What's running my battery down?

Ablezerosix

Greetings from a 2021 Tab320S new owner.  Forgive me if this is a dumb question but I'm in the process of learning how the electrical system operates.  Right now, the Tab is sitting in my driveway, since I bought it a few weeks ago.  On a sunny day the battery will charge and read full.  However, overnight the battery gets low.  The fridge and everything else is turned off.  The only things that I think are pulling current are little LEDs in the TV and what-not. Shouldn't the battery hold a charge with nothing turned on for a couple weeks, at least?  Thanks for any info on what could be draining the battery. 

pthomas745

There are no dumb questions, and welcome to the Forums.

Tell us...what battery do you have?  I'm guessing a "stock" battery.  Open up your battery box in the front tub and have a look.  Most likely, it is a "12v, Group 24, 80 amp hour deep cycle battery".  This is/was the same battery many thousands of 320 owners had installed in their trailers.

What are you using to monitor your battery?  Your 2021 has solar, and a Victron solar controller.  When you say the "battery gets low", what are you using to determine that?  The Victron solar controller has a bluetooth app that will help you to monitor your battery.  You might be using a multimeter.  If you are using the Kib monitor in the trailer...that is ok, but not very accurate. 

Let us help you get the Victron app running on your phone.  If you don't have the passwords the original owner used in the App, some hoops will have to be jumped to get it reset for you. But, the Victron app, or, even a multimeter, used correctly, will help you know a lot about your battery status.

What you are seeing "overnight" as the battery "drops" is called "parasitic drain".  You guessed it: the LED's and What-Nots are what the parasitic drains are.  There are some devices in the trailer that are never completely off.  The carbon monoxide detector, for example, is always on.  These parasitic drains are not very much, but, over time, they can add up.  In my 2017, my trailer, just sitting there with the battery switch on, nothing running and no power coming into the trailer, adds up to about 1/4 of an amp per hour.  So, over 24 hours, about 6 "amp hours". 

This is what you are seeing overnight, or about those 12 hours when the solar is not charging the battery, until the sun hits the panel the next day.  If you have that 80 amp hour battery we mentioned....and your "parasitic drain" was say, 10 amp hours overnight to make the math easier...that would be about 10 percent of your total amp hours in your battery. (It is a bit more complicated than this, but you get the idea.)

You are correct that a healthy battery should hold a charge "with nothing turned on" for quite a long time.  But: unless the battery disconnect switch in the trailer is off...those parasitic drains mean the trailer is still "turned on".  If your solar did not get enough of a charge to replace the "parasitic drain" each day, the battery could eventually drop to a very low "state of charge" that can become problematic for the health of the battery, and things in the trailer may stop working on battery power.  (If you did not have solar, and left your battery switch on....the parasitic drains can take a "stock" battery lower than what is good for the battery in less than a week or so.)

Have a look at your battery and tell us what it is.  Most likely, it will have some sort of designation with the number "24" on it.  Do you know how old it is?  Think it might have been replaced with something larger?  Take a picture if you want.

Do you have a multimeter?  Found the Victron app?

Again: do not hesitate to ask questions!

https://www.victronenergy.com/victronconnectapp/victronconnect/downloads

Ablezerosix

Yeah, it's got the stock Interstate SRM-24 12v deep-cycle battery.  I have the Victron app working on my phone and it shows good voltage from the solar panel.  I'm just using the control panel in the RV to look at the battery level.  I'm thinking maybe pulling the fuses on some things to reduce the drain, but it's hard to believe a few LEDs would run the battery down so fast. 

pthomas745

Ok, good.  The Victron app should be your preferred voltage monitoring tool.  The trick about a lead acid battery is: if the battery is being charged...the only thing your tool will measure is the charging voltage going to the battery.  If the battery is being "discharged", even by the small amount of power used by these parasitic drains, the voltage readout is going to be automatically "false", and depending on what is being used by the battery, will always read lower than actual.

