DC to DC charger 12V to 24V battery....

[southsouth]

before you ask why would you have a 24v system, well...i found a 24v water pump, a/c, fridge, led lights, heating pads...and I likely will have not much on 12v....and 24v gives me the discharge rate to run a small welder if I want one day.
24v alternators are expensive, and I don't know if its possible to down step it to 12v for the cars system. And running two alternators sounds like a hassle. Ill have 1000W on the roof and 330AH 24v battery.

I am trying to find a DC to DC charger so my 12v alternator can charge my 24v battery bank.

Solution found online is a Orion TR 12/24-15A. Which is extremely low 360wh, especially for the cost.
Alternative solution is the Victron Orion IP67 12/24-50A. A very high 1200 wh.
But this is "non isolated" while the other is.

So does someone know if it would be okay for a van to use a non isolated 12v dc to 24v.

I also found VOTRONIC 3341 DC voltage converter DC/DC 1224-25 12V to 24V which states it is "galvanic isolated"....is this the same as isolated?

Another solution is the renogy two in one mppt plus DC to DC, but I have seen mixed reviews. Anyone use the renogy just for the alternator?

 

[outboard1196]

before you ask why would you have a 24v system, well...i found a 24v water pump, a/c, fridge, led lights, heating pads...and I likely will have not much on 12v....and 24v gives me the discharge rate to run a small welder if I want one day.
24v alternators are expensive, and I don't know if its possible to down step it to 12v for the cars system. And running two alternators sounds like a hassle. Ill have 1000W on the roof and 330AH 24v battery.

I am trying to find a DC to DC charger so my 12v alternator can charge my 24v battery bank.

Solution found online is a Orion TR 12/24-15A. Which is extremely low 360wh, especially for the cost.
Alternative solution is the Victron Orion IP67 12/24-50A. A very high 1200 wh.
But this is "non isolated" while the other is.

So does someone know if it would be okay for a van to use a non isolated 12v dc to 24v.

I also found VOTRONIC 3341 DC voltage converter DC/DC 1224-25 12V to 24V which states it is "galvanic isolated"....is this the same as isolated?

Another solution is the renogy two in one mppt plus DC to DC, but I have seen mixed reviews. Anyone use the renogy just for the alternator?

You can use multiple Orion's to achieve your desired charge current. You can use both isolated and non isolated as long as you use the same ground.

 

[NWC100]

Wait for the Orion XS1400 if that's what it remains named as! 12/24V upto 50A as well, and other tricks up its sleeves!

 

[mikefitz]

know if it would be okay for a van to use a non isolated 12v dc to 24v.

It's not an issue. For safety the house battery needs the negative to chassis/van metal connection so you would loose any isolation.

Sterling power offer 12 to 24 chargers,

Sterling Power battery to battery charging system - DC to DC smart battery charger, marine grade DC powered charger 12v to 24v

DC to DC converter. Charge your auxiliary battery bank with the correct multistage, temperature compensated charging curve by using the input power of any vehicles alternator thru the start battery system automatically while the vehicle is running.

www.sterling-power-usa.com

The Renogy unit may be worth trying.

Consider the load on the van alternator , a 50 amp output at 24 volts is 100 amps plus at 12v.

 

[HarryN]

24 volt is ideal for mobile use, vans, trailers, etc.

When you stop looking at just the victron web site, there are a number of good option.

Just use your browser and type in 12 to 24 volt battery to battery charger.

Sterling offers a number of options.

Depending on your exact vehicle, using an inverter to pull power from it can be a good path.

( starter battery ) ---- ( breaker ) ---- ( 12 volt inverter ) ------------120 vac ------------( 24 volt charger ) ---- (breaker or fuse ) ----( 24 volt battery )

 

[southsouth]

Wait for the Orion XS1400 if that's what it remains named as! 12/24V upto 50A as well, and other tricks up its sleeves!

yes but its non isolated. I am still trying to figure out what the isolated vs non isolated vs galvanvic isolated means.....otherwise I dont know why anyone would pay for a isolated dc to dc which are lower amps and 2-3x more expensive than the non isolated counterparts

 

[southsouth]

It's not an issue. For safety the house battery needs the negative to chassis/van metal connection so you would loose any isolation.

