Vanner equilizer question..

[travelingfools]

Is the 12 volt post on the equalizer the same amperage as the 24v side ?

[Sean]

No.  The amperage on the 12v post will be double whatever it is on the 24v post.

-Sean
http://OurOdyssey.BlogSpot.com

[norules]

shouldn't the answer be:

whatever the lower 12 volt batteries are capable of suppling - with the note that the Vanner circuit breaker will OPEN (stop equalizing voltages) when the amp draw from the UPPER 12 volt batteries to "EQUALIZE THE LOWER BATTERY VOLTAGE" exceededs the Vanner Model maxium AMP RATING. (example Vanner 60-50A = max amps 50)

[Sean]

shouldn't the answer be:

whatever the lower 12 volt batteries are capable of suppling ...

No, it should not.

The question was the amperage at the post, and the answer is that it is twice the amperage at the 24v post UP TO the operating limit of the equalizer.  The supply capability of the batteries is irrelevant -- you won't measure that amount of current at the 12v equalizer post.

Note that the internal circuit breaker on the unit is not sufficient and is for a different purpose.  Vanner documentation mandates external fuses at both the 24v and 12v connections between the equalizer and any loads, batteries, or charge source.

-Sean
http://OurOdyssey.BlogSpot.com

[norules]

I'm very confused - please explain ??

how can the AMPS available at the 12 volt post (which is tied to the Vanner 12 volt post) be 2x the AMPS available at the 24 volt post

?

[JackConrad]

watts equals volts times amps.    480 watts divided by 12 volts equals 40 amps. 480 watts divided by 24 volts equals 20 amps.  Jack

[bevans6]

How I think of it, which may well be wrong, is that the Vanner is a little power supply designed to take in 24 volt power and put out 12 volt power to help equalize the load on the 12 volt battery.  Here is my scenario:  you have two identical batteries in a 24 volt system, and there is only a 24 volt load.  The load is equally distributed between the two batteries, and the Vanner is doing nothing.  Now you add a 10 amp draw from the lower 12 volt battery to run a 12 volt load somewhere.  Now the load is no longer equally distributed, the top battery has 10 amps less load than the bottom battery.  Now the equalizer has something to do - it pulls in power at the 24 volt terminal and puts it out at the 12 volt terminal to make the load on both batteries the same.  If the batteries are getting charged at the time, it makes sure that each battery is getting the same amount of charge.  Assuming 100% efficiency, and a Vanner is very close to that, the power coming in at 24 volts will be at half the current as the power going out at 12 volts, since power is volts times amps.

Brian

[Sean]

how can the AMPS available at the 12 volt post (which is tied to the Vanner 12 volt post) ...

OK, now you have me confused.  When you say "12 volt post tied to the Vanner 12 volt post,"  I am guessing you must be talking about the 12 volt battery post.  The OP was asking about amperage at the Vanner post.  These are two different places.

There should only ever be one wire attached to any Vanner post; they can not be used as junction points.  That's because the very first thing that needs to be at each of the two hot posts is an in-line fuse.  ALL connections to each post must be made on the other side of the fuse.  A model 60-50 Vanner requires an 80-amp fuse on the 12-v side, and a 35-amp fuse on the 24-v side.

With only one wire attached to each Vanner post, the current on each wire (and fuse) is easily established by the power relationship that Jack described.  For any given power level, the product of voltage and current on each post must be the same, thus halving the voltage will double the current.  So as I wrote initially, the amperage on the 12 volt post will be twice what it is on the 24 volt post; no more, no less (well, OK, the Vanner itself uses a tiny bit of power, so the output current will always be a tiny bit less than twice the input).

The amount of current flowing to or from the batteries at the 12-volt center post is a different matter altogether.  There will be one point where the 12-v feed from the Vanner, the 12-v output to the loads, and the center tap of the batteries all come together (sometimes that is actually at one of the battery posts), and figuring the current flows there is a fairly complex matter involving the amount of load, the SOC of the batteries, and even the battery imbalance at the time of measurement.

Does that clear things up?

-Sean
http://OurOdyssey.BlogSpot.com

[buswarrior]

For a goof like me...

You still get your 12 volts by centre tapping a 24 volt battery set, Equalizer is irrelevant.

