Please help me understand my RV electric

Interesting. I will likely charge each 6V individually assuming I have the time.

What you have is one big 12 volt battery. Treat it as such. If you want to charge differently, you have to have disconnects in place. As long as the connections are there, it is one battery.

After the charger indicated the bank was full, charging at 12V, I have only topped off 2/4 6V batteries which each took about 12 hours to do so. Very, very interesting. Here is the 3rd battery, also interesting that despite all the batteries being connected, each individually still reads 6V.

OMG then started reading this page, now I'm totally confused...

http://www.batterytender.com/Connecting-Chargers/

FOUR BATTERIES IN SERIES / PARALLEL (EXAMPLE 1), ONE CHARGER

The diagram shown in Figure 11 is an acceptable way to charge a combination series / parallel battery pack. This method is definitely better than the arrangement shown in Figure 10 (there is no Figure 10) because the imbalance in individual battery voltages is not as much of a concern. There are some intricate details of charging algorithms that are specifically optimized to account for and eliminate the individual battery voltage imbalance in large series strings. Even without those special charging features, the single 24-volt charger in this arrangement does a better job than two 12-volt chargers would. Again, the blue wire designated W1 serves the same charge voltage drop imbalance function that it did in Figure 9.

Figure 12 again shows two 12 volt chargers connected to a series / parallel battery pack. But this battery pack is configured like example 2 in the previous section. What you have is two sets of two batteries each connected in parallel. Then those two parallel-connected sets of batteries are connected in series by a single wire connection. In this case, it is perfectly acceptable to use a single charger for each of the parallel-connected sets of batteries without worrying about the voltage imbalance discussed with respect to example 1. Recall that example 1 shown in Figure 4 had two sets of two batteries, first connected in series, then each series connected in parallel by 2 wire connections.

For those mathematics buffs that are into topology and n-dimensional spaces, etc., one might consider the fact that there is one more piece of wire connecting the batteries in example 2 (5 pieces of wire total) compared to only 4 pieces of wire in example 1. That one extra connection makes the difference between being able to use two 12-volt chargers effectively instead of having to use one 24-volt charger. In some larger systems, these types of considerations could have an impact on both economics and system reliability.

FOUR BATTERIES IN SERIES / PARALLEL (EXAMPLE 2), ONE CHARGER

Just one more comment about voltage imbalance while charging current is being applied. Figure 13 shows two wires highlighted, the blue one designated W1 and the green one designated W2. Interestingly enough, if the connection at battery D positive terminal is moved to battery C positive terminal, without changing the connection at battery A negative terminal, then a voltage imbalance will exist. Do a thought experiment. Take a pencil and trace the path of the charge current from the output, positive terminal of the 24 volt charger, through the wires, and the batteries, through W1 and back to the output, negative terminal of the 24 volt charger.

Now go back to Figure 12 and look at the green wire designated W3. With 2 independent chargers connected, the blue wires W1 & W2 correct the voltage imbalance that would exist in the individual, parallel connected battery packs. The green wire W3 does absolutely nothing in terms of charging the batteries. In fact, it can simply be removed because NO CURRENT flows through it while the two groups of batteries are being charged.

Those instructions are for using all 12 volt batteries, so series/parallel makes 24 volts. You have 4 x 6 volts, each 2 connected in series to get 12 volts., and then connected parallel to give you 12 volts with 2 times the amps.
When all is connected you will get the same reading on all batteries, 6+ volts individually, and 12+ volts measured as a pair or group (main posts + and -). Main posts are the ones that lead into the main trailer wiring. These posts will be used for charging from your converter and should be used when using an external charger.
A "battery tender" is a maintainer, not great as a charger. Do you have a good 3/4 stage converter? If so, plug the trailer in and let it work. If not, replace with new.

byrogie said:

Those instructions are for using all 12 volt batteries, so series/parallel makes 24 volts. You have 4 x 6 volts, each 2 connected in series to get 12 volts., and then connected parallel to give you 12 volts with 2 times the amps.
When all is connected you will get the same reading on all batteries, 6+ volts individually, and 12+ volts measured as a pair or group (main posts + and -). Main posts are the ones that lead into the main trailer wiring. These posts will be used for charging from your converter and should be used when using an external charger.
A "battery tender" is a maintainer, not great as a charger. Do you have a good 3/4 stage converter? If so, plug the trailer in and let it work. If not, replace with new.

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I agree, I think you are over thinking this. Forget about the battery tender, and if your trailer doesn't already have a good converter, upgrade it to a 9270 or a 9280 and be done. Why worry about charging the batteries one at a time? Put a smart charger on it and be done.

