Charging tale of woe

[SMan]

So after having many RV's both trailers and motorhomes along with ATV's and collectible cars that sit extended periods of time I have replaced many a battery over the years. I had a small Battery Tender that I used in my Chinook and decided to pick up their more expensive Battery Tender Plus unit. I put it on any every thing seemed to work fine however after a few months the unit was doing its alternating flashing light indicating it may be a polarity issue. By this time it had drawn my 1 year old Interstate batteries down to 3 volts which I think has essentially ruined them. They have charged to 13.6 volts but I don't have confidence they will now hold a charge. I took the charger out and put it on a battery in my garage and it is functioning correctly. It goes into the flashing mode after about a day back in the Chinook.

I am not much of an electrical guy but was wondering if anyone has had a similar experience or is familiar with the Battery Tender Plus. Is there a special way to hook up to a dual battery set up like on the Chinook?

Signed Low Spark near Seattle

[Blue~Go]

Is there a special way to hook up to a dual battery set up like on the Chinook?

Just to clarify, since there could be two interpretations of dual battery (house plus start, or house plus house), you are speaking of two 12-volt batteries hooked up in parallel to make a house bank, right? If so, then normally you would hook the positive charger lead to one battery's positive terminal, and the negative charger lead to the other battery's negative. You could also just hook up to one battery, but including both of them would balance them better.

RE: the painful problem. Is there any way you could have hooked the leads up backwards? (i.e. positive charger to negative battery post and negative charger to positive battery post? That would drain the bank, plus I imagine give the reverse polarity warning. (And maybe you just didn't notice at first?)

Just for completeness sake: Have you checked the water level if you have flooded cell batteries?

If the charger was "taking" and not giving, then your separator should have remained open I think, and your start battery would be fine. But maybe check it too.

I have used the tiny Battery Tender on my boat (800 ma of smart charging, stand back!), and if I remember correctly you can't hook the leads up to the battery charger itself backwards as there is a plug that only connects one way. The same on yours?

[SMan]

Thanks for the quick reply BG. To clarify I am referring to the two house batteries. The start battery is functioning normal. I'll try to get a picture in the next few days of my wiring. (I'm tied up Monday and Tuesday.) I supposed the Battery Tender leads could be wired wrong although my BT Junior worked fine. I watched the "BT Plus" for quite a while after attaching it without the alternating flashing LED's. For now I can go back to my cheap but reliable BT.

[SMan]

The fused side of the BT connection is on the positive so absent of some other issue it should be correct.

[Blue~Go]

It certainly does look like you have the BT hooked up correctly. So .....? How was the water level (if checkable)? What was the battery(s) voltage when you hooked it up? I wonder if something that didn't have to do with the battery tender could have brought them down (coincidentally).

I've never hooked a charger up to the "opposite" posts from the ones that lead to the bus bars (the crowded ones in your case), but I can't think why it would make a difference to go the other way. (However, coffee is now being consumed, so maybe I'll think of something.)

A couple of suggestions for your bank:

1) An appropriate fuse on the positive post or very nearby (can't see if there is one).

2) Bus bars. Then you can eliminate that giant mess of cables going to the battery posts.

3) Eliminate wing nuts. They can't be tightened correctly (just use regular washer/lockwasher/nut, or serrated flange nuts).

[SMan]

Thanks for all the input and suggestions BG. Water is good in the batteries. The voltage reading was 3.6v when I found the problem. After simply plugging into house current for a few days the batteries are at 13.6v (with 110 power removed) There is a fuse but not sure what type. I'll check and report back hopefully Wednesday.