Wiring Additional Battery for Engel Car Fridge?

Sorry but I just cannot let this go without comment!

"...fully charge an aux battery under the bonnet to full capacity the battery will fail in a short time". Umm... you sure? A battery should last longer if fully charged, a flat battery will quickly die.

"...An auxiliary battery cannot be charged to anywhere near full capacity from a vehicle alternator..". Umm... no! It just takes longer, maybe a lot longer. As long as the charging voltage is greater than the battery voltage it will continue to charge the battery.

"...To fully charge a battery you need a DC - DC charger..." Umm... a DC-DC charger is one way to fully charge a battery, but many others come to mind, like solar, 240V smart charger etc...

"...This is the only method to satisfactorily fully charge and maintain your auxiliary battery." Umm... this is one way to do it, but FAR from the ONLY way.

12V vehicle batteries are a minefield, mainly because there is no "ONLY" way to do things. So much depends on your requirements and your budget that unless you fully know ones requirments, it is very hard to recomend a cost effective solution.

For example, a wet cell battery can be far more cost effective than an AGM if there is no proper charging system - neither will last so may as well buy the cheaper battery and keep replacing it (not that i am saying that is the way to go).

While the method you recommend is good, it is very costly (~$700+) and the original poster only wanted to run an engel fridge for an unknown duration - a simple low voltage cut-out may be all he needed to ensure his starting battery wasn't flattened.

Will get off my soap box now :)

Cheers

Captain

Stand by my post in its entirety. 100% correct. Unfortunately you are poorly informed about batteries and charging.

The method recommended is far from expensive. Ctek D250S about $280 Ctek D250S Dual $340 and you save on buying Redarc battery isolator around $120, and importantly you charge the battery to as close to 100% as possible. A vehicle alternator will charge a battery to 65% to 75%. Why lose 30% of a batteries capacity and reduce the life of the battery.
The Ctek D250S or D250S Dual is in fact the cheapest and best system you can use.

Captain

Agree with all your comments. There seems to be whole industries based on creating an insecurity in people's minds then having a whole heap of products to make them feel good again. Seen those new razor adds?

A simple dual battery and isolator setup would be my recommendation - professionally installed. A change of battery plus a low voltage cut out may also work.

DC-DC chargers - Oh the latest wonder product. It somehow uses more sensitive electrons to do what an alternator can't do. Load of rubbish! Marketing hype! I have a CTEK and have carefully monitored the voltages at different parts of the charging cycle. Almost identical pattern and voltages to what the alternator does in my vehicle. Maybe both CTEK and Toyota know something about charging batteries after all.

For a more complex and expensive setup a DC-DC charger such as the CTEK 250S or the newer 250S Dual (which allows easy connection of a solar panel) could be used to charge a battery away from the engine bay.

It may even be sufficient to replace the standard battery with something like an Exide Orbital combined with a low voltage cut out.

Paul has said in a follow up. "A vehicle alternator will charge a battery to 65% to 75%. Why lose 30% of a batteries capacity and reduce the life of the battery." For this to be true the alternator could not charge the battery beyond about 12.3 to 12.4 volts. This is simply WRONG. My alternator and many, many others bring the starter battery and the second battery up to full charge which happens to be 12.7 volts, measured after resting the battery after charging. I can run the fridge/freezer overnight before seeing the voltage drop to 12.4.

It is unfortunate that nearly every time someone posts this sort of question a deluge of disinformation is presented as fact.

Flynnie

Captain and Flynnie ignorance by amateurs is sheer bliss.

"My alternator and many, many others bring the starter battery and the second battery up to full charge" Technically impossible and especially in a Toyota. Late model Toyota's have one of the lowest charging capacities of all current brands. Suggest you check the Toyota Technical Data Sheets.
If you did bring your starter battery up to full charge you would have a battery life of around 12 months.

ROFLOL "I have a CTEK and have carefully monitored the voltages at different parts of the charging cycle. Almost identical pattern and voltages to what the alternator does in my vehicle." Of course, you are seriously joking. Unbelievable the rubbish you see posted there at times. A Ctek or any other modern quality battery charger has a charging cycle completely different to a vehicle alternator.

