Safe way to use trickle charger?

[Chisca]

I'm using a battery tender on a 1984 318i that is driven infrequently and I think I have fried the diodes in the alternator. Is there a safe way or a better charger to use with the bosch alternator to keep the battery charged when the car sits for weeks at a time? I have gone through two alternators in 6 years which seems excessive. Or does this have nothing to do with keeping the battery on a trickle charger?

[Manolito]

I have been working around batteries for 50 years, and to my knowledge, a battery tender should have no adverse effects on your alternator. The things that I typically see causing premature failures of alternators are:
1) Excess load. People add aftermarket lights and amps and ask their alternators to put out close to or greater than their rated capacity for extended periods. Depending on mounting location and the fan on the pulley, an alternator will generally put out 100% of its rated capacity for only a few minutes before it starts to overheat.
2) Poor connection between the alternator and battery, resulting in voltage spikes. The voltage regulator is designed assuming that there is a 'big electrical sponge' on the other end of a good electrical connection that is keeping the voltage from making any sudden changes.

[Chisca]

Thanks so much. I have moved the battery to the trunk and will recheck all the connections to make sure that isn't the problem. No added accessories so I know that's not the issue. I have used a battery tender on my motorcycles and have never had a problem but after reading the pelican troubleshooting guide on Bosch alternators I made a false assumption about overcharging and diodes.

[Jared at Pelican Parts]

A battery tender wont do anything to the alternator.

How did you wire the battery when you re-located it to the trunk?

[Chisca]

8 gauge wire to a power distribution block that is mounted where the old battery was. I cut off the original clamp that connected to the battery and soldered a copper eye lug to attatch to the power distribution block. Odyssey PC 1500 battery.