Question about specs for DIY build

[John SK]

Hello. I'm going to buy a lithium battery kit or hire someone to build a pack for me. I don't want to get lost in the weeds over exact products, but wanted to know more about higher level construction methodology suited to my intended use.

The LiFePO4 battery would be used in a 23' long Sprinter 3500 based motorhome vehicle that's heading out from SE USA to South America for a 2-year, 40,000 mile trip. I'll probably endure 15,000+ miles of gravel corrugated roads in average to poor condition, compared to US roads. The battery is in a "step-well" battery compartment typical of Class C vehicles at the entry door. Weather conditions will range from 105F to -10F, so the batt would be heated. The battery compartment is closed (not open to the elements), well insulated, vented into the vehicle (with fans) and designed to house batteries.

QUESTION: What's important to improve durability? Should I be thinking about a particular type of bus bar, cell compression method, etc? I have no idea.

I could not find a "pair" of batteries, that would have offered redundancy, to fit. I need at least 300AH total energy storage. I'm not fond of having only one battery, but since this seems to be my only viable option, I'm thinking a "kit" or custom build battery would be best. Because I can repair it if it breaks and maybe take an extra BMS and a cell, or whatever makes sense, with me in the spare parts locker. At least this makes me feel a little more comfortable since all my eggs are in one basket with a single 300 amp hour battery. I hope this makes sense.

Thanks for any thoughts.

 

[sunshine_eggo]

DIY build on a mission critical battery needs to be done right. Hiring somebody to build you one where you might get decent support is almost laughable.

Figure out how to make multiple batteries work. 3X 100Ah?

I see two options:

1. Buy SOK batteries. They are user serviceable. Buy more than you need. Keep at least one in reserve for emergencies.
2. DIY with "grade A" cells and at least 4 spare cells in reserve. Again, 3X 100Ah batteries (12 cells + 4 reserve). Ensure you select a "smart" BMS, for each battery so you can have cell visibility.

 

[chrisski]

Hello. I'm going to buy a lithium battery kit or hire someone to build a pack for me.

IMO, do not hire anyone to build one for you. Between shipping and time, there is no way you could get a custom battery for your rig and be able to pay someone a good rate for his time.

Capacity testing and Top balancing can take in excess of a week. Cutting custom 1/4" X 3/4" copper bar at $2 per inch materials to fit on studs is costly.

Also, best practices...All over the board.

Either do this yourself or buy a lithium battery.

Building my own battery starting from scratch took weeks between research, teaching myself to cut busbars, teaching myself how to do a battery case, finding out compression was done with 1/4"-20 rod, looking for a case for this which did not exist, to figuring out how to build that case.

Done again, the next one would be quicker and I can buy 16S 280 ah cases, I would use the busbars that came with it, etc, but would still take a lot more time than I'd like to spend.

=================
My battery bank is 560 ah 24 volts with 2 X 8S cells, about 200 LBS total I fit in this slideout tray:

Amazon.com

Also, if the tray is extended, I support the 200 LBS with an RV slideout support.

 

[hardtop]

Buy store-bought batteries that already have a BMS and a heater. The DIY route is for people that like to get hands-on and tinker with things as well as save money.
I built a DIY 304 AH 12V pack and for its size, weight and cost its amazing compared to lead acid. I get 3.4 kWh out of the pack at the inverter which is all day use and then I charge it first thing in the AM with a generator. I saved about $200 over going with a name brand AIO, not a huge amount but I know a hell of a lot more about batteries and charging than I ever have lol.

 

[John SK]

DIY build on a mission critical battery needs to be done right. Hiring somebody to build you one where you might get decent support is almost laughable.

Figure out how to make multiple batteries work. 3X 100Ah?

I see two options:

1. Buy SOK batteries. They are user serviceable. Buy more than you need. Keep at least one in reserve for emergencies.
2. DIY with "grade A" cells and at least 4 spare cells in reserve. Again, 3X 100Ah batteries (12 cells + 4 reserve). Ensure you select a "smart" BMS, for each battery so you can have cell visibility.

I agree entirely. I've been incredibly frustrated at this little vehicle's size constraints, compared to a much larger RV that I have, plus the low cargo capacity. My first preference last week was two SOK 206 AH 12V blue tooth, heated batts. I dropped the idea due to the work required to install them. But I just re-measured and reconsidered that option, so I've decided to modify the batt compartment to fit the two SOK 206 batts. That would give me redundancy plus 412 amp hours, that's 112 more than a single, 300AH batt. The job is about $500 in parts (e.g., tearing out 2 buss bars & a shunt that I installed already, some new cables, etc.) and 20 hours of hacking, cutting, but the outcome is far superior. I build the compartment 4 years ago. Its astonishing to me how far lithium has progressed.

