battery voltage drop

[New Comer]

I noticed that when I use my secondary battery (12v) for things like a small heater, the voltage dropped from 13.1 to 12.1. Then, when I use a bigger wattage heater, it dropped from 13.1 to 11.7. I mean the wattage will drop when running the heater. Once I stop using it, the wattage goes back. My question is if I continue to bring down the wattage to 11.7 by using the bigger heater, will it hurt the battery? Does the batter have to be always in 12 v or above to stay healthy?

By the way, I am very new to this topic and won't get upset if you try to inform me. 

 

[MrAlvinDude]

Part of the processes inside a battery are chemical processes. And for lead acid batteries these processes are somewhat slow/sluggish, so when you stop using power, the chemical processes will catch up, and the voltage will somewhat go up again.

In this text there is talk about how "aging" (sulfation) of a lead acid battery happens in two stages.  https://batteryuniversity.com/index.php/learn/article/sulfation_and_how_to_prevent_it
First stage: soft-sulfaction, and second stage: hard-sulfaction.

The soft-sulfation being called reversible (by fully re-charging the battery) and the hard-sulfation being mentioned as permanent degradation of the battery (happens when the battery has a lower voltage than its ideal voltage of 13.5 to 13.8 V - and happens faster the lower the voltage is, for any prolonged time).

So to keep a lead acid battery as healthy as possible, for as long as possible, means to keep its low-voltage time as short as possible.

Thus I would say it is more important to get the battery re-charge as soon and as much as possible, rather than trying to keep it above 12V at all times (like under heavy load).

I would also say that it is more important to get the battery to hold a voltage above 13.5V  a couple of times every week,  rather than keep it above 12V when it is under heavy load.

 

[highdesertranger]

heating anything with electricity is very inefficient. you don't notice in a sticks and bricks because electricity is so cheap. there is no way you are going to run an electric heater off of one battery for any length of time. unless it's like a 8D. highdesertranger

 

[New Comer]

heating anything with electricity is very inefficient.  you don't notice in a sticks and bricks because electricity is so cheap.  there is no way you are going to run an electric heater off of one battery for any length of time.  unless it's like a 8D.  highdesertranger

This is very true. I have two Ms. heat buddy. But my wife is so afraid of it that she won't let me use it. 

 

[jonyjoe303]

The more watts your device uses the quicker it will drain the battery. 1000 watts at 12.7 volts uses 78 amps, but once your battery goes down to 11.7 volts those 1000 watts will use 85 amps. The lower voltage battery will put out more amps at lower voltage to maintain the 1000 watts  As the battery voltage goes even lower it will use even more amps.

A good youtube video to watch is "lithium battery test versus gel" , on this test they test 3 batteries a 100ah lithium, a 100ah lead acid and also a 220ah lead acid, they use a 2600 watt load(heater) and run it until the the heater shutsoff from low voltage. The lithium voltage drop to 11.7 volts and was putting out 285 amps(lasted 21 minutes), the 100 ah lead acid voltage drop to 10.2 volts and was putting out 325 amps(lasted 6 minutes), the 220 ah lead acid battery drop to 11 volts and was putting out 305 amps(lasted 13 minutes). The lower the voltage the more amps it used, you need a large lead acid battery bank to keep the voltage high.

When you turn off your heater, your battery should be reading at least 12 volts, if it reads less then that, your draining it too much. If the battery gets down to 11.5 volts or lower without load and you don't recharge right away it won't last long. I destroyed my agm by taking it below 11 volts about 3 times. The sweetspot is not to take the battery below 12.1 volts(no load), it will last years.

If you can't use the mr.heater, add more insulation. The more insulation, the less you have to run your electric heater, you can run it on the lowest setting for a few minutes every once in a while.

 

[Ticklebellly]

......a small heater, the voltage dropped from 13.1 to 12.1. ......... a bigger wattage heater, it dropped from 13.1 to 11.7.

A simple example of Ohm's law.   The larger heater draws more current, hence more voltage is dropped across the internal resistance of the battery, the heater element, and the connecting wires.    When the load is disconnected, the terminal voltage at the battery is very close to open circuit voltage. What you observed is as it should be. Increased battery life degradation is linked to the voltage of a rested battery and its open circuit terminal voltage. The open circuit voltage of a rested battery can be used as an indication of the state of charge of the battery. Drawing down a battery to low voltages is what does the damage to life expectancy of a battery.

 

[tx2sturgis]

The lower voltage battery will put out more amps at lower voltage to maintain the 1000 watts  As the battery voltage goes even lower it will use even more amps.

{snip}

The lower the voltage the more amps it used

This is true when a 120 v space heater is run thru an inverter powered by batteries, but it's not true if the heater is a 12v heater powered directly off the batteries, such as one of those 12v 150w windsheild defroster heaters or one of those 12v 400 watt auxiliary cab heaters.

I'm not sure what type of heater the OP is using...is it a 120v heater powered with an inverter, or a small 12v heater?

Or maybe the OP has a propane RV furnace using a 12v blower?

:huh:

 

[tx2sturgis]

Either way, the power to run an electric heater in a vehicle has to come from somewhere....either the engine electrical system or the solar-charged or genset-charged house batteries.

 

[New Comer]

This is true when a 120 v space heater is run thru an inverter powered by batteries, but it's not true if the heater is a 12v heater powered directly off the batteries, such as one of those 12v 150w windsheild defroster heaters or one of those 12v 400 watt auxiliary cab heaters.

I'm not sure what type of heater the OP is using...is it a 120v heater powered with an inverter, or a small 12v heater?

Or maybe the OP has a propane RV furnace using a 12v blower?

:huh:

I am using the 120 v 400-watt heater.