Are Victron Smart batteries the right choice?

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Darlene asked Mar 10, '24

Are Victron Smart batteries the right choice?

I need to replace a bank of SLA (AGM) batteries in my home solar set-up after 2 years, as they have not proved to be as robust as the manufacturer claimed. My system consists of 4.5kW solar, MPPT VE Can 250/100, Multiplus 48/5000/70-100, and eight 135aH 12v AGM batteries (in a sunny region). I thought that the batteries would be ok if discharged to 50%, but in reality that probably seldom happened, if at all, and they are now, after 2 years, not capable of running 2 fridges and a freezer overnight on hot nights. I have the possibility to switch over to the grid, but ideally want to be independent, and so I'm looking to replace those batteries with 2 Victron 25.6v 200aH LiFePO4 Smart batteries in series, with a Victron VE.Bus BMS V2. I don't want to buy these items only to find that I'm once again doing the wrong thing. They would need to power a laptop (ca 50w) for max 6 hours after sunset, and the above-mentioned 2 fridges and 1 freezer for max 12 hours in warm-hot weather, a bit longer in cooler weather, but then the fridges/freezers aren't on as much. High current-draw appliances, like aircon, heater, stove have individual switches that allow them to operate from the grid if I choose, and so they are grid-run after sunset. I charge an EV at max 15amps (240v) during the day, but ONLY at whatever the sun allows; if the batteries are called upon for EV charging it is only momentarily, if a cloud causes a brief dip in available sunlight, and it's usually not more than 50% of what the car is charging at. I really want to be conservative with the batteries, and take no more than a third of what they are rated to deliver each night. My question is: am I making the right choice in buying these batteries? Will I get the maximum cycle life advertised by using them in this fashion?

The MPPT is currently set to charge at max 30amp, and the Multiplus, if the charger is enabled, at 100amp. I've seen in the Multiplus settings, under the heading "Lithium Batteries", that the batteries I'm considering need to be configured using VEConfigure and the VE.Bus BMS Assistant. Is this configuration self-explanatory, i.e. are all the values readily available, or do I need to find this information somewhere?

Finally, I'm aware that lithium batteries are sensitive to overcharging. Should max charge be capped at 3.2v per cell? The batteries will be depleted to some degree every night - should I indeed be setting the max charge to 100%? I've read several times that they should only be charged to 90% for max cycle life. But how would they balance if they are never charged up fully? Perhaps charge them fully once a week, and otherwise stop charge at 90%? That would be 2.88v per cell.

Thanks for taking the time to read. I'd really appreciate some guidance before making such an expensive investment.

smart lithium

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Answer 1 · 2024-03-10T05:58:10Z

duivert answered · Mar 10 at 05:58 AM

Hi i have no experience with victron smart batteries, but why not use pylontechs? Better cycle life with up to 90% dod, cheaper and no need for extra bms, setting up is easy pylontech bms sets right settings itself

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Answer 2 · 2024-03-10T08:07:47Z

Darlene answered · Mar 10 at 08:07 AM

Thanks for the suggestion. I've not heard that name before. I'll look into it. I've noticed not every type of battery is available here in Australia.

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nickdb ♦♦ commented · Mar 10 at 08:08 AM

They are definitely available in Aus.

The compatible batteries are listed here:

https://www.victronenergy.com/live/battery_compatibility:start

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Darlene nickdb ♦♦ commented · Mar 10 at 09:32 AM

Thanks....just checked it out. They are indeed available. Don't know why they haven't cropped up on searches before.

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Answer 3 · 2024-03-10T08:36:15Z

Sarah answered · Mar 10 at 08:36 AM

Hi @Darlene I’ll start by saying that the shift from agm to lithium is monumental! The batteries charge faster and can discharge to 10% capacity without a hiccup. . Are the Victron smart lithium batteries good ? I believe so, i have 4 x 200 A/H 12 volt batteries on my boat. Running for two years without any degradation in performance. Are there better ? Probably. But when you start to mix and match the components everything becomes more difficult. Having good monitoring and a system that is end to end compatible is in my view essential and this is where Victron excels (I have a lynx bms and cerbo as well as two victron mppts and a bunch of other Victron stuff). Springers also are having an Easter sale with some great deals at the moment.

