DC to DC Charging

[dmbraaten]

I have read the threads on upgrades to alternators, chargers, and lithium batteries which was interesting. I am upgrading my house bank to 1000Ah of lithium with Victron lynx input/bms/distribution and 2 Quatro II 5k in parallel.

My question is how to charge the stern and bow battery banks. I was thinking of connecting DC to DC chargers (Victron Orion) from the Lynx distribution to each of these banks. But some folks have told me this is not a good idea without explaining why. Seems that if I am fully charging the lithium bank via alternator/genset/shore power/solar, I should be able to use this bank to keep the thruster batteries charged up.

Thoughts?

 

[mvweebles]

I have read the threads on upgrades to alternators, chargers, and lithium batteries which was interesting. I am upgrading my house bank to 1000Ah of lithium with Victron lynx input/bms/distribution and 2 Quatro II 5k in parallel.

.....DC to DC chargers (Victron Orion) from the Lynx distribution to each of these banks. But some folks have told me this is not a good idea without explaining why......

I hope it's not a bad idea - this is exactly how I'm configured. I'll be interested in feedback on this thread to see if I should reconsider.

Peter

 

[HeadedToTexas]

While each has its place, DC to DC chargers and automatic charging relays cost about the same, but DC to DC chargers can be programed to specific needs and seem like a more intelligent approach than ACRs today. When my time comes, that's where I'm leaning too.

 

[O C Diver]

I have read the threads on upgrades to alternators, chargers, and lithium batteries which was interesting. I am upgrading my house bank to 1000Ah of lithium with Victron lynx input/bms/distribution and 2 Quatro II 5k in parallel.

My question is how to charge the stern and bow battery banks. I was thinking of connecting DC to DC chargers (Victron Orion) from the Lynx distribution to each of these banks. But some folks have told me this is not a good idea without explaining why. Seems that if I am fully charging the lithium bank via alternator/genset/shore power/solar, I should be able to use this bank to keep the thruster batteries charged up.

Thoughts?

If you have a inverter that's on 24 / 7, another plan is to charge the banks with 120 volt AC chargers. This allows for recharging from shorepower, generator, engine alternator, or solar. Certainly more options in chargers using AC chargers.

In my experience, 6 amp chargers are sufficient to charge thruster banks with it taking less than an hour to recharge them. Below is a picture of my 24 volt bow thruster bank.

Ted

 

[Portage_Bay]

My boat was set up with a dedicated small 120 V AC charger to the thruster bank when I purchased the boat. It works well. If it's easier to tap into an existing 120 V AC line than pull new DC lines that is what I would do.

 

[tiltrider1]

My alternators charge my start bank. I use a DC to DC charger to pass excess capacity on to my house bank because of the mixed chemistry between the two banks.

My thruster, generator, and hoist banks all use AC current to charge. This is due to convenience and mixed voltages.

There are multiple ways to achieve the same result so without knowing your full system and goals it’s hard to recommend a solution.

 

[HeadedToTexas]

There are multiple ways to achieve the same result...

That's for sure.

Do you guys using dedicated AC chargers have them switched so that they can be shut off when your inverter is supplying AC to the boat, or is the load so light that it's not worth the risk of leaving that switch off?

 

[SteveK]

That's for sure.

Do you guys using dedicated AC chargers have them switched so that they can be shut off when your inverter is supplying AC to the boat, or is the load so light that it's not worth the risk of leaving that switch off?

Mine is wired to only work from shore power and then manually turned on as needed

 

[Portage_Bay]

That's for sure.

Do you guys using dedicated AC chargers have them switched so that they can be shut off when your inverter is supplying AC to the boat, or is the load so light that it's not worth the risk of leaving that switch off?

Mine is on anytime there is 120 V AC to the fwd cabin. Shore, gen or inverter. I've not measured the draw once the batts are charged but I suspect is near zero.

 

[Freedomvango]

In this route i would just use a normal ip22 or ip67 through the system and just do it that way. its basically the same power regardless with just a hair more loss doing it 120v

I put it on a breaker so you can turn the chargers off when you don't need them.

 

[Jeff F]

I have three Orion units charging bow, stern and start banks. All are powered from the LiFePo house bank, and all charging sources - solar, alternator, genset and shore power - charge the house bank.

This has worked well for me over 4 years of live aboard use. The chargers can be configured to turn on or off according to source voltage, which means that once configured you can forget about them.

 

[HeadedToTexas]

This has worked well for me over 4 years of live aboard use.

There are lots of right answers, but some are better for some uses than others. Live aboard is different than full time cruising which is different than weekend use.

