Settings for lithium batteries

DIY
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1

I’ve recently migrated from lead acid to lithium batteries.
I have a diesel generator feeding a Multiplus 24 3000 70 and 4x300ah lithium batteries. It’s powering a house 230v.
The setup is working but there’s a few settings I’m not sure of.
I had hoped to upload the settings here but I can’t see how to do that so I’ll list the ones I need advice on:

The charge efficiency defaults to 95% but I read somewhere that it should be 99% for lithium. What should it be?
It seems to default to 14.2V for charging but the battery manufacturer recommends 14.4 + or - 0.2v. Should I change it?
It’s set to turn on the genny when battery goes down to 20% and to stop charging 10mins after 95%. I read somewhere that it should be 20% to 80%; any reason not to change it and why the 10 mins?
Is there somewhere I can upload the settings file and get it checked?

Finally, when I set it up first I mistakenly put the battery capacity at 1200ah instead of 600ah. Do I now need to remove the batteries, charge them fully and set it up from scratch so the system reads the % correctly or can I just leave it as is?

Really finally; there’s also some solar panels and a solar charge
controller which feeds direct to the batteries without going through the multiplus. Is this correct? Seems to me that the Multiplus will have no way of knowing what the % charge is with this setup.
Thanks

2

The easiest way in my opinion to publish settings is to access the settings in VictronConnect, take a screenshot (often this means pressing POWER and VOL DOWN at the same time) and posting that pic. That way we get to see a lot of info in one shot.

The reason for “95% + 10 min” might be (i’m not an expert, but i’ve seen a lot of BMS versions) that many BMS’s (battery management systems) only “top balance”, i.e. during a charge cycle they wait until the flat part of the charge vs voltage curve is finished, and then put a little more power into the low cells to bring them all up to the same voltage. This takes time (only a very small current, over thin wires, is used to do this, so it can take some time), so if you chopped off the charge as soon as you got to 95%, the BMS would not have enough time to do much balancing.

The number of Ah (i.e. capacity of the battery bank) is only relevant for shunts to calculate the SOC, so if your MultiPlus is getting its SOC directly from the battery (i.e you have a comms-capable battery, and a data cable goes from your GX device to the BMS), then the MultiPlus already knows the correct capacity.
If you have a Victron shunt, and therefore the shunt is watching the current going in and out, and adding/subtracting from the presumed capacity, you can reset this info in VictronConnect ; Open VC, select your shunt, click the gear wheel, and enter the correct capacity. Now the shunt knows the battery capacity, but it has no idea if the true SOC right now is 0%, 100%, or somewhere between. So now you need to either enter the SOC, or wait until the battery is 0%, or 100%, and reset the SOC at that time.
Its not going to make any difference to the running of the system or efficiency, but it will make a big difference to whether the genny turns on/off at the correct time.

The Multiplus is not in charge of tracking the SOC - this is the shunt or BMS’s job, but you are correct in that unless there is a shunt somewhere that is “seeing” the mppt’s power going in, there is no way to know the SOC. Remember though - the MPPT has a shunt, as does the bms, so in a setup where there is no external shunt but there is a battery with a BMS, the BMS will be “seeing” every input and output, as the shunt is just in front of the cells, so its not possible to charge/discharge without the shunt seeing that current. The Victron GX devices have very clever code that gets the topology of a system right almost every time, and it can do the math required to accurately calc the power flows. This is what you see in the dashboard diagrams, even without doing any config.

3

To answer a couple of the direct questions.

The charge efficiency should be 99%.

The lithium preset is for Victron lithium batteries and these are at the lower end of the typical range at 14.2V. It may be best to go with your actual battery manufacturers settings.

Just reset your Ah capacity to the correct value.

When you have solar panels it is best to have a shunt on the batteries unless your batteries have communication.

4

Thanks for the settings.
My batteries don’t have communication. As far as I know the Multiplus I have doesn’t have any wireless capability. Surely the Multiplus already has a shunt in it so that it detects state of charge? Can a separate shunt not just monitor the state of charge but also tell the multiplus when to turn the generator on and off?
This is all new to me

5

I hate to be dumb but how do I actually post a screenshot?
victron settings 13 1 25.TXT (1.8 KB)
Is that right?

