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Solar Switch


trialsrider

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Ive been reading on here about the dangers of my solar panel over charging and damaging my leisure battery. Could I simply fit a simple on off switch before it goes to the charge controller (most accessible point) to act as an isolator in the circuit enabling me to turn solar on and off and prevent further charging ? My set up is a 100 watt panel charging a 110amp leisure battery via charge controller. Our van literally bakes in the sun on our drive in the summer as it's in a sun trap. I thought I could switch the charge controller on and off and do this but I don't think I can. If a switch would work could people suggest a suitable switch. Thanks.
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HI,

I don`t see the point of fitting an on/off switch. The solar charge controller if programmed correctly should monitor and take care of the batteries charge state and prevent over charging. Besides if you fitted an on/off switch in the positive line from the solar panel it would indeed cut power, but you would still need to manually monitor (operate) this switch to which the charge controller does anyway. (?) As regards a suitable switch if used I would recommend at least a 30amp rated.

 

 

Steve

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You may wish to consider using a 20A maxi blade fuse. This would provide visible isolation, and you could place the removed fuse link in some clearly visible place as a reminder

 

I have no first hand experience, but solar overcharging is frequently mentioned on ths forum.

 

Alan

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A switch suitable for 12v dc current will be easier than a fuse to isolate the panel. Fuses are not needed on solar panel feeds as a solar panel is limited in its current output.

Suitable switches, fit in the positive cable between the panel and controller,

https://www.12voltplanet.co.uk/1-way-rocker-switches.html

https://www.12voltplanet.co.uk/1-way-toggle-switches.html

 

Mike

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sshortcircuit - 2018-11-09 7:43 PM

 

Little point in having a controller if you are going to isolate. Mine is connected permanently and never had any problems even the months in Spain. If you can find a link to one of these stories it would be interesting reading.

 

Shortcircuit,

 

You mention months in Spain, when you would be using your habitation battery. The OP was referring to a vehicle parked on his drive, and preumably not in use.

 

Alan

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Alanb - 2018-11-09 9:37 PM

 

sshortcircuit - 2018-11-09 7:43 PM

 

Little point in having a controller if you are going to isolate. Mine is connected permanently and never had any problems even the months in Spain. If you can find a link to one of these stories it would be interesting reading.

 

Shortcircuit,

 

You mention months in Spain, when you would be using your habitation battery. The OP was referring to a vehicle parked on his drive, and preumably not in use.

 

Alan

 

So? What is the purpose of the controller?

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Thanks for all your posts. As someone pointed out my problem is when the van is on the drive in the summer months. I've seen the voltage panel display 14.4v. That must be a harmful level ?

 

When we are away in the van it's not an issue as I want all the solar charge I can get with a compressor fridge, 12v telly and lighting etc. We never use hook up and go to some pretty basic sites.

 

The switch I need ideally would be surface mounted not flush fitted as all my solar cables are not hidden as they come through the roof into a cupboard.

 

Thanks

 

Gareth

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Have a read at the controller instructions, my controller has an absorption charge of 14.4v then will drop to 13.7v float when the battery is full.  Once a month it goes up to 14.9v for 3hs to equalise the cells.

Any excess voltage will be lost in the controller heatsink and why it should be fitted horizontally in a well ventilated place and in the same ambient temperature as the battery.

I have a fuse to disconnect rather than a switch as it was more convenient at the time of fitting, I was going to fit one in the cupboard where the wiring came in as joint box but the mrs said it would get knocked and turned off when she put things away.

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The concern is that the solar controller will start up each morning and apply its main charge even if there was no significant drain on the battery overnight (the battery may still be fully charged).

If the van is not in use, the theory is that this can eventually overcharge the battery.

 

The solar controller cannot tell the battery's state of charge since it doesn't monitor the battery current directly. The solar controller only knows how much current is being drawn from it (and its output voltage of course) but it doesn't know where this current goes. Any other consumers (TV, lights etc.) will add to the overall current draw. The battery voltage used to indicate state of charge is only meaningful when there has been no load on the battery for a couple of hours.

 

The need for a switch on the solar panel output is questionable over the winter period, as there is not much solar energy about. It is probably only useful if layed up during sunny periods.

