Auxiliary battery dead? (1 Viewer)

[MarionK]

The question isn't so much, "Is it dead?" as, "Why is it dead?"
I thought I had it on charge for the last 24hours, but it seems I had the charger switched off >.< so there's a faint glimmer of hope still but only faint.

I could really do with an idiot's guide to camper electrics . . .
Don't they charge up while the engine is running? Does the charger need to be on or off while driving?

 

[Richard n Ann]

It should charge up via the van's alternator. The charger doesn't need to be switched on

 

[pappajohn]

Yes, Via the engines alternator but it's painfully slow.
From flat maybe 10 or 15hrs constant driving.

If it's totally dead...not even enough for a light or two...it MAY be terminally damaged and while it will charge it won't hold the charge and be flat again in no time

 

[MarionK]

Thanks, both of you.

In that case it's definitely dead, and I am even more puzzled as to why. :S

A bit more info on why it seems to be dead:
When the panel by the camper door has the switch set to MAIN, AFAICT, everything works, and the BATT light shows green, with or without the charger being on, and with or without connection to external 240v supply.
With the charger off, and the switch set to AUX, (or half way) all the lights go out, (unless connected to the mains and the charger is on, in which case everything "seems" fine.)

I'm wondering if the battery isn't properly connected; the diagram of how it should be connected is as clear as mud.

 

[Spriddler]

A bit more info on why it seems to be dead:
When the panel by the camper door has the switch set to MAIN, AFAICT, everything works, and the BATT light shows green, with or without the charger being on, and with or without connection to external 240v supply.

When set to MAIN it's connecting the starter battery only which presumably is sufficiently charged.

With the charger off, and the switch set to AUX, (or half way) all the lights go out, (unless connected to the mains and the charger is on, in which case everything "seems" fine.)

When set to AUX it's connecting the hab battery only which is probably insufficiently charged (or knackered).

When set to 'half way' neither battery is connected to the habitation circuits so no 12v item will operate.

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[MarionK]

Thanks Spriddler, that's what I thought, but it's good to have it confirmed in plain english.
Any idea how a 2 yo battery got knackered? ( I don't want to get another if it's going to go the same way in another two years. )

 

[XxAnthxX]

Any idea how a 2 yo battery got knackered? ( I don't want to get another if it's going to go the same way in another two years. )

Batteries are consumable items and they don’t last for ever…..especially if they’ve had a hard life, been mistreated or allowed to be excessively discharged.

All of which will dramatically affect the life span of your battery.

Welcome to the wonderful world of continual motorhome expense and maintenance……

WHEN you replace it at least try to buy a decent brand/quality deep cycle ‘leisure‘ battery, it will be worth it in the long run.

Oh you’ll also need to invest in a subscription here if you want to continue to post…..again worth it in the long run.

 

[Spriddler]

Thanks Spriddler, that's what I thought, but it's good to have it confirmed in plain english.
Any idea how a 2 yo battery got knackered? ( I don't want to get another if it's going to go the same way in another two years. )

Almost impossible to suggest a single reason because I think in another post you mentioned that you've only just acquired the m/h so no past history available. Most likely it has died naturally or been left discharged or partly discharged for a few weeks.
If it was me I'd check that there was a charge going to the hab battery by putting a multimeter across the hab battery terminals and check the voltage with the engine stopped and then again with the engine running when the voltage should be higher than when the engine was stopped. Then check the voltage again after the engine has been stopped for say 30 minutes but with the 240v supply connected when the voltage should be higher than it was without the 240v connected.
If you buy a new battery and the charging system isn't working you'll be back at square one with a flat battery.
If you don't fancy the testing or don't have a meter someone on here may offer to do it for you if you gave a clue as to where you are.

 

[pappajohn]

Thanks Spriddler, that's what I thought, but it's good to have it confirmed in plain english.
Any idea how a 2 yo battery got knackered? ( I don't want to get another if it's going to go the same way in another two years. )

Maybe discharged too deeply too often, recommended discharge is 50%, or not left on mains charge when not in use.
Loads of possibilities, it's finding the right one!

 

[autorouter]

Don't they charge up while the engine is running?

Most motorhomes have a relay (electrically operated switch) that connects the leisure battery to the starter battery when the engine is running and the alternator is producing power. The alternator charges both batteries. When the engine stops, the relay disconnects the leisure battery from the starter battery. It takes several hours of driving to fully charge a flat leisure battery.