Our boat is similar to yours in that all charging sources charge the house bank and the house bank powers the inverter. Start batteries are maintained, such as it is, by automatic charging relays. I think the DC to DC technology is better than ACRs, and that is part of my upgrade path.

 

[O C Diver]

That's for sure.

Do you guys using dedicated AC chargers have them switched so that they can be shut off when your inverter is supplying AC to the boat, or is the load so light that it's not worth the risk of leaving that switch off?

Mine runs off a circuit fed by the inverter and then automatically switched to shorepower or generator as applicable. Once charged, power consumption is negligible. I have the same charger for the generator and engine batteries. With the newer style battery chargers, there's no reason not to maintain full batteries when shorepower or the inverter are available.

Ted

 

[Jeff F]

There are lots of right answers, but some are better for some uses than others. Live aboard is different than full time cruising which is different than weekend use.

Agree that there are always different ways of doing things.

My intended and actual use has been daily travel and anchoring 9 -10 months of the year. I didn't give any consideration to optimizing for shore power or generator.

 

[Beekeepergreg]

Keep in mind that LiFePo will receive and discharge at very high rates. I like the DC to DC to limit the current. Victron with the Bluetooth is very handy.

 

[tiltrider1]

My 120v chargers run off my inverter. My bank is large enough that the inefficiencies of doing it this way are insignificant. Meaning, if my crane or thruster batteries need charging then the boat is running and there is excess power generation available. My generator is a last back up option so I would rather have it 100% than more usable time on the house bank.

 

[dmbraaten]

Thank you all for your input! Good things to consider. I posted the same on the Selene owners forum and one response was interesting and would like your comments.

Owner connected his stern thruster batteries into the house so he gained more Ah without needing additional space as the battery compartment was already there. Now he runs his stern thrusters off the house and doe not have a separate bank any more. His calculations were that the 10 or 15 second burst of the thruster would not significantly deplete the lithium house and it charged up quickly from what ever source is charging the house (alternator, shore, genset, solar).

I find that very interesting and am looking into this concept for both bow and stern trusters. I have 2 battery boxes for each which gives me 4 lithium batteries plus the 4 I had originally planned.

 

[Mac2]

As others have pointed out, there are many ways to accomplish what you’re doing. I prefer to isolate all my systems if possible. I’ve learned this the hard way. It’s not if, but when will the system break. I find it easier to solve a problem if you don’t have to figure out multiple system possibilities.
The only caveat would be how much space yo have. Sounds like you have isolated bow and stern thruster battery banks now. How are they being charged? Is your priority to expand your house bank using bow and stern thruster batteries?

 

[BB-marine]

I have read the threads on upgrades to alternators, chargers, and lithium batteries which was interesting. I am upgrading my house bank to 1000Ah of lithium with Victron lynx input/bms/distribution and 2 Quatro II 5k in parallel.

My question is how to charge the stern and bow battery banks. I was thinking of connecting DC to DC chargers (Victron Orion) from the Lynx distribution to each of these banks. But some folks have told me this is not a good idea without explaining why. Seems that if I am fully charging the lithium bank via alternator/genset/shore power/solar, I should be able to use this bank to keep the thruster batteries charged up.

Thoughts?

I may be misunderstanding your question. If so explain a bit more of your upgrade. What type of batteries are you using for your starter bank? AGM, flooded, maintenance free? What type of batteries are you using for your thruster bank? AGM, flooded, maintenance free? We know that the house bank will be lithium. Based on your post you plan on charging the lithium banks using alternator/genset/shore power charge/ and solar charger. How are you charging the cranking battery bank and generator battery bank? I would assume the charge would be from alternator 24V and shore power 240V charger. 24V thrusters with battery banks for bow and stern separately or hydraulic thruster powered with a 24V battery bank? How did you charge the batteries before? A 49' Selene has several battery banks over and above the house bank. One alternator or two alternators on the engine?

I am in the beginning stages of changing lead acid to Lithium for my house bank. My boat being much smaller so it is a simpler install. 120V AC, 12V DC, Start, alternator, thruster, charger and inverter. Charging source, alternators (two engines),600W solar Victron 100V50A solar charger, Pro Mariner 30 amp three output and 50 amp smart IP43 12V/50amp Victron.
*Pro Mariner = ( Port start) (Starboard start) (Bow thruster) batteries
*Victron Solar charger = House 480 ?? AH LifePO4
*Victron Smart IP43 = 12V/50amp-House LifePO4
*Port Alternator = (Port start), (Bow thruster battery)- Blue sea ACR,( House LifePO4)-*Victron-DC to DC 12/12/30amp
*Starboard Alternator= ( Starboard Start) (House Life PO4) Victron DC to Dc 12/12/30amp

*3000W Kisea inverter that powers the 30 amp 120V electrical panel. The inverter DC power comes from the House battery bank. Most of the house users will be powered by the house bank.

