Odd Connext Screen Start Voltage issue

[lazergeek]

Since I replaced my start battery with an LFP Dual Purpose last year I’m having a weird issue. With the ignition on or engine running its reports the start battery voltage is just fine. If I turn off the ignition before the screen shuts down, it reports 0.8v and sometimes the low voltage alarm will come up before the screen shuts off. If I immediately turn the ignition back on voltage goes back to normal as soon as the ignition is back on.

I thought maybe it was the BMS causing or the DVSR since it’s engaged by my ignition switches, so I checked my Shunt voltages when this happens, and the start battery voltage does not drop at the shunt after I Turn off the ignition.

Any thoughts or ideas?

 

[FSH 210 Sport]

Since I replaced my start battery with an LFP Dual Purpose last year I’m having a weird issue. With the ignition on or engine running its reports the start battery voltage is just fine. If I turn off the ignition before the screen shuts down, it reports 0.8v and sometimes the low voltage alarm will come up before the screen shuts off. If I immediately turn the ignition back on voltage goes back to normal as soon as the ignition is back on.

I thought maybe it was the BMS causing or the DVSR since it’s engaged by my ignition switches, so I checked my Shunt voltages when this happens, and the start battery voltage does not drop at the shunt after I Turn off the ignition.

Any thoughts or ideas?

Did this problem begin directly after changing to the dual purpose LFP batteries?
I can’t remember when you made up your relay system for your DVSR, did you do that before the dual purpose LFP batteries as well?

 

[lazergeek]

yes since upgrading the Start battery last fall is when I started getting the low voltage messages after turning off the ignition I never paid attention to the voltage reading before then however. I also replaced by Shunt at the same time as the old shuntone never fully recoverd from getting wet last summer.

I did the Ignition DVSR Mod andHouse LFP batteries 2 years ago.

 

[FSH 210 Sport]

yes since upgrading the Start battery last fall is when I started getting the low voltage messages after turning off the ignition I never paid attention to the voltage reading before then however. I also replaced by Shunt at the same time as the old shuntone never fully recoverd from getting wet last summer.

I did the Ignition DVSR Mod andHouse LFP batteries 2 years ago.

Well, that’s quite interesting.. what’s the voltage on the connext when the keys are on and the engines are off?

I’m also wondering what could be going on with the relays down in the head compartment.

 

[lazergeek]

Both batteries showed 12.8v when I initially turned on the ignition yesterday morning. Before starting. They were in the 13v range the rest of the day when I looked with the exception on when the engines were running then start batter was 14 volts from charging.

I was thinking of disconnecting the delay harness to see what the behavior is next time I'm at the boat.

 

[FSH 210 Sport]

Both batteries showed 12.8v when I initially turned on the ignition yesterday morning. Before starting. They were in the 13v range the rest of the day when I looked with the exception on when the engines were running then start batter was 14 volts from charging.

I was thinking of disconnecting the delay harness to see what the behavior is next time I'm at the boat.

Okay, I was wondering if one of the relay contacts was hanging up a bit, perhaps voltage decay on one of the coils is slow, or is somehow back feeding in as the voltage drops away. Again, can’t remember how you wired them, where did you pick up the ignition hot source from?

 

[lazergeek]

The ignition is powering the coils in the relays which adds 12v to the red wire in the DVSR. The shunt is not seeing the voltage drop from the start battery when I turn the ignitions off

 

[FSH 210 Sport]

The ignition is powering the coils in the relays which adds 12v to the red wire in the DVSR. The shunt is not seeing the voltage drop from the start battery when I turn the ignitions off

Correct, and the shunt is independent of the ignition hot relays and the ECU / Connext screen which gets its inputs from the ECU’s I think. Not sure if the connext screen gets voltage direct from the batteries but my understanding of the connext screen is that it is display that is fed its information from the ECU’s via the port tachometer…

 

[lazergeek]

I tried to troubleshoot this today but I can't find the cause of the issue. All wiring checks out. Disconnecting the relays for the DVSR .side no difference. Start battery circuit has full voltage with the ignitions off.

At this point other the then the occasional brief low voltage after shutting off the ignition before the connext turns off I wound think this was normal