Adding 4D AGM #2

[kmessinger]

My Sprinter has 1 4D AGM mounted on the driver's side. I am removing a g/w tank from under the passenger side and installing an additional 4D AGM. The batteries will be about 60 inches apart. Will that much of a run cause any problems in wiring them together?

Thanks,

I-know-nothing-about-batteries-Keith

[Ford_6L_E350]

Run the same length of wire (2gauge I'm guessing) from each battery to the tie point and there will be no problem.

Well, unless one old and one new battery is a problem. The older, weaker battery will always pull down the newer, better battery.

Mike

[daveb]

Keith I agree with Mike...I had a 2 year old battery that was in great condition but because they cost so much I didn't take a chance and added two new batteries over just adding one to the existing 4-D to minimize the teeter totter effect. But you're in the same boat if one of the new batteries fail for whatever reason, so it's a gamble. Usually most experts suggest that 1 year old is the cutoff date with a battery that has been properly maintained.
Another thing you might be willing to do is add a separation switch so you're only using one battery at a time (if you want to), but I've always thought more stuff like wires, connections, and switch gear just means more to check or more to go wrong. Still, it's a common practice in the boating industry. One thing is you can keep it connected as a rule and if you see the charging length/amperage change, isolating the batteries will help reveal the problem.
I just added (in 2007) 2 new batteries and so far so good.
Dave

[jage]

I didn't take a chance and added two new batteries

SMB took that gamble for me and the first battery was bad and just caused havoc with the new one until I replaced them both.

And I don't get the same length of wire- sure, if you're tying to a common point away from both, but couldn't the new battery location just be tied in parallel to the existing battery location, since it's all in parallel?

Or is it better to do equidistant runs to a common point?

[Ford_6L_E350]

Jage,

It rarely matters if the wires are the samelength.

But, it can make a difference when you have heavy current draws (that's why you have two 4Ds - right?). With alot of current draw, the wire can cause voltage drop and most of the load will be on the battery with the shorter wire.

Use of that microwave could shorten the life of one battery.

Mike

[LenS]

As you go up in Ah on the house battery side. More batteries and/or bigger batteries, how do you know when it is time to upgrade the engine alternator?? Is there any kind of rule of thumb??

[Ford_6L_E350]

LenS,,

You need to upgrade your alternator when the current one will not keep your batteries charged in normal use.

It's not the size of the batteries, it is the usage, both of the batteries and the van, that will determine how much alternator is enough.

Mike