The difference between 800mA and 2A balance current...

[Greywolf74]

So I did some spearminting today between my iCharger X8 (2A balance current) and my Hitec X2 700 (800mA balance current). I took two nearly identical Liperior 5000mAh 50C LiPos (with similar IRs), discharged them down to 6.4V, and the used my data logger to capture the charge info on both chargers.

I charged them both at 2C and the iCharger X8 with 2A balance current charged 13.8% faster than the Hitec with 800mA balance current. At 2C the X8 charged in 32m 26s and the Hitec did 37m 38s. This turns out to mean the X8 charged 5m 11s faster. At a 1C rate, this is theoretically 10.5m longer wait. I'm going to test it and see because I'm betting it's even longer than that. I will update this post again once I get the results back from the 1C tests.

iCharger X8

Hitec X2 700

 

[Jerold]

If I'm reading this correctly the Hitec X2 700 using a higher current?

I would swap the batteries and run it again to see if there is a difference.

 

[bill_delong]

It's worth noting that your results will become staggering as the IR on the cells becomes unbalanced where the 2A balance current may save you upwards of 20+ min of charge time as the battery ages. This performance gain won't be nearly as beneficial when packs are brand new and the IR is nearly perfectly balanced between the cells.

I tend to charge closer to 4C on average with charge times around 15 min with a brand new pack and I will observe the charge times slowly diminish as the IR become unbalanced between the cells... while the pack may still be acceptable for a basher, I will discard it once the pack takes longer than 30 min to charge knowing that the pack will fade and lose punch toward the end of a long race.

 

[Greywolf74]

If I'm reading this correctly the Hitec X2 700 using a higher current?
View attachment 197788
I would swap the batteries and run it again to see if there is a difference.

Both chargers were set to 10A. The data logger was only reading 9.8A on the X8 and 10.1A on the Hitec. Even if the data logger is correct, and the chargers need to be calibrated, 300mA isn't enough difference to really change the overall comparison between the two.

I finished doing the 1C charges and the 800mA balance current charger (Hitec) took 1h 3m 13s, whereas the 2A balance current charger (iCharger X8) did it in 55m 48s. This means the Hitec was 7m 25s, or 15.02%, slower than the X2. (See graphs below)

One thing I've discovered about these chargers that might be affecting the overall time is the way in which the two chargers balance charge period. If you look at the tail end of the graphs, where it's obviously balance charging, you can see what I mean. The X8 is much newer than the Hitec and has a much smoother balance charge. Now I can't say for certain because the manuals don't go into enough detail, but I'm wondering if that isn't also affecting how quickly the X8 is able to charge as well.

iCharger X8 (1C)

Hitec X2 700 (1C)

 

[RustyUs]

It's worth noting that your results will become staggering as the IR on the cells becomes unbalanced where the 2A balance current may save you upwards of 20+ min of charge time as the battery ages. This performance gain won't be nearly as beneficial when packs are brand new and the IR is nearly perfectly balanced between the cells....

Doing 1C charge rates, and charge times being almost 2x longer than should be.... This is exactly what lead me to try to figure out what was so different about my chargers vs. the higher end variety.

...One thing I've discovered about these chargers that might be affecting the overall time is the way in which the two chargers balance charge period. If you look at the tail end of the graphs, where it's obviously balance charging, you can see what I mean. The X8 is much newer than the Hitec and has a much smoother balance charge. Now I can't say for certain because the manuals don't go into enough detail, but I'm wondering if that isn't also affecting how quickly the X8 is able to charge as well.

iCharger X8 (1C)
View attachment 197814

Hitec X2 700 (1C)
View attachment 197815

Yes, I often wondered if different algorithms are used in chargers during the constant voltage part of a balance charge. Is that even the correct term?

 

[Greywolf74]

Is that even the correct term?

Yep.

Wouldnt surprise me if it was an algorythm of some type. Different firmware designs for sure.

 

[bill_delong]

Doing 1C charge rates, and charge times being almost 2x longer than should be.... This is exactly what lead me to try to figure out what was so different about my chargers vs. the higher end variety.


Yes, I often wondered if different algorithms are used in chargers during the constant voltage part of a balance charge. Is that even the correct term?

