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Old 11-28-2018, 02:39 AM
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wpoll wpoll is offline
Join Date: Sep 2015
Location: South Island, New Zealand
Posts: 2,477
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While Andrew is correct in pointing out that the 2.2kW will draw more power than than the 2.0kW starter, I do wonder if the extra load is going to be the difference between needing the regular top-up charge or not. I reckon that given your (VERY) short regular trips, you may well be faced with the top-up charging regardless of which starter you end up fitting.

I have tried to figure out what distance is needed for a "break-even" trip on my 3.0d, in terms of battery charge. While I don't have any actual figures to back up my conclusion (like battery specific gravity, starting load etc.) I have found that unless I'm travelling something like 20kms each trip to recover the charge used at start-up, I end up having to top-up charge the battery after a week or so. At least in the winter anyway, with near-zero degree starts two or three times per day. Summer is WAY better.

I guess in Cyprus, it'll be a lot warmer and so you may not have to travel as far, the start-up load being less.

The maths on this doesn't help much. If you assume the battery has 100AH capacity and the start-up load is 300Amps (starter, plus glow-plugs etc.) for 5 seconds, that equates to around 0.4% of the total battery capacity (100Ah/300Amps = 20mins; 20mins/5secs = 100/240 = 0.4%).

Of course, this is without de-rating the battery to allow for internal resistance etc. De-rating figures for car batteries are hard to find but could be as high as 50% i.e. when delivering 300Amps the 100AH battery may only deliver 50AH. This could raise the charge usage for start-up to near 1% but this still seems too low for what I have observed in real-world usage.

Maybe my battery is on the way out too and the actual capacity is WAY lower than I am calculating.

I suspect that part of the answer lies in the E53's issues with low voltages - it needs a GREAT battery for reliable operation, not just a good one.
2005 BMW X5 3.0d (b 02/05)
2001 BMW F650GS Dakar (b 06/01)
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