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Long Interval EHU Timer


StuartO

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I've been looking for a main supply timer switch (preferably plug-in)which will switch at intervals of several weeks, powering on for 24 hrs or so at a time.  I want to use it the plug the MH into an EHU at home when the MH is in storage.  No joy finding one so far - can anyone help please?

Sometimes it's a question of using the correct terminology when you are searching - what should I be searching for?
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No idea, but this is my alternative.

 

The EHU on my house wall is wired through an RCD. If I need it, I switch it on at the RCD and monitor the state of the batteries through the Bluetooth connection on my Victron BMV, then switch it off again when the BMV indicates that the batteries are full.

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There is an Omron H5s 365 day timer but it is getting on for £100 with shipping, etc. from the States.

Search for "OMRON H5S-YFB2-X ELECTRONIC TIMER, 365 DAYS 100 - 240 V AC Time Switch"

 

 

How about using a digital 7 day timer to drive an old fashioned 7 day motor drive/Analogue timer to get a longer time interval? Would that work?

 

 

 

 

 

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aandncaravan - 2018-11-14 3:59 PM

 

There is an Omron H5s 365 day timer but it is getting on for £100 with shipping, etc. from the States.

Search for "OMRON H5S-YFB2-X ELECTRONIC TIMER, 365 DAYS 100 - 240 V AC Time Switch"

 

 

How about using a digital 7 day timer to drive an old fashioned 7 day motor drive/Analogue timer to get a longer time interval? Would that work?

 

Or once a month, say on the first, switch the power on and then 24 hours later turn it off. Can't be that hard surely? And save your £100 for 'leccy bill :D

 

Keith.

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aandncaravan - 2018-11-14 3:59 PM

 

There is an Omron H5s 365 day timer but it is getting on for £100 with shipping, etc. from the States.

Search for "OMRON H5S-YFB2-X ELECTRONIC TIMER, 365 DAYS 100 - 240 V AC Time Switch"

 

 

How about using a digital 7 day timer to drive an old fashioned 7 day motor drive/Analogue timer to get a longer time interval? Would that work?

 

 

 

 

That is a novel idea Allan.

That should work but you probably need a 7 day timer that can be set on a daily basis rather than weekday/weekends.

If so, set the 7 day timer to switch on for 6 hours for just one day per week, and the 24 hour timer set to 6 hours each "day". The 24 hour timer will then advance 6 hours every week and so the combined effect would be 6 hours every 4 weeks.

This is not the same as 3 hours for 2 days as the charger will switch on twice every 4 weeks for 3 hours each.

 

The other way to do it if you have a home automation system is to use a "Smart plug" and program it accordingly. There are a couple of z-wave based systems that will do it easily.

 

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Our PVC is equipped with a CBE CB516 charger. The vehicle is normally left on permanent EHU, when not in use. I have yet to confirm any serious degradation of the batteries due to this practice. The starter battery wea retired at 11 years as a precaution, and is still giving service on our domestic standby battery bank.

 

In view of other opinions on this practice, I looked into the question of a timer about two years ago. The timer suggested by BruceM, or a similar unit, would have been my preffered solution, but the idea is on hold due to the fact that the timer switching ON would re-initiate the charger cycle, and perhaps exacerbate any problem.

 

Over the years we have owned several timers and heating programmers both electronic and mechanical. While the electronic versions can be more flexible with settings, and maintain there time settings over mains supply interruptions, there weak point can be the NiCd or NiMh back up battery. The result is that we have several functional mechanical timers, but perhaps no working electronic timers. I regard it as significant that when havng to replace heating timers after a power system surge, the updated versions used lithium coin cells for backup. Lithium cells have a shelf life of about 10 years.

 

I like Allan's suggestion of two timers in tandem.

 

Alan

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StuartO - 2018-11-14 12:48 PM
I've been looking for a main supply timer switch (preferably plug-in)which will switch at intervals of several weeks, powering on for 24 hrs or so at a time.  I want to use it the plug the MH into an EHU at home when the MH is in storage.  No joy finding one so far - can anyone help please?

Sometimes it's a question of using the correct terminology when you are searching - what should I be searching for?

HiWhen I go away without Moho l for extended periods I use a daily timer set for one hour per day. That has worked for me for periods up to 2+months.Peter
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peterjl - 2018-11-14 6:53 PM

 

Hi

 

When I go away without Moho l for extended periods I use a daily timer set for one hour per day. That has worked for me for periods up to 2+months.

