The current 140 watt panel should have produced 3.88 amps at 36.1 volts when new. I only get a maximum of 7 amps of charge in full sun with a depleted 12 volt battery, and usually it’s closer to 5 amps. Going with the 7 amp figure, at 12 volts that’s only 84 watts of charge. That’s only 60% of the rated 140 watts for the panel. Some of that loss is due to the solar charge controller being only 92% efficient according to its specs, but that leaves 32% loss due to panel degradation (it was old when I got it). I think it’s time to start thinking of upgrading the charging system.
I would want to replace the 140 watt panel with another of the same dimensions, since I have a rack system permanently mounted on the roof that I don’t want to move. There is a Rich Solar 200 watt option that fits the bill, making 5.56 amps at 36 volts. (I will stick with a higher voltage panel since the wires connecting it are only 14 gauge which are fine at that voltage but a little undersized at 12 volts).
Epever makes a new Tracer 20 amp MPPT charge controller that is 97% efficient for a 200 watt panel, a big improvement over the older tech. It also has a temperature sensor that can be placed in the battery box for optimizing the charging rate depending on whether the batteries are hot or cold. This should extend the batteries’ lives. The controller is much more affordable than Victron (pretty much the gold standard) but gets good reviews. It also has a remote monitor that would be plug and play in the location where my current Tracer monitor fits.
In terms of order of operations, I would need to acquire the charge controller first since my current controller is maxed out at 130 watts (yup, it’s hooked to a 140 watt panel but it doesn’t make 140 watts anymore). With the upgraded controller I can then get a 200 watt panel. The new panel should provide 16.7 amps of charge assuming no inefficiency, so maybe 12 or so amps in the real world. That would about double my charging capacity on a clear day.
All of this research into charging options is also me thinking ahead to eventually upgrading to LiFePO4 batteries at some point in the future. The new Epever charge controller can be set up for lithium batteries and the temperature sensor can ensure that charging will cut out at freezing temperatures so as to not damage them. Lithium batteries are coming down in price and will be attainable by the next time my lead acid batteries need replacing (2025?). I like what I see with the EVE cells (3.2 volts X4 cells) and Daly BMS, as shown on YouTube by Will Prouse and by Dan from Freely Roaming. Dan even came up with a way to warm and cool his lithium battery so that it could be charged and used in winter (a real practical consideration where I live in Pennsylvania). The 280 amp hour EVE battery would have more than double the available amp hours of my 3 lead acid deep cycle batteries, at less than 1/3 of the weight. Here are the specifics:
https://www.youtube.com/watch?v=vrIpvu3rOPo
280 amp hours in lithium = 280 usable amp hours, or 3360 watt hours at 12 volts.
75 amp hours in one group 24 lead acid x 3 batteries = 225 amp hours or 2700 watt hours for my current system. But that = 112.5 usable amp hours or 1350 watt hours at 50% depth of discharge.
Lithium can store about 250% of the usable power that my current 3 battery system can in the space taken up by a single lead acid battery.
That’s a lot of juice. We could run our fridge, heater, electric blankets, and computers for a week without having to worry at all about power consumption.
It’s fun to dream.
