How much battery voltage drop overnight? (1 Viewer)

MisterB

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Last night i left the tv on standby and got up to a flat leisure battery after driving for about 4 hours ( so should have been fully charged) Ive checked today and am getting battery useage at 0.45 Amps with nothing running other than the fridge on gas. Is that usual or do i need a new battery as its losing power due to age/defect in some way? Would tv on standby after 6 hours of watching it drain it sufficiently so that it would be "flat' the next day?
 

pappajohn

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Ive checked today and am getting battery useage at 0.45 Amps with nothing running other than the fridge on gas
Fridge control circuit board will take a bit even on gas, your main control panel will take some if its a modern electronic one.

Using 0.45 amp per hour overnight is only 4.5amps for a 10 hour night.

A four hour drive won't charge a flat battery using a regular split charge.... It will barely scratch the surface.... Unless you have a B2B charge system.
As your engine battery nears full charge, very shortly after starting, the alternator reduces output to a few amps so unless your split charge cables are the thickness of pencils the battery is going to get very little charge.

I would suggest your battery isn't getting the charge you think it is and is never fully charged unless on hookup or its goosed.
 
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MisterB

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Thanks for both responses. I am slowly working through the info.

Papajohn,

how long would it take to charge a leisure battery on hookup

Would using the fridge on 12v as we drive along deplete the power?

When i started the engine this morning and left it running for 10 mins all the 12v eqpt starting working ok. I assume it must be charging the leisure battery as a priority rather than a little bit?
 
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pappajohn

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Would using the fridge on 12v as we drive along deplete the power?
When i started the engine this morning and left it running for 10 mins all the 12v eqpt starting working ok. I assume it must be charging the leisure battery as a priority rather than a little bit?
Flat battery on hookup.... 12 to 24 hours.
Depends on your chargers output current

Fridge.... Depending how old and what model its only designed to run on 12v with the engine running, via a relay, and even then, it runs off the engine battery not the leisure

Once the engine is running the 12v stuff will run on the few amps that the split charge is providing.
It will still only charge the battery very slowly.

Best thing for engine based charging is a B2B charger.
It fools the alternator into providing a very high output and providing the wires from engine battery to the hab battery are suitably large will rapidly charge the hab battery.
They come in a couple of amp ratings... 30amp and I believe 60amp and that's the current they will bang in the battery when it's flat.

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Fletton

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For info....

When calculating power useage before fitting solar....

I discovered my Avtex tv would use the same amount of power on stand by (say 20hrs ) as four hour on time viewing...

Turn it off ;)
 
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Well that`s our 13th year & still loving it.
Why travel with the fridge on 12v, we always travel with the fridge on Gas.
That way you won't get caught out if you forget to switch over when arriving at destination.
 
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Fletton

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Why travel with the fridge on 12v, we always travel with the fridge on Gas.
That way you won't get caught out if you forget to switch over when arriving at destination.

I travel on 12v... as it runs from engine alternator... as opposed to leisure battery ... :)
 
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pappajohn

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Why travel with the fridge on 12v, we always travel with the fridge on Gas.
That way you won't get caught out if you forget to switch over when arriving at destination.
As I said, depends on age and model.
Older ones won't run on 12v except with engine running if they're wired properly.
 
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MisterB

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Thanks everyone. Im beginning to think that the battery is ok, but it just isnt charged fully. I have put a B2B top of the list. If i can get one in the morning before we leave peterborough then i will and fit when i get home. Even if i do need a new battery, a B2B will be helpful. Our fridge is a Thetford fridge and seperate freezer i assume 11 years old ( 2008), same as rhe van. Thanks for the help so far. Weve turned everything off, so lets see how we go on in the morning. Will obv needsome lights later, but no tv, not even on standby. A few glasses of wine and an early night wont hurt us!

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Ever since lighting was by Calor gas.
If a battery becomes completely discharged the output from a normal charger may not be sufficient to 'shock' it back into accepting a charge.
 
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pappajohn

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If a battery becomes completely discharged the output from a normal charger may not be sufficient to 'shock' it back into accepting a charge.
Very true, but if its connected in parallel to a well charged one and put on charge it should then begin accepting a charge..... As long as it hasn't been stood flat for ages.
Let it build up some charge then it should begin charging on its own again
 
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Agreed @pappajohn

Would tv on standby after 6 hours of watching it drain it sufficiently so that it would be "flat' the next day?
I read the OP's comment above to mean that they had been watching the T.V. for 6 hours and then left it on standby all night (and maybe other low current items ?) in which case it could have been thoroughly dead for some time and it still wasn't showing any charge after a subsequent 4 hour drive.
(Just an idle thought as I've had it happen to me when my boat's leisure battery had been dead for some hours).
 
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If you want to know about how long a battery will last or will take to charge, you need to know how big the battery capacity is, how fast the hookup charger charges, how fast the engine alternator charges, and how much power is going out of the battery.

The battery capacity is shown on a label on the battery, in units of amp-hours (Ah). Ignore the Cold Cranking Amps (CCA) figure, it is irrelevant for a leisure battery.