 

Peter

 

Same here except 15 mins per day works for me.

I do the same with our cars when we're away for an extended period in the van: timer on for 15 mins/day -> regulated battery charger -> mosfet splitter -> both car batteries.

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Alanb - 2018-11-14 6:11 PM

 

Our PVC is equipped with a CBE CB516 charger. The vehicle is normally left on permanent EHU, when not in use. I have yet to confirm any serious degradation of the batteries due to this practice. The starter battery wea retired at 11 years as a precaution, and is still giving service on our domestic standby battery bank.

 

In view of other opinions on this practice, I looked into the question of a timer about two years ago.

 

Alan

 

Alan, As it says on our webpage "Long term EHU?", the CBE CB516 is one of the very fewy chargers that switch off totally when the battery is charged, making this relatively rare charger the exception.

 

Almost all other motorhome chargers we have seen, drop to a 13.8v continuous maintenance charge.

The Victron mains chargers also drop to a 13.8v maintenance/Float but are pretty much unique

in additionally having 'storage/long term' Float/maintenance charge profile that drops to a lower 13.2v if no change in the battery state is detected.

The Victron manual states -

 

"Once the battery is fully charged, power consumption reduces to less than a Watt, some five to ten times

better than the industry standard

The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours.

In the storage mode, float voltage is reduced to 13,2 V to minimise gassing and corrosion of the positive plates. Once a week the voltage is raised back to the absorption level to equalize the battery.

(This leads to ) Less maintenance and ageing when the battery is not in use".

 

 

 

So clearly Victron support what Yuasa say and believe there is an issue of ageing the battery by long term 13.8v Float charging.

 

 

 

The problem with a daily timer is that motorhome chargers don't work like most people think. The charger doesn't start up and switch down to a maintenance charge if the battery is full. Almost all motorhome/caravan chargers start up at full 14.4v 'boost' for a set timer period, often 4 hours, regardless of the battery being full.

Only after that 4 hours has expired do they drop down to a 13.8v Float/maintenance voltage and current.

 

So a daily charge of 60 mins will be a full 60 mins at full 14.4v, even if the battery is fully charged. Clearly that isn't ideal.

 

Worse still it will be at higher current. If you go back to the Victron statement above, it talks about it's chargers being more efficient than most, especially in storage 13.2v mode where almost zero current is allowed.

It states, " And once the battery is fully charged, power consumption reduces to less than a Watt, some five to ten times better than the industry standard".

 

To reiterate that, the industry standard chargers maintenance current is "... 5 to 10 times more current than a Victron charger".

 

That means the current, not just the 13.8v, is way more than is needed for a healthy battery.

You can therefore imagine how big that current will be at an even greater 'full Boost' 14.4v?

Probably more damaging to set a timer for 60 mins each day than a whole year at 13.8v?.

 

 

Most generic Solar chargers work in the same way using timers, some don't drop out of 14.2v ever. They are designed as chargers, not battery maintainers, with a premise that the 'National Grid' will always want max power.

 

We know of only the Votronic and Victrons that drop to a low 13.4v Float/maintenance setting when the battery is full, following modern thinking that 13.8v is too high for long term battery maintenance.

 

 

Based on what Victron say, I would suggest that even a weekly charge is too often, assuming the battery is healthy.

However, as it says on the web page, there are many relevant factors from temperature, battery technology, battery age, the charger, the standby draw on the batteries, the battery bank sizes, etc.

 

Something like a Banner Energy Bull that can self discharge quite deeply inside 1 month will obviously need, and want, to be charged more regularly than a Yuasa L36-EFB.

 

 

 

 

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aandncaravan - 2018-11-14 9:30 PM

 

Alanb - 2018-11-14 6:11 PM

 

Our PVC is equipped with a CBE CB516 charger. The vehicle is normally left on permanent EHU, when not in use. I have yet to confirm any serious degradation of the batteries due to this practice. The starter battery wea retired at 11 years as a precaution, and is still giving service on our domestic standby battery bank.

 

In view of other opinions on this practice, I looked into the question of a timer about two years ago.

 

Alan

 

Alan, As it says on our webpage "Long term EHU?", the CBE CB516 is one of the very fewy chargers that switch off totally when the battery is charged, making this relatively rare charger the exception.

 

Almost all other motorhome chargers we have seen, drop to a 13.8v continuous maintenance charge.

