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highfalutintodd avatar image
highfalutintodd asked

SmartShunt Resets to 100% - Need help with settings

Hi! I know this has been asked a few times but I can't quite seem to get the settings right and am hoping someone here can take pity on me.

My project is a full-sized R2-D2 astromech droid with a 24v 30Ah LiFePO4 battery. At the recommendation of a fellow builder, I bought and installed the Victron SmartShunt to monitor battery life remotely.

Unfortunately, as has happened to several others here, the SoC seems to reset to 100% after usage. I took R2 to an event a few days ago and watched the SoC drop steadily as the day wore on - all good. But by the time I got him back home, the SoC had returned to 100%. I DID disconnect the battery for transport, but I HAVE NOT charged him back up yet.

I'm sure I have a setting wrong but, being new to the world of robotics and batteries, I'm not sure which. I've included screenshots of the settings and the SoC dropping and increasing, below.

The battery is the Bioenno Power BLF-2430A.

Any help truly appreciated!


screenshot-2024-08-26-at-104118am.png

screenshot-2024-08-26-at-104027am.png


SmartShunt
screenshot-2024-08-26-at-104027am.png (746.7 KiB)
screenshot-2024-08-26-at-104118am.png (645.1 KiB)
screenshot-2024-08-26-at-104118am.png (645.1 KiB)
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4 Answers
pwfarnell avatar image
pwfarnell answered ·

When the battery voltage is above 26.4V and the charge current is below 0.3A (1% of 30) the unit will set to 100%, 26.4 is a pretty well discharged state so as soon as you reconnect it meets the reset to 100% criteria. You need to have the charged voltage setting above 100% charged ideally 0.2V below the voltage you charge at, say 28.2V if you charge at 28.4V.

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chrigu avatar image chrigu commented ·

Wheres the 0.2V below charge voltage from, is this just experience?

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derrick thomas avatar image derrick thomas chrigu commented ·
Yes this is from experience. The manual in section 7.2.2 explains this as being relative to the float voltage (as of revision 13 dated 2/2024), but in my opinion this should be changed. There are many many posts about this very topic. Having installed several systems and going from my own experience as well as others, this is one instance where you should NOT follow the manual.


Let the flaming begin!

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chrigu avatar image chrigu derrick thomas commented ·
In reality, those 0.2V go by quickly when charging, so if SOC is set to 100% a few minutes sooner or later doesnt really make a difference. At least to me
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derrick thomas avatar image
derrick thomas answered ·

Charged voltage is too low. Should be about .2 volts below bulk/absorption voltage which should be somewhere between 28.4 to 28.8 for most 8s 24v Lifepo4. Check the battery manufacturer specs for your battery.

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chrigu avatar image
chrigu answered ·

Youve set 26.4V as the charged voltage. Thats a relatively low voltage for that. SO anytime the battery recovers above that for three minutes (charged detection time) the shunt will reset to 100% SOC

If you are charging as per the datasheet to 29.2V, then i would set the charged voltage to that.

Personally, i would set 28.4V as the charging voltage, thats 3.55V per cell. Theres little energy left to charge from 28.4V to 29.2V but you probably gain battery lifetime. Only question is the balancing, its possible that it only starts above 3.6V per cell, but the datasheet doesnt answer this sadly.

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highfalutintodd avatar image
highfalutintodd answered ·

Thank you all for your responses. If I'm reading everything correctly, it sounds like I should set Charged Voltage in SmartShunt settings to 29.0V since my battery's charging voltage is listed at 29.2V.

I'll do this, test it out, and report back.

Thank you, all!

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derrick thomas avatar image derrick thomas commented ·
What are you using to charge the battery? This matters when adjusting the shunt settings.
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highfalutintodd avatar image highfalutintodd derrick thomas commented ·

This:

https://www.bioennopower.com/products/29-2v-10a-ac-to-dc-charger-anderson-for-24v-lifepo4-batteries-bpc-2410a?variant=8152938610789

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derrick thomas avatar image derrick thomas highfalutintodd commented ·
Make sure the charger negative is connected to the system side of the shunt and not the battery. The only thing connected to the negative lug of the battery should be the shunt, and nothing else.
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chrigu avatar image chrigu derrick thomas commented ·
The battery seems to have a plug for charging and a second for discharging. I guess the shunt is on the discharging plug with the rest of the robot.


It should still reset to SOC 100% if the charge detect voltage is reached, but it will not track the Ah charged like this

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highfalutintodd avatar image highfalutintodd derrick thomas commented ·

Sorry, can you go into a bit more detail on this, please? Why is this the case?

The battery doesn't have lugs - it has separate Anderson Powerpole charge and discharge connectors directly connected to the battery:

screenshot-2024-08-26-at-122837pm.png

Are you saying I need to split the Powerpole cable from the charger and have the positive going to the battery and the negative going to... somewhere on the system side of the shunt?



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chrigu avatar image chrigu highfalutintodd commented ·

The shunt is designed to be the only device connected to the battery negative. Everything else like loads and chargers need to use the negative pole of the shunt instead of the battery.


One of the neat features of the shunt is that it measures the energy both ways, down and up, so the SOC should be pretty accurate even when not finishing charge cycles fully. But this only works if the charge current also passes trough it. If the charger is connected to the battery directly, the shunt can not measure that current, and the SOC will only reset to 100% once the battery reaches the charge detection voltage

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