Charging li-ion with UPS charger

Jeremy Choy

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Joined
May 10, 2017
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60
I understand that float voltage is bad. but looking at chargegraphs for lead acid it's a CV/CC until it hits a voltage point then float charges.

Generally it's bad to float charge at 100%. but if float voltage was below the 100% mark the charger would only charge up to the max float voltage correct?

For example:

24v - 7S20P pack (max 29.4v)into a UPS which float charges around 27.3 would only charge the batteries up to a maximum of ~ 92%. If the float charge is CC does it make a difference? you can't get the voltage high enough.

I found a 24v 1500VA for free. or I can get a 3000VA XL for $250. I want to use it to charge my batteries from grid.
 
A 24V ups in most cases will reach 28,8V or so. When that bulk step is done it will go into float where it will sit for certain amount of time. Lithium does not go down in voltage like lead acid does and therefore you get an very strange charge to the cells.

Most of us using lead acid chargers set float and bulk to same so it directly when bulk is done it goes to float and since voltage is same its done kind of.

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
vs
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

I hope i wrote correctly :) Its late here and im tired.
 
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