Does the charger need to be on or off while driving?

The mains charger and the alternator have diodes (electrical one-way valves) that prevent any unwanted back-feeding of charge. The mains charger can be left connected and switched on, that's what most people do, myself included. But no harm in switching it off.

It's a good idea to get a multimeter, a cheap one from a DIY store will be OK. Set it to 20V DC and take some measurements as Spriddler described. From these measurements you can tell if the leisure battery is being charged by the alternator or the mains charger.

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[autorouter]

Does the panel have a label (make/model)? Chances are that someone will be familiar with it, especially if you can post a picture of it.

Sometimes there is a box with 12V fuses on the front, and lots of wires going to it. If there is one, what make/model is it? Motorhome manufacturers buy these boxes in from a limited number of electrics specialists, so again it's likely someone will be familiar with it.

 

[Eddystone]

I always turn off the habitation switch, so that nothing works, if the Moho is just standing unused. I discovered years ago that each of the electronic circuits takes a small current to keep them active. This will drain the battery in just a few days especially if it wasn't fully charged when you left it.
The fridge, water heater, and space heater circuit boards each take a small amount to keep them active.

 

[autorouter]

Any idea how a 2 yo battery got knackered?

One way to ruin a lead-acid battery is to leave it in a discharged state for more than a few days. If it's been left discharged for weeks then it will be sulphated. It will appear to charge up to normal levels, but will have little capacity and will quickly discharge with a typical load that would normally last for hours.

What happens is, as the battery discharges, lead sulfate forms on the plates. It's soft and gooey, and when recharging it turns back into the other chemicals of the battery system. That's how it should work.

If the battery is left discharged for more than a few days, the lead sulfate gradually turns into hard crystals that are impossible to turn back into the other chemicals on recharging. So the battery loses capacity. A lead-acid battery needs to be fully recharged every few days, and kept at or near 100% when it's in storage not being used.

 

[MarionK]

Thanks, all, for your input.
I have managed to get a multi-meter today, and will (hopefully) give it a whirl tomorrow, and take a pic of the charger if I can too.
I'm on a bit of a steep learning curve re: chargers atm, and am wondering if, bearing in mind the age of the van/equipment . . .
Is it possible that the onboard charger might damage the hab battery by overcharging it, if it's left permanently connected to EHU?

 

[MarionK]

Well, I managed to take a couple of blurry photos of the charger, but couldn't get to the terminals at all.
Is the hab battery normally under the driver's seat, or has someone re-positioned it? I knew it was going to be a pita to get out to change it, but now I've discovered you can't even get to the terminals, I am totally boggled that anyone would think this is a good place to put a battery. :S

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[autorouter]

Welcome to the wonderful world of motorhoming . Usually the leisure battery terminals are easily accessible, but under the seat is the choice in quite a few motorhomes, so you need a Plan B. There should be a large fuse near the leisure battery, on the main power wire that goes to the 12V fusebox. Hopefully they haven't made that fuse inaccessible too. Measuring the voltage there, on the battery side of the fuse, is the next best thing. In theory there could be a bad connection along the wire somewhere, but realistically the voltage reading should be accurate.

The 'resting voltage' of a 12V battery (no charging, no loads) is normally between 12.0 and 12.8V, depending on whether it is full or very low.

When charging, the voltage goes up to at least 13.5V, probably more like 14.5V, so you can tell with the meter whether the battery is being charged or not. It takes several hours to fully charge a low battery, it's a chemical process inside the battery. When you think it's full, disconnect the charger and let it rest for a few hours, then take a voltage reading.

 

[Eddystone]

It has been a long time since November.
Have you been charging the battery at all during time since then?

 

[MarionK]

Thanks #autorouter that's just the kind of info I was needing. Will hopefully give it a try later this evening.
#Eddystone The mh has been on ehu, almost the entire time, but whether or not the charger is working is still unknown.

 

[MarionK]

Ok, with a bit more light, but still working mostly blind, I've managed to get to the battery terminals.
Whether on ehu, with charger turned on or off, or off the ehu altogether, the battery reads a healthy 12.66v, so I presume it's not the battery that is faulty, and probably not the charger either?

 

[Jimbohorlicks]

If the charger is on and your on ehu at least one of the batteries should be showing a much higher charge rate if around 13.6v depending on your charger.you need to switch your control panel and recheck which battery is charging on which setting. Then check the other battery with your multimeter both off and on charge.

