Some questions on balance charging, store charge, discharge..

hailo

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Hello all. I received my SMC 4s 7400mah lipo yesterday and I would appreciate any advice on lipos. The charge that the battery was shipped at was 3.86, 3.85, 3.84 and 3.85. I balanced charged it on a 4 button charger. So here are my questions:
1. When fully charged each cell should be at max of 4.2v. I did not let it fully charge since the day was getting late and I didn't want to take too long to discharge the batt. I stopped the charge at 4.0 per cell. Is that ok? I ran the kraton for about 30 mins.

2. I brought the truck in and store charge it. What amp should I store charge it at? The factory setting on the charger was 2.0amp. SMC instructions are to store batt between 3.4 - 3.8v per cell. Does the charger automatically stops when it reaches 3.8v per cell? Should I let the charger finish the store charge on its own or stop it when it reaches the 3.8v?

Thanks a many in advance!
 

Cmcrc

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Charger should stop at 3.8v in storage mode. Just let the charger do its thing. It will shut off when done. What charger do you have?
 

hailo

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Charger should stop at 3.8v in storage mode. Just let the charger do its thing. It will shut off when done. What charger do you have?
Reedy 1216C Dual charger. Thank you.
 

Cmcrc

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That's a good charger. I use those same batteries too. You can fast charge them if you want. It's a good battery. I haven't had any issues with mine. I would just recommend to set your voltage cutoff at the highest setting.
 

GuyFromCanada

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Should I let the charger finish the store charge on its own or stop it when it reaches the 3.8v?
This is a good question actually. The charger will reach 3.8V in the constant current (CC) mode of operation...this is where it will charge at your set charging rate and the cell voltage will rise. Once it reaches 3.8V the charger goes into constant voltage (CV) mode of operation where it maintains the target voltage while continuing to pack charge in at a lower and lower charge rate.

The chargers seem to look for your target voltage in a "resting" state...i.e. 3.8V when there is no current entering the battery. So the charge current drops slowly until it reaches 0A (or some small value) before declaring the storage (or full) charge complete. This is the part that can take a long time.

What isn't clear to me is how much the charge level varies for a given terminal voltage. If you stop charging as soon as 3.8V is achieved, then the battery may be undercharged, and perhaps isn't quite prepared for storage, but is probably good enough for a few days or weeks. If you let the storage charge complete, I presume the charge should be good for months before needing some reconditioning.

Perhaps someone can chime in with real experience here. I'm still a noob when it comes to LiPo's...
 

hailo

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Thank you for responding. I watched videos on youtube and read where you take the mAh divide it by 1000 and you can safely charge at the amp. So according to my battery, a 7400mAh, I should be able to charge at 7.4amp (1C) or 14.8amp (2C). My charger can go up to 12amps. But according to the instructions:
MAX CHARGE RATES :
1S Charge 12.0A Disch. 2.4A
2S Charge 12.0A Disch.1.2A
3S Charge 9.5A Disch. 0.8A
4S Charge 7.1A Disch. 0.6A
5S Charge 5.7A Disch. 0.5A
6S Charge 4.7A Disch. 0.4A

So my max setting to charge a 4s is 7.1A and not 7.4A? So that means at 7.1A, I would be charging a little less that 1C.
How would this affect the battery if charging less than 1C?
 

chevys10zr2003

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Thank you for responding. I watched videos on youtube and read where you take the mAh divide it by 1000 and you can safely charge at the amp. So according to my battery, a 7400mAh, I should be able to charge at 7.4amp (1C) or 14.8amp (2C). My charger can go up to 12amps. But according to the instructions:
MAX CHARGE RATES :
1S Charge 12.0A Disch. 2.4A
2S Charge 12.0A Disch.1.2A
3S Charge 9.5A Disch. 0.8A
4S Charge 7.1A Disch. 0.6A
5S Charge 5.7A Disch. 0.5A
6S Charge 4.7A Disch. 0.4A

