Solar and B2B Device

[DavyS]

I have a B2B device which when the leisure battery voltage is above 13v (i.e connected to EHU or engine running) will open an electronic switch and connect the leisure and cab batteries together to give the cab battery a trickle charge up to 2A. It works very well.

But now I want to install solar and face the usual decision of whether to go for a system that charges both batteries or just the leisure battery.

My feeling is that I need a system that just charges the leisure battery and the B2B device will continue to charge the cab battery.

Am I right?

[Derek Uzzell]

I think you own a 2015 Peugeot Boxer-based Elddis Accordo 105.

 

Can you provide details of the B2B, please? Is this a genuine B2B that was part of the motorhome's standard specification to cope.with a 'smart' alternator, or just a device (eg. a "Battery Master") that was retro-fitted to trickle-charge the vehicle's starter battery when the motorhome is on 230V hook-up.

[mikefitz]

My guess is the b2b device is a battery maintainer. This will work well with solar when the leasure battery is under charge from the solar controller. This is a better option than a controller with dual output , as the leisure battery will receive a correct charge.

I recommend the more expensive MPPT rather than a low cost PWM controller. Suitable units are available from Victron, Epever, Votronic. Divide the panel watts by 12 to determine the power rating of the controller, for example 200 watts of solar panel will idealy produce 16 amps with an ideal MPPT controller.. With horizontal panels and conversion losses the current will be lower, so a controller rated at 15 amps or higher will be suitable. ( note all MPPT controllers can tollerate being slightly 'overpaneled').

 

Mike

 

[Alanb]

Hi,

 

The B2B device described, will be a small voltage sensitive relay (VSR), arranged to monitor the habitation battery voltage and CLOSE a contact to couple starter and hab batteries when hab battery voltage is greater than 13V. I would expect to find a thermistor in series with the contact. It is the thermistor that limits the current to about 2A.

 

As stated by DavyS the device operates when on EHU, or when the engine is running, but in this latter situation I would expect that a separate split charge relay to be already coupling the batteries.

 

I fully agree with DavyS's suggestion, that he only needs a single output solar regulator connected to the hab battery.

[DavyS]

Thanks guys for reassuring me. A single MPPT controller of about 150/12 = 13 amps should suffice then.