Stinj

Re-entering the hobby and reading up. I've read a lot of (contradictory) posts on lipo charging.

What I'm intending to do is: metal ammo box (drill holes and take out seal for venting) + individual lipo bags per battery inside the box. (still undecided if I'll go for the inexpensive chinese bags or some branded options, though when I look at the branded ones, some seem very similar so you never quite know what you're getting. I live in Europe so cannot get my hands on the original lipo sack's that I've heard about and since I'll be buying 6 bags, budget comes into play..
As I'll be racing 1/12 (1S) and F1 (2S shorty) and not heavier batteries, I hope this set-up will be ok.
Am I right in assuming that the 'fire power' goes up the higher number of cells? Or does it have more to do with the mah?

Just need to figure out a place to put it as I don't have a garage and the floors are wooden. I do have a basement with nothing in it, but it's damp...
Also read something about placing the set-up on drywall?

Some lipo batteries came with the used kits that I bought. Already tossed out 2 of them (one 2S had a dead cell, one 1S was at 3.18V with 27m ohm and I didn't want to risk it. What's actually a good IR number to stay under?).
I bought a skyrc b6ac v2 for charging.
Stijn

urnotevenwrg2

iTrader: (1)

1 milliohm per cell is a good IR number. As for the ammo box and lipo bags, that is completely unnecessary. Lipo fires happen when you do something stupid. I have been using lipos for 12+ years and have never had a problem. Don't over charge or over discharge them and you won't have a problem. In that 12+ years I have seen two lipo fires. Both fires were right when a lot of people first started switching to lipos, and were still running NiMH batteries too. They either charged the lipos in the wrong mode because they were going back and forth between the two battery types, or they had turned off low voltage protection, and ran the battery down too low.

Do you have a cell phone, a laptop, tablet, smart watch, or any battery powered tools? If so, you already deal with lipos every day.

Kelseyrc

iTrader: (7)

The more cells in a battery the higher the voltage and thus your rpms will be higher. But, in general, for 1/10 scale racing you'll be using 2s packs and for 1/12 scale it'll be 1s. I charge my batteries in a Lipo sack and and usually not higher than 2c charge rate unless I'm in a huge hurry. If you charge at 1c it'll be the safest. As long as you don't over discharge your packs (<3.0v per cell) or overcharge (>4.2 or 4.35v per cell depending if they're lipo or lihv) your batteries should last at least a few hundred cycles. I set the low voltage cutoff on my esc to 3.4v per cell to be on the safe side. The reason for that is that if the cells don't discharge evenly and your LVC is set to 3.0v per cell you could still over discharge your pack since it looks at the total voltage so one cell could be at 2.8v and the other could be at 3.2v and your esc won't know any different.

Also, do not leave your battery stored at full charge! Always store your batteries at around 3.85v per cell. Lipos don't like to hold full charge for an extended period of time.

Stinj

1 milliohm? Ok, that's not a lot. The other cells are all between 4 and 9, figured that below 10 was fine. They are used packs so don't really know the history. I'll keep an eye on them when charging a few times.

So you don't even charge/keep the batteries in a bag?

Stinj

@Kelseyrc the ones I've kept are all at around 3.80V per cell.

Was wondering how I will be able to tell when to stop driving. Will take a look at the esc for voltage cut off settings. Hope I can do it without a program card of some sort. One's a used Cirtix stock club race, the other's a used trackstar.

Kelseyrc

iTrader: (7)

Although I'm not familiar with either one of those esc's, most modern lipo escs have a LVC built in as a safety feature. I would just try to find the manuals for the ones you've got and see what they are set at. They usually are factory set at around 3.2v and if so that should be good enough to use without splurging on a program box.

As far as IR is concerned I would say that 1 milliohm is a number for a pack that is in great racing shape and I would be concerned when the IR reached 8-10 per cell. That being said, IR is a tricky metric because the IR rating is dependent on the temperature of the cells as well as the mAh rating and what charge rate you are using.

For example, if you were to charge your packs at 40 amps the IR would be lower than if you charged at 1c because you are increasing the internal temperature of your cells. However, this will shorten the life of your batteries as well as increase the chance of at least puffing the lipo and in extreme cases cause a fire.

So, I would say that you should take a baseline reading for the IR of that specific pack and have a normal charging routine and when the IR increases dramatically that's when you know your pack is ready to be retired. But at least for me, it's pretty evident when a pack is old and not working properly.

Hopefully that all makes sense.

urnotevenwrg2

iTrader: (1)

Yeah, for used packs those are good. You should be fine, just keep an eye on them.

Another thing is different charge setups will read differently, so your best bet is to just keep track of your batteries. With battery age, the capacity goes down and the IR goes up. Eventually you can get some new packs, and track them from the beginning of their cycles.

eR1c

iTrader: (2)

+1

I'll add, if your battery is puffed that is usually a sign to think about throwing it out (actually you can safely destroy it by piercing it while submerged in salt water).

rcbuggy88

Our track has a green bucket filled with sand for dead batteries. Throw away any puffing batteries.

Use a lipo bag when possible. The chances are quite slim, but if you are the unlucky one whose batteries catches fire, your entire pit area will burn and melt. I've seen it happen to someone who knew what they were doing. The chances are probably 1/10000000 every time you charge, but it is good to be careful. Ammo boxes should work, you either don't need holes or drill small holes. If possible, put some sort of filter over the holes just to be safe (or give yourself a feeling of safety).

When racing, IR should be as low as possible and everyone has their personal requirements on when to call a battery dead.