Switching to AGM

[RosieR]

Hi there! My sealed lead acid batteries are nearly six years old and unfortunately they won’t hold their charge so Ive done a lot of research and just bought two AGM deep cycle 150aH batteries to replace my current two 200aH lead acid. My battery charger is a fairstone ABC1230 Fully Automatic 5 Stage and I’m pretty confident they’re compatible. My last fear is that I haven’t changed my starter as it’s still in good health but it is lead acid. Will having two battery types negatively effect the health of my batteries? 

[cuthound]

It depends on the AGM's you bought. The very best ones, like Lifeline will take a higher voltage charge, but most won't. Have you set your charger up so that the float voltage is compatible with AGM's? Typically about 13.2 volts, but check what your battery manufacturer recommends. If not your new AGM's may not last long if they are floated at too high a voltage.

 

If your charger has two outputs and charges your starter battery from the second output, then if the starter battery is a wet lead acid type, the AGM float voltage may be a little low for it, but given that starter batteries don't get discharged much (unless the engine doesn't start and you keep on cranking it over)  I doubt it will do it much harm in the long term.

 

Edited July 1, 2022 by cuthound
Clarification

[RosieR]

It’s my first time changing over batteries so I wasn’t even aware you could adjust the charger! All the information is overwhelming, I’ll look into all of that, thank you:)

[Jen-in-Wellies]

10 minutes ago, cuthound said:

If your charger has two outputs and charges your starter battery from the second output, then if the starter battery is a wet lead acid type, the AGM float voltage may be a little low for it, but given that starter batteries don't get discharged much (unless the engine doesn't start and you keep on cranking it over)  I doubt it will do it much harm in the long term

My boat spends its time when not cruising on a shore line. My first starter battery wasn't connected to the charger second output at all and so had no charging, other than when the engine was running. It lasted ten years before it died

[Sea Dog]

6 hours ago, Jen-in-Wellies said:

My boat spends its time when not cruising on a shore line. My first starter battery wasn't connected to the charger second output at all and so had no charging, other than when the engine was running. It lasted ten years before it died

Mine's the same Jen. Whilst my solar tended to the domestics for the many months my boat was unattended in lockdown, the starter battery was isolated as always when I leave and it sat there fat, dumb and happy with just a tiny bit of self discharge.  I have a CTek indicator connection which was flashing yellow when we eventually returned, but the engine started first time and the starter battery topped back up none the worse for the neglect.

Canal boat starter batteries have an easy life.

[Tony Brooks]

41 minutes ago, Sea Dog said:

Canal boat starter batteries have an easy life.

 

And most have a far larger capacity then strictly needed so lots of sulphation can take place before it even starts to be noticable.

[Ronaldo47]

My  Ctek battery charger has three charging options.  The first is for motor cycles, the second for cars, and the third (indicated by a snowflake)  for  both keeping a car battery  in good condition during extended periods of non-use or cold weather, and also for charging SLA batteries.

 

Batteries designed for different purposes often have slightly different acid strengths. They therefore have slightly different voltages when fully charged, hence the need for the different settings.  

 

 

 

 

[Sea Dog]

43 minutes ago, Ronaldo47 said:

My  Ctek battery charger has three charging options.  The first is for motor cycles, the second for cars, and the third (indicated by a snowflake)  for  both keeping a car battery  in good condition during extended periods of non-use or cold weather, and also for charging SLA batteries.

Might be worth a quick check on the snowflake purposes. Are you sure it's not for very cold weather and/or AGM batteries?

 

The multi stage CTek charger are purpose designed to keep smaller capacity and larger capacity batteries in good condition for long periods using the motorcycle and car settings respectively.