Battery Charging

[ChrisD]

Hello everyone

 

I have a compass avant-garde with a split charge relay for charging the leisure battery.

I am keeping the vehicle battery topped up with a 100 watt solar panel and charge controller.

 

Will the split charge relay operate when the vehicle battery is fully charged or does it require the ignition to be switched on which of course is not feasible. (unless we want to say goodbye to the camper!)

 

Would be grateful for any advice

 

Chris

 

[Brambles]

The split charge relay is operated by the alternator D+ output which basically turns on the slave charge relay when the alternator output is generating 12 volts. This then in effect joins the positive of the leisure battery to the positive of the vehicle battery so both can be charged from teh altermator. When the engine is not running the slave relay is open so the vehicle electrical sytems are isolated from the leisure electrical systems.

[colin]

You seem to have gone the opposite way to most re solar.

The 'normal' set up is to have a solar panel charging the leisure battery and then using any excess to keep the vehicle battery topped up. If you mainly want the solar to keep the vehicle battery topped up when not in use 100w is way OTT, 10 or 20w is easily enough.

[ChrisD]

Hi Guys

 

great replies. Learned a lot from that, thank you.

 

Colin we normally use the panel for charging the leisure battery but the vehicle battery runs down when the camper is sitting on the drive so I switched it for the time being. Is there a way to charge both batteries from the panel without having to disconnect either one?

 

 

[Brambles]

Connect the two batteries via a cable, switch, and a fuse is one way. Make sure you disconnect or isolate (switch) before starting engine. If you want to make more sophisticated you could put a light bub in series. If you are just needing a trickle charge to the leisure batteries then a 21 watt bulb is sufficient. Start the engine by accident and the bulb lights and protects the wiring from high starting currents, rather than the fuse blowing.

You can also get dual output solar chargers which will keep both topped up independently.

[gocro]

Our vans and cars start up no bother after four weeks in this weather. Worthwhile checking the drain on the vehicle battery to see if something is causing it to lose power, or get the battery checked if there is no obvious drain ie more that half an amp.

 

[artheytrate]

This is what I've fitted to my previous vans, as soon as leisure battery is fully charged it then switches auto to cab battery very easy to wire as only 3 wires one to earth, one to leisure, and one to cab battery.

Ebay £23-89p

SOLAR WIND SPLIT CHARGE LEISURE & ENGINE BATTERY CAMPER MOTORHOME BOAT 12V

 

 

 

 

 

 

 

 

 

 

 

 

 

[aandncaravan]

You can swap the existing D+ operated split charge relay for a voltage sensing relay, like the Heavy Duty Durite unit.

When the charging voltage at the Starter Battery goes above around 13.6v the Durite connects the Habitation battery into the Starter Battery loop. So once the Durite unit is fitted the two batteries will connect together whenever either the Alternator or Solar Regulator raises the Voltage at the Starter battery to about 13.6v.

The Durite unit then disconnects batteries from each other when the Starter battery voltage drops to around 13.2v'ish.

Easy to fit, one +/positive wire and -/negative to Starter battery and +/positive to habitation battery.

 

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[Brambles]

You would have to be careful it did not get in to a switching cycle loop. Switches in the other battery when voltage goes above 13.6 volts, but then the solar panels cannot supply the extra drain (where as an alternator would) and so voltage drops. The unit disconnects from second battery, voltage rises and it switches it back in...voltage drops....I think you get the picture.

[aandncaravan]

Brambles, Sorry the dropout voltage is 12.8v not the 13.2v I quoted. However, 13.6v is a pretty strong Solar voltage. On a 100 watt panel would normally have decent current to back it up. So unlikely to get into a Switching cycle.

 

 

The item mentioned in the third to last post, SOLAR WIND SPLIT CHARGE LEISURE & ENGINE BATTERY, is not an ideal solution?

 

We describe these as 'power theft' devices because while the marketing says that they only charge the Starter battery once the Leisure battery is full, it is incorrect.

They connect the Starter battery into the circuit (when used as designed to 'top up' the Starter battery from Solar) when the voltage at the leisure battery reaches 13.5v. The marketing makes the assumption that the leisure battery voltage will only reach 13.5v once it is charged.

 

However, the Battery theft devices 'see' the voltage at the battery, not the battery voltage itself. So as soon as the Solar Regulator outputs anything greater than 13.4v, the Battery theft device will 'see' the 13.5v and begin diverting current to the Starter battery even if the actual habitation battery is only 11v. In other words when you want every drop of power to go into the Habitation battery, some is 'stolen' away.

 

They also have a habit of not disconnecting until very low volts, like 12.3, sometimes allowing the habitation battery to steal the power back from the Starter battery, potentially at the expense of not being able to Start the engine.

 

They were designed a few years ago as low power units when Solar Regulators that charged both Habitation and Starter battery simultaneously were rare. They are now common place and cheap, less than the cost of a Single battery regulator + Power theft device.

A dual battery regulator is simpler so inherently more reliable as well as more efficient. Also easier to wire up.