what is the absorption rate for my 280amh LiFepo4 battery (see pdf-attached)

[Flyfishing55]

Looking for absorption rate to put in my Victron 100/30 controller. specs are in pdf....but i couldn't find this info... Also, I read somewhere that the only info needed in the Victron controller (app set-up) was the absorption rate...which i understand has other names? ( bulk or max voltage).

 

[Fred S]

Only "bulk" charging needs to be used. No absorption, equilization or float volts or time is needed for lifepo4 batteries. If you can't turn those settings off, then I'd set absorption to 14.2v, and equalization and float to 12.8v (assuming a 12v battery - double these for a 24v battery). According to your manual, both the bulk voltage and max cutoff voltage should be set to 14.6v.

 

[Flyfishing55]

Hi Fred: I haven't programed the Victron smart controller yet as I am waiting for the BMS to show up from China. I am pretty sure I only need the bulk number to program the controller. I may have to add a number for the low temp cutoff, but I think the BMS has that feature. I will use 14.6v. Thanks for your help. Tim

 

[JoeHam]

Personally I wouldn’t go above 14.2v since there is little to gain above that level.

This article may be helpful:

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...

www.solacity.com

 

[Flyfishing55]

Personally I wouldn’t go above 14.2v since there is little to gain above that level.

This article may be helpful:

How to Find Happiness With LiFePO4 (Lithium-Ion) Batteries –...

By: Rob Beckers You have just sold your first-born into slavery, remortgaged the house, and bought yourself a lithium-ion battery! Now you want to know how to take care of your precious new purchase: How to best charge lithium-iron batteries, how to discharge them, and how to get the maximum...

www.solacity.com

Excellent article. Answered many questions I had....saved in my favorites for future use!

 

[Fred S]

In fact I only go to 28v (same as 14.0 for your 12v battery) myself.
I forgot a couple things in my post: 1) there are also hours duration that can be set for bulk and equalization. I have set the bulk charging for 5 hours I think (default was 3), and the equalization is set to zero hours - or something low if it won't accept a zero; 2) the temp compensation is zero, not the "-3" default.

 

[gnubie]

The current firmware for the Victron SCCs will set the 'absorption' voltage to 14.2 (12v) / 28.4 (24v) if you select the lifepo4 preset and equalisation is turned off. It's not absorption charging, it's just a legacy term from lead acid days, just in case anyone starts waving their arms around saying "OMG OMG YOU CAN'T DO ABSORPTION CHARGING ON A LIFEPO4!!!!!!"

The default 'absorption' charge time is 2 hours if the SCC can't separate battery current from load current. If it can separate them it will use tail current to decide when to switch back to float mode. It's not float charging either, again that is a legacy term.

In most circumstances 2 hours is longer than is really required. lifepo4 will quickly rise to full voltage towards the end of charge. 15 mins is usually quite sufficient to let the battery's BMS do any cell balancing that it needs to. After 15 mins the current into the battery has likely fallen quite low so my personal advice would be to set 'absorption' time to 15 mins. You could simply watch the charge current the first time the battery is charged and select an appropriate time based on that, if your Victron can't separate battery and load current that is.

 

[Flyfishing55]

Thanks for all the great information...if anyone has anything to add please do. Tim

 

[Ampster]

Thanks for all the great information...if anyone has anything to add please do. Tim

@gnubie gave a very clear and simple explanation. I agree most of terms are Legacy terms from Lead Acid. I like to use the terms Constant Current (CC) and Constant Voltage) because they are more descriptive of what is actually happening. However most inverters and charge controllers use the Legacy terms so we have to understand those terms in order to properly charge those batteries. To make it easy for me I translate:

• Bulk is CC
• Absorb is CV with a defined endpoint of either current or time.
• Float is CV at a lower voltage than Absorb and with no endpoint (have to check that for accuracy) it is synonymous with trickle charge for Lead Acid. It should be used more cautiously with Lithium because Lithiums do not discharge as quickly as Lead Acid.
• Equalize is a setting used for Lead Acid batteries to balance the cellsc within a battery but turned off for a Lithium pack.

I am familiar with forums that have "stickies" where knowledge like this can be shared. This forum has a Wiki but I don't know how to add to it.