question

chris-job avatar image
chris-job asked

Constant charge for Smart Lithium

Hi guys,

I have a boat with the Victron smart lithium batteries 3 x 200ah and while the boat is not being used it has a constant load of around 3amps to run monitoring systems, WIFI etc. I want to keep all this on as I want to remotely monitor the boat.

I am really trying to keep the batteries between 40% and 70% to extend their lives while the boat is sitting there but I need to keep the boat connected to shore power as the solar is not enough to hold the charge. I am using the DVCC fuction on the cerbo for the multiplus to limit the maximum charge current usually at around 4-6amps to keep the batteries between 40 and 70%. I adjust this manually. Just before I use the boat I will up the charge current to 120amps to bring them upto 100%.

I just have a few questions:

1. Do you think this is a good way to exend the life of the batteries

2. Is there a better way to float the batteries at aroud 60% without turning everything off? I was thinking of putting in a relay for 240v on the Cerbo gx in generator mode so it will connect the 230v when the charge is low and disconnect when the charge level is higher.

3. Will the constant charge harm the batteries even if the current is lowered. It seems that the voltage is also lower when you reduce the current via DVCC. Would you recommend setting a lower voltage for doing this? If so what would it be?

Thanks in advance Victron experts

Multiplus-IIcerbo gxbattery chargingLithium Battery
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

4 Answers
snoobler avatar image
snoobler answered ·

1. almost.

2. Use DVCC to limit voltage as well.

3. Yes. Yes. 13.2V

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

chris-job avatar image
chris-job answered ·

Thanks snoobles, as to the answer 1. do you know of a better way of doing this?

BR Chris

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

snoobler avatar image
snoobler answered ·

#3. Simply float at 13.2V.


About every two weeks. Let the MP run it up to 14.4V and hold for 2 hours. The cells need to spend time at elevated voltage to balance.


2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

aplord avatar image
aplord answered ·

You can use the generator relay function in the Cerbo to switch some chargers, eg the Victron Phoenix. I have implemented that, to keep the SOC between X% and Y%. It works just as you say, but no need for a separate relay, just the Cerbo and Phoenix and a control wire between them.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.