Sterling power offer 12 to 24 chargers,

Sterling Power battery to battery charging system - DC to DC smart battery charger, marine grade DC powered charger 12v to 24v

DC to DC converter. Charge your auxiliary battery bank with the correct multistage, temperature compensated charging curve by using the input power of any vehicles alternator thru the start battery system automatically while the vehicle is running.

www.sterling-power-usa.com

The Renogy unit may be worth trying.

Consider the load on the van alternator , a 50 amp output at 24 volts is 100 amps plus at 12v.

My alternator is minimum 90a output but easily replaced with up to a 200a. The renogy is interesting solution but its unclear if it would pull its maximum 50amp from the alternator. Some posts have said it will max at 25a

 

[HarryN]

My alternator is minimum 90a output but easily replaced with up to a 200a. The renogy is interesting solution but its unclear if it would pull its maximum 50amp from the alternator. Some posts have said it will max at 25a

If you have a Transit with a 220 amp alternator, then you really only have ~ 50 amps to spare for BTB charging.

If it is a dual alternator setup, then it is viable to go to ~ 100 amps or so.

ALL solutions will deliver less amps than the label.

 

[southsouth]

If you have a Transit with a 220 amp alternator, then you really only have ~ 50 amps to spare for BTB charging.

If it is a dual alternator setup, then it is viable to go to ~ 100 amps or so.

ALL solutions will deliver less amps than the label.

I have a t1n sprinter.
I am surprised by the ratio of output and spare capacity for the transit.
I am not familiar with how alternators output their charge, is it based on idle speed or internal regulator that senses demand?

 

[nwillitts]

before you ask why would you have a 24v system, well...i found a 24v water pump, a/c, fridge, led lights, heating pads...and I likely will have not much on 12v....and 24v gives me the discharge rate to run a small welder if I want one day.
24v alternators are expensive, and I don't know if its possible to down step it to 12v for the cars system. And running two alternators sounds like a hassle. Ill have 1000W on the roof and 330AH 24v battery.

I am trying to find a DC to DC charger so my 12v alternator can charge my 24v battery bank.

Solution found online is a Orion TR 12/24-15A. Which is extremely low 360wh, especially for the cost.
Alternative solution is the Victron Orion IP67 12/24-50A. A very high 1200 wh.
But this is "non isolated" while the other is.

So does someone know if it would be okay for a van to use a non isolated 12v dc to 24v.

I also found VOTRONIC 3341 DC voltage converter DC/DC 1224-25 12V to 24V which states it is "galvanic isolated"....is this the same as isolated?

Another solution is the renogy two in one mppt plus DC to DC, but I have seen mixed reviews. Anyone use the renogy just for the alternator?

this is what you seek-i use it for same reason as your setup.

https://www.amazon.com/dp/B0DFBVYK2C?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

 

[HarryN]

I have a t1n sprinter.
I am surprised by the ratio of output and spare capacity for the transit.
I am not familiar with how alternators output their charge, is it based on idle speed or internal regulator that senses demand?

Every single van out there has it's own values of what can be pulled.

If my memory is working, MB spec for the T1N is 40 amps that can be pulled, but 50 is pretty close.

The T1N is the last of the alternators that work from a voltage regulator instead of the engine controller ( ECU ) operating the alternator field current. I believe in the VS3 model this has increased to 80 amps, but need to look again.

MB parts tend to be expensive and challenging to find, so there is a tendency, at least for me, to run them fairly conservatively, but I always try to have customer setups stay well within the specs and am extremely careful about grounding approaches. If you can, try to use solar on the van, as much as possible rather than tap into the van - just for those reasons.

___________

The aspect of alternator output that is not always appreciated is how much the output depends on ( field current ) x ( rpm ) , and there is relatively little output on many of them until the engine rpm hits at least 1000 rpm. ( ~ 3000 rpm alternator )

So the way that Ford runs their dual alternator setup, is to run alternator #1 as long as it can keep up, and then supplement with #2 to keep up if needed. It isn't both running full out all of the time.

People on those transit dual alts have pushed up to 150 amps, but have broken parts under the seat at 175, and it isn't a part that is so easy to find.

