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monstreruk avatar image
monstreruk asked

Victron 500A Smart Shunt - setup questions

Hi All,

I am relatively new to campervan setups, and I do not have a background in 12v electrics.

I have had a Victron 500A Smart Shunt installed in my campervan, which I am really pleased with on first inspection.

There are a number of options in the Victron Connect app to allow configuration of the Smart Shunt, here are those settings.

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Even after looking in the manual, I am not 100% sure what many of them mean, and whether the factory default settings are correct for my specific battery.

I have already changed the Battery Capacity setting to be 110AH to match the battery, but I am not sure about the rest of the numbers (Tail current, charge floor and so forth) in relation to my specific leisure battery.

Question 1

The battery fitted is a brand new 12V 110AH Xtreme AGM Leisure Battery (XR1750) NCC Class A . I am hoping someone on here can either confirm that the default settings are fine, or give me an idea as to what they should be?

Question 2

When I know the battery is 100% I want to click the "Synchronise" button (I am not sure the installer did this). My question here is, do I need to wait for the battery to be at rest (so the voltage has settled), i.e. a couple of hours after dark, or can I just click it during the day when it is in "float mode" (when the voltage would be higher)?

Many thanks for the information.


SmartShuntmonitoring
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monstreruk avatar image monstreruk commented ·

Thanks @Stefanie, that is most helpful.

Quick follow up question. For my battery (AGM Xtreme XR1750) is the Discharge Floor value of 50% correct for this battery? I was under the impression that AGMs were happy to discharge a little lower than 50%, but I dont know in all honestly.

I also found this information on my battery (the Xtreme XR1750), not sure it that helps with any of the settings. If not, I shall go with your previous recommendation on the Peukerts Constant!

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Many Thanks for your help!

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ monstreruk commented ·

Sorry, no idea about the Discharge Floor for your battery. That is something you must ask the battery manufacturer.

I don't know of any AGM that qualifies for discharge floor below 50%. The Victron AGM deep cycle are rated for 50% (I had them myself and they still perform like new even after 6 years).

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monstreruk avatar image monstreruk Stefanie (Victron Energy Staff) ♦♦ commented ·

Thanks for the reply @Stefanie

I will keep Discharge Floor at 50% then on that basis, I guess its only an indicator anyhow (in terms of calculating the % remaining), so that setting wont actually impact the operation of anything.

As for the Peukert exponent, I found this useful site. https://www.batterystuff.com/kb/tools/calculator-for-load-specific-run-time.html and entered in the numbers I found for my battery (see my previous post). The calculated Peukert exponent for my battery comes out really close to your recommendation!

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Thanks again for your help and advice.

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ monstreruk commented ·

Good find. I'll keep that link for the calculator in my bookmarks.

As said, you should ask your manufacturer for the 50%. If they are not deep cycle batteries, then 50% is way too low and will significantly reduce battery life.

If that's not acceptable for all the loads you're running, then there are other options like topping up PV to make sure the batteries don't get below 75%.

And a word for discharge floor in general:

Lead acids like to be topped up to 100% on a daily basis. Let's suspect your batteries allow for 50% and it takes a week to get to that point, that's IMO not acceptable and also will reduce battery life significantly.

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2 Answers
Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @monstreruk,

you may want to change charged voltage to something like 13.8V to prevent the Smart Shunt to synchronise too early. It will auto synchronise once charge voltage reach 13.8V AND tail current is less than 4% of the overall capacity. So that's 4.4A.

And you may als have to play with the Peukert exponent, which comes into effect when discharging the battery. From my experience for AGM, especially when new, ~1.10 is a good starting point.


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seb71 avatar image
seb71 answered ·

Keep in mind that the "discharge floor" from the shunt settings is only used to estimate the "remaining time" displayed by the shunt. It will not stop the discharge of your battery.

So set it to the value you are normally willing to discharge your batteries to, but limit the discharging by other means (cut-off voltage setting in the inverter in your case; battery BMS settings in some cases; minimum SOC in case of ESS systems).

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monstreruk avatar image monstreruk commented ·

Thanks @Seb71 - I 100% understand your point, its only a an input into calculating the "time remaining" and does not actually do anything!

My question was probably poorly worded. I was trying to determine if the default 50% number was the correct "safe discharge point" for my battery without negatively impacting battery life / performance. Or whether it was safe to discharge a 12V 110AH Xtreme AGM Leisure Battery (XR1750) NCC Class A to a lower percentage? Main thing for me is knowing how low it can safely can go, without causing any battery damage - I can then set an alarm well ahead of that percentage!

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seb71 avatar image seb71 monstreruk commented ·

Apparently that battery is rated for maximum 600 cycles at 50% Depth of Discharge.


Don't go below 50% SOC (50% DoD).

If possible, don't go below 70% SOC (30% DoD).


On the other hand, it's a single 12V 110Ah AGM battery. Not that expensive. When it does worn out (loses capacity), you have an excuse to get a LiFePO4 battery instead.


PS

I don't know what are you doing, but your battery links do not work for me.

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