Battery SG

[rweis]

I have a almost new (last april) Interstate RV/Deep Cycle 12v battery. I have been charging it for about 3 weeks with a gradual taper computer controlled charger.



The sg in 5 cells is 1300 (green on the hydrometer), but one cell is 1150 (white on the hydrometer) and will not go any higher.



I took it back to the auto parts place I got it and they said unless it is 15% difference it is not a bad cell.



The weak cell would have to go to 1105. 1100 is the weakest reading in the red discharge area on my hydrometer float.



Is this right?



The highest cell show FULLY charged and the "weak" cell show TOTAL discharge? Seems weird to me, but that is why I am asking.



Thanks,



Bob Weis

 

[rweis]

TTT,



Zero ideas?



Bob Weis

 

[GerryDrake]

challenge

I suspect that if you were to make them a challenge to put another one similar on a charger for a couple of days in their store, then with you there, check the SG, and if there were ANY cells that had, say 1/2 that variance, you'd go away happy, but otherwise they swap you out... you'd have a new battery...



Or. . contact the manufacturer, tell them the situation and ask them (e-mail or USPS so you'll have their response in print) what is an acceptable variance...

 

[rweis]

Sent email to Interstate with question of what is acceptable variance.



Will report back when replied to.



Bob Weis

 

[slo-ryde]

Here's a quote from the Interstate battery website for specific gravity testing. It looks like your battery is bad. I would print out the web page and "educate" the people you bought the battery from!



1. Draw electrolyte into the hydrometer a few times so that the float reaches the same temperature as the electrolyte. This will increase the accuracy of your readings.





2. Hold the hydrometer vertically so that the float is free and does not touch the inner walls of the barrel.





3. Hold the hydrometer so that the liquid is level in the barrel and at eye level.





4. When you draw the electrolyte, make sure that the hydrometer is full.





5. Check each individual battery cell. If the specific gravity varies more than . 050 or "50 points" among the cells while the battery is at a 75% state of charge or above, then the battery is bad and should be replaced. The cells that have a specific gravity of 50 points less than the highest cell are bad cells. A hydrometer reading of 1. 265 or greater at 80°F indicates a full charge for Interstate batteries. To determine the battery's state of charge, compare the hydrometer reading to the Specific Gravity Chart.





6. To get the most accurate hydrometer reading, you should adjust your hydrometer reading according to the temperature. If the electrolyte temperature is ABOVE 80°F , ADD . 004 (called "four points") to the hydrometer reading for each 10 degrees above 80°F. If the electrolyte temperature is BELOW 80°F, SUBTRACT four points from the hydrometer reading for each 10 degrees below 80°F.





Go to www.interstatebattery.com for the links...

 

[rweis]

Thanks Slo-ryde that is exactely what I needed. I went to the site but did not drill down far enough to find the references. I now have a print out and will take that to them in about a couple of weeks. I need the batteries for this weekend RV'ing then charge them up for a week to have them really as full as they can be charged.



Thanks again,



Bob Weis



PS TDR is absolutely awsome!, finding something like this is like finding a needle in a haystack, but someone on TDR knew where to look!

 

[slo-ryde]

I can't take all the credit, batteries get discussed in the towing forum on a regular basis. Trojan has a decent website too with lots of good information on the care and feeding of batteries. Good luck!