RV PRO

June '18

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58 • RV PRO • June 2018 rv-pro.com A F T E R M A R K E T discharge, operating temperature and aging of materials. Battery manufacturers typically underrate their cycle life number to ensure they will last well past their warranty limit of up to five years. What are the high and low operating temperature limits for (LFP) lithium batteries? Lithium batteries have a wide tem- perature range of operation (-4 to +160 F / -20 to +70 C). Lithium batteries can be stored and discharged at the upper and lower temperature limits. However, charging currents should be reduced near these limits, and lithium-iron phosphate batteries must not be charged at temperatures below freezing. Customers should consult a battery manufacturer's website for temperature limit specifications. What are the other advantages of a lithium battery system? Lithium batteries last years longer than lead/acid batteries and require minimal maintenance, maintain their charge during long periods of storage, and are about half the weight or less than that of an equivalent AH rating of a lead/acid battery. An RV dealership's dry campers will appreciate that they also provide up to three times the power of lead/acid batteries and recharge up to six times faster with the same sized charger. This results in less generator operating time and faster recharge. The reason for this faster recharge rate is the unique chemistry of lithium batteries, which allows them to accept the full charge rating of the charger until it almost reaches full charge. In contrast, the chemistry in lead/acid batteries can only accept the full charge at the absorp- tion phase state and then the charge cur- rent rapidly drops down, making a full charge take much longer. How fast will a lithium battery recharge? The answer depends on the total amp hour (AH) rating of a lithium battery pack and the current output rating of a charger. For example, a 100-AH lithium battery connected to a Progressive Dynamics PD9160L (60-amp) charger would com- plete the recharge time as follows: (100-amp hour battery divided by 60 amps per hour recharge rate) equals 1.7 hours. However, as the state of charge nears completion, the charge current is gradu- ally reduced, so the real total time would be around two hours. Under these same conditions, a lead/acid battery would require about six to eight hours, more or less, to reach full charge. Will a solar charging system work in conjunction with a lithium charger? Yes, the two systems can be operating at the same time. A solar power system should have a solar controller that allows it to be set to limit the maximum charging voltage from the solar panels. This max- imum voltage should be set for 14.6 volts for lithium-iron phosphate batteries. Can a lithium battery be recharged from a vehicle alternator? Yes, but not necessarily to full charge, due to the fact that most alternators are adjusted for the lower voltage require- ments of the vehicle lead/acid battery (approximately 13.9 volts). Lithium bat- teries require 14.4 to 14.6 volts to fully charge. That being said, users can get up to approximately a 70 percent charge, depending on the depth of discharge and distance driven while recharging from a vehicle's alternator. How much does it cost to update to a lithium battery system? That will depend on the size (amp hour rating) of the lithium battery pack and amp rating of the charger an RVer plans to install. A typical RV would have at least a 100-AH lithium battery, which would be equivalent of a 250-AH lead/acid battery. This, coupled with a PD9160LAV (60-amp) charger, would provide a two-hour recharge time. Based on pricing available on distrib- utor websites, this upgrade would cost a minimum of about $1,200. (For more information regarding updating an RV to a lithium power system, click on the following link on Progressive Dynam- ic's website: www.progressivedyn.com/ lithium-converter-replacement-units). In an RV that has a 45-amp converter/charger, can a larger 60-amp or 80-amp unit be installed to further reduce the recharge time? No, an RV wiring system is designed to safely handle 45-amps increasing it to a 60- or 80-amp charger could cause a thermal event! When updating to a lithium battery system, stick with the same size converter/charger as presently installed in an RV. Again, with the faster charge rate that lithium batteries can accept, even a 45-amp lithium charger can recharge a 100-AH battery, (100 AH divided by a 45-amp charge rate) that would equal about 2.2 hours, plus the extra time required at the end of the charge due to a lower charge rate, would equal an esti- mated recharge time of about three hours. How should an RVer store their RV lithium battery during the winter? Another advantage of lithium-iron phosphate batteries is that they do not require a trickle charge during long periods of storage. In fact, disconnecting the charger during winter storage or long-term inactivity and allowing the battery to rest is actually beneficial and will improve long term battery life. Before putting an RV into winter storage, technicians or RVers simply connect it to 120 VAC power for up to 10 hours for large battery packs and fully charge the battery, then remove AC power and hit the battery disconnect switch. In the spring, it will be ready to accept a full charge before a first camping trip. Lithium batteries have a very low self discharge rate and only lose 2 percent to 4 percent of their charge per month. In conclusion, it's time to consider updating to a lithium battery system, especially if an RVer is going to be dry camping frequently.

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