T-Pain Is On A Boat: June 2022

Monday, June 27, 2022

Re: [electricboats] 48V 10kW vs 20/30hp ICE

Ray4boat@yahoo.com

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On Monday, June 27, 2022, 6:15 PM, Reuben Trane via groups.io <rjtrane=me.com@groups.io> wrote:

The power/speed curve shows empirical sea trial data plus tank test. Originally we had 75HP Steyr diesels with 7kW motor/generators driving props thru ZF Saildrives.

I replaced that system with a pair of 10kW PMAC 48v motors with 3:1 reduction and straight shafts.

convert current HP motor to kW and you may get some info from these curves. The red line is from sea trials when brand new. The Ossa curve is at design weight and matches tank test closely.

Sunshine is a 12m cat weighing a bit more than 20,000#.

Re: [electricboats] 48V 10kW vs 20/30hp ICE

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

The power/speed curve shows empirical sea trial data plus tank test. Originally we had 75HP Steyr diesels with 7kW motor/generators driving props thru ZF Saildrives.

I replaced that system with a pair of 10kW PMAC 48v motors with 3:1 reduction and straight shafts.

convert current HP motor to kW and you may get some info from these curves. The red line is from sea trials when brand new. The Ossa curve is at design weight and matches tank test closely.

Sunshine is a 12m cat weighing a bit more than 20,000#.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

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Re: [electricboats] Server Rack Batteries

Bob,
Think it's the older one. He uses that motor everyday for last 2 years. He replaced bearing in the field. One thing he said was after you change bearing be very careful about putting it back together. The magnets are very powerful and it really snaps together hard. Fingers!
Jerry

On June 27, 2022, at 12:30 PM, bobkart <couch45@msn.com> wrote:

First I'm hearing of ePropulsion main bearing issues . . . is it the older 3.0 or the newer 3.0 Evo? Or maybe the motor is in the water year-round?

14 knots is a little fast for either the Navy 3.0 or 6.0. Their props are pitched a bit less than that: my top speeds are just under 12 knots. That's one advantage of the Elco: you can use third-party props (I think), and thus have more pitch/etc. selection. You may want to make sure that a suitably-pitched prop is available for the Elco 9.9hp model, for the top speeds you're after.

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Re: [electricboats] Server Rack Batteries

First I'm hearing of ePropulsion main bearing issues . . . is it the older 3.0 or the newer 3.0 Evo? Or maybe the motor is in the water year-round?

14 knots is a little fast for either the Navy 3.0 or 6.0. Their props are pitched a bit less than that: my top speeds are just under 12 knots. That's one advantage of the Elco: you can use third-party props (I think), and thus have more pitch/etc. selection. You may want to make sure that a suitably-pitched prop is available for the Elco 9.9hp model, for the top speeds you're after.

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Re: [electricboats] Server Rack Batteries

Bob,
   Here in St Thomas I have a friend with the epropulsion 3.0. He likes it but had to change main bearing after about a years use. Lots of Torqueedos here as well with corrosion and water intrusion problems. I still might go with epropulsion though.
    The 5 kwh server racks weigh about 100 lbs. I know it's heavier than self made but after building and running a 14 kwh lifepo4 bank for 3 years, I'm hoping the server rack is more plug and play.
     The rack I'm looking at is supposed to be able to able to handle 110 amps continuous so the Elco should work. Of course at full throttle you have at most 45 minutes running time but I shouldn't have to run it that hard. The boat I'm building will plane at 14 knots on a 5 hp gas engine.
Jerry

On June 26, 2022, at 10:44 PM, bobkart <couch45@msn.com> wrote:

I can't address server rack batteries from direct experience. While I suspect they will work from a water-resistant standpoint, a 48V 5kWh model will likely only support 100A continuous discharge, and that will just barely work with the Elco 9.9. Have you looked at the ePropulsion Navy 3.0 Evo? I have the 6.0 model on my five-meter power cat, and it works well. The 3.0 will only need ~62A from your battery, easily handled by a 100Ah LFP battery. And 100Ah is a common and cost-effective LFP size (in 12V nominal configuration), so four of those in series can be easily assembled into a 48V pack, which is then manageable weight-wise, due to the easy decomposition of the pack into ~30-pound pieces.