I did not know that the SOK batts are servicable. That's good news.

 

[John SK]

Buy store-bought batteries that already have a BMS and a heater. The DIY route is for people that like to get hands-on and tinker with things as well as save money.
I built a DIY 304 AH 12V pack and for its size, weight and cost its amazing compared to lead acid. I get 3.4 kWh out of the pack at the inverter which is all day use and then I charge it first thing in the AM with a generator. I saved about $200 over going with a name brand AIO, not a huge amount but I know a hell of a lot more about batteries and charging than I ever have lol.

Thanks. I'm gonna go store bought for sure; SOK. I was considering a 300AH pre-built SFK battery, perhaps with some upgrades, but I just never could get comfortable with a single battery.

 

[sunshine_eggo]

I agree entirely. I've been incredibly frustrated at this little vehicle's size constraints, compared to a much larger RV that I have, plus the low cargo capacity. My first preference last week was two SOK 206 AH 12V blue tooth, heated batts. I dropped the idea due to the work required to install them. But I just re-measured and reconsidered that option, so I've decided to modify the batt compartment to fit the two SOK 206 batts. That would give me redundancy plus 412 amp hours, that's 112 more than a single, 300AH batt. The job is about $500 in parts (e.g., tearing out 2 buss bars & a shunt that I installed already, some new cables, etc.) and 20 hours of hacking, cutting, but the outcome is far superior. I build the compartment 4 years ago. Its astonishing to me how far lithium has progressed.

I did not know that the SOK batts are servicable. That's good news.

AND... get a third battery. Put it in the closet.

 

[John SK]

IMO, do not hire anyone to build one for you. Between shipping and time, there is no way you could get a custom battery for your rig and be able to pay someone a good rate for his time.

Capacity testing and Top balancing can take in excess of a week. Cutting custom 1/4" X 3/4" copper bar at $2 per inch materials to fit on studs is costly.

Also, best practices...All over the board.

Either do this yourself or buy a lithium battery.

Building my own battery starting from scratch took weeks between research, teaching myself to cut busbars, teaching myself how to do a battery case, finding out compression was done with 1/4"-20 rod, looking for a case for this which did not exist, to figuring out how to build that case.

Done again, the next one would be quicker and I can buy 16S 280 ah cases, I would use the busbars that came with it, etc, but would still take a lot more time than I'd like to spend.

=================
My battery bank is 560 ah 24 volts with 2 X 8S cells, about 200 LBS total I fit in this slideout tray:

Amazon.com

Also, if the tray is extended, I support the 200 LBS with an RV slideout support.

Going store bought. The more I thought about a DIY, the more I realize I don't have the time and a the cost savings isn't really important in the context of my rig's build.

 

[John SK]

AND... get a third battery. Put it in the closet.

No can do. Money isn't a factor, but in this little rig, I just can't carry another battery for such a low probability event. I do have an EcoFlow DELTA 1300 watt hour power station. Warranties are of little value cuz I can't use them out of the US, most likely. But if the batt is servicable, what's the least amount of parts I can carry? I can carry a spare BMS, if SOK will sell me one that will work with their batt, and 1 cell. That's what I'm thinking. When a cell failure occurrs, isn't it just one cell? Or, do they all go? Maybe carrying one cell makes no sense. Don't know. Carrying 4 is a little prohibitive in terms of bulk and weight.

 

[featherlite]

It is not clear to me, but it sounds like you may have decided to buy at least one SOK 206 AH 12v battery.

Is your EcoFlow a 105Ah battery? If so, would it make sense to forgo and replace the EcoFlow with another SOK 206, which is almost twice the capacity? My thinking is that the EcoFlow is about the same physical size as one SOK and the extra SOK could be stored wherever you were planning on storing the EcoFlow.

I am just brainstorming with you.

PS: Sounds like you are going on quite the adventure!

 

[John SK]

It is not clear to me, but it sounds like you may have decided to buy at least one SOK 206 AH 12v battery.

Is your EcoFlow a 105Ah battery? If so, would it make sense to forgo and replace the EcoFlow with another SOK 206, which is almost twice the capacity? My thinking is that the EcoFlow is about the same physical size as one SOK and the extra SOK could be stored wherever you were planning on storing the EcoFlow.

I am just brainstorming with you.

PS: Sounds like you are going on quite the adventure!

I'd do 2 SOK 206's for a 412AH bank. The EcoFlow is the DELTA 1300 power station that I think is 1280 watt hours. It offers a lot of funtion including an 1800 watt PSW inverter.

