Want to build a vintage deisel battery charger

I'm thinking about getting hold of a small stationary diesel engine like a little Lister or Petter cement mixer engine, to drive a 12v car
alternator, this will be a low cost battery charger for a boat ....... now , how can i match the right size engine to the right amps alternator ? What will run what in practice ? Has anyone tried this? I might close couple the alt to avoid belt drive power losses.
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On 2 Feb 2005 09:11:16 -0800, Rich. wrote:

1hp is approx 750W. 750W is 62A @ 12v (ish). How big a battery charger where you thinking of?

Modern car type alternators fairly whizz round compared to a little old diesel plodder... You might need the belt drive to gear up the engine speed.
--
Cheers snipped-for-privacy@howhill.com
Dave. pam is missing e-mail
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Modern alternators develop peak output at about 15,000 rpm and don't charge much below about 3000 rpm. Unless you have a particularly high speed engine, you can't close couple them. The calculated output wattage has to be divided by the efficiency to get the input power. When I did this exercise using a 2 1/2 HP engine, the thing stalled dead as soon as I tried charging a battery. Assume an efficiency of about 0.25 for a start. There are various ways of reducing the output of an alternator but the easiest is to run it slower. Don't forget that alternators don't self excite. That means that they will not charge a completely flat battery as they need to draw a small current to provide initial field excitation. If you get a modern alternator, you will also have to decide where to connect the sense terminal. Again the easiest is to connect it to the output at the alternator so converting it to machine sensing. It's not as good on a car but will do if you're charging a battery off load. Finally, a lot of alternators don't appreciate running open circuit, i.e. without being connected to a battery. It is a good idea to leave a small gel cell across the output to protect the electronics. A large capacitor may also work.
John
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Sure, i'd have to put 3:1 gears on it, a car alternator cuts in at over 3000rpm, i just have a thing about v-belts at the moment after getting my overalls caught in a 30hp deisel,and loosing my trouser leg ! I'll want to drive a standard car alt 50/60 amps, because these are 10 quid from the breakers, or no quid if you are quick on a dumped vehicle.
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On 2 Feb 2005 09:11:16 -0800, snipped-for-privacy@hotmail.com (Rich.) wrote:

I built a little set 20 years ago with an 11AC alternator on a Petter AA1, even with a faily high rpm engine like that you still need a belt drive to get proper charging speed for a vehicle alternator. It was noisy. I'm sure it would have run a bigger alternator than that without bother. If you want to close couple it, maybe an old commercial or marine dynamo would be worth looking out for.
HTH Tim
Dutton Dry-Dock Traditional & Modern canal craft repairs Vintage diesel engine service
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The Petter A series (AA1, AC1. AA1 is smaller in power output and cylinder bore to the AC. The AC1 has had some modifications over time. Earlier engines have the injector in the side of the head, hidden inside the air ducting. Later ones have the injector in the top of the head and the ducting is cut out around it. The AC1 is current production by Lister Petter!) are small engines, mainly made of aluminium, and are more portable than the Lister singles (LD1, SL1, LR1, SR1, ST1. All the Listers look identical on the outside (Except for the rocker covers on the ST1!). The LD1 is the smallest in power, the ST is the larger. The cylinder bore and RPM increase down the range.). These Listers are quite(!) heavy, and much taller than the Petters. All will drive an alternator, but watch out for the RPM on the fixed speed engines. These are not all the same, and some mixers run at quite low RPM, which means putting a larger pulley on the engine, leading to a longer belt being required.
We have a Lister LR1 (Ex Mixer) which is about 3 HP at 1000 RPM (If I remember right!). It has a pulley directly attatched to the flywheel of about 12" or so diameter. It drives a standard Lucas alternator OK. It is not too noisy, just the same as a Mixer in fact, a bit clanky. The charge light circuit is powered from the positive feed to/from the battery being charged, the light and a swich being mounted on the engine. We used welding cable to take the charge to the boat battery to minimise voltage drop.
We have now come up with a new system. The alternator charges a battery mounted on/by the engine, this battery powers an invertor (600 Watt in this case). This feeds into a mains extension cable to the boat, where it runs the 240V circuit, and a battery charger to charge the boats battery.
I hope the above helps....
Regards
Sarah
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Hi Sarah, If you use the battery sense configuration, voltage drop is compensated for by the alternator. Basically there are 3 terminals on a Lucas alternator. I'm assuming one of the ACR series since that's what I have messed with. The battery (+) and indicator terminals are obvious as is the case to earth (-). The S terminal is a sense connection. The electronics try to maintain this at 14.2 volts, i.e. charging voltage. If you connect this terminal directly to the battery, you eliminate the voltage drop in the (+) lead. With a bit of fiddling, you should be able to make the (-) side remote sensing as well.
John
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Now were cooking !! just one little thing Sarah, what amp rating is your alternator ? have a nice day. Rich.
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Hi...
Our Alternators are all "used". One is a 90 Amp from a Volvo 940. One is unknown, probably about the same. We did use a Lucas one, probably around 35-60 Amp.
Never had an alternator with more than two terminals...+ feed and field coils.
I do however understand the reference to "Battery sensing". Some of them "Charge Management" thingys are meant to convert the Alternator to Battery Sensing...
HTH
Regards
Sarah
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I used to have an AB1 on the boat diving an alternator just for charging. Sold it to Kim and replaced it with a 5kva 230v genny and battery charger. I had to get the engine started and warm before I connected the field wire on the alternator and even then it struggled for a few seconds......
--

Julian Tether
Barge Parglena
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I was going to say that too .......
Still works just fine, but you are right, it does struggle to start with & I wonder if that isn't the governor struggling to deal with a sudden load, the compression failing slowly or the design of the engine being more designed for a steady-applied load.
Noisy too. It's the only engine my neighbours complain about!
Regards,
Kim Siddorn
"Spring in the air?" "Spring in the air yerself !"

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Sorry, Rich, did you mean me? Petter AA - or AB - output? Not sure, really, I just fire it up and connect it to the battery! Should I see if I can find a tag on it? - though Julian will probably know ........
Regards,
Kim Siddorn
"Rich." wrote>

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