Lithium (LiFePO4) Battery Build

[Inquisitor]

How we need to store lithium based batteries is different. It is only a CON because it is different from lead-acid usage and has to be trivially worked around.

Daily Use
If you are using these batteries on a daily basis, you charge them up and down from 0 to 100% SOC being the worst case (and get 3500 cycles). If you instead only get up and down between something in between, that is just gravy to your longevity. So, if you solar panels only get it up to 93% charge during the day... that's a good thing. This part is actually a PRO over lead-acid.

Storage
For lead-acid the thing is to put a solar panel and just let the charge controller trickle charge them during the winter. If you do this to your Lithium battery, you will destroy it in short order. Have I mentioned... never trickle charge a lithium battery!

So what do you do for Lithium if storing in the off season? Simply discharge them somewhat. The suggested is down to 13.15 volts (from 100% SOC is 14.4 volts) and disconnect them from your charger. Unlike lead-acid, Lithium have near zero self-discharge and will stay there till the Spring.

What''s the CON?

1. Having to do something different.
2. Having to disconnect them in the fall, re-connect them in the spring and recharge them before use. Lead-acid would be topped off.
3. Lithium batteries are damaged if charged below 32F (0C). The BMS I'm using protects the battery from me accidentally doing that. Some BMS's don't so, YMMV.

[Kopfjager]

@Inquisitor I wish I was as technologically inclined as you. It would definitely have saved us a bit of cash. The wife and I finally bit the bullet and ordered a Relion 300 AH battery on Thursday. I've been waiting on them to run their 15% off sale for two years.

On our we run the stereo hard, even though it is an efficient marine system, the fridge, and various other gadgets. I sincerely hate lead acid with a passion. I truly believe the lithium will be cheaper in the long run considering energy costs and time savings to charge the battery. I'll post some updates here once I get it in the boat and begin to use it.

[Inquisitor]

@Inquisitor I wish I was as technologically inclined as you. It would definitely have saved us a bit of cash. The wife and I finally bit the bullet and ordered a Relion 300 AH battery on Thursday. I've been waiting on them to run their 15% off sale for two years.

On our we run the stereo hard, even though it is an efficient marine system, the fridge, and various other gadgets. I sincerely hate lead acid with a passion. I truly believe the lithium will be cheaper in the long run considering energy costs and time savings to charge the battery. I'll post some updates here once I get it in the boat and begin to use it.

Yes, please do update us here if you wish. The forum has several large threads on boat batteries viewtopic.php?f=7&t=28031, but they are all heavily weighted toward lead-acid. I'm hoping this thread to be basically the equivalent for lithium. I don't intend this thread to be just about my build, but a sort of clearing house for anything lithium battery. Right now... it doesn't seem there is much interest, but it'll be here when someone does.

Yours Relion is a great add. I looked on their site and did a search on the DIY site. Some comment said it had built-in heating for the sub 32F charging. That would be a good feature if used during cold weather. For all that live way up their in the artic north, it'll be very important. For me... I don't think me and boat will ever be in the same place when 32F happens.

[Idiotfool]

How we need to store lithium based batteries is different. It is only a CON because it is different from lead-acid usage and has to be trivially worked around.

Daily Use
If you are using these batteries on a daily basis, you charge them up and down from 0 to 100% SOC being the worst case (and get 3500 cycles). If you instead only get up and down between something in between, that is just gravy to your longevity. So, if you solar panels only get it up to 93% charge during the day... that's a good thing. This part is actually a PRO over lead-acid.

Storage
For lead-acid the thing is to put a solar panel and just let the charge controller trickle charge them during the winter. If you do this to your Lithium battery, you will destroy it in short order. Have I mentioned... never trickle charge a lithium battery!

So what do you do for Lithium if storing in the off season? Simply discharge them somewhat. The suggested is down to 13.15 volts (from 100% SOC is 14.4 volts) and disconnect them from your charger. Unlike lead-acid, Lithium have near zero self-discharge and will stay there till the Spring.

What''s the CON?

1. Having to do something different.
2. Having to disconnect them in the fall, re-connect them in the spring and recharge them before use. Lead-acid would be topped off.
3. Lithium batteries are damaged if charged below 32F (0C). The BMS I'm using protects the battery from me accidentally doing that. Some BMS's don't so, YMMV.

If you can’t trickle charge with solar because you can’t trickle charge, how would you ever charge with solar? Can you charge via outboard alternator? Backup generator?

