ComplaintsforNature Power Products

• Initial Complaint

  05/10/2023

  Complaint Type:

  Product Issues

  Status:

  Answered

  More info

  I purchased six Nature Power **** **** **** ***** ****** one one Nature Power **** **** ********. Before purchasing the inverter (but after purchasing the solar panels) I called the Nature Power customer service phone number and I spoke to an employee who I now know to be one ********************. I explained to ****** that I wanted the inverter for a future solar project which would be including lithium ******* battery cells. ****** implied that the inverter would work for my needs. He never mentioned the inverter only working with *** Sealed Lead Acid batteries. After the call I did not feel like ****** had really listened to me, or like he had fully answered my questions but I proceeded to purchase the inverter based on his advice that it would meet my needs. Now several months later I called back to ask what size power storage system would be within reason for the inverter and panel system I had purchased. I again spoke to ******, this time however he told me that the inverter would only work with sealed lead acid batteries. After our call I again felt like ****** had not listened to me nor had he actually addressed my questions. I emailed Nature Power and tried to explain the situation hoping to speak to someone else, but again I got ******. He not only refused to take any accountability and he did not offer any type of resolution whatsoever. This went back and fourth maybe a half dozen emails or so until he stopped answering me all together. His tone becoming incrementally more and more condescending throughout the email chain. In addition to misleading me about the inverters capabilities, he also gave me information which was confusing and contradicted himself multiple times. He told me that the inverter WOULD in fact function with lithium cells, but only to 70%. Then he backpedaled and told me 30%. He refused to clarify and still refuses to communicate. He has held up my project and there is no information online and no one else at the company.

  Business response

  05/24/2023

  Dear ***** ** *********
  
  Thank you for taking the time to comment and follow up on your inverter question.  There seems to be some misinformation regarding this matter.  Our Power Inverter you purchased through a 3rd part is indeed suitable for ******* batteries.  The amount of battery storage you will be able to use is less about a percentage and more about the voltage of the system.  Usually, when it drops below ****, it will auto shut-down to protect the battery system.  The actual amount of battery you can use will vary per system and battery chemistry but should be at least 70% of their capacity before they may go into protective mode.  This is due to the characteristics of lithium versus lead acid.  
  
  Here is a more detailed answer by our lead Engineer.
  The battery deep of discharge DoD depends on the following events, whichever occurs first:
  The inverters under-voltage shutdown uvs (= LVD Low Voltage Disconnect)
  The under-voltage Cut-off by the protection /BMS (Battery Monitoring System) electronics inside most ******* batteries, which by the way, can disconnect the output of the battery for other reasons in addition to under-voltage, such as excessive discharging current, excessive charging current, over temperature, under temperature (freezing), etc.
  The battery voltage operating range of the inverter is between ****V to 15.5V corresponding to the E01 under-voltage shutdown uvs (= LVD Low Voltage Disconnect) error, and the E02 over-voltage shutdown ovs error thresholds respectively. Out of that range, the unit immediately stops supplying ** power and may turn off completely after a few seconds. This is done in an effort to avoid over-discharging the battery (or at least to delay it) and to protect the unit against over-voltage at its DC Input terminals.
  The under-voltage alarm *** E05 is triggered in advance of the E01 (i.e. at around 11V) without interrupting the supply of ** Output power, to let the user know that the uvs can be reached soon.
  Note: For more details about the voltage shutdowns, alarms, and their recoveries, please refer to the information after my signature below. All of them are prefixed and not settable.
   The following points have to do when the battery charging source is not available, or cannot supply the total average current of its DC loads (including the inverter in case of not using an external ** transfer switch to disconnect it and pass thru shore power, if any, to the ** loads), resulting in a net discharging condition and so voltage drop for the battery.
  Not all battery energy can or should be used on discharge; some reserve is almost always left behind on purpose after the equipment cuts off. This is to preserve some energy for housekeeping, for monitoring in the case of having an internal BMS /protection electronics, as well as to reduce battery stress and allow for some self-discharge if the battery is not immediately recharged.
  The Cut-off voltage threshold of the protection circuit inside most of the 12V nominal Lithium-ion batterie in the market,including the LiFePO4, is typically within the 10V to 11.6V range, suggesting using the battery to no less than 10.4V to 12V, representing about 5% to 25%State of Charge SoC left (equivalent to 95% and 75% Depth of Discharge DoDrespectively), and vary depending on the battery manufacturer. Those percentages are relative to the total full capacity in Ah of the battery bank.
  Precisely, the =****V uvs (= LVD) threshold of the inverter is quite low, favoring the full potential of the ******* battery cells. However, make sure to size the total capacity in Ah of the battery bank and to use the suggested gauge of the wires to the battery to avoid excessive voltage drops under heavy load conditions, which may result in nuisance triggering of the uvs well in advance of what should be.
  Note: For the proper wire gauge vs length, refer to the rows in the attached table corresponding to model #SW1220, the equivalent of NP # *****.
  
