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How long should a vehicle stand?


Uncle Bulgaria

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I had a problem this winter with a flat starter battery whilst the motorhome was in its secure storage. The problem appears to have been a fault in a relay which has now been fixed. The starter battery was also not holding charge very well leading to its replacement. I am seeking advice on improving the ability of my motorhome to cope with storage for a number of weeks without access to an electrical hook-up. I've read extensively through various posts on the forum and various options are identified. I am now requesting guidance from forum members with far more expertise than I to help me determine how I address this problem.

 

When the starter battery was replaced the starter battery drain current was measured at 80 milliAmps in "storage mode". This figure suggests the drain will deplete roughly 50% of the 80 Ampere-Hour capacity over a 3-week period. So I need advice on what is the best way of recharging the starter battery and how could I extend the period in storage? There is no mains hook-up available at the storage site.

 

What seems certain is that bulk charging of the starter battery can only be done by driving the vehicle and letting the alternator do its work. So, how many hours of driving is needed top replace the 40 Ampere-Hours capacity lost over a 3-week period? Even after 3 weeks in storage, the voltage of the habitation battery is still around 13 Volts, which suggests it is still well charged.

 

I do periodically bring the motorhome home and connect it to the mains. The on-board charging system is based around the CBE 516 charger and associated distribution box and control panel. Besides charging the habitation battery this system automatically provides a trickle charge to the starter battery. The habitation battery gets priority for the charger output, but once the habitation battery is well charged part of the charge is directed to the starter battery up to a maximum of 2 Amps. I've monitored both the habitation and starter battery voltages and the charge to the starter battery floats some 1 Volt below the voltage of the habitation battery, dropping to 12.9 Volts as a minimum. If the trickle charge was a constant 2 Amps should 24 hours on hook-up replenish the starter battery? What I don't know is how the trickle charge current to the starter battery varies as the CBE charger implements the intelligent charging regime for the habitation battery.

 

My next hope is to extend the period the vehicle can be left standing without being periodically driven or on a hook-up. I know extended standing is bad practice, but it would be helpful if the winter lay-up period could be extended to more like 6 weeks.

 

Unfortunately, a solar panel is out as the storage is in a big barn, out of the weather and also the daylight. Connecting the positive terminals of the starter and habitation batteries through a fused cable (as regularly referenced on this forum) with the fuse removed other than when in storage, is a possibility. A Battery Master device, if viable, has the attraction of being a "fit-and-forget" device. My concern is, if a Battery Master is a permanent fitment, how will it affect the operation of the CBE charging system when the motorhome is on an electrical hook-up? The Battery Master would be working in parallel with the CBE trickle charge, but possibly with a higher output voltage than the CBE trickle charge as it is works on a voltage difference of 0.5 Volts, whereas the CBE trickle charge voltage is about 1 Volt below the habitation battery. Would it damage the CBE charging system? or would it limit the charge current to the starter battery to the 1.1 Amp limit of the Battery Master as opposed to the 2 Amp maximum of the CBE system? These questions are way beyond my ability to answer but I hope not so to the expert contributors to this forum.

 

I am most grateful to members patience in reading this post and even more so for contributions that help me address the various questions raised.

 

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My Hobby has a similar CBE-made system to your motorhome's and I'm reasonably familiar with it. However, I'm not going to attempt to answer your questions about charging-while-driving, or about the cbe-system's trickle-charging functionality.

 

This is because the simplest/cheapest solution to your storage problem is one you've already mentioned - use Clive Mott-Gotobed's 'bridging fuse' idea to temporarily parallel-connect the leisure-battery to the starter-battery during your motorhome's periods of storage.

 

http://www.motts.org/BRIDGING%20FUSE.htm

 

I don't know if a Battery Master (BM) would have any potentially damaging effect on your CBE system, or how a BM and the CBE system's charging regime might interact when battery-charging is taking place. But, if you do not fit a Battery Master, it's certain no harm can result.

 

Obviously, if you want to be able to leave the motorhome in storage as long as possible and still be (reasonably) sure that there's sufficient oomph left in the starter-battery to start the motor, (assuming you used the bridging-fuse ploy) you'll need to have starter- and leisure-batteries in tip-top condition and fully charged at the start of each storage period.

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Hi, just a pain in the backside solution, why not take the vehicle battery home with you when you know it willbe a lengthy storeage period, and put it on charge with a separate charger. This will have one possible advantage in that the thieves would not be able to start it and take it away..

the downside would be that any on board alarm would probably have to be run from leisure battery..

but in safe storeage this may be tolerable.

 

tony

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Tony

 

The starter-battery on a Transit Mk 7-based Hobby "Van" is located beneath the driver's seat. When a seat-swivel is fitted (as it will be on a Hobby "Van") removing or disconnecting the starter-battery initially involves unbolting the seat-swivel from the base beneath it and displacing the (heavy) driver's seat + swivel sufficiently to access the battery. Then some futher fiddly unbolting will be required to remove the metal 'clamp' used by Ford to hold the battery in place. And, of course, if the radio is 'security coded' (as it probably will be on Richard's "Van") it will be necessary to input the code when the battery is put back.

