Checking battery readings in caravan

Submitted: Tuesday, Nov 29, 2016 at 10:13
ThreadID: 133864 Views:4219 Replies:6 FollowUps:3
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Seeking your opinion on whether I may have a bit of ‘leakage’ on my new caravan house battery please.

The previous battery lasted around 3 – 4 years (bought as a demonstration model) and drained twice after recharging when the van had been returned from a repair job – complete re-sheet on the door side.

This unit drained (less than 12v) in less than two weeks after being installed, so I topped it back up again – 2 days on charge and have recorded the following readings:
13.57v at 9am just prior to disconnecting from a reliable onboard Ctek unit. 6pm read = 12.7v
Next 4 mornings readings: 12.8v 12.7v 12.58v 12.49v.

My question is – should I be concerned at the drop off over the last 3 days.

I have used a second meter to verify readings so I don’t believe the meter is failing.

The van 12v mains switch is off and beyond that I haven’t a clue for further testing. Any suggestions please? At this rate I feel the battery will need a recharge on a weekly basis rather than hold up for a couple of months like the previous unit.

The battery is a 110 a/h sealed unit – Ultimate Xtreme N70AGM VO according to the receipt.

Cheers - Phil
Phil 'n Jill (WA)

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Reply By: Allan B (Member, SunCoast) - Tuesday, Nov 29, 2016 at 10:34

Tuesday, Nov 29, 2016 at 10:34

You can check as follows:

Fully charge the battery as you did before.
Disconnect it from the charger and caravan.
Wait for an hour or so and note battery voltage.
Read battery voltage each day.
If it is dropping by more than say 0.1v per day then battery may be faulty with self-discharge.
If it is not dropping much then battery does not have an internal discharge.

Now reconnect to caravan and again read voltage each day. If it is dropping significantly then the caravan wiring is draining the battery and needs investigating.

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Reply By: Member - Phil 'n Jill (WA) - Tuesday, Nov 29, 2016 at 10:54

Tuesday, Nov 29, 2016 at 10:54
Thanks Alan - exactly what I needed - some direction in how to proceed from there - Logic isn't my strongest point.

Greatly appreciated - will keep you informed.

I was hoping to have some feedback this morning as the van repairer is dropping off a hubcap this morning and I can give him a 'heads up' on my concerns and how I am now going to monitor it.

Cheers, Phil
Phil 'n Jill (WA)

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Reply By: Sand Man (SA) - Tuesday, Nov 29, 2016 at 12:16

Tuesday, Nov 29, 2016 at 12:16

With a reduction of voltage of 0.1v per day or thereabouts, something is slowly draining your battery. 12.8v is fully charged.

The isolation switch should disconnect everything from the battery otherwise it is not an isolation switch. Perhaps a device (such as a brakeaway system) has been wired up to bypass this switch, or some other accessory is slowly draining current.

I'm diagonally parked in a parallel Universe!

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Reply By: The Bantam - Tuesday, Nov 29, 2016 at 12:27

Tuesday, Nov 29, 2016 at 12:27
Does not look so bad to me ....... most lead acid batteies will st around 12.5 volts once they have reached a resting state.

If you want the truth, test the battery out of the vehicle. and measured direct at the battery terminals

It's not what happens in the firts couple of days that matters it is how the battery voltage stands up over a couple of weeks.

Any decent healthy battery should hold a reasonably steady voltage for at least a fortnight if left alone

remember too, many batteries won't settle down till they have been cycled a few times.

Don't worry too much about the second number past the decimal point ....... one decimal point will be sufficient ...... temperature alone will cause variations in the order of the second decimal point.

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Reply By: Member - Phil 'n Jill (WA) - Tuesday, Nov 29, 2016 at 14:09

Tuesday, Nov 29, 2016 at 14:09
Thanks again Alan, Bill & Bantam for those hints which I have taken on board and will follow through.

It turns out (as usual) that the 12v mains switch just inside the door is not as expected - it really only controls the roof lights by the look of it. With that switch still off, the pump , TV, bedside lights and probably a host of other items still operate and in being shown this we noticed a 'booster' switch for the TV reception was 'ON' with a green LED light glowing (this was inside a locker and not investigated - just another of my shortcomings). I am told this shouldn't be much of a drain, but is just another factor to consider.

