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battery capacity

Battery capacity - 8 lithium 100Ah 12V

Battery capacity - 8 lithium 100Ah 12V so about 9000+ watts. Fully charged in the evening 13.5V on the panel. The only consumers are the fridge and freezer, that jointly use 85 watts so by the morning 700 watts have been used and I should have 8300wats of power left but the voltage is now 13.0V -

andy744 asked
nickdb edited ·

1 Answer

5 batteries 3 + 2 or 5?

I am installing an ESS with a Quattro 48/8000/110. I have 5 Pylontech 3000C (3.5kW) batteries to connect via a Lynx 1000 distributor. Should I connect as one big 5 battery bank or as 2 (a 3 battery bank and a 2 battery bank)? And why!

Thanks in advance for your answers.

Cheers ... Manor Farmer

manor-farmer asked
manor-farmer answered ·

2 Answers

Syncing Multiplus and Shunt SOC

My Victron shunt and Multiplus are showing 2 different SOC readings. The shunt is showing 100% but the 24/3000/70 is showing anywhere from 70-80% SOC. I have programmed the shunt to know that the battery bank has 412aH @ 24v nominal.

How do I know which reading is accurate, or if either of them even are correct at all?

love2learn asked
trevor-bird commented ·

1 Answer

Three Battery Banks Walked Into A Bar…


Hi all! I really apologize if this is a stupid question. I have looked all over the Q&A section

of this website and have not been able to find the answer but I am a newbie.

I’m trying to build a pretty uncommon set up. Three battery banks. 2 x 2p16s packs running nominally 102v (powering Elco EP-70s) and a 2p8s pack running 24v (House and HVAC). Ugly whiteboard drawing attached for your amusement. Anyway, I would like to send all the BMS data from all three packs to an MFD via Victron. Cerbo GX or Venus seem capable but seem like they can only see 1 DC power source(?). I am sure I am missing something here…

(Since I am planning to use a 150 x 3.2v LiFePo4 prismatic 302Ah cells I need a BMS which can monitor that large number. I am planning to use REC BMS and will attach a diagram they provide on their website for your enjoyment. I am open to suggestions of a more elegant solution).

Thanks for your help!!


matthew-greer asked

0 Answers

Evaluate battery capacity, again

There were some discussions on battery capacity evaluations but they did not really answer my question/concerns.

I have 16 CALB Lifepo4 prismatic cells 400Ah connected in series to get 48v. So, nominal capacity is about 20kWh. Battery is 7 years old (time flies!). Batteries promised 2000 cycles for 80% DD. This is a good manufacturer and their batteries were tested before to deliver this promise. 2000 cycles is about 7 years. But I never went that far down. My typical DD 25-49%, not more. So, I should expect some life in the battery

I want to expand my total storage capacity. I try to evaluate remaining capacity to understand: is it worth to add a similar battery pack in parallel or I need to build a new system with new batteries.

All methods with "charge to 100% and then discharge to 50% or 20%" don't work for me. They are impractical. I live off-grid from this battery charging from solar. I need energy for the house, and charging is not up to me - it depends on sun. It is not so easy to discharge 10-16kWh in one go, and if I do it then there is a chance I might not be able to charge it back as there is no sun.

Hence, the only way for me is a natural experiment and observations.

I assume that Multi derives SOC based on the voltage, and Multi knows that I use Lifepo4 battery. So, if I collect SOC and consumption numbers from VRM portal, I might be able to get some idea of the remaining capacity.

For example, SOC after sunset s1 = 98.5% and consumption so far is c1 = 4.9kWh. Then I check the same parameters next day before sunrise, s2 = 66% and c2 = (7.61+3.48) = 11.09kWh as there are two days.

Estimated capacity should be (c2 - c1) / (s2 - s1) = (11.09 - 4.9) / (0.985 - 0.66) = 19.0kWh

I tried this approach several times for different SOCs and time periods and I got numbers around 19kWh. If SOC is low or time interval is short, then estimation might be lower, e.g. 18kWh. Sometimes it is higher, e.g. 20kWh. But most time it is very close to 19kWh.

Could you please comment on this approach and reliability of my estimation?

19kWh looks good, it might make sense just to add another 16 cells in parallel and use them for the next 7 years.

timbo asked
snoobler commented ·

0 Answers

Battery size with AC & DC coupled system

Hi there!

I am thinking about a AC and DC coupled system.

- a 5kVa fronius inverter on ACout 1 (with 6 kwc PV)

- a 5kVa multiplus 2

- 9.6 kWh LFP pylontech batteries (4x us2000c)

- a mppt charge controler (with 3 kWc PV - dc coupled)

So my question is:

In cas of grid failure, is my battery size(9,6) big enough to deal with the 6 kWc PV coming from the 5 kVa Fronius Grid inverter combined with the 3kWc DC-coupled PV array? (Am thinking about the 1:1 rule)

Thanks a lot in advance


law asked
Alexandra answered ·

1 Answer

Minimum specification for Phoenix 24/5000 inverter.

Is the minimum 400Ah 24v pack recommended in the manual for the Phoenix 24/5000 inverter based on lead acid battery chemistry?

Would I be correct in assuming that as LiFePo4 chemistry has more than double the usable energy of lead, that a 200Ah 24v LiFePo4 would suffice (with a BMS of 1C continuous / 3C for 1s burst) ?

dion-patelis asked
gonzalor commented ·

2 Answers

Idc Invert much higher than IOut?

Hey guys I'm pretty new to all of this- but it seems wrong that I'm getting a reading of 95 amps as my Idc invert but only 20.2 amps as my IOut. I would've figured those two would be closely matched.

