LITHIUM BATTERIES FOR DUMMIES!

[hzcruiser]

Originally Posted by Rimica

Just a report on my experience with Lithium.

I bought a brand new catamaran last year and I had requested that the electrical system be 12 volt and Lithium. The builder put an all Mastervolt system in the boat (700 Amp batteries, switches, relays, fuses, charger and inverters). All of it is connected to an onboard computer for monitoring. This is the source of the numbers I am giving below.

Hello Rimica,

thanks for sharing your numbers! May I question them a bit? So you have 700 Ah LFP capacity (not 700 Amp). What computer is monitoring it and how? A single shunt in the negative battery line would be my guess?

I have been sailing for 15 months now full time. The system is superb. I have 700 amp of Mastervolt lithium batteries. Over 15 months they have accumulated 54 cycles out of an expected usefull life of 4000 or so. [...]

Sorry, that doesn't sound right. 54 cycles over 15 * 30 = 450 days living aboard full time? That's why I asked which "computer" is coming up with such numbers.

It might be counting the Ah in or out of the bank and divides it by the capacity? In which case you would get 54 * 700 Ah = 37800 Ah drawn from the bank. That divided by the 100 Ah you seem to be consuming per day now adds up, as that gives you 378 days.

Hence, it's more likely you went through >300 "cycles" since even partly discharging a batt counts as a cycle. How much you need to discharge it before you can count it as "a cycle" is open to debate though...

I am at the dock 2 days a week on average where any accumulated deficit gets topped off. I do not have a generator on board. I use solar panels (550 watt) and a Watt and Sea water generator. When the boat goes over 8 knots (easy on a Cat) it is self sufficient over a 24 hour period. This includes watermaking.

That's excellent! Self sufficient long-distance sailing!

Since most cruisers agree that they stay >90% of the time on the hook, a tow generator often makes little sense. You seem to be underway a lot more. Could be that the Outremer just wants "to run" ?

The downside of large capacity lithium is the charging if you do not have a DC generator. After several days at anchor I can be at 50% of capacity. I therefore have 350 amp to generate to go back to 100% charged state.

Therefore it seems you're using about 100-150 Ah a day. That's not a huge amount.

In fact, this sounds too low if you even think about running an air con for half an hour a day. Fridge plus freezer and maybe one laptop alone could add up to that, without running the lights, radio, pumps, music etc.

The boat use 10amp an hour when anchored

The proper way to express this is that it "uses 10 A" on average, which is the same as "10 Ah per hour", or energy used in a given time frame. It's not 10 A an hour or 10 A per hour. Just for clarification.

Background: I am an energy pig.

If anything, you're a space pig, not an energy pig, if you're really only using 100-150Ah per day.

You need to leave and go for a 3 hour boat ride and come back. Not a solution in my view. In the Med, 5 boats will have taken your spot before you come back.

If 5 boats can fit in the space you left, you're a space pig Just kidding...

[kmacdonald]

The Nordkyn Design website has great info on lithium and I've posted links to it several times in the lithium threads. He really likes to cover all bases and some might say over the top.
If you are serious about lithium I'd suggest not using a BMS. If you feel it is absolutely necessary you shouldn't be considering lithium at all. A foolproof BMS is just cost prohibitive. Off the shelf BMS's are far from foolproof. Several companies quit offering them.
With that said, I have used a small lithium in my Capri with solar only charging that has worked flawlessly for 4 years. I have very light loads, less than 4 Ah a day, so your situation is different. If I make a charging or discharging mistake I'm only out a $150 20 Ah lithium battery. A 400 Ah @ 24V lithium battery is a LOT more expensive. A foolproof BMS would be even more and the the upgrades to all the charging sources would also be costly. There really isn't anyone qualified to do the work anyway so if you don't have the skill set to do it yourself it's not going to happen. I don't think I'd go over a 100 Ah @ 12V lithium system that could be charged with solar only and manually controlled. Really simple and not very expensive. When you start doing custom designs of a BMS you are getting way too expensive to be a viable option and that's what it would take. If you have the project management skills to oversee a group of electrical engineers, technicians, prototyping, QC, production, etc have at it. If not and you are dead set on lithium, give it a shot without the BMS and charging with only solar.
Lithium and solar are a great combination because of lithiums charge efficiency of about 99%.