Another 12V thread that is turning into a "mines bigger than yours" contest :(

Lets take a late model Toyota, say the 200. Just so happens I have one. They actually have their voltage output regulated by temperature, not a simple fixed output. In hot weather the charging voltage can be as low as 13.1V, not good for rapid charging, but certainly minimises battery overheating.

But in cool weather, the voltage output can be greater than 14.5V and leads to rapid charging with minimal risk of battery overheating. These are not random baseless figures but real numbers taken from my ScanguageII that monitors a whole host of my ECM data.

And no need for name calling, resorting to personal attacks does nothing for your credibility. But just for the record, while I am a Charted Engineer, low voltage DC is not my speciality so I suppose you could say I am just an amatuer.

Cheers

Captain

Wow,
Alot of tech talk here.

I have a 3 year old AGM under the hood and she runs the Engle's (40 & 32 ltr) day and a half in stinking hot weather. Been the same from day one.

So many variables I don't think there is an algorithm to calculate the exact answer.

Just my experience.

Cheers all

Captain if you were a competent educated engineer you would toddle off and do research and realise how wrong you are. I don't have to try and bleep in the wind like you are. Our test lab proves what I post is correct. Why do you think so many companies make equipment for charging auxiliary batteries correctly and importantly to as near as full capacity of 100% as possible. Why do you think Mercedes and DAF use this equipment in their trucks to charge auxiliary batteries correctly if they could dump another battery in parallel and get it to charge properly. Perhaps you should study low voltage electrics and battery technology to become a professional and then make informed comment.

Paul

You remain quite wrong.

I wonder if you ever have had a multimeter in your hands and checked real cars and voltages and not just looked at sales brochures and speeches by spin doctors.

"Our test lab" - not you. Why don't you declare your private interest in this matter? Who do you work for?

Doubt it is CTEK itself. They make a good product and know how to market and have no need to resort to the disinformation you have been pushing today.


Flynnie

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Hi paulnsw
I would appreciate some advice

I have a 2005 rodeo diesel and tend to travel on 7-10 day trips and mainly use my 40lt engel as a freezer.
currently I have 2 batteries, calcium and agm and swap them around under the bonnet, use the agm when camping and occasionally used the spare backup calcium to jump start when needed.
I tend to drive a bit almost every day on my trips and the seems to recharge pretty quickly back up to 12.7 by my cheap meter.
I was going to hook up a dual battery system with isolator with the battery in the back and was looking into wire sizes and units when I noticed your reply.
I had heard about dc to dc charges but thought the cost was prohibitive, now I am thinking along your line.
Does the dc-dc recharged in a reasonable time?
I thought 12.7 was close to fully charged?
what sized wire do i need to run 5mt from my main Battery?
regards Mel
melaknee@optusnet.com.au

One of the very reasons vehicle alternators don't charge the start battery above 75% because the batteries would soon fail. The other reason that if you are using a deep cycle battery the last place to put the battery is under the bonnet.
Dennis good to see some informed posts here. Keep it up.

A lot of people, including battery suppliers, recommend battery types, charging voltages etc without understanding the environment that they have to work in.

and your professional qualifications are?

Hi there.

A few questions.
What model Rodeo? (To determine the alternator charge voltage)
How long will you be travelling each day, in hours.
Will you be stopped in one stop for a few days at a time? If so how many?

Why do I ask? Well, depending on the time the car has available to charge the battery and the load will determine how to design the system.

Its all compromises and fitting your use to a system. This is how I see it.
This is my opinion only. I do not do this for a living, I do not sell anything either.

* Driving a lot, stopping overnight.
Under bonnet dual battery, smart isolator, just use a wet cell, marine hybrid deep cycle.
Cheapest also.

* Driving a bit, stopping overnight.
Depends on your charge voltage. I would go AGM in the tray. They charge much quicker than a wet cell, but do not like heat. Smart isolator. Make sure you use BIG cables, the voltage drops a lot over distance at the high amps needed for charging.

If you have a really low charge voltage a DC-DC charger might be the go. (Some guys in D4D prados need a DC-DC to get enough charge into their AGM batteries for THEIR use. ie combination of drive time and load.)

I do not know your chrage volatage to make any determination.

* Not driving much, base camping for a few days here and there.
Maybe go solar only, or even better, go a dual battery system and solar at the same time.
I would do an AGM in the tray, C-tek Dual (or similar). Hook up the ctek to the alternator and also to an anderson plug some where so you can plug in solar panels while stationary.


