50 amp single cord. Has 2 120V hot legs out of phase, A common that isn't used, and a ground that only grounds the isolation xfmr core. All of the devices on the boat are off the 18KVA isolation transformer; nothing is direct to the shore power.
Replace genset with lithium batteries and a inverter...
- Thread starter Grateful Escape
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@jmauld - A potential issue with Lithium and bow thruster and windlass is the electrical current availability. Lithium batteries can deliver such high current that motors with brushes tend to fail the brushes often. The brushes simply can't manage the current and they get smoked. The good thing is the long run in the cabling from the batteries to the motors which carries electrical resistance buffering the current from the batteries.
We were considering Maxwell Ultracapacitors for engine starting concurrent with the lithium bank for reliability. The Ultracapacitors deliver such high current that the 4/0 wires need to be reduced to 2ga between the capacitors and starter motors to keep from blowing the brushes out.
Just another detail that needs consideration.
We were considering Maxwell Ultracapacitors for engine starting concurrent with the lithium bank for reliability. The Ultracapacitors deliver such high current that the 4/0 wires need to be reduced to 2ga between the capacitors and starter motors to keep from blowing the brushes out.
Just another detail that needs consideration.
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- Jun 5, 2016
- 5,612
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- 410 Sundancer
2001
12" Axiom and 9" Axiom+ MFD
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I have to manually select select shore power or generator, but if neither source is present the inverter automatically powers the Port, Starboard, Galley, and Microwave circuits.
Is that from our original design six or seven years ago? In many ways I miss the simplicity of my 400DA....
- Jun 5, 2016
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Yes. I used Tom's schematic to power the 4 circuits mentioned above.
Here's the thread --> http://clubsearay.com/index.php?threads/inverter-install.89992/
Good point. Is there the same concern if you're using, say three Group 31's in parallel with 2400MCA, with the engine starter brushes?
- Jun 5, 2016
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If your Stage 1 is to just add a LFP house bank, I would buy one of the commercially available LiFePO4 batteries recommended Will Prowse. The SOK marine grade would be high on my list, but there are others, and the prices have come way down, and the quality way up in the last year to the point building out of cells isn’t necessary.
Buy a 200Ah or two 100 Ah, then add a dedicated charger and a DC-DC charger to the existing batteries. All in probably about $1500.
You could add the inverter/charger later and have that take over the charging of the LFP bank, and power 4-5 AC circuits automatically.
Buy a 200Ah or two 100 Ah, then add a dedicated charger and a DC-DC charger to the existing batteries. All in probably about $1500.
You could add the inverter/charger later and have that take over the charging of the LFP bank, and power 4-5 AC circuits automatically.
It seems to me that the internal resistance of the lead acid batteries would buffer the energy surge. I know it's an issue with the capacitor starting batteries. Re-thinking the lithium it would depend upon the BMS and how many BMS in parallel in conjunction with the current the brushed motor will take (it's measured resistance which is very low). My understanding from discussions with Maxwell (I'll have to dig up the correspondence) but the brushes are the "weak link". This may be one of the issues the designers are concerned about in my configuration and why they do not want my lithium bank to be my engine starting batteries. I do know they are also concerned about the loss of starting capability in the event of cascading BMS trips.... I'm thinking outside of the box here. Where I'm going is @jmauld was considering locating his lithium batteries next to the bow thruster to reduce cable length which may not be to his benefit....
jmauld
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When you put the batteries in series with each other, the effective internal resistance is lowered, so KM has a point. If you powered a thruster from a large enough bank of AGM, the thruster could see the same “battery resistance”.
I’m looking into the brush issue. There seems to be a lot of this discussion in regards to trolling motors, but nearly all of those guys have switched over to lithium at this point. I would expect that those motors were BLDC at this point but there is a bunch of them taking photos of brushes and sharing them.
I can certainly see a case where installing a lifepo4 on an old system would accelerate the death of old brushes.
I was thinking about yanking the vacuum and using that space for my house battery. This is about 15’ away from the bow thruster. I could also put a couple of loops in the cable to add some resistance. And to monkey around with nearby compasses.
I’m looking into the brush issue. There seems to be a lot of this discussion in regards to trolling motors, but nearly all of those guys have switched over to lithium at this point. I would expect that those motors were BLDC at this point but there is a bunch of them taking photos of brushes and sharing them.
I can certainly see a case where installing a lifepo4 on an old system would accelerate the death of old brushes.
I was thinking about yanking the vacuum and using that space for my house battery. This is about 15’ away from the bow thruster. I could also put a couple of loops in the cable to add some resistance. And to monkey around with nearby compasses.
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jmauld
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I know I know, but I hate myself and want to make sure I carry too many projects.
The SOK marine battery is out of stock. I would need two (maybe 3) of either the SOK or the Chins batteries, due to the limitations of the BMS that they use in their batteries. Also, If you watch Will open these batteries it doesn’t seem like any of them are using compression on the packs. Granted, I wasn’t paying close attention to that when I watched his videos the first time so maybe I just overlooked it.
jmauld
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@ttmott have you spent any time at the diy solar forums? There seem to be a a lot of boaters there and few of them are using lifepo4 packs as starters although the vast majority are not.
