12V Battery Charge Life

[JimW]

I have a new 2022 17MKE and wondering how long the 12V Battery should hold a charge when not connected to shore power. I left mine not connected to shore power and didnt leave any 12V items turned on except those that run all the time and I did not turn the battery disconnect switch off in the storage compartment. Two days later even the light on the power jack wouldnt light. I checked the battery with a volt meter and only had around 4 volts. Is this normal to die so quick? I reconnected to shore power and checked the battery 10 hours later and was up to 12V. If this is normal, it tells me I either need to add Solar or only camp where electric is available. Please give opinion. If this is not normal, I'll take it to Batteries Plus to get a condiiton print out and if bad take to dealer for replacement. Thanks for any replies.

[Country Campers]

Yes this is typical and also non typical. The battery disconnect does not actually disconnect the battery from the RV as you have found. The best way is to remove the cables , one or both, from the battery when in storage for more than a couple days. It is also best to make sure that the battery is fully charged before removing cables. If you store the RV with a less than fully charged battery and the battery power still flowing to the RV then yes it will be a dead battery in a couple days. I would have the battery checked, at 4 volts the damage may have been done.

Brian

[ThePowells]

JimW, Welcome to the family and the forum! For your trailer, you already have your answer. The battery disconnect doesn't actually disconnect everything. Your CO detector and other things among others. The only way to disonnect everything is to remove the negative cable. You will get a better experience if you turn off the inverter. It is suppling 110 to your smart TV, microwave, water heater if you haven't cut it off, and other assorted items. A single 12 volt battery is not intended for overnite camping, it is only intended to keep power to eveything while hooking and unhooking and other short term disconnects. You should have a minimum of 2 6V golf cart batteries for an overnite boon dock, but they will still have to be recharged. If you browse thru the electrical section there are multiple dozens of threads dealing with generators, batteries, and solar. Lead Acid batteries are quickly become "old technology".

[ncitro]

I have a new 2022 17MKE and wondering how long the 12V Battery should hold a charge when not connected to shore power. I left mine not connected to shore power and didnt leave any 12V items turned on except those that run all the time and I did not turn the battery disconnect switch off in the storage compartment. Two days later even the light on the power jack wouldnt light. I checked the battery with a volt meter and only had around 4 volts. Is this normal to die so quick? I reconnected to shore power and checked the battery 10 hours later and was up to 12V. If this is normal, it tells me I either need to add Solar or only camp where electric is available. Please give opinion. If this is not normal, I'll take it to Batteries Plus to get a condiiton print out and if bad take to dealer for replacement. Thanks for any replies.

As stated above, discharging lead acid batteries past 50% can cause permanent damage to them, down to 4V and the battery may be ruined. Get it tested and if needed replaced. If you are looking to do any kind of dry camping without electrical you should look at dual batteries (2 12V in parallel or even better 2 6V in series), or make the jump to lithium. Lithium can be discharged much further, some all the way to 0 with no damage.

[mpking]

I have a new 2022 17MKE and wondering how long the 12V Battery should hold a charge when not connected to shore power. I left mine not connected to shore power and didnt leave any 12V items turned on except those that run all the time and I did not turn the battery disconnect switch off in the storage compartment. Two days later even the light on the power jack wouldnt light. I checked the battery with a volt meter and only had around 4 volts. Is this normal to die so quick? I reconnected to shore power and checked the battery 10 hours later and was up to 12V. If this is normal, it tells me I either need to add Solar or only camp where electric is available. Please give opinion. If this is not normal, I'll take it to Batteries Plus to get a condiiton print out and if bad take to dealer for replacement. Thanks for any replies.

Hi Jim,
I actually read you message. (You left a red herring with the battery disconnect message).
It is and it is not normal.
My Imagine's idle state appears to power: (Trailer disconnect not enabled, but all switches off (Lights, H/W, Pump)

• CO/propane detector
• Fridge electronics
• H/W electronics
• Backup Camera (Need to move this to a marker light when I get a chance)
• Battery monitor
• Radio Memory
• Slide Controller

This all adds up to 13w (.98 A)

My Victron estimates my Crappy Group 24 Battery the dealer gave me will last 2 days, 17 hours. But that is running the battery down to the prescribed 50%. This might also have a bit of a surface charge, since I didn't let the battery sit. I just popped it off my electric hookup and took a measurement.



So yes, the battery only lasting 2 days, that is unfortunately true.

But to be at 4 volts after 2 days? That is not normal. Without a decent battery monitor (I highly recommend the Victron one ($130 from Amazon https://amzn.to/38376gt ) it's going to be hard to diagnose what's doing the excessive drain.

