Jump to content


  • Content Count

  • Joined

  • Last visited

Recent Profile Visitors

1,210 profile views
  1. Looking at the data sheet it’s saying that Recommended is 37A but Max is 74A. So surely for the instance I’m explaining about 3x 74A = 222A which is even better! We’re talking about an event that happens 2-3 times per day for 3-4min.
  2. Hi @plonkster Thanks for this, but my main concern is the ability for Lithium-Ion batteries to handle Surge Currents in excess of their rated Maximum Discharge Currents. So with 2x US2500's connected in parallel this would provide 5.1kWh delivering a maximum 112A (continuous) or 224A (15-sec). So what happens during short term over current situations drawing say 7kVA of power which should be pulling 145A from the batteries for 3-4 minutes? How do the Pylontech's and similar Lithium-Ion batteries handle this? Do they trip or just keep push current like my flogged AGM's? Thanks, Trev
  3. Hello All, I am in the process of upgrading my battery bank from AGM to Lithium-Ion and when consulting the datasheets for each product I am mindful of the Maximum Discharge Current detailed by most of the Lithium-Ion batteries. For example, the Pylontech 2.4kWh battery (US2000) has a maximum discharge current of 50A (or 100A for 15-sec). This is in contrast to the Axpert MKII 5kVA Inverter which maximum discharge output at rated capacity of 5kVA is 104A. I was about to now state that according to the Axpert datasheet, the unit has the ability of withstanding 2 x rated capacity (i.e. 10kVA) for 10-min. I was quite certain of this feature as i recall it being one of the reasons for buying the unit in 2015 when I was comparing to other brands. But I have just downloaded an Axpert user manual to check myself and I see that it states 'Surge Capacity: 2x rated capacity for 5-sec' (a significant difference). Practically however, what I do know for certain which is a common daily occurrence is that the ladies in the household run the inverter up to 7-8kVA with some appliances (typically the kettle, microwave and too many lights etc) where the Axpert starts warning with beeps and a red flashing light. The observation is that it holds this out for the duration of the kettle being boiled which is typically 3-4 min. The inverter does not trip on overload protection so I'm thinking that my original specification of 2 x rated capacity for 10-min may have been valid unless i have bypassed this with my settings . Anyway, the question i wanted to ask about this common occurrence in my household with respect to the Lithium-Ion battery is: Q1: At 7-8kVA the Axpert would be drawing up to 167A for this period of time. How does this now work with the maximum discharge current specifications outlined by the Pylontech or any other battery for that matter? This has been my biggest procrastination point that has stalled me from moving ahead with this and i would like to get your expert input to this matter please? Please note that I have tried to browse and search for previous discussion on this topic. I do recollect a conversation on this in one post where someone (I recall either @Chris Hobson or @plonkster) was alerting everyone to the limited discharge current capacity of the Pylontech battery. Please excuse me if this is covered elsewhere. If it is, kindly point me to the informative post? Getting back to my current set-up and now pondering over the details of the Axpert datasheet, the reason for upgrading my batteries is because my bank (9.6kWh: 2 x 4x100Ah Renesola 6GFMJ-100 - see attached for ease of reference) no longer has the capacity to hold-out for the design duration of 4-hrs at 50% DOD. It was doing so in its early life and held out for an entire 11-hrs to 100% DOD on 2-3 occasions. Now, when entering load shedding, my charge capacity drops drastically and any heavy loads such as a microwave or kettle causes it to shutdown. Reading previous posts I thought it may be due to imbalance and a damaged cell so I tested my batteries which all checked okay according to the guidance provided in those posts, but for good measure i purchased and installed two HA02 Battery Balancers from @ChrisB along with a Victron BMS-712 which shows me trends on the App of the drastic roll off in charge capacity (Note: i'm behind on installing the midpoint cable for whatever reason at the time of installation so cannot confirm the BMS warnings... I know, this defeats the reason for getting it in the first place... Rand out of time...) Q2: Could the frequent (daily) demand surge at for extended durations of 3-4 min at a time have prematurely damaged or aged my Renesola AGM batteries? Consulting the Renesola data sheet, I note that the 'Constant Current' table has a 10h rating of ~10.3A per cell which should give ~120A for the 2x (4x100Ah) set-up. However, I also note that this table shows capacity ratings down to 15-min where it holds out at higher currents of 128-166A per cell implying a massive capability of delivering very high currents far exceeding the cable capacity and hence the need for inline fuses or fast tripping DC breakers at 125A etc... Q3: Given the fact that Lead Acid / AGM / Gel batteries are supplied without overload protection when compared with the Lithium-Ion packs that are supplied with all and sundry, can I deduce that unless you do not implement the necessary protection mechanisms, the hammering of my AGM batteries on a daily basis would have resulted in a general degeneration of the batteries faster than the specified 1000 cycles at 50% DOD? Hence the system is typically undersized for the connected loads to start with and it's probably advisable to parallel a second Axpert (which i have available) should i wish to maintain the current load profile? This talks to my first question about the need for 'matching' the maximum discharge current of the battery bank and the inverter. Could the AGM's have quietly taken he abuse at the cost of a shortened life span given their ability to deliver on high currents? When switching to Lithium-Ion, can I anticipate that the batteries will trip if i breach the maximum discharge specifications given the built in circuit breaker? Thank you, Trev Renesola 6GFMJ-100 TDS v3.pdf
