12v to 13 v dc

[SimonTHK]

Hi

I need battery lead acid to act like it delivers 13v instead of 12v. Take in mind, that I dont want it to deliver more than 12v to load, but I need to manipulate a battery indicator to think it delivers more voltage, like 1-2 more volt.
I cant change the battery indicator, and I has quite alot of these I need to manipulate thinking it delivers more.
The problem is, that the manufacturer of the battery indicator, tells me that the battery is empty at 12,5v, and that is for sure and in practical use of a lead acid battery, not at all correct.

Can it be done?
Coils doesnt work with DC right? I am on rock bottom here.

Thanks in advance

 

[schmitt trigger]

Use a charge pump to increase the apparent voltage.
Then divide that voltage to the "correct" ratio using resistors.

I don't know if the 7660 charge pump IC will work at 12 volts, but otherwise you can use a 555. There are plenty of circuits on the web using the 555 as a charge pump.

 

[MikeMl]

How about**broken link removed**There are several makers of similar products who primarily target the Ham market.

 

[tcmtech]

Stick a 1.2 volt nicad in series with your 12 volt battery.

 

[ronsimpson]

battery indicator

We need to know what a "battery indicator" is.
Send pictures or data or .........
**broken link removed**
this?
You want it to read higher?

 

[SimonTHK]

We need to know what a "battery indicator" is.
Send pictures or data or .........
**broken link removed**
this?
You want it to read higher?

Yes that is a battery indicator. In this case, similar indicator is shown on a screen, for me completely impossible to change. But I guess it still reads from a positive wire from the battery.

 

[ronsimpson]

Idea:
1) go inside the battery indicator and change a resistor. (probably can't)
2)Can you get a 6V indicator? Get a "Zener Diode" and put it in the (+) wire of the indicator. This Zener Diode will eat up some voltage.
Example: Zener Diode = 5.1V When the battery is at 12V the indicator will see 12-5.1=6.9V. Battery = 11.1-5.1=6V
The point is I can get Zener Diodes in almost any voltage like 3.3V or 4.7V or 5.1V and that voltage will be subtracted away from the 12V battery before a 6V indicator reads the voltage.
We also can make a variable Zener diode with a way to adjust the voltage.

 

[SimonTHK]

Idea:
1) go inside the battery indicator and change a resistor. (probably can't)
2)Can you get a 6V indicator? Get a "Zener Diode" and put it in the (+) wire of the indicator. This Zener Diode will eat up some voltage.
Example: Zener Diode = 5.1V When the battery is at 12V the indicator will see 12-5.1=6.9V. Battery = 11.1-5.1=6V
The point is I can get Zener Diodes in almost any voltage like 3.3V or 4.7V or 5.1V and that voltage will be subtracted away from the 12V battery before a 6V indicator reads the voltage.
We also can make a variable Zener diode with a way to adjust the voltage.

Ty but I can only use this 12v indicator, which is part of a bigger display. I need to increase the voltage. Trying to read up on the pump charge thingy

 

[ronsimpson]

Some battery indicators are generic in nature. Inside there is a adjustment so the same electronics can do a 6V or a 12V job.

 

[JimB]

I think that the big question is "how much money can you spend?"

If the indicators cannot be re-calibrated in any way, my first thought is that you could use an isolated DC/DC converter, which can produce the extra volt or so which you need to add onto the signal to the indicator.
Isolated DC/DC converters are not exactly cheap (from memory), but would do the job OK.

JimB

 

[JimB]

Something like this is what I had in mind:
**broken link removed**
The 12v output of the converter can be cut down to 1v or so using a simple voltage divider, and then added in series with the battery voltage signal to the monitor device.

JimB

 

[ronsimpson]

I certainly can make a circuit that adds (some amount) of voltage on top of a 12V battery.
The circuit will only power the indicator! not the load! (need to know how much power it takes to light the indicator)
I think it could take any battery voltage from 5 to 25V and add (0.5 to 3V on top).
OR
It could add 10% to the battery voltage. (1% to 20%)
Maybe it does not matter if it is a fixed voltage or a percentage. (different error amp)

 

[alec_t]

How much current does the battery indicator require on its voltage-sense input?

 

[ronsimpson]

How much current does the battery indicator require on its voltage-sense input?

That is the question of the day.
The indicator might be a string of LEDs in series so the current is 5mA
OR
It could be an IC and the LEDs are in parallel. 50mA

 

[alec_t]

... or it could be a computer with a high-impedance input to an A/D converter. Who knows?

 

[Colin]

Take a photo of the voltmeter so we can help.
It's just a matter of putting 100k to 1M across the resistor inside the voltmeter.