Low Budget Lifepo4 Experiences anyone?

[DeValency]

Originally Posted by Dave9111

My insurance company (Geico) has said nothing about Lithium batteries yet.

I'm a consulting Electrical Engineer. I've been doing it for a long time.
No Electrical Engineer worth his salt will write a letter saying your Lifepo4 electrical installation is ok just by looking at it. When an engineer does that they are assuming some liability. That's not a minor thing. If a lawsuit comes about, they can go after the engineer that blessed the system. I've seen it happen.

They (the engineer) will ask questions like... are those cells CE, UL, or CSA approved? What about the BMS system. Is that approved?

The engineer will want to try and rely on proven equipment before blessing anything. So what happens if you have a homebuilt battery bank using unknown quality cells and BMS systems??

Once ABYC figures Lithium batteries out, they could be asking questions like.. if you have a Lithium battery on your boat, is it approved by UL or CE, or CSA? That could in turn be repeated by your insurance company towards you.

So what happens if you spent $4000 into a Lithium battery system and nothing is approved, what can you do?

My guess would be to find a different insurance company that doesn't care, or replace whatever is not approved!

That could get expensive.

There are some UL approved Lithium cells out there:
https://www.electriccarpartscompany....fied-batteries

But they aren't $50 each!

There are a number of standards for Lithium batteries.

Some really bad Lithium Ion battery fires started all of this.
Remember the burning Samsung phones? The fires on the airliners?
There is a reason why you can't ship larger Lithium batteries via planes.

https://www.csagroup.org/testing-cer...nergy-storage/

https://www.ul.com/industries/energy...energy-storage

https://www.ul.com/services/battery-...-manufacturers

Well, as an EE, I can't agree with almost any of your claims here. I'm not sure you know the chemistry of LFP cells, the function of a BMS and how it is connected, nor the horrible poor reputation of the "Duracell" (brand that has nothing to do with the real Duracell alkaline batteries) AGM, that are sold, for a reason, at 50% of the LifeLine Marine AGM batteries.

But maybe my engineering school wasn't so great...

[mitiempo]

Originally Posted by DeValency

3. Shore Power Charger.....
However! - Most chargers would not be suitable for a full optimized charging, even if they have a LiFePo charging mode. The charger need to be CCCV - Constant current and constant voltage of 16.8V in order to max the batteries capacity at 4.2V per unit. Standard 12V chargers usually get to 14.5V at the bulk mode (3.6V per unit), which will provide you more or less 70-80% capacity - still better than any AGM battery.

I'm not sure where you are getting the 16.8 volts from. Calb for instance are rated at 3.2 volts with a maximum charge voltage of 3.65 per cell - 14.6 for a 12 volt bank. There should not be an absorption stage or a float stage.

The BMS I will be using can be used with many charge sources as it cuts charging at 3.55 volts per cell - 14.2 for the bank. Much healthier for the batteries.

[DeValency]

Originally Posted by mitiempo

I'm not sure where you are getting the 16.8 volts from. Calb for instance are rated at 3.2 volts with a maximum charge voltage of 3.65 per cell - 14.6 for a 12 volt bank. There should not be an absorption stage or a float stage.

The BMS I will be using can be used with many charge sources as it cuts charging at 3.55 volts per cell - 14.2 for the bank. Much healthier for the batteries.

All the LFP batteries are rated at 3.2V, but if you look at their typical charge graph, you’ll see this voltage stands around 70-80% charging. My batteries come from Sinoli - I believe they are among the biggest LFP manufacturers in China and this is what they recommend. Originally, I have used my Victron charger but couldn’t get over 3.3-3.4V per cell module. When inquired with their (excellent) tech support, this is what they recommended.

What BMS are you going to use?

[newhaul]

Originally Posted by DeValency

Few suggestions:
- Most chargers would not be suitable for a full optimized charging, even if they have a LiFePo charging mode. The charger need to be CCCV - Constant current and constant voltage of 16.8V in order to max the batteries capacity at 4.2V per unit. Standard 12V chargers usually get to 14.5V at the bulk mode (3.6V per unit), which will provide you more or less 70-80% capacity - still better than any AGM battery.

