Secondary battery bad alternator

[caliche]

Hi everyone...looking for some advise here.
I recently installed a LIFEPO4 secondary battery (100amps) on my rig (LX470 2007) with a DC to DC automatic charger (20amps) connected directly to the car's started battery which charges the deep cycle battery while the car is running or idle (takes about 4h to fully charge). It's worked great since installed 3 months ago. This week, the original alternator (130amps) have gone bad and needs to be replaced.

Is it possible the deep cycle battery caused the alternator to go bad? or does not have anything to do with it given the dc to dc charger is in place?
Should get a bigger alternator or keep the same 130a alternator?

Any thoughts or feedback appreciated.
Thanks

 

[Sparksalot]

I’d guess is it’s coincidence. How old is the alternator itself? They do fail even in purely stock applications.

 

[caliche]

15 years....that was my gut feeling too...coincidence (hope - dont want to put another 130amp alternator that gets burned if that is the issue)

 

[smritte]

Most often its the alternator brush's that wear out. The electronics in modern alternators are pretty solid and it takes a bit to burn them out. But never say cant happen, it's just not common.

A low Lead Acid or AGM can draw around 40 amp's, your vehicle normally under 20 amps. Add everything else together and if your under 80% of your alternator then your good and don't need to go bigger. "Some" lithium's can draw a huge amount but most DC-DC chargers keep the current flow down so the batteries don't overheat.

If you decide to upgrade your alternator, look into hairpin alternators. The biggest obstacle around higher output alternators is poor output at idle and some dont put out much until around 1200 rpms giving full output near 4500 rpms.

My hairpin alternator puts out just over 100 amp's at 700 rpm and 250 amps at 2100. Between my two batteries in my vehicle, two in my trailer and two fridges, my stock 85 amp wasn't near enough. It will also help when running the winch.

 

[caliche]

Most often its the alternator brush's that wear out. The electronics in modern alternators are pretty solid and it takes a bit to burn them out. But never say cant happen, it's just not common.

A low Lead Acid or AGM can draw around 40 amp's, your vehicle normally under 20 amps. Add everything else together and if your under 80% of your alternator then your good and don't need to go bigger. "Some" lithium's can draw a huge amount but most DC-DC chargers keep the current flow down so the batteries don't overheat.

If you decide to upgrade your alternator, look into hairpin alternators. The biggest obstacle around higher output alternators is poor output at idle and some dont put out much until around 1200 rpms giving full output near 4500 rpms.

My hairpin alternator puts out just over 100 amp's at 700 rpm and 250 amps at 2100. Between my two batteries in my vehicle, two in my trailer and two fridges, my stock 85 amp wasn't near enough. It will also help when running the winch.

Thanks, this is very helpful!