I have a Schumacher XC10 microprocessor controlled 3-stage charger. The converter/charger model in the coach is pictured in the first post in this thread. I believe it is a newer charger but I have no idea how it functions (single stage, 3-stage, etc). So for now I am charging with the XC10. I just want the batteries to be fully charged and I'm interested/curious/concerned as to why when the "bank" is fully charged, each individual battery has taken an additional charge for about 12 hours each. Maybe its not an issue, maybe it is. I only linked the Battery Tender site as it seemed to be the most knowledgeable regarding the use of a charger on a battery bank. I would assume the same concepts apply to 6V batteries as they do 12V batteries for this purpose.

supermanotorious said:

I have a Schumacher XC10 microprocessor controlled 3-stage charger. The converter/charger model in the coach is pictured in the first post in this thread. I believe it is a newer charger but I have no idea how it functions (single stage, 3-stage, etc). So for now I am charging with the XC10. I just want the batteries to be fully charged and I'm interested/curious/concerned as to why when the "bank" is fully charged, each individual battery has taken an additional charge for about 12 hours each. Maybe its not an issue, maybe it is. I only linked the Battery Tender site as it seemed to be the most knowledgeable regarding the use of a charger on a battery bank. I would assume the same concepts apply to 6V batteries as they do 12V batteries for this purpose.

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That 7300 is the same panel that is in my coach, don't believe it is a smart converter at all.  If you have your coach plugged in when you hook up you XC10, it will think your battery bank is fully charged. I've been working on my power problems a bit too, and I haven't seen my 7300 go into a float charge yet. I'm going to upgrade my converter to one of these.

http://www.bestconverter.com/PD4655-55-Amp-Converter-Upgrade-Section_p_352.html#.VuBVSPkrK00

But I don't know if it would be large enough amp wise for your battery bank.  I think the 55 amp is the largest they make in a retrofit kit. 

Your schumacher is only 10 amps, will take a long time to charge your bank. You need more power!
You can do an upgrade to your converter, or get a stand alone converter as a charger. Others on this forum have similar setups and can comment on how much power you need.
I would guess at least 55 amp... Make sure it is 3/4 stage, and a reputable brand conducive to your situation.
Just because the Schumacher says fully charged, doesn't necessarily mean it is. Check with SG, specific gravity.
I say again, look/treat as ONE battery, for use and charging.

Thank you for the suggestions. I knew the converter output could fool the XC10 so I disconnected the converter using the push/pull switch in the coach for charging off the XC10. My budget is absolutely tapped at this point so I will look at higher amperage chargers when I have more scratch. For now, I will likely disconnect and individually charge the batteries using the XC10 and starting several days before any trip.

supermanotorious said:

Thank you for the suggestions. I knew the converter output could fool the XC10 so I disconnected the converter using the push/pull switch in the coach for charging off the XC10. My budget is absolutely tapped at this point so I will look at higher amperage chargers when I have more scratch. For now, I will likely disconnect and individually charge the batteries using the XC10 and starting several days before any trip.

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Why not just leave the XC10 connected to the full bank all the time ? If it's a smart charger it will very the voltage to maintain your bank, it will just take longer.

92GA said:

Why not just leave the XC10 connected to the full bank all the time ? If it's a smart charger it will very the voltage to maintain you bank, it will just take longer.

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Yes but charge a series pair of 6V as a single 12V. The way for pic of yours shows it will work but it will be uneven between the batteries. The positive charger input will be going against the natural flow of the current flow for one of the batteries. The current flows out the last positive post to power your RV and returns to the negative post of the the other. So the current flows from the first battery to the second battery. This is inefficient and could cause problems, maybe fire.

Bill

Could you please explain how else they could be wired? They are wired in series then parallel.

We're on our third morning in Yosemite and the battery bank is doing great. We're shutting off the inverter whenever not using the outlets. I've been running the generator for a couple hours a day, the Schumacher and the converter are working together.

byrogie said:

Your schumacher is only 10 amps, will take a long time to charge your bank. You need more power!
You can do an upgrade to your converter, or get a stand alone converter as a charger. Others on this forum have similar setups and can comment on how much power you need.
I would guess at least 55 amp... Make sure it is 3/4 stage, and a reputable brand conducive to your situation.
Just because the Schumacher says fully charged, doesn't necessarily mean it is. Check with SG, specific gravity.
I say again, look/treat as ONE battery, for use and charging.

Click to expand...

Our new hauler has a 55amp 3-Stage WFCO converter, is this similar to what you're referring to? I want to do this inverter project again and am curious if the charger/converter is enough for the 4-6 6V batteries.

I leave the trailer plugged in to a 30 amp service while on our driveway. We were headed to Payson Friday and I put my XC10 charger on the 2 tongue batteries, they took a better part of the day to top off. Why isn't the 3-stage converter keeping them topped off?

Your converter has a 13.6 volt max output. The XC 10 may have a higher charge voltage, so it will continue to charge until it reaches it's "charged" voltage.

ah, good point, thank you! I think the xc10 goes upwards of 15V