  4. Hello @Cassie Lithium Ion is a the category name given to a number of Lithium based batteries with difference active materials. Namely: Lithium Iron Phosphate(LiFePO4) — LFP being most popular for its advantages but there are many more... While not an expert, I have done a lot of reading as i look to switch my system from AGM to a Lithium-Ion alternative. This is the best resource that i have found with a great comparative explanation between different types: https://batteryuniversity.com/learn/article/types_of_lithium_ion. I'm not sure how 'apmedoutdoors' got to their sales pitch on their website when i have seen a few of these Lithium-Ion derivatives on the market.
  5. Hello Buffy Welldone on this! I have been waiting for someone with your skills to take initiative on this. I installed a Wifibox last year and have enjoyed knowing when my inverter kicks in from a remote location which is only done via Email. A significant improvement to your App would be to send all warnings and errors via Notification on the iPhone. This way it brings it to your attention as opposed to being missed in an email inbox. Secondly, one warning that the system lacks is when power is restored! No email is sent to say MAINS_RESTORED... So the only way I am able to assess how long a power outage was for is by logging into power-datacenter.com and analyzing my data points which I set to sample every 30s. This would be a big up!!! I can suggest a few more but this would be great as you would be fixing something that the Wifibox does not do! Thanks again, Trevor
  6. Just remember @Dex that if you are measuring your current with a simple ammeter you are not considering the phase angle between the current and the voltage. That is what the efergy meter does without compensation. Therein lies the issue of power factor. It is not so much an accuracy issue as it is an 'applicability' issue... with a proper power meter we will be able to tell the severity of the the current lag/lead and therefore how 'applicable' the measured Amps are as a deduction of measuring Real Power. With zero lag/lead only then would the simple ammeter be applicable. I have come to terms with the fact that my efergy is not accurate enough to tally consumption but rather only accurate with regards to exactly when power is drawn and a thereafter an 'indication' of how much is being drawn.
  7. @Dex by the way, I intend conducting the same check using the readings (actual) provided by the municipality on my monthly account bill. I have to waiting for their bill because i don't have access to their locked metering board in my street. This would be the ultimate test as this meter is not only what i am billed with but also expected to be far better quality than even my simple DIN mounted power meter.
  8. Hello Dex, Funny you should ask because today I performed a small check to test the power factor theory. My new house main DB is fitted with a power meter. Nothing fancy, just a simple single phase instrument that displays totalised power consumption in kWh (http://www.rayleigh.com/media/uploads/RI-D36-80-P_V1.00.pdf). Assuming power factor is better catered for on the DB meter than my Efergy device I obtained the following: DB Meter: 105.5kWh over 115hrs (22.0kWh/day) - manual opening and closing readings Efergy Meter: 191.63kWh over 115hrs (40.0kWh/day) - using efergy hourly reporting tools over the exact same period The difference is 18.0kWh/day... If you divide this by 24hrs you get an 'error' (misreading) of 0.749kW which talks precisely to your 750W... This crudely confirmed to me that the Axpert is in fact pulling a highly inductive load resulting in a very poor power factor which the Efergy meter does not see due to its rudimentary means of metering. I have to concur with Chris that a tremendous amount of power is lost to heat generation. By observation, the surface and sides of the inverter are however cooler than my the 200W wall panel heater in my child's bedroom. Hence my assumption is that the unit is pulling a lot less than 200W of Real Power during no load / utility to load conditions. I'll see if i can arrange a Fluke Power meter with logging capability that we have at work... It would be really useful to have a power & pf vs time trend during load and no load conditions for the Axpert. Trev
  9. @gabriel the original query by DeepBass9 starts with the above quoted question... Calculators do not explain much, just like 'join the dots' or 'paint by numbers' for artists
