Installing a DC-DC Battery Charger

I want to install a CTEK DC-DC battery charger in my 2013 Nuevo. I would be grateful for advice from anyone who has installed one.
Bernie

I've not done it but know what is involved. Before jumping in with technical information can you let me know what your expectations are by replacing the existing charging circuitry with this device?

Might be worth taking a look at the http://www.aandncaravanservices.co.uk  site it gives some useful info on battery to battery chargers .

I was hoping for a faster time to charge the habitation battery and for 100% charge rather than the 85% from a split charging system. I have only one habitation battery and also an 80 watt solar panel fitted. Solar panels help in the summer but not in the winter. A DC-DC system seemed to be an ideal easy system to add if there were no problems.

bernieproberts wrote:I was hoping for a faster time to charge the habitation battery and for 100% charge rather than the 85% from a split charging system. I have only one habitation battery and also an 80 watt solar panel fitted. Solar panels help in the summer but not in the winter. A DC-DC system seemed to be an ideal easy system to add if there were no problems.

Which Sargent system do you have, I guess an EC325 or EC328 but it may be an EC500 - Reponses will differ depending on your existing set up but in no case will you see a 'significant' increase in rate of charge and for me that would mean the cost of installation was unnecessary.

My Nuevo has a EM50 and a ES328PSU.

The battery to battery charger (B2B) uses the starter battery to charge the leisure battery whilst the engine is running and relies on the alternator to replenish the starter battery. (The Sargent EC325 has a 'fast charge' facility built in but other Sargent models don't).


The EC328 connects the starter and leisure batteries together when the engine is running so the system has to be rewired to stop this happening if a B2B is installed.  The alternator in an EC328 installation will reduce charge when it thinks both batteries are reaching full capacity whereas a B2B will only consider the charge in the leisure battery.  In new vehicles with a smart alternator where the starter battery is never charged past 80% capacity, this is a benefit.  In older vehicle like Bernie's Nuevo the benefit is minimal, if any.


There are a couple of permanent 12v feeds in the habitation area and (in newer vans) one is to the Truma combi control system.  A forum member found that in the few milliseconds that it takes the B2B to get up to voltage, the Truma can lose its settings so circuitry had to be designed to cover this.

The EC328 includes a dual channel solar controller that charges both leisure and starter batteries at the same time.

In my opinion the EC328 is the best system Sargent have produced to date (including its two successors) so, personally, I would leave well alone.

bernieproberts wrote:I want to install a CTEK DC-DC battery charger in my 2013 Nuevo. I would be grateful for advice from anyone who has installed one.
Bernie

Bernie, If you look at almost all the B2B instructions, they all stipulate very fat, uprated cabling as essential to the installation. Isn't that a bit odd when all the B2B's marketing claims are that it is the device that gives all the charging benefit? If the B2B is so good at increasing the charge rate why is it necessary to uprate the cable as well? 
The difference in charge rate is usually only raised by a few amps, as witnessed by the CTEK XS250's maximum 20a output, so the cable does not need uprating for that reason.


The real reason is that it is the cable that makes the biggest difference, the contribution from the B2B is relatively minor. 
If you just run decent sized 10mm+ cabling from the Alternator to habitation area battery, via a big 200amp relay (just £7 on eBay), you should see the voltage at the habitation battery rise to very close the same as that at the Starter batteries, 14.4v. 
On quality batteries you can see an increase from a less than 8amp charge, rise up to 18amps charge per 100Ah battery, nearly 36amps for a typical 200Ah battery bank.

The quality cabling and big relay, stops the voltage drop that would normally be seen, ensuring the batteries can pull the full current they are capable of.

Continental built motorhomes with just quality cabling and minimal connectors, usually achieve close on 14.4v charge rate from the Alternator, without any B2B or other electronics. The picture below is of a Hymer we worked on that demonstrates this perfectly.

All you need to do is, literally, run decent cables from the alternator to a big Split charge relay and then onto the habitation batteries. You do not need to interupt the old EC32x/Split Charge system. That can stay exactly as is in parallel.
The ECxxx units have no control over Alternator charging rate, all they do is trigger the relay.

When the Starter battery is 'full' it will stop drawing charge from the Alternator, even though the habitation batteries may be pulling 20amps into 2 x 100Ah batteries. 

