Peukert Exponent

[William_Foster]

I have had a few issues with the electrics on my Mk5 Scout (nothing major) and have been researching a few bits and pieces.

In the VictronConnect set-up there is a setting for Peukert Exponent, I really don't understand it to well after reading about it on the internet, but what I learnt was that for lithium systems it is usually set below 1.10 and nearer to 1.25 for AGM batteries.

Mine was set to 1.08 by the factory which seemed a little low, so I wrote to Fullriver (the maker of the DC105-12 batteries included by standard in my dual battery set-up) and was told that the Peukert Exponent should be set to 1.20.

Just thought I would share in case others were looking at the same thing.

I'm not sure how much of a difference it will make in calculating the discharge rate.

[Nomadic]

The higher the loads on your battery the more impact the Peugeot factor will have but with the changes you have made you it’s an extra 10% loss.

What is your charge efficiency setting at? The charge efficiency of LA or AGM is pretty poor so you need to put a lot more energy into your battery than what you take out in order to get it back to 100%. This is the main reason I am a LiFePo4 convert. We only have a limited number of sunlight hours in the day so we need to make the most of them.

[William_Foster]

Thanks for the reply Nomadic.

The charge efficiency is set at 95% (I have attached a photo of my settings page), which is the setting that was set by Track Trailer.

I can't see a charge efficiency on the Fullriver website (http://www.fullriverbattery.com/product/batteries/DC105-12), but I could ask them; they got back to me quickly last time.

When you say I will get an extra 10% loss, that is theoretical isn't it? The VictronConnect system just reports on the battery but doesn't control them?

[Nomadic]

Thanks for the reply Nomadic.


When you say I will get an extra 10% loss, that is theoretical isn't it? The VictronConnect system just reports on the battery but doesn't control them?

Sorry wrong choice of words in my reply. By making the change your Victron will now be correctly recording the amp hours going out of the battery. It’s not an extra physical loss but the Victron will correctly show that you have less AH remaining if that makes sense.

The 95% for charge efficiency is probably about right. Some manufacturers claim better but that is in an ideal world conditions. Most are well below that and it gets worse as the battery ages. If You used 100 amp hours overnight then you need to put back in 105 amp hours to get it back to 100%. That’s assuming a charge efficiency of 95%. Your Victron will do all the calculations for you if set up correctly. After a couple of years you probably want cut it back to 90% if you find that performance is dropping off.

[Smallfry]

Thanks William

Learning all the time, mine was also set at 1.08 so have changed to 1.20 to see if any effect

As an aside I received 2 new updates (Photo's attached, hopefully)

Also attached are my Status & History - Appreciate any comments on setup

Rob

[Smallfry]

History

[William_Foster]

Thanks for the assistance Nomadic, it is greatly appreciated.

Smallfry, I would love to provide some valuable feedback on your settings, but I can't other than to say they are the same as mine now I got those updates as well, but I must say I have no idea what the new Battery Starts Synchronised setting actually does, but it was nice to receive so that I know my system is up to date.

I really like the functionality of the VictronConnect, I can see the status of my TVAN batteries on my home computer anytime. I have a Redarc type system in my Hilux which I think I should swap over to the VictronConnect as it does give you a lot more practical information in an easy format.

[TimH]

The "Battery Starts Synchronised" just means that when the Victron is first powered up it defaults to showing that the batteries are fully charged (100% SOC) even if they aren't.
This is instead of waiting for the first synchronization. After the first full charge it will synchronize and get its head straight.

Depending on the Efficiency and Peukert settings, the State of Charge shown on the Victron can be slightly inaccurate so over several charges and discharges the error can creep up.
Victron gets around this by doing a synchronization when the batteries are fully charged, which resets the SOC to 100%.
It figures the batteries are fully charged by measuring the battery voltage, seeing when the charge current drops to a low value for a set length of time (all of these values can be changed by the user).
It sometimes gets confused and does a synchronization too early (more likely when charging by solar). So I do an occasional manual synchronization when I am charging up via 240V just to get it back in sync.

I have a couple of Lithium batteries in mine which are a bit harder than AGMs to figure out when they are fully charged, since the battery voltage doesn't change much.

The Victron has been good to use when I have been trying to work through some charging problems. I can get some great graphs on the PC showing what's happened during a charge/discharge cycle.
I'm using a windows PC so I have to attach to the Victron via a USB cable which is a bit of a nuisance.
I assume you have a Mac home computer? Do you connect to the Victron via bluetooth or do you connect to it another way?
Tim

[William_Foster]

Thanks for the information on the 'Battery Starts Synchronised' Tim.

Yes, we have a Mac and iPhones and connect to the Victron via bluetooth.

I didn't know you could connect via any other way except bluetooth.  It came standard with my Scout, we never thought we would use it but we do quite regularly when out and about; especially when driving long distances to ensure all is going well with the fridge.

I am interested in your mention of graphs, I haven't seen any graph options; I just get screens like SmallFry posted.

[TimH]

The graphing is done by using the BMV Reader software, from Victron, on a PC.
It shows similar information to the iPhone app however it also has the capacity to capture the readings every few seconds and dump them into a CSV file that Excel can open.
From this table of info you can graph the readings you are interested in to get a better feel for what is going on over time.
This method only seems to work with using a USB cable plugged into the Victron and into the PC.
I bought the special USB cable from a Victron reseller for around $20 I think. 

It's all a bit awkward since its hard to get to the back of the Victron to swap the bluetooth cable over to the USB cable (and you lose the bluetooth link while using the USB).
However it does produce some very useful info if you are chasing obscure faults.

It would be easier if you could do something similar via the bluetooth but haven't found a way yet.

I agree that being able to check where the battery charging is up to via the phone app is excellent. Saves opening the Tvan up for a look.
Tim

[Smallfry]

Tim,

Might need to talk to a knowledgable Victron dealer, I downloaded the Windows app and it connects via Bluetooth, but I haven't got any further

Rob

[peter_mcc]

Does the monitor store data that you can then download via a Windows PC or do you have to be recording it "live"? If it stores data, any idea how much?

[TimH]

It looks like it depends on catching it live.
You can set how often it grabs the current figures but that’s all.
Tim


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