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Old Jan 14, 2015, 01:25 PM
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LiPo 14.8V with HiTec X4 AC-Plus

I have a HiTec X4 AC-Plus. Since my 4S 14.8V 5000mAh batteries are a bit expensive, I'm interested in charging with an eye towards long life. I read quite a bit of the LiPo sticky threads and I read the HiTec X4 thread even though it's mostly oriented to NiCd or other types of batteries.

I know 4.2V per cell is considered the max safe charge, but I have seen 4.1V and/or a general 80% rule mentioned as a way to greatly extend life -- presumably (and this is strictly my own guesswork) without much impact on mAh because of the curve at the extreme ends of the charge/discharge cycles.

It's easy enough to alarm the battery during discharge for a 3.3V cutoff instead of 3.2V, but how do I expressly limit charging to 4.1V per cell (16.4V total, instead of 16.8V)? Specific to the HiTec X4, I mean.

I'm new to all of this -- my friend says balance charging is controlled by entering mAh, so he's guessing I should enter 80% of the rating, which would bring it down to 4000mAh.

Not to confuse the issue, but I then wondered what voltage relates to the stated 5000mAh capacity -- over the nominal 14.8V range or at max charge (presumably 16.8V)? If max charge, that would imply charging by setting mAh requires a different calculation -- but what? Or is the difference negligible due to the sharp upward spike at the fully charged end of the LiPo curve?

I'm probably opening a can of worms, and this will probably lead to a lot more questions, but...
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Old Jan 14, 2015, 02:47 PM
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Originally Posted by MV10 View Post
I have a HiTec X4 AC-Plus. Since my 4S 14.8V 5000mAh batteries are a bit expensive, I'm interested in charging with an eye towards long life. I read quite a bit of the LiPo sticky threads and I read the HiTec X4 thread even though it's mostly oriented to NiCd or other types of batteries.

I know 4.2V per cell is considered the max safe charge, but I have seen 4.1V and/or a general 80% rule mentioned as a way to greatly extend life -- presumably (and this is strictly my own guesswork) without much impact on mAh because of the curve at the extreme ends of the charge/discharge cycles.

Charging to only 4.1V/cell is purported to increase battery life. Doing so will only impact run time by 2% or 3%.

The 80% rule is different. It states that you should only use 80% of the available power. i.e. 4000mah of a 5000mah battery.


It's easy enough to alarm the battery during discharge for a 3.3V cutoff instead of 3.2V, but how do I expressly limit charging to 4.1V per cell (16.4V total, instead of 16.8V)? Specific to the HiTec X4, I mean.

Cannot address this. What does the Hitec manual say?

I'm new to all of this -- my friend says balance charging is controlled by entering mAh, so he's guessing I should enter 80% of the rating, which would bring it down to 4000mAh.

I think this is incorrect. Generally you will have two charge modes. Charge (without balancing) and Balance Charge. It would have nothing to do with mah selection. Again check the manual. IMHO always balance charge.

Not to confuse the issue, but I then wondered what voltage relates to the stated 5000mAh capacity -- over the nominal 14.8V range or at max charge (presumably 16.8V)? If max charge, that would imply charging by setting mAh requires a different calculation -- but what? Or is the difference negligible due to the sharp upward spike at the fully charged end of the LiPo curve?

I am not sure what you just asked. 14.8V for a 4S LiPo is referred to as the nominal voltage. (Don't ask me to define nominal.) 16.8V is the full charge for a 4S LiPo. BTW any time you refer to a battery please always include the cell count (xS), milli Amp hour (mah), and the C rating, and chemistry (LiPo, LiFe, NiCad, etc).

When charging you generally do not set the mah. What you do is set the charging current and that is generally specified in amps.


I'm probably opening a can of worms, and this will probably lead to a lot more questions, but...

Yes.
May I suggest you read this: http://www.tjinguytech.com/charging-how-tos

Glen
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Old Jan 18, 2015, 09:06 AM
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Thanks Glen. The X4's manual is not so good, but after fiddling with it for awhile I got it figured out. As you suspected, you don't set up charging by mAh, it is by amps. There is another setting in there for a max mAh cutoff, maybe that's what my friend was thinking of.

It doesn't appear there is a way to intentionally charge to just 4.1V instead of the 4.2V max -- there were no settings for this that I could find, and the manual just says LiPo charges to 4.2V. Oh well.

Thanks for the 80% clarification and the link.

Next up is to find some affordable 12ga silicone-wrapped cable to make several long leads for a charging box...
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Old Jan 18, 2015, 10:08 AM
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Thanks Glen. The X4's manual is not so good, but after fiddling with it for awhile I got it figured out. As you suspected, you don't set up charging by mAh, it is by amps. There is another setting in there for a max mAh cutoff, maybe that's what my friend was thinking of.

Many chargers will have a setting for maximum ma returned to the pack during the charge. This is a safety device to prevent overcharging a pack. It will cut the charge off if the ma seting is exceeded. For the most part I think this setting is unnecessary. Just set the parameter to it's maximum value. Your choice.

It doesn't appear there is a way to intentionally charge to just 4.1V instead of the 4.2V max -- there were no settings for this that I could find, and the manual just says LiPo charges to 4.2V. Oh well.

There are chargers that do allow setting the cell voltage. Namely the FMA Powerabs.

Thanks for the 80% clarification and the link.

Next up is to find some affordable 12ga silicone-wrapped cable to make several long leads for a charging box...
Wire: http://www.buddyrc.com/accessory/silicone-wires.html

Note: For long charging cables you might consider 10ga.

Glen
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Old Jan 18, 2015, 03:00 PM
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Have you charged your batteries with this charger yet?

I haven't had a battery charger that got a cell to 4.2 volts yet. It's always 4.1*
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Old Jan 18, 2015, 03:14 PM
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Have you charged your batteries with this charger yet?

I haven't had a battery charger that got a cell to 4.2 volts yet. It's always 4.1*
Any charger?
Which chargers have you used?
Are you balance charging?
Which batteries?
Have you verified the voltages with a meter?

Glen
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Old Jan 19, 2015, 07:10 AM
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Yes, it charges to 4.2V, according to the display. I haven't put a real multimeter on them to check but the separate voltage alarm and voltage checkers both agree.

Thanks for the silicone wire link! I just need enough to run from inside the box to the charger, and since the HiTec X4 is limited to just 50W and 6A per port I think 12ga is more than enough.

Though I do need to think about a long 10ga cable to power the charger from the truck out in the field...
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Old Jan 19, 2015, 10:48 AM
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Originally Posted by ggcrandall1 View Post
Wire: http://www.buddyrc.com/accessory/silicone-wires.html

Note: For long charging cables you might consider 10ga.

Glen
Good lord. How much amperage do you think you're going to need? Maybe 10ga if you're going to 30 amps with leads 100' long.

mw
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