Can we suggest that you try the 'Cabling fix' first. If you are not happy, it is easy to just swap out the new big Split charge relay and replace it with a B2B at a later date, as that is all some 'B2B's' are.

Whatever you do, please don't use the CTEK XS250  which is often marketed as 'the' B2B, it is actually one of the worst.
For a start it only has 20amps output, when the best 'pure cable' systems can achieve over 30amps, as demonstrated above, without a B2B.


Someone, only yesterday, posted in another thread on another forum saying,
"I remember a long time back being slightly miffed when you criticised certain B2Bs of which I was a fan. On the following van rather than install a B2B I, a little sceptically, adopted your beefed up wiring and chunky split charge relay recommendation. 
I'm glad I did as I achieved a great result at a fraction of the cost of a B2B".
 

Have a look at this web page : [You must be registered and logged in to see this link.]  it tells you how to 'Turbo charge' your Alternator charging system for £25. Skip down the page until you see the big picture of the 200Amp Split charge relay and start there.
It explains things like how a 200amp relay will have massive contacts inside that will reduce voltage drop, because they act in the same way fat cable does, and makes most people wonder why Motorhome manufacturers fit 50amp relays and thin cable?


Your batteries are key, they are not all the same. The new Yuasa L36-EFB with Carbon + technology can charge over 1.7 times faster than a good conventional battery and at least twice as fast as the typical Platinum. The age of the batteries will also impact the charge rate.


In the picture below you can see a well set-up system (no boost electronics) charging from the Alternator at 14.33, just a fraction less than the 14.39 we were seeing at the Starter battery/alternator. And that was with the load of the Fridge also running on 12v Alternator power.


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Thank you all for the information and advice.

 

I have just installed a new habitation battery, an AGM Trogen. I connected my volt meter to it and drove the motorhome on a short journey. The voltage crept up to 13.2 volts. When the engine stopped the reading was 12.7 volts. The Sargent display gave it as 12.4 volts.  When I connected up to the mains voltage my volt meter read 13.7 volts and when it was switched off it read 12.7 volts.

 

The CTEK B2B device seemed simple to install with the large cables and fuses. However if it requires the split relay housed inside the EC328 to be disconnected I will leave things as they are as I do not have a circuit diagram. I will rely on Auto-Sleepers and Sargent motorhome circuits and the AGM battery.

Thanks Roopert for all your information.

 

I would not disconnect cables from the EC328 as I do not have a wiring loom diagram for the Nuevo. When I bought the Nuevo I asked Auto-Sleepers for one in case of problems on holiday but they refused saying it was their Intellectual Property. I can understand the equipment joined by the wiring loom had IP but not the cables joining them.

 

I did ask a local Automotive Electrical Garage about installing a B2B and they thought it was OK to run it in parallel to the split charging circuit as they were only charging the habitation battery. I am wary of doing this in case it caused damage to the motorhome electronics.

The split charge relay connects the leisure battery and starter battery in parallel when the engine is running so for charging from the alternator the are effectively one battery.

The B2B charges the leisure battery from the starter battery with the alternator replacing the energy lost in the starter battery. If the two batteries are connected in parallel by a split charge relay then the B2B does nothing.

Peter Brown wrote:The split charge relay connects the leisure battery and starter battery in parallel when the engine is running so for charging from the alternator the are effectively one battery.

The B2B charges the leisure battery from the starter battery with the alternator replacing the energy lost in the starter battery.  If the two batteries are connected in parallel by a split charge relay then the B2B does nothing.

Yes once the Starter battery and habitation area battery are linked they can take whatever charge is available from the Alternator, but they will not behave as one big battery.

Each battery will behave as an individual unit, only drawing  the current it needs, a Leisure battery pair could be pulling 20 amps and the Starter battery just 1 amp.
If it behaved as you seem to think, a Motorhome starter battery would be severely overcharged the first time the habitation batteries were used in anger with a resulting life time of only weeks. As many people have seen Motorhome Starter batteries of over 8 years old It tends to suggest your understanding of how they work isn't correct.


You write, "The B2B charges the leisure battery from the starter battery with the alternator replacing the energy lost in the starter battery"  which is  also not correct. 
The Alternator supplies the power directly, the Starter battery does not get involved at all because the Aternator has a higher Potential Difference.
Visualise the Starter battery as a water tank at 12.6 psi. Further imagine the Alternator being a pump that pressurises the 'pipes' at 14.4psi. Obviously the Alternater 'pump' will pressurise the lower pressure 12.6psi 'tank' preventing anything coming out. Any demand for 'power' will be satisfied by the higher voltage , 'higher pressure', unit directly.