6

A shunt measures state of charge by measuring the power going in and out of the batteries so the Multiplus only accounts for power going through the Multiplus. If you have separate direct DC chargers or loads the Multiplus can not measure these.

1 Like
7

Just to clarify, my batteries have BMS to prevent them over or under charging but the BMS does not communicate.
I don’t know where My multiplus is getting the SoC from. Initially I charged the batteries to 100% and inputted that to the Multiplus but I don’t understand how the Multiplus is tracking it. Is it aware of what the batteries are getting direct from solar or not? Should the output from the solar charge controller go through the multiplus somehow so that it can be measured?
Yes, the SoC will be crucial to controlling the gennie, so will a separate shunt deal with the solar input and if so, how does it communicate that to the multiplus so that the gennie does what it should.
Thanks for the reply
I’m new to all this.

8

so I can’t put the power from the solar through the Multiplus?
the shunt is separate to the multiplus. Does it tell the multiplus the soc so that the multiplus can switch the gennie on or off? How does it comm with the Multiplus?
Does a BMV do the same thing?

9

Usually there would be a GX in the system, then information can be shared with components.
Otherwise each component does what it is programmed to.

You don’t need a separate shunt for anything, just one that does battery SOC. The bmv 700/712 has a relay that can be used to start a generator based on SOC.
The rest of the system will work on voltage.

basic flow 
graph TD
    DG[Diesel Generator] --> MP[Multiplus 24V 3kVA]
    MP <--> BusBar[Bus Bar]
    MPPT[MPPT] --> BusBar
    BusBar <--> Shunt[Shunt]
    Shunt <--> Battery[Battery]
10

Thanks @LX
I’m trying to understand why I need a separate BMV. The Multiplus already tracks the soc based on the gennie input and the inverter output. Surely all I should need to do is somehow connect the output from the solar controller to the Multiplus so that it adds this into the equation when calculating the SoC. The Multiplus already has a relay that starts the genny based on SoC.
Can the output from the solar controller be directed through the Multiplus?

11

No, you can not.

12

So I need a BMV?
There’s no GX in the system

13

For best accuracy you need a battery monitor. As an extra you could get a GX device so this is shared with the Multiplus. However, as mentioned above you can have a standalone BMV to measure battery SOC and use it to start and stop a generator.

14

I have a 24V easysolar hooked up to a 8x 3.2v lithium set via a daly bms. 270a/h

Also in there is a victron shunt as I only have solar. Have never used the gennie even when I had the lead acid batteries.

My lithium settings are as follows.
Any changes to charging oatameters can be done by going into ‘expert mode’

Effeciency is 99%
Peukert is 1.05

In order for it all to communicate its via the apps.
I only need to have the location on and bluetooth. In my case I really need to know what I take out and put back in again.

My float is 27.2
Absorption 28.4

Fully charged batteries are 27.2 resting.
Mine rarely go below 80%, but recently I purposely took them to 30%. That took over 2 days .
Only because i felt I had an issue with one of the batteries.

Hope this helps

15

Thanks for that.
I can see how to set the efficiency, the float V and the absorbtion V but I can’t see where I can set the bulk V and the Peukert.
At the moment the victron is charging them at 27.5v but the manufacturer recommends 28.8v.
How do I set the bulk (and the Peukert)?

16

Thanks,
I can see how to set the absorbtion and float voltages but not the bulk voltage; how do I set that?

17

Victron chargers do not have a setting for bulk, bulk ends when the voltage climbs to the absorption voltage. Bulk is when the charger is delivering max amps and that is the limit and voltage is below absorption.

Peukert is in the battery monitor not the charger.

18

Thanks pw,
Trying to get my head around the implications of that.
For long life I have read that I should charge the lithium batteries between 20% and 80%.
Is this the same as ‘State of charge when bulk is finished’ 80%?
I have also set one hour absorbtion once a week.

19

The quoted % figures are SOC. For lithium SOC will probably be higher than 80% at the end of Bulk maybe 90-95% if the charge rate is small compared to the battery bank size. The only way to tell is to watch a charge and see.

Personally I do not worry about the 20-80%, there is a lot of urban myth and most experienced/ professional users on here do not do this, have a search, it is mainly raised by DIYers. The key is not to leave them on 14.4V charge when full, make sure the charger drops to 13.5V or below.