Q1) after draining a lipo battery to around 3.3v how long can i safely keep it at that level?

Q2) what is the maximum safe time i can store a fully charged lipo before it needs to be used?

i have 2 lipo batteries for a speaker trailer and until their first charge and use they are being stored at 3.85v. i have done some google research and i think for the most part i understand how to safely use, charge and store them. They won't be used very often, perhaps 5 times a year on average.
1) i have purchased low voltage alarms so that i will know when to switch everything off however i will in most cases be using the speakers out in parks and fields at least 30mins to an hours ride away from a power socket so would it be safe for the batteries to sit at such a low voltage for around an hour before i can get them on the charger again? 
2) previously i used SLA batteries and was able to charge them safely overnight before an event while i slept but according to everything i've read about lipo charging i have to keep a close eye on them while they charge so i would prefer to charge them during the day prior to an event, however i'm concerned that several hours 'storage' at full charge might be asking too much...

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seandogue4 months ago

cold storage for lipos is, afaik un-charged, unlike lead-acid, which should be stored fully charged. Google it

ambientvoid (author)  seandogue4 months ago

oh im aware that they shouldn't be left fully charged long term but i'm trying to find out the maximum time before using them that i can charge them up. every event i've taken the speakers to previously has been so far away that i haven't had time in the morning to charge batteries immediately before departing for an event, so i've always charged batteries up to 24 hours early but if i can't do that with lipo i need to know so i can plan around it...

Cheaper ones seem to drain pretty fast. I have a pair of 1000Ahr thingies that charge up easily but if left idle after charging for a day or two will drain to un-usability due to leakage. Fool me once, etc. Can't speak for the 10Ahr blocks that have become popular recently in some markets like astronomy...

I like downunders' idea of using a solar panel so you're sure they'll be up to snuff when needed.

ambientvoid (author)  seandogue4 months ago

these ones are both 10000mah 4s blocks. i kinda like the idea of adding a solar panel, i considered it for the SLA powered battery speakers but those speakers were half the size of the new ones and the resulting 7 hour run time was more than i ever needed. i think the lipo's might need some help but i assumed with their delicate charging issues a solar boost might cause problems...

Downunder35m4 months ago

No problem keeping them empty for a while.
Best option to charge them would be to get a smart charger.
These change the charging modes and once full only use a trickle charge to keep the battery fresh.
Some of these chargers are also capable of "storing" your batteries, meaning you leave them connected until you use them, no matter when that will be.
Depending on budget and trailer size you could consider a foldable solar panel to keep the charge up on a sunny day.

ambientvoid (author)  Downunder35m4 months ago

i'm not sure what a smart charger is, i have a 250w 10a Turnigy Reaktor balance charger/discharger that i bought at the same time as the batteries though. it appears to have a storage mode and all sorts of other functionality which is totally lost on me haha (i really need an 'idiots guide' version of the instruction manual). does the balance charging mode do a full charge followed by a trickle automatically? will it alternatively cut off the charge completely once the battery is full?

If set correctly the charger should charge the battery at full rate until getting close to being properly charged, then it will reduce the current/voltage to avoid overcharging and damage.
Once full the charger should just get active in tiny intervals to keep the battery topped up and prevent self drainage.
But I don't know the specifics yof your charger...