ChrisD Posted June 14, 2017 Share Posted June 14, 2017 Good Afternoon I've recently purchased a new Roller team 746. It has a 130watt Solar panel fixed on the roof and a Varta LA90 AGM leisure battery. There was no manual for the charge controller and the dealer couldn't find one and neither could I online. Not happy so replaced it with a Votronic MP165. A few questions: this is my first AGM battery, what are the advantages over lead/acid for leisure use? Does it require maintenance? I'm no expert (far from it!) but I'm not happy with the wiring for the solar panel. There is no switch to disconnect the panel, should there be? The regulator is in an overhead cupboard but the battery is beneath a dinette seat. I assumed that they should be much closer. Finally I cannot find a fuse for the panel although there is one in the Votronic but what does that fuse protect? All ideas greatly appreciated Chris Link to comment Share on other sites More sharing options...
arthur49 Posted June 14, 2017 Share Posted June 14, 2017 Have a trawl through this website .... and Allan from aandn is on here regularly .... http://www.aandncaravanservices.co.uk/ Link to comment Share on other sites More sharing options...
aandncaravan Posted June 14, 2017 Share Posted June 14, 2017 A good choice buying the Votronic as at least one of your Charging devices will be optimised for an AGM battery. A while since I had a rant about AGM batteries, so here goes - AGM batteries have the Acid absorbed in a Mat, usually Glass fibre. Even if the case cracks, the Glass mat holds the Acid in place. Excellent for when you fly your Helicopter upside down, or do 'rollover self righting' on an RNLI Lifeboat, the acid just won't leak out. The Glass Matt may also be used as a Separator in the Battery Plate structure, often compressed, which helps to keep the Paste from detaching from the Plates, often resulting in a higher performing battery that will discharge/recharge with longer cycle life. However, just like on a conventional wet battery, the depth to which it can discharge and how many charge/discharge cycles it has, are dictated by the Plate construction. A thin, lightweight Plate construction AGM may perform more poorly than a thicker plate Wet battery. The Plate construction, and it's quality of construction are absolutely key in all Lead Acid batteries, but even more so in an AGM. In a conventional battery the Paste that detaches falls to the bottom of the Cell sometimes shorting the Cell so that stored electricity 'leaks away'. This is sometimes also battery life shortening phenomenon. Because of this construction AGM batteries tend not to fail 'short circuit' like conventional batteries and last longer than a old fashioned conventional battery. AGM batteries usually operate 'pressurised' as this helps the recombination of the Hydrogen and Oxygen Gas back into Water, which then returns to the Cells. This pressure is controlled by a valve, venting off excess pressure as required. While they are often referred to as 'Sealed batteries', technically they are not. A true sealed battery wouldn't vent it's excess pressure, it would literally be sealed tight. The correct description is Valve Regulated Lead Acid, where the valve will (or should) regulate the pressure inside the battery. Rapid charging or discharging at a higher rate than 20amps per 100Ah, especially at the temperatures of a Spanish summer, will not only cause the battery to gas, with a resultant increase in pressure and venting of that gas, but shorten the batteries life. AGM and Gel batteries do gas, but the rate at which they gas, is lower than an old fashioned battery but higher than a Powerframe technology battery. Under normal, as in when used EXACTLY as designed, circumstances the gas vented is low. However when used outside a very narrow window ( temperature and current) gassing can exceed that of a conventional wet battery, with potentially disastrous results. So if an AGM battery is used appropriately to it's construction and technical specification, it may have more discharge cycles. Compared to a like for like wet battery, an AGM battery may have around 80% greater cyclic capability. But then again it costs twice as much, so Dollar for Dollar, a comparable Wet battery setup will deliver more charge/discharge cycles for the same monetary outlay. It will be more cost effective to buy two quality wet acid batteries at £90 each, which will typically deliver 400 cycles (200 cycles x 2) compared to a typical, single £180 Banner AGM batteries 350 cycles. Or put another way, spending £180 on two quality wet batteries and linking them together as a single bank will create a much more powerful, longer llife and flexible arrangement than £180 spent on a typical single AGM. So the alleged primary 'plus points' are actually not that clear cut. Yet if you throw in the disadvantages of AGM when used in a Motorhome, they are significant. Because the acid in an AGM and Gel battery is 'locked' in place it is far less mobile than the acid in a wet battery. This renders them very susceptible to Plate damage from Heat. Victron state their exceptionally high quality and expensive AGM batteries will have their life dropped from 7 - 10 years to just 2 years if the battery is operated at a Plate temperature of just 40degrees. That is a temperature that doesn't even feel warm to the touch, let alone hot. They go on to write, "15. Charge