The only way to get a good readout of a lead acid battery is with the battery "rested":  No charging, and no power going out of the battery.   So: battery switch off, and in the Victron app settings, turn off the "Charging enabled" toggle for a few minutes.  Let the voltage settle a bit, and as it stabilizes it will settle down to a more "accurate" reading. 

There are many threads about owners using various switches to reduce the parasitic drain on the Jensen units, etc.

Ablezerosix

Thanks very much for that information.  I plan to start camping later this summer in Montana and I want to know how everything works before I do. 

pthomas745

You have a good start with the App, etc.  The real balancing act is between the power use of the 2 way fridge and the 80 amp hour battery.  The 2 way fridge can eat up about 25-30 amp hours a day, and solar can sometimes not keep up with that power use.  So, practice a bit with the solar/battery/fridge in use and see if this works out for you. 

Tdfhammond

This information has been very helpful for me, as mine is exactly the same. I let the battery completely deplete too many times and now need a new battery.   2021 Tab S with original battery.  What would you suggest as a replacement battery.   I very rarely camp with hook ups and have been fine managing power until recently as the battery isn't holding a charge.   I've got the 105w solar on the tab and have an additional suitcase 100w zamp.  Use a generator when needed but that use to be rare. For now, my husband pulled a battery from his boat but I need to give that back:)  I'm happy to replace it with whatever is best. What do you suggest?  Thank you

pthomas745

If: you like to camp without hookups, and you have the 2 way fridge, the best bet would be a 100 amp hour lithium battery.  Your "original" battery was most likely an "80 amp hour Group 24" battery.  From that battery, you could draw 40 of those amp hours routinely. But running a lead acid battery below that number of amp hours too many times, or allowing it to stay in a low state of charge, will lead to a shorter life.  But: you made it for three years, so you must have been doing something correct!  And, the 200 watts of solar helped support your battery also. 

A 100 amp hour lithium would let you more than double your "usable" amp hours, from the 40 in your lead acid battery to about 90 amp hours in a 100 amp hour lithium.  There are several lithium batteries that are now the same basic size of your "Group 24" battery and will drop right in.

You will need to make sure your Victron solar controller is re-configured to handle the charging parameters of a lithium battery.  Same thing with your Zamp solar controller.

You will read about "non-compatible" converters in the Tabs that will not "completely" charge a lithium battery.  My 2017 will only charge my lithium to around "85 percent".  I do have a separate lithium charger, but over 99 percent of the time I just let my solar keep my lithium charged.

Many owners have been helped by reading and watching Will Prowse.  His videos and battery recommendations are extremely helpful (at least they were for me) and the page is mentioned many times here. Here is the review of the LiTime Mini mentioned above.

https://www.youtube.com/watch?v=jR5MkFRSucc

Here is the Will Prowse battery recommendation page.

https://www.mobile-solarpower.com/lithium-batteries.html

Welcome to the Forums.  Ask questions!  This can get confusing.  Once your husband sees how nice the lithiums are, he will want one, too!

ColleenD2

Can you clarify what "the battery disconnect switch in the trailer is off" means? Thanks. We've tried boondocking and within an hour the victron alarm is going off. And with nothing knowingly running. Should we flip the dial in the front tub to off after dark? We'd love to be able to run a Cpap. I might just buy one of those power box thingys.

pthomas745

In your 320 the battery disconnect is the switch in the front tub near the battery.  What "Victron" alarm is going off, and what is the Victron app saying about your state of charge?  Is your battery the original 2019 battery?

Marceline

ColleenD2 said:

Can you clarify what "the battery disconnect switch in the trailer is off" means? Thanks. We've tried boondocking and within an hour the victron alarm is going off. And with nothing knowingly running. Should we flip the dial in the front tub to off after dark? We'd love to be able to run a Cpap. I might just buy one of those power box thingys.

Be aware that if your battery is turned off or is depleted, you will have no working CO/LP detector, which is fairly dangerous in a confined space with propane appliances.