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Battery Box or Not


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Hi all,

I am installing a couple of sealed unit batteries under one of the bench seats and the boxes are taking up more room than I would like.


I have investigated some battery hold down clamps and was just wondering what experience the collective experience would recommend.




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You need to be aware that all batteries produce gas and so must be fitted in areas with access holes to allow gas to escape downwards. There is often a small hole at the end and a hose is attached to this leading outside the vehicle. Although unlikely, there is also the possibility of acid leaks, and so a battery box does provide a container toi prevent this spreading. Actually the battery boxes available do not normally provide any actual clamping of the battery, merely a strap to hold the lid down. You can get tie down straps from caravan leiisure shops which would do the same thing. The other advantage of the battery box is that the terminals are covered so no chance of a short occurring.



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This link




is to images that include examples of leisure-battery installation in motorhomes.


and this webpage




has photos of a pair of batteries in an underseat locker.


I can’t see any persuasive argument for having to use battery-boxes, but you will need to prevent the batteries from moving about when your Calypso is being driven. If the batteries you’ve chosen are ventable - it would be sensible to fit vent-tubes to them.


How you tether the batteries will depend on the seat box and what you are prepared to do. My Rapido’s battery is in the rear garage: it just sits in a shallow tray screwed to the garage floor and there are a couple of straps fixed to the tray that stop the battery moving - much the same really how gas-bottles are often retained in a motorhome’s gas-locker.




It’s not obvious from the ‘deepred' link above what prevents the two batteries from moving horizontally, but it’s evident that the motorhome’s owner has built a wooden box to contain the batteries and that the box has a removable lid. (I’ve done something similar with my Rapido to protect the battery from being hit by things being carried in the garage.) in your case, if you took a similar approach, it would maximise the available storage space in the seat box and remove any possibility of stuff put in the seat box interfering with the batteries or vice versa.

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I too had an obscenely large battery box which only allowed one battery so I built a wooden enclosure in an under seat locker in such a way that the batteries could not move about but are still able to be easily lifted in and out as required and two small vent holes through the floor take care of the gas off tubes.
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Not all Batteries gas, if you have sealed units they should be just as safe when fitted without a battery box.

The plastic battery boxes I think you are using are actually more dangerous when a battery gases as it can concentrate the gas to explosive levels.


Some advice suggests that a battery fixing arrangement should be able to retain a battery from becoming a deadly missile in an accident. If the vehicle rolls, a 30kg lead weight might do a bit of damage. The Bed locker it is in will just flip open if the van rolls, unleashing the cargo.


However, we rarely see batteries fixed other than just to stop them sliding around and there are often just as many dangerous other things that could be put in the same category.

The risk of course is very small.


As mentioned earlier a typical plastic battery box often has little more than a strap which is usually held by a single screw through the 'belt' so any alternative fixing is unlikely to be any worse than you have now.


We would suggest that you at least have a tray to prevent Acid attacking the Floor.

Bar Beer Trays are quite good apparently. Stainless steel ones readily available if you Google search.

Don't drill and fix the tray to the floor, as the hole will provide a path for the acid to get below the tray, the type of straps/belts as used on a battery box are probably a good option.



It is important to ensure that the Motorhome Alternator, Charger and wiring will support the size of Battery Bank you plan on fitting.


A Renault/Devon, quality conversion, that we had in today had wiring from the Starter battery to the Leisure battery/Fridge that was only rated at around 30amps with a 30amp relay.

The second battery that had been added by the new owner, plus the original load, could have been higher than 40amps.

Probably a contributory reason why the Split charge relay had burnt out? We replaced it with a 70amp relay.


Don't assume that just because there is lots of guidance out there on fitting additional batteries, that any Motorhome will have the capability built in to the infrastructure.

Many don't.








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This MHFacts thread may be of interest




(Five leisure batteries - Wow!)


Rapido motorhomes and letting a battery-box into a motorhome’s floor are mentioned in the MHF discussion.


I recall (years ago when Rapido A-class motorhomes were only available in the UK in left-hand drive) seeing this arrangement at an outdoor leisure show. I said to the salesman that it seemed a sensible space-saving idea, but he warned of the need to be careful if replicating the arrangement.


He told me that an owner had DIYed a 2nd through-floor enclosure for a large supplementary leisure-battery but had not adequately reinforced the cut-out in the floor and the whole lot - battery and its surrounding box - had fallen on the road when the motorhome was being driven.


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