Leisure battery charging current

[emclaughlan]

Over the last week I have been doing extensive research and my brain is now dripping out my ears. We have a 2010 Chausson Flash 11 on a 2.4 Ford base with a single leisure battery which sadly no longer meets our needs. I started thinking about adding another battery as there is space under the seat but I am scared by this advice, http://www.aandncaravanservices.co.uk/add-a-second-battery.php.

 

Lots of people seem to have two battery installations working fine and my understanding to date is that the high charging currents occur when the batteries are discharged and charging on alternator, but that's gonna happen, hence my worry. So here's the questions:

 

1. How can I tell how much current the batteries will draw at each stage of discharge? In my understanding two batteries should halve the internal resistance and double the charging current.

 

2. Am I correct that solar and battery charger current is limited by the device and this is only an issue for alternator charging?

 

3. Are all the people with battery banks 'getting away with it' due to shallow cycling, or is there some reasonable modification that stops the connecting equipment overheating?

 

3. My van appears to have one "Boite Relais Securite" (relay) fused at 50A but it appears to be for isolating the 12V from the control panel. Any ideas on how, or if, my split charging / fridge supply is done?

 

Apologies for all the questions.

 

Eddie

 

[aandncaravan]

emclaughlan - 2018-07-27 10:30 AM

 

Over the last week I have been doing extensive research and my brain is now dripping out my ears. We have a 2010 Chausson Flash 11 on a 2.4 Ford base with a single leisure battery which sadly no longer meets our needs. I started thinking about adding another battery as there is space under the seat but I am scared by this advice, http://www.aandncaravanservices.co.uk/add-a-second-battery.php.

 

Lots of people seem to have two battery installations working fine and my understanding to date is that the high charging currents occur when the batteries are discharged and charging on alternator, but that's gonna happen, hence my worry. So here's the questions:

 

1. How can I tell how much current the batteries will draw at each stage of discharge? In my understanding two batteries should halve the internal resistance and double the charging current.

 

2. Am I correct that solar and battery charger current is limited by the device and this is only an issue for alternator charging?

 

3. Are all the people with battery banks 'getting away with it' due to shallow cycling, or is there some reasonable modification that stops the connecting equipment overheating?

 

3. My van appears to have one "Boite Relais Securite" (relay) fused at 50A but it appears to be for isolating the 12V from the control panel. Any ideas on how, or if, my split charging / fridge supply is done?

 

Apologies for all the questions.

 

Eddie

 

 

Eddie, Not all Electronic Distribution/charger controllers are the same. Some are specifically designed for the load of a single battery and a max alternator charge current of less than about 18amps. Examples of the stronger units are made by Schaudt (not early pre 1999 units) higher spec Sargent boxes (although often let down by poor wiring by the Installer and excludes the new EC160), most later CBE power controllers and later Nordelettronica units.

The weaker units are those by Arsilicii, early Nordelettronica Fuse Boards, Calira, Reich e-Box (very poor at handling more than one battery) and early Schaudt.

 

Some Charger/Controillers will happily pass the extra Alternator current drawn by a second battery, the Schaudt Elektroblock EBL 220 is designed for 4 big batteries.

Some have a separate Split charge relay that also copes ok if the batteries are healthy.

 

There are lots of installations around where people think they are working ok with two batteries, when they are actually on a slow burnout.

 

1. Typically a healthy 100Ah quality, high tec wet acid battery can draw up to 15amps, maybe a shade more on 'initial start-up' but that drops off fairly quickly.

Note that Gel batteries charge more slowly and can draw lower current, up to 50% less, and why they take so much longer to charge.

 

But it is hard to predict the current drawn because batteries are not always healthy and the current draw will depend on the batteries health and the malady they suffer. For example some types of deterioration, like Antimony poisoning, cause higher current to be drawn, others might cause less.

Imagine a battery being allowed to deteriorate to the point that each Cell has a full or partial short? That would be a bit like putting an Iron bar across the Alternator terminals with massive current draw that would almost certainly burn it out.

 

 

2.Yes the primary issue is with the high Alternator currents that can be drawn by the batteries. But obviously you need stay within the capability of the mains 230v charger, the golden rule of which is regarded as 10 times the charger 'amps' output converted to Ah. E.g a CBE 516 safely supports 160Ah total battery bank size.

If the Starter battery is charged as well by the mains 230v charger then an allowance needs to be made for this

 

3. The CBE relay system you have fitted suggests it will cope well with 2 x 100Ah batteries that are healthy.

 

 

We have seen quite a few Sargent systems that 'have worked fine for years with multiple' batteries, but if you put a current meter on the battery leads while being Alternator charged they are quite often charging at a very poor rate. Less than 10 amps and around 13.9v, due to the extra load imposed on the wiring/solution.