I’ve seen a number of Youtubers with electric conversion boats running solar, so I’m puzzled why you couldn’t keep your batteries topped up with solar and a proper BMS.

[Inquisitor]

If though can’t trickle charge with solar because you can’t trickle charge, how would you ever charge with solar? Can you charge via outboard alternator? Backup generator?

I’ve seen a number of Youtubers with electric conversion boats running solar, so I’m puzzled why you couldn’t keep your batteries topped up with solar and a proper BMS.

That's a really good question and I think I failed to explain it fully. I need to another CON and be more thorough.

First, let me define Trickle Charging as continuing to charge once the battery is at 100% SOC versus just charging at a low current rate. Yes... a single, small solar panel only delivers at a rate that even a small trickle charger can out do.

A lead-acid battery in storage... say its disconnected from any loads, brought into the garage and hooked up to a small trickle charger. The lead-acid battery is perfectly ok to be ignored the whole winter. In fact it almost has to have that charger on it. Lead-acid batteries can self discharge even if there is no load and if they get down to 0% SOC, it is severely damaged.

Lithium batteries in general and specifically LiFePO4 batteries prefer not to be at 100% SOC for long periods of time. It will deteriorate them. So... for our example of disconnecting loads and hooking up a trickle charger while in the garage, we'd be keeping it at 100% SOC all the time. The better thing to do is to drain it some and just let it set without a charger of any sort. For long term storage (months) the suggested number is to drain it down to about 13.15 volts. This is around 40% SOC. Although being new to this and worried about my investment, I might check it every once in a while. LiFePO4 batteries have almost zero self-discharge, so they are unlikely to drain further over the months.

NOW, for a more realistic case, I'm putting in one of the AirHead Composting Toilets. It uses a small fan to exhaust the fumes. Also, I'll likely have some electronics running. Say all told, I'm running less than five watts. Obviously, even this can drain a battery over several months. I'm currently in a thread with those experts on the other forum that will handle this beautifully. Basically the BMS can be configured so that it cycles from say... 40% to 70% SOC. It also reduces the number of charge cycles, so the battery longevity actually goes up during the winter. Just because of this reduced cycling strategy an estimate 50% increase in battery life... say from 10 years to 15 years might be achieved.

Let me know if this answers your question fully. I've been known to ramble the wrong direction.

[Tomfoolery]

For long term storage (months) the suggested number is to drain it down to about 13.15 volts. This is around 40% SOC. Although being new to this and worried about my investment, I might check it every once in a while. LiFePO4 batteries have almost zero self-discharge, so they are unlikely to drain further over the months.

The manufacturer of the 600Ah LiFePO4 house battery in my camper van (giant battery, no generator) recommends 50% SOC for long-term storage, which I believe they state as 13.2V, and temperature of 50F if I recall correctly. It definitely does not self-discharge to any discernible degree over the winter. My BMS shows voltage, SOC, temperature, and of course, current in/out.

No charging below 32F, and total shutdown at 0F (the BMS will shut down both functions), but I keep it warm with a heating blanket made for batteries and a wifi enabled thermostat with probe. The blanket is on a dimmer so I can regulate the output for less cycling. It’s only drawing about 50W when it’s on, and according to my Kill A Watt, costs me about $10 a season to run at a shade under $0.10/kWh.

I want that battery to outlive me without reduced capacity, so I treat it well.

[Inquisitor]

For long term storage (months) the suggested number is to drain it down to about 13.15 volts. This is around 40% SOC. Although being new to this and worried about my investment, I might check it every once in a while. LiFePO4 batteries have almost zero self-discharge, so they are unlikely to drain further over the months.

The manufacturer of the 600Ah LiFePO4 house battery in my camper van (giant battery, no generator) recommends 50% SOC for long-term storage, which I believe they state as 13.2V, and temperature of 50F if I recall correctly. It definitely does not self-discharge to any discernible degree over the winter. My BMS shows voltage, SOC, temperature, and of course, current in/out.

No charging below 32F, and total shutdown at 0F (the BMS will shut down both functions), but I keep it warm with a heating blanket made for batteries and a wifi enabled thermostat with probe. The blanket is on a dimmer so I can regulate the output for less cycling. It’s only drawing about 50W when it’s on, and according to my Kill A Watt, costs me about $10 a season to run at a shade under $0.10/kWh.