Also you can tweak the charging settings but you really don’t have to - smart lithium setting is fine - especially with Victron as the setting are designed for the smart batteries. It’s also worth noting that when you are using lithium there is virtually no relationship between voltage and state of charge as the batteries will hold the voltage until they are almost depleted. Very very different to agm.

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Darlene commented · Mar 10 at 09:31 AM

Thank you, Sarah. I also see a benefit in matching components, and Victron products have proved to be very good so far. Their EV charger removed all the headaches we had with the Wallbox charger that came with the car! I just want to make sure the two 25.6v 200aH batteries are enough to keep my fridges going at night.

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Answer 4 · 2024-03-10T10:48:27Z

Darlene answered · Mar 10 at 10:48 AM

What is the purpose of a Cerbo GX? I don't have one at the moment. The Pylontech batteries, with internal bms, apparently require them, but the Victron smart batteries that need an additional bms don't. What would happen if I use Pylontech batteries without a Cerbo?

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kevgermany ♦♦ commented · Mar 10 at 12:25 PM

Cerbo does a few things. It's a central coordination and control, reporting point for the system.

Here it would take feedback from the BMS and control the charging of the multiplus, solar etc. It also provides online reporting via internet and Victron's VRM portal. Also on your phone via Bluetooth. It can drive a display screen (GX Touch 50 or 70).

Super piece of kit, it can also take and integrate data from other devices, tank sensors etc.

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duivert commented · Mar 10 at 12:18 PM

For the pylontechs you will need a cerbo, otherwise the system will not work

A cerbo is like a central hub, everythings connected to it an controlled from there

For more info on a pylontech setup:

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

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kevgermany ♦♦ duivert commented · Mar 10 at 07:27 PM

Pylontechs will work without a Cerbo. But you lose many features.

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duivert kevgermany ♦♦ commented · Mar 10 at 08:49 PM

@kevgermany ah thank you didnt know that!

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Answer 5 · 2024-03-10T11:51:44Z

klim8skeptic answered · Mar 10 at 11:51 AM

@Darlene I just want to make sure the two 25.6v 200aH batteries are enough to keep my fridges going at night.

You might want to quantify how much energy your 3 fridges use during a 24 hour period.

And how much energy your PV can capture for the same period.

My energy use for the last 30 days with a single efficient 2 door FF. At high ambient temps. Only FF, GX device and inverter charger running.

30-day-energy-use.png (75.0 KiB)

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nickdb ♦♦ commented · Mar 10 at 11:57 AM

A++ or A+ appliances are really efficient.They draw very little

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Answer 6 · 2024-03-10T12:11:42Z

Darlene answered · Mar 10 at 12:11 PM

I could probably locate some data for one fridge and the freezer, but the second fridge came out of the Ark, and all I know is it uses more than the new ones. Any labels it may once have had are sure to have vanished.

Over the past two years there have only been 2 or 3 days where cloud cover is so dense that I've needed to run the house on the grid during the day. Normally plenty of light. It's now sunset-sunrise that is the problem with these batteries that have not taken the rigours I've exposed them to. Hot nights neat the equinox mean too much drain on them. I can't imagine the fridges and freezer would use more than 3kWh during the night. Theoretically 2 lithium batteries 25.6 200ah should do it....but having been burned by the first battery purchase I'm cautious now.

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Alexandra ♦ commented · Mar 10 at 06:24 PM

A battery is as good as it's back up when it is lithium.

Just be sure the supplier is good at warranty stuff (and customer care) and has spares (supply line or stock) for the product.

The BMS (Battery Management System).handles the cell management and with a GX and DVCC (and correct programming) overcharge should not happen. I see you mention it in your post as a concern. They self manage.

Victrons batteries want to be fully charged about once a month to keep on top of cell balancing. Other batteries like pylontec start balancing from 90% SOC.

If you already had a GX in the system you would like @klim8skeptic be able to look at your consumption. You can always add to the bank a bit later if needed anyway.

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