Charging both batteries

[Rees]

Have you seen the MMM Expert Guide Supplement, Part 2 (included with the June issue of MMM)? Overall I am impressed by the quality of the descriptive writing which, in my humble opinion, greatly surpasses that in a certain well-known generic book on motor homes. On p 8 (col. 2) this new MMM guide states that the vehicle engine charges both the engine battery and the leisure battery (via a split charge relay) when the engine is running. Also, on p. 8 (col 3) there is the statement that transformer charger (taking the mains power from the hook-up) in motor homes ' is arranged to permit the charging of both the conversion's leisure battery and the vehicle battery'. This is not what I understand to be true of our Ford Herald Aragaon IV (1996). I have searched the manual for our van but can find no mention as specific as this. Have I misunderstood the meaning or does this not apply to my motorhome? Do I need to fit a split charger?? Do these cost much? :-(

[Derek Uzzell]

Rees: Assuming your Aragon's electrical system is still standard, the easiest way to arrange for both its leisure-battery AND vehicle-battery to be charged by the on-board charger when the vehicle is on 230V hook-up would be to fit a "Battery Master" device as marketed by Van Bitz. Alternatively, for a simpler, cheaper solution, you could use Clive Mott-Gotobed's 'bridging-fuse' idea that has been mentioned previously in MMM and on this forum. For technical accuracy, best to stick to John Wickersham's books I think and (for what it's worth) I personally loath the Batten Hill's chatty style (even when they get things right!)

[southwind]

[QUOTE]Rees - 2006-05-22 2:22 PM Do I need to fit a split charger?? Do these cost much? :-([/QUOTE] I haven't a clue about your MH - but many do not split charge. Simplest and cheapest method is to be found in Maplin stores. They do two - 1 charges at up to about 1 amp, and is about £5-7 and the other goes up to 5 amps and is under £9 I have used both, they are German made, work well and are installed in minutes (and forgotten) PS they also work with solar panels, and won't allow a flat battery to drain a good one.

[Derek Uzzell]

Southwind: Assuming Rees's Aragon motorhome's electrical system remains as it left the Herald factory, the vehicle and leisure batteries will be charged by the vehicle's alternator (while the engine is running) via the usual UK-norm split-charge relay arrangement. The 'domestic' 12V system will include a Zig-made X-Series battery-charger and Zig-made control panel. When on 230V hook-up the battery-charger can be employed to charge the leisure battery, but cannot be used to charge the vehicle battery. With this system in mind, how would one wire the Maplin's product so that the battery-charger also charges the vehicle battery please ?

[Clive]

Bridging fuse remains the simplest, lowest tech and easilly field repairable answer to this one!! C.

[southwind]

[QUOTE]Derek Uzzell - 2006-05-29 7:46 PM With this system in mind, how would one wire the Maplin's product so that the battery-charger also charges the vehicle battery please ?[/QUOTE] This is the most common motorhome / Rv setup. The Maplin charger feed connects to the coach or leisure battery, and ground, and the output connects to the chassis or 'engine' battery. You don't have to 'physically' connect to the actual batteries. As long as the unit 'bridges' the two systems it works. Mine is simply connected across the battery isolator relays which are common on American RVs. It's a one way system and uses in-built diodes to ensure it only works in the direction you connect it, so you don't finish up running your starter battery flat watching the footy or whatever, PLUS when the alternator / engine is running, there is no detrimental effect. The unit ONLY 'works' or takes power when the leisure system is better than say 13.5 volts, as when on mains or generator charge, so when no hook-up is available, it doesn't take power (even if your starter battery is flat!), it won't 'run down' the leisure battery. I first deployed this system after finding myself with flat leisures in an Aire in France which left me unable to start my generator. I had to buy a new battery from Leclerc, and 'jump start' the genny. I decided to install the battery as an auxilliary - after all what else could I do with it? The problem then was keeping it charged (it was tucked away in a locker 30 odd feet away from any regulated charging circuits). The Maplin gizmo fitted the bill, and still works to this day 3 years later! I have subsequently added two further 'aux' leisures (do a lot of wild camping!), and used the bigger 5amp controller to keep these in a 'state of readiness'. I did consider fuses and diodes, but after all this is the 21st century, and for a few quid it's a fit and forget feature :-D

[Derek Uzzell]

Thanks for the description - it sounds easy enough to do and certainly isn't expensive. I notice that the Italian company CBE markets a purpose-made product (CSB.2) that does much the same thing, passing an up to 4A charge from leisure to vehicle battery once the former has reached 13V. Not sure about its UK availability, but it's available in France for around 40 euros.