*(3) bilge pumps, shower sump, oil change pump have are separated in DC distribution breaker panel and powered by the port engine battery.
*high water alarm and pump, Helm ( includes all electronics, nav lights, helm breaker panel and accessories, wiper, engine compartment blowers, Fireboy are powered by the starboard engine bank.

Engine batteries- four lead acid flooded group 31 (DC) 750CCA 105AH wired in parallel. Two per engine.

Bow thruster bank- One 4D (DC) 1250 CCA 180AH
All lead acid batteries East Penn

Installed a manual on/off cross over battery switch between the port engine battery and starboard engine. There is also a electric solenoid switch at the helm that can be used. "Redundancy"

Installed a manual on/ battery 1/battery 2/ both/ off - thruster bank to port engine bank or to starboard engine bank or both engine banks and thruster bank combined. "Redundancy"

House bank (LifePO4) I have not purchased them yet. I'm still evaluating best batteries for the money. This seems to be changing by the day. ABYC seems to be embracing the idea more and there seems to be more batteries introduced that meet the ABYC recommendations. The prices are coming down and the capacities going up. My goal is to have 500 to 600 AH capacity for DC12V house panel and inverter.

Obviously my system is a simple install compared to what would be found in a 49 Selene. My goal is to keep stored DC energy to DC power users. I am not a fan of using an AC source powered from a stored DC source to then convert it back to DC stored source. That is not an efficient use of energy. I realize having a bow thruster bank in bow of a 50' boat and a stern thruster bank in the stern of that same boat can be a charging issue. Installing a separate 120V/240V charger at each location and relying on an inverter to charge the banks is IMO not efficient. I would install a DC to DC charger using the engine alternator/cranking battery as the charger source. When you are underway making way the thruster bank will be getting charged. When the boat plugged into shore power the thruster bank will be getting charged from the engine battery that is charged from the engine 120V/240 battery charger. When you start your generator the thruster battery will be charged the same way. I would not invert DC stored energy to AC to convert AC to DC to charge a battery bank. Not efficient use of stored energy.

If this is what you have now and it works use it.Its just not efficient. My goal using solar and lithium is efficiency. I'm not waisting one amp if I can help it! Good luck on your install. It sounds impressive I would be interested in seeing the install. Post some pictures. I love the look of all that Blue!
Brian

 

[Jeff F]

Owner connected his stern thruster batteries into the house so he gained more Ah without needing additional space as the battery compartment was already there. Now he runs his stern thrusters off the house and doe not have a separate bank any more. His calculations were that the 10 or 15 second burst of the thruster would not significantly deplete the lithium house and it charged up quickly from what ever source is charging the house (alternator, shore, genset, solar).

It's certainly true that the total power required by the thrusters is small relative to the house bank capacity.

In most cases the challenge is delivering the high amperage required by the thrusters. Longer cables mean more losses at high current. Typically batteries are placed close to the thrusters to minimize the cabling loss and ensure the thruster is getting full power.

What is your house bank voltage and thruster HP? That will determine current requirements for feeding the thrusters, which will dictate wiring/battery requirements.

 

[dmbraaten]

Thank you all for your generous thoughts on this. Attached is the latest schematic I am working with and the only changes (for now) are the IP43 AC/DC chargers that I will use for the stern and bow thruster banks. The 3-way version is shown and I will get the 1 x 1 version instead. This will give me one charger per bank so if something goes awry, I know where to look. Also I will remove the Buck Boosters as I will be replacing my alternator with a Balmar 97XD-24-190-K6 and a Wakespeed WS 500 external regulator which will give solid/steady current making the Buck Boosters redundant. Lastly, I will use a third IP43 1 x 1 charger for the engine bank as well. I will leave the Genset to charge the generator batteries so they will not have another charging source. Thus, the alternator, Generator, shore power, and little solar I have will charge the house bank. all other batteries (except for the genset) will be charged using IP43 AC/DC chargers (stern/bow thruster banks and the engine).

I will change the thruster battery banks to 4 Optima YellowTop D31T in series and in parallel (I have a 24v system and thrusters). These will give 900 CCA. Currently I have deep cycle AGMs which I think Selene put in most boats. So I am moving to a starting battery for the thrusters. The Engine and Genset banks will stay as they are 2 12v 200Ah AGM in series.

My goal is to finalize this draft schematic in the next week or so and then order parts. Hope to be starting on the refit by 3rd week of Feb and will keep you posted.

Again, thank you all for you posts which have really given me a better perspective!