# question

## Smartsolar MPPT OPzS charge algorithm

I’ve looked but can’t find this answered anywhere.

I have a Smartsolar MPPT 250/100, hooked up to a 48v array of BAE Secura 6 OPzS cells.

I want to ensure I’m setting the charge voltages appropriately.

Looking at this - https://www.baebatteriesusa.com/wp-content/uploads/2019/03/BAE-VLA-Installation-and-Operation-Instructions-0219.pdf - it appears float is 2.23VPC, equalise is 2.4VPC, and absorption I’ve taken as 2.33VPC.

These voltages are more or less identical to those that victron list for their own OPzS cells - https://www.victronenergy.pt/upload/documents/Manual-Stationary-batteries-EN.pdf.

So... why do all of the OPzS charge algorithms in the firmware seem to be a mile off these values?

The most conservative setting recommended for OPzS (Position 1) gives 2.3VPC for float, 2.68 for equalise, 2.38 for absorption. +0.07, +0.28, +0.05, respectively. It also limits equalise to 8% of charge current, although at 900Ah I should be able to do the full 100A until 2.4VPC at which point it drops to 45A (5A per 100Ah), so surely a setting of 45% would be safe?

Can anyone shed any light on why, and what I should do? I’m using the values from the data sheet currently, and doing the commissioning equalise at 2.4VPC - but the MPPT is limiting the charge current to 5A, when it could be delivering much more - there’s a 4kW array in direct sunlight right now.

Thanks!

1 comment

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Update: the charge current was being limited because the batteries were full. D'oh. The question re: the discrepancy between Victron's OPzS datasheet and the MPPT presets stands, however.

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Justin Cook - Bay Marine Supply USA answered ·

@Maxwell, the simple answer is that every battery manufacturer's recommendations are slightly different, and Victron can only "preset" so many profiles.

Always defer to your battery manufacturer's charge voltage recommendations and, if it varies significantly from the presets available in the Smart MPPT, simply use the "user-defined" setting in VictronConnect to set the charge voltages according to the manufacturer recommendations of your particular battery bank.

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