# B2b or a2b or additional alt?



## Noobie (Oct 9, 2010)

Hi peeps, want get a b2b or a2b, but after watching Charles sterlings YouTube vid about alternator curves, I am wondering if I should also look at changing pully size on alternator to get higher output at tick over, or even adding another alternator just for onsite tick over charging?

I tend to stay on sites with no hook up for a week or two at a time and am having to run my motor for an hour a day to keep the bats from dying on us.

Any advice? I was looking at the 120a b2b.

Ta

Steve


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## pieterv (Feb 3, 2009)

Make sure you have wet batteries and keep them topped up. B2B or A2B don't give much benefit with gel batteries, and charge at a voltage that has the battery gassing, so maintenance free batteries (where you can't top up the water) will be a problem. 

Modern alternators provide a higher voltage (14,4V) than in the old days, and consequently the benefit of B2Bs has reduced.


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## coppo (May 27, 2009)

I agree you would benefit from of these.


The split charge system on motorhomes is useless, on mine for instance from around 88%-90% remaining the split charge put in about 5amps and as the battery got fuller it trickled off to virtually nothing.


I have a ctek dual and that puts in about 10amps from 90%(its only a 20amp jobbie) but continues to put almost this is until the batteries are full.


The B2B Sterling will put in much more than this.


I think they are a great bit of kit the B2B chargers but you do need suitable batteries.


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## Noobie (Oct 9, 2010)

The bats supplied from new on my auto cruise Augusta 2007 are on their sides so I suspect they are gel, or agm but no good for fast charging at 120a! So new bats defo.

But if I have a b2b or a2b capable of delivering 120a, it won't get anywhere near that at tick over speed, probably 20-40 amps maybe? I don't want to have to leave the motor roaring away at 3000rpm to get that max 120a output, so the solution looks like fitting another alternator.

I have been wondering if one could fit another alternator with a high reduction ratio to get it spinning at high speed at tick over but then at higher speeds, for example if the motorhome is being driven somewhere, a clutch pully could disengage it to save over speeding the alternator and wearing it out.

Possible? Someone must have done this. Can it be done on. Pug boxer 3l motor?

Ta

Steve


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## coppo (May 27, 2009)

I would just fit new batteries and go for the 50amp B2B, it will make a massive difference, as the batteries get more charged you are not going to get 50amp in anyway, but it will charge them much quicker.


Paul.


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## nicholsong (May 26, 2009)

We have a Sterling B2B and it does enough to keep us charged when moving only for 15-30' every couple of days.

Your requirement for staying put, presumably without EHU sounds more difficult.

Have you got solar panels and how big? 

Maybe more solar panels rather than an extra alternator might be the answer?

Geoff


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## listerdiesel (Aug 3, 2012)

Solar would make more sense if you are stationary for any length of time.

The benefit is that they are working as long as there is sunlight and are silent.

A couple of 100W panels and a 25A or 30A controller would do the job and not too expensive.

Peter


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## Noobie (Oct 9, 2010)

Well I could probably fit 300w of solar to the roof, there is enough space. 100w panel of eBay for £85, makes you think! Dull day = maybe 90w for 7 hours. I do have halogen spots in there, first thing I suppose is to move over to LED spots. The main lights look like they are possibly fluorescents?
Food for thought! Looks like maybe a small b2b with some cheap solar with LED bulbs may be the answer.

Thanks peeps,

Steve


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## listerdiesel (Aug 3, 2012)

Converting flourescents to LED's is fairly simple, but you get out what you put in, so don't expect 1/10 of the current draw unless you are prepared to have dim lighting.

We've converted 20 or so tungsten and flourescent lights to LED using G4 fitting round light assemblies, here's a before and after:



















Here are the ones we converted for the kitchen in the [email protected]










This is the LED cluster that we standardised on for all of our conversions:










Peter


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## Noobie (Oct 9, 2010)

Thanks for that. Must pop out tomorrow and have a look at exactly what I have and how much juice I am pulling from them. 

So plan now is-
Replace all non led for LED lights
Fit solar panels, as much as I can fit on roof.(flexible ones look cool, and just glue them on!)
Fit new bats
Fit a decent bat monitor
Fit a b2b, but may actualy not need that now. Maybe wait until end of season, see how solar performs.

Ta

Steve


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## Noobie (Oct 9, 2010)

We use tv and free sat box on and off throuh the day, water pump, hot water heater, micro wave via 1000w inverter about 4-5 mins a day, lights at night, phone chargers x2. That's probably about it. Will 90w x 7 hours be enough?

