2nd Battery, Inverter and TMV Install

[Dwarfer]

Just thought I’d post some pictures of the mods I’ve done to my van

I bought a battery box and 125ah leisure battery from eBay to install in my van, then discovered the battery I already had was a standard car battery not a leisure battery, so I bought another identical 125ah battery so I now have a matched pair.








The two batteries are wired in 16mm cable with a 100A fuse as close as practical to each positive terminal. Everything joins up in a terminal box witch is just a couple of earth terminal blocks screwed to a piece of wood inside an enclosure. The inverter and a 12v socket I have wired from this terminal block with inline fuses, the rest of the vans electric are unchanged.



The 500w pure sign inverter is switched by an 80A relay through a switch next to an un-switched socket which is on a fly lead from the inverter output. I did consider wiring the inverter into all the caravan sockets but decided against it due to the complexity. I may do this at a later date.







I found when trying to conserve water I was wasting a lot fiddling with the two taps trying to get the shower to a good temperature, and switching the water off between getting wet and rinsing left me back at square one fiddling with the taps again. A thermostatic shower would be the solution but they aren’t cheap and installing it wouldn’t be easy so the next best thing was to fit a thermostatic mixing valve which is what I have done here.



I have set the valve to 38 degrees C so turning the hot tap on full will give a nice warm shower and cold can be added if required. The valve hose barbs and “T” piece cane to about £15 on eBay.

All in I think I’ve added about 35kg to the van but as we put all the heavy stuff in the car im not realy concerned

 

[Dustydog]

I like your hot shower water mod . Well done :cheer:

 

[Damian]

The only problem with your setup is the placing of fuses in the battery box.

 

[Dwarfer]

The only problem with your setup is the placing of fuses in the battery box.

What problem do you see with the fuses being inside the battery boxes?

 

[chrisn7]

You have the batteries vented, but it is still undesirable to have the potential for sparks from a blown fuse in what is a normally closed battery compartment, as vent tubes do disconnect rather easily...

 

[Dwarfer]

I see your point but to place the fuses outside of the battery boxes would have placed them so close to the other end of the cables to render them practically useless. I did consider not having fuses at all between the two batteries but as the battery vents are piped outside, the batteries are maintenance free with a valve to limit gassing, the fuses are encapsulated and the fuses holders while not being sealed have a very narrow flame path I consider the risk to be minimal and a lot less than the risk of a fire which the fuses are there to prevent. This is probably a pretty small risk as well.

The most likely way one of these fuses will blow is if I do something stupid like touch the two battery clips together while one battery is still connected on the other end.

 

[JTQ]

I carry a second battery but due to the van' payload I need to carry it in the car boot; using my old but trusty Labcraft TP2 unit.

With what I see as very poor payloads in modern vans, fixed dual 125 Ah battery installation can only be a viable option for very few newer caravan users.

My system has independent 12 volt systems sharing the same negative, and the portable [in my case 60 Ahr] battery is configured to be able to supply the non essential services such as TV and High Fi. The two are charged via a Morningstar Duo solar controller.

 

[Damian]

The only problem with your setup is the placing of fuses in the battery box.

What problem do you see with the fuses being inside the battery boxes?

Simply that it is not in accordance with 17th Edition regulations, which you must adhere to when doing any work on your van.

 

[Gafferbill]

......I cannot see any logic for your battery and inverter set up.

The problem when off grid is how to keep the caravan battery charged.
Two discharged batteries are no better than one discharged battery.
If you have a charging method then it only needs to charge one battery.
It is true you can charge at home and set off with double the charge but you might as well keep the second battery portable and carry it in the car for connection as required.
Some sites will charge a portable battery for a small fee......your set up does not lend itself to this.

I find it better to also keep the inverter portable.
I have a 600 watt inverter that I can power from the tow vehicle batteries whilst on site and stationary....fitting under the bonnet takes about a minute and it provides mains voltage via a lead to the normal EHU caravan connection.
This way the whole caravan is powered up and I can run the on-board 20 amp smart charger to charge the caravan battery........also handy for running a 600watt hair drier for the wife!
The vehicles batteries are obviously discharged but this is monitored by a volt meter and enough charge has to be left to start the vehicle's engine.
Like all modern vehicles it is fitted with a highly efficient alternator that can recharge its batteries at up to 75 amps when the engine is running.

 

[Dwarfer]

I don't have a copy of the regs at hand but being that I am a qualified electrician with 17th edition wiring regs, a former AP electrical and formar process engineer within explosive environments for the MOD, I am not aware of anything in the regulations which prevents a fuse being installed in this location. Please correct me if you Know different.

My oppinion is that this fuse is there to protect the length of cable from the battery terminal to the terminal block and nothing else. It is rated well above the total of all loads in the van and of the fuses supplying all the circuits within the van so will not blow due to any fault other than one on this cable or the terminal block itself. If it were fitted outside the battery box there would be 900mm un-fused cable and only 100mm fuse protected so pretty pointless and in all likelihood if a fault occurred the cable would go up in smoke burning through the battery, battery box and anything else in the area. This would be much more likely to ignite any flammable atmosphere than a blowing fuse and would also produce a fairly flammable atmosphere in the process.

The battery box/compartment would not be classed as a hazardous area under ATEX/DSEAR as an explosive atmosphere is not expected to occur in quantities that require special precautions and the total volume within the box is also below that which would be deemed to be a risk so would be classd as non-hazardous.

If this battery box were to be classed as a hazardous area it would not be allowed to have the mains hook up in there either but it does, unlike the the LPG compartment on the front of the van which must not have any electrical equipment in it. (My van had a second mains hook up point connected in the LPG compartment which I promptly disconnected both for the explosion risk and as when connected to the mains the unused connection would have live exposed pins under the cover).

It is also common practice for cars to have fuses within the battery compartment and cars are no different under the regs so is almost every car sold in the UK non complaint also?

I believe I have a safe and legal setup here. If I find out different I will stand corrected and change my setup.

 

[WoodlandsCamper]

If this battery box were to be classed as a hazardous area it would not be allowed to have the mains hook up in there either but it does

My battery box has a dividing wall (with foam seal) between the battery side and the mains hookup side.

 

[ProfJohnL]

....

My oppinion is that this fuse is there to protect the length of cable from the battery terminal to the terminal block and nothing else. It is rated well above the total of all loads in the van and of the fuses supplying all the circuits within the van so will not blow due to any fault other than one on this cable or the terminal block itself. If it were fitted outside the battery box there would be 900mm un-fused cable and only 100mm fuse protected so pretty pointless and in all likelihood if a fault occurred the cable would go up in smoke burning through the battery, battery box and anything else in the area. ...

The purpose of a fuse is as you say to protect the wiring from excess current, but the position of the fuse in the circuit is not critical in the context of disconnecting the current, as a break in any part of a circuit will prevent current flow. However there are circumstancesespecially when dealing high voltages (>50V) where the position of the fuse is important in the context of ensuring exposed wiring is not at live potential.

In the context of your 12v system, there is no risk of electric shock with only a 12V potential, so fuses external to the battery box would be both effective and safe with the proviso that the activated fuse does not leave any loose wire exposed where any other metallic object could come into contact with it.

 

[Damian]

17th Edition.
A721.533.1.8
Overcurrent protective devices should not be fitted in a fuel storage compartment or fuel storage housing intended for the storage of Liquefied petroleum gas cylinders or in the compartment for housing an auxiliary battery.