcrew you found the same info I have always found concerning the power use of the Indel Cruise fridges.  290 watt hours divided by 12V would indicate a fridge power use for 24 hours of about 24 amps.  The charts, however, always tell you the measurements are at about 72 degrees ambient temps.  The idea on fridge use in many "real world" threads in this group indicate anywhere between 25-40 amps. 

I come back to the subject of "resting" a lead acid battery all the time because I think it is the prime cause of many "my battery is dying too quickly" threads.  If the battery is not "off": switch off...no charging....the voltage of a lead acid battery can swing wildly as it reacts to items running in the trailer or a cloud crossing the solar panel.  Trying to catch the voltage of a battery that is being used and charged at the same time is...impossible.

Below is a picture of my Victron readout with my (older) lead acid battery.  On the left, the battery switch is on, and the fridge is running at "medium".  A voltage of 12.01 would indicate a battery that has reached 50 percent state of charge. 

On the right, the battery switch to the trailer is off, with no charging coming in.  After only 10 minutes, the "rested" battery reading is 12.46, which would put the state of charge somewhere near the 85-90 percent mark.  If you aren't reading a lead acid battery when it is rested, you can see how easily the readout you will get from a voltage measuring device would be false.

Marceline

themcgillcrew said:

- our Isotherm CR65EL fridge uses 23 amps over 24hrs or about 12 watts per hour


Am I missing anything?  

I know that the Isotherm is supposed to be efficient, but this seems low to me, especially if the ambient temp was above 80deg. I have the little Norcold 2way that was original to my 2013 T@B CS-S and when it's hot (80+) I expect to burn as much as 40aH per day as the compressor has to work really hard to keep the fridge close to 40deg. In the middle of the day it's running almost constantly. The West Marine website says that your fridge draws 2.5amps. 2.5 X 24 = 60aH if it were running constantly. What percentage of time was it running? 

themcgillcrew

Thanks, AnOldUR.  That would be much easier.

Just to confirm, are you referring to the "Charger enabled" toggle on the Settings page in the app?  Flipping that will stop the solar input?

themcgillcrew

Thanks also for response Marceline.  We're in a cooler climate up here so I'd say our fridge is running only about 10 - 12 hours/day or using 25 to 30 amps/day.

themcgillcrew

And thanks again pthomas745 for your thorough post.  

Horigan

@themcgillcrew
 I think the 2.5amp value is incorrect, or is assumed an average over 24 hours.  Their technical data shows 6 amps when running (instantaneous consumption), but they also state it consumes 275W of power over 24 hours, which doesn't make any sense.  275 WHours over 24 hours would make more sense, but that then assumes the frig only runs for less than four hours per day, which is extremely low.  I think a good assumption is 10-12 hours running at 6 amps is typical for these 2-way fridges, which equates to 60-72 Amp-hours per day.  This would better match the behavior you're seeing with low solar energy.

See page 52 of their tech data.
https://www.indelwebastomarine.com/fileadmin/webasto__media/indelwebastomarine.com/INT/Documents/cr_classic-elegance-inox-inox_clean_touch_manual.pdf

Marceline

Horigan said:

@themcgillcrew
 I think the 2.5amp value is incorrect, or is assumed an average over 24 hours.  Their technical data shows 6 amps when running (instantaneous consumption), but they also state it consumes 275W of power over 24 hours, which doesn't make any sense.  275 WHours over 24 hours would make more sense, but that then assumes the frig only runs for less than four hours per day, which is extremely low.  I think a good assumption is 10-12 hours running at 6 amps is typical for these 2-way fridges, which equates to 60-72 Amp-hours per day.  This would better match the behavior you're seeing with low solar energy.

See page 52 of their tech data.
https://www.indelwebastomarine.com/fileadmin/webasto__media/indelwebastomarine.com/INT/Documents/cr_classic-elegance-inox-inox_clean_touch_manual.pdf

I'd be surprised if the Isotherm draws 6amps. My 10 year old Norcold draws 3.6amps when the compressor is running (I know this for sure thanks to my Victron SmartShunt). I would think that the newer Isotherm would be more efficient. Still, I think that we're in agreement that the assumption of 23aH per day seems too low. 

SLJ

Horigan said:

@themcgillcrew
 I think the 2.5amp value is incorrect, or is assumed an average over 24 hours.  Their technical data shows 6 amps when running (instantaneous consumption), but they also state it consumes 275W of power over 24 hours, which doesn't make any sense.  275 WHours over 24 hours would make more sense, but that then assumes the frig only runs for less than four hours per day, which is extremely low.  I think a good assumption is 10-12 hours running at 6 amps is typical for these 2-way fridges, which equates to 60-72 Amp-hours per day.  This would better match the behavior you're seeing with low solar energy.

See page 52 of their tech data.
https://www.indelwebastomarine.com/fileadmin/webasto__media/indelwebastomarine.com/INT/Documents/cr_classic-elegance-inox-inox_clean_touch_manual.pdf

The 2.5 amp would be correct. The 6 amps would be initial start up of the compressor. Maybe a second or two. That's the number you need for the size of the wire used. My Isotherm runs at a steady 2.2 amps when cycled on (compressor running) and that's only 50%-60% of the time around 80 degrees so if you figure less than that then lets say 1.5 AH. I've been running my fridge at 38 degrees. When it's 90 inside the fridge stays at 40 degrees and the compressor runs about 70% of the time. I run 200AH of batteries and I use between 20-35AH a day depending on outside temperature running the fridge, water pump, lights, TV/Blu-ray, and stereo. The lowest my batteries have ever been was 45% after five days of steady rain, no solar to speak of. I get constant a readout on my Renogy monitor/shunt and I've confirmed the accuracy with a calibrated meter.

AnOldUR

themcgillcrew said:

Just to confirm, are you referring to the "Charger enabled" toggle on the Settings page in the app?  Flipping that will stop the solar input?

Yes. With the switch off, no power will be sent past the controller from your solar panel. In the picture attached mine is off. When I'm topping off my LiFePO4's with a NOCO Genius10 I turn solar charging off to prevent any conflicts. Probably not necessary, but the NOCO seem to work better with solar off. Might just be my imagination.

AnOldUR

We get results similar to @SLJ from the 54qt chest fridge/freezer that we replaced our 3-way with. I measured our draw at 2.5 amps when the compressor is running, but the consumption during 24 hours is about the same.

Horigan

Thanks for the info.

themcgillcrew

Thanks all for the replies.  I'm testing my AGMs now isolated from solar input, shore power and trailer supply and it's holding it's charge well.

In the meantime, AnOldUR:  I'm curious how you're using your NOCO Genius10 to top off your batteries.  Are you digging out your batteries from under your bed or do you have another way to connect?

AnOldUR

themcgillcrew said:

I'm curious how you're using your NOCO Genius10 to top off your batteries.  Are you digging out your batteries from under your bed or do you have another way to connect?

My batteries are still in the tub, but what I did was install a cigarette port on the box that runs directly to the batteries. NOCO has an adapter for this type of port. You could just as easily add a similar port to your inside installation. It doubles as a place to plug in other 12V accessories like a fridge/freezer.

themcgillcrew

Very cool, AnOldUR.  In our 2022 Tab400 BD, we have a 12V cigarette lighter port inside our camper already.  I also have NOCO 2000A booster (not Genius) so would I be able to top off our twin AGMs the same way connecting that existing port to the booster output?

Horigan

@themcgillcrew
So in the end, what was causing the reduced battery performance that started this thread?  Was the Victron solar charger not turned on, or is it just a better understanding of solar performance on cloudy days?