Any recommendations for a QUALITY battery tender for my 01 Z3? It will be garaged for much of the winter, and not started at all in December. Griots has one that seems to have all the right specs. Any tricks in getting them hooked up? Jim Kennedy jkennedycma@bellsouth.net
BMW has there own as well, griots is fine. The main idea is to get one that is a smart charger that monitors how the battery is charged and can turn off when it's charged and on when it needs it. To hook it up I would just put it on the jump posts under the hood.
ditto above, also this: http://www.batterytender.com/Automotive/ specifically. this: http://www.batterytender.com/Automotive/Battery-TenderR-Plus.html (I use this one) or this: http://www.batterytender.com/Automotive/Battery-Tender-Junior-12V-0-75A.html
I've been using the Schumacher battery tenders that I pick up at Tractor Supply Co. I have four (4) of their units on my own cars, and another three (3) of them for use on custome'rs cars, when required. I have never found their performance to be lacking, and some of the units must be at least ten (>10) years old by now, with a zero percent (0%) failure rate. At some point point they went through a redesign, as the three (3) most recently purchased units are much lighter (in weight) than the originals, so time will tell if they are any less durable, or if the technology has advanced that much. Historically, I always paid right around $20.00 apiece, but cannot say for certain if the newest ones were still the same, nearly give away price. All include a choice of connection methods, either spring-clamps, or a disconnecting plug can be wired into the car itself. You can always pay more for something with fancy brand names, but these economically priced units include all the quality that I need from them!
I think the best of the best is in the Ctek line. I use this: https://www.amazon.com/CTEK-56-353-...dp/B000FRLO9Y?ie=UTF8&*Version*=1&*entries*=0 After an extended float charge period (>10 days), it knows to put itself into a pulse charge mode that really extends the life of a prolonged period (read; indefinite) tendered battery. I trust it with my M3's AGM battery, and it also has a specific mode for AGMs...
I've been using an Optima Digital 400. Charges and maintains a wide range of batteries. It's been used on three different cars. 1984 533i & 1999 M Coupe are both lead acid and a 2019 Porsche Macan S with absorbent glass mat. Very happy with it. https://www.optimabatteries.com/products/digital-400 About $90 when purchased directly from Optima. Got mine at 4 Wheel Parts for the same price.
