Charger installation

[Rawlclan]

Hello RV Forum.  I've been RVing for quite a while and am on my third motorhome, a 32 foot 2001 Itasca Suncruiser on a Ford V10 chassis. Right now I am preparing to install a Xantrex Truecharge 40 charger. I'm looking for information as to how to install it. Initially I was going to use it with my converter, and had been told that I should disconnect the charging wire from the converter to the batteries. Now I have heard that I should use the Xantrex charger in place of the converter. Also by examining a wiring diagram of my coach I have been unable to find any circuit dedicated to charging the batteries. Two cables go from the converter to the 12 volt fuse panel.  I guess the batteries get charged by using the the same circuitry that takes power from the batteries.

The installation instructions that come with the charger are good as far as charging goes, but it says nothing about using one of the tree charging banks to power the 12 volt system.  I assume I just run a cable from the charger to the fuse panel.  Is that all there is to it? I'm worried that if I do that it Willl burn up my electrical system as soon as I plug in to shore power, or turn on my generator.

Any information on this topic wil be greatly appreciated.

Rawlclan

 

[Carl L]

Hello Rawlclan and welcome to RVForum.  I have taken the liberty of moving your message and question to the Tech Talk section.  This is were our assorted gurus on electronics tend to gather and should provide you with a better response.

 

[Kirk]

The proper way to connect your new equipment will depend upon just what you have. And the key to doing it properly is to follow the directions. There is no advantage to keeping the old converter and adding a new one. But most standard equipment converters do not have a separate charging circuit. What they usually do is to have one output from the converter that ties to the same points as does the battery. In other words, the positive side of the converter, the batteries and of the electrical system all connect together. The converter is normally adjusted to put out about 13.5V and that supplies the 12V-dc loads as well as keeping the batteries pretty well charged. But it takes more than 14V to fully charge a battery, while your 12V powered equipment is only designed to operate on a DC voltage that ranges from about 10V to 14V, maximum. So if the converter were to be set to fully charge the batteries, it would also damage the electronics of the RV. Additionally, a battery that has been fully charged needs to have the charge voltage lowered once it is fully charged to prevent the boiling of the electrolyte. Ideally, that voltage is then lowered to once the battery is charged. The low end converters do not have enough voltage regulation to perform that function so they are set to a voltage that keeps the batteries near fully charged, while not boiling out the electrolyte.

The best converters, usually called a converter/charger, have a separate circuit that charges the batteries and one to supply the 12V-dc loads. The load circuit maintains a steady voltage around 13V, while the charging circuit has the ability to monitor the battery condition and it will increase the voltage to around 14.4V as the battery reaches full charge, and then drop it back down to a maintenance lever about a volt or so lower at that point. That type of converter also has a transfer relay inside of it that shifts the 12V circuits from the battery to the load side of the converter, when 120V-ac power is available and the battery is being charged. Once the 120V-ac is not available, the loads are shifted back to the battery and the converter is not in the circuit, except for the transfer relay circuit. Most RV inverters also have that capability built into them.

If your new Xantrex has both a charge circuit and a load circuit, then it should have instructions for where the loads should be connected and where the battery should be connected. But you will have to modify the RV's wiring to allow for this if your present converter is not that type.

 

[Rawlclan]

Thanks Kirk. I'm pretty sure my converter is the type thathas no direct  charge line to the batteries. Like you said, the batteries are charged via being on the same circuits as the converter. I have read that the Xantrex Truecharge 40 is commonly used to replace converters. It has three separate charging banks with three stage charging on all three banks.  What I was led to believe is that  I could use one bank to charge the batteries, another would be wired directly to the 12 volt fuse panel, and the third would not be used.  I was looking for somebody who had done this before who could confirm that I would be doing it correctly.  I don't understand how the power from the charge circuit would be any different that the power to a load circuit.

 

[John From Detroit]

  I don't understand how the power from the charge circuit would be any different that the power to a load circuit.

Two differences ....

