Lipo Battery

Doug1212

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Can you give me some of your expertise on the using of the lipo batteries. This hobby is all new to me and I am concerned on whether to get into this hobby or not because of the battery’s i’ve seen a lot of horror stories about them or am I just over thinking to much . I need your honest opinion please .
 

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Can you give me some of your expertise on the using of the lipo batteries. This hobby is all new to me and I am concerned on whether to get into this hobby or not because of the battery’s i’ve seen a lot of horror stories about them or am I just over thinking to much . I need your honest opinion please .

Like anything, if you use them properly and don't abuse them, you will be fine. If they were that volitile, they wouldn't be selling them. You need a good charger, capable of charging lipo batteries and some good old common sense. Don't let the batteries scare you away from a great hobby!
 

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(Wall of Text Warning)
If you are new to Lipos, don’t worry, they are not the bombs some people would make them out to be. BUT – you do need to follow the rules, and keep them happy. Something I read on a flashlight forum applies here – Follow the rules, and your lipos will be have happy cells! Break the rules and they may become terrorist cells! :eek: :D

Also, when talking voltage in lipos, it is common to speak about Volts Per Cell. If you see a voltage called out below 4.5v or so, it is pretty safe to assume we are talking volts per cell, and not for the whole pack.

Rule 1 – Right cell for the job – make sure the Lipo’s discharge rating (C rating) is up to the task. Quickest way to kill a lipo is to draw too many amps, presto, puffy cell. Arrma specs out 35C 5000mah minimum in a Quality Cell. Note that some (ALL) mfgrs fudge on the C-ratings, so personally I won’t run less than a 50c rated pack in my 1/8 scale cars (more on this later).

Rule 2 – Second quickest way to kill a lipo is to over discharge it. 3.0v per cell is the minimum – below that, and the cells can be physically damaged (internal chemistry starts to change). Also, some chargers will not charge a Lipo below 3.0vps. As long as your car’s ESC has the LVC (Low Voltage Cutoff) turned on, you should be OK. Note – 3.0 is the Minimum. Many people like to keep their Lipos above 3.5v, or 3.7v, to help them live longer. Below 3.7v, a lipo does not have much MAH left, so you don’t gain much by running them lower. FWIW, the Arrma ESC LVC is set to 3.2v, which normally leaves the battery ‘resting’ at about 3.5-3.6vps.

Rule 3- Don’t charge over 4.2v (unless you bought special HV Lipos). Again, this is a quick way to shorten the batteries life. Most chargers have the charge cut-off set to 4.2 by default, so you kind of have to try to screw this up.

Rule 4 – “Storage Charge” – A lipo is happiest at about 40% charged – which works out to around 3.85v. This is what we call “Storage charge” Any time spent away from this voltage (either higher or lower) will reduce the battery life. Now this reduction is around 10% per year, so overnight at full charge or discharge will not be a big deal. Also, heat while in storage is not good for the battery, storing them at 90f will take another 10-15% per year off the capacity. Most lipo charges will have Storage Mode to charge or discharge your lipos to 3.85v

Rule 5 – Charge rate – Just like the discharge rate, the battery will have a Charge rate – this tells you the maximum safe amps you can use to charge your battery. This is also a C-rating, but it will normally be 1c, 2c, 5c, sometimes 10C. If you don’t know the Charge rating of your lipo, best is to charge it at 1c. Speaking of c-ratings –

C-Ratings – The C-Rating is a way to measure the batteries ability to handle amps. Each pack has 2 different ratings, the Discharge C (often in the biggest print possible on the battery) and a Charge rating (often in tiny print, or only listed on the specs web page ) The C rating is will the the Capacity of the battery (in Amp-hours) * C-rating. So if you have a 5000mah, 20c battery – 5000mah=5ah, so 5ah*20c=100A – this battery should be OK for 100 amp loads. Charge ratings are the same – if that 5000mah battery has a 1c charge rating, you get 5ah*1c=5a charge rate – so charge it at 5 amps. Note – if you have a 5c charge rated battery, you do not NEED to charge it a 5C – you can go lower. But don’t go above the C-rating.

One other note about discharge C-ratings – all battery mfgrs lie. The BEST lipo on the hobby market has a REAL C rating of about 55c. Most 90C lipos will actually test out to about 30c-40c. Also, buying high $$$ batteries are no guarantee that your will get a truly better battery – that “Best real C-rating” is from a mid-priced 75c rated lipo, while “150c” lipos from another brand that cost 4x as much, often test out at 30C or below. Also, bargain basement batteries are often short lived. Read reviews before you buy, and understand that most of the super cheap E-bay batteries are either fake, or just crap.

Storage – Yes, sometimes lipos go up in flames for no good reason that we can tell. So when they are not being used, store them in some kind of fire-proof container. Those fire-cloth bags are almost useless, skip them. Get a proper lipo vault, or just an green metal Ammo can. I use a .50cal ammo can. The lid has a gasket – I cut 3 sides of the gasket out, and only left the front lip, next to the latch. Removing most of the gasket vents the can (in case of fire – fire stays in, smoke gets out) – but leaving that small piece of the gasket helps the latch work right.

Charging – Make sure you get the proper charger! That 50w, $30 charge may seem like a good way to save a few bucks, but with the bigger batteries a 1/8 scale basher needs, it will take hours to charge one of your 6s batteries. Get a good big wattage charger. If you have the budget, get a 2 or 4 channel big wattage charger. Just do it, you will thank us later. For a 5000mah battery, you need about 25w per cell for 1c charging. So a 5000mah 6s pack needs 150w to charge at 1c. Personally, I like to charge at 2C, so that same battery would need 300w to charge at 2c. Get the bigger charger, you will not regret it.

