DC to DC Charger Configuration

[steve.sharratt]

I have just swapped out my 12v alternator (to starter battery) for a 24v Alternator (to leisure batteries).  My starter battery is LA and the leisure are LiPo4.  All is working well but now I have no charging system to my starter battery.  My plan is to add a DC to DC charger and as I already have Victron components, I am looking at the Orion TR 24/12 but the wiring diagram shows it working in conjunction with the alternator.  In my case I just need a simple battery to battery connection (i.e - and + from leisure to Orion input and output to starter - and +).   Seems logical but I thought I would check.

 

Note: Sometime in the future I will look at reinstalling the starter alternator (and have dual alternators) but I have a vintage engine and this will require some engineering.

[nicknorman]

28 minutes ago, steve.sharratt said:

I have just swapped out my 12v alternator (to starter battery) for a 24v Alternator (to leisure batteries).  My starter battery is LA and the leisure are LiPo4.  All is working well but now I have no charging system to my starter battery.  My plan is to add a DC to DC charger and as I already have Victron components, I am looking at the Orion TR 24/12 but the wiring diagram shows it working in conjunction with the alternator.  In my case I just need a simple battery to battery connection (i.e - and + from leisure to Orion input and output to starter - and +).   Seems logical but I thought I would check.

 

Note: Sometime in the future I will look at reinstalling the starter alternator (and have dual alternators) but I have a vintage engine and this will require some engineering.

As far as I can tell, the Orion tr 24/12 is not designed to charge a battery. It is designed to produce a 12v supply to run 12v equipment from a 24v supply. As such there is no bulk/absorb/float “smart charger” functions, it just outputs a fixed voltage. Which is not really what you want.

I think Sterling do a B2B that is a 24v to 12v charger. Or another solution, if you have an inverter, is to use a small mains 12v battery charger. It doesn’t take much out of a battery to start an engine, so it shouldn’t take long to recharge.

[magnetman]

What about using a little converter 24v to 13.8v to just float the starter battery. 

 

this one is 10 amps..

https://www.ebay.co.uk/itm/175628566277

 

£16 (china)

 

Maybe it would burn out I don't know but it might work. 

 

40 amp

 

https://www.ebay.co.uk/itm/115698245522

 

£26.50 (china)

Edited March 8, 2023 by magnetman

[Eeyore]

2 hours ago, nicknorman said:

As far as I can tell, the Orion tr 24/12 is not designed to charge a battery. It is designed to produce a 12v supply to run 12v equipment from a 24v supply. As such there is no bulk/absorb/float “smart charger” functions, it just outputs a fixed voltage. Which is not really what you want.

I think Sterling do a B2B that is a 24v to 12v charger. Or another solution, if you have an inverter, is to use a small mains 12v battery charger. It doesn’t take much out of a battery to start an engine, so it shouldn’t take long to recharge.

They do a charger version https://www.victronenergy.com/dc-dc-converters/orion-tr-smart

[steve.sharratt]

9 minutes ago, Eeyore said:

They do a charger version https://www.victronenergy.com/dc-dc-converters/orion-tr-smart

 

2 hours ago, nicknorman said:

As far as I can tell, the Orion tr 24/12 is not designed to charge a battery. It is designed to produce a 12v supply to run 12v equipment from a 24v supply. As such there is no bulk/absorb/float “smart charger” functions, it just outputs a fixed voltage. Which is not really what you want.

I think Sterling do a B2B that is a 24v to 12v charger. Or another solution, if you have an inverter, is to use a small mains 12v battery charger. It doesn’t take much out of a battery to start an engine, so it shouldn’t take long to recharge.

I’m definitely looking at the charger version. I double checked as the converter and charger versions look similar (and the charger is more expensive of course!!) 

I looked at the Sterling but very expensive and I am considering a 240v charger but want to leave it running constantly.

2 hours ago, magnetman said:

What about using a little converter 24v to 13.8v to just float the starter battery. 

 

this one is 10 amps..

https://www.ebay.co.uk/itm/175628566277

 

£16 (china)

 

Maybe it would burn out I don't know but it might work. 

 

40 amp

 

https://www.ebay.co.uk/itm/115698245522

 

£26.50 (china)

I have considered this and do use the units in the links provided but I am really nervous about running cheap Chinese stuff continuously (and unattended).  I have a 240v charger that I have also considered using but I look at the cheap build quality and just see a fire waiting to happen.   My engine is a JP3 which can take a bit of oomph to get going and I am home moored on the Thames which can mean engine off in locks.  Short story is I need to be sure that the charge is fast enough to keep up with demand.  I may be overthinking it…

[MtB]

1 hour ago, steve.sharratt said:

 

I’m definitely looking at the charger version. I double checked as the converter and charger versions look similar (and the charger is more expensive of course!!) 

I looked at the Sterling but very expensive and I am considering a 240v charger but want to leave it running constantly.

I have considered this and do use the units in the links provided but I am really nervous about running cheap Chinese stuff continuously (and unattended).  I have a 240v charger that I have also considered using but I look at the cheap build quality and just see a fire waiting to happen.   My engine is a JP3 which can take a bit of oomph to get going and I am home moored on the Thames which can mean engine off in locks.  Short story is I need to be sure that the charge is fast enough to keep up with demand.  I may be overthinking it…

 

 

I'd have thought with a JP3 the work the starter motor and battery does starting in Thames locks is still pretty light. Does it not re-start on pretty much the first compression stroke when hot? 

 

If not, using the decompressors greatly reduces starter motor energy.

