That is a fact, but if I were to do it i would upgrade the charging wiring,, not a difficult job on my van, that alone will increase the input
Nice to meet you, 1960 to 74 . . . . . . . . . . .
It will, but if you’re going to that trouble, you may as well stick a B2B in while you are there.
Bit confused by that, surely the 30amp is coming from the alternator or it would soon flatten the cab battery if the engine is not running. Do not understand why you think you are still getting the original 7amps, of course it is possible you are putting 37amps into your cab battery then spilling 30amps into your leisure battery. But that is not 30 plus 7 into your leisure battery.
The point is, he wired direct all the way from the starter battery to the B2B with new thick wires, rather than utilising the existing wires from the starter battery which were too thin. The B2B only fires up when the engine is running and the alternator is supplying power, so the alternator is always charging the starter battery and feeding the B2B, no power drains out of the starter battery to the leisure battery.
The question stems from a 3 week trip, no EHU, the first 2 weeks the sun shone so the solar kept the btys topped up, the final week no sun so btys very low, it took over 200 miles driving to fully charge them. Which made me think about B2B. If went down this road i would fit 30A charger as i doubt my alternator puts out much more
You are of course right, I was trying to use a simple analogy. Of course current will always flow from the highest voltage source, a running alternator. Where it goes depends upon the resistance of anything it is connected to. If the cab battery is fully charged the current will then flow to the leisure battery - from the alternator. In the same way if the cab battery is at a lower state it will receive the current. A decently wired split charge relay system, connected to an appropriately sized alternator, will be able to supply all the current required. The main advantage the B2B has is the ability to control the charge to the leisure battery with a proper Bulk, Absorption,Float regime which the alternator cannot. Typically a conventional vehicle alternator outputs around 14.4volts, to fully charge the leisure battery would require around 14.8volts. (assuming lead acid). Neither are good for a fully charged leisure battery which should float around 13.5 volts. The B2B can achieve this.
Morning ''Jack''There's only two types of marine. Royal Marine and Submarine. And they both go down on submariners
My Battery monitor tells me that when the engine first starts 20A are being delivered to 2 batterys, this drops off as the batteries charge, which is what you would expect. The way we use the van has changed as i get older, we used to stay a few days and move on, but we now tend to stay in one place for longer periods, some times we use EHU many times we don't and rely on solar to top up the batteries, if the sun shines that fine, if not we have a problem,as was the case last summer. It took 200 miles of driving before the batteries were up to 85%, which promted me to think about B2B. I think I will do as you suggestand beef up the wiring and the relays and see what effect that has and go from there. Thanks for your input
You must be coming to the end of your time. Interesting times to have served. Civvy street must be a dauntng prospect, Took me 3 years to settle. Good luck
I can see how you could beef up the wiring, but I think you'll find it's more difficult to uprate the split charge relay. I'd guess it's built into the fusebox, probably soldered onto the PCB. I suppose you could just add another relay, wiring direct to the batteries.The two relays would work together, and you wouldn't have to disable the existing relay like you need to do for a B2B.
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Agreed. Older Brit m/h's do seem to have weedy wiring.
Yep & I've only got 3 x 78ah Gels & 300 watts of solar, only time we have nearly run out of power was 14 days in one spot in Germany in October (I was stuck in hospital for a week, the boss had to be careful with power).
My van is as old as god's dog, the relays are under the bonnet next to the starter battery, so updating them is not a problem, In fact I have them ready to fit, when it warms up It's my first job along with beefing up the cables, something I was going to do last year but ran out of nice days. I had seen a lot of posts relating to the virtues of B2B and wondered if it would benifit me while I was upgrading the wiring
You happy doing that ????. I guess it depends on what job you get. Think I would get cabin fever. Enjoy
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