Hobby and battery (yet another...)

[GTraus]

I have read several variants and answers of the following question but hoping for some fresh options:
I have a Hobby 495 UL (2017) without a battery. It has a Domitic 301-02 switching power supply that is active when connected to land-power or if I have the caravan connected to my towing vehicle (13 pin).

I want to add a leisure battery and preferably solar-panels. The 301-02 doesn’t have connectors (or doesn’t support) 12v input.

I have seen references to the Autark pack but can’t find any more detail about it.
I have also read the post about simply connecting a battery to a 13-pin connector and then connecting to the caravan when needed. Any thoughts on splicing the battery to the cabling from the front 13 pin connector to where it enters the Domitic unit? Since the unit seems to accept power from the towing-vehicle I’m thinking that might work.

 

[ProfJohnL]

Hello GTraus,

I am certain your plan might work, but it needs to be carefully planned and implemented.

Having looked at the instruction manual for the Domitic 301-02, this model does not support charging a battery, as it only produces 12.7V, and it only does this when 230Vac is connected.

You tell us your 12V systems work when the tow vehicle is connected. In the UK there is a device called a "Habitation relay" which interrupts the 12V power to some circuits when the tow vehicle is connected, I do not know if your Hobby caravan will have a similar function. If it does, then connecting a 12V battery to the 13pin tow plug may not work all your 12V systems.

The other concern i have is the Fridge. Usually when towing the fridges 12V cooling system is activated and supplied from the tow vehicles alternator. If you have the same connection to a battery, then the fridges electrical load will discharge your battery very quickly.

It might be worth replacing the 301-02 with the Domitic 301-03 which does have a 12 battery input and switching.

 

[GTraus]

I'm OK with running the fridge on propane when not connected to 220V. In fact the power tends to be so fickle in many camping-grounds that I switch to propane simply to prevent drops and spikes damaging the electronics.

If I do connect to the 13 pin I would probably install a switch to keep it off-circuit and only turn it on if I'm neither connected to the tow-vehicle or electricity.

 

[Jojo]

hi GTraus

where do you put the battery in the caravan( front, back)?

thanks

 

[ProfJohnL]

hi GTraus

where do you put the battery in the caravan( front, back)?

thanks

Some Hobby models may have a designated space of a battery, but if no space has been allocated then a heavy battery should be located as close to the axle as possible to minimise the yaw inertia it might create.

If you have a large nose load, you might consider fitting the battery behind the axle to reduce the nose load, and conversely, if you have a light nose load the battery should be located ahead of the axle.

Other practical concerns about batteries, During charging they can give of flammable gasses. If they are violently shaken they might spill battery acid, so they should be ventilated to the outside and sealed from the living space They should be in a container or locker and secured so they cannot tip over of move around.

 

[JTQ]

Other practical concerns about batteries, During charging they can give of flammable gasses. If they are violently shaken they might spill battery acid, so they should be ventilated to the outside and sealed from the living space They should be in a container or locker and secured so they cannot tip over of move around.

There are also VRLAs [Valve Regulated Lead Acid batteries] that in a properly managed charging situation, don't "give off flammable gasses", that only occurs when being overcharged as with a charger fault or with a battery failure.
A permutation on VRLAs is the GEL variant that has no liquid to spill and are sometimes fitted laying on their sides.
Both our Hymer caravans featured a factory fitted battery, both came with GEL batteries fitted within the habitation area and without any further venting provision, presumably to address spilling and gassing off issues.
I am aware the same practice is widespread in German motorhomes where again batteries within the habitation area are fitted, they use or specify a VRLA.
For fixing Hymer used blocks screwed into the floor to "fix" the base of the battery, and a woven "nylon type" webbing strap to fix it down, as simple and basic as that.
GEL batteries have features ideal for use as habitation batteries, but they need a charger with a specific charging routine to match their needs.

 

[GTraus]

Good point about the battery weight and location. I had planned on locating the battery towards the rear (under the bench in the rear-sitting area) but will reconsider. That’s where the local dealer locates the battery.

I will probably look at just in front of the WC-area or the fridge. That would place the battery slightly in front of the axle. It’s under the beds so I need to ensure I have a good enclosure and vent. Either that or the front storage if I can safely compartmentalize the propane from the battery. Not too afraid of nose-weight since even with a fully loaded caravan I have enough to spare both on the caravan and tow-vehicle.

I got some pictures on how I can change my Domitic 301-02 to handle an external 12v power-source from a guy who says he converted his unit, but I want to confirm it’s the same unit (and not a 301-03 or higher). If it works then I will document my conversion and post it here.

 

[Damian]

Either that or the front storage if I can safely compartmentalize the propane from the battery

Absolutely NOT allowed .

 

[GTraus]

Absolutely NOT allowed .

Yes sir. Message received loud and clear.