[john61ct]

Getting a pro like Maine Sail or OceanPlanet to install a packaged system into your boat would be expensive, but the BMS' contribution to the overall cost is minor.

But some people drop more than that on a small dinner party and consider it money well spent.

For those who want it without acquiring all the knowledge needed for DIY, at least bank-level automatic BMS **functionality** protections are essential.

Not saying they need the cell-level stuff.

And not saying someone who doesn't want to learn at least the basics should buy even a turnkey setup.

[Rimica]

Originally Posted by Pelagic

Thanks Rimica, wonderful user's analysis.
To confirm, your solar is only 550 Watts?

Sorry, typo, 750watts

[OceanPlanet]

Originally Posted by Rimica

Just a report on my experience with Lithium.


I bought a brand new catamaran last year and I had requested that the electrical system be 12 volt and Lithium. The builder put an all Mastervolt system in the boat (700 Amp batteries, switches, relays, fuses, charger and inverters). All of it is connected to an onboard computer for monitoring. This is the source of the numbers I am giving below.



I have been sailing for 15 months now full time. The system is superb. I have 700 amp of Mastervolt lithium batteries. Over 15 months they have accumulated 54 cycles out of an expected usefull life of 4000 or so. They should last another 90 years at that rate. I run everything off the batteries including my Air Cond but not the stove.



I am at the dock 2 days a week on average where any accumulated deficit gets topped off. I do not have a generator on board. I use solar panels (550 watt) and a Watt and Sea water generator. When the boat goes over 8 knots (easy on a Cat) it is self sufficient over a 24 hour period. This includes watermaking.


The downside of large capacity lithium is the charging if you do not have a DC generator. After several days at anchor I can be at 50% of capacity. I therefore have 350 amp to generate to go back to 100% charged state. The boat use 10amp an hour when anchored and 15 to 17 when sailing on autopilot. While sailing at 8 knots and with the water generator I produce 30 to 35amp, 15 go to the boat and 15 to 20 go to the batteries. I need to sail 15 to 17 hours in good conditions to fill the batteries back to 100%. Here in the Med the sails from point to point are shorter. I seldom succeed in getting back to 100%. Crossing the Atlantic will be no problem, I will run out of food before running out of electricity.



My view after 15 month of experience would be that:
1) Lithium was worth the expense given the weight saving and the capacity

2) Charging is not a problem if the sailing is over long distances.
3) No need to run engines to charge while at anchor for several days particularly if its sunny
4) If no long distance sailing is expected or if no water generator having a meaningfull output at the cruising speed of your boat is installed then one has to think about a DC generator for recharging unless you go back at the dock every few days.


I am thinking about adding a DC generator. Fisher-Panda has a 90kg 3,200 continuous watts. This would shove 200 to 230amp an hour in the batteries. That means that after 4 days at anchor, I run the machine for 1.5 to 2 hrs and I am back to 100%. Then I could have an electric stove and Nirvanna is reached.


Caveat:
I do not run my AC 24/7. When sailing, it is not on. When at anchor I will run only the one in the Master bedroom to cool it off before going to bed (30mins) on very hot days. I do not heat my hotwater tank at anchor. I do not use my wahsing machine unless at the dock.



Background:

I am an energy pig. I have an always on computer on board plus 2 other portable that needs recharging once a day in addition to "always on" WIFI and 4G receiver. I have a fridge and a freezer plus a Nespresso coffee maker.


Notes:
Charging the batteries with the engines is not realistic. My 2 engines at 2,000rpm will put out 145amp continuous in total. That is 2.5 hours at 2,000 rpm to get back the 350amp above. In an anchorage it is not doable. You need to leave and go for a 3 hour boat ride and come back. Not a solution in my view. In the Med, 5 boats will have taken your spot before you come back.


