Replace all four batteries to start D-636 ?

[gordontytler]

My engines started after about 4 turns before the sea trial in February.
Now after months on hard standing with the batteries on float charge they run down after a couple of turns.

There are 4 x 110Ah batteries purchased December 2003. One is 12.7v another is 12.0 and I haven't measured the other two.

I think they are fine for domestic but not to wake up these old BMW D-636 engines from their long sleep.

Should I buy 4 new batteries or might the start with the duff ones reconnected?

What manufactures are recommended?

Should I put 2 new ones on one side for starting and use the big switch disconnect these when moored up on a river bank?

 

[gordontytler]

I meant to type "duff ones disconnected" but its fiddly on a phone. Perhaps the bad ones make a short circuit.

 

[TQA]

9 year old batteries are WELL past their best buy date.

If it were me I would buy 4 new.

 

[lw395]

You need one battery of adequate cranking amps to start the engine.
Whether the old ones are adequate for other purposes depends on what you are asking of them.
You can't depend on them for engine starting if they have been used to run lights or fridge or whatever since they were last charged.

What is the starter motor, how much current does it draw?
Get one new engine battery with a generous CCA rating, worry less about its capacity in Amp-hours.

 

[AIDY]

10 years old ! get shot of them and buy new...

i bought recently from batterymegastore.... first class service....

sold my old batts to the scrap dealer for 40p / kilo works out about £10 a battery scrap

 

[gordontytler]

Great replies. Thanks.

The starter on the D 636 is a Bosch 2.7 kW so this would be 225A at 12v.
So, a single battery would need to be about 300 CCA? I would guess that with two in parallel I could add the two cold cranking amps together.

battery-megastore have 1000 CCA batteries for £124 pounds including delivery but the guarantee is only 2 years and both terminals are on same side.

This one http://www.batterymegastore.co.uk/product/AX+595+850/ is 850 CCA for £138 and has a five year guarantee.

I think I will get one of these for starting and sell two of the old ones to the scrap dealer.

 

[lw395]

Great replies. Thanks.

The starter on the D 636 is a Bosch 2.7 kW so this would be 225A at 12v.
So, a single battery would need to be about 300 CCA? I would guess that with two in parallel I could add the two cold cranking amps together.

battery-megastore have 1000 CCA batteries for £124 pounds including delivery but the guarantee is only 2 years and both terminals are on same side.

This one http://www.batterymegastore.co.uk/product/AX+595+850/ is 850 CCA for £138 and has a five year guarantee.

I think I will get one of these for starting and sell two of the old ones to the scrap dealer.

On the right lines but the 2.7kW is possibly at a lower voltage than 12V, as CCA is usually stated at less than 2V per cell. But an 850A cold cranking battery sounds very adequate.
Doubling up batteries does not exactly double up CCA as connection resistance is very significant at these currents. It will help a bit, but one good, well charged battery with good wiring is all you need.

Your old batteries, I would charge them all up fully, then take each one in turn and see how long it takes a 10 or 20 amp load to take them down to 11.8V.
That should tell you which are the better ones, in a semi-realistic test for house use.
I use some old headlamp bulbs to do this sort of test. (make sure they are not going to melt anything!

 

[gordontytler]

My fridge will draw about 10 amps.

 

[gordontytler]

engine has started

In the end I got two Alphaline batteries from http://www.batterymegastore.co.uk/ each CCA 850 for just £153. It took two goes of cranking for 30 seconds after the fuel filter change. The engine now starts instantly.

Next job is to fix or replace the alternator.