Xantrex 20 + and the 1-2-B Switch

[prh77]

I have 3 batteries connected to my Xantrex charger, 2 group 24 and a 27, all flooded cell. I will discharge them at different rates, and then recharge with the unit. What position should the boat battery switches be during charge? Can the Xantrex monitor each battery and adjust amps and voltage as required, or should the boat battery switches be set to "all ", so the charger views the batterys as one load?

[Ron Hill]

prf : Not too sure how you have your's wired in but the battery selector is for OUTPUT only:
If you have one of the three + charging leads from your Xanterx 20 to each of the 3 batteries - you don't have to worry which position the battery selector switch is in.  All 3 will even charge when the DC batt. sel. switch is OFF!!
Each battery will be charged at what THAT battery needs up to a TOTAL charging of 20 amps from the AC shore power. 

[mnewber]

Ron doesn't it matter on the routing of the charging wires?  My PO routed mine up to the battery switch so with that I assume that I need to have the battery selector in the ALL position to charge them?

It's on my list of upgrades but not sure when i'm going to get to it.   

[Stu Jackson]

It ALL depends on HOW it is wired, BUT even if the wires are routed to the 1-2-B switch, the switch can be OFF and the charger can still work IF the wires are fed to the 1 and 2 posts of the switch.  It will ONLY be off if the wires are fed to the Common (or C) post and the switch is turned off.

Wiring the charger output to the 1 and 2 posts of the switch is electrically like running them to the banks, it's simply just at the other end of the wire connecting the switch to the banks.  It will allow the charger to work even when the switch is off.

With the OEM #4 wiring between the banks and the switch, there's essentially negligible voltage drop for the 20 to 40 amp chargers most people have installed.  If you have a larger charger, do the research on wire sizing for a 3% voltage drop and either wire the charger directly to the banks, or change the wire size (between the banks and the switch).

Many boats came with the alternator output wired to the C post.  That's why people had to use the 1-2-B switch to select which bank got charged by the alternator.  The solution to that is to either (1) retain the 1-2-B switch but run the alternator output to the house bank and charge the reserve emergency (start) bank with another switch or a relay (echo charger, combiner, oil pressure relay, etc.), or (2) eliminate the 1-2-B switch as the basic boat switch (and move it over - or rewire it - to re-use as the emergency crossover switch) with single simple on-off switches for the house and start banks.

Please remember:  Many people get "confused" with the 1-2-B switch. There are only three points of wiring connection to the switch: 1, 2, and common (C). There are four POSITIONS to the switch, 1,2, B and off. However, OFF is NOT a wiring point of connection, it is a switch position.

[Ron Hill]

Guys : Look at the wiring instructions for the Xantrax chargers and you'll find the manufacturer recommends separate wiring from the charger output to each battery - NOT into the battery selector switch !!  They also recommend that each + lead be fused !!!

[jmnpe]

While the installation info that comes with the Truecharger+ series chargers does recommend fuses in the positive leads, this family of chargers already has internal fuses on each output: 30 amps on each output of the 20+, and 60 amps on each output of the 40+. I can vouch for the ability of the internal fuses to give up the ghost appropriately, but replacing them is a little messy and you have to know the "secret handshake" about how to successfully get the unit apart ( after you remove it from the mounting location... ). ( Please don't ask how I know so much about this subject  ..... ) The only time I have ever seen one of the fuses get blown is an accidental short of an output feed to ground or a reverse connection. The external fuse will be a lot easier to replace than the internal one.

John

[Mike Vaccaro]

Likely you'll have to do some sluething to see how your boat is wired.  If it's stock, the schematic in the manual is the best place to start.  Else, you'll have to shoot some wires. 

First a warning--if you're not familiar with electrical systems or wiring, the 115v AC system on your boat is somewhat intermingled with the 12v system in your control panel area.  The safetest way to ensure the AC system is "cold" is to disconnect the boat from shore power AND disconnect any inverters (if one is installed).  Some inverters will kick-in automatically if a load is detected and can deliver a lethal shock.  If in doubt, call a professional. 

The easiest way is to simply look at the color and size of the wires coming from the charger, and then look for a similar wire (likely red/yellow since it's a power wire) running to a battery positive terminal or one of the posts on the A/B switch.  As stated in the previous posts, running the charging wire to the A/B post is not appropriate, but it will work--the lead should be directly to the battery being charged.  If the leads are run directly to the battery, then it will charge regardless of A/B switch position (as it should).  You can use an ohm meter to check for continuity or a voltage checker to check for voltage if it's necessary to confirm how things are hooked up.

Cheers,

Mike