question

rithym1964 avatar image
rithym1964 Suspended asked

2x Multi II 48-5000 in Parallel Very Low Charging

Hi to all

Trying to troubleshoot a charging problem with 2x Multi II 48-5000-70 in parallel Master & Slave. I also have Venus GX connected. The two units have been inverting great for couple months now but I had not used any grid charging my solar takes care of that. I normally switch the multis over to grid at 00.00 - 06.00 to take advantage of cheap rate and save my 1000 Ah FLA battery from cycling too low. Today, I decided to switch on the charger on the Master Multi to test charging and at 00.00 when the grid kicked in I see the Master go in to Bulk phase but... only 7-10A of charging ?? I realise by default the Multis only charge at 75% as when I only had one unit I never seen more than 53A charging (and I never figured out how to get the full 70A). I was expecting to see about 100A charging with two units in parallel?? The Input AC current Limit is set to 30A (15A on each unit) as my grid supply is 32A. All cables are uniform acoss the two units.

I don't understand why the charging is so low any help to figure out what is limiting the charging current much appreciated as I will need to charge overnight sometimes when the Winter arrives

TIA

PS I also put a DC clamp meter on each units DC cable and they are sharing the charge output, about 4-5A each.


parallel-48-5000-bulk-charging.jpg



parallel-48-5000-input-current-limit.jpg

battery charging
parallel-48-5000-bulk-charging.jpg (3.6 MiB)
parallel-48-5000-input-current-limit.jpg (3.8 MiB)
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.

2 Answers
Paul B avatar image
Paul B answered ·

Check you charge voltage settings for Absorption and float

also in the GX device check the DVCC as there is a max charge setting there as well

1 comment
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.

rithym1964 avatar image rithym1964 commented ·

Charge settings on the multis are Absorp 60V & Float 54V as per the battery manufactures instructions. As mentioned when I charged with a single multi I got around 53A in Bulk mode but when I set up the two in parallel I am only getting 10A at most.

parallel-48-5000-charge-settings.jpg


I do have DVCC on because the bat temp sensor is connected to the Venus GX and I want it to share this info with the other Victron devices. I just checked and the Limit Charge Current setting is off.


dvcc-options.jpg


Perhaps I should try switching off DVCC completely and then try charging see what I get.

0 Likes 0 ·
dvcc-options.jpg (4.3 MiB)
parallel-48-5000-charge-settings.jpg (3.4 MiB)
Paul B avatar image
Paul B answered ·

I think we need a lot more Information.

battery voltage at the battery

battery voltage at the multiplus terminals

how have you setup parallel operation

what else is connected

how is the batteries BMS connected and does this control the charging

what brand is the BMS and how is it connected

a wiring diagram and installation photos may also help

some screen shots when using the VE Configure program of all screen tabs

are you using assistants

have you setup ESS




1 comment
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.

rithym1964 avatar image rithym1964 commented ·

Okay, I managed to suss the problem. Got up really early this morning and started playing with some of the Multi II settings on the Master. Turns out under the Grid tab there is a section titled AC Low Voltage Disconnect. This was set to 200V rather than the 180V default. For some reason during the night my grid connection voltage drops quite low, certainly below the 200V threshold that was set and this was preventing the Multi charger from using the full 30A (2 x 15A) that was set in the AC Current Limit. As soon as I changed the setting to 180V the charging current jumped up to 60 - 65A. This would be about the limit I would expect as the grid is also running the loads which are around 1200W minimum.

parallel-48-5000-sussed.jpg

0 Likes 0 ·
parallel-48-5000-sussed.jpg (3.9 MiB)

Related Resources

Additional resources still need to be added for this topic