New batteries installed

[RV-Writer]

Originally Posted by Persistent

Your charger is working perfectly!

The microprocessor is doing its job to regulate and adjust voltage for fast charge and long battery life.

Thank you for posting your results.

I wish you good luck and happy trails ahead!

Thanks Paul.

One last question I hope.

IF a fully charged battery is 12.8 volts, how can I have 13.4 volts after 4 hours at rest? Is that normal and will it come down over time to standard 12.8v - wondering what I should expect going forward. For example: If it starts showing 13.0 for a couple of weeks or months is that something to be concerned about or is anything over 12.8v considered fully 100% SOC?

Thanks again

[Mark_K5LXP]

1. - Could be just surface charge, if you want to eliminate that put a light load on it for a minute and watch it count down. The bounce back up once unloaded will be more representative of terminal voltage SOC.
2. - Temperature - voltage of cold batteries is higher than warm batteries.
3. - They're not really at rest. Is something else charging it like a maintainer or solar panel?
4. - Chemistry of the battery. Differences in plate alloy and paste will have slightly different terminal voltages. Check the data sheet for what it should be.

Mark B.
Albuquerque, NM

[RV-Writer]

Originally Posted by Mark_K5LXP

1. - Could be just surface charge, if you want to eliminate that put a light load on it for a minute and watch it count down. The bounce back up once unloaded will be more representative of terminal voltage SOC.
2. - Temperature - voltage of cold batteries is higher than warm batteries.
3. - They're not really at rest. Is something else charging it like a maintainer or solar panel?
4. - Chemistry of the battery. Differences in plate alloy and paste will have slightly different terminal voltages. Check the data sheet for what it should be.

Mark B.
Albuquerque, NM

Thanks. I had my disconnects on. But I dnt have solar or a trickle charger or anything. I had all power turned off and my battery monitor showed no incoming volts while shut down for 4 hours. But, maybe its just new batteries showing higher voltage until they break in?

Next time I will shut off city power but not hit my disconnects to draw down some like i am boon docking to see if that stabilizes some. But basically, 12.8v is full charge and anything over that is not real power available but a surface charge/residual from previous charging?

I am thinking I need to boon dock some to let my battery monitor learn the batteries

Thanks

[Mark_K5LXP]

Full disclosure - I've never owned lifelines so not familiar with their nuances of operation. I would defer to their datasheet to see what to expect for terminal voltage state of charge vs temperature. No idea about their break in either. Trojan states their break in cycles for AGM and flooded but other brands may not. The only difference I've observed with new batteries is reduced capacity for the initial series of cycles, nothing specifically with voltage.

First thing I'd do is verify the terminal voltage at the batteries with a known good meter. I don't trust battery monitors until I get a chance to see them in operation. My RV came with an outboard one the previous owner installed and it was consistently a quarter volt high for no apparent reason, so I yanked it.

Absolutely do some driveway camping with these and get a feel for what loads impact the system and how long you can comfortably run whatever it is you run. Having that familiarity will go a long way towards stress free camping when you're actually off the grid.

Mark B.
Albuquerque, NM

[Persistent]

Originally Posted by RV-Writer

Thanks Paul.

One last question I hope.

IF a fully charged battery is 12.8 volts, how can I have 13.4 volts after 4 hours at rest? Is that normal and will it come down over time to standard 12.8v - wondering what I should expect going forward. For example: If it starts showing 13.0 for a couple of weeks or months is that something to be concerned about or is anything over 12.8v considered fully 100% SOC?

Thanks again

Different battery designs behave a little different. Well used batteries behave a little different from new ones.

Fully charged will be 12.7 volts or higher. Some batteries will not stabilize higher than that.

12.4 volts is the typical recommended low limit for batteries in long term storage. Recharge for 14 to 18 hours before voltage drops to 12.4.

Lead acid AGM batteries deeply discharged to 11.4 volts and recharged over a few days will last for years and should provide 300 to 400 recharge cycles.

Batteries discharged below 12.4 volts and stored for a month or more will soon loose much or all its ability to work.

My pair of Interstate Marine AGM batteries hold voltage above 13.0 for a long time when disconnected as well. I choose to recharge at 12.7 volts.

Not all batteries will hold stable voltage above 12.7 volts. You now have some experience with your particular system. You now know what to expect.

It all has to do with lead acid battery chemistry. Discharging a lead acid battery dissolves lead from one set of plates, combines it with a sulfur ion from the acid and deposits it on the other set of plates.

Recharging reverses that process.

The lead sulfur compound on the plates has a tendency to slowly form larger crystals. The larger crystals are difficult or impossible to re-dissolve. Sometimes the crystals fall off the plates and accumulate in the bottom of the battery.

The deeper the discharge the thicker the sulfate deposit and the faster crystals enlarge. The longer the battery is stored with a thick deposit, the larger the crystals.

12.4 volts is recommended for storage because at that level the sulfate layer on the plates is relatively thin. However, it takes a long time charging to get that thin layer off the plates so 14 hours is typically recommended.

Battery University https://batteryuniversity.com/

How does the Lead Acid Battery Work? https://batteryuniversity.com/learn/...ased_batteries

Charging lead acid batteries https://batteryuniversity.com/learn/...d_acid_battery

AGM https://batteryuniversity.com/learn/..._glass_mat_agm

How to Charge and When to Charge? https://batteryuniversity.com/learn/...o_charge_table

How to Store Batteries https://batteryuniversity.com/learn/...tore_batteries

Summary of Do’s and Don’ts https://batteryuniversity.com/learn/..._battery_table

How to Measure State-of-charge
https://batteryuniversity.com/learn/...tate_of_charge

I wish you good luck and happy trails ahead!