question

guardcompany avatar image
guardcompany asked

Draining Battery?

My setup:

  • Victron SmartSolar MPPT 75/10
  • 100 Panel on the vehicle roof
  • Odyssey Group 31 battery.
  • 10 gauge wire on the PV and Battery side leads with a 10a fuse on the positive battery lead.
  • No load connected


When the vehicle is in the garage I use a CTEK (Odyssey approved) charger. So the vehicle normally leaves the garage with a full charge. I will drive to the store and turn the vehicle off with a fully battery (around 12.8/9) and look on my VictronConnect app that I am getting PV. I will come back a short time later (20 mins) and my battery is at 12.4 which shows both in the app and also in a separate volt meter I have installed. What in the world is going on?

battery chargingbatteryerror
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3 Answers
Charlie Johnson avatar image
Charlie Johnson answered ·

On the surface, it sounds like your battery may be at the end of its service life. That said, ehe answer is in your Victron Connect app.

What is the battery chemistry; flooded, AGM, thin plate pure lead AGM, gel or something else?

While driving to the store, how much charge current do you observe on the Victron Connect app?

What is the SOC of the battery when you shut down the vehicle?

What is the charge current being provided by the PV panel with the vehicle shut down?

What is the SOC of the battery just before you start the engine?

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guardcompany avatar image
guardcompany answered ·

It's only a 2 year old Odyssey AGM Group 31. I did some testing today:


1. Plugged in CTEK jumped to 14.6 and then dropped to 13.49 and sat there on float for a day (24 hours)

2. Started up vehicle and backed out of garage to full 2pm sun. Panel was showing 80W PV in bulk mode and the battery for a second (1 second) jump up to 15.0v then back to 14.7 (my preset absorption mode setting) and 10 watts PV and to absorption mode.

3. Turned off car and after about a minute it went from absorption mode to float mode.

4. After about 15 mins battery is holding at 13.6v (my preset float setting) and in float mode. PV is showing 3W.

5. Drove around and parked and went into store for 20mins. Stayed at 13.6w on float. Got home at parked and it went from Bulk > Absorption > Float in about 20 mins. Floating at 13.6 now. Only interesting thing is it was only at 12.8 to 13.11 during Bulk and then when it switched to Absorption it went straight up to 14.7v. Is this normal? Bulk is a lower voltage?

I'm going to leave it in the driveway for the rest of the day to see if I get the crazy voltage drop after being on float for a couple hours.



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Charlie Johnson avatar image
Charlie Johnson answered ·

Certainly looks like the system is behaving. What happens when you put a load on the system while charging via PV?

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Related Resources

VictronConnect VE.Bus charging manual  

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