I want that battery to outlive me without reduced capacity, so I treat it well.

Storage - Great information. Actually, that is the first actual practical usage case I've read. Obviously go with what the manufacturer says. I know my cell manufacturer recommends the 13.15V and the cells came near that state. The other forum has been debating this issue for ages and tend toward the lower end also. But... everyone agrees, it about keeping out of the end-zones... 0-5% and 95-100%. I'm getting the gist, its something like our white versus blue hull arguments.

Freezing - I've read somewhere (strangely not on the manufacturer's website) that Kopfjager's Relion 300 batteries have the heating pads built in. Some of the high-end pre-made cells do this and it totally handles those issues without the user even needing to know its going on... they're trying to make it a drop-in replacement. You being in New York (inside the artic circle... right? ) you obviously have to consider those aspects.

My BMS will do both of those cut-offs. Over the coming years, I'll see if it becomes an issue where I needed to use or charge below those cutouts. I'm thinking even here in the mountains, we don't see week long sub-freezing temperatures and never sub-zero.

[Tomfoolery]

Here's a screen shot of the battery storage page, FYI. It may have something useful in it.

[Kopfjager]

For long term storage (months) the suggested number is to drain it down to about 13.15 volts. This is around 40% SOC. Although being new to this and worried about my investment, I might check it every once in a while. LiFePO4 batteries have almost zero self-discharge, so they are unlikely to drain further over the months.

The manufacturer of the 600Ah LiFePO4 house battery in my camper van (giant battery, no generator) recommends 50% SOC for long-term storage, which I believe they state as 13.2V, and temperature of 50F if I recall correctly. It definitely does not self-discharge to any discernible degree over the winter. My BMS shows voltage, SOC, temperature, and of course, current in/out.

No charging below 32F, and total shutdown at 0F (the BMS will shut down both functions), but I keep it warm with a heating blanket made for batteries and a wifi enabled thermostat with probe. The blanket is on a dimmer so I can regulate the output for less cycling. It’s only drawing about 50W when it’s on, and according to my Kill A Watt, costs me about $10 a season to run at a shade under $0.10/kWh.

I want that battery to outlive me without reduced capacity, so I treat it well.

Storage - Great information. Actually, that is the first actual practical usage case I've read. Obviously go with what the manufacturer says. I know my cell manufacturer recommends the 13.15V and the cells came near that state. The other forum has been debating this issue for ages and tend toward the lower end also. But... everyone agrees, it about keeping out of the end-zones... 0-5% and 95-100%. I'm getting the gist, its something like our white versus blue hull arguments.

Freezing - I've read somewhere (strangely not on the manufacturer's website) that Kopfjager's Relion 300 batteries have the heating pads built in. Some of the high-end pre-made cells do this and it totally handles those issues without the user even needing to know its going on... they're trying to make it a drop-in replacement. You being in New York (inside the artic circle... right? ) you obviously have to consider those aspects.

My BMS will do both of those cut-offs. Over the coming years, I'll see if it becomes an issue where I needed to use or charge below those cutouts. I'm thinking even here in the mountains, we don't see week long sub-freezing temperatures and never sub-zero.

My battery isn't the one with the built in heater. You are correct though that Relion does make a model that heats the cells prior to charging below freezing, which is great. It's the LT or low temperature model. I would imagine in another year or two, this technology will come standard on all LiFeP04 batteries. I live in Alabama so it would be a rare situation for me to even need to charge the battery below 32 degrees. Honestly, I may just discharge to around 50% and bring it in the house over the coldest winter months. Still trying to figure that out.

[Inquisitor]

Here's a screen shot of the battery storage page, FYI. It may have something useful in it.

That's interesting... I've never heard anything about long term storage and 59F on the other forum. I wonder what's the driving force for such a high minimum temperature. The charge to 100% every six months is also a new item. Might have to poke the other forum on that. Was that a scanned image off something you have or do you have a link?

[Tomfoolery]

Here's a screen shot of the battery storage page, FYI. It may have something useful in it.

That's interesting... I've never heard anything about long term storage and 59F on the other forum. I wonder what's the driving force for such a high minimum temperature. The charge to 100% every six months is also a new item. Might have to poke the other forum on that. Was that a scanned image off something you have or do you have a link?

It’s a pdf I saved, but I don’t remember where I got it. Might have been from Coachmen, since that’s who made the RV. I’ll look for it tomorrow on a real computer and post the link.