I have been shown how to truly isolate the battery with a push button that will drop the fuse out, so if I have further concerns after more testing, that might stop the nonsense until the 'draining' is sorted out.

Meanwhile I shall take up the suggestion of disconnecting the battery completely so there is no mistake about anything hanging off it after I have brought it back up to the fully charged state, then do the daily monitoring.

When all that is sorted I will carry on to the main objective I had by connecting the 80 W solar panel to the van battery via the regulator and also stick my very old Engel 45L frig into the Anderson plug and see how the overall impact is on the battery over a few days. I have rarely pulled in anywhere for more than a 2 night stopover and usually hook the Engel to the vehicle 2nd battery. At home I should have the luxury of a proper test of the solar capacity without jeopardising our travel situation.

I guess I am endeavouring to assess whether I need to update to modern technology (i.e. later model frig) or save the shekels for other upgrades.

As usual I am impressed and grateful for the informed responses - thanks.

Cheers Phil
Phil 'n Jill (WA)

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Follow Up By: swampy - Tuesday, Nov 29, 2016 at 14:27

Tuesday, Nov 29, 2016 at 14:27
Install a shut down isolator . Completely disconnects electrical system
The only item u may leave still connected is a solar panel charging .

From what you have described u have at least 1 load leaching power.

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Reply By: Member - Phil 'n Jill (WA) - Thursday, Dec 01, 2016 at 12:13

Thursday, Dec 01, 2016 at 12:13
Well team - the isolation of the battery from the van electrics did the trick - solid 12.8 - 12.9 after a recharge since 2 nights ago.

So assumption is that I need to either find the leakage in the van or keep it isolated.

My next move is to hook the solar up to the system and run the big old MRF540B-M engel 39 litre job from an Anderson plug to get some idea how that will cope over a few days. - cold enough for the essentials - BEER.

Without a temp gauge like the younger brigade are spoiled with, I make room for one plastic bottle of water and use that as a monitor - when it shows any sign of icing up I know to back if off a touch...

The 80w solar panel (which produces 19 volt and drops to around 14 through a regulator) is on a 10 metre lead so I can get it away from any shade and face it to the strongest sun at varying times. The Engel is also on a lead long enough to ensure that is under shade cover next to the van (standard lead cut over to the Anderson connector).

The details on the compliance plate are fairly scratched & I wondered if anyone can tell me what the amps drawing are on the 240 v & 12 v sides are please. My plate suggests the 240V is 48 watt and 0.2 A but that does't sound right - but then I really would not know. I can't read any of the 12v details.

Hope I have provided all the necessary data.

Thanks again - cheers, Phil
Phil 'n Jill (WA)

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Follow Up By: Frank P (NSW) - Thursday, Dec 01, 2016 at 18:02

Thursday, Dec 01, 2016 at 18:02
Devices that are permanently connected, like dc-dc charger, mains charger, solar regulator all draw a parasitic current from the battery.

If you have any or all of those built in and permanently connected they will slowly drain your battery.

Is there a car radio/CD/DVD built in? The one in my van presents a parasitic load when it's switched off because it only goes to standby mode, so for me that's a fourth parasite.

An always-connected battery management/monitor system may be another.

A true isolator switch connected directly to the battery, with everything else hanging off the cold side would be a relatively easy solution, I would think.


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Follow Up By: Member - Phil 'n Jill (WA) - Thursday, Dec 01, 2016 at 19:09

Thursday, Dec 01, 2016 at 19:09
Thanks Frank - I am learning quickly that there is more than meets the eye - which I why I have always considered 12v 'black magic' - wonderful product but a real mystery.

Chap at Camec was good enough to add another string to my bow with the digital meter today - I have only ever used it to measure voltage, but he described how to check the leakage thru 'amp' measuring - one small step at a time for mankind...

Running a test now with the Engel off the 80w solar and battery maintaining over 13v whilst the sun is still up on this side of the country. Will have a look for that leakage on the next project - at present I have the van electrics isolated through the circuit breaker. I will kick that back in after I have had a couple of days with just the frig going to see how the battery copes.

Cheers - Phil
Phil 'n Jill (WA)

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