Really well then I feel sorry for your bank account if you actually see charging to 16.8 as a good normal thing.
My cells are fully charged at 3.65vpc or 14.6 vdc regularly charging to 4.2 vpc will cause a significant loss of battery life . And possibly a catastrophic failure.
Just not worth the final 1% to me .

[mitiempo]

Originally Posted by DeValency

All the LFP batteries are rated at 3.2V, but if you look at their typical charge graph, you’ll see this voltage stands around 70-80% charging. My batteries come from Sinoli - I believe they are among the biggest LFP manufacturers in China and this is what they recommend. Originally, I have used my Victron charger but couldn’t get over 3.3-3.4V per cell module. When inquired with their (excellent) tech support, this is what they recommended.

What BMS are you going to use?

i guess you haven't read the entire thread. I posted it before. The Electrodacus.

https://electrodacus.com/

https://www.youtube.com/watch?v=PldmjOPjGGY&t=14s

https://www.youtube.com/watch?v=eCspxDLZR9U

[mitiempo]

Originally Posted by newhaul

Really well then I feel sorry for your bank account if you actually see charging to 16.8 as a good normal thing.
My cells are fully charged at 3.65vpc or 14.6 vdc regularly charging to 4.2 vpc will cause a significant loss of battery life . And possibly a catastrophic failure.
Just not worth the final 1% to me .

I agree 100% with newhaul. My BMS cuts off charging at 3.55 per cell - 14.2 volts.

At your charging voltages the Chinese will sell more batteries though.

[DeValency]

Thanks for the comments. You are all right, of course!

And my apologies on the voltage info. Not sure where my head was last night . The LFP max recommended voltage is indeed 3.65V per cell/module and I do agree the cutoff should be at around 3.55V.

4.2V is the remaining memory from my first testing of Lithium Ion batteries few years ago before I moved to LFP.

Re. Electrodacus; had long discussions with Dacian about the entire setup few months ago. Should check with him again.

[Dockhead]

Originally Posted by Franziska

Hey thanks.

No, we will not run large inverters.
We just have some loads which run longer once in a while.

Its less about a pointload for us but more about continous draw. I am aware that we need to charge that back in though.

As you seem to be into the subject to some degree, we have a Waeco 1235 charger (can handle 220V & 110V input & charges up to 35A@12V, https://www.dometic.com/en-gb/uk/pro...a-1235-_-52943) right now, would we need somthing bigger for shoreside charging? Or, add a second Waeco 1235 for the larger banks (560Ah @ 12v or even 840Ah @12v)?

At sea we have a 2.6kWh Genset, 5x solar & a windgen for now.

I'm not speaking from experience, so take this for what its worth (for the voice of real experience and deep knowledge -- make friends with Jedi and Newhaul ).


But I did a lot of research on this, and I think I can offer a few tips for you which could be useful:


1. This is absolutely worthwhile, with huge improvement in functionality, and if you plan to keep your boat for a long time, will actually be cheaper on the long run than lead-acid. There is just no question that this will make lead-acid batteries obsolete pretty soon.


2. Do NOT however assume that you can just throw together some cells and a BMS and away you go. You will need to do significant changes to your charging system and other aspects of the electrical system, to make these work well.


3. One change in particular concerns the alternators. If you don't properly regulate ordinary car type alternators, you will burn them up with lithium. And once you properly regulate them, they will have suboptimal output. You will want to think about upgrading these or adding second alternators.


4. Protecting the alternators in case one of the cutoffs is activated by BMS is a topic much discussed. There are different ways to do this; buffering via a lead-acid battery is probably the most common tactic. But you can also do this with one of those Sterling alternator protectors, which is the way I would do it.


5. You will have to forget most of what you know about operation of a lead-acid bank. Particularly important is the fact that lithium batts hate to be kept at full charge (unlike lead-acid which thrive on being kept at full charge). When you design your system, you will want some way to hold your battery at partial state of charge, when you don't need the full storage capacity (e.g., at dock). I have not seen a good solution for this. The right solution would be via the BMS -- if the BMS gave you a control for what % state of charge to stop charging. Then you just set it at 50% or whatever when you are at the dock or at anchor with abundant solar or whatever -- whenever you don't need the full capacity. And change it to 100% when you're about to leave for a long passage under sail where you want the full capacity.


