Fast Charging a 24s11p GA Pack

As stated in the specs, a GA cell has a standard charge current of 1.675a (others say 1.475a) .

Is this 'standard current' a safe value that avoids too much heat? Or, is there an unlisted fast charge current for the GA, as is listed for the 30Q (1.5a std, 4a fast)

I have a 24s11p of GA that I'd like to fast charge in the field. Can I safely charge at ~1500w (100.8v 15a) and still be in the safe zone of no heat issues? What would be a safe current otherwise?

15/11 is only 1.36A, you're still under the spec. No problem.

Should be no problem, but the only way to know for sure is to try it and monitor the temperature.

You can go with GA safely up to 1C charge rate if you can monitor temperature in the pack, but the cell cycle life will be devastated (after 150 cycles the cell will be at 70% of nominal capacity). On the other hand charging current up to 0.5C is not affecting GA cycle life.

Tesla is using AVC(adjustable voltage control) charging algorithm for fast charging which significantly increases the cycle life of GA cells.

Oh, wow, so even 1800w is doable on 11p? The battery is sealed away in an aluminum box (hard to access), and all of my other GA cells from the order have been used. But it would be good to test one of them, to see what the thermal max is for charging.

So, if I can use this much power, what is the safe max for any random electrical outlet in the US (110v)? I plan on charging a few different places, and I don't want to be that guy who blows fuses when I do, lol.

If you NEED to you can. But charging so fast will kill the pack in 100~200 cycles at best. Considering the pricetag such a pack has you might want to consider lowering the current to the lowest you can get away with. Ideally you want to charge as slow as you can so its full when you depart. There is no reason to murder your expensive battery "just because".

In the US the standard 110v outlets will be fed from either a 15 or 20 amp breaker.
The problem is that you have no way of knowing what else is drawing power from that particular circuit. I've seen plenty of cases where a 15 amp lighting circuit has been tapped into for an exterior outlet simply because it was easier to access the closest available wiring. Bottom line is that even if you choose a low wattage charger you still have a good chance of becoming that guy who blew the breaker.

There's a lot of places I see outlets around here where there are vending machines or other things plugged in, and one open outlet. Since many of these machines have refrigeration units, whcih in this heat run a lot, even drawing 4-5A from such an outlet could pop the breaker.

Quite a few places seem to be capping off exterior outlets, or turning the outlets off.

Even restaurants and fast food places may have interior outlets turned off, so people don't plug in laptops/etc and sit there for long periods (some also have signage limiting the amount of time you're allowed to stay there, often 30 minutes or less). There's a couple of places I used to go to (after the housefire while I was at an apartment during the rebuild) specifically so I could use their free wifi to get on the forums, that have rows of outlets just for you to plug laptops/etc into---but they were all turned off, and they wouldn't turn them on, cuz they didn't want anyone hanging around (even if you kept buying more food/etc).



That said, you could get a programmable or adjustable charger, so you can run it at high current when needed, or low current when you don't think the outlet will support anything more, or when you just don't want to abuse the pack.

Meanwell HLG-xxx-xxA series LED PSUs (lots of threads about them) are adjustable via a screwdriver hole under a rubber cap, both for voltage and current. A pair of them in series would do 24s. So you could leave them set to low most of the time, and just adjust them to high when you know the outlet supports it and you *have* to charge quickly. (actually since they're in series you only need to adjust one of them; the other can be left at max current).

The Cycle Satiator from Grin tech is also adjustable and can have several presets to select from, but the high voltage version doesn't do high current, so you'd have to parallel more than one to do that; the meanwells are a much cheaper option in that case, if a bit more tedious to change on the fly.

flippy said:

If you NEED to you can. But charging so fast will kill the pack in 100~200 cycles at best.

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These are the things I want to know about. I'll only be charging at most 0.3C to 0.4C , which sounds reasonable according to previous replies. I will never (and won't be able to) use 0.5C on this pack. Plus, for riding, I only use 0.2C to make 750-800w , and I charge to 4.05v at 0.1C now, and disch to 3.55-3.6v for all rides. So it seems like my pack should live for a while, even with 0.4C charging. Sound right?

amberwolf said:

There's a lot of places I see outlets around here where there are vending machines or other things plugged in, and one open outlet. Since many of these machines have refrigeration units, whcih in this heat run a lot, even drawing 4-5A from such an outlet could pop the breaker.

Click to expand...

This is good to know. I'll just avoid the used outlets to be sure. My charge spots are pavilions and marinas with loads of unused outlets, so I should be good, and I'm only taking a 30 min to 1hr break anyways.

Keep in mind that most of those outlets are probably all tied together on a single breaker. You won't know till it pops if that's the case.

hypertoric_amplituhedron said:

These are the things I want to know about. I'll only be charging at most 0.3C to 0.4C , which sounds reasonable according to previous replies. I will never (and won't be able to) use 0.5C on this pack. Plus, for riding, I only use 0.2C to make 750-800w , and I charge to 4.05v at 0.1C now, and disch to 3.55-3.6v for all rides. So it seems like my pack should live for a while, even with 0.4C charging. Sound right?

Click to expand...

Cycling GA between 4.05-3.55V gives you only about 30% DoD. So there is no worry about cycle life. Your battery will wear more by the calendar age or storing/using at higher temperatures. As I mentioned before GA cells does not have problem with cycle life even at 0.5C charge rate, so anything below will be fine. In fact I think that the optimal charge rate for all modern18650 cells is 0.3C, there is no significant benefit in cycle life using lower rate.

Okay, so for what it's worth, someone did actually post the max charge current for a GA cell. It's 3.35a , found here in thunderheart's reviews. I have the Sanyo GA , which also tested over capacity at 3550mah. So, I have no worries now if I slam 18a into the battery.

Maybe we lost in translation I am trying to say that 18A with 11p GA pack is absolutely fine (it is 0.5C per cell, which is manufacturer recomended value for charging). The only reason for slower charging rate than 0.5C for GA is that you have low power charger or limitation by your socket but not the battery. And in your particular case with cycling battery between 4.05-3.55V (ca 30% DoD) you can go with GA up to 1C continuous and still you will have thousands of cycles available! But you have to start monitoring temperature in the pack during charging.

One of my test is 1C charge and 1C discharge rate at 50% DoD (from full charge 4.2V@100mA cut-off current down to 50% of nominal capacity, which is between 3.6-3.45V depending on cell type) and after 1000cycles there is only about 10% average initial capacity loss on majority of modern 18650 cells! It is sharp contrast with 1C-1C 100% DoD test where the same cells (GA included) are dead after ca 150 cycles!

No, I know what you meant . I assumed you were right, since none of the senior members were correcting you on it. That's always a good litmus test, lol But, you know how it goes ... it's nice to find third party confirmation on a technical thing.

Plus, it's good to know that I'm treating the cells right. This is my 3rd ebike, so I'm not a noob anymore with being hard on them, lol. Getting a full charge in 1.5 hrs with no worries is going to be a huge addition to my adventures.