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Join Date: May 2004
Location: San Antonio, TX
Posts: 2,466
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battery & charger for trailer - anyone know how to size?
I need a battery(s) and charger to go into the tongue box on my racecar trailer. I have no idea what size and/or brand for either.
I'll have a generator with me at the track, so recharging during a race weekend is doable. Would prefer not to have to recharge everyday, but can if needed. Power usage will be... - car stereo - I can't find power requirements for this, but it not super high powered. 20W RMS and 50W max. This will be played on low volume for most of the day. - XM Onyx - 9-16 V DC, 500 mA (max). Will be on for most of the day. - interior lights - 6 LEDs using 1.05A total. Will be on for say 8 hours a day. - 12V fan - uses 2.5A. Will be on for 8 hours a day. - additionally, there will be some 12v use from recharging iPhone and iPad as well as maybe an hour or two/day of 12v laptop use. The gen (Honda 2000i) will be run at least once per day for coffee. So, I guess an hour or two of charging will happen regardless. So, with that all said, can anyone advise? I am fully ignorant... Thanks, Skip
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02-09-2012, 06:36 AM
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MAGA
Join Date: May 2004
Posts: 10,781
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I have no clue, but FWIW I ran heavy wire from my truck battery to my acc plug on the trailer pigtail socket and run my trailer mounted winch off of power from my truck..... I did not feel like buying yet another battery.
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German autos: '79 911 SC, '87 951, '03 330i, '08 Cayenne, '13 Cayenne 0% Liberal Men do not quit playing because they get old.... They get old because they quit playing. |
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02-09-2012, 06:53 AM
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Join Date: Apr 2002
Location: motown
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Without getting too technical, battery capacity is rated in amp-hours, which gives a general idea of how many amps can be supplied over a period of time. If you multiply the amp draw times the length of time you need to supply that, you get amp-hours.
In your example, the fan draws 2.5 amps and you want to run it for 8 hours, that's 20 amp-hours. Between your stereo and the XM, you're probably looking at between 1 and 2 amps draw; more if you turn up the volume to jam to Zepplin; so 12 hours would be 12-20 amp-hours or so. Phone chargers are typically 1/2 amp or so, and a laptop charger might pull up to 10 amps. All together, you're looking at roughly 50-70 amp-hours over the course of a day, depending on how much the laptop gets used. A good 12 volt deep-cycle battery will provide up to about 120 amp-hours, so one fully charged battery should be able to cover a day and a half. You could hook up two batteries in parallel (+ to + and - to -) and get 240 amp-hours. Keep in mind that putting power back into the battery works the same way; if you have a 10 amp charger, it needs roughly 5 hours to put 50 amp-hours back into the battery, so two hours of running your generator and charging will more or less cover the power to run the fan. I'm simplifying things a bit here and ignoring things like efficiency and heat loss and that kind of stuff, but this should give you an idea of how this works.
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-John '94 968 Iris Blue '85.5 944 White - Rally Cross and wrenching practice '84 944 Gemini Grey (gone, but missed...) |
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02-09-2012, 11:04 AM
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John- What you say makes sense and is exactly what I was hoping to understand. THANKS!!!
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02-09-2012, 11:10 AM
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Location: MD
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Similar setup on my boat, but I have 2 batteries. A small solar panel, ~$40, on a sunny day keeps the lights on and the stereo playing. I try to avoid using the engine as much as possible. Keep in mind you dont want to go much below 50% capacity with most batteries, life span goes down considerably.
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02-09-2012, 11:27 AM
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Join Date: Jul 2000
Location: So. Calif.
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Quote:
Sherwood |
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02-09-2012, 11:36 AM
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Location: San Antonio, TX
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Anyone recomend a charger?
Thanks again all...
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1972 911T 1972 911E "RSR" |
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02-09-2012, 03:09 PM
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Navin Johnson
Join Date: Mar 2002
Location: Wantagh, NY
Posts: 8,815
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To keep your battery topped up you can get something like this
Schumacher Ship n Shore When you run your generator just have it plugged it and connected to the trailer battery, (which should be a deep cycle battery) Or as other mentioned you can get some solar panels to toss on the roof, that could run those appliances all day and not make any noise... Which is sort of nice in the pits... I hate being near someones pit set up who runs a generator 8 hours with a blown out muffler....
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Don't feed the trolls. Don't quote the trolls  http://www.southshoreperformanceny.com '69 911 GT-5 '75 914 GT-3 and others Last edited by TimT; 02-09-2012 at 04:18 PM.. |
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02-09-2012, 04:16 PM
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