current - The charge current should preferably not exceed 0,2 C (20 A for a 100 Ah battery) otherwise the temperature of a battery will increase by more than 10°C". If it is already being operated in a Spanish Summer and you use a 600watt Inverter to charge the Laptop, you won't even get 2 years life. Bear in mind these are exceptional quality batteries from one of the best Battery specialists in the World. How will an Asian budget 85Ah budget AGM fare? The very nature of the AGM construction makes it more difficult to build quality batteries in a consistent manner. An AGM battery is not automatically endowed with any qualities, it is the design and construction of the Plates that generates those characteristics. A poor quality thin plate AGM will be a bigger disaster than a poor quality wet battery, because when they do fail they can do so in a catastrophic way. An AGM battery is prone to thermal runaway : As the battery breaks down, it generates heat which promotes faster breakdown. This then generates additional heat so breaks down even faster still so generating more heat, and so on. As the battery breaks up internally so debris can block the Valve, sometimes leading to an explosion. This is not just like a wet battery splitting and spilling it's acid, this is pressure and heat build up that spontaneously ignites the highly explosive Hydrogen gas. God knows why so many people fit them under the Passenger seat. Maybe they have a desire to play at being James Bond with their very own Ejector Seat? Quality Wet batteries do not suffer from Heat damage in the same way, nor is the failure catastrophic when they do. The very mobile wet acid rises by convection as the battery is used. This draws in fresh, cool acid from below. Not only does the battery stay within temperature limits for longer but there is always 'Fresh Acid' at the Plates. In an AGM, as the battery is charged/discharged the immobile acid at the plates becomes exhausted and the chemical reaction slows down. If you run a big Inverter off an AGM, put on a current meter and watch the current drop after just a few minutes. Likewise rapid charging also exhausts the acid, to a lesser degree, so the initial fast charge can drop off quite rapidly. If Motorhomes used their electrical power like Caravans of the Eighties, they would survive better. But a modern Motorhome uses a lot more amps, and for longer, than many AGM Sales teams realise, yet this is where they pitch the product.. And I have not even mentioned they like a 14.8v charge to attain those alleged qualities!!! When AGM batteries don't have the 'real' extra charge/discharge cycles the Adverts claim (when a fair comparison is made) why put up with all the disadvantages? Please can I beg that no one buys the 'new' crop of budget AGM batteries, often with the Lucas/Numax label, in a 85Ah or 75Ah size. Not if you value your Motorhome charging systems. If you want to see the figures, charts and documents that back up the above or read more from a man who knows nothing about AGM batteries, then see : http://www.aandncaravanservices.co.uk/agm-batteries.php Link to comment Share on other sites More sharing options...
Charles Posted June 15, 2017 Share Posted June 15, 2017 Yes I'd put a 20 amp blade fuse in the solar panel positive wire. It will just serve as an isolator to disconnect the controller. Resite the controller to as close as possible to the battery. I've been told the fuse in the controller protects the battery circuit, which makes sense. Haven't been able to get my hands on mine yet, still in Spain. Itching to get home. I know, very sad :-D Link to comment Share on other sites More sharing options...
ChrisD Posted June 15, 2017 Author Share Posted June 15, 2017 Thanks Guys very helpful. Allan at least I know where to seat my mother in law. Seriously sounds like the best bet is to monitor the battery and replace it with a Varta powerframe when the time comes. Charles sensible advice. I had in fact considered a fuse in the panel live and instead of the actual blade fuse a 20 amp blade circuit breaker. Not sad mate this regulator gives hours of fun. Link to comment Share on other sites More sharing options...
aandncaravan Posted June 15, 2017 Share Posted June 15, 2017 An ejector seat for Mother In-laws, why didn't I think of that? Now an AGM battery in a Motorhome makes sense. :D Link to comment Share on other sites More sharing options...
ChrisD Posted June 15, 2017 Author Share Posted June 15, 2017 I hope to see this advice included in your website. As an original idea I gift this to humanity and all royalties go to your choice of charity Chris Link to comment Share on other sites More sharing options...
aandncaravan Posted June 15, 2017 Share Posted June 15, 2017 Chris, that's a deal. Link to comment Share on other sites More sharing options...
whiskers Posted June 16, 2017 Share Posted June 16, 2017 Perhaps you could tell Swift not to fit AGM batteries under the driving seat. Link to comment Share on other sites More sharing options...
aandncaravan Posted June 16, 2017 Share Posted June 16, 2017 I think the marketing machine behind AGM batteries is rolling along a bit too quickly for me to be able to climb on board. A bit like it was with Elecsol and Banner Wet 'maintenance free, best in the World' batteries. Link to comment Share on other sites More sharing options...
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