Battery charging amps
I am worried my batteries are not being charged properly and have been reading lots of posts on this site.
Being winter, my loads are much greater than summer and I am using my generator lots (short cloudy days also, so very little solar). My concern over the batteries comes from the generator running under an hour when it kicks on, and also can be starting every few hours. There is no way my battery bank should be charging that fast.
My 3 year old battery bank is 1520 ah. The XW6048 inverter is set to start the generator when the batteries reach 49.5V for 15 minutes. It is set to run the 3 stage charge, where it shuts off after reaching float. I have always had the system set to start charging at no less than 70 - 80% discharge. Other than a few times I had errors and the gen did not start up. 8 months of the year my solar is enough that the batteries never drop to the pre-set limit that the generator is set to turn on. I follow the manufacturer colt settings for the 3 stage charge. In other words, I have tried to take care of the battery bank.
These posts have me thnking Iam not charging at enough amps.
https://www.solar-electric.com/deep-cycle-battery-faq.html
https://forum.solar-electric.com/discussion/16348/48v-system-charge-settings
https://forum.solar-electric.com/discussion/14613/battery-system-voltages-and-equivalent-power
From these three posts; I think need to be charging my battery bank upwards of 1520 / 8 = 190 amps. This is not possible with what I have. The max charge rate on the XW 6048 is 100 amps. My generator has a max amps of 54 (108). The inverter shows around 100 amps when the generator kicks on to bulk charge at the max charge rate of 100%. I have two MPPT 60 150 solar charge controllers that I assume would allow for 120 amp charge rate if the 6 kW of panels can produce that.
The XW 6048 has so many safety features built into it that I can not charge my batteries at a high amp rate for a set period of time. The inverter moves from the bulk charge to absorb quickly on the state of my batteries now. So they only charge at 100 amps for a short time before moving to absorb, where the charge drops down to 30 amps, and then to float where the charge drops down to 10 amps. Ican adjust the voltage of the charge only.
Am I under charging my battery bank and wrecking my battery bank? Do I need to upgrade my system to allow a higher charge rate? I hope there is something I can do to save my expensive batteries.
Thanks.
Being winter, my loads are much greater than summer and I am using my generator lots (short cloudy days also, so very little solar). My concern over the batteries comes from the generator running under an hour when it kicks on, and also can be starting every few hours. There is no way my battery bank should be charging that fast.
My 3 year old battery bank is 1520 ah. The XW6048 inverter is set to start the generator when the batteries reach 49.5V for 15 minutes. It is set to run the 3 stage charge, where it shuts off after reaching float. I have always had the system set to start charging at no less than 70 - 80% discharge. Other than a few times I had errors and the gen did not start up. 8 months of the year my solar is enough that the batteries never drop to the pre-set limit that the generator is set to turn on. I follow the manufacturer colt settings for the 3 stage charge. In other words, I have tried to take care of the battery bank.
These posts have me thnking Iam not charging at enough amps.
https://www.solar-electric.com/deep-cycle-battery-faq.html
https://forum.solar-electric.com/discussion/16348/48v-system-charge-settings
https://forum.solar-electric.com/discussion/14613/battery-system-voltages-and-equivalent-power
From these three posts; I think need to be charging my battery bank upwards of 1520 / 8 = 190 amps. This is not possible with what I have. The max charge rate on the XW 6048 is 100 amps. My generator has a max amps of 54 (108). The inverter shows around 100 amps when the generator kicks on to bulk charge at the max charge rate of 100%. I have two MPPT 60 150 solar charge controllers that I assume would allow for 120 amp charge rate if the 6 kW of panels can produce that.
The XW 6048 has so many safety features built into it that I can not charge my batteries at a high amp rate for a set period of time. The inverter moves from the bulk charge to absorb quickly on the state of my batteries now. So they only charge at 100 amps for a short time before moving to absorb, where the charge drops down to 30 amps, and then to float where the charge drops down to 10 amps. Ican adjust the voltage of the charge only.
Am I under charging my battery bank and wrecking my battery bank? Do I need to upgrade my system to allow a higher charge rate? I hope there is something I can do to save my expensive batteries.
Thanks.
XW6048 inverter, EnerSys 1520 Ah battery bank, 1500 watt tracker & 7500 watt stationary solar, 10kw Baldor NG generator
Comments
Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor
21 SW280 panels on Schletter ground mount
48v Rolls 6CS 27P
2) With the Combox, SCP or Gateway, you program the battery size into the XW and it then "knows" how to properly charge that size of battery.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
I have set my battery type to custom and entered in the ah and factory charge settings. This was done in the inverter, charge controllers, and battery monitor.
One thing to consider is if the inverter charger is programed to reach float, the charge controllers will also transition to float, if the generator runs in the morning it could render the controllers useless for the rest of the day, unless the recharge value is programed higher than the defult of 50V, which is very close to the 49.5V generator restart value, which will repeat the cycle once float is reached, so essentially it would be a generator system rather than a solar system.
