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Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion?(LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...
Any advice much appreciated,
Jim
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Interesting.? I have four 100Ah LiFePO’s in series running my motor.? My no-load voltage after charging is around 53.8 volts.? I believe that to be normal.? If you read your meter correctly, I am at a loss as to where the extra 4.5 volts would come from.? Maybe your batteries have an extra cell in them?? ? Pat ? ?? ?
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From: [email protected] < [email protected]> On Behalf Of James Jones Sent: Tuesday, September 13, 2022 12:55 PM To: [email protected]Subject: [electricboats] Maximum input voltage for outboard? ? Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion?(LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...
Any advice much appreciated,
Jim
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LiFePo “12v” batteries typically reach 100% capacity with about 14.4v (e.g. this one: ? ) ? And so, 4 of these in series ~ 57.6v.? Ones with built-in BMS often allow charging voltage to be as high as 16v (internally bypassing or otherwise limiting the charge voltage on the cells).? So, it seems normal to see about 58v in your case (or 3.6vpc) and would be close to 100%SOC. ? If instead you charged to just 3vpc (for 48v total), you probably only get to 2-3%SOC: ? Now, if you need to limit to 55v, that would be 13.75v per battery or about 3.44vpc.? This still should be about 99%SOC, so you should be good. ? I recommend you reduce the CHARGE VOLTAGE from your charger if possible. ? -Myles ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of James Jones
Sent: Tuesday, September 13, 2022 9:55 AM
To: [email protected]
Subject: [electricboats] Maximum input voltage for outboard? ? Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion?(LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...
Any advice much appreciated,
Jim
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58.4 is a fully charged lifpo4 48v system (16s) I would be pretty surprised if you had anything other than 16s or your case two 24v (8s) in series.?
I don't have any specific knowledge of that motor but I would also be surprised if it was not designed to work with lifepo4 16s.?
Maybe your meter is faulty? maybe there was miscommunication??
What does concern me is the 58.3 volts. It should only be at that high of a voltage when charging and only for a short period. Resting voltage should be around 53-54 volts.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Tuesday, September 13, 2022 at 01:20:50 PM EDT, greenpjs04 <forums@...> wrote:
Interesting.? I have four 100Ah LiFePO’s in series running my motor.? My no-load voltage after charging is around 53.8 volts.? I believe that to be normal.? If you read your meter correctly, I am at a loss as to where the extra 4.5 volts would come from.? Maybe your batteries have an extra cell in them?? ? Pat ? ?? ?
From: [email protected] < [email protected]> On Behalf Of James Jones Sent: Tuesday, September 13, 2022 12:55 PM To: [email protected]Subject: [electricboats] Maximum input voltage for outboard? ? Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion?(LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...
Any advice much appreciated,
Jim
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Nice looking boat!? I would not put a stepdown?converter into it.? Can you maybe get a charger that can be set to charge at 55V instead? That will be better for the LFP cells anyway, you don't get much more capacity by charging them higher than that anyway and it will make them last longer if you limit the charge voltage.? Also in my experience you can run motors at slightly higher voltages without damaging them - just don't run at full speed when the batteries are fully charged - it will very quickly go below the 55V as soon as you start powering the motor, I would guess that within the first 10min or so they will be down under 55V.?
Hi all,
I've just completed building an electric-powered boat, and upon wiring up the batteries found that the voltage at the end of the line (electric outboard power plug) is higher than expected.
My battery bank is four (4) 24v / 75 Ah lithium ion?(LiFePO) batteries, wired with two pairs of batts each wired in parallel, and then series connecting the pairs, which should produce a nominal 48 volts output. The meter however reads 58.3 volts, which is higher than the combined "fully charged" voltage "should"(?) be. Since my outboard (Karvin 6800) has a maximum input voltage of 55 volts, this creates a puzzle. Am I missing something? Do I need to add a component to reduce the output voltage of the batteries? Etc...
