Question for the battery experts?

[scanzel]

I purchased a Magnum 4024 inverter/charger and would like to now connect the batteries to bring them up to full charge. I have 8, 100 AH at the 20 hr rate AGM batteries that are new and I got for free. I am going to use these until I get the new Lifeline batteries next year. I have a 100 amp Vanner equalizer that I would connect to run the 12 volt items, Proheat unit, water pump, sewage macerator. The interior lights would probably be 24 volts. My 120 volt items will be a standard home refrigerator, microwave. MY QUESTION IS, what is the best way to connect the batteries together, series then parallel, parallel then series, still a little confused here. Also where is the best point along the way to tap in the Vanner. I don't want to destroy anything. Right now I just want to charge the batteries using the inverter/charger.The other items above will be added to the system latter as the conversion moves forward.   Thanks. Steve C.

[Nick Badame Refrig/ACC]

Hi Steve,

It depends on your set up and what you want to achive. The 50 amp stud on your Vanner may have you limited

in the sence that you may have to be carefull of what you turn on together.

Here is a link to electrical thread that I set-up.
http://www.busconversions.com/bbs/index.php?topic=5097.0

Nick-

[Stan]

If you exceed the rated capacity of your Vanner's 12 volt output, it just draws the extra load from the 12 volt battery and replaces it when the excess load is removed. Short term overloads do no harm to the system.

Lots of information available in the owner's manual at http://www.vanner.com/pdf/man-0001.pdf

[Len Silva]

I hadn't thought about this before but here is a consideration.  The drawings were lifted from Nick's article.  If the Vanner and load are connected as shown in the first sketch then it seems to me that only one set of batteries would be doing the work. Do you think there is any problem or advantage with connecting all the 12V taps together as in the second sketch?

Len

[Len Silva]

No, forget it.  After looking again, I don't think it would make any difference at all.

Len

[Nick Badame Refrig/ACC]

If you exceed the rated capacity of your Vanner's 12 volt output, it just draws the extra load from the 12 volt battery and replaces it when the excess load is removed. Short term overloads do no harm to the system.

Lots of information available in the owner's manual at http://www.vanner.com/pdf/man-0001.pdf

Hi Stan,

There is a 50A curcuit breaker on my 12v tap of my vanner. It may trip at 65-70 amps if it's in good shape.
If not, he may be faced with bypassing the breaker and installing a higher amp substitute.
Nick-

[Chris 85 RTS]

Actually Len there is a difference.  The Vanner will have no effect on the 4 bottom batteries.  It will not help them to stay balanced.

Read the vanner pdf file, look at off-grid websites.  To just keep the series batteries balanced, you could use a smaller lower cost equalizer.  You can also use the vanner to supply the 12V directly, and not connect it's 12v post to the center tap of the batteries, and use lower cost equalizers.  There are alot of options here.  You will need to do some research and study the options for what you want to achieve. 

[Sean]

If you are using the bank to power both 24- and 12-volt loads, you want to connect a "lower half bank" of four batteries in parallel, then an "upper half bank" of four batteries in parallel, then connect those two halves together in series.

Your 12-volt tap goes to the serial connection point, as well as does the 12-volt post on the equalizer.

If you do this the other way 'round -- a parallel bank of four series pairs of batteries, then all your 12 volt loads will have to run from a single battery, thus ensuring you will have differential usage on that battery (actually, both batteries in that string, even with an equalizer).

Remember when making the two half-banks that you make final connections to the negative post at one end of the parallel group, and the positive post at the other end -- this evens out the current among all batteries in the group.  For the intra-group cabling, try to use cables of uniform length, for the same reason.

-Sean
http://ourodyssey.blogspot.com

[Stan]

Nick: You are not pulling the 12 volt current from the Vanner. You are pulling it from the 12 volt tap on the battery bank and the Vanner is replacing one half of what you use from the 24 volt half of the battery bank. If you draw more than the rated current of the Vanner, it is just not able to keep up with the balancing. For example on your unit, if you draw 60 amps on the 12 volt system, you will be pulling 25 amps from the 24 volt battery and 35 amps from the 12 volt battery. When you drop the load down to 40 amps, you will be drawing 25 amps from the 24 volt battery and 15 amps from the 12 volt battery until the batteries are back in balance.

This is rather simplistic, because the switching takes place in milliseconds in two banks of transistors, but the end result is as I explained it.

This is the big difference between an equalizer and a DC to DC converter which only has a 24 volt input and has to electronically generate the 12 volts. On that system, you cannot exceed the device rating.

[Nick Badame Refrig/ACC]

Hi Stan,

Thanks for clearing that up. Then that breaker can fool most if they don't understand the ballance of the vanner.

Nick-