Your only expectation for the Equalizer should be to hide in there and moderate the abuse that would otherwise be happening with a centre tap - imbalance to the 24v set by draining down 1/2 of it and the associated imbalance when trying to charge it back up.

Don't go expecting it to do anything else and everything will be fine.

Size the Equalizer to exceed whatever 12 volt loads you are stealing from the centre, job is done?

happy coaching!
buswarrior

[edroelle]

You really do not need to size your equalizer to be larger than all loads, all the time.  You can pull charge from your "low" battery, and later, over time, your Vanner will equalize the "low" with the "upper" battery.    At night while sleeping, your Vanner could "catch-up".

Ed Roelle
Flint, MI

[Sean]

I'm with Ed on this one.  The equalizer only needs to be slightly larger than the time average of all the 12-volt loads, not the maximum total instantaneous load.  Most bus nuts could get by with a 20-amp equalizer.

-Sean
http://OurOdyssey.BlogSpot.com

[buswarrior]

I'm concerned that there are busnuts that think an equalizer does miraculous things that it doesn't.

We get 12 volts via a centre tap.

The equalizer keeps us from wrecking batteries by doing so.

Ditto, Sean, who is going to be using as much 12 volt out of a 24 volt system as a transit bus, with all that fluorescent lighting as well as the exterior lighting?

Cheapest solution?

Just fetch a good used take out from your local transit scrapper and be done with it?

happy coaching!
buswarrior

[travelingfools]

Ok, now that Im totally confused...lol. I do understand what purpose the equalizer serves. I guess i should have got a little more specific in my original question. Im curious where that 12 volt pin on the equalizer could come into play with my 12 volt bank house batteries that feed my inverter. Will that 12 volt source be adequate to run the inverter (2500 watt) or will it be useful in charging my battery bank that feeds the inverter. My original plan was to install a 12 volt alternator to the engine to charge the bank. Any of the above options is for going down the road.

[buswarrior]

ok, tf is going to be using more 12 volt than a transit bus from his centre tap... !!

So, in other words, you want to try to charge/power the 12 volt house battery system by way of a centre tap on the coach 24 volt system?

The equalizer isn't the power source, the batteries are.

Some serious steady amperage draws involved here, you might consider doubling up the equalizer. The coach/transit manufacturers have done this in the past, put a pair of smaller ones instead of a big one.

Consider the effect on the high side coach battery if the equalizer fails... you will find out shortly afterward when it boils dry, won't pass current, the bottom battery goes dead, no gen light comes on the dashboard.

I'd be inclined to install the 12 volt alternator for loads this big, but I'm a chicken with no papers!

happy coaching!
buswarrior

[Sean]

... Im curious where that 12 volt pin on the equalizer could come into play with my 12 volt bank house batteries that feed my inverter. Will that 12 volt source be adequate to run the inverter (2500 watt) or will it be useful in charging my battery bank that feeds the inverter. ...

Not if you will also use it as an equalizer.

If this is an existing equalizer on the chassis side and is serving a center-tap on the chassis batteries to support 12v chassis loads, you MUST NOT connect additional 12-volt batteries to the 12-volt equalizer post.  This is direct from the Vanner manual.

However, if you have another equalizer that you want to install to feed your house bank, you can connect the 24-volt side to the engine alternator, and the 12-volt side directly to the house bank (NOT to the center tap of the chassis batteries).  The "equalizer" is now no longer equalizing, but instead acting as a voltage converter.  This is an approved connection method for Vanner equalizers and there is a diagram for it in the manual.

Connected this way, you will get up to the amperage rating of the equalizer for charging/running your 12-volt house system.  So a 60-50 model, rated at 50 amps, will provide 50 amps of 12-volt power (drawing about 25 amps from the alternator).

Note that if you have a large alternator, say a 50DN, the most you can use of it to supply your house system this way is less than 10%.  The largest equalizers on the market are only twice that large, or less than 20% of the capacity of a 50DN.  This is the reason I strongly recommend a 24-volt house system for coaches with 24-volt alternators.

If you've already got an investment in 12-volt house systems on a 24-volt coach, I suggest changing out the big 50DN engine alternator for a 12-volt model, using that to supply the house system, and putting a much smaller belt-drive 24-volt alternator in to power the chassis loads and charge the start batteries.

FWIW.

-Sean
http://OurOdyssey.BlogSpot.com