From observations when I had to use a generator, when the charge controllers can no longer compete with the inverter charger, they simply stop, their input, but it has been a while since I needed a generator.
Just a collection of thoughts which may help, naturally SG is the best way to establish SOC.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Also, where are the batteries located (eg cold shed)? Cold batteries can lose a fair bit of apparent capacity. A 1500ah bank might have an apparent capacity of more like 1000ah or less in freezing temps, for example. Properly maintained, the capacity comes back when it warms up, but while cold it behaves like a smaller bank. FWIW.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
http://support.rollsbattery.com/support/solutions/articles/5860-temperature-vs-capacity-flooded-lead-acid-batteries
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
My battery monitor does show around 90% (I'll watch it closer today) when the inverter is showing down around my 49.5 or 75%. I always thought that it was lying to me, and I should trust the reading on the inverter, but maybe not. It must be detecting the open circuit voltage only? Can you or someone explain this to me a bit more? The voltage reading on the monitor is usually with .3 or of the reading on the inverter display, but still says upwards of 90% charge when based on the chart it would be less.
When the generator starts the charge controllers stop charging. I assume to protect from over current to the batteries. When the gen stops they will begin again from a float charge. But I have observed that they will switch to bulk at end of day or if cloud cover comes up, putting the output less than the load.
A 0.3v difference between inverter and meter voltage seems high to me. Could small wire or loose connection be making the inverter see lower voltage and false starting genny? Does the difference get bigger with higher net charge/discharge current?
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Unless it's been a really long spell of gloomy weather, I only use the genny to bulk charge (~85% SOC), and let charge controllers do absorb to the extent possible with available pv current.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Is it possible to measure SG on a sealed battery?
Voltage is a poor method of determining SOC, it should only be considered a rough guide at best, there are differing values depending on electrolyte concentration and or manufacturer. Sadly with sealed cells it's practically impossible to measure SG, so voltage is about the only practical method other than a load test where the battery is discharged to a terminal voltage 10.5V.
With regards to differences in values of the battery monitor, the point of reference could play a part, if the monitor reads close to the battery with the inverter measuring internal voltage, there would be a voltage drop in the conductors feeding the inverter. This voltage drop will be dependent on load, as load increases so dose voltage drop, this is simple to measure by using a digital voltmeter, one probe on the inverter input the other on the battery terminal. Even the best meter will have tollerance +/- 5% for example, even 1% of 50V is 0.5V, temperature of the measuring equipment will offset readings to some degree.
The controllers don't shut down to protect themselves, they simply can't match the voltage and current supplied by the inverter charger. If the current is reduced to a value which matches the charge controllers, they will work together, most users only use bulk to mid absorption charging as charging to float is an inefficient use of fuel. The other problem is that as mentioned before, the charge controllers will remain in float until recharge voltage is met.
Perhaps adjustments to settings will solve the mystery, programming is simple so I would experiment with different settings keep records of how it performs then select the best, this could be a seasonal adjustment, every system is different. Winter is especially challenging in Northern BC, work would take me there to service HVAC equipment, near the coast was the worst Kittamat, Prince Rupert in particular, Ft. Nelson was colder but at least there is sun, where are you?
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
The night before last I set the system to start at 49.2. The SCP light was flashing at 7:30am with the low voltage. So the gen was going to be triggered to start soon.
This morning I checked around 7:30 am and see that I left the generator on manual off by mistake. The battery monitor was reading 48.9 volts, 91% charged, 22 hrs remaining to the 75% depth of discharge I have input. I had run the gen the previous morning, and only got a few hours of mixed cloud and sun during day.
Performing a load test is difficult with my setup and over the winter. If I can be confident that 49 to 49.2 is not actually 60 to 70% discharge then I'll probably set the system to start the generator around those values. Interesting that 49.5, just 0.3 volts more was triggering my gen to start every few hours, vs the 49.2 that was around 16 hrs from charge to triggering a start.
I don't mind running my generator in the winter. It is built to run, 1800rpm, and is relatively easy to service and maintain. The batteries are a different story. I got a much shortened life from my previous bank and am paranoid about my current bank to keep it safe. I didn't have the system I have now before.
I live 30 mins east of Fort St John, BC. Mid November through mid January are tough solar months. Fair bit of overcast mixed with short days.
With my second lead acid system 400Ah , which is very lightly used, mostly the inverter 18W with occasional 100W on demand pump, 12W led light and 4 hours refrigerator via transfer switch to relieve my main system of shading issues at this time of year. The daily minimum voltage connected, is constantly 24.8V which equates to 49.6V, on a clear day the controller is already in low current PWM by 8:30 in the morning even with refrigerator load. Since the actual SOC by loaded voltage is probably higher than apparent, reducing low battery setpoint slightly will prevent short cycle generator run, if that is a problem, from a noise standpoint, doubt it will have any effect on battery life expectancy, but I do understand paranoia after nearly loosing my first bank.
Fort. St. John is nice in the summer, did a canoe trip down the Peace river,10 days of beautiful scenery camping along the way, winters are not my thing however.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.