Comments on: There are battery voltages and there are battery voltages! http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/ RV Campground & Camping Information - RV, Motorhome, Camper, Travel Trailer & 5th Wheel Owners Sat, 21 Nov 2009 20:13:05 -0600 http://wordpress.org/?v=2.8.4 hourly 1 By: Roberta Callum http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57867 Roberta Callum Tue, 25 Nov 2008 23:39:45 +0000 http://blog.rv.net/?p=2910#comment-57867 Hi Brad & Lucy, I just found your Blog after Lucy gave me the www. address. Hope you are doing well .Will you be in Seattle for Thanksgiving, as planned ? Bet you are having a blast ! Good luck ! Roberta Hi Brad & Lucy,

I just found your Blog after Lucy gave me the www. address. Hope you are doing well .Will you be in Seattle for Thanksgiving, as planned ? Bet you are having a blast ! Good luck !

Roberta

]]> By: G.M http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57524 G.M Sun, 23 Nov 2008 05:40:03 +0000 http://blog.rv.net/?p=2910#comment-57524 Brad most excelten article. we have to agreee with the others though about the different capacty batts having different load rate times but the low voltage cutoff should be the determining bottom factor. However, one then assumes that the battery was fully charged and let set about a hour before the test was begun to get a true picture of its condition. Load bank testing , as I call it, is the best way to insure that you have a great trip with the RV without any electrical problems. One should be careful not to demand too much current suddenly from any battery (checking manufacture data) or one could find a exploded view of it all over the floor. Oh and always practice safety... protection of the eyes is very important working around batteries so we found. You may want to expand on that too. Again good article, thanks some of the other techinical batteries that should disucssed are the gel cell, flooded and the sprial wound optima ones. Now if we can just figure out what the volt meter is. How to hook it up to the terminals etc... if not part of the load test equipment . Most of the car voltmeters are to say the lest in- accurate so we have found. Thus, using a good quality volt meter is a good idea along with the load bank. Also a lot of MH and RV's have dual batteries with rotary switches.... one needs to assume that the battery being tested is removed from the system also. Would also be nice to see a article about battery sulfation and how the voltage current plays with that in the RV after the battery sits. and of course the proper way to charge it back up after the load bank test. (constant current or constant voltage?) Looking to read more about your work. Brad most excelten article. we have to agreee with the others though about the different capacty batts having different load rate times but the low voltage cutoff should be the determining bottom factor. However, one then assumes that the battery was fully charged and let set about a hour before the test was begun to get a true picture of its condition.

Load bank testing , as I call it, is the best way to insure that you have a great trip with the RV without any electrical problems. One should be careful not to demand too much current suddenly from any battery (checking manufacture data) or one could find a exploded view of it all over the floor. Oh and always practice safety… protection of the eyes is very important working around batteries so we found. You may want to expand on that too. Again good article, thanks

some of the other techinical batteries that should disucssed are the gel cell, flooded and the sprial wound optima ones.

Now if we can just figure out what the volt meter is. How to hook it up to the terminals etc… if not part of the load test equipment . Most of the car voltmeters are to say the lest in- accurate so we have found. Thus, using a good quality volt meter is a good idea along with the load bank.

Also a lot of MH and RV’s have dual batteries with rotary switches…. one needs to assume that the battery being tested is removed from the system also.

Would also be nice to see a article about battery sulfation and how the voltage current plays with that in the RV after the battery sits.

and of course the proper way to charge it back up after the load bank test. (constant current or constant voltage?)

Looking to read more about your work.

]]> By: Fred http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57507 Fred Sun, 23 Nov 2008 03:32:49 +0000 http://blog.rv.net/?p=2910#comment-57507 Larry, a lot depends on the type, brand and model of the battery. For the lowest voltage allowed and still be okay, some brands are better than others. Also the maximum "at rest" voltage after charging depends on the brand. The Optima brand I am using has an "at rest" voltage of 12.92 volts. That would be the voltage reading at 100% charged. Optima AGM deep cycle batteries are engineered to be effectively discharged down to 10.7 volts. They then need to be fully charged using a charge voltage between 13.5 and 15. 2 volts. That of course is one cycle. I believe they can be cycled 1000 times. If you want to really know what is going on with your batteries, an Amp Hour meter is the best way. There is nothing like having numbers and measurements to make a record be of any use. Using the battery manufacturer's specs, you program the AH meter with the high and low voltage and current limits. From that point on you will get a discharge-charge cycle reading for each time. You will also get an accumlative AH reading over the life of the battery. And yes, you got to spend the money. By the way folks, Brad Sears is a retired automotive technology teacher. So, he has a professional's knowledge of automotive "things". His way of testing is quite valid for the scenario he presents. Some tests will not work with some types of batteries and some tests will work with several different type of batteries. One test that will not work with a sealed AGM battery is of course the specific gravity test. But that test is nearly foolproof with a standard starter battery. Larry, a lot depends on the type, brand and model of the battery. For the lowest voltage allowed and still be okay, some brands are better than others.

Also the maximum “at rest” voltage after charging depends on the brand. The Optima brand I am using has an “at rest” voltage of 12.92 volts. That would be the voltage reading at 100% charged.

Optima AGM deep cycle batteries are engineered to be effectively discharged down to 10.7 volts. They then need to be fully charged using a charge voltage between 13.5 and 15. 2 volts. That of course is one cycle. I believe they can be cycled 1000 times.

If you want to really know what is going on with your batteries, an Amp Hour meter is the best way. There is nothing like having numbers and measurements to make a record be of any use.

Using the battery manufacturer’s specs, you program the AH meter with the high and low voltage and current limits. From that point on you will get a discharge-charge cycle reading for each time. You will also get an accumlative AH reading over the life of the battery. And yes, you got to spend the money.