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[autorouter]

As Jimbohorlicks says, it looks like your EHU charger is not charging. I'd expect a voltage of about 13.5 to 14.5V. 12.66V is a moderately charged battery that's not being charged. Not knowing your system, it could be many things - a switch not switched on, a blown fuse, a duff charger, etc. What make/model is your display panel and fusebox? If you post a picture of your control panel and fusebox, maybe someone will recognise it and know what to do.

 

[MarionK]

Jimbohorlicks I presume by 'other battery', you mean the starter battery.
So, back on ehu, and with charger on or off, (oops I forgot to turn it back on when I set the main panel to AUX first time) the meter now reads only 12.5v on the hab battery.
With the main panel set to MAIN, the starter battery reads 12.9v whereas, it had been reading 12.66v while off ehu.

Despite the battery reading ok though, the main panel is still dead when off ehu, and nothing works, afaict.

 

[Jimbohorlicks]

When you are on ehu the charger should put in a charge voltage of around 13.6 v no matter if it's switched to the starter or leisure (auxillary) battery. But both battery voltages that you show when off ehu seem to be ok.
Do you have any solar panels?
If the control panel is dead then you need to check the fuses or reboot the control panel.you need to advise what control panel you have,van details etc.

 

[MarionK]

autorouter I'm wondering about fuse too. :S

Hopefully I have posted the pics!

 

[MarionK]

No solar (yet)

Van is a P reg Fiat Ducato, Autotrail Cheyenne 585?
I don't think the units are clever enough to need rebooting! >.<
Yet another edit to say that no lights are on when set to AUX or midway, when off the ehu.

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[Jimbohorlicks]

The control panel seems to be functioning ok.does the battery light show as being ok on aux and main positions?
Someone with an autotrail is probably better answering as in my van the starter battery doesn't get charged up when on hook up so had to add a battery master to do that .

 

[MarionK]

Jimbohorlicks Thanks for your input.
I don't think my starter battery charges from the onboard charger either, but that's only from reading forums, not from a proper manual.
When the van is on ehu the lights are on, as in the photo,. It makes no difference what the switch is set to.
When off the ehu, the lights are still as shown while set to MAIN, but dim very rapidly to nothing when set to middle, and are all well and truly off when set to AUX.

 

[Spriddler]

When the van is on ehu the lights are on, as in the photo,. It makes no difference what the switch is set to.

That's correct. It doesn't matter which battery (i.e. Main or Aux) is selected on the switch because when on EHU with the charger switched on there are 12 volts being sent straight to the panel from the charger as well as to the leisure battery.
When not on EHU (or when on EHU with the charger switched Off) a failing battery can still show a good voltage but drop very quickly when a load (e.g. lights) are switched on (i.e. drawing current).

When off the ehu, the lights are still as shown while set to MAIN,

That's because they are being supplied by the Main battery (the vehicle starter battery).

but dim very rapidly to nothing when set to middle, and are all well and truly off when set to AUX.

When the battery selector switch is in the middle position neither the Main nor the Aux battery is connected.
Take a reading of the Aux battery voltage at the Aux battery terminal posts with your meter after the lights have dimmed but are still switched on. (EHU turned Off. Selector switch in Aux position).
These steps should help to determine whether or not you have a dead or dying Aux battery.

 

[autorouter]

Worth checking that AUX fuse. I think you turn it 90 degrees and it pops out, but some like that need unscrewing until the fuse pops out. It will be a glass fuse, you can probably see if the wire is intact or not. Or you could check it with the meter.

To check a fuse with the meter, switch to the resistance range, the lowest range, probably 20 ohms. The 'ohms' symbol is a Greek letter omega, looks like a headphone symbol. display will probably read 'Overload', OVL, OL, or something similar. When you touch the probes together, the resistance will read a small value, maybe 0.3 or 0.5 ohms. That's the resistance of the test leads.

If you touch the probes on either end of the fuse, it should go from 'Overload' to a low value, too low to register on the meter. If it stays at Overload then the fuse has blown.

I always switch the meter back to a 'volts' range after doing a resistance measurement. It's easy to forget and next time you use it to measure voltage without checking the setting, it might damage the meter.

 

[MarionK]

autorouter Fuse is ok
Spriddler The lights I'm referring to as 'dimming' are just the panel lights. I will see what happens to readings with the habitat lights "on" when I next have time. 99% sure that they don't even glow though.

Could it be the battery fuse that someone mentioned earlier is blown?

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