Unusual issues caused by a failing battery

[JLA]

A mate also has a D40 stx550. For some months his spanner/service indicator comes on too early at 5,000klm. He took it back to the service mob who reset it but assured him they had previously reset the interval to 10,000klm. Then the spanner happened again after another 5,000klm. By then he knew how to press the buttons to reset the interval himself.

Over the same period he has been complaining about the poor fuel economy, about 15. That’s not towing and it’s on the flat. I agreed that was poor.

His start battery is a high crank AGM. Unusual choice but it has lasted seven years. He chose it because he thought the stuff would not vibrate out of the plates as easily. A battery test showed this 700amp battery was stuffed. It was only cranking out 220amps, so the voltage would have been greatly sagging during a start. It was apparently sagging to below where the computer could operate. Each start the computer thought the power had been disconnected so it initialised back to default settings. This set his service interval to 5,000klm. It also reset the learned fuel settings. I recall that after a power cut it takes a tank or two of fuel before the economy becomes normal.

Every time he started his vehicle in the last few months the settings initialised, he had no chance.

It is possible that a flooded lead acid battery would never sit on the threshold for so long so it might be a problem that happens only with fading AGM batteries. Who knows?

 

[Old.Tony]

There's no difference chemically between AGM and flooded cells. They do the exact same thing in the exact same way. AGM are a little less prone to sulphation problems but they can boil off electrolyte just like a flooded cell battery. Because of the glass mat between the plates, AGM batteries are a little more sturdy.

But they still age. The plates slowly degrade with use.

It's interesting that the low voltage kept causing the ECU to do a full reset. Something to keep in the back of the mind eh!

 

[Homeonthe]

JLA mentioned above that his mate's fuel economy on his ST-X 550 was 15 ltrs/100kms. I can get up to that driving around Sydney's stop/start traffic at any time of day, but I generally average mid-14s. If I get a clear 15+km run on the M4 freeway @ 90 to 100 km/hr, this can drop to 10.4 ltrs/km (once I reset it to zero at the start). That, to me is good economy. Also, my ute is usually only lightly loaded, just carrying around 50kg in tools, plus me (85kg give or take 10 .

 

[shane_1]

I too had a similar battery issue. As the battery was dying, every now and then it'd reset everything (clock, trip meter, radio) when i would start the ute. Also, every second time, the instruments would do that crazy flicking around and ecventually settling down after 60 seconds or so. New battery, no problems.