Boosting a starter at 18v

Well, the whole world sucks and lately this forum is nothing but bad news- so I figure it's time to pose a question I've had for a couple of years.

How bad is it, really, to boost a 12 volt vehicle starter with 18 volt tool batteries? And of course the obvious question of... would they make a difference?

now, let me add some details to get the nancy no-goods off my back...

-the vehicle I'm talking about is a 70's tractor
-diesel engine- perkins, with a mechanical injection pump
-this vehicle has no working electronics- the starter motor is the only thing that gets power anymore

So, the idea. this thing sucks to start in this weather.
-new starting batteries (2 big truck batteries, wired for 12v)
-fully synthetic oil
-no grid power to run a block heater
-there is no glow plugs, but there is a cold start system that seems to function... by lighting a fire inside the intake manifold (not a joke)

all told, the engine just isn't built for this climate. once it gets cold enough, the starting crank speed just doesn't do it. I'm not using ether because I don't want to rebuild the engine if I can help it.

I've had a few ideas for ways to warm this thing up, but they're all pretty involved... but working at that site the past few years has got me thinking.
I generally have 6-8 high capacity 18v lithium tool batteries with me when I get there.
Tool batteries have an insane amount of amperage on tap.
I've seen online people jumping vehicle engines with them, although its never pretty. The good news is that these guys are doing exactly what I have in mind- cramming 18 volt batteries into a 12volt circuit and running the starter.
The bad news is that these are generally just cars or trucks that just can't quite turn over, and they just need a few seconds of crank time.

For this tractor, in the cold right now, she has to crank maybe four or five times, in 10-20 second bursts to build enough heat in the head to light off.

SO! my question to ponder.... would I have regrets if I rigged up a way to load up a few 18v tool batteries into the starter circuit just to boost that starter motor - a little bit more crank time would help, but a little faster crank speed would make a huge difference.
I just don't want to cook the starter again if I can help it. I suspect it would be just fine at 18volts, I just haven't gotten around to trying it myself yet.
Discuss- This might be the least depressing thread on ATS today

Disclaimer : I am not a certified mechanic, just a DIY mechanic with almost 40 years of working on stuff, so don't take this as Gospel.

My approach has usually been : Give it a shot. If it works, it works. If not, don't do that again. If it's 12v, 18 shouldn't really hurt it, just look out for in line fuses that may not take the load.

a reply to: lordcomac

LOL no this is a depressing thread because it takes me back to the days when I used to work in a starter and alternator shop years ago.
What you are describing would probably work but like anything else, it might be trial and error.
Anytime you over crank a starter or over heat it, it shortens the life of it.
Being this a 1970s tractor and not knowing what type of starter it is, it’s hard to say.
But it’s probably an old Prestolite or maybe an older Delco type, they were tougher than modern starters and could take more in the way of over cranking.
Although modern gear reduction type starters will crank faster, they cannot take prolonged cranking as much without burning up.
We used to sell a lot of those types of starters to the guys with higher compression engines in their hot rods.

a reply to: RazorV66

Nice to see someone with starter motor knowledge chiming in! I've replaced my fair share of these, and had a few rebuilt... but even a week doing that for a living would mean knowing far more about it than I ever will.

The problem here is that the starter likely gets overheated every time its used in below freezing weather.
Almost every time, it takes enough crank cycles to mostly drain two 900CCA batteries- it barely managed to start in those temps. Fortunately the charging circuit works well. These perkins engines were built by the english- they were never meant to see real winters.

With 3-d printers being fairly common place these days, its now pretty easy to pick up power tool style connectors- I could pretty easily pick up four of them and screw them to a board, then wire them into the starting circuit. Since the charging circuit runs at 14 volts, 18 isnt *that* far out there...

What I *can* say about the starter:
-it is NOT the higher RPM geared down style. I wanted one of these, but when I tried I got something that didn't fit.
-It says DELCO on it, but when I had it rebuilt the guy said it was a LUCAS
-Note I took at the time says "type m127(2.8)" - is that 2.8KW?
-p/n 3763362m94 (from the book)

its an older style unit, with older values- built to take a beating, but I suspect a newer geared down unit would be a better fit for this climate.

a reply to: lordcomac

I don't think you can do any damage with this method but I also don't think it will work.

You would be better off buying a small generator.
I don't know how handy you are but years ago I built a generator from a 4 hp gas engine 'lawn mower"and an alternator.
It worked great for charging an electric fence battery.

Don't forget to take the mechanical load into consideration. The gears on the flywheel and the starter will be stressed more by doing this and fail sooner. While you are only increasing the voltage to 150% of the motor rating, the shaft power output increases to 225% of the motor rating.

It might be worth a try but the gears might not be able to take the extra torque.

I'm just a Canadian redneck.....so just backyard guy here...

I'd give it a go.....the system can take a higher voltage while charging...so why not?

A couple volts over shouldn't hurt nothing.....

Eta: you could also get a cheap voltage regulator to dial the voltage back a bit...

a reply to: Bluntone22


the "will it work?" portion is my favorite.
I'm quite handy- I've looked extensively at building a DC generator, but it turns out alternators are terrible generators. they're just not made for the duty cycle that something like this would need. For a few hundred bucks there are places that sell re-wound chevy alternators designed for this kind of duty cycle, they're built to run wind turbines or gas generators to recharge battery banks.

I did wind up buying a small/cheap 1kw generator that HAS a "12 volt" DC generator (8amp) port last spring, figuring I could bolt it to the tractor and use it to run some 110v heating pads for the oil, and the block heater, while charging up the batteries for a cold start... but this doesn't change the root problem of the starter just not cranking fast enough.
I've yet to get around to attaching it to the tractor, this year has just been too busy.

a reply to: lordcomac

Ask Flyingclaydisc, member. He knows if anyone does.

