Why have I got a low voltage warning?

[Ork]

Hi all,

I’m new here; thanks for having me! I have a Renault TRAFIC campervan conversion. It’s our 3rd short trip in it and our leisure battery is giving us a low voltage warning. We’ve switched from off-grid to electric hookup and we’re charging up the leisure battery through the hookup now. However, even though the leisure battery is now 38% charged, the low voltage warning is still there. Any ideas, anyone? TIA.

 

[bigtwin]

What is it that is annunciating the low voltage?

Also, do you use an inverter?

Ian

 

[PlacidoD]

If you are on an ordinary lead acid leisure battery you in reality only have 50% of that battery capacity available. Once the voltage drops to a point where you are below 50% (from memory that will be 12.8 volts) any decent set up will warn you so as to avoid battery damage. Mine trips out at around that figure.

Your mains charger will likely have a slow rate of charge so it will take some time on an EHU to get back above 50%.

If it lead acid and genuinely at 38% then likely you have damaged the battery. If it is e.g a gel battery they can be taken down to circa 20%.

You would be well advised to check your battery once you have got over the immediate problem. I replaced mine (Hope yours is more accessible than mine is!!!) Batteries don't last for ever so your battery may well have been reaching the end of its life when your problems started.

The simple way to test is on your drive with EHU disconnected and leave a few lights of known output on and see how quickly you get warning lights showing. (Do not leave the fridge on 12V when doing this. That will guzzle electricity.)

P.S. I changed all my bulbs to leds at the same time as fitting a new battery. You may want to consider doing the same.
P.P.S. All of the above assumes you are not on an expensive LiFePO battery. I very much doubt that applies.

 

[Spriddler]

our leisure battery is giving us a low voltage warning.

What % charged did it show when the warning lamp illuminated?

We’ve switched from off-grid to electric hookup and we’re charging up the leisure battery through the hookup now. However, even though the leisure battery is now 38% charged, the low voltage warning is still there.

How long has it been on charge on EHU?

Fully charged voltage for a LA battery is circa 12.8v. Depending upon your set-up the low voltage light will probably be triggered by voltage rather than state of battery charge. 38% charged is only around 11.8v and I would expect the low voltage light to be on until you get to around 50% to 60% charged (circa 12.02v). Dependnt upon how long it's been on charge you may need to wait longer, although if the battery has been down to say, 11 volts this time or on other occasions it's probably done-for.

 

[PlacidoD]

"Fully charged voltage is circa 12.8v"
I stand corrected on the numbers but we are otherwise singing from the same hymn sheet!

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[autorouter]

Can you post a picture of the display that's showing the battery state of charge? Also what type of battery is it - Flooded lead-acid, Gel, AGM etc? Maybe post a picture of the label if it's visible.

 

[VXman]

 

[autorouter]

I was wondering how you found the charge level was 38%. Most campervans have a simple voltage meter to monitor the leisure battery, or even just three or four LEDs (full, half, low, flat). Either you have an actual battery monitor device like a Victron BMV shunt which has a percentage state of charge display, or perhaps you have a lithium battery and you're looking at the battery app on your phone. Some lithium battery apps have a low voltage alarm as well.

If it's a lithium battery, all this talk about not letting it go below 50% will not apply at all. Lithium batteries are fine to be discharged to 20% or even 10%. They don't suffer deterioration from being left in a discharged state for weeks, like lead-acid batteries do. They have a built-in Battery Management System (BMS) that usually stops anything bad happening to the battery, and many of them have a Bluetooth module built-in to communicate with a phone app, to show the battery state and history.

So, is it a lithium battery, does it have a brand and model number?

 

[bigtwin]

I was wondering how you found the charge level was 38%.

I admire your optimism.

I wondered that too in post #2 but have given up hope of getting any answer.

Ian

 

[PlacidoD]

Still no reply or words of thanks (other than a perfunctory "TIA" in the original post).

Maybe she is saving her other 5 free posts to deal with other problems. I for one will not be in a hurry to answer if she does!!

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[CAB96]

Still no reply or words of thanks (other than a perfunctory "TIA" in the original post).

Maybe she is saving her other 5 free posts to deal with other problems. I for one will not be in a hurry to answer if she does!!

Probably can't get back on as she's flattened her phone battery and can't recharge it

 

[pappajohn]

As you are on hookup the displayed voltage should be around 14.4v....the charge voltage.
What you're seeing is the actual battery voltage so indicates the charger IS NOT working which could explain the low voltage alert.

 

[pappajohn]

Still no reply or words of thanks (other than a perfunctory "TIA" in the original post).

Maybe she is saving her other 5 free posts to deal with other problems. I for one will not be in a hurry to answer if she does!!

As being new to the forum they maybe never expected such a rapid reply.
Some forums can take hours, or even days, to get a response.

Oops,just seen it has been days.

 

[Boldly]

View attachment 953321

This table has different values to the one in the other thread running on a similar theme at the moment.
Is there a definitive value for all batteries or is it not possible to be 100% accurate with lead acid?

 

[Boldly]

Your display is measuring the voltage from the batteries at the control unit then using an internal calculation like below to give you the %.
View attachment 954591
When you hookup the control unit shows 100% because that's measuring what the charger is putting into the batteries.
With your batteries being very low it will take many hours on charge to get them back to 100%

Tomorrow morning disconnect the hookup make sure everything is turned off then after half an hour switch the control panel on and look at the %.

If it's not 100% get your dealer to sort it out.

This one. Which one is accurate?

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[VXman]

This table has different values to the one in the other thread running on a similar theme at the moment.
Is there a definitive value for all batteries or is it not possible to be 100% accurate with lead acid?

There does seem to be some variation if you google battery voltages/state of charge but this one seems to be most common and generally viewed as in the correct ball park for standard lead acid. AGM can be slightly different.