Dangerously low batteries Sergent EC325 won’t switch on

[tonyidle]

In constant current mode, charger does not use the battery 'open circuit rest voltage' as an indication of the state of charge of the battery. The manufacturer has determined from extensive measurements that there is another method to find out when the battery is 80% charged.

When a fixed current is put into a flat battery, the terminal voltage will be less than 14.4 volts. The measured terminal voltage will depend on the state of charge of the battery. For example, if that battery is 80% charged, the terminal voltage at the fixed current will be 14.4 volts. It is safe to push out the fixed maximum current into a flat battery, until the voltage rises to 14.4 volts. At that point, the battery is 80% charged.

Another way of looking at this is, the charger is trying to apply 14.4 volts to a flat battery, but the charger does not have the current capability to make the voltage up to 14.4 volts, so it struggles along, applying as much current as it can, until the voltage finally reaches 14.4 volts.

That's interesting (and perfectly logical ). I hadn't considered that constant current charging offered a better method of determining charge state. Thanks .

 

[autorouter]

A van charger can often be designed to act as a PSU for the van if no leisure battery is fitted or if the main battery fuse fails so any voltage higher than 14.2 or so could be potentially damaging to the habitation electrics.

This is true in general, but does not apply to the ECS325 in the OP's van.

The ECS325 has a separate battery charger and habitation power supply, with relays to automatically switch the batteries between the hab electrics and charger when the EHU is connected. The charger can therefore apply whatever voltage is likes to the batteries without having to worry about the hab devices. Also it can see the exact current going into the batteries without the complication of current draw from the habitation circuits. Most motorhome controllers don't do this, including the Schaudt Elektroblocs.

 

[tonyidle]

This part : A van charger can often be designed to act as a PSU for the van if no leisure battery is fitted or if the main battery fuse fails so any voltage higher than 14.2 or so could be potentially damaging to the habitation electrics. Some more recent motorhomes appear not to allow this by turning off all electrics if no battery is installed. Without a facility within the van charger for a higher charging voltage (and therefore current) a 200Ah battery will take considerably more than 24h to fully charge.

No specific source - just experience of van charging systems. At on time all habitation PSUs output was set at 13.8v. Advantages of this approach were that 13.8v was battery float voltage so indefinite connection did no harm and 13.8v was a safe level for operation of hab electrics whether a battery was in use or not. A big disadvantage was that constant 13.8v would never fully charge a lead acid battery so to get the best from a leisure battery it was necessary to charge it from a smart(er) charger before each trip. Early smart chargers had two stages: charge using a 14.2v source until current dropped almost to zero followed by 13.8v indefinitely. The chargers output current wasn't especially important other than in determining how long it took to charge the battery. Modern built-in chargers are more sophisticated in that they can provide a high constant current whilst maintaining a limit on battery terminal voltage (see post by @autorouter). Even so it's not possible to operate without a battery on some if not all modern vans as it was in the past because the few vans I've experienced cut off 12v electrics if the leisure battery drops below a certain voltage. With no battery in circuit they'd never turn on.

 

[PhilandMena]

OK Tony, thanks for that. This is outside of my experience of motor-homes as our is 7 year old from new and the one before built in 2004 and so my experience is based upon these van and any info I have picked up along the way. To be honest I have little knowledge of how old PSU and non intelligent chargers operated. All the best.

 

[Charlie123]

Before throwing those batteries away get them hooked up to a desulphating battery charger. This can work miracles on seemingly knackered batteries. Ctek do a 7 amp one which is excellent. I have brought back a big battery just this week from 2-6 volts.

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[tonyidle]

OK Tony, thanks for that. This is outside of my experience of motor-homes as our is 7 year old from new and the one before built in 2004 and so my experience is based upon these van and any info I have picked up along the way. To be honest I have little knowledge of how old PSU and non intelligent chargers operated. All the best.

The only thing you need to know about them is "Not very well" .

 

[Lenny HB]

Before throwing those batteries away get them hooked up to a desulphating battery charger. This can work miracles on seemingly knackered batteries. Ctek do a 7 amp one which is excellent. I have brought back a big battery just this week from 2-6 volts.

IMO not a good idea even though they may partly recover a knackered battery I don't think it's worth the effort. Do you really want to be worrying every day the batteries may not last the night, not much works in a van these days without electrics.

 

[Titchdog]

We think the charger is working and the problem was the ‘entertainment unit’ in the autotrail. There are two black switches on a black panel. Difficult to see and both ‘on’. They had flattened the batteries which weren’t charging as there was a loose wire in the unit. We switched off the unit properly and with the unit charging properly we put on a fresh battery and it has kept its charge. We will wait till spring and get a couple of new batteries. Think the batteries that were on are cooked and won’t hold a charge. Thanks everyone.

 

[Jaws]

We think the charger is working and the problem was the ‘entertainment unit’ in the autotrail

I think that bit may be a red hearing..
I have never turned them off in our van.. Once you hit the off button on the control panel, all those circuits are dead

 

[HandyAndy]

Before throwing those batteries away get them hooked up to a desulphating battery charger. This can work miracles on seemingly knackered batteries. Ctek do a 7 amp one which is excellent. I have brought back a big battery just this week from 2-6 volts.

Not if they are AGM, that would be REAL bad advice

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[Hotcrossman]

Best advice so far from PhilandMena! (not over technical) You REALLY need to find out exactly what/which is at fault before splashing out for new batteries. I did and saved myself a lot of dosh.

 

[Hotcrossman]

A word of caution re Ctek . . . . I bought the so-called 'smart' and left connected in Spain over Winter - result totally cooked battery when came to use the mover to go home! I do have an old 'smart' which has been faultless for years (tempting fate?)

 

[HandyAndy]

A word of caution re Ctek . . . . I bought the so-called 'smart' and left connected in Spain over Winter - result totally cooked battery when came to use the mover to go home! I do have an old 'smart' which has been faultless for years (tempting fate?)

Having come in to work, to a serious sulphur smell and a smoking battery that had also been left overnight on a C-Tek, I'm with you on that one. Don't trust them at all, despite their seemed, good reputation.