General Lipo questions
 

Ok totally new to these batteries and im trying to learn as much as I can so I dont nuke anything or mess up the cells. I generally like to be as kind to batteries as possible and go for maximum longievity because well, im a massive tight wad.

So when storing, what voltage and % charge should they be left at? How long is it acceptable to leave them fully charged? Is it ok to charge them the day/night before you want to use them? Or is that too long?

Again I always go for longievity over any possible performance benefits, I used to charge Nimh at 2 or 3 amps and never let the voltage get below 6.0v. So I guess im asking whats the kindest way to treat these things. Cheers!

Most chargers have a storage charge function that balances the cells at 7.6V (2 cell) I always charge at 1c or less as my cells are 5600mah and my charger only does 5A, I left my first lipo fully charged for 2 weeks between race days, it swelled that much the case split open and I couldn't get the drawer open on my poly butler!!! Welding gauntlets on and lobbed into a bucket of salty water in the middle of the garden for a week.
Now I get up early and stick a pack or 2 on charge before an event and storage charge them as they come out of the car

1C or less is the best for longevity. Don't store fully charged. If there's a week or so between racing, then leave them as they are after the last race. If longer, then as Beale says use the 'storage' option on your charger before storing somewhere that does not go below 5 deg C or above 30 deg C. If no storage options on your charger, discharge to about 3.4v per cell and then store.

It doesn't seem to matter if you charge the day before, but leaving cells fully charged is not helpful to a long life. For the best life, don't fully charge or discharge. Use the 'fast charge' feature on your charger. This goes to the full voltage, but doesn't squeeze in the last few drops. Cells are most susceptible to damage when fully charged or full (below 3.0v per cell) discharged. HTH :)

Cheers very helpful thanks!

Very good info indeed.

I'm thinking of going over to LiPo,however I don't race and it
can be months between drives of my car.

If I ran my car and then either left the battery as it came out of the car
or storage charged it would it be ok to then leave it for 6-12 months
before charging it to run again?

Why would you not want to race an RC car for 6 months? :)

If you are going to store for that long then charge to around 50% before putting into open circuit storage. Don't store them anywhere warm.

Cheers for that Neil.

BTW tho,what's open circuit storage?


Work and another costly winter hobby get in the way for around
6 months of the year.

I had a couple of 1S cells I carried around 'just in case' but didn't use for the better part of a year.

One is fine and was recently charged and raced on a club night. Apart from being a tad off on top speed due to its age, and technology having moved on, it was fine. The other one went flat - totally flat, as in 0v - and puffed up a bit during the same time period.

I would suggest that voltage on the stored cells is checked, and if it drops below 3.2v then a quick charge/discharge cycle would be in order. I've had the same problem with receiver packs - one went flat the other two didn't - so it seems to a be a bit of pot luck. A regular monthly check would avoid any problems during storage. Storage itself doesn't seem to do them any harm from a performance perspective. HTH :)

Open circuit = nothing plugged in to the lipo power sockets/leads

For me, if your not going to be using lipo's for a few months, sell them on. Then when your ready, buy some more.
Decent budget lipos can be had quite cheap and leaves you worry free when your not running them in that time. Then when your are back to running, you'll have fresh batteries again.

3.8/3.85 V per cell is storage, is that 60%. and now most lipo can now be charged at 2c:D

deleted by Max, hobbyist correct, brand name manufacturer, wrong.

12C... that's 84A... show me the charger...! For the now-average 6000 cell, 2C is 12A - show me the charger...!! :D Look at any thread here recommending chargers and the highest you can get out of most of them is around 7A-8A. Spend mega-bucks on an LRP and you only get 12A!

The reality is that the charge time isn't reduced that much. The longest part of the charge is the last bit at constant voltage. The more amps you charge at the quicker the cell reaches its max (4.2v/cell) and the longer it takes to top out to full charge.

It may be that if you fully discharge the cell and then re-charge it so it gets a bit of heat in it it will give a bit more punch, but the reality is that only full Mod in a TC or 12th will take more than 3500ma out of a cell. At that level, anything over 8A will get it to 4.2v/cell in a few minutes, and then it spends the rest of the time on CC phase very (very!) slowly getting to full charge.

1C up and down for best life and good performance - simples...! HTH :)

40amp biggest I can see

http://shop.cpdracing.co.uk/index.ph...oducts_id=1773


Racing star from shumacher 16 amps in its sleep
http://www.racing-cars.com/pp/Manufa...100078-01.html

deleted by Max, hobbyist correct, brand name manufacturer, wrong.

So, do get to this stage of technology I need to spend £300 on a charger and use a 3200mAh cell?!!! For that sort of money I could fuel the travel to all my National meetings, and not get fade at four minutes when I get there!! Lunacy... :wtf:

The balancing bit is not relevant - it is the time it takes in the CV stage that is the same irrespective of the charge rate or balancing stage.

Reality check - do any of the A Final drivers in any electric class do this. Er... that'd be a "no" then... :) Thanks for proving it can be done, and that doing it costs more than a season's worth of tyres, fuel or a new race car. 1C up an down - I rest my case!!! :D

apart from my link to the charger that does 16 amps is only £60 which will easily do your suggested 6000mah lipo at 2 c ;)

deleted by Max, hobbyist correct, brand name manufacturer, wrong.

Listen to Slow One and Mark Christopher. Do not charge at rates greater than 1C. Reasons for this...

(1) Safety. Most safety issues are when cells are being charged. Higher charge rates can lead to an unsafe condition.
(2) There is no practical reason to need to charge faster than 1C
(3) It saves money (current costs money)
(4) Cycle life is reduced at higher charge rates.

N

+1

There has been some recent discussion in this forum with regards LIPO safety and these guys have contributed to the threads with detailed insight into the science of LIPO batteries:thumbsup:

My LIPOs (Gens Ace 5000, 40c) can allegedly be charged at 5c - 25A!!. I will not however attempt this as 5A (1c) easily gets the charged between races and also for the reasons given by Neil.