I have; the jury is still out. I had a conversation with a fellow named Denis Phares early last year on using Battle Born/Firefly GC3 lithium batteries for starting; he doesn't think it a problem as long as there is significant margin from the BMS limitations and current is equally drawn from each in the bank to prevent BMS cascading issues. On the other side the EE's that are / have been finalizing my design do not want engine starting on the lithium batteries. I'm still in a quandary as I want to eliminate the 8D batteries on the boat.
- Jun 5, 2016
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Guys are upgrading the SOK marine batteries with a different BMS. Forum has some info on that.
Compression is a whole other matter. After reading and fretting about it, I finally just built the battery. In reality if I get 1/2 the advertised life, it’s still a lifetime battery to me. I’m pretty sure they do better than 50% life.
jmauld
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Doing some reading on that site there are some that are bypassing the ability of the BMS to disconnect the load from the battery. Likely addressing the alternator concerns. Not so sure I would be comfortable doing that. I want to see manufacturers incorporating lifepo4 batteries in this manner before I would take that leap.
For now, I think I will focus on these stages:
Stage 1: all non mission critical DC loads, bow thruster and windlass on a house battery. I’ll leave the rest of the helm DC on the starter bank. Charge house battery with a dc-dc charger and a basic ac-dc lithium charger.
Stage 2: reduce the current 4 LA batteries to 2. Either with a single two-battery starter bank or with two one-battery starter banks. I may leave as two independent banks so that I don’t have to deal with two alternators fighting. This seems small but there are some loads that I need to shuffle around at the helm and I would want to make certain that there is no accidental connections between the starter and house banks. I would use a solenoid between the house and starter bank as an emergency start.
Possible Stage 3: add enough lifepo4 capacity and an inverter to power the AC overnight. I think I’ve determined based on my usage that I don’t really desire an inverter except to use the hvac. I should be able to update the TVs to use dc at some point, and the fridge/freezer already can. If I’m using the stove or microwave I can just run the generator.
For now, I think I will focus on these stages:
Stage 1: all non mission critical DC loads, bow thruster and windlass on a house battery. I’ll leave the rest of the helm DC on the starter bank. Charge house battery with a dc-dc charger and a basic ac-dc lithium charger.
Stage 2: reduce the current 4 LA batteries to 2. Either with a single two-battery starter bank or with two one-battery starter banks. I may leave as two independent banks so that I don’t have to deal with two alternators fighting. This seems small but there are some loads that I need to shuffle around at the helm and I would want to make certain that there is no accidental connections between the starter and house banks. I would use a solenoid between the house and starter bank as an emergency start.
Possible Stage 3: add enough lifepo4 capacity and an inverter to power the AC overnight. I think I’ve determined based on my usage that I don’t really desire an inverter except to use the hvac. I should be able to update the TVs to use dc at some point, and the fridge/freezer already can. If I’m using the stove or microwave I can just run the generator.
Stage 3 - They measured 36 amps at 220 VAC inrush for the 18K BTU AC unit on my boat. That is a whopping 8KW (660 amps at 12 volts). The softstart cut that in half but still, know your loads.... Where I'm going with this is, for me, to run the AC in the forward stateroom over night, keep the the boat's 4 refrigeration units on, plus operate all other AC/DC loads for 8 hours and still have margin to start the engines is how I got to 1200AH. Even with the math closing I have an Automatic Generator Start integrated with the system.
jmauld
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Yeah, I took your advice and finished my spreadsheet on the loads and that’s when it hit me, that most of my power usage is currently dc, can easily be converted to dc or could be ran off of a cheap plug-in inverter.
The only complication this presents is spending money on a charger that I might eventually replace for a charger/inverter. I might look again for a 3-bank charger that can do LA on two banks and lifepo4 on the third bank. Sounds like that might not exist though
The only complication this presents is spending money on a charger that I might eventually replace for a charger/inverter. I might look again for a 3-bank charger that can do LA on two banks and lifepo4 on the third bank. Sounds like that might not exist though
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jmauld
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This is reassuring. Your load is heavier than mine, and I was calculating that I need 1200AH as well. What duty cycle are you using for your fridge and hvac?
Florida - 70% HVAC cooling, 100% HVAC fan, 70% HVAC Raw Water Pump, 50% refrigeration.
Calculations consider HVAC cooling start and one refrigerator starting simultaneously.
It's that 1000 plus amp inrush possibility that should be of concern on the battery capability. A typical Inverter can manage quite a surge above it's rating but the BMS may not. This is why I am baselining five Battle Born GC3 batteries. Each can manage 300 amps continuous and 500 amps for 20 seconds. That gives me a theoretic 1500 amps continuous with margin up to 2500 amps. The 5KW Victron Quattros (two of them) have a nominal 10KW with a surge to 20KW which is 830 amps to 1600 amps at 12 volts.
So, as you can see here the batteries are not, by a significant margin, the limiting factor. Which is where all of us should be in our designs.
https://1t1pye1e13di20waq11old70-wp...-content/uploads/2021/02/BBGC3-Spec-Sheet.pdf
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jmauld
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Have you considered converting to a dc hvac system?
- Jun 5, 2016
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Right now DC hvac is about 3x-4x more expensive. My bet is this becomes more mainstream over the next couple years and price come down, but for now it's a pricey option.