When I look at server rack batteries, the one spec that usually jumps out at me is weight. Due to the steel-case packaging they typically use, their weight is markedly more than that of an equivalent-capacity battery assembled from modules. Of course individual LFP cells can be used for an even more energy-dense result, as I show in this video:

https://www.youtube.com/watch?v=fmk1_ynLdwI

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Sunday, June 26, 2022

Re: [electricboats] Server Rack Batteries

I can't address server rack batteries from direct experience. While I suspect they will work from a water-resistant standpoint, a 48V 5kWh model will likely only support 100A continuous discharge, and that will just barely work with the Elco 9.9. Have you looked at the ePropulsion Navy 3.0 Evo? I have the 6.0 model on my five-meter power cat, and it works well. The 3.0 will only need ~62A from your battery, easily handled by a 100Ah LFP battery. And 100Ah is a common and cost-effective LFP size (in 12V nominal configuration), so four of those in series can be easily assembled into a 48V pack, which is then manageable weight-wise, due to the easy decomposition of the pack into ~30-pound pieces.

When I look at server rack batteries, the one spec that usually jumps out at me is weight. Due to the steel-case packaging they typically use, their weight is markedly more than that of an equivalent-capacity battery assembled from modules. Of course individual LFP cells can be used for an even more energy-dense result, as I show in this video:

https://www.youtube.com/watch?v=fmk1_ynLdwI

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[electricboats] Server Rack Batteries

     I'm currently building a 12 foot cat dinghy. I've got one Hang Kai 1.2 kw outboard. Initial plan was to gang two together but I'm now leaning towards Elco 9.9 and hanging Chinese motor off back as a spare. While researching Elco motors noticed that 5 hp weighs same as 9.9 hp. Also 24v so doesn't work for me.
    For batteries looking at around 5 kwh Lifepo4 server rack. Need to keep the weight down for servicing these weigh around 100 lbs which is manageable.
   Anyone have any experience with these in a boat? Some are advertised as water resistant but of course not water proof. They will be in sealed compartment anyway but might need ventilation for the temperature.
    I'll keep looking but would appreciate any input. Boat building on hold now till fall when temperature drops. The epoxy cures too fast to work with.
Jerry Barth

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Friday, June 24, 2022

Re: [electricboats] 48V 10kW vs 20/30hp ICE

Hi Larry. Really appreciate your reply. I plan to use the existing sail drive, which is a Volvo SD120S and MS25S existing transmission with ratio of 2.47:1. This gives me max revs at the prop of 1500RPMs and 900RPMs when cruising (or 2200RPMs on the tacho). I am interested in how you plan to connect to your sail drive on your new boat? Cheers and thank again for your comments. Stu

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

I converted my 40ft sailboat from 2 cylinder diesel 28 hp to a Thunderstruck 10kw kit. I used a 48v lead acid for 2 years then converted to a diy 48v 400ah lifepo 4 I installed ANT bms to monitor and program my battery perameters. I was very pleased with the performance and range. The lead acid used more electricity to charge than the lifepo4 I have a new sailboat with sail drive and intend to remove the 30 hp yanmar diesel engine and use a similar kit for the electric conversion. I hope this helps thank you kind regards Larry Schmitz

On Thu, Jun 23, 2022 at 7:59 PM Rumble <rumble@bigpond.net.au> wrote:

Hi, thanks for your information Jeffrey. Even though I have worked the stats on boat sizes v engine sizes etc, I am very happy with my existing 2 x 30hp Volvos in our 35ft 16500lb displacement catamaran. I wouldn't go less. Anyhow, I am starting by replacing one engine and upgrading the alternator on the other, and go from there.
There's plenty of room for 1 or 2 x 300A 48V lithium bank but still tying loose ends with BMS and max amperage types and arrangements. I am sure 12-15kW would probably be more aligned with my existing engine setup, but I can't find much in the 48V range.
GM no longer have a 15kW but recommend the 10kW. Controllers....won't start on these.
Hence my question, as I won't go 72V unless I really need the 12-15kW size. Cheers.

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Thursday, June 23, 2022

Re: [electricboats] 48V 10kW vs 20/30hp ICE

I have converted a 12,500 lb boat to electric replacing a very well matched 23HP diesel with a 12kW water cooled electric motor. I have a lot of detail on my installation here:

http://dan.pfeiffer.net/10m/electric_drive.htm

Look it over. I'll just say a couple things here in response to previous comments...

