Alternator poor charge rate

[Tauras Junior Member Find all posts View Profile Close Tauras]

Hi all, I've recently noticed the charge rate on my alternator has degraded significantly from around 45 amps to an average of less than 15 amps. Believing that the alternator was on its way out on my 2012 D4D with 143k on the clock, I replaced it with an OEX 130 amp version, however this has not resolved the issue. The charge rate tends to degrade as the car heats up and is worse on warmer days.

I have so far confirmed that all grounds are clean and firm, I have also inspected the timing belt which appears to be fine (this was also confirmed by Toyota when they inspected at the last service).

I'm running a Renogy 50 amp DCDC charger to charge a Renogy lithium 50 AMP battery, the battery is rated for an input current of 50 amps which I regularly achieved about 6 months ago (I'm using a Victron smart shunt). I also have a backup charge circuit through a Redarc SBI12, this runs independent of the DCDC and on a switch incase the primary system fails, I've been using this to troubleshoot the issue.

Given my alternator is new, my options are:
- replace all wiring to confirm it is not a fault wiring (although I have tried to charge a third battery with jumpers and experienced the same issue).
- replace timing belt - its due to be replaced at next service but it looks fine and I'm not sure if I would notice it is slipping under load?
- replace fusible link - I'm really hoping to avoid this, on fuse looks fine.
- replace wiring from alternator to fuse box?
- replace starter battery which (its 5 years old but still performs well when tested using a load tester).

Appreciate in advance any other ideas or options.

[zoc Junior Member Find all posts View Profile Close zoc]

you don't really mean timing belt, you mean serpentine belt, right?

what issues are you having? is the battery not charging and causing the car not to start?

they alternator only "delivery" what the circuit requires. higher requirements = higher output.
maybe, as the day/drive goes on the discharge battery is charged more and requires less

how are your measuring the current?

[Leethal Advanced Member Find all posts View Profile Close Leethal]

Replacing the wiring to the fuse box and the fusible link will not achieve anything as the alternator output is dictated by load (demand) so most likely the system is not “demanding” more amps.
As your second battery supply should be off the start battery positive terminal direct via a fuse/circuit breaker to your DCDC charger the fuse box and fusible link should not be in the circuit.
Also of a concern I believe is charging a 50Ah battery at 50 amps, I would be checking all the specifications for the battery to confirm the recommended charge rate is 50 amps, not that it can accept a 50 amp charge rate. An excessive charge rate will reduce the battery life even though the battery will accept the charge.

When you say you have used jumper leads to charge a third battery how did you measure the current and was the battery heavily discharged in order to require a high charge rate

For reference my 100Ah Enerdrive lithium has a recommended charge rate of 35 amps to ensure maximum battery life.

Lee

[carco Advanced Member Find all posts View Profile Close carco]

Renogy DC-DC has a 50% charge option. Check you have wired that correctly or the max it can pump out is 25a.
They also don’t like getting hot, will cut in and out. I fitted 12v fridge fans to vent my gear.
Is the DC-DC coming from a VSR? Even though the switching is capable of 120a, they don’t like long continuous drain and will cut in /out, you’ll be able to check that pretty easily.
And finally, I have bought a lot of Renogy gear, some of it is iffy to say the least, especially their DC-DC’s.
I have one brand new unit now in the cupboard, it’s combined with solar input and the best it will do is 15a. Renogy’s clever people advised me the charging algorithm was working as it should. I replaced it with a straight 40a DC-DC and it pumps 40a constant.
I’m running 25sq mm cable.