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Forum Index : Windmills : Battery Bank Cross-Tie Question
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| floodrod Regular Member  Joined: 08/07/2009 Location: Posts: 70 |
Heya, My battery bank is 645 amp hours, about 3.5 years old wet flooded batteries. I have 3 strings of 6v batteries. The batteries connected on the Positive side seem to get the most abuse, as all the corrosion forms there, and those batteries have acid drip stains, as opposed to the negative side which are all clean. So I found some info about cross-tying the batteries to equal out charge and discharge. SO I went ahead and cross-tied all 12 batteries. No issues thus-far. My question is: On the diagrams, cross tied banks show the positive lead going to one battery on one end, and the negative going to the opposite end. But on my setup, the Positive and Negative leads connect more like Buss-Bar style. With a cross-tied bank, is it OK to connect pos and neg leads to a common bus bar, or must they connect to 2 individual battery terminals? Thanks |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hey Floodrod You may need to draw a diagram or take a picture to explain, or give a link to the diagrams you've seen. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| floodrod Regular Member Joined: 08/07/2009 Location: Posts: 70 |
Sure.. 
The dotted lines is the cross-tie. Exact same as my setup, but mine has 1 more row of batteries. Notice the battery feeds go to 2 battery terminals. If my parallel connections at the end battery rows go to a buss bar, I assume I can just hookup to the Buss? |
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yahoo2 Guru  Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
what they try to do is give each battery the same total cable resistance. So if you trace a path through the circuit past each battery the total length of cable and number of connections should be the same for each cell. unfortunately your problem with the acid is more likely to be as a result of sulphation. usually the positive grid is forced to expand from the growing crystals and this in turn distorts or damages the seal around the +ve post. The acid will then wick up the post from capillary action and evaporate the h20. if you have a close look (measure it) you could find that some of the posts are higher than others. battery damage sometime measuring is not required 
Bit of acid is not the end of the world, just means a bit more cleaning. I'm confused, no wait... maybe I'm not... |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Floodrod The interlacing of the battery bank like this equalizes any small differences between pairs but is best done from a new set that the standing voltage of each pair is matched, without matching the slight differences can result in cross current in each pair, resulting in losses by self discharge, this is more of a problem in stand by banks, that are just floating most of the time, on a working bank the constant load charge cycles make it less of a problem, the only time I have had problems with it was when a farmer fitter a new set of batteries next to an older set, some 10 years difference, so the internal resistances due to longer term sulphation, natural degradation of the plates was different, it reduced the capacity of the newer cells and required more charging, indicating an internal self discharge current was flowing. The other case was different SG of some of the coupled batteries, caused by either more sulphation in some or perhaps a slight difference in the SG of the electrolyte when the batteries where initially flooded, in both cases a long treatment with a desulphator helped and a little bit of acid to balance the SG of the batteries on the second set. I am having similar problems with my batteries at the moment as they are SLA 15 years old and I am trying to rectify the dehydration in various stages across 50 batteries. some are badly sulphated and others are OK, so I have had to go for selective desulphation and it is very time consuming. All the best Bob Foolin Around |
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