Is charging too slow bad?

Is there a point where charging too slow is actually harmful for a cell?
For example 30Ah+ pack charging at 1.5A .
Don’t mind the time it takes.

tagging the guru :blush:


Dude your overthinking it, its not bad.

There may be some better charging methods in some situations, like for lead acids where the charger is “pulsing” and doing dome wizardry to “clean the cells” buts in our applications and with our batteries I don’t know of any other charging method than a regular li ion battery charger


I’m not aware of any disadvantages to slow charging until you get so slow that the cells are actually self-discharging faster than you are charging. We’re probably talking under 1mA here for a pack. :grin:

@soketsu brought up something I hadn’t considered…spending a lot of time at a forced high state-of-charge will speed up aging of the cell. But we’re talking some crazy slow charging here.

The advantages of relatively (not extreme) slow charging are definite though…extended cell life and faster/better balancing.


Inb4 1A chargers become as popular as 8A chargers…

1 Like

All my chargers are 2 amp, takes forever but I’m hoping to get the longest life out of my packs.


You can for sure charge it at a higher rate than that, if you are super worried about shortening your cell life span, use 50% of recommended charge rate, if you have a 4p pack, that’s at least 1A per cell

I cant imagine charging below 4A even my phone lol


Yea, I can’t imagine much of a benefit to charging at less than 1A per cell for power cells (20A current rating or higher) or 0.5A for energy cells (under 15A current rating).

As long as it’s at room temp or a bit lower. Higher temps than that, easily done with cells in a battery pack where they all heat each other up and the pack is wrapped up, can speed up cell aging.

Definitely always keep charging cells under 45°C if max cell life is a concern. Lower is better.

no, don’t charge your pack in a refrigerator :joy:


Normal slow charging wont cause harm.

Extreme slow charging can indirectly shorten cells’ life span.
By extreme I mean like charging 30Ah with only 0.03A lol.


Could you explain how it does that?

(edit) Wait…I think I know…

My guess

Too much time at high states-of-charge accelerates aging and extreme slow charging leaves the cell at a high charge point for a lot longer.


would take 100hours to fill from 90% SOC to 100% SOC (if my math is right)
Surely, staying long in such high SOC would age the cells a bit.


Agreed, that’s what I realized too late. :slightly_smiling_face:
Thanks for posting that! Amending my other post.


I got a 2amp for my 3p pack it wasn’t that bad, on my 8p pack I never timed it but I’m sure its 10 hours plus.

I am eventually upgrading to 6amp.

I usually use a 7A on my 4P pack, charges from dead to full in about 2.5hrs and add another ~30 mins for a good balance. I like to ride and charge multiple times in a day

that said i want to slow charge overnight, take advantage of the full 10+ hours it sits unused and hopefully extend my pack life.

I guess according to @Battery_Mooch I shouldn’t charge below 4A as I’m using power cells? but I guess 2A would be okay?

1 Like

What are power cells?


“Power Cells” is generally how we refer to cells with high current load ability that sacrifice on cycle life and/or capacity (mAh)

“Energy Cells” is how we generally refer to cells with lower current capability, usually designed for higher cycle life and/or capacity.

1 Like

Huh? I have no idea how you came to that conclusion. 1A per cell is a recommended standard or slow charge rate for high power round cells. It is no where near the “too slow” threshold we’ve been discussing.

A too-slow charge might be down in the few milliamps level, or lower. Charging at 0.5A/cell is a standard slow charge rate used by millions of people for cells like those.


bear with me.
Im slow.

On my 12S10P 30q 30AH pack.
I usually use a 7 amp charger looks to actually charge a 5.5.
I just got a 5 amp charger which looks to charge at 4.5 amps.

I have been pondering making an adapter for my 2 amp charger to use on my large packs.

the 12S10p 30q and my 12s7p P42a pack.

I expect that would actually charge around 1.5

the 12s10p pack struggles with keeping that cells even…

do you guys think iay benefit from the 2 amp charger on these larger packs?

it’s not a conclusion, hence the question mark, I guess I’m wrong and going down to 0.25A per cell is okay?

I disagree. You came to a conclusion, clearly stated, and was asking if it was correct.

Based solely on my post what would your conclusion be?
Then you have to decide if my post is actually correct or not. :joy:

it’s a guess, and an ask…