question

greg-1 avatar image
greg-1 asked

Are those Victron BMV, MPPT and battries recommended settings good?

AM Solar has a nice list of recommended settings for Victron products (and not only) including Victron Lithium batteries. Are those good?

I own a BMV-702, a MPPT 100/50 & a Victron Lithium Superpack 12,8V/60Ah. Some of the settings differ from Victron's manuals/specs/defaults.


1. BMV-702 manual only provides two settings specific to Lithium batteries (ch. 6, p.37): Peukert’s exponent at 1.05 and charge efficiency at 99% (those are identical to AM Solar's guide). Other values are defaults for "all batteries":

- charge voltage default = 13.2V (AM Solar = 13.9V for Victron Lithium)

- tail current default = 4% (AM Solar = 2% for Victron Lithium)

- temperature coefficient = 0.0%cap/degC (AM Solar = 0.5%cap/degC for Victron Lithium)


2. Bluesolar MPPT 100/50 manual provides (ch. 3.7, p. 11):

- absorption voltage for LiFePO4 = 14.2V (AM Solar = idem)

- absorption time for LiFePO4 = 2h (AM Solar = 1h)

- float voltage for LiFePO4 = 13.2V (AM Solar = 13.5V)

- tail current default = 2A (p. 9) but is actually disabled when choosing Lithium batteries (knob at setting 7) with firmware 1.46 (AM Solar = 0.5 per 100Ah for Victron Lithium)


3. The 12.8V/60Ah Victron Lithium SuperPack comes without any manual but according to specifications it should operate with:

- absorption voltage = 14,2V – 14,4V

- float voltage = 13,5V (Victron = 13.2V, AM Solar = 13.5V)

- max charge current = 30A (while MPPT 100/50 can deliver 50A, as it name suggests... it's nowhere mentioned/recommended in the manuals but for safety I have limited my MPPT's max charge current to 30A using Victron Connect app).


Question:

So which settings are "better"? Or maybe soome settings (like a higer charge voltage) are better for "performance" while other (lower charge voltage, disabled tail current) are better for battery longevity?


Source: https://amsolar.com/rv-solar/support

MPPT Controllersbattery chargingBMV Battery MonitorLithium Battery
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1 Answer
Justin Cook avatar image
Justin Cook answered ·

@Greg., this is a mixed bag. Generally speaking, you should always follow the manufacturer recommendations over any third-party seller's recommendations.

Follow Victron's published SuperPack specifications when charging: 30A maximum charge current, 14.2-14.4v bulk/absorption, 13.5 float. Set your MPPT accordingly, as well as any additional charge sources that you have. LFP banks don't need an absorption cycle, so there's no harm setting the absorption timer down to 1 hr or .5 hour... by the same token, there's no harm in leaving it at the 2 hour default for LFP batteries in the MPPT.

For the BMV settings, there's no harm in using AM's specifications over the default battery settings; the important bits are the Peukert Exponent and the Charge Efficiency, which are correctly spec'd in both Victron guidelines as well as AM Solar guidelines; tail current default to 2% is fine as well as temperature coefficient of 0.9% cap/F. The circumstances under which you actually need to modify those last two settings are rare, but there's no harm setting them just to dial in the accuracy of the BMV that last .09%.

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