1. What accessories come with LFMP batteries ?
The standard configuration of all GBS batteries is a 4-cell pack configured for 12 volts. The batteries come with strapping hardware and aluminum end support plates installed. Screws, washers and terminal connectors are provided with each battery purchases at no additional cost.
With our LFMP battery packages, we supply a CPU, shunt, 7” Video Display, EPS EMS boards for every cell, EMS harness cable, two 400 amp high efficiency solenoids for the UV and OV protection and miscellaneous parts for installation. We include a control panel to locate near the monitor so you can remotely operate the battery bank.
2. Why are the cells strapped as 4-cell packs ?
When large format prismatic cells are under high current load, over-charged or over-discharged, they tend to swell or deform. Swelling will result in severe degradation of capacity. In the worst case scenario, swelling will result in internal shorts. Strapping is to prevent the cells from swelling. We use aluminum plates and steel bands for strapping. Our standard configuration is 4-cell pack. Our factory can make customized strapping configurations such as 6-cell pack or 8-cell pack, if there is significant volume. The steel bands are made to specific lengths to achieve the best results of preventing swelling (it is not based on tension of the steel bands).
3. How should LFMP Li-ion Batteries be stored ?
Our batteries have characteristics of very low self-leakage rate, ~ 3% per month (NOTE: Recent battery tests have shown that a partially charged battery may loose less than 5% per year), which allows batteries to be stored over extended period of time. Batteries are to be charged to 40-60% full and disconnect all loads before long term storage. Batteries should be stored in cool temperature environment. You should check cell voltages periodically, e.g. every month, to ensure proper voltage level. If any cell voltage drops to 3.0V or under, battery needs to be recharged.
If sense boards are left installed during storage the green led will cause a slight drain which roughly doubles the self-discharge rate which will necessitate checking cell voltages more often. A simple way to disconnect the sense boards is to remove the two screws from one side of the sense board and slide a piece of plastic or other non-conductive material between the battery terminal and sense board to disconnect it from the battery.
4. What can potentially damage LFMP batteries ?
Over-discharging, over-charging, operating outside of the current specification limits and operating outside of the temperature specification limits are the most common ways of damaging the batteries.
i During charging, not using a proper charger and no EMS monitoring and protection against over-voltage can lead to an over-charging condition.
ii During discharging, no EMS monitoring of cell voltages can result in cell voltages dropping below low voltage limit, which lead to over-discharge condition.
iii Drawing extreme high current (>3C) over extended period of time (>20seconds) can result in damages to the batteries.
iv Proper operating temperature ranges are -20 to 65C (-4 to 149F) for discharging and 0 to 65C (32 to 149F) for charging. Not operating and storing batteries within these temperature ranges can result in damages to the batteries.
v Mixing batteries with different characteristics, voltage ranges, capacities, internal resistance, ages, which may lead to uneven loading across batteries, can potentially result in over-charging and over-discharging conditions.
vi Putting batteries in parallel without EMS monitoring and control can lead to unbalanced charging and discharging conditions.
5. What are the best practices to maximize the lifetime of LFMP Li-ion batteries?
Cell voltages, depth of discharge, operating temperature and current draws are the key factors determining the lifetime of the batteries. Li-ion battery cells must be operating within the specified voltage range at all times. Over-charging and over-discharging will result in reduced battery lifetime or even kill the battery. All of our batteries are equipped with the EPS Energy Management System (EMS) which will prolong the lifetime of the battery, by preventing over-charging and over-discharging conditions. The EMS is configured to automatically shut down all charge sources to prevent overcharging and automatically shut down and eliminate all current consumption when the battery is empty. Cell balancing feature of the EMS system is also very helpful to maximize the usable battery capacity while minimize the chances of over-charging and over-discharging.
Our batteries have no memory effect. Batteries do not need to be completely discharged before charging. In fact, reducing the depth of discharge (%DOD) can significantly increase the number of cycles. Therefore we recommend charging the batteries as often as possible instead of waiting for the batteries to be completely drained. If you use less than 50% of the battery each cycle, you will get much longer life.