 

[ProfJohnL]

There are also VRLAs [Valve Regulated Lead Acid batteries] that in a properly managed charging situation, don't "give off flammable gasses", that only occurs when being overcharged as with a charger fault or with a battery failure.
A permutation on VRLAs is the GEL variant that has no liquid to spill and are sometimes fitted laying on their sides.
Both our Hymer caravans featured a factory fitted battery, both came with GEL batteries fitted within the habitation area and without any further venting provision, presumably to address spilling and gassing off issues.
I am aware the same practice is widespread in German motorhomes where again batteries within the habitation area are fitted, they use or specify a VRLA.
For fixing Hymer used blocks screwed into the floor to "fix" the base of the battery, and a woven "nylon type" webbing strap to fix it down, as simple and basic as that.
GEL batteries have features ideal for use as habitation batteries, but they need a charger with a specific charging routine to match their needs.

Whilst these options are available, so are the more conventional lead acid varieties, and manufacturers will not know which type their customers will choose. Despite the "safer" options, UK standards still requires a separate ventilated compartment for 12 volt storage batteries. Even if newer caravans do have low voltage charging systems, which in theory should not cause gassing, what happens if the battery or charger becomes faulty? I still support the fully room sealed compartment to control gas,acid or gel leakages.

 

[JTQ]

Despite the "safer" options, UK standards still requires a separate ventilated compartment for 12 volt storage batteries.

I think you actually mean the "standards" of a UK caravanning trade body, rather than "UK standards"?

As already said there is no arguments that with battery failures and charger failures, there could be gassing.
However, as already pointed out VRLAs are used in many motor homes and caravans, without being in sealed atmospherically vented enclosures, and I suspect if the Hobby had the factory battery option, it would have been.

 

[ProfJohnL]

Hello JTQ

In this case I'm not interested in the semantics of who set the standards except that the provision of an externally ventilated room sealed container is never a bad thing. It makes good engineering and safety sense to do so, even if the battery technology being used is inherently less likely to fail. You can never say never.

I have seen plenty (admittedly not all in caravans or motorhomes) of distorted gel batteries some with open cells due to both battery and charger faults, so the these newer systems are not as bullet proof as some would tell you.

Back the 1980's I had had to work on some caravans and motor homes where a battery has explosively failed. In older ones where the battery was not room sealed, the damage has been extensive to surfaces and furnishings, not to mention the smell and fumes. I have seen a couple of caravans that were totally destroyed becasue a battery out gassed and it was ignited leading to the caravan burning down.

Generally many people seem to fit and forget until something does go wrong.

It should never be forgotten that any battery used in a caravan or motorhome is storing energy, and the quantity of energy they may contain if released under fault conditions to do quite a lot of damage, especially if its released suddenly. When batteries fail they may do so in a variety of ways, and generally none of which are beneficial to humans. So regardless of the battery technology used, the most sensible thing is to segregate it from the habitation side of the vehicle.

 

[GTraus]

Just to give some feedback since I have seen the 12v/Hobby caravan question on several forums.
I met a guy at a camp-site who showed me his solution. His caravan is a 2020 model and mine a 2018 but things are relatively comparable so I basically copied what he’s done.
First a forewarning: There is a colour-code, but frankly after seeing the colours in the other caravan, the cabling in that harness, in my caravan and my harness I think there might be some leeway in how manufacturers define some colours. What was supposed to be orange was brownish in my harness so I don’t recommend going purely on what each coloured wire should be doing. Test it and confirm with the multimeter.

Whats needed: a multimeter, connectors (mostly female) and a crimping tool, 2.5 cable (red and black) of appropriate length, a wire-cutter and something to remove insulation off the wire-ends, some way to place a fuse on the wire to the positive on the battery (I used a 4 fuse box and fused wires going out of the battery too). I also added a simple digital volt-meter.

Using a multimeter I confirmed my 13 pin socket on the vehicle was functioning. I then opened the junction-box that is inside in the front-end of Hobby caravans (usually under a bed) where the 13 pin harness is connected to the caravan wiring. I then used the multimeter and car-connection to confirm what each wire did in the junction-box, mainly looking for the Trailer battery charging (10) and the earth for that (13).
Disconnected the vehicle and made certain there was no power connected to the caravan.
Connected the positive from the Trailer battery charging to the cable that would lead to the battery, and the earth to 13. Then created a small 10cm loop from that earth to the main earth at 11.
Used the appropriate gauge wire (it’s 2.5 in the 13pin loom), placed them in a flexible plastic tube and fastened it out of the way and to the battery. Placed my AGM battery near a vent. Put a 15 amp fuse on the positive leading to the battery, but have 5-10 amp fuses to the 2 USB and 1 lighter plug I added. The factory-included fuse box sees to the rest of the electronics.
Using a 140A AGM battery I get +3 nights off my CPAP plus normal use of lights, water-pump and phone-charging. I definitely need a better battery-charger (my cheap Primark one doesn’t cut it) or better yet solar.

Hope this helps someone in a comparable situation.

 

[GTraus]

Forgot to add:
12v does not keep the fridge on in the Hobby. At best it provides enough power to prolong the fridge being cold when on 12v but not much more than 4-6 hours. After that I noticed that the ice-cubes in the freezer started melting. I use propane for the fridge. At the lowest setting it does a very good job of keeping everything cold.