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Old 01-01-2019, 03:25 PM   #1
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Default What does "fully charged battery" mean?

It is a new year, and I am sure there will be some folks that are planning to update or replace their batteries and/or charging systems so I think this is a very valid question to ask everyone, as it goes to the heart of battery, charger, monitoring, and use in our vans.


I think we may find that there are a lot of different ideas, based on what we see in various discussions of related topics.


As an example, one of the very common comments made in other discussions is along the lines of "I do XXXXX and my batteries are fully charged", which in itself is a very relevant piece of information that could be very useful to anyone trying to improve their own system. IMO, the usefulness of the statement goes way down when there is no explanation of how it was determined that the batteries got "fully charged", as personal experience has convinced me that getting fully charged is not really very easy with equipment that is readily available to us at this time. Others will disagree with me on that. There are lots of discussions on this forum of different charging and monitoring subjects, so lots of interesting information is available by searching.


The fact that all of the discussions here stay around essentially forever is what makes it more important to give some detail to the subject, IMO, as folks will be searching in the future and could easily be confused by various claims or comments.


So, what does "fully charged batteries" mean to you in your real world camping? There are no wrong answers to this question



An example may be as simple as "I run a (brand and model) smart shore charger cycle and it goes to float, so the batteries are full".
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Old 01-01-2019, 04:15 PM   #2
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It is intriguing to read "There are no wrong answers..."

i was under the impression one needs to use a battery monitor (a good one) and let the batteries sit for a good while - then take a reading with no load on them to determine state of charge... not so?
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Old 01-01-2019, 04:20 PM   #3
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"Fully charged" means my TriMetric meter is satisfied the umpteen parameters I plugged into it, including a bit of overcharge, have been satisfied.
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Old 01-01-2019, 04:35 PM   #4
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Fully charged:
For lithium it means 14.5 volts and 20 amps acceptance for a 200AH battery bank.

For lead acid it means 14.4 volts and 4 amps acceptance for a 225AH battery bank
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Old 01-01-2019, 04:56 PM   #5
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My van AGM's: 14.3V & less than 1 amp acceptance for approx 400Ah bank. I can't seem to get to 14.4V & less than 1 amp with the PD charger so 14.3V & less than 1 amp will have to do.

For the Class A: 14.4V & less than 4 amps acceptance for approx 400Ah bank. There are some basic loads that I don't turn off so it is likely closer to 14.4V & less than 2 amps acceptance actually.
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Old 01-01-2019, 06:59 PM   #6
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I have two 6v AGMs. Fully charged is a reading of 12.8 volts with no load and about 30 minutes after any charging source has been removed. 50% charge is 12.3v under the same circumstances. I try not to take the coach batteries under 50%.
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Old 01-02-2019, 12:43 AM   #7
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Quote:
Originally Posted by hbn7hj View Post
Fully charged:
For lithium it means 14.5 volts and 20 amps acceptance for a 200AH battery bank.

For lead acid it means 14.4 volts and 4 amps acceptance for a 225AH battery bank
Interesting conversation! Maybe I can learn something!

Could you please elaborate on the terminology.

When you say 14.5 v and "20 amps acceptance for a 225AH battery," Does that mean that a fully charge battery could initially accept a load of 20 amps whilst still retaining a terminal voltage remains of 14.4v? If so, for how long?

Just trying to understand! ............. Thx.



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Old 01-02-2019, 01:16 AM   #8
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There are many charts on the Internet, and most seem to say OCV of 12.7 for flooded batteries and 12.8 for AGM. However, odd as it may seem, I believe it depends on the battery. I bought a flooded lead-acid battery for a friend's car, and the OCV was 12.96 and I did my best to remove any surface charge. Even a week later it was 12.90.
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Old 01-02-2019, 02:05 AM   #9
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Quote:
Originally Posted by Wingeezer View Post
Interesting conversation! Maybe I can learn something!

Could you please elaborate on the terminology.

When you say 14.5 v and "20 amps acceptance for a 225AH battery," Does that mean that a fully charge battery could initially accept a load of 20 amps whilst still retaining a terminal voltage remains of 14.4v? If so, for how long?

Just trying to understand! ............. Thx.



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Acceptance means charging current, not load current.
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Old 01-02-2019, 01:57 PM   #10
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Quote:
Originally Posted by ManWonder View Post
It is intriguing to read "There are no wrong answers..."

i was under the impression one needs to use a battery monitor (a good one) and let the batteries sit for a good while - then take a reading with no load on them to determine state of charge... not so?

The "no wrong answers" is intended to mean that this is not intended to be a discussion of the technical end of whatever methods are the best/most accurate, but only to collect information on how the various members are determining if their batteries are fully charged to put some context to the many times we see posts that describe batteries as fully charged but with no explanation of how "fully charged" was determined.



In keeping with the idea of no tech discussion here, I will send you a PM as I think you may have misinterpreted some of the monitor and voltage testing discussions.
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