So my max setting to charge a 4s is 7.1A and not 7.4A? So that means at 7.1A, I would be charging a little less that 1C.
How would this affect the battery if charging less than 1C?
Charging under 1c is just fine for the battery. Some would say it's actually better for it. It is more work on your charger being maxed out though. Also, you should be able to set the charger at 7.4 (or higher) but it will max out around 7.1 amps due to it hitting the max wattage.
 

hailo

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Ok. Another question...and maybe more to come as I'm learning. Today I ran my truck for the second time. I allowed the charger to balance charge the lipo to fully charge. I ran it until the battery came to 3.82, 3.83, 3.83, 3.83v. I used the charger to perform a store charge. In less than 10 seconds, the storage was complete. So is it ok to run the battery down to storage charge and not have to use the charger?
And what amp should I use for storage charging mode?
 

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My battery routine -
I normally charge at 2c (check your batteries to make sure this is OK, for SMC this is recommended)
For charging to storage, I will normally use 1c, sometimes 2c.. Some chargers won't let you storage charge at more than 1 or 2 amps, though.
I have my charger's "Storage" charge set to 3.85vps.
If I have several batteries to storage, I will pull them off when they are in the 3.8X range (regardless of charge or discharge to storage)
If I have extra time, or if I see one cell is off balance, I will let the charger balance the pack at storage. This will save time later when charging to run.
From a balanced storage charge, charging at 2c, batteries are ready in about 15 minutes. If I don't balance them at storage, then it is about 20-25 minutes to fully charged and balanced.
 

olds97_lss

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Ok. Another question...and maybe more to come as I'm learning. Today I ran my truck for the second time. I allowed the charger to balance charge the lipo to fully charge. I ran it until the battery came to 3.82, 3.83, 3.83, 3.83v. I used the charger to perform a store charge. In less than 10 seconds, the storage was complete. So is it ok to run the battery down to storage charge and not have to use the charger?
And what amp should I use for storage charging mode?
It's ok to run the battery down to storage charge, however, what typically happens inside the pack when you use it is that some cells get lower faster than other cells due to them being wired in series internally. This is where balancing comes in to keep them all as even as possible.

If your checking the voltages and your right at 3.8V on each cell, it's probably fine to just let it be.

My charger maxes out at 5A when storage charging. As the voltage gets closer to 3.8, it drops the output automatically as @Jerry-rigged suggests.

I run the 2S 7200/7400 packs from SMC. They were 7200 last year, but I got 4 new ones this year to add to my collection and they are 7400.

My charger maxes out at 100W per port or 10A per port. I charge mine at 10A always and they seem to be doing fine. Have had 2 of my packs for about 16 months and another 2 for 12. The older pair are taking a bit longer to charge than my others, but they still charge fine, balance fine and run fine. I run mine until the LVC kicks in unless I break something. I have my LVC's set to 3.5V in all my trucks. If I don't drain them in a truck, I drain them on the charger unless I know I'm going to use them the next day. My charger (as probably do many others) will discharge when using storage mode, but they only discharge down to the storage voltage vs when you use the actual discharge mode to run it down to the minimum voltage. My charger will only discharge at 5A max, so it takes a while to drain them if they are full. Was even worse when I ran 9000mah 2S packs.
 

hailo

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What is the capacity cut off function of a charger? The default is set to 5000mAh. Does this mean that capacity of a lipo battery at full charge? So for my 7400mAh, I should set the cut off at 7400mAh?
 

GuyFromCanada

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What is the capacity cut off function of a charger? The default is set to 5000mAh. Does this mean that capacity of a lipo battery at full charge? So for my 7400mAh, I should set the cut off at 7400mAh?
This is a safety mechanism in case other halt mechanisms fail. You can set it a bit higher than the capacity...this way you'll still be able to fill it from empty, but if it continues to the cutoff, then it will halt charging. It is the same thing with the time cutoff, just another safety mechanism.
 

olds97_lss

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I have a couple different capacities of 2S packs, so I just have mine set to exceed the largest one by a little bit, 9500mah is my largest and I think I have the charger set to that since I don't use it very often. Granted, that doesn't add a second layer of protection when charging my 7200mah or 7400mah 2s packs, but I'm always around when charging, so I keep an eye on it.

There's also usually a timeout setting as well so it stops after a certain amount of time.
 

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