Charge packs at what amperage?

Hi everyone,

this was probably asked a thousand times ... but i could not manage to find an answer so far (at least for myself), so i would be happy about any hint on that.

I still wonder at what amperage my batteries (7 in series,consisting of 64 cells each) can be safely charged. So whats the best setting for amps?

Hope i get the math right now: I assume that if i have 64 cells per pack/batteryandi want the cells to becharged safely at, lets say,500mA, i can

go with a charging amperage of 32 amps. Or am i a complete dumba.. ?

Best and many thanks!

500mA is a good number for charging and yea that means 32A is safe. I charge and discharge my cells while testing @ 1A (for a single cell) but I like to run much slower for normal use as the slower you go the longer they last.

Look also at your total capacity. Say each cell is 2000mah (2Ah) *64 cells is 128Ah (128000mAh) charging at 32A will take 4 hours So keep that in mind too.

crud said:

Hi everyone,

this was probably asked a thousand times ... but i could not manage to find an answer so far (at least for myself), so i would be happy about any hint on that.

I still wonder at what amperage my batteries (7 in series,consisting of 64 cells each) can be safely charged. So whats the best setting for amps?

Hope i get the math right now: I assume that if i have 64 cells per pack/batteryandi want the cells to becharged safely at, lets say,500mA, i can

go with a charging amperage of 32 amps. Or am i a complete dumba.. ?

Best and many thanks!

Click to expand...

No not a bumbass, you would be that if you didn't ask the question. You don't ask you dont learn

Thanks for the Feedback!

So i am still not sure about the charging:

Looks like 32 amps charging current is not very realistic concerning BMS and Charger.

So just wanted to ask whats your average charging current with your packs, BMS and Charger ? And how long does it take you (on the sunny days, though )

Many thanks

Ok, so what you can do is figure based on what you want to charge each cell at. So, if you have 100 cells in a pack, and you want to charge each cell at .25 Amps, you then would charge that pack at 25 Amps (.25 * 100).
So, as jdeadman mentions, 500mA (.5 Amps), then at 64 cells, that would be 64 * .5 = 32 Amps.

I personally would go with about 250mA per cell. That would allow for any kind of surge (not likely, but possible) so the cells would still be safe at a higher input. At 250mA * 64 cells = 16 Amps. So you have a pretty good range of 32 to 64 Amps.

If you have larger packs, then the charge Amps would go up.

So after todays crash of the forum i was able to retrieve some information that got lost from the google cache concerning this thread:


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ozz93666 Online
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#5 1 hour ago (This post was last modified: 1 hour ago by ozz93666.)
There is also the question of efficiency of charging .... the quicker you charge the more will be wasted in heat ...

It all depends on the internal resistance of the pack ... at a rough guess charging at 1C that's 1hr for a complete recharge 10% of input might be lost in heat ...
charging at 1/10th C ... that's 10 hrs for a complete recharge perhaps about 1% is lost

This is due to I squared R loss inside the cell , in the example above the current is one tenth ... square that and you get one hundredth ...so the rate of power loss is one hundredth at 1/10C compared to C ... but since you charge ten times longer at 1/10C the overall reduction in energy loss is ten times
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Robert Baumer Online
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#6 58 minutes ago
(1 hour ago)ozz93666 Wrote:
There is also the question of efficiency of charging .... the quicker you charge the more will be wasted in heat ...

It all depends on the internal resistance of the pack ... at a rough guess charging at 1C that's 1hr for a complete recharge 10% of input might be lost in heat ...
charging at 1/10th C ... that's 10 hrs for a complete recharge perhaps about 1% is lost

Very good point.... and I am not sure that much heat would be a enemy to your packs. I noticed that my charge backs off on the charge when the batteries get too warm which extends charging time. I would say that while the 1000 setting would be the preferred, 200 would be the safest and easier on your cells.
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ozz93666 Online
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#7 49 minutes ago
(58 minutes ago)Robert Baumer Wrote:
(1 hour ago)ozz93666 Wrote:
There is also the question of efficiency of charging .... the quicker you charge the more will be wasted in heat ...

It all depends on the internal resistance of the pack ... at a rough guess charging at 1C that's 1hr for a complete recharge 10% of input might be lost in heat ...
charging at 1/10th C ... that's 10 hrs for a complete recharge perhaps about 1% is lost

Very good point.... and I am not sure that much heat would be a enemy to your packs. I noticed that my charge backs off on the charge when the batteries get too warm which extends charging time. I would say that while the 1000 setting would be the preferred, 200 would be the safest and easier on your cells.

I think that backing off (on your opus?) is due to getting near the end of charge ...the opus has no temperature censor.... it goes into trickle mode ... in normal circumstances temperature should not be an issue , cells can handle up to 60*c with no problem .. that's too hot to touch!!! ... being warm to the touch if not an issue.
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daromer Online
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#8 48 minutes ago (This post was last modified: 45 minutes ago by daromer.)
ozz93666: The Opus have 1 sensor per cell just under the cell. If or how its used i cannot tell though but the sensors are there Smile

I put in 150A easily currently and when rest of panels is up a bit above 200A. BUT... I have a huge bank so per cell this is nothing.

With my curent solar panel setup (17kw) it would take 1 FULL day of sunlight to charge it.. but more realistic is 2 days of charge. Currently my nightly useage takes 3-4 hours to charge back up again. (Will go faster when the added panels are there)
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 57kWh LiFePo4 | 40*260W Poly
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ozz93666 Online
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#9 15 minutes ago
(48 minutes ago)daromer Wrote:
ozz93666: The Opus have 1 sensor per cell just under the cell. If or how its used i cannot tell though but the sensors are there Smile

Ooooppps I stand corrected ...consulting the manual I see it says it cuts out at 60*c this would never be used in normal usage ...

@ 60*C you cannot put your finger on the cell without pulling away .. it feels very hot ,and 60*C is still within the manufacturers working limit ...

I think you agree the backing off of charge current is when opus goes into trickle mode near the end of charge ...nothing to do with warm cell (about 40*C)
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continues with Comment now at #5 (Korishan)