300ah battery bank.

Ta

Steve


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## WildThingsKev (Dec 29, 2009)

I think your existing batteries will be fine with a 50A b2b charger. I have 2 x 110Ah Victron gel batteries and a Votronic 50A (45A output) b2b charger; Victron state that a charge rate up to 0.2C (ie 22A for a 110Ah battery) is ok and above that temperature compensation is required, which I have anyway. Check your battery manufacturers specs. Our gel batteries will accept the full 45A charge once their voltage is below about 12.2/12.3v (50%) but since they can be discharged to 20% without any undue loss of life expectancy this doesn't present a problem.

In practise we give it fairly hard use whilst skiing. We are just on the way back from 2 months in the alps where we had hookup for a total of 12 hours, moved on average every 5 days and only had to run the engine on tickover for an hour on about 5 occassions. Incidentally with a ducato 140A alternator it will happily put 50A into the b2b charger, top up the vehicle battery and run the fridge on tickover. (Remember to turn the fridge off if you want the veh batt to charge quickly). I tend to run the engine until thd charge rate drops to 30A then turn off. 

With my previous split charge and 2 100Ah banner wet batteries I never saw more than an initial 23A charge rate and it would generally be below 10/14A within 15 minutes. 

I also have an 80w panel, on this trip peak output would be 2.4A, the best clear blue skydays giving about 12Ah total. In extreme conditions I always pull the fuse the night before running the engine so that any morning solar top-up doesn't fool the b2b into thinking the batteries are at a higher state of charge than reality, they are automatically disconnected by a relay when the ignition is turned on anyway.

Kev


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## coppo (May 27, 2009)

If I was speccing a new van I wouldn't have solar just a B2B and 2 big 6v traction batteries, wet ones you can top up.


Solar great in summer when you don't need it, no heating to worry about which is the biggest user anyway.


In winter solar is useless in uk, a quick drive with the b2b and bingo.


We had 2 Rolls Surrette 6 volt and a sterling b2b on our last van, wonderful. Also had 280 watt of solar, great when you don't need the power, ie summer.


Paul.


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## WildThingsKev (Dec 29, 2009)

I agree, if I didnt already have the panel I wouldn't have added it after fitting the b2b. However we only use the van October to February these days.

ps. Last line of my previous post should read that "..... the solar panel is automatically disconnected from the batteries by a relay when the ignition is switched on anyway".


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## nicholsong (May 26, 2009)

Kev (W/things)

Your post above (no.12) is one of the most useful contributions to the many discussions about charging and battery performance that has been made, because it is based on actual usage, not theoretical calculations, and was in the worst conditions(low temps.) for battery performance.

Paul (Coppo)

We have Sterling B2B and have no problems - as you say quick run and batteries topped up.

I would like, and have looked for, large 6v traction batteries but cannot find any to fit my battery box - they all seem to be quite tall - do they have to be? or is it because of where they are located in golf-carts etc.?

Maybe if there were enough of us we could convince Peter(listerdiesel) to build a batch for us to smaller dimensions. 

Peter are you there? Come in Peter......

Geoff


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## coppo (May 27, 2009)

All the ones I have seen are tall as well Geoff.


I transferred the 6v ones over from our first van to our second, I have to alter the lid on the battery box in the first van so they would fit in.


No problems in second van as a really high outside battery locker.


I agree lower 6v ones would sell great in the MH sector.


Paul.


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## listerdiesel (Aug 3, 2012)

nicholsong said:


> Peter are you there? Come in Peter......
> Geoff


I is here Boss :grin2::grin2:

What is it that you need?

Peter


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## nicholsong (May 26, 2009)

listerdiesel said:


> I is here Boss :grin2::grin2:
> 
> What is it that you need?
> 
> Peter


Peter thank you for responding.

Please read the posts above and I will contact you in the morning with some more specifics, as I am about to bed (GMT +1)

Geoff


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## listerdiesel (Aug 3, 2012)

nicholsong said:


> Peter thank you for responding.
> 
> Please read the posts above and I will contact you in the morning with some more specifics, as I am about to bed (GMT +1)
> 
> Geoff


OK, no problem, sleep well.

Peter


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## listerdiesel (Aug 3, 2012)

For those of us who cannot use a B2B device, solar panels do give a useful amount of power, but like all things it is really down to how much power you use.