  10. @DeepBass9 I'm sure you would like to use an equation, so here it is: Q = m x Cp x dT ------- (1) where: Q = Energy required to heat your 'substance' m = Mass that you are looking to heat dT = Final temp minus Initial Temp ( T2 - T1) then P = Q / t ------- (2) P = Power required to deliver or that you have in place to transfer the above calculated energy in a required or resulting time 't' t = time required for a given power base to deliver the required energy, or time required to reach a final temperature from an initial So: (2) ---> (1) P = [m x Cp x dT] / t And finally: t = [m x Cp x dT] / P Given: m = you have not defined a mass so I will use 100kg (100l) then you can simply multiply the calculated time by 2 for 200l, or 3 for 300l etc. Cp = water is 4.183kJ/kg.K (at 55C) dT = 30C as you have stipulated, so you could be starting at 25C and want to get to 55C but you have not stated your starting point which is irrelevant since you asked how long to raise the tempt by 30C (I.e. dT) P = 2kW heating element thus: t = [100 x 4183 x 30] / 2000 t = 6275s (1h44m) for every 100l --> Now that you have the final equation you can play around with different scenarios for size of geyser, heating element installed, temperature rise and amount of water!
  11. Thanks guys! You have jointly answered my question pertaining to the float charging of my batteries. I just need to figure out the high load shown on my efergy meter. Plonkster, point taken about the power factor! Although i cannot think of many inductive loads that would be responsible for a high amperage and this a skewed reading by the efergy which uses Amps (metered) x Voltage (constant preset) to display a 'real' power estimate. I am currently in the process of converting to LED throughout the house which started this weekend! Observations were however made prior to any LED lights at my new house as well as my old house with a similar installation presenting the same characteristics. Hence i was wondering if i got my settings wrongs somewhere for both installations? Just calculating quickly: Total Efergy Load: 680'W' (apparent power) with downstream Inverter load: 208W (real power). For a poor pf = 0.7 (say) the real power for the efergy would be ~475W which implies that my Axpert is drawing a quiescent load of 285W....??? The only systems that are not on the Inverter are: 1 x Geyser (solar powered with circulating pump), 5 x air conditioners (standby) and a tumble dryer (off). Could the aircons be drawing such high phantom loads? I guess during winter time they should be switched off at the CB's anyway...
  12. Well noticed! When the photo showing 208W on the Axpert was taken my efergy was reading 680W... So that is close to the 500W no load draw shown on the efergy throughout the night...
  13. Thanks Chris, So the fact that my efergy is reading an average of 520W during the night when everything is switched off (bar phantom loads and security lighting - 100W max.) should therefore be a concern right? The only device that is permanently on is the Axpert inverter. I would be happy to see my efergy read 42-44W. I currently have a bypass switch installed on my system that allows me to remove my Axpert should a technical fault arise without having to rewire the breakers. It is however damaged and will be replaced shortly (story for another day). When i get this changed i will test the loads that i am seeing with & without my inverter inline for absolute confirmation that it is responsible for the high no load draw. But before i get there i was just wondering if there was anything obvious that i was doing wrong with my settings?
  14. Hello all, This is my first post to this forum but i have been wanting to do so for quite some time... I am not sure whether to post my query under this particular thread or 'batteries'... My question pertains to the operation of the Axpert inverter with respect to charging the battery bank. My display continuously shows that while utility is available, I always am 'charging' my batteries and supplying power to the house simultaneously. What has led me to this is that I am concerned about the load drawn by the inverter while I have little to no load in the house. I am using an efery power meter on my mains incomer to monitor my household power usage (not to be 100% accurate but to identify areas to reduce usage). At night when all appliances are off the draw is 0.52kW which is very high even for the phantom loads by electronic appliances... As my efergy CT is installed on the main incomer it is also reading the quiescent load of the inverter itself. Hence my concern is now two fold: 1) I am constantly pulling an unnecessary load 2) I risk overcharging my batteries. I would expect that the inverter would monitor my battery bank to ensure that the batteries are fully charged and once this has been achieved then it will switch over to 'float mode'. i.e. I assume that no power will be directed to the batteries during float as they hold their charge... Then as the batteries gradually discharge while on standby, the inverter monitors the charge level to kick in at a predefined setting to once again top up their charge. During top up (bulk) I expect a high load draw but not during float... Please assist? 1 x RCT (Axpert) 5kVA MKS Inverter | 2 x 4 -12V100Ah Renesola Gel batteries (100 cycles @ 50%DOD) | No battery management | Using as back-up battery power. Looking to install 1.3kWp of solar panels shortly...


Contact Us - Power Forum South Africa

  • Create New...