Would a B to B charger be the answer; if so what size?

[Rocking Rivet]

We, SHMBO and I, like to get to an area of the country - UK or European- then spend a couple of nights in a place and move on (normally only 30-50 miles at a time). We stay mostly on CLs & CSs in the UK and Aires when abroad, most of which don’t have hook ups.

We have a 2018 Euro 6 Peugeot Autosleeper Nuevo, with a Sargent EC328E power supply, which has an intelligent 300-watt (~25A) battery charger and power supply, which incorporates a 3-stage intelligent charge routine. A built-in solar panel regulator for the direct connection of up to a 100-watt solar panel provides the simultaneous charging of both the leisure and vehicle batteries. There is 80-watt solar panel on the roof. It’s all connected via a Sargent EM50 to the original motor electrics.



I am thinking of buying a CTEK D250SE 12V 20AMp Dual Battery- to- Battery Charger as it seems to be able to charge any type of batteries up to 260ah and I only have 100ah wet lead acid battery at the moment, but at some stage will upgrade this to. It also has a connection for solar/wind power, as I would like to have a larger solar panel.



Is this best option or should I buy 2 separate units, one to charge the batteries from the alternator and one to charge the batteries using solar power.

Would I be half way to there for a lithium battery replacement?

What size cables should I use?

What is the maximum size of solar panel I could fit?

 

[LesW]

It all depends on how much 12v you use, and what on.

 

[Rocking Rivet]

We use lights when dark and radio for a 4-5hrs a day. Plus we charge up phones and iPad, we use the fan on the blow air heating if cold and just blown air if really hot also a usb type fan all night again if its really hot.

 

[DBK]

For a 100Ah battery a 20A B2B would be fine. I haven't come across that particular unit but it seems quite clever.

The problem is if you are going to add more solar in the future and change to lithium, which can take a higher charging rate I seem to recall, the unit may not meet your needs.

However, you can always run another solar panel off a separate controller if the CTEK can't cope.

 

[pappajohn]

The built in solar regulator is limited to 100watts so to go any bigger will need a "stand alone" regulator suitable for whatever panel you fit.

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[Lenny HB]

If only driving 30 to 50 miles a day I would fit a 45 amp B2B.

As John says to fit more solar need to bypass the Sargent unit it, its a cheap and nasty regulator anyway. I would fit at least another 100watts.

Cable size depends on length of the cable run, you want to aim for less than 3% volt drop.

 

[nicholsong]

Rocking Rivet

I think the basis of the answer to your questions is in your travel style

'Moving every couple of days.....30-50 miles driving'

That is identical to our touring. We fitted a Sterling B2B(Victron maybe better now), wired directly to the leisure batteries. We do have an 80w solar.

Since we fitted the B2B we have never had to think about batteries(2x90Ah lead acid)

Put in whatever other smart kit you like, but why not try our set-up and keep the other money in your pocket for later if you feel like it.

Remember B2B works all year, and in an emergency could be used stationary, at 1000+ revs, with any neighbours permission.

 

[Kannon Fodda]

Rocking Rivet

Remember B2B works all year, and in an emergency could be used stationary, at 1000+ revs, with any neighbours permission.

Stationary use of modern engines may not be a good idea. Potentially screws the DPF and other sensors.

If the OP moves every day or two, but shorter hour long or so drives a high capacity B2B is the best choice rather than added solar. Solar is fine, if it's sunny. The B2B connections can bypass the Sargent, indeed necessary to avoid a back loop with the Sargent charging circuit. In Ducato based motorhomes bypass may be as simple as pulling a fuse from the connection fusing often mounted behind the drivers seat in RHD vans. Cable size a useful calculator : https://www.12voltplanet.co.uk/cable-sizing-selection.html

 

[gerry mcg]

To a certain extent, the choice of B2B charging rate depends on the size of the battery bank you are trying to charge and the battery chemistry of the batteries.
For lead batteries Inc AGM, the max charge rate should be the battery capacity (C)/5
So your onboard charger at 25A already is sufficient / exceeds that.
With lead / AGM Batteries, you should only deplete your battery bank to a maximum of 50% SOC, south in theory, you would be able to charge a 50% depleted battery in 2 hrs. In truth, the charge absorption rate of wet lead AGM Batteries drops off significantly at 80% SOC, south that final 20% could take several more hours.

Lithium batteries do not suffer these limitations, and can be discharged to 10% SOC safely and can absorb as much charging current that can be thrown at them so czn charge quickly. Actually the purpose of the B2B is to limit the charging current (not boost) the charging current being drawn from the alternator.

In my case, I have 200Ah lithium with a 50A B2B.

I don't see much reason to add a 20A b2b at the moment as you don't have the battery capacity or chemistry to benefit from it.

 

[nabsim]

Except: the current Sargent charger is mains so no use off grid. Presumably the Sargent system has some form of split charge system fitted to charge the habitation battery’s. The B2B would be compared to the split charge system. See what voltage is going into the habitation battery’s with the engine running and no hookup is a good place to start.

