B2B preference

[TheCaller]

These videos are good, but I wouldn't say excellent. He talks about a '100 to 200 amp battery', as if he wanted the charging current to be 100 to 200 amps.

The recommended charging current for a 100 to 200 amp-hour lead-acid battery bank is C/5, which is 20 to 40 amps.

Agreed. In the first video he completely ignores the recommended maximum charge rate & talks about 100/200 Amp batteries, when he clearly means 100/200 AmpHour batteries. He is suggesting a 100A+ charge rate when those batteries should only get 60A max. A narrowboat (Sterling's background) may well have an 800AH battery bank, which could take the 100A+ charge rate, but outside the RV market, very few motorhomes have more than 2 leisure batteries. I know several dedicated wild campers on this forum do, but they are in the minority on here & in a tiny minority in the market as a whole. Lithium is a whole different ball game, but he makes no suggestion that it's lithium batteries he is taking about.

In the second video he then does make a big play about the C0.3 charging rate, which many would still consider high for any of the lead based technologies & certainly so for Gel. Contradicting what he said in the first video. I watched them on my phone, so not easy to see how closely together they were made, but they looked to be part of a related series - same shirt & same white board!

I agree with his conclusions - a B2B charger is an excellent idea for anyone who camps away from EHU & stays in one place for more than a couple of nights at a time. It is also more or less essential for anyone with a Euro 6 vehicle. The reasoning he gives appears to be flawed, yet I find it difficult to believe he doesn't know that.

He's not very complimentary about the Sargent unit & he has a point. It's not up to the job he is describing. But he is ignoring the fact that the Sargent fulfils its design brief very well. It's a piece of kit designed to be a one box easy fit unit for volume converters who are selling to the UK market where most motorhomes are never away from EHU for more than 24hrs while in use. It will be fine for 80% of the motorhomes sold in this country & for even 50% of members on here. I wouldn't want one though.

 

[Diabalo]

Use D+ the B2B will only activate when the alternator is charging.

Not sure if everyone has an EM40 interface unit but on mine the wiring diagram shows Tow D+ low D+ neg (fridge) 2x Fridge D+(fridge Positives) and Low D+ Signals to PSU

Would it be ok to piggyback of the fridge positive?

 

[Revolvor]

Not sure if everyone has an EM40 interface unit but on mine the wiring diagram shows Tow D+ low D+ neg (fridge) 2x Fridge D+(fridge Positives) and Low D+ Signals to PSU

Would it be ok to piggyback of the fridge positive?

I have a EM50, and did exactly that - took a feed from the Fridge Positive to energise a relay that disconnects the Sargent charger when the engine starts. I was fitting a Ctek Combined Solar Charger and B2B.

 

[Pausim]

Not sure if everyone has an EM40 interface unit but on mine the wiring diagram shows Tow D+ low D+ neg (fridge) 2x Fridge D+(fridge Positives) and Low D+ Signals to PSU

Would it be ok to piggyback of the fridge positive?

I don’t know about Sargent wiring but it sounds reasonable as long it is only live when it gets a D+ signal.