____________

The ECU in a modern vehicle will actually turn off alternator charging and run the battery down to 75 - 85% in some driving conditions, and then when the brake pedal is pushed, will push a large field current into the alternator to capture the rotational inertia of the engine slowing down to really pump the power into the starter battery. ( in some vehicles, an additional battery )

MB was the first van to start using this concept aggressively, and others have followed with increasingly active control over time.

____________

So the answer to your simple question is - the ECU control algorithm does what it wants to do and we are along for the ride, and it isn't always so easy to figure out.

 

[southsouth]

Every single van out there has it's own values of what can be pulled.

If my memory is working, MB spec for the T1N is 40 amps that can be pulled, but 50 is pretty close.

The T1N is the last of the alternators that work from a voltage regulator instead of the engine controller ( ECU ) operating the alternator field current. I believe in the VS3 model this has increased to 80 amps, but need to look again.

MB parts tend to be expensive and challenging to find, so there is a tendency, at least for me, to run them fairly conservatively, but I always try to have customer setups stay well within the specs and am extremely careful about grounding approaches. If you can, try to use solar on the van, as much as possible rather than tap into the van - just for those reasons.

___________

The aspect of alternator output that is not always appreciated is how much the output depends on ( field current ) x ( rpm ) , and there is relatively little output on many of them until the engine rpm hits at least 1000 rpm. ( ~ 3000 rpm alternator )

So the way that Ford runs their dual alternator setup, is to run alternator #1 as long as it can keep up, and then supplement with #2 to keep up if needed. It isn't both running full out all of the time.

People on those transit dual alts have pushed up to 150 amps, but have broken parts under the seat at 175, and it isn't a part that is so easy to find.

____________

The ECU in a modern vehicle will actually turn off alternator charging and run the battery down to 75 - 85% in some driving conditions, and then when the brake pedal is pushed, will push a large field current into the alternator to capture the rotational inertia of the engine slowing down to really pump the power into the starter battery. ( in some vehicles, an additional battery )

MB was the first van to start using this concept aggressively, and others have followed with increasingly active control over time.

 

[southsouth]

This seems to be the go to for figuring this out, and also mentions the transit in it.

T1N 200amp alternator

The point I make is that a DC2DC inverter/converter/whatchmacallit is a quite comical as a solution when considering the capacity of an alternator and contrasting the scalably in price needed as the DC2DC units reach toward the real capacity of an alternator. In fact I'd likely go with...

sprinter-source.com

Summery of what i think is relevant is that the t1n alternator has three versions, 90a, 150a, 200a. connecting lifepo4 to alternator terminal is a not the way. It should be connected to the D+ terminal.

Dc to Dc chargers that pull 30a do not work because the t1n can pull 60a and the alternator at idle produces 60a or it produces 90a at idle but pulls occasionally more than 60a, which cuts off the 30a dc to dc charger.

That said, the larger 150a and 200a versions people have used with success. Both dc-dc chargers and even directly charging empty lifepo4 400ah banks without a dc-dc.

From what I gathered I think I will upgrade my alternator, assuming it just the 90a version, and run a 60 amp dc to dc. As for directly charging lifepo4 from alternator for a fast charge, I would need to do more research and contact those that have been doing that for years. But theoretically with a 200a alternator it should be possible to charge with 120-130 amps, which is around 1500 watts. This would fast charge my 8kwh battery's very quickly.

 

[mikefitz]

connecting lifepo4 to alternator terminal is a not the way. It should be connected to the D+ terminal.

Not correct, D+ is a 'alternator charging' indication voltage and on your alternator the energising point, its not a point on the alternator where you take power. It an be used as a control signal for DC to DC chargers, the power input to the charger is from B+.
The power is from B+, a M8 stud, D+ is a M5 stud . In the UK OEM fit was 90, 115, 150, ( 200 special) amp alternator, 150 amp are readily available, not too expensive.

200a alternator it should be possible to charge with 120-130 amps,

In theory, but this is high stress for the alternator, 120 amps is the possible maximum at engine idle speed. The van circuits, the starter battery need power, perhaps up to 50 amps, this limits the 'spare' current to much less than 120 amps.