  Having said that, the scenarios are as follows :
  If the inverters  uvsthreshold at =****V is above the Cut-off one of the protection circuit inside the Lithium-ion battery, there should be no problem at all in using the inverter (--> the =****V threshold is still quite low).
   If the inverters  uvsthreshold at =****V is below the Cut-off one of the protection circuit inside the Lithium-ion battery, the latter (i.e., battery cut-off) will happen first. In this case, is the battery the one that determines the depth of discharge, not the inverter.
  This is not necessarily a problem,since most of the protection circuits inside the Lithium-ion batteries (preferably equal to or higher than 100Ah of total battery bank capacity) can do it systematically and at high current rates (i.e. at the 200A continuous maximum current the inverter draws from the battery when supplying its maximum 2000W of power) without compromising severely its service life.
  Then, the battery should wake up by keeping it at the nominal voltage from the charging source for a while (as happens in most Lithium-ion batteries with internal BMS protection).
  Ask the battery manufacturer. -->If that is a problem, refer to the following point c).
   If, and only if, according to the battery manufacturer the inverters uvs must happen first (sooner) that the Cut-off of the protection circuit inside the battery and at a higher threshold than its corresponding ****V, or if there is no Cut-Off protection circuit inside the Lithium-ion battery and the uvsmust be over ****V, the only solution would be installing an external programmable automatic Low Voltage Disconnect LVD device with the proper continuous and peak current ratings to feed all the DC loads from the battery, including the inverter.
  Please notice that this approach is also required despite having the proper uvs (=LVD) threshold in the inverter, when there are other DC loads connected to the same battery, not having that functionality or not meeting it.
  About the E05 warning and E01 shutdown messages in the 12V NP single inverters model # *****, *****, and 38215:
  The E05 (DC-input Low Voltage warning) is just a warning and the unit should continue working but beeping. It is triggered when the battery voltage* drops below 11V (but not less than ****V) to let the user know that it is getting low.
  Then, if the voltage continues dropping below ****V,the E01 (under-voltage shutdown) message would be triggered and the unit shut off.
  
  Note *: Those values correspond to the voltage measured directly on the DC-Input terminals of the unit, and not necessarily to the one on the battery terminals. They can be different (i.e. higher at the battery terminals) due to the voltage drop (resistance) through the DC wires and other devices in series with them (e.g. DC fuse & holder or DC breaker,battery selector switch, a possible shunt to measure the current for an external battery monitoring system, etc.), particularly under high current conditions
  
  Both the beeping warning (E05) and the shutdown (E01) triggering events, together with potential On/Off oscillations,normally do not have to do with the inverter itself but with external factors, in this case, the inverters DC-Input voltage. They do not mean that the unit is defective, and can occur eventually (sooner or later)while the battery is getting discharged, or when the voltage at the battery terminals drops due to heavy load.  
  
  The voltage dropping through the DC + and wires that feed the inverter, while it is supplying power to the loads, has to be considered. Using thinner and/or longer wires out of our recommendations will increase the voltage drop through them, triggering the under-voltage shutdown (uvs) events in advance of what should be when using thicker and shorter wires. Please check the DC wiring information after my signature below.
  However, please notice that the uvs can occur sooner or later while the battery is getting discharged. That is normal.
  
