atloubser avatar image
atloubser asked

New blood needs sanity check. - Using Victron MPPT & Battery with Synapse 3.0+ inverter



I am just starting out in he PV / Backup system world and would appreciate it if someone would let me know if my plan for a system upgrade makes sense.


My existing system is made up of a Synapse 3.0+ inverter with two lead-acid batteries in series to provide a small amount of backup power to a fridge, PC and some lights during rolling blackouts. I'm South African and, for someone who doesn't know, we have frequent scheduled blackouts (3 a day for 2h30m lately).

The Problem:

The batteries are now showing signs of corrosion and have lost most of their capacity. Many days there isn't enough time between blackouts for the batteries to recharge fully.

My Goals:

1) I would like to keep the Synapse 3.0+ to charge my batteries from grid at night time after a blackout.

2) I want to replace my worn batteries with Lithium for greater DoD.

3) I want to add PV solar to my installation to allow the new batteries to get at least 1 full charge daily.


My Proposed Solution:

The picture at the top of the post is a simple diagram of the changes I'd like to make to my system.

The first problem I have is that my roof is almost completely East/West facing. This means I need two strings on my roof to get the required coverage during the day to ensure at least 1 full charge per day. My plan at the moment is to have 2x360W (40.4V Voc, 11.4A Isc) panels per string.

Herein lies the second problem: The Synapse 3.0+ only has 1 PV input. This means that I need to get an additional MPPT to run the West string. For this I am looking at the Victron SmartSolar 100/30.

For the battery I am thinking about going either with 2x LFP 12.8/160 or 1x LFP 25.6/200 with the smallBMS for management.

My Question:

Does the diagram make sense as a system that will function as intended? Is there a better design that is maybe cheaper?

Also, I have been told by a supplier that the additional MPPT will only charge the battery and won't provide power to the Inverter, is this right?

Any advice and/or link to a similar functioning design would be greatly appreciated.

MPPT SmartSolarLithium BatteryBMSsolar
2 |3000

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1 Answer
kevgermany avatar image
kevgermany answered ·

Your design looks ok.

Battery settings on the Victron MPPT must be setup for lithium, must match the settings on the Synapse.

Additional MPPT powers battery, yes. Which powers inverter. When inverter pulls from battery it has no way of distinguishing between battery and MPPT. If the synapse is clever enough to run MPPT from solar without battery, he's right, but I suspect the output from the MPPT in the synapse shares a common connection to battery and inverter, in which case he is wrong.

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Related Resources

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Additional resources still need to be added for this topic

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Did You Know - How to create a battery profile for non-Victron batteries?

Victron VE.Bus BMS product page

Victron 3rd party BMS compatibility page