Fast Charge/Discharge & Longevity of Lithium Batts

[PaulLad]

Am I understanding right that fast discharging doesn't affect longevity but fast charging does? If so, is there a rule of thumb for charging rate to maximize longevity? My Bluetti EB2400 has a 200W AC charger and I want to build my own 500W charger. Will charging it with 500W reduce the life of the battery vs the 200W? Thx!

 

[PaulLad]

bump

 

[upnorthandpersonal]

The AC adapter that's included is just the max that that one can deliver. You won't be able to charge faster by putting a larger adapter on, since it can only take about 170W maximum (limited by internal electronics, not the wall plug).

 

[OffGridInTheCity]

The AC adapter that's included is just the max that that one can deliver. You won't be able to charge faster by putting a larger adapter on, since it can only take about 170W maximum (limited by internal electronics, not the wall plug).

I'm don't see the specs for your battery - this would help answer the question.

For example, if I had a 14s20p battery, then a 500w charge would be 400w/48v = 10.42a charge. 10a/20cells = 500ma/cell - e.g. would be 40% of standard charge spec of 1250ma/cell.


My home powerall has 18650(s) with average specs like this:

Notice the 500ma 'Standard' discharge and 1250ma 'Standard' charge.

For long life, I wouldn't go higher than the 'standard specs' of your battery/cells.

In my powerwall, I average 250ma for charge & discharge - which is 50% of standard on discharge and 20% of standard on charge. I'm hoping this + low DOD in the middle of the voltage range will *greatly* extend the cycles - but I've not seen specific data on charge/discharge vs long-life.

 

[MurphyGuy]

It is not fast charging or fast discharging that harms the battery, it is temperature... but when you are fast charging or discharging, the temperature rises, which then causes the harm.

A battery that has stabilized outside in 35 degreeF weather can be charged much faster than a battery that is sitting on sunny beach at 90 degreesF.

Storing your lithium battery at a full charge is also harmful.. lithium should be stored at less than 50%, and in an environment as close to above 32 degreesF as possible.

 

[PaulLad]

I'm don't see the specs for your battery - this would help answer the question.

For example, if I had a 14s20p battery, then a 500w charge would be 400w/48v = 10.42a charge. 10a/20cells = 500ma/cell - e.g. would be 40% of standard charge spec of 1250ma/cell.


My home powerall has 18650(s) with average specs like this:
View attachment 73609
Notice the 500ma 'Standard' discharge and 1250ma 'Standard' charge.

For long life, I wouldn't go higher than the 'standard specs' of your battery/cells.

In my powerwall, I average 250ma for charge & discharge - which is 50% of standard on discharge and 20% of standard on charge. I'm hoping this + low DOD in the middle of the voltage range will *greatly* extend the cycles - but I've not seen specific data on charge/discharge vs long-life.

The manufacturer doesn't provide the specs as its an all in one unit.

 

[OffGridInTheCity]

The manufacturer doesn't provide the specs as its an all in one unit.

Do you know the capacity? (volts + ah or kwh) This would give some context a how big a change from 200w -> 500w might be.

 

[PaulLad]

The AC adapter that's included is just the max that that one can deliver. You won't be able to charge faster by putting a larger adapter on, since it can only take about 170W maximum (limited by internal electronics, not the wall plug).

Are you sure? According to Hobotech you can.

 

[PaulLad]

Do you know the capacity? (volts + ah or kwh) This would give some context a how big a change from 200w -> 500w might be.

 

[PaulLad]

The AC adapter that's included is just the max that that one can deliver. You won't be able to charge faster by putting a larger adapter on, since it can only take about 170W maximum (limited by internal electronics, not the wall plug).

 

[chrisski]

I recommend putting together your own crate build with products you know the specs for.

When I read a post that says I have been charging with 415 watts for two hours and its great, kind of makes me roll my eyes. The battery spec sheet will give max charge rates and they’re there for a reason and to me its much too expensive to just guess at this stuff.

I just built a crate and the goal of that was to power a 300 watt inverter with taking in energy from the panels to cover it while its doing it. I think you’re ready for a bigger project.

 

[PaulLad]

When I read a post that says I have been charging with 415 watts for two hours and its great, kind of makes me roll my eyes. The battery spec sheet will give max charge rates and they’re there for a reason and to me its much too expensive to just guess at this stuff.

The only reason I posted that is because the admin said it wasn't possible to charge it with more than 170W. My point wasn't that its safe or that someone should do it. That's why I'm asking the question on this forum.

 

[upnorthandpersonal]

Are you sure? According to Hobotech you can.

Yes, but that approach is putting the power supply to the solar input. You can do that - the system will then just see the input as if it were a solar panel. Just stay at the maximum solar panel voltage and power and you should be fine.

 

[OffGridInTheCity]

You don't say the voltage! - just so you know, it really helps to share the voltage of any battery under discussion

BUT - let's go with the "2400wh/1000w" spec that you shared. This indicates a 2.4kwh battery with 1000w max discharge. This size of battery should be able to handle 500w of charging. For example, a 2400wh could be 7s33p of 3000mah cells. At 500w of charging / 24v we get 21a. 21a/33cells = 637mah/cell of charging which is not raising any red flags for me.