The Victron mains chargers also drop to a 13.8v maintenance/Float but are pretty much unique

in additionally having 'storage/long term' Float/maintenance charge profile that drops to a lower 13.2v if no change in the battery state is detected.

The Victron manual states -

 

"Once the battery is fully charged, power consumption reduces to less than a Watt, some five to ten times

better than the industry standard

The storage mode kicks in whenever the battery has not been subjected to discharge during 24 hours.

In the storage mode, float voltage is reduced to 13,2 V to minimise gassing and corrosion of the positive plates. Once a week the voltage is raised back to the absorption level to equalize the battery.

(This leads to ) Less maintenance and ageing when the battery is not in use".

 

....................................................

 

The problem with a daily timer is that motorhome chargers don't work like most people think. The charger doesn't start up and switch down to a maintenance charge if the battery is full. Almost all motorhome/caravan chargers start up at full 14.4v 'boost' for a set timer period, often 4 hours, regardless of the battery being full.

Only after that 4 hours has expired do they drop down to a 13.8v Float/maintenance voltage and current.

 

So a daily charge of 60 mins will be a full 60 mins at full 14.4v, even if the battery is fully charged. Clearly that isn't ideal.

 

..............................................

 

That means the current, not just the 13.8v, is way more than is needed for a healthy battery.

You can therefore imagine how big that current will be at an even greater 'full Boost' 14.4v?

Probably more damaging to set a timer for 60 mins each day than a whole year at 13.8v?.

 

.............................................

 

We know of only the Votronic and Victrons that drop to a low 13.4v Float/maintenance setting when the battery is full, following modern thinking that 13.8v is too high for long term battery maintenance.

 

.............................................

Based on what Victron say, I would suggest that even a weekly charge is too often, assuming the battery is healthy.

.............................................

 

 

 

Allan,

 

So you are agreeing that those of us fortunate enough to have either Victron or CBE chargers need not worry too much about long term EHU? Also you seem to be agreeing with my suggestion, that introducing even a weekly timer on systems where these chargers are fitted, could make matters worse.

 

Also I have noticed the repeated grammatical error in my original post. All please read "their" for "there" at the two appropriate places.

 

Alan

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"Allan, So you are agreeing that those of us fortunate enough to have either Victron or CBE chargers need not worry too much about long term EHU?

Alan".

 

 

No I am not agreeing. As I say on the web page, there are many factors that affect the outcome, the charger is just one aspect.

 

For example, the CB516 'goes to sleep' once the battery is 'fully charged', but then monitors the battery voltage looking for it dropping below 13.0v. Once the voltage drops below 13.0v the CB516 then restarts charging, beginning with a full power 'Boost' charge.

 

If you have a quality, modern battery, like the Varta LFD90, which has a SOC of 13.0v then the battery will take some time to drop below 13.0v so the charger will also take some time to 'restart'

 

But if you have an old fashioned, high self discharge, high Antimony, Banner Energy Bull battery, then the battery voltage will drop like a stone to under 13.0v in hours, maybe minutes, causing the charger to 'restart' in full power mode almost as soon as it 'switched off'.

 

 

Two very different scenarios, just because the battery is different.

 

 

To be honest I wouldn't use your 'fortunate' phrase to describe owners of a CB5XX that has anything but a quality, perfect battery because the way the charger works goes against the 'safety timer' principals adopted by most quality motorhome electronics manufacturers.

The manual states ;-

 

"The charging system is carried out in 4 stages:

1) with maximum current until the end-charge voltage is reached:

Note: the end-charge voltage is reached ONLY if the battery is efficient".

 

 

In other words it is charged in full 'boost' mode until the current being drawn by the battery drops below 1 amp. That is great for a good battery, but what about one that is tired and never stops drawing less than 2 amps?

Imagine such a battery/charger combination on long term EHU at 14+ volts and the fire/explosion/mess that then results? All when no-one is around to take action.

 

I personally think the CB5xx charger is one of the worst ever fitted in a UK motorhome. What other unit charges a wet battery at 14.1v/13.5v and a Gel battery at 14.3v/13.8v?

No sorry, I take that back, the Sargent 151 'Supercharge' fixed 13.5v, 10amp unit is the worst.

 

 

A 7 day timer with a low quality battery is probably better than a daily timer, but that depends on the charger, the battery, it's age, it's size, the temperature, etc, etc, etc..

