How to install a battery master in my RV ?

[missoo]

Hi everybody,

I'd like to install a battery master in my RV in order to charge my engine battery with secundary lifepo4 battery.

In France, people usually use the CBE CSB2. When the leisure battery voltage is lower than 12.5V, the car battery recharging system is deactivated.
However, I have read that there could be some draining issues on lithium leisure battery.
Why would it be a problem as low voltage disconnect for lithium battery is around 11 V ?

CBE has developped a new product the CSB2-LT, which is only for lithium batteries.
With this one the car battery recharging system is also desactivated in the absence of a “230V network signal” and “solar signal”.

I was thinking of using this last system. However I don't understand how to wire it to the "Input solar signal " and "Input 230V net signal".
CBE told me it could be only used with a CBE solar charge regulator and CBE charger. What do you think ?
Here are the connections for the CSB2-LT.

Could I used the first one I mentionned using a switch in the case I don't have my solar panels working ?
Could I have draining issues at night ?

Thank you so much for helping I am really confused.

 

[missoo]

Anybody that can help me here ?

 

[mikefitz]

Anybody that can help me here ?

I will try.
note that the battery master devices are not battery chargers, they provide a maintaining current to compensate for battery self discharge and van circuits small current drain, they will not full charge a discharged vehicle battery.

The CSB2 is installed between the service battery and the engine battery. Its a simple circuit with a resistor, current limiting components and a diode in series. When connected between lead acid batteries and the service battery is under charge there is a voltage difference between the two batteries, the diode conducts and current flows from the battery under charge to the engine battery, limited by the resistor. With a typical service battery charging voltage of around 14 volts the engine battery will reach 13.4 volts, a reasonable maintaining voltage.
This is what you get in a CBS2 case,


CBE decided the CSB2 would not work with lithium batteries and developed the CSB2 LT, this works in a similar way but is only enabled to pass current when the AC charger or the solar charger is active. The thinking behind this is that with lead batteries the chargers will be at a high voltage for some time and allow current to flow through the CBS2. Because with lithium the charge voltage will be at a lower voltage for the majority of the charge cycle, the engine battery would not receive enough charge. Whilst the CBS2 may be slightly less efficient with Lithium batteries I think it would still function well enough.

I use a very simple circuit to maintain the engine battery from the service battery. A 12v filament bulb ( as a non linear resistor to limit the current) in series with a Schottky low volt drop diode. Unless the engine battery is in poor condition and needs replacing you only need a fraction of an amp to compensate for self discharge and van circuits. Suitable bulb is 10 watts, for higher current use a 21 watt bulb with 5 amp diode and fuses.

10w circuit,



With this system the lithium battery will always be providing a small maintaining charge unless the SOC is low. This has nor proved an issue with the (usually) much larger service battery compared to engine battery.

A maintaining unit that offers programmable options for different battery systems is,

alternative product,

Ablemail AMT12-2 Battery Maintainer

<p>The AMT12-2 Trickle Charger has been designed to keep a vehicle’s starter battery charged and protected from damage during prolonged perio...

www.roadpro.co.uk

Reports are that it works well.

Mike

 

[missoo]

Hi Mike,

Thanks for your explanations. It's much clerarer. As I already bought the CSB2 I'll try it then

I am already trying to install it. The wiring is ultra simple but I still have a question sorry ...

The CSB2 should be connected to the earth. Does it mean to the chassis ?
Also, my service battery was not connected to my car battery yet, but it is going to be with the CSB2. Does it mean that using a CSB2, I also need to connect my service battery to the chassis ?

Sorry, it's not easy for me to understand all that.

 

[missoo]

Using your diagram, can I connect what they called the "earth" wire to the negative terminal of my leisure battery ? Would it work ?