My battery box continues to be a work in progress. Much needed Power Pole connectors still to be wired in. With calculated, measured, and actual continuous use power needs at or near 120watts I needed at least a 100Ah (nominal 1200 watt hour) battery. The 10amp power draw arises when operating totally on battery in full UHD EAA viewing mode. The 32" 4k monitor (via fiber optic HDMI connection) and supplemental 2-in-1 tablet add to the basic set up drain on the battery. Fortunately I do not have to operate this way all the time where some dark sky sites allow supplemental AC power for the viewing station, and off-grid only at the scope.
In idle mode with the J5005 powered NUC PC turned on the daily (24hr) power use is 80-110wh. Since the USB travel router is also on set to max power output, the local network connection and Remote Desktop connection are on there may be some power use there causing variation. I turn off the CEM120 mount as it idles with motors 'running', to avoid excess wear. The NUC PC is powered by a 'boost' converter which steps up '12v' to 19vDC which adds to the daily battery drain. The NUC spec says 12v to 19v DC operation though.
One feature of the Victron MPPT solar charge controller is a measure of battery voltage to the millivolt. Being a load control (and sense) unit it measures current drain on the battery to 10ths of an amp, as well as watt-hours consumed and put back. The logging feature tells me how hard I have worked the AGM (lead acid) battery. This off-grid season new moon sessions draw between 350-500+ watt hours because I can power the viewing station on AC.
For my heavy use nominal 10A (120w) load and anticipated 8 hour on time I would put the 100Ah battery into 'distress' level. Pulling 80% from the battery regularly would decrease it's cycle life substantially down to about 500 cycles. I consider myself lucky to string 4 of these heavy use view sessions each new moon. So 12 months of that (unrealistic) puts only 50 hard use cycles on the battery a year. The 'idle' cycle is in this battery's '6000+' cycle range, while this summer typical 250-400+ watt hour use cycle life is '4000+'. Of course all this depends on how well and soon the battery is recharged, or allowed to sit idle in self discharge.
This years ~3 months nearly continuous operation has put another 90+ cycles on the battery box. I need to change out the end plug (smaller) of the AC 12 gauge extension power cord I use to connect 200watts of 36v solar. This will let it pass through the access hole (cut into one of the 'feet') and I will be able to shut the lid of the wheeled Pelican case and keep the spiders out. A 10 amp temperature compensated three stage AC charger and 100w pure sine wave inverter are in box as well.
Yes the AGM battery box is pushing 100 pounds all in. Yes a 'lithium' battery would be much lighter. Yes the AGM battery is 1/3 the initial cost of a 100AH LifePo with BMS. Yes the AGM operating/charging range is much broader (with reduced capacity) and without supplemental heating and associated increase in capacity to supply it. Yes the LifePo energy density is greater. In time I'll re-**** my needs and costs involved with an upgrade.
