| Author | Message | ||
| jaime martinez (Jaime)
Registered Member Username: Jaime Post Number: 1 Registered: 4-2009 Posted From: 68.225.216.226 Rating: N/A |
I am new to the forum as a participant but have been reading it for years, I am not a converter however I do own a converted bus. Previous owner did an excellent job on conversion so I have mainly research info to build an understanding incase I encounter an issue, best to learn from other experience when possible. I am trying to find specs for constant current for some of the more common batteries for conversions. It is common rating for batteries used for battery plants with telecom equipment.. It allows for a determination of the batteries ability to release electrons with out causing the internal resistance of the battery to increase to the point that the per cell instantaneously voltage drops to below 1.75 Volts. I currently have Interstate SRM 4D ‘s and they are ok but, I would like to research the possibility of going to a battery with a higher constant current spec. I am happy with amp hour performance but on occasion I do push the limits on current draw. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 829 Registered: 1-2003 Posted From: 67.142.130.47  Rating: N/A |
Jaime, Which parameters manufacturers choose to test and rate in their specifications vary based on the type of battery and its intended application. For example, start batteries tend to be rated in cranking amps (CA) and cold cranking amps (CCA), whereas traction batteries seldom carry such ratings. It is certainly possible to test a traction battery for CA and CCA and rate it accordingly, but since traction batteries are not starting batteries, manufacturers choose not to go through the process. Likewise, backup or "float service" batteries such as are common in large UPS systems and in telecom applications (my own personal background) are quite different batteries than the type used for RV house systems. You will not typically find RV batteries rated this way, although some manufacturers may choose to do so. The best way to find out is to surf over to each manufacturer's web site and simply look them up -- virtually every battery manufacturer now publishes their product specs on-line (and, frankly, I would hesitate to buy from one who doesn't). -Sean http://OurOdyssey.BlogSpot.com | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1415 Registered: 10-2003 Posted From: 71.58.110.9  Rating: N/A |
Generally the CCA of a battery was rated at 0 degrees F. Now they are rating a lot of them at 32 degrees F, which makes the rating significantly higher. Sort of like how Sears rate the horsepower of some of their electrical appliances, like a 4 horsepower hand held circular saw. Yeah, 4 horsepower while the smoke is coming out of the vents. The rating and actual life experienced before replacement are going to be very important/ cost effective. Getting comparable information from different companies could be difficult as Sean says. Sometimes the old golf cart batteries may be the best solution when taking cost, performance, and availability. And don't forget regular maintenance. FFred has mentioned several times in previous posts about Hydro caps for use in wet cell batteries to lower maintenance and water consumption. Spend considerable time in the archives studying past posts on battery system design/usage/ issues. There is a wealth of info from our senior and experienced posters in that area. | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 830 Registered: 1-2003 Posted From: 67.142.130.21 Rating: N/A |
Just to clarify what John just said, there are two different cranking ratings (in common use): "Cranking Amps," abbreviated CA, is a 32°F rating. "Cold Cranking Amps," abbreviated CCA, is a 0°F rating. Most reputable starting battery manufacturers provide both ratings for their start batteries, but one had best be sure, when comparing start batteries, that you are comparing the same type of rating across the board. Which rating happens to be emphasized in any given advertisement, or which one figures more prominently on the label, varies from brand to brand and store to store. -Sean http://OurOdyssey.BlogSpot.com (Message edited by Sean on April 22, 2009) | ||
| jaime martinez (Jaime)
Registered Member Username: Jaime Post Number: 2 Registered: 4-2009 Posted From: 68.225.216.226 Rating: N/A |
Understand the above information and thank you for reinforcing it. I am thinking of using a battery similar to this M12V155F. it is a very good battery per my personal experience. I have been to several of the battery manufactures web site and compared specs and I am having trouble correlating for example CCA or CA to constant current discharge. The constant current discharge allows me to work from what I need to what it would take to support it battery string wise over a given period of time. Amp hour rating is based on constant current point of peak efficiency exceeding that point reduces amp hours, so dimensioning batteries correctly gives you the best amp hours and battery life. So I guess what I am trying to ask is, How to determine battery string size. Based just on CA, CCA, amp hours. It may be cheaper to just double what I have now (Interstate SRM4D x 2 to x 4) and see how it serves the occasional need. Thanks | ||
| Sean Welsh (Sean)
Registered Member Username: Sean Post Number: 831 Registered: 1-2003 Posted From: 72.171.0.138 Rating: N/A |
Jaime, As I have written here before (check the archives), I do not recommend telecom batteries for house use unless you get them nearly free as take-outs. The battery you linked is a telecom battery. Most batteries for house use in RV's, boats, and AE applications are rated in Amp-Hours at a 20-hour rate. When comparing capacities, that is usually the best number to use, simply because it is almost universally available. The Interstate SRM-4D is not a house battery either -- it is a "marine" battery, a hybrid that is a compromise between starting capability and house use. Like all such hybrids, it excels at neither. I recommend you use starting batteries for starting, and true deep cycle batteries (traction, house, AE, or EV) for your house system. BTW, CA and CCA are ratings that apply strictly to starting batteries. Batteries designed for other purposes, such as traction or house batteries, seldom carry these ratings. To answer your question about sizing of your bank, figure your needs in amp-hours, even if you do not plan for a 20-hour usage period. You can always multiply by the Peukert coefficient if you normally plan for a shorter or longer discharge time. Then determine the allowable DoD for the type you will be using (usually from 50% to 80%) and divide accordingly to get the number of total amp-hours you need in your system. Hope that helps. -Sean http://OurOdyssey.BlogSpot.com (Message edited by Sean on April 23, 2009) | ||
| Jaime Martinez (Jaime)
Registered Member Username: Jaime Post Number: 3 Registered: 4-2009 Posted From: 68.225.216.226  Rating: N/A |
Got it thank you, (amps * 20hrs)/DoD. i.e. (20 * 20)/.8 = 500 amp hrs. I will look in to getting some more appropriate batteries as well. | ||
| Tom Caffrey (Pvcces)
Registered Member Username: Pvcces Post Number: 1279 Registered: 5-2001 Posted From: 65.74.69.200 Rating: N/A |
Jaime, one other thing that may give you a clue; you will get between 1 1/4 to 1 1/2 amp hours from a 12 volt bank per pound of battery. I prefer to use KWH with house batteries. For example, a golf cart battery runs about 1 1/3 KWH and an L16 runs about 2 1/3 KWH. Figure that you can use about half safely and maybe up to 3/4. Do not figure that an inverter is going to deliver 90% of the power it uses; with light loads, the efficiency can be quite low. I agree with Sean that you want to use only a true deep cycle battery for your house bank. For what it's worth. Tom Caffrey PD4106-2576 Suncatcher Ketchikan, Alaska |