[Tomfoolery]

And here's the response I got from Xantrex when I asked the question. I thought the published instructions were a little unclear or contradictory, so I emailed. This is their response:

Hi Thomas,
We hope you are enjoying your Galleria and our UL Listed battery! The duty cycle of the temperature cycles is the key. How often or how long are you below 14F? Our recommendation is to:
-Discharge the battery to around 50%....close enough is good enough.
-Turn off the battery
-Do purchase a heater blanket and plug it into an AC outlet. Just enough to keep the battery above 32F is fine.

I can email you what I have on my computer if you want. I couldn't find the documents online. Just PM me if you want them.

[Inquisitor]

And here's the response I got from Xantrex when I asked the question. I thought the published instructions were a little unclear or contradictory, so I emailed. This is their response:

Hi Thomas,
We hope you are enjoying your Galleria and our UL Listed battery! The duty cycle of the temperature cycles is the key. How often or how long are you below 14F? Our recommendation is to:
-Discharge the battery to around 50%....close enough is good enough.
-Turn off the battery
-Do purchase a heater blanket and plug it into an AC outlet. Just enough to keep the battery above 32F is fine.

I can email you what I have on my computer if you want. I couldn't find the documents online. Just PM me if you want them.

Sounds like they're being real conservative and/or reading off a script. But a problem with Lithium is the unknown. It just hasn't been used that long in large quantities like lead-acid. I'm sure even if that company has even one real expert, they're not replying to end customers. I know in my last profession, the last thing the company wanted was us engineers talking to end-real-people. With the Tesla/electric car revolution and Norway being a huge customer, I imagine, we'll be getting lots of good data on cold weather behavior before long.

I'll take your image above and ask on the other forum. I'd really like to know what all this is about.

[Inquisitor]

And here's the response I got from Xantrex when I asked the question. I thought the published instructions were a little unclear or contradictory, so I emailed. This is their response:

Hi Thomas,
We hope you are enjoying your Galleria and our UL Listed battery! The duty cycle of the temperature cycles is the key. How often or how long are you below 14F? Our recommendation is to:
-Discharge the battery to around 50%....close enough is good enough.
-Turn off the battery
-Do purchase a heater blanket and plug it into an AC outlet. Just enough to keep the battery above 32F is fine.

I can email you what I have on my computer if you want. I couldn't find the documents online. Just PM me if you want them.

I got plenty of responses from the other forum, some were of the same thought that I had... that this is a warranty voiding clause. Either to not honor OR maybe legitimately... they just don't know. The technical stated that the electrolytes do freeze at -22F/-30C, but noted that lead-acid ones do also. A few noted, that although battery capacity while at cold temperatures was affected (similar to lead-acid) there were no life cycle capacity degradation once returned to warmer temperatures. Anyone interested in details - https://diysolarforum.com/threads/keepi ... ost-217598

[Inquisitor]

28F this morning... back to indoor projects.

While on other projects I checked self-discharge rate. That's my story and I'm sticking to it.
Over sixty days initial voltage was 13.070 and dropped to 13.063.

I also did the efficiency test comparing the low wattage usage (70 watts) on two Inverters (2200 watt and 300 watt) .
viewtopic.php?f=8&t=28020&start=30#p349411

Now its time to do a final assembly so I can put it into the boat.

Taping the battery using fiber shipping tape. On the DIY forum, this is the most common recommendation for assembly. This is just to keep them together and to a lesser extent, constrains the batteries from expansion during charge/discharge cycles.


Here the BMS wiring is attached and routed to the end of the battery. Some people put the BMS on the sides and some on the top. I've picked this orientation so that it will fit down inside the battery compartment. Points of interest: The main cable coming from the negative post of the series connected cells. Five smaller wires are for cell monitoring and keeping the cells balanced. Also note the two silver end plates. These are simply 3/4" plywood. These are to compress the cells as was discussed in this post: viewtopic.php?f=8&t=28149#p348218. It seemed to be a worth while benefit to get 40% longer life from my cells!


All the exposed wires just seem to invite mishaps... broken wires if I'm lucky, dropping a wrench and shorting several thousand amps and molten wrench flying around if I'm not. Here, I CAD'd up a set of caps. No attachment is necessary. The the pieces slide under the bus bars and the end-holes allow the threaded rod used to compress the cells. This keeps the rods isolated from the posts and makes everything tidy.