 

I have an inline blade fuse on my system but rarely use it. On my Votronic duo mppt, I added a switch to the temperature sensor input to switch in a resistor that lowers the output of the solar controller if I am not going to be using the van for awhile.

 

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Is this really a problem, or just a perceived problem ?

 

My Roller Team had a 100w panel (OEM fit) and fairly basic PWM controller connected to a 100Ah No Name "Leisure" battery. I added a CSB2 unit to divert excees charge to the van battery when the habitation battery was charged. The van sat on a south facing drive in West Yorks for 310 (or so) days a year.

 

The No Name leisure battery was starting to show signs of reduced capacity at 4 years old when I sold that van - the cab battery stlll appeared OK. Had I kept the van I was planning to replace the habitation battery for the next year, but don't feel that being permenantly connected to the solar had reduced the battery life.

 

Nigel B

 

 

 

 

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The point as I understand it is that most, if not all solar controllers start a new charge cycle each day after hibernating overnight due to lack of sunlight. Their charging algorithms force a full charge for a specific period at each new charge cycle, irrespective of the battery condition. For Votronic chargers, which are pretty well regarded amongst the various makes, this full charge can be anywhere between 30 minutes and 6 hours of every day, depending on the type of battery charging program selected.

 

Whether this is a real issue or not, I don't know, but I suspect any likelihood of problems would rise in proportion to the solar capacity available.

 

Certainly, my experience of smart mains chargers over many years (which do not exhibit this daily full charge behaviour, but are supposedly capable of being left connected on a permanent maintenance charge) is that they do have a detrimental effect on battery life if left connected for extended periods despite the manufacturers' claims. I base this on my experience with a classic car and also a fleet of motorcycles that were left connected to intelligent chargers whenever they weren't in use. Battery life was poor in each case, but improved markedly after changing to a routine of a single monthly charge with the batteries left disconnected in the interim. The life of my quality classic car batteries actually doubled after changing to the latter routine.

 

Having said that, I don't disconnect or restrict the solar controller on my motorhome, but nor would I leave it connected to its mains charger for extended periods either.

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mgnbuk - 2018-11-10 12:27 PM

 

Is this really a problem, or just a perceived problem ?

 

 

 

 

Yuasa say on their web site, "Continuous charging, even from a well-controlled charging system, will result in internal degradation of the battery. This could result in the battery not giving its predicted output when required even though the battery appears to be fully-charged)".

 

Victron Energy, the most expert battery and battery charger manufacturer in the world, state - That a battery is ok on Float/maintenance/trickle charge of 13.8v for days, even weeks, but not months.

 

 

Banner go one further and say, " In order to obtain the maximum service life from your battery, please ensure complete separation from the on-board supply (charger) when the vehicle is not in use for more than 7 days".

 

 

Roadpro say - "'...... with a solar panel, a battery to battery charger or a mains charger that's on for days at a time, the electrolyte levels of Energy Bull batteries must be checked on a regular basis".

Normally, excessive fluid loss is a sign of overcharge.

 

Clearly these Energy Bull batteries are losing more than normal fluid when on Solar or long term mains charging, strong evidence that long term charging from Solar/EHU affects batteries.

 

 

 

 

The best motorhome specific Solar regulators Float charge at 13.4v, not 13.8v. Clearly 13.4v is going to create far fewer issues than 13.8v, or even the 14.4v of some Solar regulators.

However, both Banner and Yuasa say long term charging at any voltage is clearly not ideal.

 

 

 

Those are the experts views, take them or leave them.

 

 

Obviously the above is only a risk for fully efficient Solar solutions, many are so poor that they struggle to get 13.3v into the batteries. Obviously these won't put out enough charge to cause any degradation.

 

Just like the 2003 Hymer of Mr Row's I saw on Saturday that had a really crude Solar rgulator ( the one used by Sargent, see here : https://sargentltd.co.uk/shop/product/dual_solar_regulator/125) and that wasn't raising the batteries above 13.5v max despite full Sun at 12:45..

 

Everything about the install went against the rule book, A poor none MPPT Regulator installed up near the ceiling, 4 metres away from the EBL 101 using thin cable, etc.

 

 

 

 

 

 

 

 

 

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Emergency lighting, fire alarms, burglar alarms all use batteries permanently connected to a charger as do UPS units for computer backup, operating theatre supplies etc. Is there something special about MH batteries?