PM him

originally posted by: lordcomac
a reply to: RazorV66

Nice to see someone with starter motor knowledge chiming in! I've replaced my fair share of these, and had a few rebuilt... but even a week doing that for a living would mean knowing far more about it than I ever will.

The problem here is that the starter likely gets overheated every time its used in below freezing weather.
Almost every time, it takes enough crank cycles to mostly drain two 900CCA batteries- it barely managed to start in those temps. Fortunately the charging circuit works well. These perkins engines were built by the english- they were never meant to see real winters.

With 3-d printers being fairly common place these days, its now pretty easy to pick up power tool style connectors- I could pretty easily pick up four of them and screw them to a board, then wire them into the starting circuit. Since the charging circuit runs at 14 volts, 18 isnt *that* far out there...

What I *can* say about the starter:
-it is NOT the higher RPM geared down style. I wanted one of these, but when I tried I got something that didn't fit.
-It says DELCO on it, but when I had it rebuilt the guy said it was a LUCAS
-Note I took at the time says "type m127(2.8)" - is that 2.8KW?
-p/n 3763362m94 (from the book)

its an older style unit, with older values- built to take a beating, but I suspect a newer geared down unit would be a better fit for this climate.

Yeah ok...those old Lucas starters were not a very good starter design wise but they were built like a tank.
Very heavy duty armature and field windings which are the parts that will suffer the most from over cranking.
The downside with that starter is it is a slow cranking unit with normal 12 volts.
I think you will be ok with what you are trying to do but again, it will most likely be a trial and error thing.

Edit - Yes the 2.8 on the starter does mean 2.8Kw


Edit - I don’t know what it cost you to get it rebuilt, the prices most likely vary wildly in different parts of the country but here is a website that would have a good option on a new aftermarket replacement if you needed one....probably in around $100-125

www.dbelectrical.com...

That's gonna wear your starter solenoid out fast. Cold does two things, kills your batteries power, and makes the oil thicker.

So I would bring your battery in at night and find a way to warm your oil. You can get solar powered blanket heaters to wrap around the oil pan.

JUst a thought as thats what I did to my truck up in Montana.

My jump pack is full at sixteen volts, it can be charged up to eighteen volts, when you engage the starter, the voltage goes down. As long as you do not have a lot of electronics on a car or vehicle, the voltage is not really a problem. My big battery charger has a start function, that jumps at about sixteen volts, but the battery of the car is a buffer, so it averages about fourteen volts when the starter is engaged, not really a problem. Over eighteen volts can be a problem for new cars though, remember that. If the regulator sticks, it can cause over eighteen volts, that can burn out diodes and electronics if it is constantly used. Had that with a Honda CRV.

One thing to check is the gauge of the wires connecting it all up. If they start to get too hot then put in some thicker wire.

a reply to: lordcomac

Using 50% more voltage won't really do much to harm a large non-electronic item like that. The main concern would be the glow-plugs and if they have their own voltage regulation system, which they should, but it is possible that the voltage is too much for the regulator to handle.

Beyond that issue, is that 18v lion batteris have terrible discharge rates. A 3 Ah battery might only put out 100W of power, where a 12v car battery will have something in the range of several to dozens MW of power.

I would say the problem is the motor doesn't have glow plugs. Is there a way to add them? Otherwise you'll need a heated garage. Or an ether start. Otherwise relocate it to where you can plug a block heater into the mains.

I have a feeling though you're going to need a 30 amp circuit for a serious block heater though. A 15 amp house outlet may not be enough.

Connecting the 18v power tool battery to the Car battery will help charge it up, it is well within limits for a recharge cycle. About 14.4 - 14.8v is a good standard charge for a healthy car battery. 21v is starting to over charge a standard car battery, it will still work ok, starting to put the battery into more stress and affect expected life expectancy.

It will help lift the overall voltage reaching the starter motor. These are the thickest wires going from the battery, rated to around 200 Amps on average, At a guess, you might be getting 15-16v at the starter motor. Get your self a multimeter is a great way to learn what is going on.

a reply to: lordcomac

My father was in construction so I grew up around construction equip., first option is to install a water heater if you have 110V nearby or the old fashion way, make a small fire under the engine to warm it up and make sure engine is clean and no oil leaks otherwise you know what, then use starting fluid when cranking.

When getting to what is going on with electricity, Ohms Law and the relationships between Volts, Amps and Resistance is a good start.

My main concern would be with the batteries themselves.

Assuming these are 18v lithium-ion? MIGHT work in a pinch, but these are fickle things that don't like abuse (much less an effective dead short put on them regularly). Best case is it works, middling case is the batteries have short lives, and of course worst case is they ignite. A booster pack designed for this is cheaper than unplanned fireworks...

The tractor will be no problem, old school with no electronics and everything way overbuilt. Back in the day we had a similar machine also with a Perkins, and if the temp was literally under 50F it needed starting fluid. Not a lot, just a fraction-second "sniff" while turning it over.

If you want to avoid starting fluid/ether, try carb cleaner. Not as destructive, and if the motor just needs a little help the cleaner might be good enough. Be careful not to soak the air cleaner element.

Don't know how cold of weather you'll need to be working in, but if it's single digits F or colder, you'll really want to get the block heater going somehow.

he vehicle I'm talking about is a 70's tractor

tent it with a tarp and put a small Coleman camp stove on the ground below it.
that will warm the engine and battery enough to start it.

I had an old 6 volt VW bug that I converted to 12 volts.
The only thing i did not change was the starter, i left the 6 volt starter and ran 12 volts to it
ran it like that for years, and it sounded like spinning up a turbine but started fine even in cold weather
many people used to do this with old 6 volt cars.