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Old 10-01-2020, 12:01   #16
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Re: Volvo MD30 Starter: real current use

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Originally Posted by john61ct View Post
The peak transient current you "measure" is completely dependent on the instrument. Most ammeters won't see at enough resolution, need a $300 Fluke, or really an oscilloscope for accuracy.

And in fact even with a very precise current number, no one is going to know

how much voltage sag a bank composed of **those** cells will exhibit, or

what the wear & tear factor will be of such a transient C-rate

without IRL testing.

You being a pioneer, you get the arrows 8-)

yes I am a pioneer in this.


But getting the amps of a starter to seize the battery you don't need fancy and precise measurement and tools.
its good enough to know if you crank for 5seks and see the approx current. is it 150 or 200 or 250A what you see and this you take as baseline to choose the battery. Thats how it was done over the last decades.

Also a very good indication is the size of the starter battery used before without problems. In this case a 140AH AGM.
So this 40AH LTO should be easly doing it, it outperformances a 140AH AGM under any condition and temperature.
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Old 10-01-2020, 12:05   #17
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Re: Volvo MD30 Starter: real current use

Yes I already said, afaict you should be fine.

But you won't know for sure until you test it.

Amps at the ms level are nothing like a long period like 5sec.

The issue might be, NP at all with amps, in warm weather healthy engine

but long cranking in cold temps, you run out of ooomph with only 40Ah, where 60, or 80 would be fine. . .
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Old 10-01-2020, 12:09   #18
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Re: Volvo MD30 Starter: real current use

In case of doubt about the safely available current capacity of your LTO set-up you could parallel it with a super capacitor bank.The capacitor bank will take care of any high amps while the battery supplies the back-up load to recharge the caps after every start attempt.
Some people extend the service life of their car starting battery that way.

Search youtube for ideas and applications.
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Old 10-01-2020, 12:37   #19
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Re: Volvo MD30 Starter: real current use

The starting current is not easy to define.

Below is a graph posted by Blue Seas showing the start current of a diesel (size not defined). You can see the current spikes above 1000A for a very short period of time but the draw averaged over a second or so might be only 250A. The timescale is important.
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Old 10-01-2020, 12:47   #20
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Re: Volvo MD30 Starter: real current use

Good quality analog ammeter [Simpson Electric model] with the correct shunt is the measurement tool if you want repeatable accuracy and total voltage independence. Since a shunt is in series with the starter you have to use good quality cables and connectors when making the connections.
A 7.5 liter gas boat engine in a 12 V system draws about 250A for 5 seconds then tapers to about 200A. I believe an 8.3 ltr Cummins diesel in a 24V system is about the same.
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Old 10-01-2020, 12:58   #21
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Re: Volvo MD30 Starter: real current use

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Originally Posted by Boatyarddog View Post
Sure you can.
Get one of these.Or borrow one.
Clamp it on you'll get real time actual current use of what it is your measuring.
I'd go for a Fluke 323, more functions.
But, here's Harbor Freight
https://www.harborfreight.com/digita...SABEgKPIvD_BwE.
Cheers,
SV Cloud Duster
that's great if you have an AC powered starter... but most folks use DC and that meter is AC only.

And such instruments don't do well measuring rapid transients as others have pointed out.

Too bad.

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Old 10-01-2020, 14:17   #22
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Re: Volvo MD30 Starter: real current use

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Originally Posted by CaptainRivet View Post
HI all,


could anyone please tell me how much ampere the Volvo penta MD 30 starter uses in reality?


Its rated at 3kw so 3000W with 12V so 250A but how much is it in reality?
Boat is 3000km away so I cannot measure it myself.
Thank you
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Originally Posted by Boatyarddog View Post
Sure you can.
Get one of these.Or borrow one.
Clamp it on you'll get real time actual current use of what it is your measuring.
.............
Gonna need long arms or long leads as well...
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Old 10-01-2020, 19:08   #23
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Re: Volvo MD30 Starter: real current use

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Originally Posted by noelex 77 View Post
The starting current is not easy to define.

Below is a graph posted by Blue Seas showing the start current of a diesel (size not defined). You can see the current spikes above 1000A for a very short period of time but the draw averaged over a second or so might be only 250A. The timescale is important.

thanks. looks like a starter in the range of 3 to 4,5kw and expected a startup spike of around 4 times the spec so 1000A spike is spot on...just imagine the stress for a 200AH FLA with its high internal resistance to cope with this 1000A spike, no wonder they make 500 cycles and die...


figured more data: a config of 6 40AH LTO cells can deliver/is rated 1749CCA, so the short 1000A spike it can easily handle. Also 800A continous for 4 seconds and continous 400A over 3min straight is piece of cake for it. What a 40AH monster...

and up to 5C charge=200A is recommended for 40AH battery, 400A possible so battery will recharged soon if engine runs and alternators work.

So yes I am confident it will definitly handle the 3kw starter of my boat, also cranking it 50 times in a row.

Will go for it, just need to find a supplier/seller of these cells that deliver real 40AH ones and not rebatched 30AH.
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Old 10-01-2020, 20:36   #24
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Re: Volvo MD30 Starter: real current use

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thanks. looks like a starter in the range of 3 to 4,5kw and expected a startup spike of around 4 times the spec so 1000A spike is spot on...just imagine the stress for a 200AH FLA with its high internal resistance to cope with this 1000A spike, no wonder they make 500 cycles and die...
Does anybody else find this the most outrageous statement that is just false on its face? An FLA in starter service--even a large diesel--is good for WAY WAY WAY more than 500 starts... If you aren't getting seven to ten years out of s standard starter battery you are doing something really, really wrong.

Our boat did TWO ten year circumnavigations and is only on its third start battery of 100% standard tech that can be found ANYWHERE in the world for dirt cheap.

Odds are the latest high tech super duper exotic battery is not going to be any better for you if you can't keep a FLA alive.
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Old 11-01-2020, 05:58   #25
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Re: Volvo MD30 Starter: real current use

Probably crossing wires from discussions about deep cycling use cases.

Completely agree about the impracticality vs knowledge / skillset level aspect.

But as long as safety is covered, reliability can be added with redundancy.

IOW bring along the science experiment once proven on shore, even try using it day to day

but have a backup / reserve lead bank standing by for when the sea gets nasty winds howling, you're drifting toward a lee shore, is exactly when the engine will have trouble starting and something fails in the LTO pack.
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