 

I did consider the option of fitting a battery isolator switch

 

http://www.electricalcarservices.com/Switches/Battery-Isolator-Switches/c-p-0-0-5-6.aspx?gclid=CMGkypCx5L0CFZShtAodD

 

to remove the small current-drain that's presently being placed on the starter-battery, but the radio would probably still need recoding and (as you point out) any alarm run from the starter-battery would either become inoperative or need to be powered from the leisure-battery.

 

If Richard's "Van" were being stored for several months without being started and with no battery-charging taking place, it would make sense to remove the starter- and leisure-battery and keep them on charge elsewhere, replacing them when the motorhome is brought back into service. But, with a combined starter-battery+leisure-battery Amp/hour total of (say) 160Ah to play with and just a small constant current drain, linking the two batteries via a 'bridging fuse' should allow engine starting to be practicable after a projected 6 weeks of motorhome 'idleness'.

 

Richard removes his motorhome from storage periodically, thus allowing the batteries to be recharged via his home's mains power-supply. As he explains, the vehicle's CBE-made electrical system only passes a 'trickle charge' to the starter-battery when the onboard battery-charger is operating. This means that the onboard battery-charger alone will not be able to fully recharge a well-discharged starter-battery. The options are either to recharge the starter-battery via the vehicle's alternator or use a separate battery-charger that can provide more than a 'maintenance' trickle charge.

 

My Hobby is stored at home and I use the latter technique, charging the leisure-battery occasionally via the onboard battery-charger, then switching off that charger and using a CTEK battery-charger to charge the starter-battery alone. In the same way that Richard is wary of the CBE system and a Battery Master charging in parallel, I'm wary of the CBE system and a separate battery-charger working together. That's why I'm careful not to have the onboard charger and CTEK charger operating simultaneously. (It might be OK - in fact it probably would be OK - but, as I can avoid any risk by carrying out the charging separately, that's what I do.)

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I'm grateful to Derek for his considered reply. For extending storage time (to more than 3 weeks) the Bridging Fuse solution from Clive Mott looks the clear way to go. I still need to bottom out the rate at which charge is put back into the starter battery as the vehicle is driven. Any further advice on this would be welcome - I guess this is not an easy calculation. The alternative is to follow Derek's practice and use a separate charger to recharge the starter battery on an overnight on the drive.

 

Thanks for the interest and contributions.

 

Richard.

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Guest pelmetman

Batteries are the first thing to suffer when in storage ;-)................especially with todays wagons having such complicated electrics :-S..............

 

But don't forget the rubber............As I can speak from experience of having what the MOT man said were square tyre's 8-).................I can also confirm that a full set of tyre's are more expensive than a battery :'(...........

 

So don't get complacent with your wiggly by pass :-|................If I've learn't anything after 20+ years with the same camper..............they're like women :-S..............and get grumpy when ignored :D.............

 

 

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The only real disadvantage of installing a battery isolator switch for the starter battery is the need to re-code the radio, and possibly some slightly erratic running of the engine when first re-started (but, as vehicles change all the time, it would be wise to get specific advice on leaving the vehicle for several weeks with the starter battery isolated).

 

The slight disadvantage of Clive's bridging fuse is that by allowing both batteries to be depleted, it increases the driving time, or time required on hook-up, to fully replenish them.

 

As the trickle charge given to the starter battery by the CBE charger is, as noted above, inadequate to charge it, hook-up will not be the solution for the starter battery however long the van is left connected. It is intended only as a "maintenance charge" that counters self-discharge, and system drain from the van. In short, to get the starter battery fully charged using this system, one's only option is to drive the van for some time. Like Derek, I can't say how long that might need to be, but storing the van with a partially discharged starter battery would be likely to shorten its life.

 

A further point to bear in mind is whether external factors (accident, illness, prolonged bad weather) might prevent the van being driven at the intended interval, leaving both batteries substantially more heavily depleted than expected.

 

On balance, given the circumstances, if one can face the slight tedium of re-coding the radio before it is next to be used, I think I'd go for the isolator as a first option. Simple, fairly foolproof, and relatively inexpensive, it also acts as a simple foil to theft - at least until the would-be thief finds the switch! :-)

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Brian Kirby - 2014-04-23 9:42 PM

 

The only real disadvantage of installing a battery isolator switch for the starter battery is the need to re-code the radio, and possibly some slightly erratic running of the engine when first re-started (but, as vehicles change all the time, it would be wise to get specific advice on leaving the vehicle for several weeks with the starter battery isolated).

 

 

Unfortunately, the insurance company says NO. Fitted security systems must be in use when the vehicle is unoccupied, and they are off the starter battery, of course.

 

I've been in touch with the MMM technical advice service and Clive Mott has given me good advice that my battery drain current is too high at 80 mA. I'm working with the dealer to identify the drain from each circuit to find where there might be a fault and to reduce the drain. This will extend the time the vehicle can be sensibly left in storage without causing deterioration of the tyres and other components. I think the solution may be to do as Derek does and use a separate quality charger to fully charge the starter battery at intervals.

 

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