Is a charging Multiplus protected against sudden battery disconnect?

DIY
1

I would like to disconnect the battery from the Multiplus charger with a relay, and keep 230V available (so turning off the Multiplus is not an option).
When the relay is activated and disconnects the battery, will that hurt the Multiplus?

Background:
I have a Multiplus 800, a CerboGX, Raspberry Pi LiFePo4 battery and a 230V dehumidifier. The dehumidifier is turned on or off (with a Shelly plug) based on humidity values measured by the Raspberry Pi. The Multiplus is turned On, when the dehumidifier needs 230V. Trying to prevent the battery from charging to 100% SOC, I turn off the Multiplus when dehumidifying is done. But often dehumidifying takes a long time and the battery is charged close to 100%. So I would like to disconnect the battery from the Multiplus charger with a relay, but keep 230V available.

Thnx,
Bram

2

You cant run the multiplus without battery! Its a battery based system and not designed for it

2 Likes
3

Use the relay to trigger an input on the gx or something to limit voltage in dvcc using a node red flow instead. That is a much safer option.

Or just go to the gx and limit voltage. Or program it in such a way that you don’t reach the full charge.

A battery should only disconnect in a system if there is a problem, to some degree the inverter can handle it. But as normal operation and repeatedly. NO.

4

Thanks for chiming in. Node Red is already doing some things, and I will investigate the DVCC/Lower Voltage solution you suggested.

5

Best way to limit the battery charge is by modifying the charge voltage parameters, reducing Abs and Float voltages slightly. Do NOT disconnect the battery from the Multiplus while it is operating.

3 Likes
6

Here is a simple node-red flow that will limit the charge current as the SOC increases. I do this for one of my systems. It will map the input range of the SOC. My battery is current 0% so will allow full charge of 35amps and taper the current to 0 as it nears 100%. You can play with the numbers to get the desired performance and also change the system to the 800 multi. Hope this helps,

image
image1594Ă—376 62.8 KB

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1 Like