The OP asks "What Optimizer Maintenance Thingy do I want"?
There are several products out there, but to make life easier I would like to narrow down the choices to three.
- Optimate 4 CAN bus edition
- CTEK XS 0.8
- BMWs own CAN bus charger.
CTEK:
This is the cheapest of the lot. According to descriptions it does a fine job bringing a low battery back to life. Limited desulfatoring abilities and it is made to be connected for a long periode of time with a sleep mode and 10 days between checking the battery. Does not handle the BMW aux outlet, a direct to battery cable is required.
Optime 4:
This is the most advanced charger of the lot. In addition to the regular charging cycles it has a recondition desulfator program. You may use the AUX outlet. For the desulfator procedure, the battery must be disconnected and direct connection to the battery is required, as the desulfator voltage is too high for the bikes electronics. A built in check prevents the procedure to be performed while the bike is connected.
BMWs CAN charger.
Does pretty much the same as the CTEK, but may be used through the AUX port and has a LCD display that shows status in plain language.
CTEK is the cheaper, BMWs charger is the most expensive.
CTECK is a fairly simple charger, but in order to keep the battery alive during the winter it will probably do a fine job. Hook it up and leave it on until the spring comes
The Optimate is the one with most advanced options. In order to use all of them, the "Extra" requires the battery to be disconnected.
As long as the battery is connected all the mentioned charger does the same job, more or less.
CTEK has a very basic display, but easy to understand.
Optimate have several LEDs, but may be confusing to understand. You really need to keep the manual available in order to understand it. (Or you can trust that it works and drop the manual)
BMW charger does not do more or less to the battery than the others but has a two line display that says what it's doing in plain language. It may be used either through the AUX port or direct to battery cable. It does not handle the AUX plug better or worse than the Optimate.
Usually, if there are issues by using the AUX port for charging the problem is on the bike side of the plug.
The CAN-bus ability is merely that a charger usually does a test of the battery prior to charging. If connected to the CANbus, the port is closed and as the charger senses nothing, it will not start a charge.
The CAN bus connect procedure starts by applying 12V to the plug. This will signal to the ZFE that there is a charger on line, and ZFE opens up allowing the charge to begin.
However, some of the charge cycle consists of pulsing the battery, and this may be done to a certain extent. But if the low-voltage of the cycle is too long, the ZFE close the port.
As for using the Aux plug or a direct connect cable, my choice would be a direct connect cable. Aux plug sounds tempting, but it limits the charger the ability to properly monitor the battery as the current is routed through the ZFE in the bike. If the internal GPS plug is used, the AUX port may not open up for the charger. All in all, do your self a favour and forget about the AUXport (yes I know, it is possible to make it work, but there is always the chance for it to screw up.) Also, with a direct to battery cable you may use it to hook up equipment that requires more than 5A, e.g an air pump.
