How to KILL your batteries

This is from Midnite Solar's Classic charge controller manual, pages 7 and 8, which is at

In the tips, "Strings mean either batteries or PV panels wired in series.  If you have a 12V system with 4x 12V batts, then the batts will be wired in parallel … you will have 4 strings of batts.  If you have a 12V system with 2V batts, thus 6 batts in total, then the 6 batts will be wired in series (6 x 2V = 12V) and you will have one string of batts."


If you have questions, doubts or additional tips, come to the hall Sunday from 1 til 3.


How to KILL Your Batteries

Batteries are delicate and require proper attention especially when off-grid. Think of your batteries and solar equipment as a small nuclear power plant, hydro dam, or natural gas-fired power plant.
Just like any of those, your system needs DAILY attention to ensure it is performing correctly and safely. For Lithium battery banks we highly recommend using the Logic input on the Classic which allows the BMS to tell the Classic to stop charging if the BMS detects an issue brewing. We also recommend the use of an independent battery monitor/alarm if you have an expensive battery bank. Below is a list of some of the most common ways we have seen people kill their battery bank.

❖ Not watching the charge voltages or verifying you are charging to the voltage supplied by the battery manufacturer.
❖ Not verifying the temperature compensation neutral point (typically 25° C) and the milli volts per degree C per cell (typically -5mV).
❖ Not watching to verify the Absorb or EQ time is set properly and that the equipment actually charges for that period of time. Some equipment will have settings like “End Amps” that can terminate Absorb early and if set up wrong can damage a battery.
❖ Not having enough charge current (Solar Panels) to properly charge the size of the battery you have. Consult the battery manufacturer for the minimum charge current.
❖ Using tap water or other liquids instead of distilled water in a flooded battery. The minerals in the tap water will destroy a battery.
❖ Failing to keep all connections clean.
❖ Not using ALL EQUAL LENGTH interconnect cables on each string. It is important that ALL strings be wired EXACTLY the same. Any variance in resistance on one string versus another
will cause an imbalance and the batteries will be dead in less than 6 months.
❖ Using more than three parallel strings and not using common bus bars. When you use more than three strings it is very hard to properly charge the middle strings. The only safe way to do this is to wire each string with equal length cables to a common bus bar.
❖ Not making sure your lead acid batteries get a full charge at least once a week.
❖ Routinely using more than 50% of the capacity of the lead acid battery. Using more than half the battery capacity drastically shortens the batteries life; occasionally is fine but on a daily
basis will kill them in months.
❖ Not leaving ample space between cells for cooling. We recommend at least one inch between the cells for cooling. Ask the battery manufacturer what they recommend.

❖ Trusting a State of Charge (SOC) meter, which can lose calibration over time and give you false readings. You need to verify specific gravity and or verify the charge voltage is being
met. Never fully rely on the SOC %; it is just a good, quick reference.



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