Battery maintenance - Page 3 - Fiberglass RV


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Old 10-01-2013, 04:58 PM   #29
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Ed, I will be doing this. I am going with a solar system, and there are solar chargers which do fine job of intelligently charging the batteries, I just wanted to avoid buying a new 120v AC charger AND a solar charger.

I am in a spot at the state park where I have 120vac and SHADE. So I buy my solar system for when I go dry camping and yes, it does a fine job of keeping the batteries charged when the solar panels are getting sun, but while I am hooked up to AC (in the shade) the solar system will probably simply do nothing whatsoever.

While you say "not doing a lot of harm" that is not necessarily true. A battery sitting at a partial charge, with the solution slowly separating back into water and sulfuric acid does appear to actually damage the batteries. So I need an AC powered charger which correctly handles the charge duties.
I'm not sure. It is my understanding that a battery can and will be charged from multiple power sources simultaneously without causing harm. So you could have your solar panel and controller still hooked up and working while you're plugged into AC.

I am using my solar panel while the trailer sits in the back yard, instead of plugging into shore power and depending on the WFCO.

The thing I don't know is whether the solar controller will "see" the battery as needing the higher voltage charge, or if it will only give it a lower voltage maintenance charge, when the AC and converter are keeping the battery as charged as they normally do. You might have to get a meter and experiment with it a bit.

It seems to me that if you try that, and if the solar controller is not contributing like you want it, and if you are going to stay hooked to AC for enough days in a row that you feel your battery would be negatively affected, then you would want to add a new unit in the trailer. But there are some 'ifs' in there that you could cover before you shell out the bucks. Maybe you could even unplug for a while once a week (or however often you like) to 'goose' the solar controller into a higher voltage charge, just to keep the batteries in shape.

I am now using my solar panel instead of shore power/WFCO while my trailer sits in the back yard.
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Old 10-01-2013, 05:07 PM   #30
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I'm not sure. It is my understanding that a battery can and will be charged from multiple power sources simultaneously without causing harm. So you could have your solar panel and controller still hooked up and working while you're plugged into AC.

I am using my solar panel while the trailer sits in the back yard, instead of plugging into shore power and depending on the WFCO.

The thing I don't know is whether the solar controller will "see" the battery as needing the higher voltage charge, or if it will only give it a lower voltage maintenance charge, when the AC and converter are keeping the battery as charged as they normally do. You might have to get a meter and experiment with it a bit.

It seems to me that if you try that, and if the solar controller is not contributing like you want it, and if you are going to stay hooked to AC for enough days in a row that you feel your battery would be negatively affected, then you would want to add a new unit in the trailer. But there are some 'ifs' in there that you could cover before you shell out the bucks. Maybe you could even unplug for a while once a week (or however often you like) to 'goose' the solar controller into a higher voltage charge, just to keep the batteries in shape.

I am now using my solar panel instead of shore power/WFCO while my trailer sits in the back yard.
The source with the higher shut off voltage will be the one charging at the end. Before that point current can be drawn from all charging sources.
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Old 10-01-2013, 05:10 PM   #31
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I wonder how many people obsess over charging of your vehicle starting battery, their boat battery charging, their cell phone charging? Some how maybe trailers are special, eh?
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Old 10-01-2013, 05:26 PM   #32
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Byron, I obcess over the water level.
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Old 10-01-2013, 06:45 PM   #33
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Multiple charging sources will likely "confuse" a charger, if it measures only the current it is providing: it will see relatively high voltage and low current (since the other chargers are contributing) which looks to it like a nearly completed charge cycle, even though the battery may still be accepting a high charge current. The combination works, but I don't think it should be expected to work ideally for the battery.

Most people don't worry about their car battery charging system to this extent, but they also don't have to stop their recreational activity when the car battery charge runs out, and rarely need any significant fraction of the car battery's capacity.

Is any solution actually desired here, or is it just a rant? I'm okay with a rant, I just don't want to waste my time contributing to an unwanted solution.
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Old 10-01-2013, 08:20 PM   #34
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Byron, I obcess over the water level.
Of your cell phone battery?
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Old 10-01-2013, 08:22 PM   #35
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Multiple charging sources will likely "confuse" a charger, if it measures only the current it is providing: it will see relatively high voltage and low current (since the other chargers are contributing) which looks to it like a nearly completed charge cycle, even though the battery may still be accepting a high charge current. The combination works, but I don't think it should be expected to work ideally for the battery.

Most people don't worry about their car battery charging system to this extent, but they also don't have to stop their recreational activity when the car battery charge runs out, and rarely need any significant fraction of the car battery's capacity.

Is any solution actually desired here, or is it just a rant? I'm okay with a rant, I just don't want to waste my time contributing to an unwanted solution.