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[Rocking Rivet]

Except: the current Sargent charger is mains so no use off grid. Presumably the Sargent system has some form of split charge system fitted to charge the habitation battery’s. The B2B would be compared to the split charge system. See what voltage is going into the habitation battery’s with the engine running and no hookup is a good place to start.

First of all Nabsim, have you been moonlighting on TV adverts for Sky? Would the split charger have be fitted by Peugeot, Autosleeper or is it something that is in the Sargent EC 328 box? I don't have anything to test the voltage with, when the engine is running, but if I could find the split charger there may be some info on it. Where is it most likely to be?

 

[autorouter]

The split charger is built into the Sargent EC328 box. It is a big relay, which is an electrically controlled switch. It is switched on by a signal wire from the alternator that tells it that the engine is running and the alternator is providing power.

This relay simply connects the leisure battery to the starter battery, so the alternator charges them as if they were one big battery. When the engine stops, the relay turns off and disconnects the leisure battery from the starter battery.

There is a 20A fuse on the wire from the starter battery, and also a 20A fuse on the wire from the leisure battery. That gives you an idea of how much charging amps the alternator is expected to send to the leisure battery. 20A is about right for a single battery of say 80 to 100Ah

 

[nabsim]

First of all Nabsim, have you been moonlighting on TV adverts for Sky? Would the split charger have be fitted by Peugeot, Autosleeper or is it something that is in the Sargent EC 328 box? I don't have anything to test the voltage with, when the engine is running, but if I could find the split charger there may be some info on it. Where is it most likely to be?

If I am in Sky adverts they aren’t paying me and didn’t let me know

Wait for someone familiar with the Sargent who can say how efficient the split charge system is, most manufacturers didn’t fit very efficient split charge systems either in relay used or cable sizes from what I have read. If it turns out yours is one of the less effective systems you may have the choice of either a decent split charge or B2B system to suit your needs.

It is fairly easy to fit either system yourself and doesn’t need a dealer (check if you still have warranty). I recently redid the cables on my B2B with a kit from simplysplitcgarge.co.uk and I found it quick and easy. You can get a local garage or mobile fitter to do the work for you unless you know someone on here who could help.

Start with a multi meter on habitation battery and see what voltage you are getting with the engine running. Also see what the electric gurus on here suggest as I have put it simplistically, some vehicles need different approaches

 

[autorouter]

The problem with a split charge system is that the alternator doesn't know there are extra batteries connected. If you connect two leisure batteries, or even half a dozen, the alternator will still send out its 20A to share between them all. If you want more than that,you need a B2B.

A B2B, also called a charge booster, takes 12V power from the alternator/starter battery in the same way that the lights, wipers and fan take power. They demand power and the alternator supplies that demand. A B2B is a proper multi-stage battery charger, powered by the alternator. It boosts the voltage to whatever it thinks is correct for the battery charging. It can have different charging profiles to match the different battery types, some of them do lithium as well.

I'd say it's better to go for separate solar controller and B2B, unless you know exactly what you want and are sure you won't need to upgrade either of them. Some B2Bs have different settings like half power. So you can get a 40A B2B and set to 20A for a single battery, then set it to 40A when you get a second battery. It's not so important for a solar controller - you won't get more than 20A with less than 300W of solar.

 

[Gags]

Have a look at the Renogy 50 amp B to B charger/solar charge controller, i have just fitted one along with 3no additional 100w panels (so 400w total) and my 260 amp leisure batteries are fully charged from the night before by 9am, its a great set up and takes care of everything, i am just about to fit a 2000W pure sine wave inverter as i have bags of power and want to test the system before i go to Europe in june, the Renogy will push either 50 amps from the alternator whilst driving or 50 amps from the solar whilst stationary or 25 amps from each, it charges the engine battery first then the leisure battery, when both are full it trickle charges the engine battery. its quite cheap compared to the rivals and you can get a great digital display unit off e bay which is a third of the price of the renogy unit which does exactly the same, i have been using this on my 2018 Chousson 630 with electric beds, table and Webasto heating and i am very impressed with the set up, for about £600 quid (fitted myself) i can only use about 10% of the available power.

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[Gromett]

For a 100Ah battery a 20A B2B would be fine. I haven't come across that particular unit but it seems quite clever.

The problem is if you are going to add more solar in the future and change to lithium, which can take a higher charging rate I seem to recall, the unit may not meet your needs.

However, you can always run another solar panel off a separate controller if the CTEK can't cope.

What DBK said. I would add that with a single 100Ah lead acid battery you have <50Ah of usable capacity. So a 20A B2B would charge from effective empty to pretty much full in around 2.5Hours of driving. You obviously won't get the full absorption phase.

If you then go for say 200Ah of lithium you may have as much as 180Ah usable. A 20A B2B would be a bit weedy in this situation and as Lithiums don't really have an absorption phase you can get a much faster charge rate per hour of driving across more of the range of the batteries capacity.

If you are seriously considering Lithium I would look at a bigger B2B now to save you having to upgrade it later.