These will rarely burn out, but neither will they charge at anything more than a snails pace. We estimate that around 70% of Sargent based solutions have a second battery solution that is far from optimum, yet the owners are completely unaware.

 

 

 

 

[Alanb]

Eddie,

 

My 2006 PVC has a nominal 160 Ah twin battery system from new. I have not had any problems with the 12V Distribution Board (12V DB).

 

I note that Allan of aandncaravanservices has already answered your questions 1 to 3, so I will confine myself in the main to your fourth question re split charge and fridge.

 

The CBE 12V DB (DS300?) is connected to the starter battery (B1) at its B1 terminal.

The board has integral split charge and fridge relays,

A second ignition switch controlled supply is also connected to the 12V DB. This second supply is electonically monitored and is connected to the spli tcharge and fridge relay coils, when charging voltage is detected.

 

A disadvantage is that both the fridge current of 13A plus, and the habitation battery (B2) charging current share the same cable. The consequent additional voltage drop reduces the B2 charging current.

 

Alan

[aandncaravan]

"A disadvantage is that both the fridge current of 13A plus, and the habitation battery (B2) charging current share the same cable. The consequent additional voltage drop reduces the B2 charging current".

 

 

Alanb, it is for a similar reason that we state the Sargent, and indeed most motorhomes fitted with a British made Power Controller, charge more slowly. I

n the Sargent case, not necessarily taking the Fridge supply from the same cable, but from the habitation battery rather than the Starter battery/Alternator.

However, additionally, in many Sargent installations the motorhome builder uses cabling that is undersized as well, resulting in what I describe above as 'Snails pace' charging.

As you point out, all that is required is decent cables with the Fridge supply taken directly from the Starter battery, or even better the alternator.

 

Alanb, you are lucky with your system it lets you see what is going on when the engine starts, so the display shows the voltage and the current, in most cases.

All a UK built van owner sees is the 'EMC' shutdown message, which is the reason why most don't know they have an issue that has become greater after adding a second battery. The rest that do know how bad things are, usually add a B2B

A simpler solution is just to use decent cabling supplied from the Starter battery/alternator.

 

 

[emclaughlan]

Thanks guys, that's top class advice. Looks like I have my work cut out to trace the circuits and work out the path of the charging current. I have the twin wheel transit with two ford batteries under the driver seat. Despite numerous enquiries I haven't been able to ascertain what chausson do with the auxiliary battery Ford supplies. I have run the vehicle without it and everything works. I speculated that, as it's intended to run the non engine equipment in the van, Chausson might have configured it as a second leisure battery but the consensus on forums was that it wouldn't be. As for Chausson, well the less said about them the better.

 

I got started on this project because my two year old 110Ah Enduroline hab battey was dying, so I put the van on a discharge test and the ford aux battery drops off like the enduroline, so I'm thinking they're in parallel and both dying (the ford is 8 years old, which might have contributed to the demise of the newer enduroline if they truly are in parallel.

 

So current thinking is; if they are in parallel, replace them both with 2 Yausa EFB, 100 or 75Ah, depending on what I learn. If the batteries are in parallel, I currently have 170Ah total with dying batteries. As Alan notes elsewhere, the CBE charger bulk charges to a voltage rather than a time, so I'm thinking the 10x rule is less of an issue than with other chargers. Assuming the circuitry suits I will put them both under the passenger seat for better balancing. Does this seem to make sense to you or am I missing something?

[aandncaravan]

Not sure your understanding of the CBE charger is correct? I thought they only charged at 'boost' voltage for 90 minutes, which isn't going to get a 160Ah battery bank charged very quickly at all if it is 50% DOD.

 

In 90 minutes a charge rate of 15amps is going to put in only 20Ah of the 80Ah needed.

That might mean it keeps cycling or the remaining 60Ah will be put in at 13.8v and just a couple of amps.

Potentially a 60+ hour charge time to get it 'full'.

 

If it is a 510/516, the manual states :

 

1) with maximum current until the end-charge voltage is reached:

The charging system is carried out in 4 stages:

2) when the threshold is reached the charger continues to operate for 90 minutes (lead

batteries) or 8 hours (gel batteries) with constant voltage.

3) voltage holding 13.8V (gel batteries) or 13.5V (lead batteries)

4) After 10 hours, the battery charger reaches the mode and begins to operate again only

when the battery voltage is lower than 13V .

 

 

Maybe you have a different charger, but the reason a 'timer' is used is for safety.