Your alternator, red markup is power connection B+, green markup is D+.

 

[HarryN]

Whatever you do, don't go down the path of trying to charge your house battery directly from an alternator, unless it is specifically equipped to control the current flow, not just the voltage.

If the battery SOC is low, it can behave more or less like a black hole, and pull so hard it will destroy not only your van, but also the battery itself.

When the SOC is high, then the charging rate can be very poor.

Just because a few people have gotten away with it "much of the time", does not mean that it a reliable method.

It is not just the alternator that limits current flow on the sprinters, it is also parts of the van wiring. I have not worked on a T1N for a while, so I don't remember all of the details. Going to a higher amp version can be helpful. Watch the pulley size.

 

[southsouth]

Not correct, D+ is a 'alternator charging' indication voltage and on your alternator the energising point, its not a point on the alternator where you take power. It an be used as a control signal for DC to DC chargers, the power input to the charger is from B+.
The power is from B+, a M8 stud, D+ is a M5 stud . In the UK OEM fit was 90, 115, 150, ( 200 special) amp alternator, 150 amp are readily available, not too expensive.

In theory, but this is high stress for the alternator, 120 amps is the possible maximum at engine idle speed. The van circuits, the starter battery need power, perhaps up to 50 amps, this limits the 'spare' current to much less than 120 amps.

Your alternator, red markup is power connection B+, green markup is D+.

Thanks for the info and correction. I reread that forum and yes the D+ was used a signal to a dc-dc, not for drawing power directly from D+.

I got confused because another member posted that he used a 'constant duty relay' tied to the D+ to charge his lifepo4. Not sure what a constant duty relay is but that member has been over landing his t1n for 7 years and posting on his 60 page his build and problems, and I don't think he had to replace his alternator or lifepo4. I will message him directly about his experience and recommendation.

Overall it seems it is feasible to charge from the alternator and at a considerable wattage, using non isolated dc-dc chargers, in one way or another at a small relative cost.

Dc-dc is not essential to my charging needs, just like a 8kwh or 12kwh battery bank with 300a bms isn't either. But what I do want is a versatile system, one that makes it possible using a small welder. Primarily the dc-dc charging would be needed to replenish batterys after operating a mini split on cloudy days. Ultimately my bus bar could have the battery, mppt, inverter/charger, dc-dc, 12v distribution and 24v distribution boxes on it. Since im spray foaming I plan to run all the circuits I potentially I will ever want.

 

[mikefitz]

posted that he used a 'constant duty relay' tied to the D+ to charge his lifepo4.

What the guy was saying is that D+ was connected to the activation coil of the high current relay, the switch contacts of the relay connected the starter battery/alternator to the house battery. This is a common technique where the house battery is lead acid.
When you use the same system with lithium you are relying on the circuit impedance, ( resistance of cable and everyone else in the charge ciruit) and the saturation of the alternator, where its at maximum and thus its output voltage falls. Under these conditions its running very hot

You intend to have a 24 volt system that needs either an additional 24 volt alternator or DC to DC converter.

feasible to charge from the alternator and at a considerable wattage, using non isolated dc-dc chargers,

For reliable operation limit ensure the DC converter does not overload the single alternator. A damaged alternator is incovienent, if it takes down the vans ECU as it fails, its a costly fix.

 

[southsouth]

according to victron sales rep the 12/24 50a non isolated charger outputs 24v. So its not suitable to charge.

 

[RV8R]

Hi @southsouth

After reading thru your thread here;

1) Careful about burying wires in foam insulation

2) If you want to charge by alternator, best to identify the power you can draw using a DC2DC from your current alternator & future upgraded alternator. Part of this is understanding MB proprietary systems etc. @HarryN has worked on MB, Ford, & Promaster vans, so has a good understanding of each manufacturer. I also like what @mikefitz posted for you ,,, D+ is typically (always), a signal wire to turn these DC2DC’s on/off ,,, many of these DC2DC also use starter battery/alternator voltage readings to do the same.

3) It is a good idea to perform load calculations for your system in order to design it. Electrical systems are designed from “The Loads” as the primary consideration.


