Extra battery charger

[Sp0_0k]

I want to install a second fridge and solving an autonomous charging for the extra battery.
I charge it only from a hookup now but want to charge it from an alternator as well.
Easiest way without serious modifications I had in mind is to get the current from the cig lighter socket. It has a direct connection with alternator anyway when the engine is running.
The tricky part is to cut charging when the engine stops. Should be easy by simply detecting the lowered voltage.
Let say above 14volts in cig socket, the charger is feeding current to the battery. When the engine is turned off and even if the leisure batteries are fully charged they don't give that voltage.
Or maybe there is an easier way to accomplish it all?

 

[WelshGas]

OK, you have 1 Leisure battery that charges from the engine and you want to install a 2nd one and also have that charged from the alternator as well.
I think using a 12v socket could lead to problems as if the 2nd battery is low you could get a significant current flow. You only have to look at the wiring connecting the original battery to the charging circuit and compare to the wiring for the 12v socket to see what would be needed. Why do you not connect the 2nd Leisure Battery to the original battery in parallel with an in-line 80amp fuse as on the Ocean. As long as both batteries are the same type and capacity then there will be no problems. Both will charge from Alternator and Mains charger.

 

[WelshGas]

Remember though the batteries should be connected with high capacity cables capable of 80amps +.

 

[Sp0_0k]

Because 2nd battery is like twice bigger.

 

[WelshGas]

Unfortunate. I think you will have problems then.
Solar Panel for 2nd battery?

 

[Loz]

Because 2nd battery is like twice bigger.

As long as they of the same type it wont matter about the capacity as it will act like a large cell.

 

[Sp0_0k]

Yea I planned to add solar a bit later. Right now there is no much camping in 1 spot under the sun.
So most charge I can get is from alternator.
Loz, by the type you mean like AGM?

 

[Loz]

Yea I planned to add solar a bit later. Right now there is no much camping in 1 spot under the sun.
So most charge I can get is from alternator.
Loz, by the type you mean like AGM?

yes

 

[sidepod]

I want to install a second fridge and solving an autonomous charging for the extra battery.
I charge it only from a hookup now but want to charge it from an alternator as well.
Easiest way without serious modifications I had in mind is to get the current from the cig lighter socket. It has a direct connection with alternator anyway when the engine is running.
The tricky part is to cut charging when the engine stops. Should be easy by simply detecting the lowered voltage.
Let say above 14volts in cig socket, the charger is feeding current to the battery. When the engine is turned off and even if the leisure batteries are fully charged they don't give that voltage.
Or maybe there is an easier way to accomplish it all?

Unplug it when you kill the engine? Or is that too easy?
Failing that install a dedicated split charge relay to isolate it.

 

[WelshGas]

As long as they of the same type it wont matter about the capacity as it will act like a large cell.

Considered wisdom from many sources is that Batteries wired in parallel must be of the same type AND same capacity and approximately the same age to avoid problems.

 

[Sp0_0k]

Loz seems right. There is no problems running different capacity in parallel.
Sidepod, that's an interesting idea with split charge relay. Any working solutions already on the market or should I build my own?
I know about the CTEK dual. But it is designed to connect to an auxilary battery/alternator. So do I simply stick that end into the cig socket?
I read there is a problem with such relays running with "smart" alternators.

 

[Loz]

Considered wisdom from many sources is that Batteries wired in parallel must be of the same type AND same capacity and approximately the same age to avoid problems.

Only a problem when using batteries in series.

 

[WelshGas]

Loz seems right. There is no problems running different capacity in parallel.
Sidepod, that's an interesting idea with split charge relay. Any working solutions already on the market or should I build my own?
I know about the CTEK dual. But it is designed to connect to an auxilary battery/alternator. So do I simply stick that end into the cig socket?
I read there is a problem with such relays running with "smart" alternators.

Battery makers disagree about connecting batteries in parallel that are dissimilar in output, type or age.
https://www.optimabatteries.com/en-...i-connect-dissimilar-batteries-parallel:thumb

 

[Loz]

Battery makers disagree about connecting batteries in parallel that are dissimilar in output, type or age.
https://www.optimabatteries.com/en-...i-connect-dissimilar-batteries-parallel:thumb

Optima say this because their batteries are different in construction to any others on the market.

 

[Loz]

Loz seems right. There is no problems running different capacity in parallel.
Sidepod, that's an interesting idea with split charge relay. Any working solutions already on the market or should I build my own?
I know about the CTEK dual. But it is designed to connect to an auxilary battery/alternator. So do I simply stick that end into the cig socket?
I read there is a problem with such relays running with "smart" alternators.

I have a d250s for my portable power pack that I built and it is a good choice because the solar input can charge both the aux battery and maintain the starter battery as well once the aux is fully charged, you can also use a ctek smartpass add-on for your additional battery but the smartpass is not cheap either. See: http://www.ctek.com/sradmin/ARCHIVE...SmartPass_with_Charger_at_Starter_battery.pdf
These should be cabled up properly and not through cigar sockets that are not rated for constant heavy current.

There is also a ctek M300 charger in there, but you can also see a lead with an Anderson plug on it that connects it to the vehicle.

Have a look at the example diagrams on this page http://www.ctek.com/gb/en/page/support/dcdc-support#smartpass

 

[WelshGas]

Optima say this because their batteries are different in construction to any others on the market.

Not just Optima.
But never mind, it's not my vehicle and not something I have ever done in the past nor would consider doing in the future. Best of luck.

 

[Loz]

Not just Optima.
But never mind, it's not my vehicle and not something I have ever done in the past nor would consider doing in the future. Best of luck.

I totally agree it is good practice and I would always buy matching units but not the end of the world in this use case as a ctek monitors the additional battery.

 

[sidepod]

Just simply get another split charge relay and piggyback it onto the existing.
Use the same control and power input from the alternator.
Instead of switching over to leisure batteries on engine switch off simply leave disconnected.
This scheme will isolate your supply as required.
Hard wire a dedicated supply for your second fridge.