Any advice much appreciated,
Jim
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I second Matt's points.? You shouldn't see more than 55V for long with 16S LFP after you stop charging.? Even a small load will bring it right down.? Have you tried connecting it to the motor?? I understand not wanting to damage it, but it *should* protect itself and just not function.? I also have a 16S LFP battery, and my motor tops out at 60V (ePropulsion).? Also, as a test of the meter you're using, see what it says on the output of the charger with no load.? If that's over 58.4V, your meter may be reading high.
Hey James, that's a nice looking cat you have there!? I considered those Karvin motors for mine.? I'd be interested to hear how well they work.? And, I'm in the Seattle area too.? Wondering if we frequent the same waters (Lake Washington/Union and Puget Sound between Seattle and Everett).
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(Martin's post crossed mine.? Agree with those point as well.)
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Thank you all for the info and suggestions!
Turns out that it wasn't the meter (I checked with two different meters), and the batteries themselves are within spec (no extra cells, etc.): Their documented fully charged voltage is 29.4 volts, and each one currently reads 29.1. Which adds up to what I see on the meter for the whole bank: 58.3. Here are the particular ones I'm using:?
They haven't even been plugged into a charger yet; they're still in the "partially charged" shipping condition.
So I guess either these batteries have an atypically high voltage, or the Karvin outboard has a unusually low maximum voltage. Or both. :)
And to answer bobkart's question: I'll definitely post info about how it works when I finally launch the boat in, hopefully, a week or two. And yup, I'm near Lake Washington and will probably launch at Magnuson Park.
Thanks again,
Jim
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That is a decent battery in terms of energy density!
I'm just surprised to see such a high voltage on an LFP battery after sitting for what I'm guessing is many days.? The BMS must not draw very much.
I looked more closely at your pictures, and now see what I suspect is a Star Trek reference in your boat's name.? (We sometimes call our Nissan Leaf the Shuttle Craft.)
According to SOC tables I have, 54V resting voltage is 99% SOC, and 99.5% SOC comes in at 55.2V.? So if you have the option of turning your charger down somewhat, that should alleviate any concern of damaging the Karvin.
Or you could put a small load on the battery for a bit after fully charging to 58.4V.? You only need to bleed off half a percent or so of capacity (~20Wh).? A 75-ohm, 50-watt resistor would do it in just under half an hour (but would likely get pretty hot).
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Hi Jim,?
Now my interest is really piqued!?
There is zero chance your batteries would be sitting at 29 volts in a partial charged state. Even at 100% soc they would fall below 29v within a minute after taken off the charger and they would keep falling 26ish volts. While often not followed,? Lithium batteries are supposed to be shipped at no more than 30% soc, fyi.?
The specs on the link you sent seem perfectly in line with 8s lifepo4. Click on the "Download the Lithium Battery Spec Sheet" link. Scroll down to the Battery Management?System. This is where things get weird. They say per cell "over voltage protection" is 4.3v. This would be a correct (even a little high) for an NMC chemistry battery.? I have seen manufactures?put in? high upper limits to make up for bottom of the barrel cells, but never this high. What's even more concerning is the "over charge release voltage" of 4.1. This means the cell will cycle between 4.1 and 4.3. It should never go above 3.65.?
I would say they just put the wrong specs on this page, but this does not explain your abnormally high voltage. You either have an unusual number of cells in series (highly doubtful) or these cells are actually NMC or some other chemistry.?
?I would get them on the phone ASAP and not charge these until they can explain. If they give you a run around I would gladly talk to them for you.?
Matt Foley? Sunlight Conversions Perpetual Energy, LLC 201-914-0466
On Tuesday, September 13, 2022 at 06:35:17 PM EDT, James Jones <jgjones252@...> wrote:
Thank you all for the info and suggestions!
Turns out that it wasn't the meter (I checked with two different meters), and the batteries themselves are within spec (no extra cells, etc.): Their documented fully charged voltage is 29.4 volts, and each one currently reads 29.1. Which adds up to what I see on the meter for the whole bank: 58.3. Here are the particular ones I'm using:?
They haven't even been plugged into a charger yet; they're still in the "partially charged" shipping condition.
