To add or not to add - how to calc power consumpti

[bbilly]

First thanks for the feedback - the emergency jump starter seems a good idea! Portable so I can take it on and off board to recharge, accessible to check out, sealed so I can chuck it in a locker. But how much power will I need. I investigated products on the web and there are models that fit in the "palm of your glove box" and ones on wheels! How can I calculate how much power (amps) I need available to get my Volvo TAM22D turning over to fire it up! I have a digital tester is this any good to measure power absorbed when I start my engine or is it a calculation on paper?

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[BrendanChandler]

Because I do not have space for a third battery, I use both batteries for domestic and starting. I manually watch the voltage and if they get to about 12v, I recharge them. This is hit and miss so I recently bought a Red Flash 650 at the boat show 'cause the man there persuaded me that I could easily get by with a much smaller one and that this one would be more than enough. It holds its charge for something in excess of a year, has a set of lights on the side to indicate charge and has a key to isolate the built in jump leads and so avoid shorts.
It comes with a mains and and 12v charger.

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[BrendanChandler]

Because I do not have space for a third battery, I use both batteries for domestic and starting. I manually watch the voltage and if they get to about 12v, I recharge them. This is hit and miss so I recently bought a Red Flash 650 at the boat show 'cause the man there persuaded me that I could easily get by with a much smaller one and that this one would be more than enough. It holds its charge for something in excess of a year, has a set of lights on the side to indicate charge and has a key to isolate the built in jump leads and so avoid shorts.
It comes with a mains and and 12v charger.

Brendan

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[johna]

I have recently posted this same question on <A target="_blank" HREF=http://www.yanmarhelp.com>http://www.yanmarhelp.com</A> so you can see the replies there. The answer is starter motor power divided by 12v times 2 gives the required Cold Cranking Amps. The times 2 factor is to allow for voltage reduction during cranking. For my Yanmar 2QM20 the starter is 1.3kw so requirement is of the order of 220 CCA.

I am considering adding a Red Flash battery for starting owing to reduced size and weight but lowest quote to date for smallest battery is £63 +VAT.

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[bbilly]

Brendan,
What engine would you like to start with the 650 and how much did it cost?

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[BrendanChandler]

I have a Volvo Penta M2040.

We are going liveaboard so I went for overkill.

The cost was £120 +vat delivered, very expensive but I wanted a sure backup and in fact could probably run the ship off this battery if necessary.

I bought it from Barden Batteries. See their websit for specification.
www.bardenbatteries.co.uk

Brendan

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