Good luck with your system.
D

Hi JFRCN,

Sorry for the diatribe above, 12V threads seem to bring out the worst in some people. As there are many ways to accomplish what you want, its hard to advise a cost effective solution, one could spend many $$$ to have a Rolls Royce system when a simple system would suffice.

Your current battery (assuming its in god condition) should be fine to run the Engels overnight and still be able to start in the morning. If you added a cheap low voltage cutout, it would shut the Engels off if the battery did start to get too low. But now you may have warm beer - a real tragedy.

So, the next question is how long do you want to run the Engels for without restarting the Rodeo? And how close to help are you in the event of a battery failure? If its just overnight and you are in Caravan parks each night, then go the cheap option IMHO. But if more than overnight Engel running or you are reletively remote, then a 2nd battery would be the best way to go IMHO.

It is possible to simply run the Rodeo every day for a few hours to top up a single battery, but this can be a pain. Besides, a battery can fail for many reasons, an Engel left running is only one of a multitude of things that may cause a flat battery. It is far from unheard of for a battery to drop a cell for no apparent reason.

So, my suggestion would be a simple low voltage cut-off if you are in Van Parks each night (can run the Engel on 240V too) and are not travelling remote. However, if wanting to stay put for more than overnight, or if travelling remote, then go the 2nd battery IMHO.

Now the next lot of fun starts. What type of battery (deep cycle, AGM, Calcium/calcium, normal wet cell etc..) and how to charge and isolate it. As you have already seen, there are many strong opionions on how to do this and most suggestions will likley work, it just depends on your requirments that will make one way more cost effective.

What I have done for my last 3 vehicles is to use a hybrid wet cell as the 2nd battery. It is a cross between a starting battery and a deep cycle, it will allow you to start the vehicle if the main battery dies on you, but also gives reasonable deep cycle capacity for normal use. Others may suggest AGM's or true deep cycle etc.. and they are not wrong, but all have plus and minuses.

An AGM is arguably the best battery type, but it is more sensitive to temperature and relatively pricey. True deep cycle will give better performance if only running an Engel, but if you ever want to run a winch or some other high current application (start the vehicle) then you will quickly kill a deep cycle battery. Choose the type that suits your needs and budget best, there is no one answer here.

Most dual battery installations go under the bonnet (hot!) as this is typically the easiest place to locate it. It also minimises the cable run, thus voltage drop. I run AGM's in my van but use hybrid wet cells under the bonnet. I figure I can charge my van battries under optimal conditions thus get the value out of the pricey AGM's. But under the bonnet, the high temperature is a battery killer so I go the cheaper hybrid wet cell as its more cost effective. There are many other technical reasons why too, but this reply is already way too long!.

Now all thats left is to charge/seperate the 2nd battery form the main battery. Again there are several ways to do this and their cost varies considerably. One is a "dumb" solenoid, it joins both batteries together when the vehicle is running and isolates them when the vehicle stops. Connect your Engel to the 2nd battery and it will never impact on your main battery.

The next step up is to use a voltage sensing solenoid, typically a redarc or some other brand. These are very similair to the above, but moniotr the main battery voltage to determine when to connect/disconect. The majority of 4WD 2nd battery systems use this type of system, its relatively cheap, relaible and proven in the field.

Another way is to use a DC-DC charger, it too can isolate the battery but has the advantage of being able to charge at the correct voltage. For under bonnet installations I reckon its overkill but if there is a long cable run (say the 2nd battery was in the rear tray), then it will help in charging the battery properly, especially if the cables have been undersized - but it adss considerable $$$.

So, I have now got probably you totally confused for what seemed to be such a simple question (this happens on many 12V threads!). The one thing I know is that I have successflully used a Redarc isloator with a hybrid wet cell battery under the bonnet on many, many vehicles very successfully over ~20 years. Sure there are other ways to do this, but IMHO its the most cost effective way for the majority of 4WDrivers and their typical usage patterns.

Cheers

Captain

"The guys there know their business which gives you a warm feeling when you are relying on the system to do the job. " as long as you are happy is all that matters because their battery isolators drop the voltage among the most and consequently get an even lower charged battery.

Bill obviously Paulnsw’s comment has confused you, but he is correct, your second battery will get a lower charge, than your starter with this system. There are better ways to do it.

