Elektrik: zwei Batterien im 750i - Fragen

[schneeflocke42]

hi antti,
I am no expert in electronics but when I asked the same question, my dealer gave an answer that made sense to me: because of the many additional gadgets in the 750, the 750 has two batteries being charged together, but several users - like the webasto - which could cause servere performance loss use / are connected to the smaller battery only. the switch protects that the main battery is touched at all (one way).
as the space for the batteries is very limited, I think you'd better recharge the batteries through the + and - pols at the engine (those for jump start) regularly. that will keep them in good shape...
cheers,
r.

Zitat von Christian

Heute erhielt ich nachstehende Anfrage. Vielleicht könnte sie jemand (am Besten direkt in englisch) beantworten:


Hello Christian!

I hope you are doing good. I found your contact information on 7er.com and I hope you could guide me to the right direction.

It seems my 750 iAL is not well known by local BMW dealers in Finland because I have not got a good explanation on how the batteries are connected and what they are for etc. I bought the car from BMW Niederlassung Munich two years ago. (I think it's manufactured in 09/2000 and I guess that means that it should be model year 2001....but it's missing something which should belong to BMW 750 iAL 2001 models and that missing feature is the remore control for the Webasto).

- Why two batteries? Is the smaller one for the Webasto only?

- Are they connected in parallel or are they "totally" independent on each other? The user manual says that there is a switch between them!

- (If they are independent) could I only charge the bigger one with a battery charger? Of course the question would remain how the smaller one would get charged? Perhaps by the generator when the engine is running?

Another thing is that my car is standing typically for 2...3 months at a time when I'm out of country and the batteries may become bad during that
time. I have considered to buy batteries which survive such conditions, like the ones manufactured with AGM technology (gas-recombinant absorbed glass mat). For instance, Optima is one I have thought of. However, the case may be that there are no AGM batteries which would mechanically fit into the available space (inside rear right fender)? Have you anything to say to this?

Best regards and looking forward to your advice,

Antti Suoniemi


Vielen Dank,
Chriss