You also write, "If the two batteries are connected in parallel by a split charge relay then the B2B does nothing", sorry but that is wrong again for the exact same reason of the varying Potential Difference, 'pressures', between the two charging circuits explained above.

A typical UK motorhome has an Alternator charge voltage at the habitation batteries of less than 13.8v, as witnessed by the above Posters' 13.2v.
If you create a direct, efficient wiring path to the habitation batteries of 14.4v, either by decent cabling or a B2B, then the higher Potential Difference of the B2B's 14.4v will effectively 'out pressurise' the Sargent split chargers 13.2v.

Although the Sargent Split charge system is still in place it will effectively be inactive.


If Bernie's existing Alternator charge voltage is 13.2v, then using decent cabling to get 14.4v to the habitation battery will result in at least double the charge rate. 
If you consider that 13.8v is the voltage used for 'trickle charging' and 13.2v as an ultra low long term 'maintenance/Float' voltage, then clearly upping the 13.2v to 14.4v is going to have a major impact.

Alla, I can not replace the motorhome wiring with thicker cable to achieve the 14.4 volts to charge the habitation battery. I wonder why Auto-Sleepers and Sargent don’t do it.

However am I correct in thinking that a B2B would give 14.4 volts to the habitation battery, thus allowing more current to flow into it. Resulting in a fully charged battery in a quicker time.

As the B2B would be the main supplier of current to the habitation battery making the split charge system inactive. Could I install a B2B without disconnecting the Sargent split charge system?

bernieproberts wrote:Alla, I can not replace the motorhome wiring with thicker cable to achieve the 14.4 volts to charge the habitation battery. I wonder why Auto-Sleepers and Sargent don’t do it.

However am I correct in thinking that a B2B would give 14.4 volts to the habitation battery, thus allowing more current to flow into it. Resulting in a fully charged battery in a quicker time.

As the B2B would be the main supplier of current to the habitation battery making the split charge system inactive. Could I install a B2B without disconnecting the Sargent split charge system?

Bernie, It isn't just Autosleepers, it is Bailey, Swift group, Explorer group, etc.  

Almost all B2B instructions stipulate that the wiring is uprated to gain full functionality. You can install a B2B without uprating the wiring but the old wiring will be a limitation and unlikely you will obtain full benefit. 

There is a device made by Schaudt, the biggest motorhome charger manufacturer in the world, that is specifically designed to operate with low Alternator voltage input, such as you have, yet still deliver 14.4v to the Sargent Power Controller/Charger.

Unlike conventional B2B's, which literally bypass the Sargent by running Starter Battery to Habitation battery, this unit is designed to work with all Motorhome power Controllers from Sargent to CBE, just as you might expect from a company that have been in Motorhome electronics since the early 1990's. 
It fits into the Starter battery/alternator feed going into the Sargent. That ensures the Sargent is always fed with exactly the 14.4v it needs regardless of the Alternator voltage, it works even with Brake Energy Recuperation vehicles. 
Because it works in harmony with the Sargent's Split charge system, not in parallel, you don't need to make ANY changes to the Sargent. 
Because of the unique way it installs the Sargent does not know anything has changed, the Ecxxx just receives a consistent 14.4v from the Alternator.

The Schaudt WA121525 is the CTEK 250 'equivalent', it isn't the cheapest Alternator Booster but is the best, especially if you want to avoid lots of wiring. Can be found on eBay at about £145 as opposed to the CTEK 250 at about £230.

We have a web page giving free advice to people wiring their own Camper Van, particularly installation notes aimed at getting the fastest charging out of the Alternator, most of it is irrelevant to your issue, but near the bottom of the page there is a comparison to the CTEK 250XS which shows how the WA121545 (larger version) can literally achieve half the charging times of a CTEK 250.
A manual for the device can also be found on the wiring your own Camper Van web page.

Note that the WA121525 has typical output of 25amps, compared to the CTEK 250's typical 18amps output once it gets warm and starts to back down the charge rate. 


Because the WA1215xx unit is so easy to install, it is also easy to remove to fit to the next vehicle, thus protecting the investment.