I would recommend over-building capacity so that at cruise speeds you are operating at about 50-60% capacity. And you can't run too cool. Have as much passive cooling as possible in addition to an active cooling system.

I don't think you would need 15kW to replace a 20HP diesel (if that was a correct match to the boat). I replace 23hp with 12kW and I think 10 might have done it but I wanted more capacity headroom and I wanted water cooling which I got with the Motenergy ME1616 motor. See my details in the link above.

The propeller is very important to get best performance. Bigger and slower is better. Spend some time on this. I have a feathering prop and it can do regen. A folding prop would not. I have seen 500 watts sailing at 6.5-7 knots. It's a bit tricky to keep the throttle adjusted for best output. But a computer could do it pretty easily.

The comment about low RPM torque in the electric as relating to acceleration of the motor is true enough but otherwise basically useless in this application. If you ramp up RPM too fast all that torque is just going into making bubbles and that cavitation is probably pretty hard on the propeller. So the quick acceleration of the motor is not really all that useful if you cant get that power to the water. Like having tiny tires on a 700hp car.

You need to design the driveline system to get the motor operating in it's best efficiency range at cruise speeds. Yes you can get all that torque at half RPM and drive a big prop. But you'll be wasting a lot to heat if the motor is not close to that sweet spot. With the motor I have and similar motors I don't know how you could do it without a reduction gear of some sort. Mine is a 3:1 belt drive. On the diesel it was 2:1 gear. Same max RPM of 2400. So my max prop RPM went from 1200 to 800. The feathering prop has a changeable pitch.

The low speed operation of the motor is a nice advantage over diesel as noted. The low rpm speed of diesel is limited to the idle speed of the engine. 700rpm? The electric is fine down to 1 RPM. As noted it is useful is docking type operations.

Dan Pfeiffer

On 2022-06-23 9:01 pm, Jeffrey Griglack via groups.io wrote:

I replaced my Atomic-4 (rated at 30 hp, but probably, really closer to 20) with a 10kw kit from Thunderstruck. It worked well in my Pearson 30 (30 feet, about 8300 lbs. displacement) sailboat. I was limited by the small battery bank, but it got me in and out of the cove where my mooring is located. I used the same prop that I was using for the A-4.

I since upgraded boats to a Pearson 365 (36.5 feet, ~18000 lb displacement) with a Perkins 4-108 in it. The diesel runs well, but is 43 years old, and I am thinking I will, at some point, replace it with a 14kw, 72v, liquid cooled electric at some point. I figure I should be able to mount the motor where the v-drive is currently, and the batteries where the engine is. But we'll see.

On Thursday, June 23, 2022 at 12:53:55 PM EDT, Rumble <rumble@bigpond.net.au> wrote:

Just wondering if anyone can give real life experience with replacing a 20hp or 30hp diesel with a 10kW 48V electric motor diy. I am aware of the conversion and inefficiency allowances etc, but in actuality, is it more like a 20hp or 30hp, assuming same prop and configured rpms etc?

Re: [electricboats] 48V 10kW vs 20/30hp ICE

Interesting! I have previously noticed the combination of 2 EM's in some setups, but normally arranged with one at the front and one behind, not like that! Haven't seen this before. Thanks!!

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

Lynch Swordfish comes in a 16kW size at 48V. Not a fan of the belt drive arrangement though:

https://lynchmotors.co.uk/inboard.html

Also unclear if they're available where you are (down under?).

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

Hi, thanks for your information Jeffrey. Even though I have worked the stats on boat sizes v engine sizes etc, I am very happy with my existing 2 x 30hp Volvos in our 35ft 16500lb displacement catamaran. I wouldn't go less. Anyhow, I am starting by replacing one engine and upgrading the alternator on the other, and go from there.
There's plenty of room for 1 or 2 x 300A 48V lithium bank but still tying loose ends with BMS and max amperage types and arrangements. I am sure 12-15kW would probably be more aligned with my existing engine setup, but I can't find much in the 48V range.
GM no longer have a 15kW but recommend the 10kW. Controllers....won't start on these.
Hence my question, as I won't go 72V unless I really need the 12-15kW size. Cheers.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

I replaced my Atomic-4 (rated at 30 hp, but probably, really closer to 20) with a 10kw kit from Thunderstruck. It worked well in my Pearson 30 (30 feet, about 8300 lbs. displacement) sailboat. I was limited by the small battery bank, but it got me in and out of the cove where my mooring is located. I used the same prop that I was using for the A-4.