Good luck, and let us know how you get on!

[donradcliffe]

You don't have to spend a lot of money to keep from burning up your alternators. Just put a longer and/or thinner wire between the alternator and the LFP battery. if your LFP batteries will accept 400+ amps at 13.2v and your alternator is regulated to 14.2v, a piece of wire which will drop 1 volt at X amps will effectively derate your alternator output to a max of X. It will increase your charge times, but eliminate your alternator burnout.

For example, #2 wire has a resistance of 0.1563 ohms per 100 ft. If you want to limit your alternator output to 100 amps, you need about 6 feet of #2 wire (which has an ampacity of about 100 amps).

CAUTION: This does NOT work for external voltage regulators with sense wires that go to the battery posts, but it will work if you shift the sense wire to the alternator output post.

[kenbo]

Originally Posted by donradcliffe

You don't have to spend a lot of money to keep from burning up your alternators. Just put a longer and/or thinner wire between the alternator and the LFP battery. if your LFP batteries will accept 400+ amps at 13.2v and your alternator is regulated to 14.2v, a piece of wire which will drop 1 volt at X amps will effectively derate your alternator output to a max of X. It will increase your charge times, but eliminate your alternator burnout.

For example, #2 wire has a resistance of 0.1563 ohms per 100 ft. If you want to limit your alternator output to 100 amps, you need about 6 feet of #2 wire (which has an ampacity of about 100 amps).

CAUTION: This does NOT work for external voltage regulators with sense wires that go to the battery posts, but it will work if you shift the sense wire to the alternator output post.

I'm not an EE so take this with a grain of salt.

When I do the calculations I come up with 32' of 2AWG from the source point of 14.2V to the 100a load point to achieve a 1-volt resistive reduction to 13.2v.

And Ancor lists the ampere capacity of it's 2AWG cable as 178a in an engine space.

[newhaul]

Originally Posted by kenbo

I'm not an EE so take this with a grain of salt.

When I do the calculations I come up with 32' of 2AWG from the source point of 14.2V to the 100a load point to achieve a 1-volt resistive reduction to 13.2v.

And Ancor lists the ampere capacity of it's 2AWG cable as 178a in an engine space.

#2 wire has a 115a capacity
This chart may be helpful

[kenbo]

That chart is for SE cable (service entrance) which may explain the ampacity difference to fine stranded, 105°C rated cable.

I was quoting from Ancor's wire and cable technical data, https://www.ancorproducts.com/en/~/m...1902-49961.pdf

[kenbo]

Here's a different ampacity chart, this one for welding cable which is similar to marine cable save for the tinning. You can see that 2AWG is rated for 200a up to 50'.

[kenbo]

Originally Posted by kenbo

I'm not an EE so take this with a grain of salt.

When I do the calculations I come up with 32' of 2AWG from the source point of 14.2V to the 100a load point to achieve a 1-volt resistive reduction to 13.2v.

And Ancor lists the ampere capacity of it's 2AWG cable as 178a in an engine space.

I believe I made an error as well in my first calculation. R=V/I so 1/100 = 0.01ohms and since 2AWG has 0.1563ohms per 1000' that works out to 64' of 2AWG cable. My first reasoning was for the round trip distance but I'm not sure that's applicable in this case.

Not that I would use this method to charge an LFP battery since the charge would never stop and the constant 100a load on a small case alternator is life-shortening practice.

[newhaul]

Originally Posted by kenbo

I believe I made an error as well in my first calculation. R=V/I so 1/100 = 0.01 and since 2AWG has 0.1563ohms per 1000' that works out to 64' of 2AWG cable. My first reasoning was for the round trip distance but I'm not sure that's applicable in this case.

Not that I would use this method to charge an LFP battery since the charge would never stop and the constant 100a load on a small case alternator is life-shortening practice.

The easy answer is b2b charger.