I have tried, for interest sake, to use the small Honda generator (2,000 Watt) to charge the batteries. It was connected to my charger which outputs 100amp. First the Honda is not powerfull enough to permit the charger to output 100amp. I need to set my charger to 80amp max for the generator to work. In fact I have to ramp up the charger starting at 25amp and bring it to 80 by stages otherwise the Honda chokes. At 80 amps, you need to run it for 4 to 5 hours to go back to 100% charge and it is noisy (65 to 70 dBs). Its is better than running the engines though.



Hope I contributed positivly to the discussion


Thx

What size are your engines? Sounds like you have only the stock alternators. Most of the Li systems we do upgrade the alts and turn the engines into DC generators....

[Rimica]

I have 2 Volvo D2-40. Which are 38HP each. The Mastervolt alternators are controlled by 2 Sterling Power Products "Advanced 4 Step Digital Alternator to Battery Charger".


Those are small and light engines (as far as diesel engine goes). I can get to 8.5 knots in flat water, all out.


Thx for the interest.

[Rimica]

Thx for the reply. Good guess on the boat, yes indeed it is a pleasure to sail this boat. She just want to go and go. Here is more info:


Monitoring and Cycles:
The Mastervolt Batteries are connected to the computer via what they call "Masterbus". I have two 350amp batteries in parallel. I also have the Mastervolt software to connect the Masterbus to the computer. Numbers given are from that software and the cycles are the ones calculated by the battery management system itself. I do not know the details of the calculation.



Daily usage:
The air con is not run everyday. Only on very hot nights with no wind at all. So I did it a dozen times which may be out of my averages.


What happens on usage over a 24 hour cycle is: down by 20-25% by the morning and up 10% by the end of daylight for a net average 15% depletion per day. I am rounding here. If no sun during the day its a depletion of 25%. Those are the numbers I use for my planning.


And yes here in the Med anchoring with proper scope is a bit different then in North America. Most boats go to anchor for the day and go back to the marina at night. So often their view is as long as the anchor is wet it has proper scope. In the middle of the afternoon in some cala you can walk from boat to boat to go to the beach while after 20:30 at night there is only 2 or 3 boats left.


Hope this help.

[OceanPlanet]

Originally Posted by Rimica

I have 2 Volvo D2-40. Which are 38HP each. The Mastervolt alternators are controlled by 2 Sterling Power Products "Advanced 4 Step Digital Alternator to Battery Charger".


Those are small and light engines (as far as diesel engine goes). I can get to 8.5 knots in flat water, all out.


Thx for the interest.

Perfect size engines for being your DC generators. Use switches to turn them off or to 1/2 power when full motoring power is needed. See attached pic of 360A super compact AP HPI on a Yanmar. Puts out 300A continuous. Of course you may not need so much, however with the smaller engines you'll be very fuel efficient.

[john61ct]

With a good "DC generator", regular motoring and an LFP bank, there may be no need for any solar nor an AC generator.

[Q Xopa]

Originally Posted by OceanPlanet

Perfect size engines for being your DC generators. Use switches to turn them off or to 1/2 power when full motoring power is needed. See attached pic of 360A super compact AP HPI on a Yanmar. Puts out 300A continuous. Of course you may not need so much, however with the smaller engines you'll be very fuel efficient.

This is certainly a very nice solution.

This is also going to take more than 4.3kW/6 HP to drive. Which is more in your engines happy operating range than lightly loading it.

It is also not inexpensive,

In ball park numbers-
$2,895 High output alternator • 360-amp, 12-volt output • 360HPI-GM60-12
$1,149 Serpentine pulley kit
$ 427 Balmar MC-624, (if you dont have one already)
$???? Labor to have this fitted

This is north of $4k. (Not including the last 2 line items).

This for a small case alternator, all be it a very impressive output numbered one. 300 A continuous is certainly substantial.

Can it continiously dissipate enough heat surely produced at those sort of output levels?

Is there a reason for using a 6 rib serpentine rather than 8 rib? Both are readily available at reasonable cost. 6HP+ is asking a lot for even a serpentine belt. My thinking is if your going to the effort of going Serpentine why go the small one. It will wear faster than an 8 rib having 25% less ribs sharing the load.

