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Q: Battery System for a Cart in Retail Store ( Answered,   0 Comments )
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 Subject: Battery System for a Cart in Retail Store Category: Computers Asked by: 3horn-ga List Price: \$5.00 Posted: 22 Jun 2002 13:22 PDT Expires: 22 Jul 2002 13:22 PDT Question ID: 31651
 ```I am trying to create a roll around cart for use in a retail store that has the following equipment: laptop with wireless card, barcode scanner, barcode printer, possible receipt printer, and a battery source of power (mainly for the printers). My question is, what is the best equipment to use for this battery unit. I need something that can be plugged in to charge, and will last approx 2-3 hours out on the retail floor. I thought about a uninterruptible power supply, but someone warned me that this wouldn't work.```
 ```Greetings, 3horn! I've been playing with this stuff for about the past 10 years or so, mainly in the avenue of making too much noise with pro audio gear out in the middle of nowhere, powering it off of a car battery. I assume this will be A/C powered equipiment, and not specialty D/C powered equipiment. Given that assumption, you have two problems. 1) How to get A/C out of a battery, and 2) how big or how many batteries you need to sustain that power for 3 hours. The first problem is an easy one to solve: A DC to AC Power Inverter. These are devices that covert 12 volts DC to 120 volts AC, 60 HZ. There are two kinds on the market: ones that produce a modified sine wave and ones that produce a pure sine wave. Modified sine wave inverters have more noise on the line, and will require extensive filtration to clean the power up for sensitive electical components. Pure sine wave inverters make an AC power that is most similar to the power from a wall outlet. Laser printers, in particular, are sensitive to 'dirty' power, and will benefit most from a pure sine wave inverter. A good description of square wave, modified square wave and sine wave power output is at this page: http://www.almac.co.uk/proven/PAGES/invert.htm To determine what size you will need, just add up the power consumption of all of your equipiment. If you are using a laser printer, you may be looking at over 600 watts just for that. The laptop and accessories could run 20 watts to over 100 watts. Once you have the total wattage draw, take a look at some of the following offerings: Majorpower.com offers serious power inverters, some of the best I've seen: http://www.majorpower.com/inverters/?source=google I particularly like this, the Pro Sine series: http://www.majorpower.com/xantrex/prosine.html They provide very clean AC power, with less than a 3% variance from a 60hZ sine wave. However, it may be overkill for your project; they start at 1,000 watts and go up, as well as having a starting price tag of over \$700. Less expensive power inverters can be found at dcacpowerinverters.com: http://www.dcacpowerinverters.com/power_inverters.html Also, NexTag offers a large list of power inverters and pricing from various online merchants: http://www.nextag.com/serv/main/buyer/OutPDir.jsp?nxtg=459437_C83ACF7A2CE79A3E&node=&otherForm=n&doSearch=y&advanced=n&searchnode=-1&search=power%20inverter Now that you have the power inverter in hand, you need batteries. Deep-cycle batteries will provide the longest service life and number of charge-discharge cycles. A deep cycle battery will outlast a regular car battery by a factor of 2 to 10 times or more. An excellent FAQ on deep cycle batteries is found at the Deep Cycle Battery FAQ: http://uuhome.de/william.darden/dcfaq.htm The time a battery will last is measured in amp-hours; how many amps can be drawn for how many hours. If a battery is rated at 10 amp hours, it can have 10 amps drawn for one hour, or one amp for 10 hours. What you'll want to know is how much amperage the power inverter will draw at peak load. Most power inverters do not list their amp draw at peak load, just an efficiency rating. For example, the ProSine 1000 lists an 89% efficiency. At max load, 1,000 watts, that would equate to a draw of about 1100 watts from the battery. 1100 watts at 12 volts is 91 amps. So, for a 3 hours use, you would need 275 amp-hours of reserve capacity. 1000 watts / .89 efficiency = ~1100 watts. 1100 watts / 12 volts = 91 amps. 91 amps * 3 hours = 275 amp-hours. One maker of deep cycle batteries is the Trojan Battery Company located at: http://www.trojan-battery.com/default.htm They have very good resources there, as well as a battery picker that can help you to choose the battery you will need. I hope this has provided you with enough information to complete your project. Good luck, and if you need further clarification, just ask! Further Reading: DonRowe.com Power Inverter FAQ: http://www.donrowe.com/inverters/inverter_faq.html Search Strategy "power inverter" "deep cycle battery"```