Emergency Car Battery starter on boat engine?

aquaplane said:
Why would your normal starter battery not start your engine, don't you look after it?

Look after your battery and you don't need another "just in case".

Also, a "just in case" battery needs more looking after because you never use it, so it gets forgotten.

Forget it and stick with what most folk use, domestic and engine batteries, it works or folk wouldn't do it.
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Northcave is on a long distance cruising boat.

Things go wrong.

You need to be prepared as best you can, even if it's helping your neighbor in the anchorage.

Plus -
They're great as a travel battery for phones, laptops
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Might get one meself! :cool:

 
Got one. Used it to start a diesel car and helped to start a yacht engine at 75hp. The one I got does work. Similar to one shown by Richard10002
 
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Richard10002 said:
That particular one is:

https://www.ebay.co.uk/itm/Emergency...e/262719830710

Battery Size:165 x 79 x 40 mm

Battery Weight:470g

at 68800mAh, that's nearly 70AH, which would be fine as a starter battery for regular use.

Is it possible that something so small can be 70Ah ?
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I strongly suspect this has one too many zeros!

I have quite a lot of experience of lipos from electric rc aircraft. 7ah is perfectly feasible, not 70.
 
Or its 68.8Ah at a different voltage from 12V! Standard LiPo cells are 3.7V so would be 21Ah at 12V assuming no losses.
 
davidej said:
I strongly suspect this has one too many zeros!

I have quite a lot of experience of lipos from electric rc aircraft. 7ah is perfectly feasible, not 70.
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A lot of Li batteries sold for motorbikes are sold described as 'equivalent to' so many Ah of lead acid.
For my bike I was offered a 4Ah Li battery or a 12Ah Lead-Acid.
There is some sense behind this, they have similar (or more) CCA and similar reserve cranking time.
A lithium battery's ability to crank drops off a lot less as it discharges. You can use it down to nearly flat without damage.
I went for lead-acid, as it's still a lot cheaper and that's what the regulator is designed for.
Next time around it might be different.
 
Hi Hadenough, how's France!? I think you have a generator as a backup if your batteries go down, so perhaps this makes you more confident in using a combined engine and domestic battery setup? Personally I have a pair of jump leads on board which also come in handy if the car battery has gone flat after a cruise when we get back ..........
 
Just received some lithium ion 18650 cells from China. Cell proudly claims 9800 mAH However my experiments so far using a lithium 3 cell charge/ discharge controller and 3 cells indicates I can get about 800mAH at about .9 amp rate.
Likewise a pack of 3 cells in parallel 3 in series to make 12v from 9 cells seems to give barely 2AH before the controller shuts it down with low voltage. Claimed capacity around 25AH. This in 2 different packs. So I am beginning to think the Chinese just claim any amp hour capacity that they think will sell the cells. Are US or European cells any better. That is the question. olewill
 
GHA said:
Northcave is on a long distance cruising boat.

Things go wrong. You need to be prepared as best you can, even if it's helping your neighbor in the anchorage.

Plus -

Might get one meself! :cool:

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Thanks. I almost took the cherry and replied with a comment myself but refrained. You're response was much more gentlemanly than mine would have been :)

I've read of entire battery banks being fried with a lightening strike so in lightening now I always turn the engine on and leave it running. As you say, things go wrong and it would be nice to start my genset or engine if something did occur to the batteries.
 
northcave said:
Ok so you can now buy smallish lithium batteries that output USB, 12v and high power 12v to jump start a car. They're great as a travel battery for phones, laptops and also as a car jump starter but could they start a perkins 80hp Diesel engine do you think?

The unit I recently tested on a car work perfectly and written in the side was power 600amps jump starter.

It was this one: http://www.nekteck.com/product/nekt...-van-suv-boat-smartphone-usb-device-and-more/
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From a slight knowlege of RC cars I know how impressive LiPo can be - a 12000mAh LiPo typically rated at 30C can deliver 360A - it can be run flat in a few minutes and be recharged and do that again, and again, and again. Very impressive technology for those of us brought up on Lead Acid and NiCads.

I would see no problem with a correctly-spec'd starter based on those starting a typical diesel - but no I have never seen it done.
 
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