Advice needed please Victron and gel carbon battery

[djgriff]

Hello, so i have hooked up a Victron 12/12 30 to a deep cycle Gel acid carbon battery (link) . I have setup the charging routine as suggested by the battery supplier and been on several long 3+ trips. Victron goes into float mode suggesting it is 100% charged.
So i just hooked up a battery monitor and 6 12v small LED light to test everything out and check the level of the battery and checkout the new battery monitor (Battery Monitor BM2 )
So when i first turned on the lights it stated the battery was 98%, great i thought. i then turned off the lights and hit the breaker switch. I then turned it all on again and it then stated 86%.. umm ok im thinking in a 1 min period 6 led light to loose 12% is crazy. So i did a repeat of the process, turned off the lights hit the breaker , reloaded the app. and boom agian 75% !? . So i did it again but it now continuously states 75%. Does this point to the battery being faulty or is the monitor likely to be faulty ?

Not sure where to go with this. I must add the monitor is connected to the fusebox entry point and then earthed to the battery through the fusebox return.

Really not sure where to go with this as the battery has been on several long runs and the battery goes into float mode, indicating fully charged. but then the monitor states 75%.. the victron has also kicked in to charging in absorption mode.

Any help would be greatly appreciated.

Thanks

Daniel

 

[t0mb0]

The BM2 is a pure voltage measuring device, as such it's probably good for long term steady-state SoC estimation but it'll be no good at all for estimating sudden/dynamic changes in SoC caused by active loads - you'd need a shunt (i.e. current measuring) based device for that. Having said that I wouldn't expect it to get so confused as to drop 14-25% from a light load - are you sure it's suitable for a gel battery?

The other (hopefully remote) possibility is that you actually do have a problem with the wiring somewhere and switching on those LEDs actually caused a significant current draw from somewhere. Do you have a clamp meter you could use to measure current out of the battery to check this isn't the case?

 

[t0mb0]

Also, just to check as I'm slightly confused by your description: " I must add the monitor is connected to the fusebox entry point and then earthed to the battery through the fusebox return.". Is the BM2 basically wired correctly across the positive/negative of the battery?

 

[t0mb0]

Might help to post some pictures just so we can see if there's anything obviously wrong.

 

[Dellmassive]

What @t0mb0 says...

Post some screenshots of the BM2 plots... For a 24hr veiw and a 7day plot.

Also some pics of your install.

 

[djgriff]

 

[djgriff]

Thanks for the info and advice, so its pretty straight forward setup from what i can tell.
Please let me know your thoughts as i am no pro at this stuff

appreciated

Thanks
Daniel

 

[djgriff]

What @t0mb0 says...

Post some screenshots of the BM2 plots... For a 24hr veiw and a 7day plot.

Also some pics of your install.

So I only have data for a couple days as just installed.. think i will attach it directly to the battery tomorrow. maybe it will be more stable

Many thanks

 

[Dellmassive]

Got a few BM2 screen shots.?

 

[djgriff]

So this is over monday and then the downward blip on the second pic is the lights just now
cheers

 

[djgriff]

Got a few BM2 screen shots.?

Can go and grab some photos/screen grabs, now if you like over a few min period to show the voltage drop if this helps?

 

[Dellmassive]

Well I'm seeing 13.0v constant across the 24hr period... So that very good and nothing to worry about.

As @t0mb0 says it's more about the long term trend and not the instant BM2 SoC reading.

Keep posting the 24hr plots.

 

[djgriff]

Maybe i need to invest in a proper monitor like the victron.. seems expensive though, do you have a recommendation for a good battery monitor for a leisure battery?
thanks

 

[djgriff]

Well I'm seeing 13.0v constant across the 24hr period... So that very good and nothing to worry about.

As @t0mb0 says it's more about the long term trend and not the instant BM2 SoC reading.

Keep posting the 24hr plots.

cool will do, appreciated guy. So basically its the wrong kind of monitor really for the job

Best

Daniel

 

[Dellmassive]

No the BM2 is an awesome voltage logger for battery state of charge over time... Ie 1day 7day 15day.

If you want definitive SoC readings and accurate power reading you need a current shunt.


The Victron smart shunt is the best, but there are cheaper version s like the Renogy shunt....


Ultimately a lithium battery will be your ultimate upgrade.

 

[Dellmassive]

More info here:

Battery Monitoring -- How I Done It --

Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...

www.t6forum.com

.

 

[Dellmassive]

And here.

Lithium LifePo4 12v Batteries - Time For An Upgrade?

Lithium Batteries are the future, (keep checking back for the latest news/edits) ************************************************** Dellmassive`s -- "how I Done It" -- Thread ************************************************** Kit List And Stuff -- How I Done It & What I Use --...

www.t6forum.com

.

 

[djgriff]

No the BM2 is an awesome voltage logger for battery state of charge over time... Ie 1day 7day 15day.

If you want definitive SoC readings and accurate power reading you need a current shunt.


The Victron smart shunt is the best, but there are cheaper version s like the Renogy shunt....


Ultimately a lithium battery will be your ultimate upgrade.

Awesome thanks man appreciated

 

[Dellmassive]

Your gel carbon battery is ultimately at sealed lead acid or SLA battery.

That means it is subject to voltage drop when you draw power... This messes up the soc readings on your monitoring.

Also being a SLA battery you can only use 50% of the capacity.... That means you can only use half of that 110ah.... So you have 55,ah to play with.

That means you can pull 1A for 55 Hours,

Or 10A for 5.5hrs.


Then your battery is done.


You have a good DC-DC charger though, that will help with the recharge.

 

[t0mb0]

Doesn’t look to me like anything is obviously wrong. It looks like coming off float voltage has just confused the BM2 slightly. I’d just live with it for a while, you’ll likely get used to any quirks soon enough and if you really think the BM2 is limiting you then you can upgrade if you need to.

Also worth seeing if there’s any settings on the BM2 you can tweak, I wouldn’t be surprised if a gel battery required a slightly different voltage/SoC curve.