Good day all

I want to add an additional battery to my current solar installation. I currently have the following installed

• Victron Multiplus II 48/5000
• Victron SmartSolar MPPT 250/100
• Victron Cerbo GX
• Around 5000 watt solar
• Dyness BX51100 5.12kwh battery

I asked the company that did the install for a quote on an additional battery and they charge and additional R7500 for labour, Lynx Power In, some fuse link, pull fuse disconnector and some cables.  

My question is, is this all necessary? I though you can just switch off the system, connect the two batteries, comms cable between batteries, setup slave an master and switch everything back on?

Thanks 

My guess is that your current wiring (and probably fuse) between the inverter and battery is not adequate to handle double the current that your battery bank can now produce, so you would need the new disconnector and then the wiring between the batteries and inverter would need to be upgraded, possibly with a bus bar. As far as materials as concerned that looks ok, but I can't really say anything about the labour charge as I have no experience with that.

7 hours ago, AndrewD said:

I though you can just switch off the system, connect the two batteries, comms cable between batteries, setup slave an master and switch everything back on?

Theoretically yes, after all, I assume your battery can supply 5kW worth of energy to your 5kW inverter, hence, the cabling should already cater for your app. 100A current potential a second battery should not allow your inverter to become a 10kW inverter and if that remains the same the current draw peak and charge current peak for two batteries will remains the same as for one battery, just divided by the two batteries now...

Edited October 24, 20223 yr by Kalahari Meerkat

8 hours ago, AndrewD said:

Good day all

I want to add an additional battery to my current solar installation. I currently have the following installed

• Victron Multiplus II 48/5000
• Victron SmartSolar MPPT 250/100
• Victron Cerbo GX
• Around 5000 watt solar
• Dyness BX51100 5.12kwh battery

I asked the company that did the install for a quote on an additional battery and they charge and additional R7500 for labour, Lynx Power In, some fuse link, pull fuse disconnector and some cables.  

My question is, is this all necessary? I though you can just switch off the system, connect the two batteries, comms cable between batteries, setup slave an master and switch everything back on?

Thanks 

Original installation should have been designed for maximum charge and draw current from the inverter. The MPPT also can only deliver 100A so I see no logical reason for cable or fuse upgrades unless the Dyness battery is a 0,5C or less device and your set up was configured for this.

51 minutes ago, Peter V said:

Original installation should have been designed for maximum charge and draw current from the inverter. The MPPT also can only deliver 100A so I see no logical reason for cable or fuse upgrades unless the Dyness battery is a 0,5C or less device and your set up was configured for this.

If you haven't had this already done, I would also advise getting an alternative quote from another 1 or 2 installers... it's really disappointing that we develop a relationship with the first installer and still we are taken for a ride.😡

1 hour ago, Peter V said:

Original installation should have been designed for maximum charge and draw current from the inverter. The MPPT also can only deliver 100A so I see no logical reason for cable or fuse upgrades unless the Dyness battery is a 0,5C or less device and your set up was configured for this.

The a/bx series is 0.5c

In times where loadshedding is the order of the day installers are in high demand and can charge pretty much any price (and people still pay). Also say what area you are staying in, there are a couple of installers on the forum that might be able to help you. The problem is that your installer might not want to give you any support if someone else worked on the system and something breaks.

 

On 2022/10/24 at 9:59 AM, AndrewD said:

I asked the company that did the install for a quote on an additional battery and they charge and additional R7500 for labour, Lynx Power In, some fuse link, pull fuse disconnector and some cables.  

Look, there is a point to all the fuses and linkages. When adding another battery you are also adding more heat to the cables and more current for charging etc. In another topic I have been looking into an Axpert 11kW MAX-E that didn't have the appropriate fuses in place and when it blew the mainboard was severely damaged and the dude is going to have to pay half the value of the inverter just to replace the boards that were blown. Setting up the DC fuses correctly would have saved him like 15K in repairs, don't be like this guy, make sure that all the correct safety measures are in place when installing additional batteries etc.

 

Although, it does seem a little steep for adding a battery and a couple extra connections. Look around and get another quote or you can shop for the parts yourself. If you buy the DC fuses etc before hand he may be a little more reasonable with his labor charges. 

1 hour ago, Psy said:

When adding another battery you are also adding more heat to the cables and more current for charging

I disagree, if this lot was wired up for 5kW and thus 100A or so, nothing will change, he'll be able to run longer off the batteries and they will take longer to charge up, but no need for increased current cabling, since he won't be changing the inverter or MPPT side of things, only if he is going to upgrade the inverter to a higher power rating, or the MPPT, then he'd have to look at the cabling, until then, assuming the cable is rated to carry the 5kW to the inverter/from the MPPT to the battery, there is no need to go overboard, if the battery has a fuse/protection, that should also be ok and not require additional expenditure.

30 minutes ago, Kalahari Meerkat said:

he'll be able to run longer off the batteries and they will take longer to charge up

spot on.
It's similar to adding an additional fuel tank to a car. It will give you more range, but no need to upgrade anything else, except to connect the additional tank to the original one.

Just my 2c, which is to not design the wiring and fuses around the inverter when it is operating as expected, but for the current that can be pushed by the batteries when something in the system goes wrong. No idea what that could possibly be, board blown, short circuit, whatever, it's just an uneasy feeling.

26 minutes ago, GreenFields said:

the current that can be pushed by the batteries

Batteries don't push, the device consuming the power, draws and thus limits the current it will consume.

In a easy DC circuit explanation see the battey connected to the load and for ease, let's make the load a resistor of value 54Ohm and the battery sitting at 54Volt, now, with Ohm's law, I=V/R, the current I will be V=54/R=54 = 1 Amp. the battery can not *push* any more, but what the load, the resistor in our simplified circuit will consume... the resistor in our case had better be rated at 54W minimum and have some way of cooling down...

@AndrewD if the system was installed correctly then all you would need is need link cables for the new battery and most importantly correct length for the main neg and positive, your fuse should be the same as you would be drawing the same amount of amps as before just that you capacity will be higher thus giving you more amp hours.

Thanks everyone for your inputs. I had electronics in high school but have not used that in a very long time. The batteries will be connected in parallel thus increasing your amp-hour capacity. The amount of current you can draw is still limited by inverter and thus cannot draw more than what the system is currently designed at. 

The current fuse size is 125 amp and the cable thickness is 25mm thus I don't believe that the current system is under designed. I am going to connect the battery and see how the system behaves. Will provide feedback. 

Thanks again for all the input

2 hours ago, AndrewD said:

I had electronics in high school but have not used that in a very long time.

 

 

Refresher course

Hi all

Have done my install of the additional battery but something weird is happening with the charging/discharging of the battery. It only show's have the wattage it should be showing.

The total PV charger does not add up to the total loads plus the charging. (677+577=1254 missing 450 watt). Previously it did. Think the second battery is causing this. Did to a redetect on the battery but did not do anything. Any ideas what settings should be changed?

Edited November 8, 20223 yr by AndrewD