I have a working system that uses lithium batteries. the system was originally configured as a hybrid (solar/grid) power source in an RV. I have disconnected the solar panels and moved the system into my basement where it functions as backup power for my sump pump. I wish to swap out the lithium batteries for AGM. Something in the configuration prevents the AGM batteries to be charged. Can anyone help me reconfigure the system? I can make details and photos available.
Post your configuration and your battery spec, that will help anyone here who wants to diagnose.
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Hello
this is an attempt to answer the request for a description of how my set is configured. Please let me know if this is the information you wanted.
This is a fair representation of the configuration of my set-up. I have modified the original diagram from AM Solar to show my two Lithium batteries.
This circuit has maintained my batteries since 2018 with no problems. THE INVERTER CHARGER IS A MULTIPLUS COMPACT 12/2000 80-50 120V
In 2023 I disconnected the solar panels (6 -100watt panels) from the system.
Also I disconnected the “alternator” related parts of the circuit which were meant to obtain charge voltage from the vehicle alternator and provide “boost” to the vehicle starter.
With those functions eliminated and the system plugged into my house power (grid) the lithium batteries have stayed in float mode.
When I experimented by substituting the lithium batteries with one 100AH AGM battery I found the system would not charge the AGM and according to the flashing LED’s on the Multiplus there was insufficient battery voltage for the inverter charger to perform any charging on the new battery.
This explanation seemed odd but it came with the suggestion that I change the settings in the Multiplus so that it can respond to the AGM’s normal voltage which, I was told, is different from the lithium voltage.
I have the USB device to connect the system to the Victron applications. Using the app., I ran into dire warnings that changing settings is for experts only. Fair enough but I can not find an expert within 200 miles.
Michael Shore
PS sorry about the 3 uploads. I am not a computer expert .All the same image . I struggled to create a jpeg.
I am totally baffled by this format. Sometimes a robot responds, sometimes a person. I fear I am wasting your time by not knowing the procedure for asking and responding. I have finally arrived at the pages in the Victron app where settings can be changed.
I am hoping for some guidance in making the changes that will safely charge the battery described in the attached photos.
Sorry i missed your reply from the 4th November.
I would have scribbled ln a piece of paper and taken a picture. You definitely went all out there.
You could use any of the gel presets for the AGM. The voltage range is correct. Are you cycling them? That is the only difference between the presets.
The for experts warning is really there to remind anyone using the app and tools is that you are the one responsible for anything that happens beyond that point.
You can use the @shrgrp when replying i will get a notification.
thank you for the response.
I cannot work on the system today (1-18-25) or tomorrow . I should be able to put some time in Monday .
I need to understand better what you mean by " cycling them" and how the affects “the differences between presets”. The grid is very stable here. I am just being cautious.
My goal is have a back up power supply in case the grid fails.
Thanks for the response!
I can not work on the project today or tomorrow but I will get to it at the start of the next week.
I don’t understand the meaning of “are you cycling them?” . It might become clear when I get a good look at the web page.
Nevermind.
In these discussions its always hard to know the knowledge level of users, so don’t be offended if any of the experts say things that are plainly obvious. I’m not an expert, but here’s a quick explanation of chemistry to make sure we are all on the same page.
The purpose of the charger is to provide the correct voltage and current at the correct time so that charging, floating, or maintaining the battery happens. The correct voltage and current will be dependent on the chemistry of the battery (e.g. LiFePO4, AGM, lead carbon, Lithium Ion, etc), the temperature, the part of the charging cycle you are in, and possibly other factors. You are maintaining a full battery for grid failure emergencies, so its very much like a UPS system (Uninterruptible Power Supply) - for this, most of the time you are just putting a tiny trickle into the battery to keep it topped up.
For LiFePO4, the cells typical cycle from 3v up to 3.65v per cell, for lead its more like 1.8v to 2.2v per cell, hence the various profiles in the charge controllers.
So if you took a LiFePO4 battery off the system, and did not change the profile, and put an AGM in place, depending on the number of cells in the old vs new battery, its likely that the charger will be putting out a voltage that is too high or too low for the new battery. Too high = cooking the battery, too low = the battery never gets fully charged.
The meaning of “cycling” is allowing the batteries to get down a bit, and then charging them up again. This is different to charging them, and then keeping them full with a trickle of power. Some batteries need at least some amount of cycling, so the controller operates more of an on, off, on, off cycle rather than charge-at-full-rate, then trickle forever (or until the battery drops due to a power cut).
If you are keeping them charged and the system is behaving like a ups, then you are not cycling.
The system will be on float charge (you will see the value on the battery datsheet). Only discharging during power cuts as you have explained. And will charge up using the inverter charger.
There is a preset with the correct values to use so you don’t need to worry about setting everything.