Hi, I’m looking for a little information, I have a eviction phoenix multiplus 12/2500/120 and would like to replace my old lead/acid leisure batteries (4) with a large lithium ion battery, my question is, am I able to simply swap the batteries or do I need a different charger. Thanks, Dave
I think you mean lifepo4 batteries instead of lithium-ion. You could use a 12V Lifepo4 battery as drop in replacement. However charging them up to 14.4V is on the edge of what they can handle. I would go for a bit lower absorption voltage (for example 3.55 * 4 = 14.2 or to be save 13.8). You can set this with the dipswitches. And always us a battery with a BMS to protect the battery in all cases.
Thanks for your reply, I’m currently charging my batteries via a victron multiplus inverter (approximately 20 years old) and am being advised that I need a newer generation inverter, I don’t particularly want to do this as it’s worked perfectly all its life.
II doubt those old systems provide a lithium charging profile which new systems do.
Ideally you want to use a battery on the supported list which would want to be connected to a GX so the battery can manage its own charging.
You can still charge it old school style, by setting parameters to the manufacturer’s spec, but do not just swap batteries without making changes to the charging profile.
I agree with Warzel. If you can set the absorption V to something like 14V and a float V of 13.5V on your old inverter it would work providing the LiFePo4 (I would avoid Lithium-Ion unless for specific applications) has a proper (build in) BMS.
Don’t set the absorption V too high as I find that lead acid charging algorithms easily climb through their target V. That’s fine for lead acid, but for LiFePo4 the BMS will disconnect the battery from the system in this case. Taking a lower absorption V might prevent this.
The experts may comment on specific charging algorithms between lead acid and LiFePo4 and if that would be an issue.
LiFePo4 needs a simple charging algorithm. Max current till the absorption V is reached and after a short period drop back to ‘float’ V. Some even skip the float V and just charge to a specific V (as long as it’s above the balancing V of the BMS) and leave it there.
Thanks for your replies, food for thought indeed, you’re right I did mean lifepo4 battery, is it easy to change the absorption settings in the victron. Thanks again, Dave
Just follow the manual as posted above and let us know how it worked out. I would set the absorption and repeated absorption time as short as possible which I think is 1 hour/15 mins. LiFePO4 doesn’t need lots of absorption, but refer to the battery manual for more guidance.