DC2DC Choice;

Kisae I believe also makes a 12vdc to 24vdc & it might also be a dual ( alternator & solar ) charger. I have a Kisae 1250 which is 12v & max 50amps that I use on my 2021 Promaster. The voltage & amperage can be user set. Amps can be set ( 5a to 50a in 5a increments ). I also have AGMs. Here was yesterday charging at idle;





The above numbers would look different with LFP batteries ,,, voltage & amperage would be a constant 50 amps after engine startup.


Here is a link to the Kisae DMT 2430 ( I assume it is fully programmable like my Kisae 1250 );

https://www.kisaepower.com/wp-content/uploads/2024/01/Datasheet_DC_to_DC_Charger_DMT2430.pdf

If that DC2DC interests you, best to contact Kisae directly (by email), to get information on it & see if it will fit your needs ,,, “Ricardo” is the tech guy I have dealt with & he is excellent.

 

[Dooug]

according to victron sales rep the 12/24 50a non isolated charger outputs 24v. So its not suitable to charge.

The current 50 amp victron DCDC is just a converter, so constant voltage. Like.mentioned before, there is a new model coming out soon that will be a "smart" version and do 50 amps.

 

[HarryN]

The current 50 amp victron DCDC is just a converter, so constant voltage. Like.mentioned before, there is a new model coming out soon that will be a "smart" version and do 50 amps.

Just like apple - our next model will be better than what we offer today - almost as good as what you can buy from other people for years.

 

[southsouth]

Hi @southsouth

After reading thru your thread here;

1) Careful about burying wires in foam insulation

2) If you want to charge by alternator, best to identify the power you can draw using a DC2DC from your current alternator & future upgraded alternator. Part of this is understanding MB proprietary systems etc. @HarryN has worked on MB, Ford, & Promaster vans, so has a good understanding of each manufacturer. I also like what @mikefitz posted for you ,,, D+ is typically (always), a signal wire to turn these DC2DC’s on/off ,,, many of these DC2DC also use starter battery/alternator voltage readings to do the same.

3) It is a good idea to perform load calculations for your system in order to design it. Electrical systems are designed from “The Loads” as the primary consideration.


DC2DC Choice;

Kisae I believe also makes a 12vdc to 24vdc & it might also be a dual ( alternator & solar ) charger. I have a Kisae 1250 which is 12v & max 50amps that I use on my 2021 Promaster. The voltage & amperage can be user set. Amps can be set ( 5a to 50a in 5a increments ). I also have AGMs. Here was yesterday charging at idle;

View attachment 282406

View attachment 282407

The above numbers would look different with LFP batteries ,,, voltage & amperage would be a constant 50 amps after engine startup.


Here is a link to the Kisae DMT 2430 ( I assume it is fully programmable like my Kisae 1250 );

https://www.kisaepower.com/wp-content/uploads/2024/01/Datasheet_DC_to_DC_Charger_DMT2430.pdf

View attachment 282409

If that DC2DC interests you, best to contact Kisae directly (by email), to get information on it & see if it will fit your needs ,,, “Ricardo” is the tech guy I have dealt with & he is excellent.

Thanks a bunch. That certainly looks like great value. Ill email them directly to confirm

 

[RV8R]

Thanks a bunch. That certainly looks like great value. Ill email them directly to confirm

I use my Kisae 1250 just as an alternator DC2DC charger ( I don’t have solar on my van ). Although I have tested out the solar side of my DC2DC with a 100W panel & that worked quite well;

https://www.promasterforum.com/posts/861492/

Best to review your application & any unit you are interested in directly with Kisae to see if it is a good fit before buying anything. I think you are planning on more solar panels than the Kisae unit can handle.

 

[Drizzt321]

You can use both isolated and non isolated as long as you use the same ground.

I got an Orion Isolated since I'm charging from my tow vehicle, and I didn't want to worry about connecting battery & vehicle (and thus trailer) ground all together. Is it generally just fine to have battery & trailer/two vehicle ground connected?

 

[outboard1196]

I got an Orion Isolated since I'm charging from my tow vehicle, and I didn't want to worry about connecting battery & vehicle (and thus trailer) ground all together. Is it generally just fine to have battery & trailer/two vehicle ground connected?

They normally are grounded together for trailer lights / brakes to work.