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House systems - separate or together with drive system?
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I am at the beginning of a conversion for a 32’ ketch, and I have the 10kw thunderstruck kit, charger, reduction, and battery bank all working on my bench under artificial load. She will be at a dock soon where I can pull the diesel and begin refitting with the EV drive.
The boat has an existing house system with four 6v golf cart batteries in 2p2s for both the 12v house loads and the starting motor, along with two 50w solar panels and a charge controller. During the summer in the Pacific NW the solar keeps up with the house loads at anchor all summer, she is usually at a dock plugged in for much of the winter. I originally intended to leave all the existing 12v system in place, and keep the 48v ev system separate, but I’m realizing that once the old motor comes out, it’s really prime time to simplify as many things as possible, so I’m wondering about the necessary equipment and pros/cons of running the house load off of the same battery bank as the EV (right now I am working the EV with 4x 12v 200ah AGM in 4s). What becomes complicated or inefficient about running them together (with a 48v to 12v step down) vs having separate systems? I halfway thought that I would try leaving the existing house system as-is, adding the EV with the AGM bank separately, and if it is all working well, then switching the EV drove to a m bank of lifepo4 and rewiring the AGM bank in 4p at 12v, replacing the older system which is nearing end of life in the next few years anyway. But I also am drawn to the simplicity of only having one set of batteries to worry about for all loads. What are the practical considerations that you guys have encountered for each scenario? My boat will mostly be used for crushing near shore, likely with power though most winters, and at anchor or underway in summers. |
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Wow, I apologize for not editing for autocorrect typos. Hopefully the ones below make sense in context.
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On Jun 24, 2020, at 22:42, Ryan Sweet via groups.io <ryan@...> wrote: |
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Ryan, How much house power do you need, and what is the relative balance of motor power vs. house power? If the house requirements are tiny, then running a converter to regulate the 48V down to 12V may be a good answer.? On my small boat, this is what I have done - at least for now. If your house requirements are large, then getting a sufficient regulator becomes more of an issue. You might also consider how "critical" each supply is.? One reason house banks are kept separate from starting battery banks on many boats is to prevent the owner from accidentally running down the battery so far that he/she is no longer able to start the main engine.? ?In your case - would you want separation of the banks so that you didn't accidentally run down the power so much that you couldn't get home? If you have a backup generator - then that is much less of a problem. One other option is that if your house needs are small enough, you could consider a separate house bank - but keep it at 48V and use a regulator anyway.? That would allow you to have the house bank and the motor bank both at 48V, so that your house bank could be a "backup" for your motor, if anything bad happened to your main motor bank (i.e. if you ran it down unexpectedly). Ultimately, it's a judgement call for you.? As with so many engineering problems - there are many answers.? Some less efficient, and often no single obvious perfect answer. John
On Thursday, June 25, 2020, 12:46:09 AM CDT, Ryan Sweet <ryan@...> wrote:
Wow, I apologize for not editing for autocorrect typos. Hopefully the ones below make sense in context. > On Jun 24, 2020, at 22:42, Ryan Sweet via groups.io <ryan=[email protected]> wrote: > > ?I am at the beginning of a conversion for a 32’ ketch, and I have the 10kw thunderstruck kit, charger, reduction, and battery bank all working on my bench under artificial load. She will be at a dock soon where I can pull the diesel and begin refitting with the EV drive. > > The boat has an existing house system with four 6v golf cart batteries in 2p2s for both the 12v house loads and the starting motor, along with two 50w solar panels and a charge controller. During the summer in the Pacific NW the solar keeps up with the house loads at anchor all summer, she is usually at a dock plugged in for much of the winter. > > I originally intended to leave all the existing 12v system in place, and keep the 48v ev system separate, but I’m realizing that once the old motor comes out, it’s really prime time to simplify as many things as possible, so I’m wondering about the necessary equipment and pros/cons of running the house load off of the same battery bank as the EV (right now I am working the EV with 4x 12v 200ah AGM in 4s).? > > What becomes complicated or