Operating the batteries in extreme weather conditions (extreme heat and extreme cold weathers) will shorten the battery lifetime. Having a climate control system to maintain the battery temperature around room temperature will help to prolong the battery lifetime.
High current draw during discharging and fast charging current will also reduce cycle life. Charging and discharging batteries at or below 0.5C will produce the best result of cycle life. For most RV applications, this is not an issue as the typical charge rate is 0.35C or less.
6. How much current can I draw from my LFMP battery pack?
Cell voltage drops with increasing current draw. In other words, cell voltages sag with high current draw. Voltage sag may become more significant when current draw is over 2C. We recommend impulse current draw to be limited to 3C and continuous current draw to be limited to 2C. Impulse current draw must be limited within 20 seconds. Extended period of high current draw (over 3C) will shorten the life cycles of the battery, and may even damage the batteries. Typically, an RV will never draw more than 1C. 1C of a 300AH battery is 300 amps. 2C = 600 amps.
7. What LFMP battery size is most suitable for my application?
For an RV system, I recommend that you install a bank that is 2 times the average nightly consumption. For example, if you use an average of 150AH by morning, I recommend that you install a 300AH battery bank. You may want to go slightly larger if you want more time between charges. The smaller the battery, the sooner you will need to recharge it.
8. What is the recommended charging process?
There are a number of ways that the battery will be charged in an RV. For motorhomes, the engine alternator will provide charging when the engine is running. If the voltage is too high from your alternator, the OV protection will disconnect it and cycle off and on until you stop the engine. If this occurs, your alternator should be adjusted for a lower voltage, preferable no more than 14.1 volts measured at the battery.
An onboard converter or inverter charger may be used to charge from shore power or a generator. These charge sources must be adjustable to properly charge your battery. Since there are many different types of chargers, contact Starlight Solar for more information.
A PV solar system is a great way to charge our battery as the full current of the PV solar is used until the battery reaches about 98%. This feature means you will realize about a 40% improvement from your PV solar system! Many PV solar charge controllers such as Samlex, GoPower, Morningstar, and others are not suitable for charging our LFMP batteries. Please contact Starlight Solar to discuss the proper controller.
Our EPS chargers use a 3-step charging program: constant current, constant voltage and re-charging steps. At the final re-charging step, you will notice that the charger is on for a minute and off a minute and repeating, which is normal. The main purpose of the re-charging step is to balance the cells. When the charging process is complete, all the green LEDs on the charger will be lit.
9. What are the common failures of the Energy Management System?
Electrical shorts are the most common killers for the EMS system. Most common locations shorts can occur are:
i Between 12V and GND pins of the power supply inputs to the CPU
ii Between OV, UV and GND alarm outputs of the CPU
iii Between shunt connection points on the CPU.
iv Shorts introduced on the sense board strings (typically by dropped screws or screw drivers touching connectors)
Actions to prevent shorts:
i Install sense board strings before the CPU is powered
ii Install battery cover after each sense board string is installed on the battery
iii Use insulated connectors for 12V,GND, OV, UV, and shunt connecting pins on the CPU
10. What do I have to do for my EMS system if my battery configuration changes?
The CPU of our Energy Management System (EMS) is programmed for a specific battery pack configuration: cell size, number of cells and pack configuration (number of cells in parallel and series). If any of the conditions changes, the CPU of the EMS system needs to be sent back to Starlight Solar for re-programming.
11. How much torque should I put in the battery screws?
There have been several types of screws used on our batteries and the torque varies with each. It is important to ensure that all fasteners are securely torqued to ensure a good connection. The unique terminal design does not require an excessively torqued fastener to obtain a good connection:
i Philips head M4 screws – 12 in-lb
ii Hex head 2.5mm M4 screws – 12 in-lb
iii Torx head T20 M4 screws – 30 in-lb
iv Hex head 4mm M6 screws (200Ah cells only)– 40 in-lb
This document was provided originally by Elite Power Solutions but has been modified by Starlight Solar Power Systems for RV applications.
Elite Power Solutions GBS Battery
Frequently Asked Questions