Hi Dennis

The ancillary battery I am using is a Exide deep cycle 80 Ah, its the largest they could fit under the bonnet (100series). Should I be able to charge it up to the 12.7V the same as the starting batteries or do deep cycle batteries, fully charged run slightly less than a starting battery. I was previously advised that is the case.Mine is running around 12.5V. If I did get it charged to the 12.7V how much more time would we get form the battery.

Cheers Bill

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Hi Paul

Thanks for the follow up

I guess I should be following up our supplier to see what can be done. Deep cycle batteries are expensive and as we are about to leave on a 9 months trip into the great outdoors I need to make sure the system we have will work successfully over that time without failure and we are getting the best results possible.

Cheers Bill

Forgot to ask what voltage should I be achieving when the deep cycle battery is fully charged, 12.7V? the same as the starting batteries (2-off) turbo diesel

Bill when you come across these people travelling with power pain of which there are heaps, you will be so grateful you have a system that is so functional and works and gives your battery the best chance to get to 100%.
Download the Ctek manuals and product sheets and read for yourself.
http://www.ctek.com/EN-GB/dcdc/d250s-dual.aspx

Under no circumstances let anybody flog you a calcium battery when it comes time to replace your Exide deep cycle. Technically you cannot manufacture a deep cycle battery using calcium technology. Calcium are magic cranking batteries, but useless for cycling.

Voltage is not a good guide for battery capacity. Voltage is variable for temperature, type of battery and period of time since it was charged. You can have a battery that reads 12.7V and is useless.

When you are discharging your battery with a light load, a volt meter can give you a reasonable guide for your system, and will give you a good understanding at what capacity you have left after a few weeks use. Try to avoid discharging the battery below 12.2V.
Variable for type of battery and temperature. First figure more suitable lead acid, second AGM
100% 12.7 to 12.8
75% 12.4 to 12.6
50% 12.2 to 12.3
25% 12.0 to 12.0

Bill what equipment will you be looking to power?
Will you be stopping much at locations for a few days?

Hi Paul
Will follow up on the info you have sent through
We have an engel fridge 40 litre and whilst we are traveling the fridge in the van.

The Ctek will it monitor the battery condition ie. not allow the battery to go below 12.2V or do we need a separate monitor to control the low level.

The length of our stay will be around two to three days when off 4x4 without the van in tow and staying at caravan parks where I usually hook the engel up to 240V.

Did buy a AGM for the van but was advised the Exide was OK for the car ancillary battery. Will buy AGM next time
Cheers

Hey Paul, I have a Ctek 15 A mains charger, is the 250s a DC-DC charger? Looks like it is, you dont happen to work for them (Ctek I mean) do you and maybe can land me a good deal??

Thanx

Bill I take it the fridge in the van is 3 way

The Ctek D250S Dual does not operate as a low voltage battery cutout, it is only a battery charger and solar regulator and can be used as a 240V battery charger with the addition of a 240/12V 29A power supply which is under $50.

How do you intend to charge the battery in the caravan?

If you do any free camping which can save you a hell of a lot of money now many caravan parks in the $35++ a night bracket, 3 nights free camping is $105++ saved, Buying the correct equipment and/or a solar panel can soon earn their keep. Considering quality brand name solar panels are so cheap now 85W $400 and 140W $660.00. Having a power system makes one hell of a difference. We travel extensively and have not been into a caravan park in 5 years. Important to have a good power system to keep the Mrs Bill happy so she can watch a bit of TV when she wants and have sufficient lighting to cook with.

The Exide if it is a deep cycle battery is not an issue for the car auxiliary battery.

When you consider the cost of the Ctek D250S Dual $340 includes a battery isolator about $120 so now the Ctek D250S Dual is $220 is super cheap for the job it does and includes the latest technology MPPT solar regulator if you want to add a solar panel.
Your gain would be minimum 30% and could be as much as 40% getting your battery 100% charged. The important thing is you will get substantially better battery life because the battery will not sulphate and not deteriorate like under charged batteries do. If you read the deep cycle battery manufacturers data they all recommend you ensure a battery is 100% for maximum life.
Having been involved in a professional capacity for over 20 years in ambulances, trucking, fire engines, military vehicles, aeroplanes, boats auxiliary power systems we know what works and what does not work as everything is triple tested and evaluated.