Even with a battery monitor, you'll have to pull fuses one at a time to isolate what your draw item is.

[JimW]

Thank you for all the replies. I understand now. I do think my battery has recharged ok and thinking of adding a negative battery post disconnect to keep it from draining when not needed or stored.

[Scott'n'Wendy]

you should look at dual batteries (2 12V in parallel or even better 2 6V in series), or make the jump to lithium. Lithium can be discharged much further, some all the way to 0 with no damage.

ncitro Why is two 6v in parallel better than two 12v in series?

Meant to say 6's in series and 12's in II

[Guest]

Two six volt batteries in series has more capacity where each 6v battery typically has higher capacity than one 12v battery. Only issue with 6v volt batteries is their weight. They are very heavy.

Batteries wired in series have their voltages added together.
Batteries wired in parallel have their capacities added together.

Here is one example of a 6v battery and its high capacity.

https://www.thesolarbiz.com/trojan-t...iABEgIQ4PD_BwE

Jim

[mpking]

ncitro Why is two 6v in parallel better than two 12v in series?

Not ncitro, but it's a matter of capacity.

A Group 24 battery (the cheap one the dealer gives you) has a reserve rating of 40amp hours (A/h) (The number is actually 80, but you are only supposed to use half to prevent damage to the battery, so I'm going to only use the safe numbers). Group 24's are decent sized, pretty heavy, and have a short life span. Price is around $88)

Two in parallel give 80 A/h. See the math? (Price is around $160)

Golf cart batteries. (Yes, the batteries to drive golf carts) are designed with even larger reserve capacities of around 100 A/h. But you need two of them to get the correct voltage (12volts). Because it's in series, you still only get 100A/h. They are MUCH bigger than Group 24's, MUCH heavier, but last longer. Price is around $300ish for the set.

OR you can buy a LiFePO4 battery, that would be same size as a group 24, lighter, and have a reserve capacity of around 100A/h. They also have a 10-15 year service life. Just really expensive compared to a Group 24, but the the prices have been dropping (Saw one advertised for $400 the other day https://amzn.to/3uoyDmY) You could do two LiFePO4 batteries for $800, but have 200A/h, and not think of it for 10 years.

[Guest]

mpking That price is excellent. I'm intrigued by their claim to use automotive grade cells. Typically all our lithium batteries (even the over-hyped battleborn) use B grade cells. But without information on the cell, all we can do is believe them....sort of anyway.

Jim

[StephenO]

Golf cart batteries. (Yes, the batteries to drive golf carts) are designed with even larger reserve capacities of around 100 A/h. But you need two of them to get the correct voltage (12volts) so that gives you 200A/h. They are MUCH bigger than Group 24's, MUCH heavier, but last longer. Price is around $300ish for the set.

Looks like you got a typo in there, in that two 6v batteries, with a RC of 100A/h each, in series still gives you an overall capacity of 100A/h. Your Amp Hour rating only goes up when you have batteries in parallel, like you have indicated in the beginning of your post.

[ncitro]

ncitro Why is two 6v in parallel better than two 12v in series?

Looks like everyone got here already, just wanted to clarify that two 6V ned to be in series and two 12V need to be in parallel. I also agree that the time of Lithium Iron Phosphate batteries is here. With the prices out there and the lack of maintenance, weight savings, full capacity use, and current allowed it is where things are headed, if not already there. I made the jump a few years ago and have not looked back. Particularly when inverters get involved you cannot beat their change and discharge current specs, but the lack of maintenance is what really did it for me. I am terrible at monitoring water levels and SOC when not in use, and because of that I was usually lucky to get three years out of my FLA batteries. After I did the math for full capacity and three sets of FLA in the lifespan of 10 years of lithium the cost difference worked out to about the same for me (I have 6 LiOn energy, four bought on an initial promo when they got started for $600 ea, and two this year at Costco for $700 ea).

[mpking]

Looks like you got a typo in there, in that two 6v batteries, with a RC of 100A/h each, in series still gives you an overall capacity of 100A/h. Your Amp Hour rating only goes up when you have batteries in parallel, like you have indicated in the beginning of your post.

Thanks. Fixed it.

[mpking]

mpking That price is excellent. I'm intrigued by their claim to use automotive grade cells. Typically all our lithium batteries (even the over-hyped battleborn) use B grade cells. But without information on the cell, all we can do is believe them....sort of anyway.

Jim

Or you can just cut the battery open. :-)

[mpking]

Here's the other low cost battery:

Since they both had a low temp charging cutoff fail, he has a solution for that: