Charging Lipos

[bsodmike]

Hi all,

I've got an older battery charger - it's got an LCD readout etc. and allows saving of battery profiles. That said, I've never 'balance' charged lipos before.

AFAIK, there is no 'balance' port - leaving the balancing aspect aside, on to basics.

The batteries I'm running are Turnigy 4000mAh 2S 40C Lipo Pack and come with a balance lead.

I'll be running two in a 4S configuration, i.e. in series. If I ignore the aspect of balancing these and simply charge as usual, say at around 0.8A through the balance plug - should I charge both packs in parallel?

I've also got a JST-XH Parallel Balance Lead 2S 250mm (2xJST-XH) - I'll essentially be wiring the positive/negative terminals to my charger leaving out the 'sense' line. Thoughts?

How would I go about balance charging as well, without having to buy a whole new charger? I'll post details of my current charger shortly. Thanks in advance for helping a newcomer with the nuances of lipo charging...!

 

[bsodmike]

According to this thread:
http://www.rcgroups.com/forums/showthread.php?t=1570042

It seems that charging via the balance lead is possible, although slow due to charging at say < ~2A.
I wonder if it's worth making a 5.5mm bullet connector harness ending with 4 mm banana plugs to connect to my charger and charge via the discharge leads instead. Thoughts?

Q1. Should I charge my 2x 2S packs in series, i.e. as 4S or in parallel as 2x 2S? Any caveats I need to be aware of?

Thanks!

 

[frickenjoey]

If your charger can charge Lipos but not balance you need an external balancer. I have one for my ICE charger kinda like this one. I will go with a batter charger one of these days but as long as the old ICE keeps plugging along I will use it.

---------- Post added at 4:02 PM ---------- Previous post was at 3:59 PM ----------

According to this thread:
Q1. Should I charge my 2x 2S packs in series, i.e. as 4S or in parallel as 2x 2S? Any caveats I need to be aware of?

Thanks!

Do not charge in series!!! Yes the problem is risk of overcharging one pack and FIRE. Charge one at a time only with a charger that has a Lipo setting and get an external balancer or a new charger. DO NOT charge in series, very dangerous!

 

[bsodmike]

Can't I get away without a balancer?

Do not charge in series!!! Yes the problem is risk of overcharging one pack and FIRE. Charge one at a time only with a charger that has a Lipo setting and get an external balancer or a new charger. DO NOT charge in series, very dangerous!

Got it, thanks

 

[frickenjoey]

You can for a little while but the cells will get out of balance and start to puff then it is time to get a new pack.....or again run the risk of over charging or discharging a cell or entire pack and you have the fire risk yet once again. Cell matching in Lipo is infinitely more important than it was in the NiMh and Nicad days. Once you replace a couple packs it would have been cheaper to get a balancer.

 

[bsodmike]

You can for a little while but the cells will get out of balance and start to puff...

...and by 'puff' you mean bloat up?

I had my radio in storage and the Lipo was in the box as well - it was well bloated, a 11.1V 3S radio lipo. I never did any balancing on them before... that explains it! :whhooo:

 

[frickenjoey]

Yes bloated = puffed. That means the battery is doing it's death march. you can run them in very low draw functions for a little bit but you have to be very wary. Still not a good idea. I use a couple puffed 2s packs for a roto start and it is ok. But it is still a risk. If they are going to sit for a couple months it is best to put a storage charge on them. Most newer chargers have this function. i just lost a 3s pack for my crawler since I didn't do it after not running for a few months. Pack puffed, showed low voltage on the chrger which means garbage time.

 

[bsodmike]

Gotcha. I just ordered this balancer:
http://www.amainhobbies.com/product...-Planes-Electrifly-Equinox-Lipo-Cell-Balancer

 

[frickenjoey]

Good deal, better safe than sorry man. I ruined a couple packs when I first got into Lipo. I just got home and looked and this is the one I have by Hyperion

 

[ksrichard]

I try to balance my lipos at least every other charge. It wont hurt to balance it every charge. I have an
Astro blinky. Seems to do its job. Be sure to properly dispose of your puffed lipos. Put enough water in a bucket to submerce the battery. Then add salt until no more will disolve. Soak it for a couple days.then toss it.

 

[Greywolf74]

Astro blinky is a great little balancer. I still have mine and my ICE charger although I've since retired them from use.

 

[bsodmike]

I want to thank everyone for your advice and this is my charging setup

The PSU fried yesterday; I'm picking up a chepo ATX PSU and will be adding power resistors to the 5v/12v rails to allow 1A draw. I'm charging my Lipos @ 1C, so 4A. The Electrifly Equinox balancer works great - if anyone decides to get it, make sure you get the 'high power' balance lead set for charging over 2A and only supports 2-5S.

 

[Greywolf74]

You dont need a resistor on the 12V side. Id put a 10ohm 1/2W resistor on the 5V side though to minimize voltage sag on the 12V side

 

[bsodmike]

You dont need a resistor on the 12V side. Id put a 10ohm 1/2W resistor on the 5V side though to minimize voltage sag on the 12V side

It'd need to handle 2.5W for 0.5A? Understood re. the 12V side. The PSU pictured packed up yesterday evening mid-charge, hmm.

 

[Greywolf74]

It'd need to handle 2.5W for 0.5A? Understood re. the 12V side. The PSU pictured packed up yesterday evening mid-charge, hmm.

Sorry bro, I dont understand what you were saying in this post.

 

[bsodmike]

Oh, you mentioned a 10ohm 1/2W resistor; it'd need to handle 2.5W though, i.e. 0.5A * 5V. Anything > 2.5W would suffice.

 

[Greywolf74]

My main point was you dont need a resistor on the 12v side. IDK how small of a resistor you can use to put sufficent load on the 5V side to prevent the 12V side from sagging under load but I do know a 10ohm 1/2W will do the trick. Thats what I've been using in my PSU conversions.

 

[benlinus]

You will need to get either 2x2s lipos or 2x3s lipos and with two 2s lipos the volts are 14.8 and with the 3s lipos the volts are 22.2.http://hobbyking.com/hobbyking/store...arehouse_.html At hobbyking make sure you buy from usa warehouse or it will take weeks to ship it to you.Imo i would go with the 3s lipos if you want it to be pretty fast. Then you will need a charger that charges lipo batterys.

 

[Greywolf74]

You will need to get either 2x2s lipos or 2x3s lipos and with two 2s lipos the volts are 14.8 and with the 3s lipos the volts are 22.2.http://hobbyking.com/hobbyking/store...arehouse_.html At hobbyking make sure you buy from usa warehouse or it will take weeks to ship it to you.Imo i would go with the 3s lipos if you want it to be pretty fast. Then you will need a charger that charges lipo batterys.

Not sure what this has to do with his post. He already said he has two 2S lipos that he was going to be running in series to make a 4S pack.

As for the OPs question about charging them in parallel that never got answered, my advice would be to charge them one at a time unless you get a better charger that is more capable of higher amperage.

 

[bsodmike]

@greywolf74 I ended up using a 50R 1/4W watt resistor on my 5v line - it's essentially dissipating 1/2W but didn't go up in flames hehe.

Also this arrived,

While I was keen to shave a bit off on weight with it, I realised I'm giving up a good ~4,000mah compared to my current 2x 2S 4,000mah = 4S @ 8,000mah config. It was also silly to go for a 4.5 rated Lipo as my charger can only charge in steps of 1,000mah.

I doubt I'll get much out of this pack, although it may serve to be adequate as an 'emergency' backup brick.