1: power to the load circuit is ALWAYS 13.6 (or some other arbutary voltage very close to 13-14 volts)
  Power to the charge varies depending on where in the charge cycle you are

2: Xantrex products you program in current limits.  If the batteries are supposed to be fed at say, 75, amps, and the charger is thus outputting 75 amps, and the load in the MH is 25 amps, then .. (Single circuit) there is but 50 amps for charging (unless there are some very tricky sensors in the line,,, not normally done)

But if you have seperate "load" and "Charge" lines... Then the converter powers the load, (25 amps) and the full 75 amps (In this example) feeds the batteries.  Means faster re-charging.

 

[Karl]

Rawclan,

That charger is designed specifically to charge 3 seperate banks of batteries or 3 individual batteries. It is not designed to function as a power supply to external circuits like your coach lights, etc., and would not work properly in that mode. Go here to download detailed info (including wiring diagrams).
http://www.xantrex.com/web/id/69/p/docs/pt/24/product.asp

 

[Gary RV_Wizard]

Your TruCharge can operate in a 13.5 VDC Fixed Output mode that is appropriate for use as a house power supply. However, that mode is a poor chice for battery charging because it will overcharge the batteries after awhile. Unfortunately, you cannot select Fixed mode for one bank and Charging mode for another, so Charging mode is therefore your only choice.  That's not really much different than how most converter/chargers work anyway. The battery acts as sort of a buffer for the house wiring.

I would not use a separate bank for direct connection to the house system. There is really no advantage to that because (according to the TruCharge manual available online) the banks are not separately regulated anyway.    All the separate banks do is isolate one set of batteries from another, i.e. prevent one battery from trying to charge the other by supplying current to it.  My choice would be to wire the TruCharge output direct to the battery terminals, but if necessary you can connect it as your present converter/charger is wired, i.e. to the 12V distribution panel.  Just make sure the wiring from the panel to the batteries is large enough to handle the TruCharge's 40A max output.

Do NOT activate the Equalize mode while the house wiring is connected. Equalizing produces greater than normal operating voltage and could possibly damage or shorten the life of 12V appliances.


I would have recommended one of the RV converter/chargers by Progressive Dynamics or Iota over the TruCharge. With the Smart Charge feature they offer 3-stage charging and are designed for RV use. Excellent products, both of them. See http://www.progressivedyn.com/power_converters.html  or http://www.iotaengineering.com/12vdc.htm

 

[Karl]

Gary,

Not disputing anything you said, but this system seems to have been designed for multiple vehicles which sit for long lengths of time between use. They specifically state Emergency Vehicles and also mention RV's. I think that 21-day automatic charge feature is the giveaway. While true that the output voltage is common to all 3 + leads, there seems to be some kind of charge level sensing that regulates the current to each leg.
Quote from the manual:

Simultaneous Three-Battery Bank Charging
Truecharge+ has three separate DC positive terminals to allow charging of three separate batteries (or battery banks). The total current into the
batteries is a maximum of either 20 amperes or 40 amperes, depending on the model, which is divided amongst the batteries according to their state
of discharge.
Note: The three outputs are not independently voltage regulated so it
is important to avoid systems with mixed types of batteries.

Also totally agree that there are other units available that are a much better choice. The wiring of this unit could be a nightmare, what with all kinds of back-circuits to contend with.

 

[Bob Buchanan]

Hello Rawlclan:

>>  I assume I just run a cable from the charger to the fuse panel.  Is that all there is to it? I'm worried that if I do that it Willl burn up my electrical system as soon as I plug in to shore power, or turn on my generator.
====
In 1995 I purchased that charger (Statpower then) -- along with a 1500W inverter (separate units). I installed both it in my then '94 Brave. After chatting with the repair manager at CW, I plugged the charger into an AC outlet -- and ran adequate sized cables to the battery bank. I did not run any wires to the converter.

Since then I have had a travel trailer, a 5th wheel, and now a Tioga MH -- and have wired that charger exactly the same way in each with no problems. My Tioga has a pretty good charger already whereas the other rigs came with just a trickle charger in the converter. Most of the time I just unhook the rig charger via the circuit breaker that supports it.

When the batteries get low while dry camping, I turn on the genset that gives AC to the outlet that I plug the charger into. If on inverter power, I unplug the charger.

 

[Rawlclan]

Thanks everyone. Based on the input I think I'll just leave my converter as is, and hook up the Xantrex as a charger only when I'm dry camping and need to charge the batteries.