This may sound daft - but its a serious problem ... two 20Ah Lawn Tractor batterys

Refueler

Refueler

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I have Superanne sitting there luckily weather has warmed up a touch ... but she has no batterys on board and auto-bilge pump cannot keep her dry.

We have rain over last few days and more to come. I am thinking about taking the lead acids out of my two lawn tractors, Jonsered LT2113 and LT2114 and fitting in SA to provide power for the bilge pump ... this I know is fine as my Progress motorboat has same pump and only a 7Ah SLA with 5W solar panel.

The question is .... would 2 x 20Ah lawn tractor batterys be able to start the Perkins 4-107 from cold ?? She's not too bad with a shot of easystart up the chuff ... worry is the load may buckle the plates and I'm then left with no batterys.

I'm thinking its better to put them into the boat ... usually the batterys stay on the tractors and handyman is supposed to check charge through winter to avoid them freezing / damaged ... but each winter I lose at least one.
Putting on SA - I have a Maplins auto-detect charge splitter and small 4A charger can be on a timer to keep them topped up.

It led me to wonder if they would actually start the engine to let me run Anti-Freeze through ...

I don't want to pay out for a new bank of batterys and leave them in for winter ...
 
ghostlymoron said:
The ability to start your engine depends on the cold cranking rating not the ahr. The amp hours used to start an engine is tiny.
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True, but the CCA and the Ah are both tied to the size of the battery.
If the small batteries are in good nick, and not too cold, they will probably deliver enough current.
Best if you can parallel the two.
 
RichardS said:
Can't you just carry the battery over from your car and use that to start the engine with jump leads?

Richard
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If you remove battery from either of my cars ... the radios etc. all lose codes ... and the boat is in the channel afloat ... I've tried leads before - but the length is just too long ... I cannot get car close enough.

I thought about swapping one of the car batterys for a LT one ... but I would need to bridge the old battery with new to do it ... not a good idea with two significantly different batterys .... to stop losing the codes etc.

For years I have used 2nd hand batterys from breakers yards ... had fantastic use out of them ... just because they are 2nds .. doesn't mean they are dud.

I've had them last 5 or more years on board ... even though they are standard car starter jobbies. Trouble is with Eu rules and such ... all the sellers in my town have stopped ... they now only take in for disposal.
 
Refueler said:
If you remove battery from either of my cars ... the radios etc. all lose codes ... and the boat is in the channel afloat ... I've tried leads before - but the length is just too long ... I cannot get car close enough.

I thought about swapping one of the car batterys for a LT one ... but I would need to bridge the old battery with new to do it ... not a good idea with two significantly different batterys .... to stop losing the codes etc.
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Don't worry about bridging 12V batteries in parallel whilst you remove the main battery. I do this several times a year on modern cars to preserve the ECU/radio/security settings etc. It's how the dealers do it. You only need a tiny battery to keep the systems alive. Probably a 12V dry cell would do although I've never actually tried that. :)

Richard
 
ts blo**y awful out there .. storm winds and cold ... so I will be inside for a while thinking this through !!

Thanks ... I know I've seen dealers use an emergency start pack ....

I have to admit - I hate carrying a 100Ah battery along the side deck of the boat ... that's after climbing on board ! My boat is moored bows to the BBQ pontoon .... its times like this - you wish you had Baltic style pulpit ... they have their pulpits split into two so - centre you can step through. All based on their common bows to moorings and tieing up to trees !!
 
Surely it's better to stop water getting into the bilge in the first place rather than concentrating on removing it afterwards? (And it saves having to hump batteries around!)
 
Thistle said:
Surely it's better to stop water getting into the bilge in the first place rather than concentrating on removing it afterwards? (And it saves having to hump batteries around!)
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I agree with you .... but its an old 1970's boat that water creeps in under the cockpit hatch ... drips through the stern seal .... condensation collects ...

I am sure there are many others who have an older boat that no matter what you do - you can never stop water collecting in the bilge. You do all you can - then solve the residual problem.

But the real question is not the bilge pump ..... not bothered about that at all ... Its whether those two small Lead Acids together can turn a 4-107 diesel over to start ... its 43HP.
 