 

A non Motorhome charger generally works on the basis that it charges the battery flat out until the current being drawn by the battery drops below a set level like an amp, at which point it goes into 'Float' mode.

 

But it was discovered a long time ago this methodology isn't so good in motorhomes that have bigger battery banks that are charged unattended.

Imagine if you have a big battery bank that gets a bit tired, it may never stop drawing a lot of current. Never drops down to the Float stage.

 

Eventually the battery is destroyed, often in a big messy explosion.

 

If your charger truly is a none timer version, take extra care when charging unattended.

 

We have worked on many Transits, and the combination of battery connections seems endless. Even where the factory does one thing, the owner later changes it.

If it is 'Standard' I would expect the 'aux' battery to be linked in with the Starter battery at start up and then function as the 'primary' leisure, but so many variations.

 

Two Varta LFD75's work and fit perfectly. They also make a better Starter battery than the Ford original, both more powerful and greater capacity. The Varta Silver technology also handles the usual higher Transit Alternator voltages, if that wasn't disabled by the converter.

 

 

[emclaughlan]

Thanks Allan. I suspect you're right and I have misunderstood. I read those same words above but interpreted "until the threshold voltage is reached" as charging to a voltage, with the timer bit coming after that but it's obvious to me that you are much deeper into this stuff than me, so I'm inclined to take your view.

 

Looking at your final paragraph are you saying that, in my shoes, you'd look at replacing the 60Ah ford calcium with a 75AH Yausa EFB and put another Yausa under the passenger seat? What do you think of the idea of 75AH under the driver seat and 100Ah under the passenger? Is that too much of an imbalance?

 

Thanks for your help, you've saved me a lot of work.

 

Ed

 

[aandncaravan]

The Ford Starter battery is usually a Silver calcium battery and very, very expensive. 60Ah sounds a bit too small, I think the last I replaced was a 67Ah? Maybe you don't have an original OEM?

 

 

Yes if it was me and the Starter battery is more than 5 years old I would replace all 3 with Varta LFD75's because :

 

1 At 60Ah that is a very small Starter battery, even 75Ah is small, so works hard and is more prone to sudden failure.

 

2. It is such a pain to take off the Seat. Even more of a nuisance in the middle of a rainy night just outside Barcelona when all the battery shops are closed.

 

3. The right sized/quality Starter Battery can be hard to get in a hurry.

 

4. A perfect Starter battery isn't going to add to the charger load.

 

The LFD90 is zero fluid loss, no maintenance, perfect for putting under a seat and forgetting for 5 years.

 

 

Batteries must be matched size, age and technology, etc otherwise shortened life will result

 

[emclaughlan]

Yep, just checked; 2x 60Ah Silver Calcium ford original equipment which is now 8 years old. I hadn't really thought about the starter battery as it's never had a hiccup. I'm curious about the logic of a leisure battery as a starter battery. I get the need to match the batteries and I see that the engine battery can be in circuit with the primary leisure / starter battery for a short time at startup, but won't a battery designed for long slow discharge fare badly with starting loads? Also, why Varta rather than Yausa?

 

[aandncaravan]

Because the Varta LFD 75 is a Dual purpose battery that both Deep Cycles and Starts big Truck engines, it handles big currents better than most OEM Starter batteries.

 

The last Varta LFD 75 I fitted, was the exact same physical size as the ones I took out but had more Cranking Amps and greater capacity. Significantly. I would double check the physical size though, as while the LFD was much more powerful, I don't remember the ones I removed as being as 'small' as yours? The LFD75 is -

Length 278 mm

Width 175 mm

Height inc. terms 190 mm

 

 

A Motorhome Starter battery is used very differently to a Car because while a Car gets used every day, a Motorhome doesn't. It can be idle weeks, so the Starter battery can discharge a lot more deeply than a Car or van starter battery ever would, so benefits from that characteristic as well. That is why the bigger LFD90 makes a better Starter battery than the Fiat OEM, not just because the cranking amps are higher.

 

 

The Varta rather than a Yuasa because I know this size Varta works in Transits and also because it is Silver technology like the Ford originals, so a better match than the Yuasa in a Transit.

 

Despite the higher performance, they are half Ford's price.

 

 

I suggest you are cautious about the durability of the existing Starter battery, because I suspect when your ignition key turns, The Starter has the help of two other batteries.

Your Starter Battery might be worse than you think, but it isn't doing the work for that to show up.

 

[emclaughlan]

Thanks Allan,. That's a huge help. I'll go with that plan. You clearly know your stuff.

Thanks

Ed