So I guess either these batteries have an atypically high voltage, or the Karvin outboard has a unusually low maximum voltage. Or both. :)
And to answer bobkart's question: I'll definitely post info about how it works when I finally launch the boat in, hopefully, a week or two. And yup, I'm near Lake Washington and will probably launch at Magnuson Park.
Thanks again,
Jim
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Good call Matt, looking at the spec sheet.? I only looked over the specs on the main product page.
So they say "built on patented Lithium Iron Phosphate (LiFePO?)?chemistry" on the main product page, but then say "built on patented Lithium Iron Manganese Phosphate chemistry" on the spec sheet.? The latter seems to have too many ingredients in it.? I do notice that 7 x 3.7V nominal is the 25.9V nominal they claim on the spec sheet.? That's consistent with a 7S NMC arrangement.? 8S LFP would come to 25.6V nominal.? NMC would also explain the apparent great energy density (for LFP) that I noticed.? No trouble at all to get that energy density with NMC.
You should definitely follow up on this with the supplier.? Easiest way to answer the question would be to open the case, but that's likely going to void the warranty and compromise the case waterproofness.? X-Ray perhaps?
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An update...
I communicated with both the outboard maker ("Don't exceed 55 volts. Seriously. Warranty is void if you do."), and the battery folks ("Battery is within specs, will try to find a solution, [e.g.: voltage regulator, buck converter, etc.]" but after talking to their tech as he searched, it doesn't appear that any off-the-shelf item which doesn't cost heaps of money has the right voltage and amperage range. (Matt: many thanks for the info and offer to talk to them. I didn't really dig into the details with them (cell voltage protection, etc.), but they didn't give me any runaround, and I think they did their best to be helpful.)
So... unless I can find a reasonable alternative, I'll go to plan B: Since this outboard can use 24, 36 or 48 volts, I'll rewire the batteries in parallel to make a 24 volt bank, rewire solar panels to output 24 volts, and buy a new 24 volt charger. My solar controller is also multi-voltage. This will, I imagine, reduce the maximum power of the outboard, but realistically I don't think I'll be unhappy with the speed from 24 volts if I every have to floor it. :)
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Too bad about that 55V limit.? I believe them when they say that the battery is within spec, but I'm thinking that's because it uses NMC cells (7S) as opposed to LFP (8S) .
NMC would explain the stated nominal voltage (7 x 3.7V = 25.9V).? LFP would be 8 x 3.2V = 25.6V.? NMC also explains the light weight.? 27 pounds for ~1,940Wh of LFP is significantly better than any other 'packaged' LFP battery I've found, but no problem for NMC.? NMC also explains the staying around 55V for much longer than LFP would.
The only downside to those batteries being NMC instead of LFP, other than (in your case) the slightly-higher resting voltage after fully charging, is the increased chance of thermal runaway.? So something to be mindful of.
As you suspect, you'll get only half the 8hp they'd deliver at full voltage.? Upside is your full-power runtime (without panel assistance) will double, and the panels will fill in for a greater portion of your consumption.? Depending on how happy you are with the resulting speeds, you could consider a 15S LFP battery, as that has a maximum voltage of 54.75V.
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Why not just change your charge controller and charger to stop charging at 54 volts and keep using the batteries that you already have. ?There is almost no useful Wh at the very top and bottom of lithium batteries. ?And as a plus, under charging them will add years to there useful life.
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On Sep 20, 2022, at 12:35 PM, James Jones <jgjones252@...> wrote:
?An update...
I communicated with both the outboard maker ("Don't exceed 55 volts. Seriously. Warranty is void if you do."), and the battery folks ("Battery is within specs, will try to find a solution, [e.g.: voltage regulator, buck converter, etc.]" but after talking to their tech as he searched, it doesn't appear that any off-the-shelf item which doesn't cost heaps of money has the right voltage and amperage range. (Matt: many thanks for the info and offer to talk to them. I didn't really dig into the details with them (cell voltage protection, etc.), but they didn't give me any runaround, and I think they did their best to be helpful.)