So when calculating how many hours I should be getting out of my battery should I be using the 95 number or the 20 number? And if those shouldn't be so different, how would you trouble shoot that?

ggk1 asked
ggk1 answered ·

2 Answers

Are my SLA batteries ruined?

I've had them for almost two years. They are generic alibaba type SLAs. It seems like the capacity is getting really bad, such than the SOC is more than 25% off compared to the rated capacity. I never let them go lower than 60% according to the original SOC calculation. I'm not in an area with a lot of daylight hours currently. They're supposed to be 12v 250AH SLAs, and I have 4 of them in a 24v configuration to be 24v at 500AH. Here are my graphs and charge/BMV settings, as you can see it goes to 24v at like 80% SOC. 100% SOC sync happens when the batteries are getting like 300watts. Midpoint looks okay so shouldn't be a bad cell. Is there anything I can do aside from halving the BMV amp hours?




vulture asked
vulture commented ·

2 Answers

Multiplus Compact Alarm on cold mornings?

Hi all, I have been using a secondhand Multiplus Compact 1600VA 12V for 5 years, with errors every now and then. I take this to be a good run for a secondhand product, but it would be a pity to replace a good piece of gear unecessarily.

On cold mornings (<5degC) the unit wont start, and the Alarm LED light up with no pre warning code. When the day warms up, the unit will start, but makes a loud vibration noise!

Also, sometimes after running for 5 hours or so continuously with a moderate load, the unit will go into alarm mode. In these cases, the battery voltage is still good (e.g. yesterday at 13.4V). I can only think this is due to overheating? The load is never near max (1600VA).

My setup is a Victron Multiplus Compact 1600VA 12V. I only have two LiFePO4 90Ah 12V batteries wired in parallel. These are about 6 years old. I also have a Digital Multicontrol Panel but only use it as a remote control for the inverter. I have a Smart Solar 100/50 hooked up and running throughout the day.

My theories are:

1) the unit is no longer tolerant to extemes of temperatures.

2) I need to hook up the temperature sensor that I never installed?

3) My battery bank is of too small capacity for this size inverter?

4) There is some internal component that is failing

Any ideas? The charger circuit still works fine.

Any way to dignose the error? I think I have a USB connector somewhere...

staf-ivory-smith asked
staf-ivory-smith commented ·

0 Answers

Upgraded battery. How to see the capacity changed?

We recently upgraded doubled our battery pack from 10.5KW to 21KW.
But at this point we are not 100% sure if we installed it correctly. Feels like we didn't gain much.

Is there a way to see the battery capacity in VRM or Victron Connect?
Just to double check. Or are there other ways to validate?

We have now 6x polytech us3000c modules connected with Cerbo GX.
Below a picture of our System
Here you can see our Public Dashboard:

Thanks for the help


dave-hakkens asked
dave-hakkens edited ·

5 Answers

Understanding what "BATTERY 100%" really means - 100% yet still shut down low voltage

Hi All.

i have an all Victron off-grid system

48-5000-120-100-120V Inverter

MPPT-150 charger

Cerbo GX + Display

Victron DC shunt

(3) SimpliPhi 3.8 batteries @ 48V

I posess a basic knowledge set regarding electricity and such. i "designed" and installed this system myself - and it has performed flawlessly and to the specs which i targeted ...

QUESTION: What does "100%" mean ?

Can anyone explain (or point me to an article or treatise) that explains what the Cerbo Display unit is telling me as it relates to the "ACTUAL" status of my battery supply -

this morning i awoke early - just in time to hear a click and my entire system switched off/went dark...

(i subsequently figured out that my well pump had malfunctioned and run all night - fixed that problem promptly)

hmmmm. unplugged from my Victron system and dusted off my gen set so i could muddle through breakfast

as sun crested the horizon my Victron system started to "wake up"

one it had awoken - the display Showed 43.7 V (low) yet it also said "100%" in big happy numbers...

As i sit here and type this it is happily recharging, Voltage back up to 52.1V and its packin in 20A from the MPPT.

I can be awfully stupid - but i always remind people that i'm not as dumb as i look -

In the past i recall the %percentage%" battery level goin up and down with loads and charging -


how am i to understand batteries that are basically depleted low voltage (down to 43%) yet my fancy Cerbo Display is showing me an unwavering "100%".

What am i missing ? is there a way to understand this or is the display or shunt borked?

i would really like to be able to "trust the display" when it proclaims 78% that i actually have 78% of my usable Ah avail for all my fancy off grid amenities...

any thoughts or redirects to a knowledge base would be greatly appreciated


/Steve (Panda_North Photon Collective)

panda-north asked
panda-north commented ·

3 Answers

80% battery at 10.99V

I have three 100ah AGM batteries in my campervan. I've used them for 2 years.

(also a 390w solar panel, victron mppt and battery monitor)

Recently, staying in Portugal with high temps, although I've reached 100% battery each day, by morning I'm at 75 or 80%. My fridge tries to start up, runs for a few seconds then stops. When this happens, it takes my batteries from 12.17V to 10.99.

When there's enough light on my solar panel the fridge runs fine.

Being agm batteries, I can use 50% of their capacity. Its frustrating to be at 80% but still not have a working fridge!

Would new batteries help? I don't recall having this problem before, so I'm guessing they just aren't holding their charge as well as before.


missy asked
missy commented ·

1 Answer

How does this not ruin a Start Battery?

In this design example, a Sterling DC to DC converter is used to charge a lithium house bank with the Start battery as the "Source". So for example, if we are charging the Lithium Bank at 60Amps over 3hrs, how is this justified when a Start battery is not designed to provide high current over a long period of time?


ve-user asked
pau1phi11ips edited ·

3 Answers

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