Charging Both Ways

[VerMonsterRV]

Hey guys, we had a bit of trouble a couple of days ago. I ended up running the truck out of fuel while in a pretty remote area, but still on a highway. Long story short I need to re-adjust our newish VDO senders to accurately read when the tank is empty and not 1/4 full.... Luckily we had a second tank that was completely full.

So, while on the side of the road in close to freezing temps I tried to bleed the engine. Well with the cold and oncoming night I drained the batteries before I got truck running. So, given that our truck is 24v and our house bank is 12v we have a B2B charger going from the start batteries to the house bank. Great for topping up the house bank while driving, but now I really want to charge the start bank from the house bank when I want to. I have also decided to ditch our Sterling B2B charger as it is now down to 50% capacity because one leg has failed (and this is the second unit after the first one completely failed). I have on order 2 Victron 24/12 30 amp B2B chargers which I can parallel for 60amps of charging. What I also see now is they have a 12/24 15 amp B2B charger which would be perfect for house to start charging. I had hoped to find a suggested wiring schematic on the Victron site but apparently they do not provide tech support and rely on the dealer network for support. So my question is this, does anyone have a great way of doing this? I want the start to house working whenever the alternator is running, but the house to start only to be working when the alternator is not. Thinking about it now I guess I could tie in the ignition switch somehow. But still, if you have a good way to accomplish this just let me know.

 

[joeblack5]

Going from 12 to 24 is no big deal but the Ah are going to be half. Not sure what the capacity of your 12 volt house battery is and how much ah you want to transfer in your 24 volt starter battery ? It also would take a long time..
To late for that now if you do not have it but I only use diesel filtration with a manual piston bleed pump. My bus with a Mercedes om926 had an integrated fuel pump with a drain back leak and I replaced that with an external electric pump.. bleeding is very easy in that case....and cracking the injector lines of course...
Good luck
Johan

 

[joeblack5]

Just a thougt.. to keep it kiss... Have two smaller 12 volt house batteries in parallel.. in case of emergencies you can switch them for the starters..

 

[Geo.Lander]

Hey guys, we had a bit of trouble a couple of days ago. I ended up running the truck out of fuel while in a pretty remote area, but still on a highway. Long story short I need to re-adjust our newish VDO senders to accurately read when the tank is empty and not 1/4 full.... Luckily we had a second tank that was completely full.

So, while on the side of the road in close to freezing temps I tried to bleed the engine. Well with the cold and oncoming night I drained the batteries before I got truck running. So, given that our truck is 24v and our house bank is 12v we have a B2B charger going from the start batteries to the house bank. Great for topping up the house bank while driving, but now I really want to charge the start bank from the house bank when I want to. I have also decided to ditch our Sterling B2B charger as it is now down to 50% capacity because one leg has failed (and this is the second unit after the first one completely failed). I have on order 2 Victron 24/12 30 amp B2B chargers which I can parallel for 60amps of charging. What I also see now is they have a 12/24 15 amp B2B charger which would be perfect for house to start charging. I had hoped to find a suggested wiring schematic on the Victron site but apparently they do not provide tech support and rely on the dealer network for support. So my question is this, does anyone have a great way of doing this? I want the start to house working whenever the alternator is running, but the house to start only to be working when the alternator is not. Thinking about it now I guess I could tie in the ignition switch somehow. But still, if you have a good way to accomplish this just let me know.

Hi Jon,
The Victron smart DCDC chargers have programmable relays you can use for those proposes and also ignition / startup / voltage sensing, all programmable. You will probably need an isolated unit and combine the voltage sensing (alternator to house) with the relay (use the circuit on the alternator to house to trigger the house to start charging).

Much more data is available on their site with functions fully explained, i suppose you have gone for the fully isolated chargers?

 

[Joe917]

Jon, what engine is that? The OM366 should not need bleeding, pump the manual lift pump(right beside the fuel filter) till it gets hard and it should start very quickly.
The injectors are not easy to access.
As for the 24 V battery issue, we carry a 230V 24V battery charger, hook it up to the inverter in just such an emergency, run the generator if necessary.

 

[DiploStrat]

Jon/Dimitri,

As you might guess, the challenge is to break an infinite loop. No charge from engine to camper unless the engine is RUNNING, and no charge from camper to engine unless the engine is OFF.

I do this with two relays, one is a simple on with engine, off when engine off. The other, which controls the charge from camper to engine is a cross over relay. In its normal, not energized state, it turns on the B2B that takes 12v from the camper and gives 24v to the engine. When the engine is on, the relay energizes and that OPENS the contacts, breaking the circuit. (Gotta think that one through a few times.)

Haven't drilled down into the Victron documentation, but:

-- It appears to have a low voltage trigger, which forces the B2B to turn on when the engine voltage is low, as it might be with a modern Euro alternator.
-- What you want is a setting that kills the B2B when the engine is running. If it will do that, then you can avoid at least one external relay.

Does this work? Yes, it works very well. Just don't leave the ignition switch ON when the engine is actually off (as with the exhaust brake switch). A big camper battery bank will impose a large demand on the starter batteries. The B2B will limit the amp flow, but the demand could be of long duration if your camper battery is low.

 

[Sitec]

I'd think along a different and more mechanical route...

I have a Facet in line electric fuel pump on our engine fuel supply line, which will have a push button hidden in the gas locker. This pump will get it's power from the Hab Box batteries (once I have them). Our fuel filters are located at the back of the engine (accessable from the Hab Box floor hatch)... We can bleed the fuel system using the electric pump (Wifetec operated) while I bleed the air at the filters without having to tip the cab. No cranking involved until the last moment when in theory the engine should burst back into life.

