Hi,


I'm building a small PV system to charge 18v tool lithium ion Ryobi battery packs (both 2AHr & 4Ahr). I have two possible Scenarios that I'm considering.


Back of the napkin I figure the PV array can supply something like 36Ahr (assuming a 5hr day)



Considering that the sole purpose is to charge the Li Batteries, my basic design assumption is that I'll need to charge 6 4AHr batteries on a daily basis or nominally 24Ahr (4Ahr x 6). If I assume an efficiency of say 90% for the chargers that would work out to be something like 27Ahr. Therefore:



In scenario #1 since I don't have an inverter that's a load of 27Ahr per day (75% of PV).



In scenario #2, based on 90% efficiency of the inverter the load goes to 30Ahr per day (83% of PV)



As this will have long periods of non use I intend to trickle charge while stored.



What size and type of battery should I be looking at? Do I even need a battery?


Please help.



Thanks!



I didn't find the right solution from the Internet.



References:

www.solarpaneltalk.com/forum/off-grid-solar/12v-solar-for-rv-or-camping-etc/355581-solar-charger-for-18v-tool-batteries

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