I since upgraded boats to a Pearson 365 (36.5 feet, ~18000 lb displacement) with a Perkins 4-108 in it. The diesel runs well, but is 43 years old, and I am thinking I will, at some point, replace it with a 14kw, 72v, liquid cooled electric at some point. I figure I should be able to mount the motor where the v-drive is currently, and the batteries where the engine is. But we'll see.

On Thursday, June 23, 2022 at 12:53:55 PM EDT, Rumble <rumble@bigpond.net.au> wrote:

Just wondering if anyone can give real life experience with replacing a 20hp or 30hp diesel with a 10kW 48V electric motor diy. I am aware of the conversion and inefficiency allowances etc, but in actuality, is it more like a 20hp or 30hp, assuming same prop and configured rpms etc?

Re: [electricboats] 48V 10kW vs 20/30hp ICE

Hi Ryan. I like your setup. Thanks for the link. I have 3 blade folding props that maybe suited to regen. When sailing, they do not fold and spin when in neutral. In fact, as per the Volvo specs, I have to put the gears in reverse to fix them from spinning. When I convert to electric, I suppose time will tell whether they will fold or allow regen. All depends on how much energy is required to turn the prop with the EM.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

Agreed, thanks for confirming my thoughts. 30hp (20.1kW) less ICE inefficiencies = 15kW. Though the ICE max RPMs = 3600, in 20 years I don't think I have ever exceeded 3200. Nowadays 2800 is max, and gets me out of most trouble. Cruising RPMs is 2000-2500. As torque is high at the lower end for EMs, then the 10kW could be adequate. As I am considering DIY, I am not keen to exceed a 48V setup. Again, thanks very much for your feedback.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

Thanks William, good to know. I had the option of 20hp or 30hp when I bought 20 years ago. Though I'm glad I went with the 30's, as there have been times through bars, current and against the wind/sea, when I've have needed it. The 108 is a big engine with same RPMs, so that is good to know. Appreciate your comments.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

I replaced a 15hp yanmar 2qm15 with a 10kw 48V thunderstruck system so a bit smaller initial diesel than what you are comparing against. I did switch to a larger 3 blade prop to get more range and regen (capability).

There are lots of nice aspects of the electric motor:

1) limited maintenance, i.e. no transmission to worry about among many other things.

2) quiet

3) has a lot of torque at low rpms and can run at an arbitrarily slow speed, super nice for maneuvering to get in and out of a slip.

I would highly recommend going with LFP batteries. Do not get lured into the 'cheapness' of lead acid or agm batteries.

Detractors of electric will tell you... what if you are in a storm and you need to motor full throttle for 48 hours. Ok, you got me, make sure you have done all your 'standard maintenance'. I hope you know what storm sails are.

I carry a small 2200 honda generator and 5 gallons of fuel so if I need to harness the energy density of fossil fuels that is an option. You can do a lot with 2kw of power, maybe not hull speed but the boat moves pretty well. This goes a long way to alleviating range axiety.

The continuous power rating works out to about 13hp for a 10kw motor. That said -

Great read:

https://blog.greenyachtsales.com/blog/the-hp-of-an-engine-vs-the-kw-of-an-electric-motor?hs_amp=true

"electric motor of X kW is comparable to a gas or diesel engine with HP 2-3 times higher"

In summary, I would say the electric motor shines at low rpm and being ready in an instant. The ice shines in running for long periods of time at high rpm. If you don't use an oversized prop with the electric, you are missing out on all that easy low rpm torque.

Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------

From: Rumble <rumble@bigpond.net.au>

Date: 6/23/22 6:53 AM (GMT-10:00)

To: electricboats@groups.io

Subject: [electricboats] 48V 10kW vs 20/30hp ICE

Re: [electricboats] 48V 10kW vs 20/30hp ICE

10kW at the prop shaft will be 13.4hp, but prop RPMs may differ between electric and diesel.

There are two areas where electric boat motor makers get to exaggerate the 'equivalent horsepower' of their motors beyond a strict units conversion: out-of-the-hole torque/acceleration, where electric wins over ICE, and generally lower prop RPMs for electric, allowing for more efficient propeller design. As an example, the Propel S1 claims 73.5% efficiency from electric-power-in to propulsive thrust from the prop. At 10kW electric power in, that's 7.35kW of propulsive thrust, which is in the neighborhood of a 20hp ICE outboard. ICE outboard propeller designs are nowhere near that efficient due to much higher prop RPM.

