Newbie Battery Questions

[The Inner Geek]

I did some searching around and found a lot of answers, but a couple are still eluding me so any assistance would be appreciated.

First off, I just got into the hobby after lurking around for a year or so. I made a big fat order from the FliteTest store that included two of these batteries;
https://store.flitetest.com/800mah-3s-20c-lipo-battery/

And this charger;
https://store.flitetest.com/imax-x150ad-ac-dc-charger/

The batteries are 800mah but when I charged them each only went to about 331mah when the charge was complete. What I do not know and cannot find in the charger documentation is whether it is showing the the amount of mah it added or a total of what is in the battery? For reference, the batteries started with 3.8v per cell and charged up to about 4.2v per cell if I remember correctly. So, was the battery 'half full of mah' when I started so it only needed 330ish more to be full?

Also, I've not done any kind of RC since the ancient times of NiCad and beginnings of NiMh batteries. I knew LiPo's were temperamental, but whilst looking for the answer to the above question on my own I've read a lot more about them. Do I need a bomb shelter to store them in?

I just finished my Tiny Trainer and got the Tx all set up and ready to go yesterday so I charged up the above two batteries. Then the rain started so I didn't get to crash... I mean maiden it. Are these batteries ok to sit charged for a day or two? Is correct etiquette to 'storage charge' them as soon as possible? I've got them in my garage in a LiPo bag right now... will my garage still be there when I get home this afternoon?

I'm trying to balance good sense with concern, but I'm a worrier by nature.

 

[ViperTech]

New batteries come with about 1/2 charge in them typically so a 331 mha charge would be correct. Most chargers show how much they put into the battery.

Well not a bomb shelter, I just keep mine out in the garage on a metal table, everybody has an opinion on what to do with them.

yep they are fine for several days in fact I have mine at full charge most of the time and have had no issues.

I have had no batteries explode or catch fire even in extreme crashes or after being stuck in a tree for 3 weeks I was able to recharge that battery by starting the charge as a nicad at low amp until it reaches 3 volts then balanced it and it works fine a little puffy but no issue.

Just use common sense with the batteries don't have bare wires exposed because that would be a problem and all will be well.

 

[dayve]

The charger is only telling you the mAh it has put in during the current charging session. It knows the battery voltage, but it doesn't know the capacity(e.g. 800mAh vs. 5000mAh), so it can't really tell you how many mAh are already in there, only how many it has put in.

I use a metal bucket to store my batteries in. I currently only have two, so it's not a huge deal that they're in the bucket together. If I had dozens, I'd come up with a better storage technique. I just keep the bucket where there's nothing flammable for several feet above it. Although LiPo packs certainly deserve respect and proper care, they *usually* don't catastrophically fail. I just think of all the people out there who don't know any better that run their buggies/quads/planes until they won't go any more (running the pack totally flat), charge the pack at the max rate their charger can supply so they can get back to playing as soon as possible, then do it all over. There should be a lot more burnt down houses if every pack that was abused burst into flames. That said, absolutely treat your packs well and store them appropriately.

I'm no battery expert, but it seems like most people will agree that leaving them fully charged for a day or two isn't the end of the world. That charger has a function to bring a pack back down to storage charge if you're super concerned about it, or if it turn out you won't be using it for a while.

 

[The Inner Geek]

Thanks for the quick replies guys. I feel a lot better about my battery situation already.

That said, I like the metal bucket idea. I'll have to grab one for that purpose.

Now I just need the weather not to be windy or rainy and nice out like it was yesterday for just long enough to charge two batteries. Really being realistic, I only need it to be nice out for a minute or two... I can't imagine my first flight will take much longer than that to end abruptly!

 

[French]

A bag of play sand from Home Depot or Lowes next to the metal bucket would be one of the best ways to extinguish a fire if it did occur.

Personally, I like the fire proof bags. Although I probably load each of them up with too many mAhs. I'm ok letting charged batteries sit for a week (no particular reason other than I like to have some ready). If I don't have a chance to use over a day or two, I'll try and cycle them to storage voltage (11.4V) then back up to full if I can.