Victron DC to DC wiring

[duck21]

Hi all!

It's winter time up here in the frozen north, but I'm already getting excited for spring. Only 4(ish) more months until launch!

In the meantime, I'm starting to plan out projects. One project about which I am quite excited is an upgrade to our alternator charging system.

We currently have the OEM Hitachi alternator wired to the mid-90's Hunter shunt, dividing charging to the start and house batteries (currently a group 24 start and 4D house, both lead acid).

I am now in possession of two new Victron DC to DC chargers -- a Victron Orion XS 50 amp and a Tr Smart 9 amp DC to DC charger. The 50 amp would be between the alternator and the house battery, the 9 amp between the house battery and the start battery. The goal here is to output cleaner power from the alternator to the batteries (real, actual voltage controlled bulk and float stages) , baby the alternator for more extended higher amperage output (as I've understood this is accomplished by current limiting the charger to 40 amps, keeping the alternator from moving to "self protect" mode as quickly), and potentially prep for a future upgrade to Lithium.

The more immediate planning question (and the reason for this post) is best determining how to wire the new units. Specifically: should I (mostly) re-use the existing alternator charging wiring, or should I run new wires and connect these units directly to the batteries. I see advantages/disadvantages to both options:

Keeping the existing layout:
Pros: Physically simpler wiring, DC units are mounted in a compartment with more space, the ability to shut off power between the battery and alternator
Cons: Wiring may be a little undersized (it's the OEM Hunter wiring), extra failure points with the battery switches in line


New wiring:
Pros: A simpler system (more direct wires), fewer failure points, right sized wire
Cons: Some space concerns for the House to Start charger location, more cabling to pull, more contact points on the batteries/bus bars

I've included a great MS Paint drawing of the existing configuration and how the two options may look. The drawing is basic -- I'd obviously include fuses, wiring for indication that the motor is running and (most obviously) I used a red line, but the negative would be wired appropriately for the circuit. With that would folks with more expertise in this area recommend?

 

[dlochner]

I don't really understand the reasoning for the 50a DC-DC charger. It is perfectly OK to run the Alternator output to a DC+ bus and then connect that to the battery.

Everything gets connected to the DC+ Bus, alternator, charger, DC-DC charger for the start battery, the feed to the panel, etc. This keeps the wiring to the battery simple and uncluttered. Wired correctly, there will be 3 switches, on/off switches for the battery and a BlueSeas Dual Circuit Plus switch which will allow either battery to start the engine and/or power the house batteries.

To future proof your wiring use wires capable of handling the high output of 100+amp externally regulated alternator.

Spend some time reading Rod Collin's MarineHowTo.com website. It has numerous articles on batteries, charging, and other topics on marine electrical systems. Solid information from a well respected professional.

Marine How To - DIY for Boaters - Marine How To

For DIY boaters in an attempt to try and keep the sport as affordable & safe as possible. How To articles for sailboats and powerboats.

marinehowto.com

 

[duck21]

Hi!

From everything I've read and observed the stock Hunter/Yanmar Hitachi alternators, while great for car scenarios, are pretty terrible for maintaining larger battery banks:

DC to DC charger size

I have a question for all of you that have switched to lithium house banks but kept the AGM start batery. What size DC to DC charger did you install? I have an 80amp alternator on my Yanmar. I would like to go as large as possible in order to facilitate faster house charging, but I do not...

forums.sailboatowners.com

The actual inspiration for this project was from the same thread (here's the parent):

DC to DC charger size

I have a question for all of you that have switched to lithium house banks but kept the AGM start batery. What size DC to DC charger did you install? I have an 80amp alternator on my Yanmar. I would like to go as large as possible in order to facilitate faster house charging, but I do not...

forums.sailboatowners.com

As well as Rod's Marine How To article about automotive alternators (like my Hitachi) being used for powering larger battery banks:

Automotive Alternators vs. Deep Cycle Batteries - Marine How To

A Deep Cycle Battery Assassin The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this

marinehowto.com

The main goals with the DC to DC are to provide better regulated voltage to the battery and to keep the alternator from pushing 60-70 amps for 5 minutes then backing way off on amperage output to 15-20 as it self regulates. In my reading keeping the Victron DC to DC at about 40 Amps will actually keep the alternator happy for longer periods of time while also regulating the voltages to the battery in the preferred bulk/absorption/float stages.

The other options are to wire an external voltage regulator to the Hitachi, which I'd rather not do, or to replace the unit with a smart alternator -- which I considered. But most smart alternators are quite a bit more expensive (I missed the boat on the Hitachi drop-in that Rod used to produce), and the other drop- in options don't offer significantly greater output (while the higher output options require modifications to the drive/belt system).

I think my plan is pretty solid, but I'm just a bit on the fence about wiring through the switches vs. direct to the DC bus bars near the battery. I'm leaning toward all fresh wiring however, which does match your suggestion -- just looking for the additional thoughts as to whether there are other pros/cons.

Doug

 

[JoeWhite]

The DC to DC victron that I use to charge the batteries from solar panels requires a minimum of 17 VDC to have an output. Does the alternator produce high enough voltage to make the Victron put out regulated voltage?

 

[dlochner]

The DC to DC victron that I use to charge the batteries from solar panels requires a minimum of 17 VDC to have an output. Does the alternator produce high enough voltage to make the Victron put out regulated voltage?

The Victron solar controllers and DC-DC chargers are different critters. Solar panels don't produce 12v, they typically produce more than 20 volts (at least the larger ones 50w and higher) and very few amps. Victrons require the panel out put to be 5v above the battery's voltage so that when the voltage is reduce to a safe charging voltage (~14.6 for LA batteries) there is enough amperage to actually charge the battery.

DC-DC chargers will come on line at a pre-programed voltage based on the DC source (alternator, charger, or battery bank) and raise or lower that voltage to charge a battery. The only requirement is the input voltage meet the programmed voltage. They do not need a 5v difference between the source and the battery being charged.

 

[dlochner]

I think my plan is pretty solid, but I'm just a bit on the fence about wiring through the switches vs. direct to the DC bus bars near the battery. I'm leaning toward all fresh wiring however, which does match your suggestion -- just looking for the additional thoughts as to whether there are other pros/cons.

Ideally the start and house batteries should be isolated in normal use, however, all systems should be able to run on either battery in an emergency. And it should be human proof, so some well meaning soul doesn't accidentally drain both batteries. I forget in which of Rod's articles this system is described. It is the one I used in my boat. It is also a good idea to avoid using the posts on a switch as a power post with multiple wires attached. The Blue Sea Dual Circuit switch accomplishes this.

While Blue Sea switches and bus bars are the darlings of the DIY boating community, there is another brand BEP Pro that offers a few advantages. The BEP switches can be surface mounted, it makes wiring much easier. They also have a bus bar system that is very flexible. The quality is just as good as Blue Sea. BEP is part of Brunswick's Navico Group which also owns Blue Seas.

 

[Maine Sail]

The Victron DC to DC chargers go-between batts not an alt and a batt..

 

[duck21]

This all makes sense -- I was thinking of the Victron XS as functioning somewhat similar to the Sterling Alternator to Battery charging unit. I appreciate the guidance on this -- I'll amend my plans accordingly!

Thanks,
Doug