inefficient about running them together (with a 48v to 12v step down) vs having separate systems? > > I halfway thought that I would try leaving the existing house system as-is, adding the EV with the AGM bank separately, and if it is all working well, then switching the EV drove to a m bank of lifepo4 and rewiring the AGM bank in 4p at 12v,? replacing the older system which is nearing end of life in the next few years anyway.? But I also am drawn to the simplicity of only having one set of batteries to worry about for all loads. > > What are the practical considerations that you guys have encountered for each scenario? > My boat will mostly be used for crushing near shore, likely with power though most winters, and at anchor or underway in summers. > > |
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There is added complexity either way you go. The right answer takes into account the peak and continuous loads for the 12v. For me, the biggest load is the anchor windlass at <80 amps. So, a pair of Thunderstruck 50 amp DC-DC converters was the simplest approach. BTW, my propulsion batteries are 96v. If my peak current had to include a starter motor then DC-DC converters probably wouldn't be as good a choice and a separate 12v battery + charger would be better. I do have a portable 12v battery plus charger for my tender that can also be tied in for 12v emergency power should the main system fail.
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Here’s my latest thinking for my 12m eCat. I have my main 48VDC LFP pack charged by solar and a 12v battery for house loads. The 12v has a stand alone solar panel and controller PLUS a 48v/12v charger I just installed. I also use dc/dc converter/power supplies for additional 12v needs. I can get you info in the charger if you’d like.? |
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??Hello Ryan! Good name! I'm Ryan also.?
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On my setup, I knew that my house requirements were sufficient to really need their own bank, so I have 2 qty Grp 27 deep cycles in parallel, and seperable by means of a 3-way batter switch. I did this for the reason previously stated, as to be able to isolate a starting battery for the main engine, in my case an old evinrude 140 converted from b.s. vro to mix.? The 48v bank for auxillary propulsion is chargeable by 4 qty 100w 12v renology panels, and by a small honda 2200w inverter generator pushing a 48v 25a switching power supply, isolated from the solar cells by large blocking diodes, and being fed parallel into a large analogue relay controlled by a charge controller.? I ended up getting an "intelligent" 25a 48v to 12v nominal converter and just putting it between them, and thus far it has worked just fine. It simply makes more sense, with my setup anyway, to charge the propulsion bank directly and have keep the house bank topped off. I have to be trying hard to pull 30a from it, except of course when starting the motor; and so the propulsion bank makes the cycle rate on my house bank pretty much non existent when at anchor, and when underway, between the solar array and the little genny, it keeps my big bank pretty stable unless I am at full throttle on the electric outboard and running everything imaginable on the house bank
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??Hello Ryan! Good name! I'm Ryan also.? On my setup, I knew that my house requirements were sufficient to really need their own bank, so I have 2 qty Grp 27 deep cycles in parallel, and seperable by means of a 3-way batter switch. I did this for the reason previously stated, as to be able to isolate a starting battery for the main engine, in my case an old evinrude 140 converted from b.s. vro to mix.? The 48v bank for auxillary propulsion is chargeable by 4 qty 100w 12v renology panels, and by a small honda 2200w inverter generator pushing a 48v 25a switching power supply, isolated from the solar cells by large blocking diodes, and being fed parallel into a large analogue relay controlled by a charge controller.? I ended up getting an "intelligent" 25a 48v to 12v nominal converter and just putting it between them, and thus far it has worked just fine. It simply makes more sense, with my setup anyway, to charge the propulsion bank directly and have keep the house bank topped off. I have to be trying hard to pull 30a from it, except of course when starting the motor; and so the propulsion bank makes the cycle rate on my house bank pretty much non existent when at anchor, and when underway, between the solar array and the little genny, it keeps my big bank pretty stable unless I am at full throttle on the electric outboard and running everything imaginable on the house bank |
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This is the converter I used. Works fine for me, as I don't really have any real heavy draw stuff on my 12v house bank like wenches etc; but it should still work fine to fill the house bank back up after occasional intermittent heavy amp draw use.?
