Long-Lasting RELiON Batteries Power Off-Grid Minnesota Cabin

Posted January 04, 2021

Not wanting to make the same mistake of attempting to rely on a third set of lead-acid batteries that would invariably fail them again, Cameron Rabe, a full-time electrical engineer by trade and a Schumann family-in-law, decided to invest time to research a longer-lasting and more reliable energy storage solution. The two primary issues Cameron sought to overcome through a new energy storage solution were:

  1. Shallow Depth of Discharge. The lead-acid batteries only allowed for a very shallow depth of discharge (DOD) of about 50%, which directly impacted overall usable battery capacity on a daily basis and also required frequent recharging by their generator.
  2. Inability to Remain in Partial State of Charge. Their lead-acid batteries always had to be fully recharged and then constantly topped off in order to avoid leaving them in partial states of charge (SOC), which can and did significantly reduce their lifespan. This in turn required they constantly run their noisy, costly fuel-dependent generator to continually keep the lead-acid batteries charged and topped off.

Issue 1: Shallow Depth of Discharge

The Schumann family was previously using eight Crown 6CRV390, 390 Amp-hour, 6V AGM VRLA lead-acid batteries, for a total of 48V and 18.72 kWh. However, while 18.72 kWh was the rated capacity for this battery bank, the actual usable capacity is far lower due to the much lower allowable depth of discharge for lead-acid batteries. So as to not damage the batteries, it is recommended that most lead-acid batteries not be discharged more than 50%. Therefore, while the rated capacity of this eight lead-acid battery Crown battery bank is 18.72 kWh, the actual usable capacity is about half of that, so just 9.36 kWh.

Cameron then compared these eight Crown batteries to just a single RELiON RB48V200, 9.6 kWh battery. He quickly discovered that because lithium batteries can be discharged much more deeply, often up to 100% more, this single RELiON battery, while having a lower-rated capacity than the eight lead-acid battery Crown battery system’s rated 18.72 kWh capacity, actually has a slightly higher usable capacity.

This would allow the Schumann family to obtain the same amount of usable energy on a daily basis from just one RELiON battery as from eight Crown lead-acid batteries.

Additionally, the datasheet for these Crown lead-acid batteries states: “Maintain a state of charge greater than 60% when operating batteries at temperatures below 32°F (0°C).” Therefore, in wintertime in northern Minnesota, the manufacturer requires these lead-acid batteries never be discharged more than 40%, which even further diminishes the usable capacity of this lead-acid battery bank to just 7.5 kWh.

Issue 2: Inability to Remain in Partial State of Charge

The second major issue the Schumann family sought to overcome was the need to constantly ensure that their Crown lead-acid batteries were never left in a partial state of charge (SOC), as this is often damaging to lead-acid batteries. The datasheet from the manufacturer of these batteries states that the “batteries must be fully recharged after the termination of duty cycle usage,” as “chronic under-charge or overcharge will shorten battery life.” For example, after being discharged down to 50%, the Schumanns would have to fully recharge the lead-acid battery bank to 100% state of charge in order to not have the batteries deteriorate.

The datasheet for these Crown lead-acid batteries also states: “freshening charge recommended for inventory at 75% SOC.” Therefore, in order to not damage the lead-acid battery bank, the Schumann family had to constantly keep the generator running in order to fully recharge, and then continually ‘top off’ the lead-acid battery bank. This meant that the generator kept coming back on every five minutes in order to provide additional charge for the batteries. According to Cameron, this defeated the purpose of having batteries since they were constantly having to keep their generator running.

“We really didn’t want to have to constantly worry about keeping the lead-acid batteries out of a partial state of charge,” Cameron said. “Obviously we paid the price for that in the end by having to purchase a brand new set of batteries after our first lead-acid bank failed on us after just four months.”

By comparison, the Schumann family came to learn that RELiON batteries could be charged and discharged as needed, with no requirements prohibiting partial states of charge. This appealed to them because they could simply put energy into RELiON batteries and take it out whenever they wanted, with no complicated or cumbersome restrictions to always monitor.

The Solution

After discovering that the RELiON batteries could easily overcome the two primary issues the Schumanns faced with their prior two lead-acid battery banks by allowing a much greater depth of discharge and allowing partial states of charge without issue, they decided to purchase one single, long-lasting RELiON RB48V200 battery for a total of 9.6 kWh. They easily replaced their lead-acid battery bank with this much lighter and more energy-dense RELiON battery and paired it with their generator and Magnum Energy MS4448PAE inverter/charger. This system also includes a Magnum Energy MEARC for advanced remote control, a battery monitoring kit, and a Magnum Energy Automatic Generator Start module. This robust energy storage system now reliably powers the cabin’s lights, water pump, outlets and fans in the summertime throughout the day.

“I am very happy to report that our RELiON system is working flawlessly and I firmly believe it has solved all of the woes we had with the lead-acid batteries!” Cameron exclaimed. “I compared a recent, full charge cycle to the first charge cycle after we first installed the RELiON system a year ago, and was astonished at how well they tracked each other, as I’m confident there is no battery degradation, unlike with our two prior lead acid battery banks that significantly deteriorated in a matter of months.” Explore the graphs below to see how closely the RELiON battery’s charge cycles mirror one another after a full year.

Now that the Schumanns can easily discharge their RELiON battery up to 100% before needing to recharge, as well as can leave the RELiON battery in partial SOC without any degradation of the battery, they can rest easy and fully focus on enjoying their time together in nature. “We never have to worry about partial SOC or a partial charge cycle, as we simply put current in when we want and take current out when we want,” Cameron said. “There’s absolutely no fuss, as it really is the optimal solution for us.”

In addition to the RELiON batteries resolving the depth of discharge and partial state of charge limitations of the prior lead-acid battery banks, they are also expected to last for many more years than the Crown batteries, which in turn saves the Schumanns precious funds by reducing the number of battery bank replacements. For example, in just an eight-month time span, the Schumanns spent more on replacing and installing two sets of (sixteen individual) Crown lead-acid batteries than they did on their RELiON system, which is warranted to last for many more years to come. “I wish I had discovered RELiON solutions after our first AGM bank died,” Cameron said. “It would have saved us a significant amount of money spent on two sets of AGM battery banks, saved all the extra wear and tear on the generator, and given us back two years of the pleasurable cabin experience your battery allows.”

The Schumanns have also already drastically reduced their generator use, which has resulted in them saving about 50% of the funds they previously had to spend to refuel their generator. “With our RELiON system, the generator turns on, charges at full current the entire time it is on, then shuts off, as there isn’t any wasted fuel and we also no longer have to spend all of that extra time listening to a generator running at idle load,” Cameron explained. “After charging the RELiON system with the generator, we have several days, sometimes a full week, worth of electricity and can now relax with much more peace and quiet.”

Now that the Schumanns have made the switch from lead-acid batteries to much more reliable, easy-to-use and longer-lasting RELiON energy storage solutions, they can truly relax in their cabin worry-free, all while saving crucial funds previously spent on diesel fuel.

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