 

You could experiment on your mooring stopping the engine then re-starting it over and over again to get a feel for how many starts the battery will deliver without any re-charging. I bet it is well into the hundreds of re-starts.

 

 

 

Edited March 8, 2023 by MtB

[steve.sharratt]

9 hours ago, MtB said:

 

 

I'd have thought with a JP3 the work the starter motor and battery does starting in Thames locks is still pretty light. Does it not re-start on pretty much the first compression stroke when hot? 

 

If not, using the decompressors greatly reduces starter motor energy.

 

You could experiment on your mooring stopping the engine then re-starting it over and over again to get a feel for how many starts the battery will deliver without any re-charging. I bet it is well into the hundreds of re-starts.

 

 

 

You are probably right.  She will start without decompression when hot but it can be harsh on the starter motor gear (I’ve seen brass/bronze? Flakes shear off as it hits the compression stroke) so I generally will use decompression to get her spinning.  I might run a test, as you suggest, as I suspect my existing battery might be near end-of-life.  

 

[steve.sharratt]

9 hours ago, MtB said:

 

 

I'd have thought with a JP3 the work the starter motor and battery does starting in Thames locks is still pretty light. Does it not re-start on pretty much the first compression stroke when hot? 

 

If not, using the decompressors greatly reduces starter motor energy.

 

You could experiment on your mooring stopping the engine then re-starting it over and over again to get a feel for how many starts the battery will deliver without any re-charging. I bet it is well into the hundreds of re-starts.

 

 

 

You are probably right.  She will start without decompression when hot but it can be harsh on the starter motor gear (I’ve seen brass/bronze? Flakes shear off as it hits the compression stroke) so I generally will use decompression to get her spinning.  I might run a test, as you suggest, as I suspect my existing battery might be near end-of-life.  

 

[magnetman]

I've seen JP3 engines started with dynastarts rather than gear starter motors.

[steve.sharratt]

1 hour ago, magnetman said:

I've seen JP3 engines started with dynastarts rather than gear starter motors.

Now you are just giving me reasons to spend more money 💰😁. 

[magnetman]

A dynastart with its own dedicated Lithium (LTO) battery would be interesting. They have significant power output capability and will go up to 16.8v. Charging at 14.8v would around 75% and the oomph you get is amazing.

 

I'm a big fan of LTO batteries. The ones I have came from the same gentleman who built your boat but I don't think he has any left.

 

 

[steve.sharratt]

4 minutes ago, magnetman said:

A dynastart with its own dedicated Lithium (LTO) battery would be interesting. They have significant power output capability and will go up to 16.8v. Charging at 14.8v would around 75% and the oomph you get is amazing.

 

I'm a big fan of LTO batteries. The ones I have came from the same gentleman who built your boat but I don't think he has any left.

 

 

I bought my lithium from him as part of the boat purchase.  I’m running 24v for the house bank and have just fitted a 140amp Balmar and regulator.  My problem is the engine speed is not fast enough to spin the alternator to optimal revs - its charging but no where near capacity. First test was yesterday but the batteries are at 100% so not sure how much that influenced the output.  Currently letting the batteries run down a bit before I test again. I have fitted it to the original mount/engine pulley for this season (to benefit from the existing set up).  I plan to get an engineer to redesign the mounts and have the flywheel grooved for a serpentine belt as the flywheel has a considerably larger diameter.

[magnetman]

I would not bother getting the flywheel grooved unless you find it is necessary. It is possible that a poly vee belt will work directly on the flat part of the flywheel.

 

Might not get the full output but I think it is possible because of the large amount of belt wrap you can get.

 

You would need a tensioner somewhere to get it properly around the alternator pulley though.

 

Another option which has always intrigued me is putting a friction wheel on an alternator and running direct off the flywheel.

 

Again don't know if it would work but might be worth investigating.

 

 

 

 

[steve.sharratt]

21 minutes ago, magnetman said:

I would not bother getting the flywheel grooved unless you find it is necessary. It is possible that a poly vee belt will work directly on the flat part of the flywheel.

 

Might not get the full output but I think it is possible because of the large amount of belt wrap you can get.

 

You would need a tensioner somewhere to get it properly around the alternator pulley though.

 

Another option which has always intrigued me is putting a friction wheel on an alternator and running direct off the flywheel.

 

Again don't know if it would work but might be worth investigating.

 

 

 

 

Getting the flywheel grooved was on recommendation but I agree that it shouldn’t need it, especially as the flywheel is so large.  I did discuss last year on this forum (cant work out how to link it) and these where my calculations:

 

Currently: Using a double v pulley onto the engine pulley is 2.2in (alt) / 15.5in (engine) = 0.142 velocity ratio.  300rpm (engine idle) / 0.142 = 2112 rpm at alternator.

 

Flywheel: PolyV pulley onto engine flywheel is 1.9 (alt) / 23in (engine) = 0.083. 300rpm / 0.083 = 3615 rpm.

 

Using the flywheel takes it from  20 amp to 70 amps at idle and 65 amps to 135 amps at running speed.  

 

The biggest challenge is as you suggest, tension due to contact at the alternator pulley.  I also need to have a decent alternator cradle designed as the flywheel is further from the fire wall hence the reason I think I will get an expert to design.

 

[DHutch]

Can you run a poly-vee pulley onto the flywheel?

[steve.sharratt]

5 hours ago, DHutch said:

Can you run a poly-vee pulley onto the flywheel?

That is my plan but it needs a bit of engineering work that is beyond me as the flywheel is further away from the bulkhead so needs a robust alternator cradle.  I have contacted a local boat yard and plan to drop in for them to assess as I pass through.