12v Batt-Bat Charger

[Guest Rees Pryce]

I have been reading about the Sirtling Battery-battery, invented by Charles Sterling, in the RoadPro catalogue(p24). Has any member experience of using this equipment? I am fitting a new ElecSol 100amph battery and wish to keep the battery in good order but £245 seems a lot to pay for this facility. I drive the van every two or three weeks throughout the year and I wish to keep the leisure battery (and the engine start battery) in good order. Is it easy to fit (as the RP catalogue suggests)? Can it be obtained more cheaply from elsewhere than RoadPro? Any comment -especially informed comments - will be much appreciated.

[Guest Derek Uzzell]

Some earlier forum correspondence about this product, Rees. Search on "sterling" to retrieve it.

[Guest Clive]

There are lots of benefits of leaving the charging system as the manufacturer intended. Don,t you think that if this alternative charging system were beneficial it would be incorporated as standard in all vehicle alternators? If it were it would not cause any cost increase. Buts it is not. Its a system that is more appropriate for charging milk float and fork lift truck batteries which are disconnected while charging as the voltage goes to well over 14 volts (per 12 volt battery) during certain phases of the charging cycle. "Traction" duty batteries have plumbing incorporated to facilitate the regular topping up with de-ionised water that will be required when batteries are repeatedly charged to 100%. Yes it will put a bit more (15 - 20%) in the batteries but if you are that short on capacity then you need to look carefully and ask why. Your existing vehicle alternator will look after your batteries in a safe manor with the minimum of maintenance and little risk of over-voltage damaging electronic components. But as Derek has said, its all been said before!

[Guest Bill]

I've looked at the Sterling website as suggested, and also re-read John Wickersham's article in Aug2003 MMM - and frankly I'm now more confused than I was when I started. Wickersham is firmly in the Sterling camp, but I also see Clive's point that "if this alternative charging system were beneficial it would be incorporated as standard in all vehicle alternators"

[Guest Clive]

Confusing isn,t it! I have spent 42 years in the battery electric fork lift industry as an electrical designer. (Retired January 2005) The techniques incorporated by Messers Sterling are not new and are widely used in the battery electric vehicle industry. There are DIN standards applicable to these regimes although I don,t have them to hand any more. But when the battery is your motive power you need to fully charge to ensure a days work out of the truck. Traction batteries are special deep cycle batteries for this type of application. Because they are deep cycled and fully (and frequently fast) charged they do consume a lot of de-ionised water. Maintenance is very important and to this end the main battery manufacturers offer bulk water topping up systems. The batteries are disconnected totally from the trucks when they are charged, frequently replaced with another charged battery while the removed one is in the charging bay. Hence there is no posibility of the high voltages applied to the batteries during certain phases of the charging cycle causing damage to electronic components. I believe a motorhome is a different environment for a battery than a fork lift truck. The position of leisure batteries is not always conducive to regular topping up, we the users are not well deciplined either. Plus the lesiure battery is frequently connected to equipment while it is being charged. Yes it wouod be so simple for the likes of Bosch, Lucas and the rest to produce alternators that used a fast full charge technique by simply changing the electronics within the regulator. But they dont. Ask yourself this question "how long does my starter battery last in my car". Well if you charge your leisure battery the same way and don,t over-discharge it it should last as long. The main detail frequently overlooked in the conventional "split charging" system is not having fat enough wiring for the charging current and not taking the feed direct from the alternator B+ terminal. (frequently its wired to the starter battery POS terminal and this puts the leisure battery at a disadvantage.) I waffle on! Its your choice and your money.

[Guest William R Dunstone]

Hi Rees, Some straight answers to your questions. Yes, I have experience of using the Sterling Battery to Battery charger - and it does what it says on the tin! It does have settings that can be changed for different types of battery and will keep them better charged if used regularly. You have to apply common sense in that if you stop too long you can flatten any number of batteries and if you don't move sufficiently frequently you will not recharge them. Sorry to state the obvious. What the B to B charger will do is put considerably more charge in than the normal alternator setup given a reasonable length of run. What it will not do, is significantly increase the storage capacity of your leisure battery. This is the question you need to ask yourself,have you got sufficient storage capacity? Can you park up for your normal time without external supply? I do not know of anywhere you can buy it cheaper. It is quite easy to fit assuming normal DIY skills and agility. I am a satisfied customer only. BillD

[Guest Clive]

And we have been motorcaravanning since 1972. All that time using the conventional split charging arrangement properly implemented with FAT cable and run from a standard alternator off the B+ terminal. Never had need to question its efficienty or its rate of charge! The only problem we ever had was when the regulator in one alternator went drasticly wrong resulting in boiling both starter and leisure batteries. The headlights were VERY bright when the throttle was blipped! That was our converted coach - Bedford Duple Vista 29 seater 14 years back. Its your choice and your money Good luck Clive

[Guest William R Dunstone]

I am glad that Clive has managed all these years without needing enhanced battery charging facilities. It is clear from the fact that Sterling developed and can sell this fairly expensive piece of kit to many people in the marine and other leisure users that others feel that the standard kit is not adequate. Perhaps it has something to do with leisure and bow thruster batteries, etc often being quite some distance away from the vehicle battery and there comes a limit to how bid cables one wants to run and even then there is some volt drop. BillD

[Guest Bill]

I guess what we are all really looking for is something that will supply a continuous 150 watts or so, regardless of whether it is overcast or dark, or no wind, and do it without making a helluva racket, like a petrol generator. That way the battery becomes merely a load smoothing device. I wondered about a (reverse) Peltier Effect generator, and thought about stripping the workings out of a cold box. Then I wondered if anybody else had had the same idea, did an Internet search and came up with a company in Canada which produces one, but it is very heavy and has a thermal efficiency of only 3%, which would imply both heavy gas consumption and a real problem with the heat-sink. Another possibility is Stirling engines, but the only ones available today are laboratory curiosities, which are too small – at a price which will make your eyes water. Back in Victorian times suitable Stirlings were made commercially, and I suppose it would be possible to “reverse-engineer” one of these and have a machine-shop make it up. But it would cost an arm and a leg, at least on a one-off basis.

[Guest Clive]

For a continuous 150 watts (well perhaps nearly continuous) you will need a fairly substancial wind generator. But in the current climate (we are all blowing rather well) perhaps its not such a bad idea. But WHY do you want 150 of continuous power, its supposed to me Roughing it smoothly I know but its still camping! Stirling engines are interesting, I also followed the same thought process and came to the same conclusion. I know, you need a FUEL CELL. That,s an arm and a leg cubed for that amount of power. Totally cover your roof with solar panels? You would need a sponsor! Good luck Clive

[Guest Mel E]

One word on the Elecsol batteries: do check their electrolyte level very frequently. In our last van I used Elecsol for a while and ordinary 'el-cheapo' batteries bought at a show. Never had a problem with the latter, but the Elecsol repeatedly gassed itself dry, even though all the charging (engine and solar panels) was properly controlled.