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Lipo charging

Discussion about Tx, Rx, Servo's, Batteries, Chargers, and all the other things we like to talk about..
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Lipo charging

Post by Peter Balcombe »

Mark,
I suspect that when you say that your packs charge to 95-97%, does that mean that you are reading this percentage on a checker after having removed the batteries from the charger?
If so, then it may just be that the checker is reading slightly low or the balance process has reduced the capacity by a few % points, as all it will be doing is to display a percentage figure based on the measured pack voltage by using a look-up table. The charger will expect a fully charged Lipo to deliver 4.2v/cell (i.e. 12.6v for a 3S pack).
Yes, the voltage could also be reduced by the cell balancing process which will discharge high cells to the lowest cell value once the highest cell has reached 4.2v.
Note that if your cells are not well matched during charging and therefore have significantly differing voltages at the end of charge, this could potentially result in a lower than expected charged capacity as the balance process dumps power from the higher voltage cells to achieve balance.

I would suggest a couple of checks:
1. Check the individual cell voltages on the charger when it starts the balance process to note the cell voltage spread. The balance process will then equalise at the lowest voltage. (I don't think that the chargers tend to top-up the pack after initial balancing). If any cell is particularly lower than the rest then I suggest that this indicates a failing cell, particularly if the cells were better matched when new.

2. Fully charge the pack, then do a discharge/charge cycle, noting the discharge capacity against the nominal pack capacity & also the recharge capacity. Although the discharge rate will probably be rather lower than in normal usage, the test should give an idea as to whether the pack can accept & then deliver its nominal capacity.
Rechecking this periodically should also indicate the onset of pack tiredness.

Note that check 1 can be done as part of check 2.

Hope this helps,
Peter
Barry_Cole

Re: Lipo charging

Post by Barry_Cole »

Has anyone actually had a checker read 100%??? I never have.

Anything over 95% is a good charge, in my book.

BC
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Lipo charging

Post by Peter Balcombe »

As you say Barry, a checker is unlikely to be accurate enough, or the Lipo voltage repeatable enough across the production spread of all sorts of batteries, to give 100% unless it is limiting at this number.
The trouble is that although a meter may have a resolution of 1%, it doesn't mean that any measurement is anywhere near accurate to 1%, especially when talking about any battery voltage translated to a charge level using a typical battery voltage/capacity level curve. Many users confuse resolution with accuracy, particularly with digital displays.

My recommendation is that ALL battery checker readings should ONLY be used as a guide to the charge level, not as an absolute value.
Also, you need to take into account that any voltage read on a checker will be with a negligible load applied to the battery. The value will be lower when connected to your real circuit load.
Some old-fashioned analogue meter Nicad checkers used to apply a load to the battery during measurements for a more realistic Battery state indication, but even then, the indication would only be in 'Green', 'Amber', 'Red' bands.
Barry_Cole

Re: Lipo charging

Post by Barry_Cole »

Basically this is technology overload.
We used to charge nicads, by plugging them into a charger for 16+ hours and were happy that they were charged. You knew when they were discharged because your plane stopped flying.
Then we had, as you say battery checkers that had red, yellow, green lights, progress indeed.
Now we have chargers/dischargers that show voltage, current, time and power in and power out.

Most modern radio systems will show the battery voltage of the Tx and Rx batteries to 0.1 volts, with audible warnings should the voltage get too low.

We are now getting some people complaining that they want the voltages shown to 0.01 volts. 90% of them would not know a volt if it punched them in the face.

:roll: :roll: :roll: :roll:

BC
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Ian Davis
Posts: 162
Joined: 18 Mar 2015, 12:33
Location: Bishopstoke UK

Re: Lipo charging

Post by Ian Davis »

John

Like many others I've had doubts about my chargers. I had a BC6 mains/battery charger for many years and found that it was becoming increasingly difficult for it to decide when a pack was balanced.

I first suspected my batteries were failing altho' the mismatch wasn't critical it was always a worry.

I decided to replace with a new one of similar capability. Found this:-



and lo and behold all my batteries balance perfectly. It won't do two batteries at once but in all other respects it is totally capable and from experience I would recommend it.

Ian ;)
john greenfield
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Joined: 18 Mar 2015, 07:52
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Re: Lipo charging

Post by john greenfield »

Hi guys

I use Hyperion dual output chargers and have 4 of them so can see how they perform over time and against each other and I have not noticed any issues between the chargers even thouth they are used several times a week (day!) BUT.... the balance boards are a different matter. Careful investigation has shown that even the slightest tarnishing of the pins in any of the balance lead connectors can throw the chargers off as they can get a false reading.
Balance boards are very cheap and as I have been unable to find any better quality ones I now regurarly replace all my boards. I aklso take care to clean the balance plug on the battery with switch cleaner at regular intervals.

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)
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Ian Davis
Posts: 162
Joined: 18 Mar 2015, 12:33
Location: Bishopstoke UK

Re: Lipo charging

Post by Ian Davis »

John

You're getting confused, the link I sent you shows in the data that it is capable of charging LiFe cells and I can confirm that that is the case. This is not the Imax charger that you mentioned.

Best regards

Ian
Barry_Cole

Re: Lipo charging

Post by Barry_Cole »

It most definitely charges LiFe. I use mine on them all the time.

:D :D :D :D

BC
john greenfield
Posts: 497
Joined: 18 Mar 2015, 07:52
Contact:

Re: Lipo charging

Post by john greenfield »

[quote="MarkDev"]John, I've tried using a spray type of contact cleaner without seeing any improvement , what type are you using? Or would more regular use keep them clean?


M[/quote]

Mark
Regular use does not help as I think it packs any tarnishing into the sockets. I use Ambersil cleaner but there are others available. If the ceaner is not showing any improvement I would change the balance boards.

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)
Barry_Cole

Re: Lipo charging

Post by Barry_Cole »

John,
I cannot find the maker, but it does not appear to be the Imax one.

This link to Amazon works, and I cannot find anywhere else that sells this particular one.



Attached are a couple of photos that clearly show that it states that it will charge all 3 Li cells Po, Fe, and Io

They balance the cells better than the old BC6, and reliably charge NiMh cells.

BC
Attachments
WP_20170808_15_30_02_Pro.jpg
WP_20170808_15_30_08_Pro.jpg
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