Sorry one more thing, the Schaudt Wa1215xx boosts the alternator voltage for all the alternator driven items, not just the Split Charge system. So running the Fridge on the 14.4v it is supposed to have, as opposed to 13.2v, will obviously also be more efficient when driving.
A conventional B2B won't do that as it focuses solely on boosting the habitation battery voltage.

I disagree with those above and think you would see a phenomenal difference because your 13.3v is even lower than the average 13.8v we see. 
An Alternator charge of 13.2v, that is even lower than a mains chargers 'trickle' 13.8v, just won't get your AGM battery fully charged, probably less than 80% most of the time, and take forever to get just that far.

I would be very surprised if fitting a WA1215xx to your existing system didn't half the charging time as a minimum. Probably improve things by a factor of 3?


Are you aware that the Trojan AGM batteries are best charged at 14.7v and short term Float charged at no more 13.5v? Are you also planning to replace the mains charger and Solar regulator to suit this special battery?

bernieproberts wrote:What a can of worms I have opened. The people I bought the battery from said that this AGM battery would be a match for the one I had and discharge at a lower capacity, charge faster and perform more cycles. What battery of the Group 27 would you recommend for the Sargent EC328 system.

AGM batteries can perform more cycles and the Trojan is one of the few AGM's that actually has thicker plates to make them more suitable for Leisure use. However, that will only be achieved if an AGM is charged as per design, and clearly a 13.2v Alternator charger is no where near the most basic 14.7v most AGM's need to charge fully.

Likewise most Sargent Solar regulators don't have an AGM charge profile either, nor do any Sargent mains chargers.


Back in 2014 Hymer did a deal with Banner to fit  AGM Car Stop/Start batteries as Leisure batteries. None of the motorhomes had AGM chargers, solar regulators or adapted Alternators.
Hymer and Banner issued a press release saying that they would charge up fine on a Gel charge profile. 
They had failures in their thousands, actually hundreds of thousands and the German Forums where the first to be hot with failures and a big outcry. 
The UK followed about a year later after premature failure of batteries that were claimed to last about 8 - 10 years, but didn't make it to 2 years.

It cost Hymer a lot of money to rush through new Mains Chargers and Solar Regulators that were AGM optimised, but only this year have they addressed the Alternator issue. 

Hymer ditched the Banner AGM's in a 'smokescreen' to try point a finger at whose fault it was and switched to Varta AGM's.
The forums continue to report premature AGM failures, none of which have ever been replaced under warranty. 
Apparently, according to Hymer, Banner and Varta all the issues are down to the owners not looking after the batteries!! 


Then it emerged in 2018 that AGM's have not lived up to the promises made by the marketing men and were having a life as a Starter battery of about 3 years, when Lead Acid Starter batteries typically lasted 8+. Remember AGM's cost twice as much so should be giving 16+ years life, not 3.
Last year many major car manufacturers switched over to the new EFB (Enhanced Flooded Battery) wet acid technology, which being a wet acid based battery, works on almost any charger. 


Alpha Bbatteries are one of the few specialist battery retailers we know that understand what they sell. They have warnings on their website that states that for optimum life an AGM battery must only be used with an AGM optimised charger.

I bet your battery "specialist" also 'forget' to mention that AGM batteries are more prone to thermal runaway, leading to fire and even explosion? 


In the September 2018 magazine the Caravan and Motorhome club wrote : 
"In general, it's probably best to avoid AGM batteries unless you are absolutely sure your charger is suitable, as the otherwise excellent performance counts for little if the performance is compromised through damage by inappropriate charging". 



Just as the Automotive world start throwing out AGM's and the Leisure industry recognise their short comings, Swift begin their rollout in motorhomes and around we go again.


For the best Motorhome batteries, have a read of our 'Battery Technology' webpage :  [You must be registered and logged in to see this link.]  and before anyone starts thinking it, we don't sell any batteries. It is independent advice.
Maybe have a read of our home page as it describes where our battery expertise has come from?

I have been following this thread with a keen interest. Its good to receive up to date advise from a professional.
Thank you for your time and expertise

Roopert wrote:One further update: earlier I suggested that the D250SA may not be suitable in terms of distributing charge from its solar controller to both batteries. Further research suggests that this is true:

Will the CTEK D250SA charge my starter battery as well as the leisure battery?