Check out ohm's law.
If that don't work for you check out Kerchief's current law.
Then try to determine the impedance of the battery undercharge and if it changes.

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Old 10-01-2013, 08:57 PM   #36
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Brian, I expected various folks to have examined this and care, perhaps to have found something they used. Not happening, so I would say don't waste your time.

I am looking for a single package which will take ac or solar dc and provide smart charge from either, and automatically switch if the ac goes away. I have found solar smart chargers, I have not found that combination.

Only one other person in this thread expressed anything other than 'how silly of me to care'.
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Old 10-01-2013, 09:51 PM   #37
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Check out the Battery Tender website. They carry 4 stage chargers to deal with Golf Cart batteries and they charge at the voltages that are specified for your batteries. Lots of good info on this site.
Eddie
Battery Basics - Batterytender.com
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Old 10-01-2013, 10:21 PM   #38
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Eddie, good web site.

Thanks.
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Old 10-01-2013, 11:47 PM   #39
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Check out ohm's law.
I'm familiar with that. The battery is not just a resistor.

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Originally Posted by Byron Kinnaman View Post
Then try to determine the impedance of the battery undercharge and if it changes.
As the battery charges, the internal voltage rises, so less current flows for the same applied voltage.

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Originally Posted by Byron Kinnaman View Post
If that don't work for you check out Kerchief's current law.
Check out the basis on which multi-stage chargers determine the point to switch charging stages, and consider the consequences for the ones based on current measurement of the measured charge current (out of the charger) not being the actual charge current (into the battery)... because Kirchhoff's current law says that if current is coming from two different chargers, the current into the battery is the sum of them... not just the output of one charger.

To be fair, any charger that is measuring only its own output current is doomed to be incorrect (in the opposite direction to the multiple-source case) when other loads are taking some of the current instead of the battery (Kirchhoff again)... and that's the normal RV converter/charger scenario.

A charger which responds only to voltage won't have a problem with either case; although that's not going to be ideal charging, maybe it's good enough.
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Old 10-01-2013, 11:56 PM   #40
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From that site:
Quote:
The transition from absorption charge mode to the next stage is determined either by a timer, or by the charger sensing the value of charge current and then switching over when the charge current drops below a certain threshold
This is an example of stage transition based on monitored charging current, as I mentioned earlier.
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Old 10-02-2013, 12:31 AM   #41
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I'm familiar with that. The battery is not just a resistor.


As the battery charges, the internal voltage rises, so less current flows for the same applied voltage.


Check out the basis on which multi-stage chargers determine the point to switch charging stages, and consider the consequences for the ones based on current measurement of the measured charge current (out of the charger) not being the actual charge current (into the battery)... because Kirchhoff's current law says that if current is coming from two different chargers, the current into the battery is the sum of them... not just the output of one charger.

To be fair, any charger that is measuring only its own output current is doomed to be incorrect (in the opposite direction to the multiple-source case) when other loads are taking some of the current instead of the battery (Kirchhoff again)... and that's the normal RV converter/charger scenario.

A charger which responds only to voltage won't have a problem with either case; although that's not going to be ideal charging, maybe it's good enough.

BASIC ELECTRONICS --- A battery is a considered a load to a DC supply. There are only 3 types of loads, resistive, capacitive, and inductive. In DC there's only resistive.
A battery charging is simply a DC supply.
If you really understand it things can be broken down to some pretty simple concepts. Those that don't try to impress you with their foot work.
That's what happens when everything that's read on internet is believed.

Therefore to look at multiple charging sources is to look at multiple power sources tied to same load (resister or battery). Then look at the smarts, or sensing. The smarts can look at is current, or shut off the output and look at the voltage. When the battery gets close to being fully charged one of the smarts will shut off that source and leave the other until the battery gets a bit charge.

Granted that the charging profile might be a bit different with two charging source vs one, but it's going to be different between the two charging source if used individually along with a different profile when charged from the tow vehicle. Add to that many solar charges are PWM (Pulse Width Modulation).


If I connect a battery via jumper cables to my truck I can get a 74 amp hour battery from dead to fully charged (as high as will charge) in about 15 minutes. Connect that same dead battery to my smart 10 amp charger it'll take 10 to 15 hours. Connect it to my solar charger at 4+ amps it'll take about 8 hours with direct sun. All different. If I connected all three at once the truck would still have the battery charged in 15 minutes.

The fastest profile wins.
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Old 10-02-2013, 11:16 AM   #42
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Interesting thread. Although I'm new to this site and to deep cycle marine batteries, I've used Battery Tenders for years on my motorcycles. My experience has been that I get about 10 years' use from a wet cell battery on an electric-start Harley when it's plugged in to a Battery Tender through our longish Northern Wisconsin winters.
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