[Frank]

[QUOTE]southwind - 2006-05-28 3:46 PM Simplest and cheapest method is to be found in Maplin stores. They do two - 1 charges at up to about 1 amp, and is about £5-7 and the other goes up to 5 amps and is under £9 I have used both, they are German made, work well and are installed in minutes (and forgotten) PS they also work with solar panels, and won't allow a flat battery to drain a good one. [/QUOTE] I have been reading the thread with interest since I am about to buy a second coach battery which will be remotely located but will require charging, so thank you for the information. Have you any idea of the description or name that Maplins gave the system? Regards Frank

[southwind]

Hi - The bigger one is a solar - battery regulator and is made by Kemo of Germany, and their website is: http://www.kemo-electronic.com/en/module/m149/index.htm this is the link to the Maplin site you need (though they are obtainable at the large stores). http://www.maplin.co.uk/module.aspx?TabID=1&criteria=SOLAR%20PANEL%20battery&ModuleNo=37774&doy=30m5 The smaller one is a 12v battery regulator and the web link is: http://www.maplin.co.uk/Module.aspx?ModuleNo=37762&&source=14&doy=30m5 The price has gone up a bit since I bought one (still less than a tenner + VAT), and the smaller 1.5 amp one is £7.99 + vat these days. Both come with full instructions + wiring diagram. All very straightforward and I can recommend either, in fact the smaller one keeps the Genny aux. battery well charged, so for trickle charging most engine starter batteries should be more than adequate.

[southwind]

Found another which may be of interest, though I have no knowledge of it. It does come from the same stable as the others. http://www.maplin.co.uk/Module.aspx?TabID=1&DOY=30m5&ModuleNo=37767&criteria=

[Frank]

Hi Southwind Thank you very much for providing these links, I will follow each of them up. Regards Frank

[lesandy247]

Just picked up on this thread. Are we saying that MMM is wrong, and a hookup doesn't charge the engine battery? (?)

[patrickr]

Derek www.caktanks.co.uk import the CSB2. It is an excellent piece of kit, very simple to fit and inc postage is around the £23 mark. Pat

[Derek Uzzell]

lesandy247: Depends what you mean by "wrong". When on 230V hook-up my Hobby's system is said to charge automatically the leisure-battery as first priority, then the engine-battery once the leisure-battery has reached a particular state of charge. (Presumably it does this, but I haven't actually checked!) Some systems allow user-selection of which battery receives the on-hook-up charge, while others (as standard) aim the charge solely at the leisure-battery. I've no idea how many motorhomes have an on-hook-up charging system that only charges the leisure-battery as opposed to those with an automatic 'both batteries' or user-select 'one or other battery' system. But it's definitely not true that all motorhomes have an on-hook-up system where engine- and leisure-battery can both be charged via the motorhome's on-board charger. Happy with that explanation?

[chas]

hi- When we bought our new motorhome a year ago I was under the impression that the EHU charged both liesure and vehicle batterys, but as the van stood for a week or two over the winter period, the vehicle battery went flat, and on contacting the dealer informed us that it only charged the leisure battery, and only vans of a much higher spec charged both. He also said that I was not the only one to be caught out by this ommision. When you think of the tiny cost of fitting a split charger system it does seem to be spoiling the ship for a hapeth of tar. Luckly at this same time in MMM what should be advertised but the CSB2 from CAK tanks. Great piece of kit , took about 1 hour to fit, I do work slow, and have had no further problems, highly recommended. Chas

[Clive]

Up to recent years the standard hookup only charged the leisure battery. However of late several of the motorhome manufacturers have incorporated a range of different methods of using the hookup to charge both leisure and starter battery. One of the simplest was a relay that energised when the hookup was connected. This relay just linked the two batteries together (like my bridging fuse). Other systems give some priority to getting the leisure battery charged first. Its a changing world in motorhome electronics with micro computers getting so cheap. In the next few months you will see many of the features provided by the "add on" market incorporated into the standard controllers in new motorhomes. Watch this space! C.

[LeoK]

Would somebody please assist with technical enlightenment... I was taught that you should not charge a battery whilst it is still connected to the vehicle alternator, because to do so would wreck the alternator. I am prepared to believe that the above statement is true. I am also prepared to believe that there are few motorhomes with alternators which do not work. Hence, I reason, there must be a specific method by which the charge splitters (as from Maplin) are connected to the batteries such that the alternator comes to no harm. Could someone please post the theoretical and practical specifics ?

[Derek Uzzell]

"I was taught that you should not charge a battery whilst it is still connected to the vehicle alternator, because to do so would wreck the alternator." I don't know if this was ever true, though it's possible that the diodes and semi-conductors in early vehicle-alternators were particularly sensitive to 'battery in-situ' charging (and hence the warning). I checked what the Haynes manual for my 1995 VW Golf said about battery charging, but the only caveats related to jump-starting the vehicle and the correct charging regimens for different battery types. If providing an external charge to a connected battery always resulted in a wrecked alternator, then it would be impractical to emergency-start a vehicle via jump-leads or a power-pack. There's also a considerable incentive nowadays not to disconnect the battery, as so doing can knock out things like radio key-codes and may have an unpredictable effect on electronic management systems. Perhaps Clive M-G can give you fine detail on this.

[LeoK]

Thank you Derek. Best I now check out the volts and gravities (to establish just what might be already installed) ... then off to Maplin as recommended above.