As far as Mono vs Poly goes, in theory the mono’s are slightly more efficient, but in practice I seriously doubt you’d ever notice a difference, therefore I’d go with the best cost…Solar nowadays can be had on ebay for less than a buck a watt (vs mine at over $5.00 per 10 yrs ago!!)…
Over the last few months I’ve had a chance to gain a fairly decent hands-on working knowledge with a single 100a LiFePo4, running an air conditioner (via inverter) and recharging via 400w solar and a basic PWM controller…
The only downside to Li (besides the initial cost!!) is that they cannot be recharged below 32df (say, when mounted in an outside compartment), yet will continue to provide a discharge down to just below zero df…
The big advantages are, less than half the weight of the equivalent wet-cell,
the voltage remains nearly constant throughout the entire discharge, the harvest-charge recovery rate appears to be at least twice as fast (in my estimation – using just a PWM controller) than with a chemically sluggish wet-cell (great during off-season solar harvesting!), and Li is reported to have about 10 times the available life cycling as does the wet-cell (4-5k cycles vs about 300)…
In my opinion, IF limited to only one battery (due to space limitations) I would definitely go with one Li in order to benefit from more available amp hrs capacity over whats only about 50% ‘usable capacity’ that only one wet-cell will offer…
If you decide on Li, you’ll need to configure your converter-charger and charge controller (if adjustable??…) for a Bulk output at somewhere between 14.4v – 14.6v, and Equalization modes (if present) must be disabled…In many cases (depending on charger specs) Bulk voltages will often fall within this range, while Absorption setting (usually around 13.6v) is not needed but if present will not harm the battery…
If you add another panel (or more) you’ll want to allow for about 10% additional ‘head room’ controller ampacity, and ‘may’ want to upsize the wiring as well to accommodate…As I previously stated, a PWM controller will do fine (due to the uber high receptivity rate of Li), yet a slightly costlier MPPT controller can do even better (gaining roughly 25% or so additional panel efficiency).
Good Luck,
Phil
