BATTERY CUT OFF VOLTAGE GADGET

[sonic113]

Ok fellas been very busy and haven't been on forum in a while but this issue has happened to me twice now and I need to do something lol!

 

Basically the kids have a twin screen dvd player in back of car that runs on the 12v socket inside the centre console. All is great as this keeps the them quiet and I can listen to the radio in peace lol! BUT when parked up for more than an hour and a half or so the battery has died twice now when I go to start. Now I will admit the car has been switched of so this is obviously why its running the battery down as the 12v socket is a constant drain when car is off , The radio I don't think is causing the issue as it turns off after about 1 hour anyway but I don't think it would be much of a drain I think the culprit is the DVD players via the 12v socket and it only happens if we are parked up waiting for more than 1 hour or so not on short waits so I would be 100% its the players.

Now what I want to know is is there any gadgets for the 12v sockets that can keep an eye on battery level and cut of anything that's plugged in when the battery voltage drops to a set amount to still leave enough for the car to start? I have saw devices online and on the forum but they are more for hardwired dash cams for recording when parked ect.

 

The only other option I can think is to get one of them wee battery voltage meter jobbies that use another power sockets and keep an eye on the voltage when parked . At least this way I can cut off the players or just start up and take a spin to recharge lol!

 

http://www.ebay.co.uk/itm/LED-CAR-VAN-12v-24v-BATTERY-VOLT-VOLTAGE-METER-MONITOR-FOR-CARAVANS-Motorhome-/201459532152?hash=item2ee7ec8178:g:4lAAAOxy7nNTQWAS

 

 

Any advice on gadgets is welcomed.

 

Many thanks in advanced.

 

[Stoney871]

Any use to you?-

http://www.ebay.co.uk/itm/282065809159

Sent from my SM-G930F

[blue crush]

I got myself a volt meter to keep eye on my battery for the very same reason. When it falls under red markers i know battery is being drained

[sonic113]

 

On 17/06/2016 at 5:47 PM, Stoney871 said:

Any use to you?-

http://www.ebay.co.uk/itm/282065809159

Sent from my SM-G930F

Same kind of idea I think But that looks a bit to complicated to install lol! But thanks anyway stoney. I think a basic 12v socket volt meter will do the job.

 

 

22 hours ago, blue crush said:

I got myself a volt meter to keep eye on my battery for the very same reason. When it falls under red markers i know battery is being drained

Thanks David at least I'm not the only one lol! Is the meter you use just like the one I posted a link to or is it different?

 

 

 

 

also does any one know what the minimum voltage is that the car could drain to before it wont start? I think i read one time that it was 11.3v anything below this and she wont start.

[Stoney871]

Easy plug'n'play-

http://www.ebay.co.uk/itm/231962625577

Sent from my SM-G930F

[blue crush]

That one stoney has linked to is simple to use.

I have a 52mm gauge in a pod on my windscreen pillar. It seems to read abt 11v after engine is off but when engine is on.. It goes to abt 13/14v.

I think it must be under 11v to be drained but i am not so sure to be honest as havent taken the risk to let it drop so far lol.

[blue crush]

You can also buy voltage readers that plug into cigarette lighter/12v socket.

[sonic113]

Thanks guys.

 

Stoney great find fella I have will order that one and install. Very handy with the alarm feature. Exactly what im looking for so I will set to go off around 11.3 volts then take the car fr a spin to recharge lol!

 

Thanks

[ScaniaPBman]

Now, if I had a proper iPhone this would be the one for me...

https://www.amazon.co.uk/Battery-Guard-Bluetooth-Voltage-Display-Batteries/dp/B00ZETXNAQ/ref=sr_1_1?ie=UTF8&qid=1466367262&sr=8-1&keywords=battery+guard

ScaniaPBman.

[biff55]

i would give myself a bigger margin of error than 11.3v as draining the battery repeatedly to below 12 is not going to help its long term ability to hold a charge.

shame they dont make lithium ion batts for  (non-electric ) cars yet cos thats what you need really

or possibly switch to an auxilary power source for when youre stationary using a dedicated outlet socket

[trailertrash]

Why not go for a dedicated leisure battery and socket and a split charge relay?

Oops! Just noticed that biff55 has said almost the same thing above:

Quote

or possibly switch to an auxilary power source for when youre stationary using a dedicated outlet socket

 Like this

 

Edited June 19, 2016 by trailertrash
Duplicated advice

[Tdci-Peter]

On 17/06/2016 at 5:30 PM, sonic113 said:

when parked up for more than an hour and a half or so the battery has died twice now

To drain a fully charged 50AH battery in an hour and a half is a current of 33 Amps! This is pretty high, and would blow the fuse in most "12v" outlets. This suggests your battery is a bit poorly, and is nowhere near its stated capacity (which should be on the label).

