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electrical:solar:synopsis_puzzle2 [2018/02/10 14:11] frater_secessus [Synopsis: HandyBob's RV Battery Charging Puzzle] |
electrical:solar:synopsis_puzzle2 [2020/10/11 19:48] |
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- | This page aims to distill the knowledge contained in HandyBob' | ||
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- | Particularly useful and pithy statements are quoted directly under fair use. | ||
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- | ====== Synopsis: HandyBob' | ||
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- | [Note from Secessus: | ||
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- | HandyBob and his wife are fulltimers in a 5th wheel and have no generator. | ||
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- | ===== charging batteries is like airing up tires ===== | ||
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- | > " | ||
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- | ===== volts, volts, volts ===== | ||
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- | Manufacturers give absorption voltages ranging 14.4V - 14.8V (temp compensated) and that is not too high. | ||
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- | Chargers do not read specific gravity, but can estimate [[electrical: | ||
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- | > " | ||
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- | > "The difference between 14.4 & 14.8 volts is not 3%. That difference is nearly 20% of the charging range (12.2 to 14.8 volts)" | ||
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- | Use short runs and oversized wires to minimize voltage drop. | ||
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- | ===== battery monitors ===== | ||
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- | Most OEM monitors (led displays, gauges, and idiot lights) are bad, tricking the owners into believing their batteries are fuller than they are. The monitors will read too high when charging and too low when discharging. | ||
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- | The battery bank must rest at least an hour before a reasonably accurate measurement can be made. A hydrometer reading is best but a multimeter will get you in the ballpark: 12.7V is full and 12.2V is 50% state of charge (the bottom of the deep cycle). | ||
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- | Battery bank life will be longer when it is charged fully and not discharged past 50% DoD. A full charge is also important to capacity: | ||
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- | > "a 95% charged battery has 10% less usable power in it than a 100% charged one, since you are trying to keep it in the top 50% of its operating range (5% of full = 10% of 50%.)" -- HandyBob | ||
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- | ===== recording meters ===== | ||
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- | Bob recommends the use of AH e-meters like Link or the Trimetric 2020/2025: | ||
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- | > " | ||
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- | The meters will require configuration/ | ||
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- | It is common to find appliances use less power than their placards state: | ||
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- | > "The label has to show what the appliance will not exceed, not the actual energy use." | ||
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- | ===== batteries ===== | ||
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- | Bob recommends matched 6v golf cart batteries. | ||
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- | Get charging specs from the manufacturer and follow them; this is particular important with new or exotic chemistries. | ||
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- | In multibattery systems the connecting cables should be the same length and gauge. | ||
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- | ===== converters ===== | ||
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- | Most OEM [[electrical: | ||
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- | ===== generators ===== | ||
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- | A generator with DC battery charging output is better than running the converter or auto charger on 110v. | ||
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- | ===== solar ===== | ||
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- | Bob runs his RV off 345W of panel and 450AH of 6v deep cycle batteries. | ||
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- | > " | ||
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- | When seeking advice: | ||
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- | " | ||
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- | ===== charge controllers ===== | ||
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- | Get an oversized [[electrical: | ||
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- | Bob prefers Morningstar. | ||
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- | ===== MPPT boost controllers ===== | ||
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- | They work but the gains are found in specific scenarios like deeply discharged batteries. | ||
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- | ===== wiring ===== | ||
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- | "Big wire" is cheaper than panels for a similar gain in power. | ||
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- | Wiring from panels to controller is important; | ||
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- | Use stranded wire, the type (building, automotive, welding) is less important. | ||
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- | > "big wire is there to limit voltage drop, not to carry amps." -- HandyBob | ||
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- | ===== inverters ===== | ||
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- | Use a properly sized [[electrical: | ||
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- | MSW is fine unless you know you have something that needs PSW: " | ||
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- | "Soft start" inverters work work well. | ||
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- | Many inverters have a high voltage disconnect (Vhvd) of 15v. Temperature compensated charge controllers can hit 15v easily. | ||
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- | ===== installation considerations ===== | ||
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- | Install the charge controller near the batteries. | ||
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- | Locate solar panels so they are not shaded. | ||
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- | ===== fusing ===== | ||
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- | Bob prefers fuses to automotive-style circuit breakers. | ||
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- | Avoid fuse holders with springs in them. | ||
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- | Fuse every positive wire within a few inches of the battery. | ||
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