If the conditions are correct it will put a maintenance charge into the starter battery. The correct conditions are:

   Solar panel fitted and working
   Leisure battery fully charged.
   No loads on system
   Starter battery between 11.5 & 12.6V

Under these conditions the D250SA Dual will give a 3 second pulse of approx. 13.6V and whatever current is available every 30 seconds, this function is designed to offset any self discharge within the starter battery.

This would make the product unsuitable for most users here, IMO, because most camper users take significant power from the engine battery (e.g. for the cab radio) while they are parked up, and maintenance charging would be insufficient to put that power back quickly enough.

Roopert, Thank you for that I didn't know the rate was so low, however when you think that these are primarily based on designs from the boating arena, where a Boat Starter battery will never have any drain on it to discharge, it is perhaps understandable.
A boat Starter battery won't have an Alarm, Tracker, "Body computer waiting for a Remote key fob to unlock the door", or Radio, etc. 

Some of these products that are sold as 'suitable' into the Motorhome arena are not always what they seem. We think the CTEK and Sterling products are designed for boating, but "because they both use a Split Charge Relay" they are 'directed at motorhome's' as well.
Yet the above demonstrates just one of the subtle differences that have grown between the two.

20 years ago, motorhome electronics were much simpler, more like it is now on Boats, there were no Alarms, 'Remote' to unlock the doors, Trackers, etc.  Differences between Water craft and motorhomes are now a gulf apart, as a result some of the products that might have been appropriate long ago, like boat style B2B's, are not the ideal option any more. 



We would suggest that the CTEK 250 Solar regulator is not just flawed in the area of charging, but in efficiency as it performs well below the best motorhome dedicated Solar Regulators, such as the Votronic MPP range.

'We' received an email on Tuesday about work that was done on Monday, that said - 

"It was great meeting you yesterday, the Votronic Mppt controller is working fantastic, such a massive improvement. Paul W". 

We are used to such comments after replacing the SunSolar's, Steca's and generic eBay style units, but this Votronic MPPT 250 replaced a PWM Schaudt LR1218, which 4 years ago we regarded as the best of it's class and was one of the few Dual battery regulators of it's day. 
After the replacement regulator was fitted, we saw a better than 30% improvement in Solar harvest, which is equivalent to upgrading the 200watt Solar Panels to 260watts.
That shows how things have changed in 4 years never mind 20.


Also very, very relevant to this thread is this users real world experience - 
Recently a big name Motorhome Converter delivered a new vehicle to a customer who discovered the vehicle had a Brake Energy Recovery/Euro6 optimised Alternator whose voltage varied from 13v to 15+ so wasn't charging the habitation batteries properly through a standard split charge relay. 
The company admitted it was their problem and agreed to fund the owner fitting the necessary electronics to resolve the issue.


This was the update published on a forum just two days ago on the 10th April 2019 :

"Wee update. I have the Schaudt WA121545 from Germany. Wildax are aware and are keen to see how well it works. 
They have been using B2B's but have stopped doing so because of "issues": not sure what these are. 
Today I temporarily installed it in the van without the voltage and temperature sensors connected. With engine running at tickover I have a constant 14.41v at the leisure batteries (Banner Energy Bull). Fridge is now running OK on '12v' with engine running but I wasn't prepared to take a temporary installation onto the open road so I can't be sure it is 100%. 
I reckon once I have a permanent installation with sensors included, this is going to be a class bit of kit".

I have now swapped the AGM battery for an EFB battery. Thanks for pointing out the charging voltage required for the AGM battery. Taking the motorhome for a run with the old discharged battery the voltmeter reading across the battery read 13.8+ volts. I am happy now I know the Sargent system is working correctly.

It was interesting that no one reported that they had a DC-DC Battery Charger fitted to their Motorhome. I will look into the advantage of installing the Schaudt WA121525 but it looks a little tricky to install whereas the B2B is a straight Starter to Habitation battery connection.

I have a Sterling B2B charger diy fitted 4 years ago. No problems so far charging 3 x 110 amp sealed lead/acid batteries ( I have a compressor fridge)
Used 25mm sq cable to reduce voltage drop and replaced the miserable Sargent 12amp battery charger with a Victron 30 amp unit.
Its been a case of "fit and forget" and copes well with frequent 2 month trips to France