As Pete (Biff55) says, going below 12v (open circuit voltage) is not good for the battery, but at high current, voltage drops in the cabling & battery internal resistance will lower the voltage reading, and you will find the voltage will drop below 12v, and maybe below 11.3v, rather quickly. However it should recover to over 12v when the load is disconnected (which will annoy the kids no end, I know! )

A battery voltage indicator, or cut-off circuit with voltage indication, is a very good idea. However some experimentation will be needed to determine a best compromise cut-off level that will save the battery, and keep the kids happy.

The voltage indicator can also be used to check battery condition to some extent. A known load (headlights and ignition is typically 12 to 15 Amps), should not discharge the battery below about 11v (load connected) or 12v (load turned off & battery recovering), even if applied for several minutes. (With engine off. With engine running, expect 13v to 14.5v.)

The separate battery idea (Adrian) is a good one, but expensive. But how much is the quietness of the kids worth?

Sorry if this is a bit technical, but Amps & Volts are my bread & butter!

Peter.

 

 

[blue crush]

Would a compactitor that is used for car audio systems do anything to hold the charge longer?

[Jon84]

2 hours ago, blue crush said:

Would a compactitor that is used for car audio systems do anything to hold the charge longer?

No that i just like filling a bucket with power temporarily for large bass hits.

Personally, I'd go for the leisure battery option

[MONDEO TXS 2.2]

Bear in mind that no matter the ah rating of any battery only approximately half of it is useable, so, for example if the battery is rated at 100 ah only 50 ah is practically useable.

Therefore a 100 ah battery will not give 100 amps for one hour or 1 amp for 100 hours but merely 50% of that . . .  & as stated a leisure battery will offer more deep cycling ability.

 

A good engine starter battery at rest ( off charge ) should be around 12.7v +  . . . 12v & less is technically a flat / discharged battery.

[Tdci-Peter]

1 hour ago, MONDEO TXS 2.2 said:

if the battery is rated at 100 ah only 50 ah is practically useable

In practice, Mark is correct.

Technically, the Reserve Capacity of a battery, as on the label, is the time that the battery can deliver a specified  current (Normally 25A) for, in hours, multiplied by that current. The normal test termination voltage is 10.5v. And a reputable manufacturer like Bosch or Varta will have done documented tests to verify this. If the new battery, fully charged, cannot deliver this, then the manufacturer is probably breaking the law (Trade description act or EU regulations).

But, once the battery has been used like this, there is no guarantee that it will ever fully recover, and the next discharge cycle may be reduced. That is where "Deep Discharge" batteries score over normal car batteries intended primarily for starting duty. The primary specification of a car battery is its CCA (Cold Cranking Current, a rather nice, descriptive term I think!)

Also, as the battery ages, the Reserve Capacity will diminish. It is reasonable to guess that halfway through its life, the capacity may be about half its original.

Thus the 50% rule is a good one, and may well be under that for an older battery. Also regular discharges to 50% will, unfortunately, greatly shorten the life of a standard car battery, especially if it is left for any length of time in a state other than fully charged. (AGM or EFB batteries for cars with charge management & regen. should be a little more tolerant).

If a battery has been charged (during a journey), and then left idle, its voltage should drop slowly to about 12.4 to 12.7 volts, I certainly agree. But these batteries take a long time for the voltage to stabilise after charge or discharge, so after a period of discharge, you may have to wait quite a while (possibly hours) for the voltage to fully recover to its idle state. That is why I suggested "over 12v" as a recovery threshold.

However, I think I am going into technical details which, while important or interesting to some (like me), are not very relevant to someone who just wants a gizmo so his kids DVD does not result in not being able to start the car. Give it a go, it will probably work fine for you.

 

 

 

[trailertrash]

TDCi-Peter says above:

Quote

The separate battery idea (Adrian) is a good one, but expensive. But how much is the quietness of the kids worth?

Not that expensive actually. A quick search on eBay for, respectively, 'caravan leisure battery' and 'caravan split charge relay' shows a 110AH leisure battery with 3yr warrantee and 'magic eye' (?) for £25 post free (auction starting price but no bids yet, closes tomorrow - buy now £55) and a relay for £7.50 post free. Add an hour for a competent auto-electrician - say £40 - and the whole kit-and-caboodle comes in at  < £75. While you're at it add in a dual power USB socket and a couple of standard 'cigar lighter' 12v sockets. Job done!

[sonic113]

2 hours ago, Tdci-Peter said:

 

However, I think I am going into technical details which, while important or interesting to some (like me), are not very relevant to someone who just wants a gizmo so his kids DVD does not result in not being able to start the car. Give it a go, it will probably work fine for you.

 

 

 

Peter thank you very much my friend fro all the information. Maybe a bit too technical but none the less very informative. I think I will just be using a little voltmeter as for all the time I do be parked up its not very often its more than 1 hour so i will just use a little voltmeter or my multi meter to keep an eye on the battery level..

 

 

Thanks again to all who inputted here,