  Following are the voltage thresholds for the under-voltage E05 and E01 alarms and errors:
  
  E01 and E05 voltage thresholds in the 12V NP single inverters model # *****, *****, and 38215:
  The battery voltage level (right on the inverters DC terminals) has to be just below ****V to trigger the under-voltage-shutdown uvs (shown on the display as E01).
           DC Input Operating range:                                          ****V 15.5V (right on the DC terminals of the unit)
           Under-voltage E05 Alarm ***:                                       =11.0V
           Under-voltage E05 Alarm Recovery uvar:                 =11.2V (typically 11.3V) The *** hysteresis is: uvar *** = 11.3V 11V = 0.3V
           Under-voltage E01 Shutdown uvs:                              = ****V
           Under-voltage E01 Shutdown Recovery ****:         = 11.8V (typically 11.9V) The uvs hysteresis is: **** - uvs = 11.9V - ****V =1.4V
           Over-voltage E02 Shutdown ovs:                                 = 15.5V
           Over-voltage E02 Shutdown Recovery ovsr:            =15.0V The ovs hysteresis is: ovs ovsr = 15.5V 15V =0.5V
  
  Notes:
  a)       Allow 3 % of error to the voltage thresholds above
  b)       All the voltage thresholds must be measured right on the inverters DC terminals
  c)       The *** is just a warning. The unit continues working as normal except for the beeping activated
  d)       Once the *** is triggered, it shuts down itself (by stopping the beeping) after reaching its corresponding recovery (uvar) threshold, even if it happens beyond the 30 sec. period.
  e)       Once the uvs is triggered, it shuts down itself (by stopping the beeping and resuming operation) after reaching its corresponding recovery (uvar) threshold, as long as it happens within a 30 sec period just after the triggering of the uvs. Beyond that period, the unit completely shuts down itself and has to be manually turned on to restart.
  f)        The best and easiest way to test the thresholds above is by feeding the inverter with a variable DC power supply (with no ** loads at all).
  
  Once the under-voltage shutdown uvs is triggered,the unit shuts down its **-Output power and starts beeping and showing the corresponding E01 message on the display for about 30 sec.  
  If within that 30-sec period, the voltage rises over the under-voltage shutdown recovery ****, the unit returns to normal operation again, restoring the **-Output power. Otherwise, the unit will completely go off in a latched way, by stopping beeping and showing the E01 message. In that case, it has to be manually turned on by pushing its Power button, once the battery gets charged enough.
   The voltage threshold or the **** is a little higher than the one of the uvs (there is a hysteresis) in an effort to avoid On/Off oscillations on the **-Output power due to the voltage variations when the battery is under load condition or not*.
   Note when measuring the E01 voltage threshold: *: When the inverter shuts down its **-Output, the battery is not anymore under load condition, therefore, a rapid and little increment of its voltage would be expected, which in some cases, can reach the **** threshold and so restarting again, producing an On/Off oscillation for a while.
  The higher the battery bank capacity (size) and or its state of charge SoC, the lower its voltage variations under load and no-load conditions, and so the lower the chance for On/Off oscillations. In any case, those oscillations do not have to do with the unit itself but with the battery bank sizing and its SoC condition, in relation to the inverter ** power demanded by the **-loads and their runtime requirements.
  Therefore, when you want to check the E01 uvs threshold, make sure to measure the battery voltage right at the DC terminals of the unit and just before the E01 is triggered (you can keep measuring it continuously until the E01 is triggered, so to get the one just before that happens). Otherwise, you will get a wrong higher value than ****V which may be wrongly interpreted as a problem in the unit when it is not.
  I hope this detailed answer helps give you confidence that you purchased the correct system for your needs.  If you have any additional info needed, you can reach out to me directly at *********************************.
  
  Thank you,
  
  *******************
  President/CEO
  *********************************
  ***************************

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