Lifeline Battery Advice?

[KenMcCulloch]

We have a fairly mainstream electrical system with a main battery bank consisting of 2x110Ah conventional flooded batteries, and a smaller backup bank which is a single Lifeline AGM battery. A 1-2-both-off switch allows selection. Charging is either by the engine alternator via a Sterling external regulator with its output going to the common (supply out) terminal on the selector switch, or via the mains charger. Charging by engine is simply selected using the selector switch. We don't use the Lifeline battery much, treating it as an emergency supply, but do select it occasionally both to start the engine and give it a charge for an hour or so from time to time.

My question is about the pros and cons of connecting the Lifeline battery to the spare output on the mains charger. The charger is specified as producing a boost voltage of 14.4V and float voltage of 13.8V. There are 3 outputs from the charger only one of which is sensed, currently that and one other output are connecetd to the 2 main batteries. What are the pros and cons of connecting the Lifeline battery, which as I understand it requires a slightly different charging regime from a FLA battery? If I did that which battery should the voltage be sensed from?

 

[pvb]

My question is about the pros and cons of connecting the Lifeline battery to the spare output on the mains charger. The charger is specified as producing a boost voltage of 14.4V and float voltage of 13.8V.

14.4v won't harm your AGM battery, so you could connect the mains charger to it. Sensing should be from the main bank.

However, have you checked that your Sterling regulator is set for AGM batteries? If it isn't, your AGM battery could be getting excess voltage during engine charging. Unfortunately, setting the regulator to AGM means that your main bank won't charge quite as efficiently. Mixing battery types isn't recommended, for this reason.

 

[VicS]

We have ........
which battery should the voltage be sensed from?

You dont say exactly what alternator regulator or battery charger you have . This makes it difficult to consult the correct documentation.


Unusual to have a voltage sensor on a battery charger .... Are you sure it is not an ( optional) temperature sensor ?

If so I would connect one of the three outputs to your " emergency" battery and connect the other two to the main battery bank. There is no guidance in the manuals I have looked at as to which battery the temperature sensor should be fitted. Not critical I assume.

If you are right about it being a voltage sensor then the manual should indicate which battery it should sense. RTM, as they say

As pvb indicates the battery type settings should be for the one requiring the lowest charging voltage. The battery manufacturers documentation should be consulted rather than just relying on the standard settings

OTOH your alternator regulator will have a voltage sensor.
With your set up it should be connected to the common terminal of your selector switch.
It is important that it is not connected to a battery which may not be receiving charge.

 

[KenMcCulloch]

Thanks for those helpful responses. It's a Morven charger and the documentation clearly specifies that one of the outputs senses voltage. The mixed batteries were inherited, I am not sure what was in the previous owner's mind when spending at least twice the price of a third FLA battery on the Lifeline AGM.

 

[ditchcrawler]

I have two sealed traditional 110a/h batteries as my domestics and a Red Flash AGM as my starter battery so very similar to you with the Red Flash on no1 and the domestics on no 2 of my 1/2/both switch.My Sterling alternator management system is set to charge at 14.4v by the electrician who installed it and my Sterling mains charger is also set to charge both sets of batteries at the same setting.
This was as recommended and fitted by the marine electrician.I do not know if my mains charger is sensed on either bank.
I went for the small size of the Red Flash due to space restrictions.It has a small capacity,27a/h, but a large cranking amps value.I use it just for starting,charge it for 10 mins or so and then switch to my domestics.