The hookup charger amps is shown in the manual. If you know the make and model of the charger someone can probably tell you its amps output.Sometimes the hookup charger is incorporated in the mains input/12V fuses box. A photo will help.

I see that you can tell that .45 amps is going out of the battery. Is this a figure displayed on a control panel? If so, does it show the battery voltages? Does it show the amps going into the battery, for example on hookup?

I don't have the figures for your MH. A typical MH battery is 100Ah capacity. A typical hookup charger will push out its maximum current, maybe 18 amps, until the battery is 80% charged.

Let's say this battery is very flat, say down to 20%. To charge it up to 80% it needs to add 60% to 20% to make it 80%. so it needs to add 60% of 100Ah, which is 60 Ah.

A charger with 18 amps output charging for 3 hr 20min (ie 3.33 hours) will supply 18 x 3.33 = 60 amp-hours. In theory. In reality it will probably take a bit longer, maybe 4 hours to do this.

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I'm not doubting what you say, can you please provide a link to said act.
I thought it was allowed if you have both a crash sensitive regulator and a high pressure hose with rupture protection. The rupture device protects from leaks on the high pressure side and crash regulator shuts down the low pressure side.
 
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Why travel with the fridge on 12v, we always travel with the fridge on Gas.
That way you won't get caught out if you forget to switch over when arriving at destination.
A naked flame anywhere near a fuel forecourt is not a good idea. That is why the AES fridges do not change from 12v to gas until some time after the ignition has been switched off.
 
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Lenny HB

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I thought it was allowed if you have both a crash sensitive regulator and a high pressure hose with rupture protection. The rupture device protects from leaks on the high pressure side and crash regulator shuts down the low pressure side.
Providing the appliance is approved for use such as Trumer heater. The act bans the use of appliances with naked flames which is what a fridge has.
 
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The act bans the use of appliances with naked flames which is what a fridge has.
I'm not convinced that's correct, Lenny. The relevant regulation is here: https://www.legislation.gov.uk/uksi/1986/1078/regulation/96/made

Reg 96(3) prohibits the use of gas-fired appliances in a moving vehicle, subject to exceptions. One exception in 96(3)(c) is "a refrigerating appliance".

Interesting that it does not seem to be a specific offence, but is still dangerous when driving on to a fuel station forecourt, as others have said.
 
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pappajohn has given you the answers.

I too recommend a B2B charger as we have one fitted and it does bang a huge charge into the leisure batteries when engine is running, and tops-up a day's battery usage in a 20-30 min. run.

To read more go to Sterling's website, where there is a good description. They make a selection of models as do Viktron.

Geoff
 
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Lenny HB

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I'm not convinced that's correct, Lenny. The relevant regulation is here: https://www.legislation.gov.uk/uksi/1986/1078/regulation/96/made

Reg 96(3) prohibits the use of gas-fired appliances in a moving vehicle, subject to exceptions. One exception in 96(3)(c) is "a refrigerating appliance".

Interesting that it does not seem to be a specific offence, but is still dangerous when driving on to a fuel station forecourt, as others have said.
upload_2019-4-28_10-13-22.png

3c states :- which does not expose a naked flame to the outside of the appliance.

The flame on a dometic fridge is exposed at the back of the fridge, just look through your grill when it's running at night you can see the flame from 50 yds away.
 
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MisterB

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Bavkto the original discussion. I turned the engine on yesterday and let it idle for about 15 mins. I did it 4 times. Last night no tv, but lights erc as normal. No tv plugged in over night, fridge left on gas, main control panel turned off. This morning 12.7v on the leisure battery, everything working just fine.

So new queiries/thoughts
1 if the battery was goosed, just by idling the engine for about an hour surely it wouldnt put enough power into the battery unless there is a B2B already installed? How would i know?
2 it looks as though the tv being left plugged in on standby might have been the issue, irrespective of why it happened, at least i wont do that again!

Thanks for the 'on topic' responses !!

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View attachment 299692
3c states :- which does not expose a naked flame to the outside of the appliance.

The flame on a dometic fridge is exposed at the back of the fridge, just look through your grill when it's running at night you can see the flame from 50 yds away.
I agree with you about the naked flame, but not about the offence. IMHO, the refrigerating appliance is to be read separately from everything after the "or", which relates to a heating appliance.

However, taking the hint from @MisterB, we are off-topic so we'd better stop! (y)
 
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1 if the battery was goosed, just by idling the engine for about an hour surely it wouldnt put enough power into the battery unless there is a B2B already installed? How would i know?
Ideally you need to see the amps going into and out of the battery. It's possible that you can already do this because you said the amps out of the battery was .45 amps. Does this meter show the amps into the battery, from the hookup charger or the engine alternator for example?

You can calculate the amp-hours going into the battery by reading the amps and noting how long it's charging for. Amp-hours = amps x hours. So 18 amps for half an hour is 18 x 1/2 = 9 amp-hours, for example.
 
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Well that`s our 13th year & still loving it.
A naked flame anywhere near a fuel forecourt is not a good idea. That is why the AES fridges do not change from 12v to gas until some time after the ignition has been switched off.


You are quite correct but who suggested pulling into a fuel station?
 
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