Hi Paul

Firstly I appreciate you taking the time to explain the ins and outs of low voltage charging etc.....

My van has two 80 watt solar panels to keep the van battery fully charged which by the on-board meter it works ok. The Anderson plug on the car is connected to the ancillary system to assist if necessary in charging the van battery, it probably doesn't have sufficient power to work anyway. The 3 way fridge during travel is connected to the ancillary car battery via the 7 pins plug to keep it working whilst the car is running. (not to the van battery which is used lighting TV etc) I think this part is all good, all installed buy the caravan provider which is well respected in the market place.

I am not electrical/electronic engineer, my experience is mechanical, but I work for a company who does have these people. They have agreed with your comments, only wish I had talked to them before I went down the track I have. On reflection in my first cruiser the battery did have a melt down which was explained to me as my fault in the way I used it. May have not been the case!

Have asked the guys to check out my ancillary battery and it isn't a good as I thought, actual figures are around 12.3 V with no load on it for three to four days and traveling to and from work 30 - 40 minutes each way happy charging all the way.

Will be discussing the info you have provided with them tomorrow (the company has been in business for 50 years electrical/electronic lighting, mining work shop and emergency services) and see what we can do before we head off at the end of the month. It may have to wait till I get back but I think I will eventually get it right.

From the figures you quoted my battery is at about 50% (the other guys confirmed this) we have a fair way to go to get the best out of the system. The new costs to get it up to speed will pay for it self in the long run if the battery last longer and work efficiency.

Your type of input is always worth while and obviously by this blog has ignited a lot of discussion, keep it up.

Cheers

Bill

Bill "The Anderson plug on the car is connected to the ancillary system to assist if necessary in charging the van battery" is a bad bad idea with you having 2 x 80W solar panels. What happens you get no charge from your vehicle of the battery in your caravan above 60%. Now what happens your solar regulator sees the high voltage from the vehicle and thinks your batteries are charged and consequently shuts down your solar panels. You can travel all day and start off with the same as you started the day. We never ever connected the vehicle alternator into the auxiliary battery system in your case your caravan.

Your 3 way fridge is also connected incorrectly "The 3 way fridge during travel is connected to the ancillary car battery" The 3 way fridge should be connected to the main vehicle start battery in conjunction with a Redarc battery isolator or an ignition powered relay.

"traveling to and from work 30 - 40 minutes each way happy charging all the way." you see the issue is, another battery in parallel with your main vehicle alternator will never fully charge. The other issue is if you have an electronic switching battery isolator they are worthless junk as they drop the voltage to much. You need an electronically controlled mechanical switching battery isolator like a Redarc.

When you are travelling, your Engel 40L should also be powered from your main vehicle start battery and changed over to your auxiliary battery automatically with a double pole single throw Bosch mini type relay. This will then ensure your auxiliary battery is fully charged up to as near as 100% as possible so when you switch off your engine, the relay drops out, switches your fridge automatically back to the auxiliary battery.
Bill there are circuit diagrams etc for all this and ore on RVtravelau. The professionals are there and can inform you on anything electrical and great ideas for your caravan. Wealth of caravan and motorhome knowledge.

Hi Paul

Thanks again for your feed back

I never considered doing what you have suggested, I do have sockets connected to the main batteries, will be using them from now on, after the trip I will install the Redarc isolator, and disconnect the 7 pin from the ancillary battery. Thanks for the tip on the Anderson plug, had it fitted as a result of other recommendations, sounds right to me now.

The Ctek will also be on the to buy list, have followed up the info with the guys at work and now understand its the right way to go.

Thanks for your input hope the original guys has followed the blog as he should now have the best info to go forward with his project.

I am now off to RVtravelau.

Cheers

Bill

PS. I am the retiring operations manager for 'Burn Brite' part of 'Ampcontrol'Newcastle

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pepper - with your system you will do a lot better than some others with more sophisticated systems.
I have an old guy down the road who does exactly the same as you and uses to large century 4WD starter batteries in parallel. He runs his Engels and watches his voltage carefully and achieves around 5 years from his batteries.

Exactly Dennis, there are more ways to kill a cat than stuffing its mouth full of jelly beans. LOL

Norm, it's hard for some who delight in making it hard!

So it would appear