My 6kW electric outboard claims 9.9 'equivalent horsepower', but math puts it at more like 8hp. Then the more efficient propeller design (due to lower prop RPM) results in 3.42kW of propulsive thrust, which is in the neighborhood of a 10hp ICE outboard.

For comparisons between electric and diesel, the prop RPM issue will likely not be as much of a factor, due to lower typical diesel engine RPMs. Then reduction gears can completely negate that advantage, but of course that adds drivetrain loss.

My guess would be that to adequately replace a 20hp diesel motor (inboard), and keep the same prop and prop RPMs, you'll need more like 15kW electric motor output. Depending on where the prop RPMs are starting, you could gain some performance by targeting lower prop RPMs and using a higher diameter and pitch propeller. Again depending on what your prop RPMs are now, you might be able to get to a 30hp 'equivalent horsepower' performance level from 15kW electric motor output. But probably not much more than that.

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Re: [electricboats] 48V 10kW vs 20/30hp ICE

FYI, I installed a new prop per the advice from Electric Yachts, where I bought my QT10 system.

I seems to be the low end of what is acceptable for my 30-foot, 13,000 lb. displacement sailboat. Was certainly fine for my 17nm trip from Everett to Kingston in WA. About the same as the Perkins 108 I replaced, but with less extra power.

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On Jun 23, 2022, at 09:53, Rumble <rumble@bigpond.net.au> wrote:

Just wondering if anyone can give real life experience with replacing a 20hp or 30hp diesel with a 10kW 48V electric motor diy. I am aware of the conversion and inefficiency allowances etc, but in actuality, is it more like a 20hp or 30hp, assuming same prop and configured rpms etc?

Sunday, June 19, 2022

[electricboats] 48V 10kW vs 20/30hp ICE

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Saturday, June 18, 2022

Re: [electricboats] LifePo4 build questions

I'll be adding a fuse right at the connection. I still have not had a chance to get out and test the batteries but will post back when I do.

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Friday, June 17, 2022

Re: [electricboats] >200 Ah cell size

I don't know where that rumor started, I was always skeptical of it. My 1000ah Winston cell are 12 years old have run daily house load for that 12 years, and have racked up close to 3000 miles of sea travel as a traction pack, and the last time I checked about a year ago was still delivering 100% capacity.

On 17 Jun 2022, at 14:06, Steve Gjertson <sgjertson@gmail.com> wrote:

Hello,

I am revisiting my sailboat conversion after some time. I am in the process of sourcing cells for a 48v LifePO4 pack. I had read a while back that going over 200Ah cell size was not a good idea from a durability standpoint and structural strength to weight ratio of the cell. Is this still the case or have technological advances over the last several years negated this concern
Thanks,

Re: [electricboats] >200 Ah cell size

I've 16S2P of 272Ah Basen cells - had them a year so can't give you the long view but so far so good.

On 17 Jun 2022, at 14:06, Steve Gjertson <sgjertson@gmail.com> wrote:

Hello,

I am revisiting my sailboat conversion after some time. I am in the process of sourcing cells for a 48v LifePO4 pack. I had read a while back that going over 200Ah cell size was not a good idea from a durability standpoint and structural strength to weight ratio of the cell. Is this still the case or have technological advances over the last several years negated this concern
Thanks,

Re: [electricboats] >200 Ah cell size

My 1,000 AH Winston cells are doing just fine after 9 years.

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[electricboats] >200 Ah cell size

Hello,

I am revisiting my sailboat conversion after some time. I am in the process of sourcing cells for a 48v LifePO4 pack. I had read a while back that going over 200Ah cell size was not a good idea from a durability standpoint and structural strength to weight ratio of the cell. Is this still the case or have technological advances over the last several years negated this concern
Thanks,

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Saturday, June 4, 2022

Re: [electricboats] LifePo4 build questions

Looks good . . . but I see no fuse or circuit breaker. Keep that in mind as those terminals are 'exposed' in the sense that an inadvertent short there will cause grief. No doubt you'll have a fuse between the battery and load, but closer is better as far as fuse and terminals go. Less room for something to get at the unprotected parts. That's why my fuse is inside the box. The circuit breaker approach has the advantage of also being a master shutoff switch, something most experts will at least recommend (and which I don't have).

