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Home » Sensors » Xantrex Link 10 (Emeter) |
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Xantrex Link 10 (Emeter) OCID cn00000196 |
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Xantrex Link 10 (Emeter) by Andy Gotterba created 8/23/2002 submitted 8/23/2002 05:49:39 PM Formerly the Cruising Equipment Emeter, the Xantrex Link 10 is one of the most common amp-hour meters. This is a summary of my experience with this meter. Many a question has been posted on the ASC mailing list asking about what amp-hour / kilowatt meter to use. The choice can be critical: your Ahr meter is your fuel gauge; good strategy relies on its accuracy. Here are my experiences with what I believe is the most popular: the Xantrex Link 10 (Cruising Equipment Emeter) The Link 10 measures current via a shunt. Though this adds a tiny amount of resistance to the line, I believe it is more accurate than a Hall effect sensor (though the Link 10 may not take advantage of this accuracy). Its current measurement has a resolution of 0.1 A while below 40 A, and 1 A resolution up to 500 A. Though accuracy is listed as 0.8% + least count of resolution, I was able to obtain about 0.8% + 0.4 (least count of resolution) by carefully matching each meter with a particular shunt. The Ahr accuracy is the current accuracy multiplied by the amount of time for which the meter has been running without being reset. While this accuracy is adequate for normal electric vehicles, it is marginal for solar cars. The meter considers 0 to be a full pack, and counts down as you use power. When the recharging conditions (which you set) are met, it resets to 0, erasing all accrued error. This is fine for a battery pack that you fully discharge, then charge back up to full, then discharge again. But with a solar car, you pack starts full, and may not be completely full for the rest of the race (or at least until the next staged start). Therefore, error accumulates for the entire period of the race, up to about 240 hours (or 150 hours, if you short the sense leads when charging is not allowed), giving an error of more than 24 Ahr. Therefore, I would recommend that after a few days, you measure the battery voltage each night, when the pack has had time to settle, and reset your meter to this value for use the next day. However, the Link 10 may still be attractive, especially for lead-acid packs. The Link 10 is designed to for lead-acid packs, and, if you know the constant parameters for your batteries, can take such things as battery temperature and discharge rate into account. Also, with an RS232 interface, it can be used to collect data and send it over your telemetry system. Though other teams used the Link 10 without incident, I experienced numerous problems during ASC 2001. At times, the displays would go blank. At others, the current sense leads would seem to disconnect, and the current would float until it reached –500 A. Remaking my connections did not help. As pure speculation, I would guess that these problems might have been caused by temperature, which exceeded 50 C. Xantrex does not list a maximum temperature for proper operation. The Link 10 retails for around 200 USD; 400 USD with RS232. Voltage prescaler (for packs exceeding 50 volts) is ~100 USD, and a temperature sensor is about 50 USD. Solectria and Brusa also have amp hour meters, and are listed as having greater accuracy than the Link 10 (Solectria: 0.01 amps). I have not used them though, and don’t know how they perform. If you do, write it up and post it here! More questions about my experience with the Link 10? agotterba@Ihatespamif youarearealpersonyouknowtoonlytypehotmail.com 594 words | turret
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