Refueler said:
Its whether those two small Lead Acids together can turn a 4-107 diesel over to start ... its 43HP.
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Without knowing the CCA of the small batteries, it's difficult to know .... but my suspicion would be that, unless the engine is already warm or it's in a warm location, one battery would struggle whereas both, in parallel, might stand a chance if they are fully charged.

You could try as you will know within a second whether the batteries can spin the engine. If they can't, then stop immediately before any heat is generated and the batteries will be fine. It's only going to damage them if you force them to struggle on against an impossible load. :(

Richard
 
I think it is unlikely that 40Ah would start that engine - would probably struggle on CCA let alone capacity especially if not fully charged or not it tip-top condition.

One option is to get one of the new-style jump-start power packs and take that down to the boat when you go. I don't have one but everyone swears by them these days
 
I bought a Red Flash 900 AGM because I believed the CCA figure given by Tayna. In fact this was incorrect and the battery was not up to starting my Yanmar 3GM30F when slightly discharged, although it was fine fully charged. This battery has an Ah figure of only 13. So I think there is a very good chance that your 2 x 20 Ah batteries fully charged will do it.
 
A 16 Ah battery starts my bike. That involves pushing a 94mm piston against 11:1 compression.
A diesel will have less than twice the compression and probably less than half the piston area.
CCA of the battery is nominally 200A or so. So a new one of those at sensible temperature will crank a 1.5kW starter motor very happily for a short while.

In practice such batteries get mistreated and often don't start anything at all after a couple of years.
 
Why not bite the bullet now and buy the battery you really want. Your only problem then ( assuming you want to leave it aboard) is ensure it doesnt go flat over winter. Even a small solar panel would keep it topped up. ( Or a bigger one if you have concerns about keeping your bilges pumped out)
 
You say the rain gets in through the cockpit hatch. Until you can cure that why not cover up the cockpit with a tarpaulin?

It will also keep leaves and birdshit out, and protect any varnish work.
 
Poignard said:
You say the rain gets in through the cockpit hatch. Until you can cure that why not cover up the cockpit with a tarpaulin?

It will also keep leaves and birdshit out, and protect any varnish work.
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I used to cover .... and it needs to go under the boom so the tarp sags in the middle ... I rigged wood battens ... ropes ... but if you see how much snow we can have here ???? I'm talking a lot of kg's !! and the cold causes the tarps to crack.

Honest - I'm not bothered about the bilge ... its a tiny problem and well under control.

LT battery (one) is now on board ... ran for about 20 secs ... all dry ... charger is set via timer and auto detector for 4hrs charge each monday ... she'll do nicely till I get a proper start battery to run the engine.... which is the main reason about the post.
 
pcatterall said:
Why not bite the bullet now and buy the battery you really want. Your only problem then ( assuming you want to leave it aboard) is ensure it doesnt go flat over winter. Even a small solar panel would keep it topped up. ( Or a bigger one if you have concerns about keeping your bilges pumped out)
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That would be the sensible thing to do ... but having already lost a couple of batterys due to the winters here ... I want to wait till spring to buy new. If I can get her through winter on 'crap' ... then I'm a happy boater !
 
lw395 said:
A 16 Ah battery starts my bike. That involves pushing a 94mm piston against 11:1 compression.
A diesel will have less than twice the compression and probably less than half the piston area.
CCA of the battery is nominally 200A or so. So a new one of those at sensible temperature will crank a 1.5kW starter motor very happily for a short while.

In practice such batteries get mistreated and often don't start anything at all after a couple of years.
Click to expand...

Dunno ... she's a 43HP 4-107 .... basically a London Taxi engine ...

There wouldn't be a problem if motors like this still had starter handles ! The alternator will not be energised so won't care about no battery ... its only if you disconnect when alternators outputting that diodes etc. blow.

I put one battery in ... and I'll wait a bit ... pumps catered for now. We have weather forecast of + temps for rest of week.

Once my moneys released from arrest in Canada and I can draw on it again ... I'll fix everything.
 
Not starting an argument ... just curious ...

I was told years ago that a diesel engine usually has far greater compression than a gasoline engine and is part of the reason they are heavier and stronger blocks / heads.

I must drag out my Perky manual have a look at the specs ...

Perkins 4-107 and 4-108 compression ratio : 22:1 ..... with 4 pistons of 79.4mm (page 17 Perkins Workshop Manual).

I think maybe those two LT batterys are going to have a hard time with that !
 
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