Definitely more fun building something like this than just bolting together three off-the-shelf batteries. And, if something were to fail in your battery, you're far more likely to be able to diagnose and correct the failure than in the off-the-shelf approach.

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Re: [electricboats] LifePo4 build questions

I was able to balance all 16 cells and only 3 came in under 58ah. After choosing the top 12 cells it was time the finalize this assembly.

The last picture showed the final battery with charg leads and the charger. The charge leads will be stowed. The cells fit perfectly in a Harbor Freight 4600 waterproof case.

I might be able to test it tomorrow on the water if I have time.

It would have been easier to just buy three 12 batteries but I had fun building this.

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Thursday, June 2, 2022

Re: [electricboats] Another LifePo4 build question

Myles - by 4s, I mean 4 LiFePO4 cells in series, so 4 x 3.2V or 12.8V nominal. Very simple.

Ironically, though I bottom balance, I've never drained the pack yet. It is on a sailboat. Actually, the BMS never shut down the pack due to under voltage or over voltage (conservative charger controllers), but I did have two shutdowns due to high temperature one hot summer day when pushing the pack hard. That was back when I had a PWM motor controller physically close to the BMS. Removing that motor controller stopped the shutdowns.

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Wednesday, June 1, 2022

Re: [electricboats] Another LifePo4 build question

Thanks Curtis---great explanation.

When you say "4s pack" --- normally I'd think this means 4 cells in series, which might be just 17v fully charged. Is that about what you have or are you talking about 4 modules in series of, say, nom. 13v lithium batteries that have internal BMS themselves also?

Bottom, Top and Continuous balance techniques certainly have their distinct benefits and tradeoffs. Ideally some sort of continuous balance would be optimal---balancing during operation throughout the operational voltage. Then, the cells could conceivably better track throughout the range. I think the main thing that this is good for is to address "self discharge or leakage" that causes one or a few cells to droop while the pack is just sitting there at intermediate voltages. I see this on my boat---over months of time about 6 pairs of cells drift. I don't know for sure what the cause is but self-leakage is possible. With the BMS running always or periodically while at the dock, the rest of the pack can be made to track the drifters.

Bottom balancing certainly is good if you're hyper-miling your pack usage and trying to get that last bit of energy out while not reversing a cell.

In my case, as a rule I never take my pack below 33v (and usually 36v) with 30v as the spec'd lowest voltage for a 2.5v/cell minimum voltage. At 33v, the average cell voltage would be 2.75v/cell. Even if I had 4 cells in the string that at that point drooped to 2.5v/cell, the remaining cells would on average be at 2.875v/cell. This represents 375mv/cell of imbalance for those 4 cells.

I have had a single cell pair get almost about this far out of balance and since have been careful to stop discharge at around 36v.

Better still, my cells are now all balanced to within about 50mv. J

Top balancing is very useful if you're more concerned about cells exceeding the max voltage rating during charging. This is the default balancing mode for the RLECs I have from Enerdel. However, they don't start bypassing until something like 4.1vpc and I have only been charging my pack to 47.9v or 3.99vpc, so if I powered the RLECs during charging, for the most part they would likely not do anything unless I boosted my charge voltage another volt or so. I might go that direction…after all, an extra volt would be nice J.

So for the most part, I am neither Top-, nor Bottom-balancing mine. I use a CI/CV power supply for charging, never discharge below an average of 2.75vpc and take a glimpse at the cells every few months to confirm no cell pairs more than 100mv from the rest.

Thanks.

From: electricboats@groups.io [mailto:electricboats@groups.io] On Behalf Of cpcanoesailor via groups.io
Sent: Wednesday, June 1, 2022 7:39 AM
To: electricboats@groups.io
Subject: Re: [electricboats] Another LifePo4 build question

Myles - I bottom balance, but I have a little 4s pack. Some DIY EVers were very keen on it, and it made sense to me for a simple traction pack.

My BMS is not balancing, and it uses very little power. I have left it connected since assembling the battery 3 years ago, even when storing for 4 months with no charging. In fact, I have only used an AC charger once, after bottom balancing the cells. Everything else has been solar charging on the boat.

Certainly, in a larger, more complex battery, there will be more variation between cells, and balancing and BMS activity will be much more complex.

Interesting discussion.
Curtis Patzer

Re: [electricboats] Another LifePo4 build question

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