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A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually “killed” the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can’t handle the higher amp loads.?
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开云体育There’s another consideration here: the house battery ‘type’. What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or…).? Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down). However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.? Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.? In fact, the lifetime of the batteries is improved by keeping the voltage lower, so…? And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you’d be just fine. ? From: [email protected] [mailto:[email protected]] On Behalf Of Reuben Trane via groups.io ? A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually “killed” the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can’t handle the higher amp loads.? |
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Myles, I'm following what you're saying, and appreciate improving the life of the lithium battery by not fully charging it to the max allowed voltage.? But would you be giving up a significant portion of the battery capacity? And I guess all of this depends on the exact details... There was one "12V" Lithium battery I peeked at: It's rated for a max charging voltage of 14.4V, with a standby voltage of 13.8V. So I guess if your "48V to 12V" converter actually put out 13.5V (typical of many automotive systems),? then you'd probably be in pretty good shape. If it only put out a true 12V, then your 50Ah battery (from above example) would never get close to being fully charged, and you'd get a significantly reduced fraction of the 50Ah life out of it before needing more charging. Right? John
On Friday, June 26, 2020, 11:03:56 AM CDT, Myles Twete <matwete@...> wrote:
There’s another consideration here: the house battery ‘type’. What Reuben says is correct if one is using PbA batteries for the house battery (12v or 24v or…).? Lead acid batteries need to be charged much higher than their nominal voltage rating and need to ramp the charge current down as that voltage gets near the end and then halt current (or possibly provide a trickle or maintenance charge after cooling down). However, if instead of PbA batteries, you were using lithium for your house pack and that the lithium battery was rated, say, as a replacement for 12v (PbA) batteries.? Most of these are rated to 14.4v or so and there is no penalty at all in charging them only to 12v.? In fact, the lifetime of the batteries is improved by keeping the voltage lower, so…? And so, in the case of lithium batteries used as the house battery, you would not need (nor maybe would it be advisable) to use a 48vDC-12vDC charger unit (unless it were configurable for lithium) but simply use a 48/12v DCDC and you’d be just fine. ? From: [email protected] [mailto:[email protected]] On Behalf Of Reuben Trane via groups.io ? A DC/DC converter (power supply) is NOT a charger. I mistakenly did the same as you, using DC/DC converters hooked up to my 12v batteries (2 separate systems). They eventually “killed” the batteries. That is why I researched the DC/DC battery charger. It works as a constant source of 12v while charging the battery. That power supply you bought works w/o a battery supplying a constant 12v. I use 500w Mean Well 48v/12v to supply 2 of my 12v panels. And I have 48VDC/12v battery chargers going to 12v batteries - one for the panel with the windlass (hi amps) and one to the panel with the generator (ditto). My DC/DC converters can’t handle the higher amp loads.? |
开云体育One of the best sites I have seen can give you a pretty good answer for LiFePo, for how much total capacity lost for each voltage cutoff. ?For example at 3.6 volt per cell will only cost you a max of 2%. ?That would be around 14.4 volts for a 12 volt equivalent, or 57.6 for 48 volt equivalent. ? You can run the math for other cut off points.? ? On Jun 26, 2020, at 12:13 PM, john via groups.io <oak_box@...> wrote:
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开云体育? Thank you everyone for all of the answers! In the end I think I like the idea of having one set of inputs (shore power/solar) and two banks (house/drive system), and some way to use the house system as a backup.? Either way I think the biggest challenge I’ll have is cleaning up all of the apocryphal wiring from 50 years of lighting and equipment that has evolved over the lifetime of the craft.?
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Randy Cain
Reuben Trane