Will I have problems pulling 12 volts off just one of two battery strings?

[belfert]

My plan for house batteries is to have two parallel strings of four 6 volt batteries for a total of eight 6 volt batteries in two parallel strings.  The main voltage will be 24 volt.

I have a Vanner Equalizer for 12 volt power.  Since a Vanner is just a center tap of a 24 volt battery bank, wouldn't this mean one string would get more usage than the other?  I would think charging the parallel strings would be a problem if the usage is not equal.

Is there a way around this to still use the Vanner and 6 volt batteries?  I really don't want to spend twice as much on four 12 volt batteries.

Brian Elfert

[JackConrad]

Brian,
    My understanding is that the Vanner equalizer draws from both batteries to keep them equal, hence the name "equalizer".  Just make sure you do not exceed the rated capacity of the equalizer.  Maybe somone with more electrical knowledge will join in. Another option would be a DC to DC converter which reduces 24 volts to 12 volts. Hope this helps,  Jack

[belfert]

Brian,
    My understanding is that the Vanner equalizer draws from both batteries to keep them equal, hence the name "equalizer".  Just make sure you do not exceed the rated capacity of the equalizer.  Maybe somone with more electrical knowledge will join in. Another option would be a DC to DC converter which reduces 24 volts to 12 volts. Hope this helps,  Jack

The manufacturers I talked to recommended the equalizer over a convert for RV use.

My problem is I have two parallel strings of batteries charged by the same charger.  I figure I can only put the equalizer on one string of batteries so the charge state won't be the same.

Brian Elfert

[jjrbus]

 I've had a 60amp Vanner equilizer running the 12 volt in my bus for 5 years with no problems.
                                                                                                  HTH Jim

[NJT5047]

You'll have to divide the battery bank into  two 12V groups.  You'll have a combo of parallel and series.  That would work fine.  Still have the same total amps potential.  Then install the Vanner between the appropriate 12V and 24V terminals.  It will keep the batteries equalized.   A 60 amp Vanner will keep the batteries equal for practically any RV load...short of a hooking up a 12V inverter and trying to run an AC.  Use a 24VDC inverter to remove some of your RV 12V loads such as some lighting.  Any major power requirements should be on the inverter...big entertainment systems, AC (OTR only).   Using banks of high quality 12V batteries would be easier to hook up. 
All the Vanner will do is assure that both batteries discharge and charge together.   The Vanner isn't a
"center tap"...it just keeps the batteris equal.   It'll pull from the "upper" battery whenever there is a small difference in voltage between the batteries.   
I've been using the original 8ds and a Vanner for several years without any problems.  Runs all of the usual RV stuff, fridge, hot water ignitor, pump, monitors, radio, and lighting.
JR 

[belfert]

24 volt inverter is what I am using.  The battery bank would be 12 volt only if I had a 12 volt inverter.  My Vanner is 80 amp only because I got it cheap.

I realized after I posted that I might be able to make two strings of 12 volt and join them so the Vanner will draw from both.

Brian Elfert

[NJT5047]

At the risk of prattling too much, if you are using a Vanner, there is a particular method of disconnecting the units.  Someone may know, but check the manual or material printed on the unit.  I believe the ground is disconnected first.  It's printed on mine  but I forget. Wouldn't want t damage a good Vanner,  these things are typically expensive. 
Your 24V inverter is a good choice on 24V coaches.  Only way to fly! 
JR

[NewbeeMC9]

At the risk of prattling too much, if you are using a Vanner, there is a particular method of disconnecting the units.  Someone may know, but check the manual or material printed on the unit.  I believe the ground is disconnected first.  It's printed on mine  but I forget. Wouldn't want t damage a good Vanner,  these things are typically expensive.  ...
JR

JR, Could you look that up and post it? 
I have a 100amp equalizer and I used 100amp DC breakers/ disconnects on the 12 & 24 volt lines and the ground hrd wired in.  I'm pretty sure that was the way it was to do it correct and it took me a little wotk to find the breakers.  To turn it off I just open the breakers.  and then shut to turn it on.

[NJT5047]

Yep.  I'll get it off the Vanner tomorrow.  I'll post what it says.   Removing either the 12V or 24V leads may appear to be a dead battery and the Vanner may toast itself trying to charge an open circuit.  I'll check on the correct proceedure.   
Remember to disconnect ALL of the DDEC and Vanner if you weld on a bus chassis too.  Some welders will screw all over our electronics.  I'll leave that explanation to those that understand welding.   My coach has warning lables in the battery compartment regarding welding on the coach.   My DDEC is twelve volts, so the center tap still has potential  even when the ground is removed...or something like that!   
JR

[NJT5047]

OK.  The correct order for removing the Vanner leads are to disconnect the ground wire first, and reconnect the ground last.   They also caution against connecting more than one lead to any Vanner post.  Connect to the battery terminals, and not the Vanner terminals,  if you need 12V or another 24V tap. 
Check this website for specifics:     

http://www.vanner.com/pdf/man-0001.pdf#search='vanner%20equalizer'

Hope this helps.   JR

Fixed the link. Richard

[belfert]

The Vanner that came with my coach to run the lights and such has three connections to grouond for some reason.

Always remember to disconnect the ground on your Vanner if you do any welding.  In my case, I also have to remove the fuses for the DDEC and WTEC when welding.

Brian Elfert

[belfert]

Opps, didn't notice somebody already posted the warning about welding.

As far as the original question, I think I can create four 12 volt strings and hook them together at the center for the center tap.

Brian Elfert