Why have I done this...? Because I've been caught out several times (like you) with blocked filters, a blocked fuel pick up line, and a broken return line (meaning air could get into the system and the truck needs bleeding if it was left more than 2 weeks)...

 

[DiploStrat]

Sitec,

Tell me more. Is the idea that this pump is more powerful than the engine pump? I take it that it is in line, before the first filter/water separator, etc.

As I believe that my problem may have been something sucked up from the tank blocking the line, is the idea that this pump would pull it through?

Is the pump normally off and able to pass fuel when it is not needed?

One of these? https://www.facet-purolator.com/

 

[Iain_U1250]

Facet pump will let fuel through when it is turned off, I have one on each tank which I use for bleeding ( and finding leaks) and transferring fuel between the tanks. I'd recommend getting some of them, it makes bleeding the air out of the fuel system a less than five minute job. If I do run the tank dry whilst driving, most of the time I can start the facet pump, switch over to the full tank, and get the engine running all before I come to a complete stop.


I also have on of those little Lithium jump starter packs, they work great provided the engine will start quick, as at best the give about 20 seconds of cranking. I have a 12V Unimog, sot hat's a lot easier and a very different starter battery wiring to most.. If you have two house batteries, you could have a few switches that disconnect them from the camper, and then reconnect the two house batteries in series , which you can use to start the truck, and them switch them back to being in parallel, just takes a few heavy duty switches like the ones from BlueSea systems.

 

[grizzlyj]

Totally disconnect your house bank, rewire with sufficient jump leads to connect to your truck pair to start. You might just need a short length between two 12v house batteries, then two longer ones to reach the starters/chassis?

 

[DiploStrat]

Facet pump will let fuel through when it is turned off, I have one on each tank which I use for bleeding ( and finding leaks) and transferring fuel between the tanks. I'd recommend getting some of them, it makes bleeding the air out of the fuel system a less than five minute job. If I do run the tank dry whilst driving, most of the time I can start the facet pump, switch over to the full tank, and get the engine running all before I come to a complete stop.


I also have on of those little Lithium jump starter packs, they work great provided the engine will start quick, as at best the give about 20 seconds of cranking. I have a 12V Unimog, sot hat's a lot easier and a very different starter battery wiring to most.. If you have two house batteries, you could have a few switches that disconnect them from the camper, and then reconnect the two house batteries in series , which you can use to start the truck, and them switch them back to being in parallel, just takes a few heavy duty switches like the ones from BlueSea systems.

Sitec/Iain,

Would love a photo or two (not Iain's usual subject) and a recommendation of pump model.

 

[Geo.Lander]

Jon/Dimitri,

As you might guess, the challenge is to break an infinite loop. No charge from engine to camper unless the engine is RUNNING, and no charge from camper to engine unless the engine is OFF.

I do this with two relays, one is a simple on with engine, off when engine off. The other, which controls the charge from camper to engine is a cross over relay. In its normal, not energized state, it turns on the B2B that takes 12v from the camper and gives 24v to the engine. When the engine is on, the relay energizes and that OPENS the contacts, breaking the circuit. (Gotta think that one through a few times.)

Haven't drilled down into the Victron documentation, but:

-- It appears to have a low voltage trigger, which forces the B2B to turn on when the engine voltage is low, as it might be with a modern Euro alternator.
-- What you want is a setting that kills the B2B when the engine is running. If it will do that, then you can avoid at least one external relay.

Does this work? Yes, it works very well. Just don't leave the ignition switch ON when the engine is actually off (as with the exhaust brake switch). A big camper battery bank will impose a large demand on the starter batteries. The B2B will limit the amp flow, but the demand could be of long duration if your camper battery is low.

You dont need an external relays, there are 2 ways to activate house -> start circuit charging, either using the program engine detection with your custom voltages on the alternator line into the DCDC line or a combination of the L-pin override. you do not even need an isolator as you can use the voltage detection metrics to program your own start and stop parameters and use the L-pin integrated switch on the Alternator->House bank circuit (although that would need a simple relay). Plenty of ways to do this once you dig into the docs on the Orion units

 

[DiploStrat]

Just be very, very careful - you can create an infinite loop where each charger is chasing the other. Most of these beasts are intended to turn on when the engine is running, and throttle back when the battery is charged. In this case you need a brick wall that assures that the camper>starter charger CANNOT run if the engine is running. This is a bit counter-intuitive. Especially running lithium to lead acid, the lithium is very likely to be above the turn on voltage almost all the time.

 

[Sitec]

Sitec,

Tell me more. Is the idea that this pump is more powerful than the engine pump? I take it that it is in line, before the first filter/water separator, etc.

As I believe that my problem may have been something sucked up from the tank blocking the line, is the idea that this pump would pull it through?

Is the pump normally off and able to pass fuel when it is not needed?

One of these? https://www.facet-purolator.com/

Hi DiploStrait.

It's a small Facet Cube pump. These can be bought in 12 or 24v. The cube pumps don't have an anti syphon valve in them, so can be used as a primer pump to bleed the system,but then just sit quietly in the fuel line (between the fuel tank and first filter) doing nothing until such a time as it's needed as it will let fuel pass when not in use. I'll only use it to bleed the system if I run the truck out of fuel, change filters etc. Re pulling a bockage through, no it won't do that, but it will indicate to you that there is a blockage prior to the pump when using it to try and bleed the system as no fuel will flow out at the filter bleed points. This is where the fuel pump can be disconnected on the suction side, and an air line used to blow air back into the tank (fuel cap off) to reverse the blockage. With the fuel line clear, the fuel lines can be reconected and the Facet used to bleed the system. The main reason for having this is so we don't have to crank the engine to prime it, or tip the cab to get to the hand primer.

 

[DiploStrat]

Tanx! All makes sense to me. Will throw one into my tank clean/rebuild/replacement.