Martin avatar image
Martin asked

Victron 160AH Lead carbon batteries

Hi I've seemed to have lost a lot of capacity in my battery bank 8x 160 AH Victron lead carbon, they were new in mid 2019 so just over 3 years old, the BMV has recorded 104 charge cycles and 507 full charges ( sync to 100,%) our average discharge is 107ah, we now get a low voltage warning around 80ah, basically we have to run the generator in the evening to get something like 90% change if the solar hasn't got it above 90% or we end up with low battery warning in the morning or shutdown with voltage about 38 volts, the battery settings are hopefully in the picture below with the history page.

I've spoken to my dealer he's essentially said out of warranty and buy new lithium! I'm off grid so totally dependent on the battery bank, I've checked and cleaned all the terminals my next option is possibly removing 4 of the pack and getting them tested and charged with mains power to see if they are still usable, interested to know if this is normal for 3 year old batteries or if something is setup incorrectly?

EasySolar All-in-OneHelplead-acid
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klim8skeptic avatar image klim8skeptic ♦ commented ·

Your deepest discharge is 321Ah. Not good for a bank rated at 320Ah.

Your other stats, Ave discharge, Cumulative Ah drawn, Charged/Discharged kWh all indicate a battery bank that has been utilized to the max.

Time for some new batteries.

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Martin avatar image Martin klim8skeptic ♦ commented ·
Hi thanks for the reply, that 321ah discharge was over a long period (7 to 10 days) at low current, the batteries were nearly new and didn't drop below 42volts, at that time we didn't live on the site and didn't have the solar setup, during winter we normally max out at 160AH to 170 AH, the data is roughly 790days worth with 507days getting 100% full charge, 104 charge cycles, Victron's battery spec stats 500 full discharges to 42v (10.5 ea), for the vast majority of the past 2.5 years 20% to 30% (10%in peak summer) is the normal discharge, it's only the last 6 to 8 weeks that the voltage drops, stat of charge hasn't gone below 60%+

A £1000 a year in batteries, is probably still cheaper than mains but way off the minimum 5 years life I was hoping for, 1000 to 2000 cycles and 10 year life claims seem like a fairytale, what's 450kg of scrap batteries worth £50??

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pwfarnell avatar image pwfarnell commented ·
What settings do you have for tail current and charged voltage in the shunt for synchronization of SOC to 100%, the default figure of 4% is too high and synchronises before the batteries are full. The same question can be asked of your charger settings, what determines the end of absorption and the switch to float, are the batteries being fully charged to 100% before swapping to float.
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3 Answers
kevgermany avatar image
kevgermany answered ·

Might be worth checking your charging setup. The max voltage looks rather high.

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Martin avatar image Martin commented ·
Thanks for the reply, The max battery voltage recorded is a bit of a mystery to me, it's been at 59.33 volts since the BMV was connected, it's never been set that high and the highest I've ever seen when charging is about 57volts, the "charged" voltage setting was at 55 volts from original setup until about a year ago Jonnas B did a BMV video and recommend slightly lower I think 54.5 volts? The Victron data sheet gives 14.1 volts (56.4)Max , I've put it up to 55.5 volts and capacity has improved a bit, the batteries are indoors and never go below around 14°C.

We've got a 10kva (Kubota) it gets used mainly in winter and once or occasionally for big power tools, welder, plasma cutter etc, I've never connected anything like that to the inverter, just domestic stuff, 2 x 3kva easy solar so not even huge inverters.

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kevgermany avatar image kevgermany ♦♦ Martin commented ·
The question is, are the settings giving misleading readings or not?

When charging in solar, generally higher charged voltage is needed, somewhere close to absorption, because of the effect of clouds during charging. On AC, charged voltage is usually set around the float voltage, both relying on tail current to confirm state of charge (SOC).

If the monitor does not recognise a full charge regularly, drift errors accumulate and mislead.

Datasheet gives 14.1-14.4 absorption, 13.5-13.8 float. It's also not clear how long you've spending in absorption. When charging, absorption voltage only indicates around 80% SOC, hence the tail current setting for confirmation.

For future, you might want to check charge efficiency setting lead carbons are much better than AGM and would normally justify 90-95% and Peukert can be reduced as well.

Also bear in mind that battery voltage drops under load, voltage readings for state of charge are misleading unless the batteries have rested for quite a while. Starting a charge because voltage drops to 12V under load (48V in your case) is not needed. Voltage will recover once load goes.

Suggest you reduce charged voltage to the float range, and set tail current down to 2% to achieve a full synchronisation. This will give a better indication of the battery condition.

The downside is you will be running your generator for an extended period at low load. But a full synchronisation once a week will be enough.

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Martin avatar image Martin kevgermany ♦♦ commented ·

Thanks for your advice, hopefully a picture of the settings screen is attached? The tail current was set at 4% until last week, charged detection time was at 5m?

I will chage the figures to your suggested values.You said "reduce" the peukert figure, what do you suggest?

We've got 3.8kws of solar fitted currently and I've got another 4.8kws to put up, hopefully in the next few weeks, with the 2x 150/70 mppt's, I think we are then nearly maxed out?

We got kinda forced off grid due to the cost to connect, it's literally 30mts from my boundary to the nearest pole, but now in the UK you need to have provision for car charging, the price is ridiculous, Planning for the house has just been passed, so this whole system will get replaced, hopefully the 2 easy solar's and batteries can be somehow included in the new setup?

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JohnC avatar image
JohnC answered ·

Hi @Martin

Given you're in the UK and approaching winter, how cold are your batteries? Pb's drawn down to say <70% SOC and at <10 degC are pretty much useless at holding V under even small loads. And the lab ratings won't be done down there either. So they may still be ok if this applies.

That said, I agree with @klim8skeptic that you've worked them pretty hard. How you should treat them is opinion though. My own opinion (flooded pb).. 80% the preferred min low SOC, 75% is panic level. I once reached 70%, and my shunt hasn't registered a single cycle since installed some 3+ years back (I think it uses 65% to register a cycle). And I never finish the day <95% (genset then). Hate seeing them below 48V with light load, and don't care what they get down to with heavy load. Note that 48V/light load is only ever reached in winter. 5.5 years old now, and behave like they did when new.

Yeh, my mother always told me to behave better. Took me a long time to learn, but I do now (at least with my batts). :)

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kevgermany avatar image
kevgermany answered ·

These BMV 712 settings work well for me with Lead Carbon.


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kevgermany avatar image kevgermany ♦♦ commented ·
Note that I have a mix of solar and grid charging, almost all grid at the moment in South of England. In summer I increase charged Voltage to about 28V.

As @JohnC said/implied, it's about tuning the settings to match your system and usage.

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