Voltage Cut Out Level And Module

[Dieseldonkey]

Having recently installed an AGM battery under the drivers seat, I'm considering installing a voltage cut out unit in some of the low power circuits such as cabin lighting. I've found a few devices on eBay but wonder if anyone has used any or could recommend one from elsewhere.

Also what's a sensible setting for the cut off voltage, with respect to keepIng an AGM battery in tip top condition for as long as possible.

 

[t0mb0]

If you want voltage as a proxy for state of charge, it’s unlikely to work very well. When something heavy’ish, e.g. fridge, kicks in the voltage will naturally drop under the load and potentially cut out your lighting unnecessarily.

I think you can buy battery protector gizmos which will cut all access to the battery when voltage drops but I’ve no idea how well these work in practice.

 

[Dellmassive]

a nice little chart on this page. . . .


but i seems the answer you are looking for is:

12.3v cut off (50% soc) for max life of the battery

11.8v cutt off (0% soc) as absolute minimum before battery damage.




State of Charge Sealed or Flooded Lead Acid battery voltage Gel battery voltage AGM battery voltage
100% 12.70+ 12.85+ 12.80+
75% 12.40 12.65 12.60
50% 12.20 12.35 12.30
25% 12.00 12.00 12.00
0% 11.80 11.80 11.80

Battery voltage and state of charge - Energy Matters

 

[t0mb0]

I think that 12v’ish is pretty safe to cut off at but 12.3v could be problematic - mine can drop to 12.3v under load even in decent state of charge.

 

[mmi]

I just installed CTEK Smartpass 120 for the same purpose. It has a separate output for “non-critical” consumers which will be switched off at low voltage. As it has somewhat intelligence I’m hoping to avoid the potential premature cut outs referred above. The manual states that it cuts out when voltage falls below 11.5Volts – and reconnects when back above 12.0 Volts. So hoping the company has done some real life experiments on that.

SMARTPASS 120

Anyway, need to wait till winter to have some real experience how it really fits the purpose.

 

[Dilbert]

If you want to go solar, the Victron SmartSolar Charge Controllers with load output (MPPT 75/10, 75/15, 100/15, 100/20) do the same and you can programme the cut off voltage for the load output using their app. More info here in their datasheet: https://www.victronenergy.com/uploa...ller-MPPT-75-10,-75-15,-100-15,-100-20-EN.pdf