The trailer has four 80W panels split into two separate circuits, one for the habitation side and one for the engine winch and rear compartment lighting. We have these two circuits completely separated. Each circuit has a 26A charger attached.

That worked very well and the trailer is still with us, we went up to it today.

The Mercedes has 24V vehicle electrics, so again we can't use a conventional B2B device, and instead we have four 100W panels split again into two circuits, with 225AH AGM batteries on both, with 50A chargers on each.

This will cover the extra electrics we will be using, such as LPG solenoid valves and other safety bits and pieces.

Peter


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## pieterv (Feb 3, 2009)

Since a gel battery doesn't take a voltage of higher than 14.4V, which you will get from your alternator, I fail to see where the benefit of a B2B lies. I suspect that the improvement seen might well be that it compensates for the voltage drop in the (often too thin) wiring installed by the motorhome manufacturer. Upgrading the wiring might have a very similar effect.

Real benefit will be seen by using wet batteries where you can utilise the higher voltage the B2B can provide. It is generally accepted that gel and B2B are not an ideal combination. Sterling's own website states this very thing (or at least used to).


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## listerdiesel (Aug 3, 2012)

Most VRLA Lead-Acid batteries operate gas recombination at the plates, so unless you go to extremes with charging voltages and currents, AGM or GEL batteries will withstand 14.40V and higher.

Car alternators are machine sensed, so whatever voltage you may get at the output terminal is normally dropped by half a volt by the time it gets to the battery, and a bit more by the time it has gone through the B2B unit.

My trailer solar panels are running the batteries at 14.20V at the controller and 13.90V at the batteries.

Peter


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## WildThingsKev (Dec 29, 2009)

14.4v may well be the max voltage at 20C, (I have seen up to14.55v when the batteries are cold as the b2b has voltage sensing and temperature sensing wires) but the b2b charger will still put in a continuous 45A if it needs to which the original split charge system would get nowhere near. I agree that bigger wiring would improve ANY split charge system but the existence of a charged starter battery in the circuit will always restrict a continuous high charging current, the b2b effectively annuls the starter battery. (I should clarify that my split charging system is disconnected from the batteries along with the solar panel by the ignition operated relay, it still powers the habitation whilst driving).

The b2b also provides a full 3 stage charging profile set to be optimised for gel batteries which heavy wiring on a split charge system simply would not do. Where a gel battery is not so good for fast charging is only in the last 20% which takes a long time but I would make two points about this. First, that few vans touring around with any system are likely to get there batteries much over 80% anyway, especially in winter. Second, and this is why I have gel batteries, so I have a wide range of usable Ah between 20% and 80% which can be recharged at high current; with the cheap wet batteries Charles Sterling recommends I would only have a range of 50% to 80% plus quicker, but still relatively slow, up to 100%. I must admit that I don't understand Sterlings argument, there are a huge number of contrary articles elsewhere; plus I now have the evidence of my own experience as Geoff kindly pointed out.

Last week on a skiing aire there were people with new batteries running generators several hours a day and still losing power after fully depleting their batteries.

Kev


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## WildThingsKev (Dec 29, 2009)

Correction to last post para 2.

First, that few vans touring around with any system are UNlikely to get there batteries much over 80% anyway, especially in winter.


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## pieterv (Feb 3, 2009)

WildThingsKev said:


> this is why I have gel batteries, so I have a wide range of usable Ah between 20% and 80% which can be recharged at high current;
> 
> Kev


Kev, thanks for sharing your experience. I would be interested to know what gel batteries you have. With mine a discharge to 20% would severely limit their life. Mind you, they are a few years old, so technology might have progressed. Would be interested to have a look at the spec sheet for yours.

Thanks.

Pieter


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## coppo (May 27, 2009)

I think Kev has mentioned a few times on facts he has Victron gel batteries.


Paul.


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## WildThingsKev (Dec 29, 2009)

Paul is correct, Victron gel batteries. Datasheet attached which shows life expectancy of 500 discharges down to 80% depth of discharge, ie 20% left. I think it is also 200 complete discharges.

Incidentally I checked my Votronic b2b manual and it only charges wet batteries to 14.4v in the absorption phase, same as a gel battery, so not 14.7v like the Sterling unit. Also, this is only reached after the bulk charging phase during which the maximum current is going in and the voltage is steadily increasing.

Kev


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## pieterv (Feb 3, 2009)

Great, thanks for that.


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