Sadler 32/Red Flash/Bukh DV20

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Ross f

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Am thinking about using a Red Flash battery to start my DV20 and mounting it in the engine bay. This will make room for an additional house battery in the battery box. Not sure what size of Red Flash I need (900, 1000, 1100) to start a DV20. ATM I use an Optima Blue 55Ah with 765CCA so it looks like a Red Flash 1100 with 775CCA will be the nearest equivalent. I suspect the Red Flash 900 or 1000 may be enough to do the job but not sure? Any body use one on a DV20?
Also have read that AGM batteries don't like too high an ambient temperature and it does get hot in the engine compartment when on a windless day - anyone got an AGM beside their engine?

Thanks
 
Hi

I have a Red Flash on a DV24, pretty sure it is an 1100. Works a treat, plenty of juice even for multiple attempts at starting. Can't comment on your temperature question as ours is in the battery bank, would be surprised if it is an issue but others may know better.
 
Ross f said:
Am thinking about using a Red Flash battery to start my DV20 and mounting it in the engine bay. This will make room for an additional house battery in the battery box. Not sure what size of Red Flash I need (900, 1000, 1100) to start a DV20. ATM I use an Optima Blue 55Ah with 765CCA so it looks like a Red Flash 1100 with 775CCA will be the nearest equivalent. I suspect the Red Flash 900 or 1000 may be enough to do the job but not sure? Any body use one on a DV20?
Also have read that AGM batteries don't like too high an ambient temperature and it does get hot in the engine compartment when on a windless day - anyone got an AGM beside their engine?

Thanks
Click to expand...

Beware of the CCA ratings often quoted for Red Flash batteries

Suppliers very often quote the maximum discharge currents given in the table here:- http://www.dmstech.co.uk/red-flash/red-flash-high-rate/ as the CCA ratings. They are not!

The real CCA ratings can be found here:- http://www.dmstech.co.uk/downloads/DMS_data_redflash_highrate_web.pdf

The Red flash 1100 you mention has a max discahrge current of 775 amps but that is not the CCA which is infact only 500amps . It may be enough for your DV20 but its performance compared with your Optima battery may be disappointing, Likewise the Red Flash 1000 ( CCA 400) . The Redflash 1200 (CCA 550) will be marginally better but to come near to your Optima battery the Red Flash 1800 ( CCA 700) would be a better choice.

The red Flash 900, with a CCA of only 156, will be unsuitable.
 
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Thanks for your input you sound like you know what you are talking about. Interesting that RivalRedwing manages to start his engine multiple times with a Red Flash 1100 - suppose the determining factor is how many CCAs a Bukh DV20/24 needs.
 
Red Flash batteries have applications in some fields, such as motorsport, but it seems to me that they're incredibly expensive to use to start a small boat engine. The Bukh DV20 is just under a litre in capacity, why not look for a small diesel car battery, perhaps something like the 012 size? It wouldn't be much bigger than a Red Flash, it would do the job, and it would be less than half the price. The DV20 starter motor probably only takes around 100A.

Putting any battery in the engine compartment isn't ideal; a cooler place would be better. Couldn't you find a place for a small battery outside the engine compartment?
 
CCA is cold cranking amps.
Can be specified in at least two ways, but you probably won't want to be starting your boat engine in seriously negative temperatures.
It comes down to having plenty of margin for when the battery gets old or is not fully charged.
A medium sized motorbike battery would probably do the job, but you might need to replace it unacceptably soon.
 
Ross f said:
Thanks for your input you sound like you know what you are talking about. Interesting that RivalRedwing manages to start his engine multiple times with a Red Flash 1100 - suppose the determining factor is how many CCAs a Bukh DV20/24 needs.
Click to expand...

Trawling through a few manuals I find that the recommended battery is 88Ah. No mention of the all important CCA of course!

Typicaly an 88Ah starter battery will have a CCA rating of 700 to 800 amps. On that basis a Red Flash 1800 would be the obvious choice

IMO 700 CCA would be overkill for an engine that size, but that's only my opinion !
 
lw395 said:
CCA is cold cranking amps.
Can be specified in at least two ways, but you probably won't want to be starting your boat engine in seriously negative temperatures.
It comes down to having plenty of margin for when the battery gets old or is not fully charged.
A medium sized motorbike battery would probably do the job, but you might need to replace it unacceptably soon.
Click to expand...