End of life - Most common for lipos at the end of their life - they start to "Puff" If you have a battery that is starting to look round-ish, or is feeling a bit squishy, this is a sign it may be at the end of it's life. Best of dispose of it before it becomes a Terrorist Cell. If the lipo swells to the point that the Mylar bag leaks or ruptures you WILL get a lipo FIRE! So this is a danger sign. Note - sometimes after a hard run the cell will swell a small amount - this is not a problem (usually). But it is something to keep an eye on. To dispose of a lipo - discharge to 0.0v, and then throw in the trash. Most common is to run them to LVC, then use some kind of light-bulb discharger to run them down, then give them a "saltwater bath" - mix up some extra-salty water, and drop the lipo in, and leave it overnight. Do this outside. After the water clears up, the battery is dead, and safe to trash.

What did I miss?
 
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So I have stuck to NiMH batteries for these main reasons:

1. Far less work to maintain. I don't like the idea of spending all winter long worried about the discharge rate of my LiPOs, and cycling them through a charger every couple of weeks.
2. I don't have to worry about low-voltage cutoff as much. I simply put in the battery and run the car until it stops moving. Then charge up the battery.
3. While theoretically any battery can catch fire and/or explode, I don't hear the horror stories on NiMH batteries. They don't sell Kevlar battery storage packs that specifically call them out for use on an NiMH battery (that I know of.)

So what am I missing? What makes a LiPO so valuable that it's worth putting up with all this hassle for?
 

bicketybam

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For me it's the power and the fact that they don't make the vehicle get slower and slower as they discharge. It's pretty much constant power from start to finish.
 

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So I have stuck to NiMH batteries for these main reasons:

1. Far less work to maintain. I don't like the idea of spending all winter long worried about the discharge rate of my LiPOs, and cycling them through a charger every couple of weeks.
2. I don't have to worry about low-voltage cutoff as much. I simply put in the battery and run the car until it stops moving. Then charge up the battery.
3. While theoretically any battery can catch fire and/or explode, I don't hear the horror stories on NiMH batteries. They don't sell Kevlar battery storage packs that specifically call them out for use on an NiMH battery (that I know of.)

So what am I missing? What makes a LiPO so valuable that it's worth putting up with all this hassle for?
For #1, I don't think the frequency is nearly that high. I had some traxxas 3S lipos I bought 18 months ago to use in my ERBE when I got it. I put them at storage charge, then didn't use them until this weekend as I started running 4S right away (2x2S) vs 6S and I never used them. They were still at a safe storage voltage and I hadn't messed with them since January of last year.
 

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So I have stuck to NiMH batteries for these main reasons:

1. Far less work to maintain. I don't like the idea of spending all winter long worried about the discharge rate of my LiPOs, and cycling them through a charger every couple of weeks.
2. I don't have to worry about low-voltage cutoff as much. I simply put in the battery and run the car until it stops moving. Then charge up the battery.
3. While theoretically any battery can catch fire and/or explode, I don't hear the horror stories on NiMH batteries. They don't sell Kevlar battery storage packs that specifically call them out for use on an NiMH battery (that I know of.)

So what am I missing? What makes a LiPO so valuable that it's worth putting up with all this hassle for?

These are all great reasons to run Nimh. For someone starting out, Nimh is perfect - one less thing to stress over.

Plusses for Lipo -

A 2s 7.4v lipo runs faster than a 6c 7.2v Nimh, close or maybe a bit better than a 7c 8.4. Plus the lipo can feed more amps than a Nimh, so you get better acceleration than even the 7c Nimh.

Cost - if you only need 20c 3000mah lipos, they are about the same cost per mah as Nimh. But as the Mah goes up, the cost per mah for lipo becomes much less than Nimh - plus Nimh maxes out at about 5000mah, but you can get Lipos with much higher mah.

Runtime - Same as above - you can get bigger lipos.

Big power setups - if you want a high power motor, like a 3660 SCT motor, or a 1/8 scale BLX185 system, a Nimh simply can't supply the amps needed. You must go Lipo.

Charge time - Nimh, you are limited to 1c charging. Most modern lipo's can be charged at 2c, and higher (if your charger can handle it) so full batteries in 15-20 minutes are possible.

But yeah, they have negatives too, as mentioned above.
 

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For #1, I don't think the frequency is nearly that high. I had some traxxas 3S lipos I bought 18 months ago to use in my ERBE when I got it. I put them at storage charge, then didn't use them until this weekend as I started running 4S right away (2x2S) vs 6S and I never used them. They were still at a safe storage voltage and I hadn't messed with them since January of last year.

Agree. I have read that if you store a lipo for long term (year?) expect the first charge to be a bit soft. If your charger has a cycle mode, it can be good to cycle a lipo that has sat for a long time before you put it back in service, but there is no need to cycle it every month to keep it fresh.
 

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Agree. I have read that if you store a lipo for long term (year?) expect the first charge to be a bit soft. If your charger has a cycle mode, it can be good to cycle a lipo that has sat for a long time before you put it back in service, but there is no need to cycle it every month to keep it fresh.
I had a charger that would charge them when I bought them, the traxxas dual ID charger, but I sold that because it took too long to charge the 9000mah 2S smc lipos I was running instead. Last week, I cut open the traxxas lipos because noone wanted to buy them and I installed normal 3S charge plugs so I could try them on my outcast... they didn't like it. One of the cells in one of the packs puffed a bit with just 1 run. It took 6 months of abuse in my ERBE before my SMC's puffed at all. Even then, they still worked fine for over a year with a little puff.
 
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