October 31, 20214 yr Now that we have been running solar assistant for 6 months ... its time to verify and tweek the settings. Bulk charger - 57.6 VDC Float voltage - 54 VDC Battery cutout - 46 VDC Load - 1.03 KW from monday - friday 900 watts on the weekend ... some of the computer screens and other stuff is off. Batteries - 105 amp/hr deep cycle - 4S 2P (I think that is the correct reference) 2 sets ... made up of 4 batteries connected in series to make 48 VDC. Total 210 amp/hr = 10.08 kwh We had this understanding that they would backup the power for around 10 hours (maybe when the load was on 100 watts) ... someone commented that they only lasted an hour ... real time data collection indicates 1hr 20 minutes ... the batteries are just over 3 years old. 2 months ago with a 200 watt less load ... recordings indicate from the point that the power switches off till the battery cutout ... 3hr 20min last week recordings indicated 1hr 30 min to cut off at 46 VDC As the power switches off ... the battery voltage drops from 54 to 50 VDC within a few seconds ... then there is a flat line for 1 hr 20 min ... then the drop to 46 VDC literally straight down. The inverter is used as a UPS for all the computer equipment ... TV screens ... servers etc. My thoughts ... sell the old batteries ... before they die ... lots of bass fisherman looking for a cheap 105 amp/hr for a bit of weekend fishing. Increase the capacity to 315 amp/hr = 15.12 kwh (knock off 50 maybe 60 % because the are flood lead acid) I know everyone is going to say WTF ... why dont you just get lithium. Personally I would agree and hoof the old RCT 5 KVA inverter out ... it cant run "online" only bypass switching when the power goes off ... I would prefer the unit is online to get cleaner power (pure sine wave) and stable voltage out the unit. Personally I would go Victron with lithium batteries ... considering the application and clean power required. The cost for me to replace the 8 batteries - R16K plus an additional 4 batteries - R24K So lets hear you suggestion and why. I would need to backup my proposal to the customer.
October 31, 20214 yr Author 1 x 5 kwh hubble battery cost R24k. Anyone have a real time chart showing the hubble with a 1 kw constant load ... so we can see the time and response to the load from the point the power switches off until the battery shuts down? The load on the inverter is slowing increasing over time.
October 31, 20214 yr Author People say the product has a 10/15 or 25 year warranty ... only 2 % of companies operating today will still be around in the next tens years that is a fact. My concern is my company is already 30 year and still going strong there is a good chance I am going to still be around in 10-20 years time ... so it becomes a challenge ... I suppose I could pull a Hilti on my customers and say sorry (lifetime warranty is limited to 10 years ... they no longer support any of my Hilti products older than 10 years ... from the date of manufacture ... some of my Hilti equipment was purchased less than 10 years ago .. no longer supported ) I have a lot of Hilti machines ... replacement value well over R100k.
November 1, 20214 yr On 2021/10/31 at 11:01 PM, isetech said: As the power switches off ... the battery voltage drops from 54 to 50 VDC within a few seconds ... That's normal, the battery is no longer being float charged. Though it would be better if the voltage only dropped to about 12.8 V x 4 = 51.2 V (assuming light loads). On 2021/10/31 at 11:01 PM, isetech said: Battery cutout - 46 VDC That's 11.5 V per nominally 12 V module. That's nearly dead flat. Lead acid doesn't like to do that more than a few times in their life. With frequent load shedding, this should be set to 48 V. That at least should not discharge the battery too far past 50% DOD. That means less run-time, while it lasts, but you will get more years of life. That's why lithium is so much better than lead acid when there is frequent load shedding. Lithium batteries can be discharged to about 80% DOD without affecting life unduly.
November 1, 20214 yr Author I have a constant load between 950 (Weekend)and 1100watt (weekday) ... should I increase the float voltage to 55 VDC ? Looking at the curve displayed on the charts ... I have just adjusted the cut out voltage to 48 VDC (benefits of having remote access)
November 1, 20214 yr Author @Coulomb ... if you look at the attached chart in battery curve ... you are spot on ... once the voltage reaches 48 VDC ... it cuts out within a few minutes.
November 2, 20214 yr 19 hours ago, isetech said: I have a constant load ... should I increase the float voltage to 55 VDC ? I don't see any advantage with that. It just brings you closer to the gassing voltage (14.4 V per 12 V module at 25°C, lower at higher temperatures), and you don't want to be gassing sealed battery modules.
November 14, 20214 yr Author I downloaded a chart for lead acid 48 volt batteries SOC. That explains the drop to 50 volts 100% - 50.92 90% - 50.48 80% - 50.00 70% - 49.48 You start to understand what they talk about with the C rating of the battery 20 discharge @5 amps and the effect of the fast discharge rate at higher rates like in my case ... on one particular site the discharge current is around 25 amps and higher ... suddenly you throw all calculations out the window. Like those little 7 amp/hr gate and alarm batteries ... when we test them ... after a full charge ... if the battery is below 12.5 VDC as you disconnect it ... there is a good chance it is past its sell by date ... they gets stripped for the lead.
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