I dont know how much room is in your engine bay, but if you have at least an inch extra clearance from your current alternator my preference would be a large case alternator. Maybe Bruce will have a better version than me but it seems to me that large case units have more metal to dissipate heat from and more more air flowing through the inside to cool more. But that's just me.

I recently heard someone trying to convince me to ditch my large case alternator for a small case unit. The reason given that large case alternators are too hard on engine crank bearings. As a diesel mechanic I have never heard this one. I questioned how this worked, commenting if they could explain this more to me as my obvious limited understanding was that 300A, or whatever number, will require the same amount of torque to drive either small or large case. The engine doesnt know if the alternator is big or small, surely it only feels the drag it is putting on the engine.

Apart from that a typical diesel engine has big explosions pushing/ pounding the crank into the bottom side of the main crank bearings. Conversely most alternators are mounted above the crank so pull up, opposite to the weights of the pistons, conrods and the explosions. But I suspect nowhere near the same magnitude of force. We learn something new every day eh.

I would suggest, if anyone is a little DIY inclined, this can be done way cheaper. I am nearly finished a 2x 220A large case install with, programmable external regulators, Remote rectifiers and heavy duty drive belts. 2 large case Alts and Remote rectifiers to me give more redundancy and are able to share and dissipate the heat better. That's just my uniformed opinion though. Remote rectifiers also hopefully will keep more generated heat out of the Alternators. Diodes produce a lot of heat in the back of our alternators. The alternator also get a lot better airflow through them without the diode heat sink significantly impeding the airflow in from the back of the Alternator.

I wont say it's easy, but honestly it's not that difficult either. My biggest fiddle thus far is playing with alt mounts and pulley spacers to get everything clearing and aligned. I'm just finishing getting some machine work done. I will post details of what parts I've used, what I had to fiddle with and how it seems to be going when I'm done. If anyone wants details so far feel free to PM me.

Obviously Bruce knows way more about this stuff than me.

[kmacdonald]

First off I'd never mount a 300A alternator on the engine. Secondly a 300 A alternator will take more than 12 HP to run. That's about a third of the engine output----way too much. There's more but I'll stop at that.

[OceanPlanet]

Don't need to go all the way to the HPI. The Mark Grasser (MGDC) 250A J180 large case with an external rectifier is less power but arguably more bang for the buck. Or even the MGDC 160 or 180A with external rectifier are way better than what most folks have.

FWIW, I know we're talking 12v here, however it's important to note that more & more boats are going to 24v, or even 48 (actually 51v Li). You get way more actual watts for the same load, use smaller cables, etc. For instance the HPI 150A x 50v version is the same size & weight as the 360 x 12v. So even if running at only 100A x 50v, that's 5kW, whereas the 12v running at 300A x 13v is 3.9kW


But the higher voltage is more relevant on boats with high loads, running lots of stuff off inverters, etc But I couldn't resist mentioning it...

[OceanPlanet]

Originally Posted by kmacdonald

First off I'd never mount a 300A alternator on the engine. Secondly a 300 A alternator will take more than 12 HP to run. That's about a third of the engine output----way too much. There's more but I'll stop at that.

Definitely must be carefully configured. Belt should be close to engine, may need idler pulleys to direct the load, etc.

We seem to be loading at around 10hp at full current, but it's hard to tell for sure.

[a64pilot]

Likely less than 10 HP. Direct conversion of 3600W to HP is about 5 HP.
My 3.5 KW generator uses a 7 HP engine.
I’m assuming 12V and 300 amps, of course if voltage is higher, wattage is too, but I bet 10 HP guess is conservative.

[kmacdonald]

Originally Posted by a64pilot

Likely less than 10 HP. Direct conversion of 3600W to HP is about 5 HP.
My 3.5 KW generator uses a 7 HP engine.
I’m assuming 12V and 300 amps, of course if voltage is higher, wattage is too, but I bet 10 HP guess is conservative.

The general rule of thumb for an alternator is 1 HP for 25 amp output. Google will confirm.