Do the SOK batteries have a high failure rate?

I'll have to think about substituting another SOK 206 for the DELTA. I already own the DELTA, including a 160 watt foldable PV panel. I'd have to think about how I could use a spare SOK battery. With a 412AH bank, and knowing my loads, the spare SOK wouldn't be needed to supplement the bank, so I guess it would just be for a failure.

 

[featherlite]

Do the SOK batteries have a high failure rate?

Not to my knowledge.
As for me personally, if I had to buy an off the shelf battery, the SOK is the only off the shelf battery I would buy.
I would buy from
https://www.currentconnected.com

 

[John SK]

Not to my knowledge.
As for me personally, if I had to buy an off the shelf battery, the SOK is the only off the shelf battery I would buy.
I would buy from
https://www.currentconnected.com

this vender doesn't seem to offer the model I want, which has both bluetooth and the heater.

 

[Partimewages]

Email them and see what they can do.

 

[sunshine_eggo]

@HighTechLab is a bigwig regarding SOK batteries in the U.S.

EDIT: Oh.. and he doesn't suck...

 

[John SK]

@HighTechLab is a bigwig regarding SOK batteries in the U.S.

Thanks. I checked that site but they didn't offer the batt I wanted. I just bought a couple 206AH SOKs off SOK's site. Hey, do you know a vendor where I can order some pre-made cables, like 2/0 & 4/0 stuff. Good cables, like fine stranded tinned copper with good lugs where I can specify the orientation on the lug? The place I was using in Georgia 4 years ago seems to be out of business.

 

[HighTechLab]

I don't recommend SOK's heated batteries - the non-heated are excellent but the heated ones have to be treated just right to work perfectly - most beginners don't take the time to learn how to use them properly and complain like crazy, so that's why I do not have them listed on our site. The logic for when to turn on the heating pads has been significantly improved, but still not perfect.

If you want a heated battery, I strongly recommend Epoch battery. Their BMSs have been flawless despite my many attempts to find issue. We are a dealer for them and will have them on our site when they arrive next week. They are not however, field servicable.

12V 300Ah Heated & Bluetooth LiFePO4 Battery - Epoch Essentials

Get the 12V 300Ah heated & Bluetooth LiFePO4 battery from Epoch Essentials. Charge in sub-zero conditions, control with iOS and Android apps, and enjoy the benefits of smart battery management. 4,000+ cycles, 11-year warranty.

www.epochbatteries.com

 

[sunshine_eggo]

Thanks. I checked that site but they didn't offer the batt I wanted. I just bought a couple 206AH SOKs off SOK's site. Hey, do you know a vendor where I can order some pre-made cables, like 2/0 & 4/0 stuff. Good cables, like fine stranded tinned copper with good lugs where I can specify the orientation on the lug? The place I was using in Georgia 4 years ago seems to be out of business.

I have personally used these guys:

Marine-Grade Supplies | Greg's Marine Wire Supply

Browse through the website of Greg's Marine Wire Supply today to discover more about our marine-grade products.

gregsmarinewiresupply.com

Very happy with the quality. Don't know if the price is anything special.

 

[John SK]

I have personally used these guys:

Marine-Grade Supplies | Greg's Marine Wire Supply

Browse through the website of Greg's Marine Wire Supply today to discover more about our marine-grade products.

gregsmarinewiresupply.com

Very happy with the quality. Don't know if the price is anything special.

Thanks. This the same product for about 15-20% less than were I was buying.

May I impose on you for a final question. To get the pair of SOK 206 batts (with Bluetooth) in my step well compartment, I gotta relocate two bus bars and a shunt that I installed for a Trimetric 2030 meter. When I got the Trimetric years ago, I had an AGM battery bank.

Is there any good reason to keep the shunt, since I have Bluetooth in the BMS? I have proper phones & tablets to use SOK's app. Eliminating the shunt would simplify my work.

Thanks

 

[sunshine_eggo]

Thanks. This the same product for about 15-20% less than were I was buying.

May I impose on you for a final question. To get the pair of SOK 206 batts (with Bluetooth) in my step well compartment, I gotta relocate two bus bars and a shunt that I installed for a Trimetric 2030 meter. When I got the Trimetric years ago, I had an AGM battery bank.

Is there any good reason to keep the shunt, since I have Bluetooth in the BMS? I have proper phones & tablets to use SOK's app. Eliminating the shunt would simplify my work.

Thanks

BMS aren't terribly accurate, especially for low currents < 2A. You might also have issues with BT signal if it's enclosed in metal.

Is it good enough? Probably. I'm pretty lazy, so if it makes things easier, I'd probably exclude it.