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Old 10-06-2019, 08:16 PM   #1
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Battery replacement

I just tested fully charged batteries by operating the toaster in my trailer and the charge percentage went to 40% immediately. The volts were at 12.2. Based on what I have read this is not acceptable and the charge even without high draw items lasts only a short time. I have 2 12 volt Lifeline batteries deep cycle AGM that are just over a year old. (Purchased trailer new in June 2018). Is this possibly a battery problem (needs replacement?) or something else? New batteries should last 5-6 years based on what Iíve read. And what would cause them to fail? Iíve read that one shouldnít let the charge go below 50%.

If the batteries need replacing, what recommendations would anybody have for the batteries? My usage would be boondocking occasionally for 3 to 4 days and running the furnace sparingly in the colder weather along with other basic power draws. I can not justify the added cost of lithium ion batteries.

Iíve checked for any recent posts and have not seen any on this subject. Thank you for any relevant information.
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Old 10-06-2019, 08:28 PM   #2
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Sounds like your batteries have sulfated and need to be equalized.
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Old 10-06-2019, 08:39 PM   #3
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Might be too much draw trying to use appliances like a toaster or microwave from lead-acid batteries. Lithiums would be a much better battery source if you really need to run big inverter loads.
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Old 10-07-2019, 08:07 AM   #4
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You bought top of the line AGMís. They should do far better than that. I would look at the converter ó it doesnít seem like the batteries are being adequately charged or, as noted, getting desulfated.

Measure the battery voltage on shore power, again after an hour and again after 12 hours. You should see different voltages indicating different charging rates.
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Old 10-07-2019, 08:20 AM   #5
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Quote:
Originally Posted by ctimberlake View Post
I just tested fully charged batteries by operating the toaster in my trailer and the charge percentage went to 40% immediately. The volts were at 12.2.
Clarifying question: Are you saying that you did the test while the toaster was operating? Voltage will drop when the batteries are under load. After using the toaster, put the disconnect switch in Store and wait an hour, then test the batteries again.

We are usually on shore power so I don't know what our AS batteries are doing most of the time. My bass boat uses 2 group 31 deep cycle batteries for the 24v trolling motor. I can go fishing for 5-6 hours and while I'm fishing the voltage will go down to 12.4 but after the hour long drive home they are back up to 12.6.
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Old 10-08-2019, 06:43 PM   #6
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Quote:
Originally Posted by richw46 View Post
Clarifying question: Are you saying that you did the test while the toaster was operating? Voltage will drop when the batteries are under load. After using the toaster, put the disconnect switch in Store and wait an hour, then test the batteries again.

We are usually on shore power so I don't know what our AS batteries are doing most of the time. My bass boat uses 2 group 31 deep cycle batteries for the 24v trolling motor. I can go fishing for 5-6 hours and while I'm fishing the voltage will go down to 12.4 but after the hour long drive home they are back up to 12.6.
Yes test was done with toaster (high draw) operating and fully charged batteries as they just came off shore power minutes earlier. I was trying to emulate an operating furnace motor (also high electrical draw) for a dry camping scenario.

I will try your suggestion you mentioned in addition to the one above of testing after one hour and then 12 hours.

I use shore power most of the time so batteries should stay charged and voltage normal. Of note, last winter I stored the trailer for one month, returned to a 100% charge. In "store" mode with solar panels while away.
I also used the furnace motor at night time (moderate temps of 40-45 outside) successfully with recharging during the day. It seems to me that sulfating is not the case if battery voltage is close to 12.8-13.0 while on shore power.

I do indeed appreciate all the replies to narrow this problem down.
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Old 10-08-2019, 06:50 PM   #7
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Battery replacement

Furnace draws maybe 200watts. Toaster on high is upwards of 1,200watts. Completely normal that voltage drops when under that much load using 2 AGMs.

Charge your batteries to include a minimum of 24 hours of float. Then let them sit for 4 hours or so at room temperature. Then check voltage. Should be 12.6 or better. If so you are fine.

BTW - 12.8-13.0 is the voltage being read based on your converter output while on shore power...... that is not an indication of if the batteries are sulfated or properly holding a charge.
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Old 10-09-2019, 09:49 PM   #8
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I conducted a test by disconnecting shore power and going to battery power. Battery was fully charged. I turned on the furnace and the voltage went to 12.4 and the charge percentage went to 65 to 70%.

Disconnecting shore power, battery voltage after one hour was normal at 12.7 to 12.8 volts. Charge was 90%.

All this seems normal however the charge percentage with any type of loan seems excessively low.
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Old 10-09-2019, 11:17 PM   #9
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Battery replacement

Your batteries are just fine.

Charge percentage displayed on the standard airstream display panel is very simply a crude guess based on voltage being observed. Low voltage = low charge percentage. But as youíve seen, just because you put a battery under load., which temporarily reduces its voltage, doesnít mean itís depleted of energy.

The monitor that comes in your airstream is very rudimentary.

If you really want to know what your actual battery charge % is, regardless of voltage being observed, you need to install a proper shunt / battery monitor like the victron BMV 712.

https://www.victronenergy.com/upload...2-Smart-EN.pdf

These devices actually monitor current in/out of the batteries... vs trying to guess state of charge based on voltage which can give false indication if there is high load or low temperature or both.

Have a read through section 3.3 of this doc:

https://www.victronenergy.com/upload...S-SE-PT-IT.pdf
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Old 10-10-2019, 02:12 PM   #10
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Hi

Worse yet .....

The point that voltage is monitored matters. If you sense it a bit away from the battery, the drop in your wiring gets into the act. Under a massive load ( > 100A) that drop can be a lot. Even at lower loads, it is not unusual to see a few tenths of a volt in the cabling.

Lead acid batteries "like" lower discharge rates. With typical ~200AH setups that equates to currents < 20A. Get above that and the capacity drops along with the voltage under load.

More exciting still, the "magic voltages" are all temperature dependent. By how much and at what temperatures depends a lot on exactly what model battery you have and what the target market was. Apparently Florida gets different batteries than Alaska, both with the same model numbers on them. A half volt shift from 80F to 30F is not at all unexpected.

If you are worried about your batteries, check them with a DVM at the battery posts. Do that after they have sat a while. See what you get. If you still are worried, pull them out and take them to a battery dealer for testing.

If indeed you are simply tired of your old batteries, Lithiums will give you ~2X the capacity in the same space. They aren't cheap. They are about the only way to make a significant change. ( = to me 10% is not a significant change).

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Old Yesterday, 08:39 PM   #11
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Thank you all

Well, many thanks for all the helpful responses regarding my AGM dry cell batteries. I was given the suggestion to switch off the charge converter CB (15 amp) while connected to shore power. This to simulate dry camping by letting only (full sun) solar replenish the batteries. A few small draw items took some battery power during the night time to include a one shot run of the furnace early morning. 65-70% and 12.5 Voltage was noted in the morning prior to the solar replenishment. By all I can tell, this is acceptable.
And yes the gauge inside the trailer is likely not that accurate. Will suffice for now. Be safe.
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