Battery Drain

emjga

Member
T6 Pro
Folks

Had this setup for the last 2 years and have not had any issues but in the last 6 months noticed the leasure battery was flat in the monring

Setup
2 X TNE12-100 , AGM 100 amsp, two batteries so giving a total of 200 Ah

Fridge CR-0050 Waeco

Solar panel 325 Watt with Victron mmpt 100/30

Simple BM2 battery monitor that only showed %

So recently installed Victron Smart shunt 300 amps

Made sure battries where 100% full from both the Shunt and BM2
Disabled the mmpt so no charge was going to the battries.

Turned the fridge on to Setting 3
Current 4.45A , Power 60W
1 Fridge Output.webp


Then left it until approx 11pm
Noticed the Shunt and BMI where down to 10% ,should not have been anywhere near that

If my run time calculation is correct
Hrs = Battery Capacity Ah X Volatage / Consumption W
40hrs = 200Ah X 12 Volts / 60 Watts

I know AGM should only be distarged to 50% so dived by 2
Gives a run time of approx 20hrs

At this point I tured the fridge off and MPPT on (It is night so dont expect it to charge)

In the morning I checked the shunt graphs
2 shunt votlage ssems to take a dive at approx 12 midnight.webp
As you can see the voltage is going down as expected , however at approx 9pm it ssems the voltage just drops off a cliff and repidly drops from 12.77V to approx 11V

So not sure if the issue is with the fridge just deciding to consume all the power or if the battery's are the issue.

Is there a better way to test this or anbody has any thoughts , would be very welcome.
 
Something else must have turned on too as the extra load onto the battery.

That's a fair drop on an AGM. So just have been a good few amps extra.

What else have you got on the leisure batteries bank? Heater? Other chargers? Split relay?
 
There are
Heater turned off
Inverter turned off
Light / control panel , turned off

The only thing on was the fridge

Going to try a different test

All off except the lights / control panel and see what the result is
 
Can you show the 1 day BM2 battery plot as well?
 
Can you show the 1 day BM2 battery plot as well?
1 Day would be not enouge to cover yeaterday but have a 7 day plot.

Red line shows approx when I started the test

Screenshot_20250808_132309_Battery Monitor.webp

Screenshot_20250808_132324_Battery Monitor.webp
Red Line shows 10am start of voltage drop

Which seems to be the same as the Victron Shunt , so in a way good news that they are both showing the same result.
 
I've just had exactly the same thing. Only had the (empty) fridge on and all was fine. Fridge set to low power.
'Something' has happened and the battery has freaked and drained very quickly.

Screenshot_20250808-141343.webp

I've got a new battery in and seems to be doing okay with minimal drainage - admittadly its getting slightly topped up with solar..
 
Did another test but this time only with lights and a invertor using a 4w house lamp

Turned off Solar at 1.18pm , Shunt Votage 13.65
Left it for 1 hr just to make sure it was stable at 2.18pm , Shunt volatge 13.3V

Lights on Shunt 13.28V , 1 amp , 14 watts

Left it until 3.30pm
Dont think the lights on its own is going to generate enough load or take to long.
So started Inverter and turned on a house lamp with a 4 Watt LED bulb
Shunt 3.6 amps , 46 watts
Should give a run time of approx 26 hrs

Came back just after 4.30pm
The graphs look ok

However just before 5pm the Graphs went rapidly downhill
Screenshot_20250808_165238.webp

This would sugest to me that I have a battery issue ?

As it is the same as what I saw using the fridge as a load device

When I orrigional looked at batteries , I just could not afford LiFePO4 but think it was a mistake not to go down this route
Any recommendations on LiFePO4

Anybody know anything about Frogstar Drift
I live in Scotland and do get away in the winter off grid
I do have a heater and use it but the batteries are in the back of the Van , heater is under front seat.

Would need 200Ah
Is it better to have 2 smaller batteries like , 2 X 100Ah
Or could get 1 larger say 300Ah , size would fit but the weight could be fun tryin get 26Kg though a rear hatch
 
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looks like that battery bank is goosed. . . .

shows a voltage but has no capacity.

id say replace with Lithium - but thats my thing.

look at ROAMER, FOGSTAR, RENOGY for a start as good known brands.


take a look here:





.
 
1 Day would be not enouge to cover yeaterday but have a 7 day plot.

Red line shows approx when I started the test

View attachment 298691

View attachment 298693
Red Line shows 10am start of voltage drop

Which seems to be the same as the Victron Shunt , so in a way good news that they are both showing the same result.
Your battery seems to be showing below 9.0V on 08/06 and 08/07 - So I'd say the batteries are trashed.

Simon
 
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id say replace with Lithium - but thats my thing.
Lithium would be my choice , knowing what I know about AGM batteries now (Which is not a lot )

The following I think will work with minor adjustments
DC DC Victron Smart Charger 12 12-30A
Solar Victron MPPT 100/30

My concern would be the CB516-3 which is used for Mains hook up , not used very oftern

In the past I was using the CB516-3 as trickle charge but was not happy with it and got the Victron DC DC Charger installed
The company that fited the DC DC charger disabled the trickle charge.

The cb516-3 manual
General Information - CBE ENERGY CB516-3 User Manual [Page 7]

Selector switch B would give Bulk 14.4V , Float 13.8V
Which would seem to match the Frogstart 300Ah Specs but I have been cought out before on this.

Frogstar Spec 300Ah
  • Absorption charging voltage: 14.2V - 14.4V
  • Float charging voltage: 13.5V - 13.8V

Looking at the Frogstart 300Ah as a single battery
Size would fit in , weight of 26Kg will be fun to try and fit
 
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The Victron smart chargers are customisable like the smart shunt and smart MPPT's. It's not a massive outlay (compared to a big LiFePo4) for the ability to set it perfectly for your battery of choice.
 
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The CBE516 does not have a lithium setting. It’s easy to disconnect and remove (that’s what I did with mine). If you want a mains charger I’d recommend the Victron ip65 to match your other kit. It’s silent as it has no fan and can be installed so it’s easily removable to use on other vehicles. I have put the cable (with QR connection) in for mine but not installed the charger as solar covers my needs. I’d also recommend an Ablemail AMT12-2 to keep the starter battery topped up from the leisure battery while camping or leaving the vehicle unused or extended periods.
 
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I know there are two versions of cb516

Cb516
Cb516-3

As far as I can tell Cb516 does not support AGM / lithium

However CB516-3 does support
Think I might have a talk to frogstar and see what they say
 
Just found this


The CBE 516-3 is a different matter because it has a desulphation phase and I would not leave this model connected to a lithium battery

Sounds like need to go and replace it.
 
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