The alternative, but which you rarely see quoted even if more relevant for our purposes, is the MCA rating which is based on the battery performance at 0°C rather than 0°F
 
pvb said:
Red Flash batteries have applications in some fields, such as motorsport, but it seems to me that they're incredibly expensive to use to start a small boat engine. The Bukh DV20 is just under a litre in capacity, why not look for a small diesel car battery, perhaps something like the 012 size? It wouldn't be much bigger than a Red Flash, it would do the job, and it would be less than half the price. The DV20 starter motor probably only takes around 100A.

Putting any battery in the engine compartment isn't ideal; a cooler place would be better. Couldn't you find a place for a small battery outside the engine compartment?
Click to expand...

I did that, putting a modestly-sized car battery in the adjacent locker under the head of the quarterberth. I was installing a calorifier there, too, so the additional cost of making the platform bigger was minimal, and I accepted the further loss of storage. (Of course the calorifier makes the locker a bit warmer, but certainly no worse than the engine bay I think.)
 
Yes - that locker contains all my tools, battery chargers, engine spares, junk etc so don't really want to lose any of it - just thought the engine bay has some space and is close to the starter motor so nice short cable runs. (Where I'm going to put a calorifier is for another post!)
 
pvb said:
it seems to me that they're incredibly expensive to use to start a small boat engine.
Click to expand...

They are, but one big advantage is that they can be mounted on their side, as in the photo below.
Which means the can be tucked away somewhere where no normal battery would fit.
I would agree that finding such a space onboard is probably better than putting it in the engine bay.

This Red Flash 1100 has started my 20 hp Beta722 for well over 10 years now and I have had nothing to complain about.
Although CCA is the important number, one should be aware that the capacity in Ah is small in these batteries, so perhaps not the best choice for an engine that often is difficult to start.

batteries.jpg
 
Ross f said:
Yes - that locker contains all my tools, battery chargers, engine spares, junk etc so don't really want to lose any of it - just thought the engine bay has some space and is close to the starter motor so nice short cable runs. (Where I'm going to put a calorifier is for another post!)
Click to expand...

As it did for me, excepting the charger which is and was mounted under the chart table. I chose to move very rarely-used things ashore, relocate others (e.g. I 'lost' the small cave locker forward of the chart table) and use tool rolls instead of a monolithic tool box. Regularly-used tools, engine spares, an MOB handy billy, a ditty bag and a few other odds and ends are still (accessibly) fitted around the new battery box and calorifier. I was pleasantly surprised!

But everybody has to use precious boat space differently, so good luck with your choices.
 
Another vote for a Red Flash 1100. One of the advantages of them is that unlike a simple car battery you can mount them in any orientation. The other thing is long life if you keep it charged when boat is not in use - expect a minimum of 10 years. I have a 750 in my Morgan which is a bit like a boat - used in the summer but very little in the winter. Now 15 years old and has never failed to start the 1.8 engine. Just use a trickle charger if it is not used for a while.
 
Definitely not a RF 900. I bought one after reading the erroneous figures already referred to. It would start my Yanmar 3GM30F when fully charged but not when down a bit. I replaced it with an 1100 that fits alongside the gearbox and it has been perfectly OK for several years now. I know someone who uses an 1100 to start a 4 cylinder Volvo, he keeps it lying in the bilge under the engine.
 
Thanks for all the advice/feedback much appreciated.
The favourite by a nose is the RF1100 (£190ish) as it is a proven starter of a Bukh DV24 although (being Scottish and a Fifer at that) the wee cheap car start battery is closing fast on the rail as they are available for about £40 to £50 - may be worth experimenting with . Think of all the haggis suppers I could buy with the change.......
 
Ross f said:
Thanks for all the advice/feedback much appreciated.
The favourite by a nose is the RF1100 (£190ish) as it is a proven starter of a Bukh DV24 although (being Scottish and a Fifer at that) the wee cheap car start battery is closing fast on the rail as they are available for about £40 to £50 - may be worth experimenting with . Think of all the haggis suppers I could buy with the change.......
Click to expand...

Ah, common sense is creeping in to the practical boat owner forum!
 
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