You can bypass the CCCV (constant current constant voltage) algorithm to drastically reduce charge time, simply change the charge setting from "BAL" to "LiPo" mode and disconnect the balance lead to do this, however this will reduce the "saturation charge" and technically will reduce the stress on the battery as well, more info here:
https://batteryuniversity.com/article/bu-409-charging-lithium-ion

I used to do this all the time on aged cells to get the charger to finish within a reasonable amount of time, but it's still a good idea to plug in the balance wire after the charge to ensure none of the cells have gone significantly past 4.20V... if you use LiHV cells then there minimal risk. I think the highest I ever saw a cell get was close to 4.25V which is relatively insignificant.

In no way am I recommending that anyone do this, just sharing my personal observations with what I used to do before I invested in a quality charger as a means to "hack faster charge times" with a low quality charger. Those who choose to do this are doing at their own risk!

 

[ahr43]

On occasion I will charge in the LiPo mode and not connect the balance lead. This for shop use in verifying, for example, a power unit install or linking a radio or calibrating a rcvr install. Makes for a quicker bench test charge.

When returning the pack to storage voltage, always connect the balance lead. Thinking this will correct any imbalance occurring in using LiPo mode for a quick charge. Am I correct in thinking this or should I change procedure? -AC

 

[RustyUs]

Thanks for taking the time to test things Greywolf74. I think a lot of people may change their minds about what charger best fits them if they would look at a specific spec, and that spec holds up in practice. I, like a lot of people, kept on upgrading my chargers as my needs grew. I never thought I'd be buying 3S, and 4S LiPo packs let alone having an RC that uses a 6S LiPo pack.

Up until 2019, my chargers were all in the 200~300mA range for balancing current.

They say, "the proof is in the pudding." Going from my most powerful charger at the time (UP120AC Duo) with 300mA balance current, to the 1600mA & 2000mA balance current in my Hota D6 & H6 Pro... the constant voltage balance charge times are noticeably less.

 

[tntpoof]

I have one of these for way outa balanced cells. I can charge at 10 amps on mine thru balance wires I would not but I have done 5 amps. I dont have the radiolink. I have the Schulze one.does not look like this its a open circuit board style

 

[DavidB1126]

I dont have the radiolink.

Good.
I wouldn't buy anything radiolink period. Lol. after all the headaches I had with them.

 

[Jerold]

Both chargers were set to 10A. The data logger was only reading 9.8A on the X8 and 10.1A on the Hitec. Even if the data logger is correct, and the chargers need to be calibrated, 300mA isn't enough difference to really change the overall comparison between the two.

I finished doing the 1C charges and the 800mA balance current charger (Hitec) took 1h 3m 13s, whereas the 2A balance current charger (iCharger X8) did it in 55m 48s. This means the Hitec was 7m 25s, or 15.02%, slower than the X2. (See graphs below)

One thing I've discovered about these chargers that might be affecting the overall time is the way in which the two chargers balance charge period. If you look at the tail end of the graphs, where it's obviously balance charging, you can see what I mean. The X8 is much newer than the Hitec and has a much smoother balance charge. Now I can't say for certain because the manuals don't go into enough detail, but I'm wondering if that isn't also affecting how quickly the X8 is able to charge as well.

iCharger X8 (1C)
View attachment 197814

Hitec X2 700 (1C)
View attachment 197815

All that is true. The 300mA is about 3% of 10V, which isn't ~15% difference you're seeing, and it's entirely possible one charge is better.

The current setup gives you have at least 2 variables, the chargers and the batteries. That's essentially 4 combinations, if we are not looking at the variability of the batteries to charge/discharge under different conditions.

That's why I was thinking to swap the batteries and see if the behavior follows the batteries or the chargers or changes all together. Ideally a single precise load used on two different chargers under the same conditions. Then the only variable is the chargers.

 

[Greywolf74]

All that is true. The 300mA is about 3% of 10V, which isn't ~15% difference you're seeing, and it's entirely possible one charge is better.

The current setup gives you have at least 2 variables, the chargers and the batteries. That's essentially 4 combinations, if we are not looking at the variability of the batteries to charge/discharge under different conditions.

That's why I was thinking to swap the batteries and see if the behavior follows the batteries or the chargers or changes all together. Ideally a single precise load used on two different chargers under the same conditions. Then the only variable is the chargers.

The batteries are nearly identical even down to the amount of cycles and IRs of the individual cells, so the batteries aren't really a factor. If I thought that the batteries could be any sort of significant difference, then I would have done what you are talking about.

As for the 300mA difference, even if I went in and corrected that, it would just broaden the time difference between the two chargers because the charger that took 15% longer is the same one that is getting the extra 300mA.