What's new
Van's Air Force

The definitive Van's Aircraft support community! Buying, building or flying an RV? Join our exclusive family of mentors and enthusiasts!

Low Voltage Warning Etched Circuit Board Modification.

R

Rjmvmi1998

Active Member
I have one of the early AeroElectric Connection Low Voltage Modules installed in my plane. I want to try and modify it. I installed EarthX batteries and as you know the resting voltage is around 13.5V. The LVM was designed for lead acid batteries and doesn’t engage until it detects 13V indicating the alternator is off line. My understanding of the EarthX batteries is at 13V they are already substantially depleted.

I would like to modify my LVM to activate at 13.5V. Attached is the Schematic and parts list. Can someone explain which which component detected the 11V and can that component be replaced with one that detects 11.5V.

Auxiliary Battery Management: The AEC9005-101/102 LV Warn/ABMM kits features an open-drain, power transistor rated at 2.0 amps and configured to automatically close an auxiliary battery contactor or relay whenever bus voltage is greater than 13.0 (26.0) volts.
 

Attachments

Check - perhaps your buss voltage dips down below 13vdc when you have a load on your fully charged battery (as in normal flight) and the alternator trips off.

Carl
 
Carl Froehlich said:
Check - perhaps your buss voltage dips down below 13vdc when you have a load on your fully charged battery (as in normal flight) and the alternator trips off.

Carl
Click to expand...
Hi
Put a diode in the buss voltage supply the .6 volt drop will mean the unit triggers approx.6 volt higher

Thanks
K
 
All good ideas. I meet with an older retired friend who work in the broadcast business for many years designing and fixing circuit boards. He instantly was able to make since of the schematic, ran some calculations and determined changing the R105 resistor from a 10.5k to a 12k should change the trigger to 13.5 volts. He even had the resistor in his tool box. I’ll install it and report back my findings.
 
Rjmvmi1998 said:
I have one of the early AeroElectric Connection Low Voltage Modules installed in my plane. I want to try and modify it. I installed EarthX batteries and as you know the resting voltage is around 13.5V. The LVM was designed for lead acid batteries and doesn’t engage until it detects 13V indicating the alternator is off line. My understanding of the EarthX batteries is at 13V they are already substantially depleted.

I would like to modify my LVM to activate at 13.5V. Attached is the Schematic and parts list. Can someone explain which which component detected the 11V and can that component be replaced with one that detects 11.5V.

Auxiliary Battery Management: The AEC9005-101/102 LV Warn/ABMM kits features an open-drain, power transistor rated at 2.0 amps and configured to automatically close an auxiliary battery contactor or relay whenever bus voltage is greater than 13.0 (26.0) volts.
Click to expand...
For R104 You might try 2.37K Be sure it is 1% or better!
That should change the trip Voltage to 13.5 to 13.6

Rolf
N9EY
 
rolf said:
For R104 You might try 2.37K Be sure it is 1% or better!
That should change the trip Voltage to 13.5 to 13.6

Rolf
N9EY
Click to expand...
Hi I've reran the calcs and Rolf's answer above is correct for a LV trip of 13.5 - 13.6 volts however R106 should be 2.37K R104 set's the Zener reference current and won't change the error voltage on pin 2.

Changing the top (R105) resistor from a 10.5k to a 12k as per Rjmvmi1998 changes the LV trip to 14.6 !!!

Inserting a diode (1n400X) in the supply line will also raise the trip point to 13.6 to .7 volts without messing with the PCB it can be fitted in the D sub sell enclosed in heat shrink.

Thanks
K
 
Last edited:
kms001 said:
Hi I've reran the calcs and Rolf's answer above is correct for a LV trip of 13.5 - 13.6 volts however it should be R106 should be 2.37K R104 set's the Zener reference current and won't change the error voltage on pin 2.

Changing the top (R105) resistor from a 10.5k to a 12k as per Rjmvmi1998 changes the LV trip to 14.6 !!!

Inserting a diode (1n400X) in the supply line will also raise the trip point to 13.6 to .7 volts without messing with the PCB it can be fitted in the D sub sell enclosed in heat shrink.

Thanks
K
Click to expand...
K and Rolf,

Thank you for taking the time to run the numbers. I will defiantly try changing the resistors you recommend. My plane is to change the resistors and hook it up to a DC power supply, change the voltage until it triggers, hopefully close to 13.5. I will make to sure to post my results. Again, thanks for your help. This is just a project for me to see if it can be done. I hate having a system in an airplane that doesn’t work even if it’s old tech. My engine monitor will alert when the voltage drops below 13.5 volts.

Robert
 
Rjmvmi1998 said:
K and Rolf,

Thank you for taking the time to run the numbers. I will defiantly try changing the resistors you recommend. My plane is to change the resistors and hook it up to a DC power supply, change the voltage until it triggers, hopefully close to 13.5. I will make to sure to post my results. Again, thanks for your help. This is just a project for me to see if it can be done. I hate having a system in an airplane that doesn’t work even if it’s old tech. My engine monitor will alert when the voltage drops below 13.5 volts.

Robert
Click to expand...
Hi it's only one resistor R106
K
 
You must log in or register to reply here.
Back
Top