So... unless I can find a reasonable alternative, I'll go to plan B: Since this outboard can use 24, 36 or 48 volts, I'll rewire the batteries in parallel to make a 24 volt bank, rewire solar panels to output 24 volts, and buy a new 24 volt charger. My solar controller is also multi-voltage. This will, I imagine, reduce the maximum power of the outboard, but realistically I don't think I'll be unhappy with the speed from 24 volts if I every have to floor it. :)
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I would second this approach, it would lengthen the life of batteries and not require any additional reconfiguration.?
On Tue, Sep 20, 2022 at 7:34 PM James Sizemore < james@...> wrote: Why not just change your charge controller and charger to stop charging at 54 volts and keep using the batteries that you already have.? There is almost no useful Wh at the very top and bottom of lithium batteries.? And as a plus, under charging them will add years to there useful life. ?An update...
I communicated with both the outboard maker ("Don't exceed 55 volts. Seriously. Warranty is void if you do."), and the battery folks ("Battery is within specs, will try to find a solution, [e.g.: voltage regulator, buck converter, etc.]" but after talking to their tech as he searched, it doesn't appear that any off-the-shelf item which doesn't cost heaps of money has the right voltage and amperage range. (Matt: many thanks for the info and offer to talk to them. I didn't really dig into the details with them (cell voltage protection, etc.), but they didn't give me any runaround, and I think they did their best to be helpful.)
So... unless I can find a reasonable alternative, I'll go to plan B: Since this outboard can use 24, 36 or 48 volts, I'll rewire the batteries in parallel to make a 24 volt bank, rewire solar panels to output 24 volts, and buy a new 24 volt charger. My solar controller is also multi-voltage. This will, I imagine, reduce the maximum power of the outboard, but realistically I don't think I'll be unhappy with the speed from 24 volts if I every have to floor it. :)
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I've pursued the idea of having the battery charger top out at <= 55 volts, which would indeed be a great solution, but after much searching I'll be darned if there's a lithium ion battery charger out there which is small-ish, of reasonable cost, and has a suitable adjustable voltage range and adjustable amperage (or is limited to <= 15 amps).?
Victron makes what would be the perfect charger but it sadly isn't available in a 48 volt version.
So, just thought I'd ask if anyone might have knowledge of, or an idea where to look for, such a charger. :)
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If you're looking for a 'shore-power' charger (as opposed to a solar charge controller), I'm using the Meanwell HLG-600H-54A (two actually) on my 16S LFP pack:
The CV output voltage is adjustable (on the 'A' model).? The specs claim 11.2A CC output current, but in practice I see more like 12A.
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It might work better to have a pair of 27V chargers, so the two batteries stay balanced better as they charge.
This could work even if you're asking about solar charge controllers, with the obvious downside of needing two (and an even number of solar panels).
For charging at home, even one 27V charger can work, by moving it from one battery to the next after the first one is full.
Without splitting the charging like that, you might need something like the HA01 battery balancer, although that's for a pair of 12V-nominal batteries as opposed to 24V.
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Have you thought of removing one cell, reducing your high-end voltage?
Best wishes,
Reuben Trane
Mobile: 786.303.1013
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I guess the reasonable cost is up for debate but they have e-bike chargers that you can set to only charge to 80/90/100 percent that go for around $100-$200. Here is a link to listed for $95 that charges at the following levels: ?80% (52.8V), 90% (53.8V), 100% (54.6V).?
Some Choices:
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I've pursued the idea of having the battery charger top out at <= 55 volts, which would indeed be a great solution, but after much searching I'll be darned if there's a lithium ion battery charger out there which is small-ish, of reasonable cost, and has a suitable adjustable voltage range and adjustable amperage (or is limited to <= 15 amps).?
Victron makes what would be the perfect charger but it sadly isn't available in a 48 volt version.
So, just thought I'd ask if anyone might have knowledge of, or an idea where to look for, such a charger. :)
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bobkart
Reuben Trane