Two chargers on the same battey

[eamarquardt]

I dunno. In theory I can't see any reson for it not to work, but strange things sometimes happen. I wouldn't risk it.

Just a thought.

Cheers,

Gus

[wlooper89]

I had this concern too, as I have a three stage converter and also a Battery Tender connected. Both units have their own programs for recharging and battery maintenance, and I did not want them competing to charge the battery and sensing each other's voltage at the same time.

My solution was to install a 12V relay that would disconnect the Battery Tender output if the converter is powered. The relay is powered by converter 12V output. It may not be the easiest way to do it, but I enjoy soldering wires and making circuits that work, so it is part of my hobby. The result is what I wanted.

There is a switch to turn off the Battery Tender, so the forgoing is just in case I forget and leave both the converter and Battery Tender connected.

Bill

[eamarquardt]

I would have powered the relay with the 110 volt side of the converter. Seems like it would be more related to the converter being powered than on the 12 volt side. Depending on how the relay is wired it might possibly be powered/activated from some other 12 volt source (diodes could be used to solve this). But, if you wired it, it's working, who am I to argue with success. I like relays as they can be used to solve a lot of problems.

Good work.

Cheers,

Gus

[wlooper89]

Thank you Gus, you are exactly right. It would be hard to undo now, but I might have tied the relay to the 120V side of the converter. My battery goes through a switch to the the converter DC output terminals. From there D/C power from either source connects to the trailer by way of a D/C master switch and fuses. If the battery switch is on, charging from the Battery Tender is inhibited as though the converter was on. I have to remember to turn the battery switch off and turn converter/trailer A/C power switch off to charge from the Battery Tender. Shore power goes through another A/C switch to the Battery Tender and there is also a switch for the D/C output of the Battery Tender. If the Battery Tender D/C switch is off the relay is unpowered so the relay does not remain on unnecessarily. A lot of things have to be set correctly for the Battery Tender to charge the battery. Is it any wonder that I usually just use the three stage converter to maintain the battery? Fortunately a flashing light on the Battery Tender panel reminds me if it is powered but not connected to the battery. I think one reason I used D/C power for the relay was a reluctance to put both A/C and D/C connections in the same junction box. The D/C switch is DPDT with center off. Up enables the Battery Tender output and relay coil, while down turns on a D/C utility light. Perhaps I will think about changing the relay power to the converter A/C power. After all, this is a hobby.

Bill

PS Some photos in my album show my electrical system. Comments attached to some of the photos indicate component source or my wiring arrangement. My Little Guy arrived with no electrical system except three AA battery operated lights.

[wlooper89]

After thinking about the two charger question some more, I decided to stay with my present arrangement with a D/C powered relay. The requirement for the battery switch to be off also ensures that the Battery Tender cannot be connected to the trailer and a possible load it is not designed to handle. And this way my brain gets some exercise just remembering how to turn on the Battery Tender.

Probably I have digressed a bit from the original question. My posts have described a way to have two chargers that work, but not at the same time. The two chargers are very unequal. The WFCO converter puts out 25A and the Battery Tender only 1.25A. As mentioned earlier I would not want to connect them both at the same time. The relay makes this impossible even if one attempts to connect them both.

Bill

[cpaharley]

Although this post is old and so am I, I'm just getting to reading it. I'm to assume that everyone recommends that you disconnect your solar charged while plugged in to 120 and your converter is working? I thought the whole purpose of the 5 watt chargers was not to have to disconnect while the battery was being charged elsewhere? Am I wrong?