By the way folks, Brad Sears is a retired automotive technology teacher. So, he has a professional’s knowledge of automotive “things”. His way of testing is quite valid for the scenario he presents. Some tests will not work with some types of batteries and some tests will work with several different type of batteries.

One test that will not work with a sealed AGM battery is of course the specific gravity test. But that test is nearly foolproof with a standard starter battery.

]]> By: Larry Guthrie http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57342 Larry Guthrie Sat, 22 Nov 2008 01:23:10 +0000 http://blog.rv.net/?p=2910#comment-57342 I believe the test you specify. Using a load 3 times the capacity of the battery to test is a test to determine if the battery is "good". i.e. will it accept and hold a charge. It is not a test to determine when to charge the battery. The voltage on a deep cycle RV or golf cart battery should not be allowed to fall below about 12 volts. To do so repeatably will drastically shorten the life of the battery. Fess up you made a mistake. I believe the test you specify. Using a load 3 times the capacity of the battery to test is a test to determine if the battery is “good”. i.e. will it accept and hold a charge. It is not a test to determine when to charge the battery. The voltage on a deep cycle RV or golf cart battery should not be allowed to fall below about 12 volts. To do so repeatably will drastically shorten the life of the battery.

Fess up you made a mistake.

]]> By: Tom Hargreaves http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57311 Tom Hargreaves Fri, 21 Nov 2008 22:14:43 +0000 http://blog.rv.net/?p=2910#comment-57311 Good post, but for me, determining the state of charge of a partially discharged battery was always confusing because under load, the measured voltage depends on the state of charge and the current draw. For instance, and using your example, a freshly charged battery without the surface charge and with a discharge of, say, 0.1 amp, the battery voltage might read something like ~12.69 volts, whereas if the same battery were discharged at three times the amp hour capacity rating, the measured voltage might be 9.6 volts. So, sitting warm and snug boondocking in my RV and avidly watching the volt meter as the furnace kicks on under battery power (I get my jollies in strange ways sometimes), how do I know when to go start the generator because my batteries are reaching that critical 50% discharged level? I've read a lot of articles, blogs, etc. on batteries and RV electrics, but the answer to this question has been a bit vague. I stumbled on this as the best information I've found: http://www.rollsbattery.com/?q=node/51. The right answer seems to be to buy one of those monitor panels that track battery current in and out, or, lacking the funds to do that, use the SWAG (Scientific Wild-A** Guess, with emphasis on the "scientific") method . I love your posts, Brad, keep them coming! Tom Hargreaves Good post, but for me, determining the state of charge of a partially discharged battery was always confusing because under load, the measured voltage depends on the state of charge and the current draw. For instance, and using your example, a freshly charged battery without the surface charge and with a discharge of, say, 0.1 amp, the battery voltage might read something like ~12.69 volts, whereas if the same battery were discharged at three times the amp hour capacity rating, the measured voltage might be 9.6 volts. So, sitting warm and snug boondocking in my RV and avidly watching the volt meter as the furnace kicks on under battery power (I get my jollies in strange ways sometimes), how do I know when to go start the generator because my batteries are reaching that critical 50% discharged level? I’ve read a lot of articles, blogs, etc. on batteries and RV electrics, but the answer to this question has been a bit vague. I stumbled on this as the best information I’ve found: http://www.rollsbattery.com/?q=node/51. The right answer seems to be to buy one of those monitor panels that track battery current in and out, or, lacking the funds to do that, use the SWAG (Scientific Wild-A** Guess, with emphasis on the “scientific”) method .

I love your posts, Brad, keep them coming!

Tom Hargreaves

]]> By: John Shelton http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57296 John Shelton Fri, 21 Nov 2008 20:54:43 +0000 http://blog.rv.net/?p=2910#comment-57296 Brad, you "done good" with your water hose and water pressure and flow example. This is a very accurate comparison. Do not be swayed by naysayers like Rob. Brad, you “done good” with your water hose and water pressure and flow example. This is a very accurate comparison. Do not be swayed by naysayers like Rob.

]]> By: Rob Robinson http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57295 Rob Robinson Fri, 21 Nov 2008 20:53:32 +0000 http://blog.rv.net/?p=2910#comment-57295 Besides Phrannies link detailed about all RVers should read and make a copy of the following http://www.ccis.com/home/mnemeth/12volt/12volt.htm http://www.ccis.com/home/mnemeth/12volt/12volta.htm Besides Phrannies link detailed about all RVers should read and make a copy of the following

http://www.ccis.com/home/mnemeth/12volt/12volt.htm

http://www.ccis.com/home/mnemeth/12volt/12volta.htm

]]> By: Rob Robinson http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57288 Rob Robinson Fri, 21 Nov 2008 20:32:20 +0000 http://blog.rv.net/?p=2910#comment-57288 Brad just buy a $30 Battery Load tester and for God's sake quit comparing water flow with electricity. The comparison has long been called a poor if not detrimental comparison. Brad just buy a $30 Battery Load tester and for God’s sake quit comparing water flow with electricity. The comparison has long been called a poor if not detrimental comparison.

]]> By: Aaron Borovoy http://blog.rv.net/2008/11/there-are-battery-voltages-and-there-are-battery-voltages/comment-page-1/#comment-57279 Aaron Borovoy Fri, 21 Nov 2008 19:37:01 +0000 http://blog.rv.net/?p=2910#comment-57279 Electricity has always confounded me. However, with your description using the hose, I finally, finally get it! Thanks. Electricity has always confounded me. However, with your description using the hose, I finally, finally get it! Thanks.

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