I'd like to go solar with a couple of our battery-powered tools without a) charging the batteries with DC directly, as they're expensive batteries with their own fancy AC chargers, or b) spending money on other expensive solar batteries to power charging these expensive tool batteries.
More specifically, I have a tool shed I'd like to put solar panels on solely to charge the electric mower & weed whacker (two 7.5ah@56v/420wh EGO brand batteries), and a bike shed I'd like to do the same - charge three Bosch 500wh (36v) battery packs with solar on the bike shed. We drain all batteries to about half capacity once a week, so they have roughly similar requirements - generate about 1kwh per week, although more than that is better "just in case."
I can get used 250w, 30v panels locally for about $90, so I figure four of those should be enough per shed, but I'm new to solar. I live in Seattle, so I figure 1kw of solar capacity, when factoring in clouds, conversion losses, and other system losses, should be enough to get 1kw into the batteries over the course of a week in most conditions, but I could use a sanity check there. Since the panels are relatively cheap I figure it's a good place to spend money as opposed to solar battery capacity, which seems very expensive.
Speaking of batteries, that's my question. There's lots of advice on how to hook up a solar array to a big battery to run your fridge at night etc, but not so much for my use case.
Ideally I'd just charge the tool batteries straight off an inverter, without a solar battery, or use a small (and inexpensive) battery. But I have the intuition that I can't just do that with typical equipment - it's here where I start to get fuzzy... both the EGO tool charger and Bosch battery charger draw about 2a while charging (one a little less, one a little more). So take the Bosh charger, 120v @ 2.2a = 264w, and the internet says an inverter draws 1 amp to output 20w at 24v, so that would mean I'd need a 264/20=13.2amp battery? The cheapest decent-looking LIFEPO4 I can find would be four 12v 7ah Dakota batteries (two pairs in parallel would give 24v 14ah), which would run about $200, and it seems like that's just scraping by for the requirements.
- Would this work as I've imagined it? Surely I'm missing something.
- Any way to cut out the charge controller & battery middleman? I'm aware of microinverters, would it be better to use microinverters and a voltage regulator to get 120v without going through a charge controller?
Thanks for any input!