 

With respect to the OP, I would doubt if any controller would allow overcharging. They all look for voltages, whatever the time of day and adjust accordingly.

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sshortcircuit - 2018-11-11 8:24 PM

 

Emergency lighting, fire alarms, burglar alarms all use batteries permanently connected to a charger as do UPS units for computer backup, operating theatre supplies etc. Is there something special about MH batteries?

 

With respect to the OP, I would doubt if any controller would allow overcharging. They all look for voltages, whatever the time of day and adjust accordingly.

 

 

Nothing special about Motorhome batteries, but there is about UPS units for computer backup, operating theatre supplies etc.

Firstly they are very, very expensive, 10 - 15 year life batteries.

 

Secondly they are long term 'trickle' charged at 13.2v, as per the manufacturers guidelines, not the 13.8v of a motorhome mains charger or good Solar.

 

Thirdly, they are usually in air conditioned rooms where the cold temperature ensures they can better handle permanent charging.

 

Temperature is a key factor in overcharging, hence the original OP wanting to protect his batteries during summer months, 'in his Sun Trap'..

 

 

If you look at this thread https://www.swift-talk.co.uk/swift/forum/new_posts/267084/leisure-battery-alert, it not only documents problems with Solar regulators over charging (a known issue with the Sargent 'generic' unit), but, conversely, also contains text documenting a poor PWM installation that struggles to reach even 13.4v. It states :-

 

"Many thanks all for your continued help, We have bright autumn sunshine here and the panel is charging 'solar to leisure' at 0.4a and a voltage of 13.4v".

 

Note that 13.4v is to a battery that has been run down to 11v by the Heating and should be charging 'flat out', so 13.4v certainly won't overcharge, it probably won't charge it hardly at all, hence his original issue?

 

 

Your faith that Solar chargers do what the advertiser claims is endearing, However almost all those currently on the market, are aimed at House Solar systems. We know of only 3 motorhome specific Solar regulators out of the hundreds available.

 

 

House Solar Regulators might seem to have the same functionality as a motorhome, but it is subtly different. The difference is only small but the outcome for the batteries very different.

 

House Solar is based on the premise that the House owner will want to throw absolutely every amp harvested at the Batteries/Grid, for obvious reasons.

Whereas, most motorhomes/caravans are idle for 3/4 of the year so will have full batteries and not want even a milliamp put into the battery.

 

Therefore a Solar Regulator that wakes up each day 'in flat out 14.7v' mode, might be perfect for a house, but is going to kill a Leisure battery that is already full.

 

For example one Solar Regulator we encountered 'wakes up' each day when the Sun rises and then goes straight into a 'fast charge' 14.7v for a fixed time of 2 hours, even if the wet acid battery is already fully charged.

 

It will only drop to a 13.8v 'trickle' charge once the 2 hour timer expires. That will happen 365 days a year. And yes the quote of 14.7v for a wet acid battery is as per it's spec, not the usual 14.4v, so this again will have an 'overcharge' impact.

That will seriously shorten any batteries life if the Solar isn't managed by shutting it off manually.

 

 

If you think buying from a big Solar specialist will protect you, then have a look at this -

http://www.photonicuniverse.com/upload/file/Manuals/PTRxx10A/PTR1210A/PTRTracerA__user_manual.

pdf

 

The Photonic universe Tracer regulator is the one we speak of above that charges at a battery gassing 14.7v!!!!

 

 

It is far from the only unit, we estimate that probably 90% of motorhome owners have an 'inappropriate' Solar solution.

That is why we put so much effort into our Solar web pages to help people correct the issues themselves.

http://www.aandncaravanservices.co.uk/solar-power.php

 

And the web page on charging longterm ;-

http://www.aandncaravanservices.co.uk/ehu-full-time-yes-or-no.php

 

 

 

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My experience with UPS units: they sit there, do nothing and when you need them the battery is dead :-D

 

Allan posted a nice document on his site from a study of large battery installations (UPS and such). Lets say modes of failure and battery lifetime figures are eye opening in many ways. I know of no solar regulator that would default to skipping bulk and absorption phases each day. Some know to keep them short if the battery is already full from previous days, but they still bump the voltage up initially. Which, as many documents and studies say, is unnecessary or even harmful to the battery over the long run.

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