 

 

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plwsm2000 - 2018-11-14 6:11 PM
aandncaravan - 2018-11-14 3:59 PMThere is an Omron H5s 365 day timer but it is getting on for £100 with shipping, etc. from the States. Search for "OMRON H5S-YFB2-X ELECTRONIC TIMER, 365 DAYS 100 - 240 V AC Time Switch"How about using a digital 7 day timer to drive an old fashioned 7 day motor drive/Analogue timer to get a longer time interval? Would that work?
That is a novel idea Allan.That should work but you probably need a 7 day timer that can be set on a daily basis rather than weekday/weekends.If so, set the 7 day timer to switch on for 6 hours for just one day per week, and the 24 hour timer set to 6 hours each "day". The 24 hour timer will then advance 6 hours every week and so the combined effect would be 6 hours every 4 weeks.This is not the same as 3 hours for 2 days as the charger will switch on twice every 4 weeks for 3 hours each.The other way to do it if you have a home automation system is to use a "Smart plug" and program it accordingly. There are a couple of z-wave based systems that will do it easily.


When I was younger I would have been able to get my head around this straight away but these days it takes a while and I sometime have to draw pictures for myself.  This time I managed to understand within two minutes and without having to write or draw anythng!

So my Chinese digital week-long timer is set for one spell of six hours every week and this one has to be in the wall socket all the time to power the digital timer.  I then set a mechanical 24 hour timer for six hours per day and piggy back it on to the digital timer.  The motorhome is plugged on to the mechanical timer.  The effect is that power only gets through to the MH once in every four cycles of the digital timer, for a six hour period, because on the other three occassions each month when the digital timer powers on the mechanical timer moves six hours further through its 18 hour power off phase.

You can only have a maximum of six hours of power if you want to restrict to one powered phase per four weeks.  If you set both timers for a twelve hour spell of power it will reach the motorhome every two weeks.

The question for Allan is therefore which is best for battery life - six hours every four weeks or twelve hours every two weeks?  I suppose it depends on charger and battery types.  In my case the charger is inside an EBL101 and the leisure bank is a pair of Varta LFD90s.
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Stuart, that is an excellent description.

 

Yes you are right, it depends on how big the battery bank is, the batteries, the charger and what parasitic 'leaks' you have as obviously something like an Alarm and Tracker will drop batteries very quickly, etc..

 

If the batteries are ultra efficient Varta, they won't self discharge, but Banner Energy Bull's self discharge quickly and can drop in a month, so the charging time needs to be adapted to suit. If the charger is a weak BCA 10amp 13.8v unit that takes forever to charge the batteries, then you may need a longer charge time, etc.

 

It will be unique to every motorhome, even two identical models may have different needs if the battery is slightly older, so the only way to do it is see what works for your vehicle.

 

In your case with new Varta LFD90's and a Schaudt 18amp charger you will probably get away with a few hours a month, so long as the Alarm isn't set and there isn't a Tracker, etc. Most will probably be better with 12 hours every 2 weeks.

 

 

Remember the parasitic load on the batteries from an Alarm, etc is key. If the batteries are genuinely being discharged by some usage, then they will need charging and because that charge is into a battery that 'needs' charge there will be little damage.

 

As it says on the web pages, this is about charging 'fully charged' batteries that are idle..

 

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With all this (often repeated) moither about long term hook-up and what certain inbuilt chargers can and can't do, and at what rate they do or don't charge etc...If a vehicle is being laid up for a while why not just disconnect the batteries from the "system" and just use a standalone CTek , monitoring type of charger?

..or are they now frowned upon as well? :-S

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pepe63 - 2018-11-15 11:22 AM

 

With all this (often repeated) moither about long term hook-up and what certain inbuilt chargers can and can't do, and at what rate they do or don't charge etc...If a vehicle is being laid up for a while why not just disconnect the batteries from the "system" and just use a standalone CTek , monitoring type of charger?

..or are they now frowned upon as well? :-S

 

 

A CTEK is a car battery charger designed for short term unattended charging.

 

The manual for the XS 7.0, one of the most common units recommended by the armchair 'experts', states :- "Don’t leave any battery during charging unattended for a longer period of time".

 

Have a look at the image below from the newer 10 amp model (full manual with better image at the bottom of this page : http://www.aandncaravanservices.co.uk/how-does-a-charger-work.php )

 

 

I will let you go through the various stages depicted in the image and work out what you think might happen with a tired battery that is losing a bit of voltage.or drawing a bit more charge current than a new battery?

 

 

 

1072824615_CTEKMXS10small.jpg.2b015c7fbfaacac098cee7ea504e468f.jpg

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