[cvollers]

I have been pretty stuck on using the Victron 200Ah LiFePO4 (12.8V) smart battery for my camper van build house battery. Not because it is smart (or expensive), but because it has the smallest footprint (physical dimensions) of any 200Ah LiFePO4 battery on the market and 200Ah is my bare minimum for house battery capacity. Perhaps that is why it is so expensive. I need the small footprint because of the limited space the battery is being installed in.

Recently I was made aware of DIY LiFePO4 options using prismatic cells that can deliver more capacity in the same or smaller footprint at potentially less cost. @CaptainUnderpants was kind enough to share this link: USA STOCK FAST UPS DELIVERY HiGee LF120 120Ah 3.2V LiFePO4 Prismatic Battery Cell Laser Welded Terminal Stud.

I'd like to stay at 12.8V. If I buy four of these cells, does that get me 480Ah at 12.8V? Also, does anyone have a link to a resource that shows how to build/wire a DIY prismatic cell battery?

 

[CaptainUnderpants]

If you use 4 x 120 amp hr 3.2 volt cells to make a 12.8v battery, you will have a 12.8v 120 amp hr battery. If you use these 4 of these 3.2 volt 304 amp hr batteries you will have a 12.8 volt 304 amp hr battery. This will be 50% bigger than your proposed 200ah Victron Battery. It will cost less than $1,000 to build this battery. Approximate size using the 304 amp hr cells will be 12" x 8" x 10 ".

P (Power - Watts) = I (Amperage) x V (Volts)
Energy = Watts x Hours

Something like this

 

[cvollers]

If you use 4 x 120 amp hr 3.2 volt cells to make a 12.8v battery, you will have a 12.8v 120 amp hr battery. If you use these 4 of these 3.2 volt 304 amp hr batteries you will have a 12.8 volt 304 amp hr battery. This will be 50% bigger than your proposed 200ah Victron Battery. It will cost less than $1,000 to build this battery.

P (Power - Watts) = I (Amperage) x V (Volts)
Energy = Watts x Hours

Perfect! I found this YT vid that explains parallel versus series battery cell configuration:

With 4S, you get 4X the voltage of a single cell, but the overall capacity is equal to single cell capacity just as you stated above. Four cells, two compression plates, three bus bars, threaded rods with tubing, a Lexan cover plate and you're done.

I already was planning to have a Victron BMS as part of the overall build. I may elevate the battery slightly to create some airspace underneath.

 

[CaptainUnderpants]

You've got it!! Not sure if a Victron BMS works with this type of set up. A typical 4 cell BMS will have 5 small wires on it to manage individual cell voltages and keep them balanced.

I think a Victron BMS only works with a Victron battery?

I use Overkill BMS's and can monitor the batteries with the Overkill iphone App. This app shows both BMS's (I have 2 x 4 cell 12 volt batteries) and each individual cells voltage. Or I can use the Victron Connect app to monitor my shunt which shows the overall total charge of the battery bank.

 

[njvagabond]

Overkill BMS's

Overkill has a great document on there site for anyone interested in building a DIY battery.

 

[CaptainUnderpants]

SOK batteries are probably the closest things to DIY prismatic builds. In this video you can see the interior structure is the same. If I didn't do the DIY battery, this is probably the direction I would have gone.

 

[CaptainUnderpants]

I have been pretty stuck on using the Victron 200Ah LiFePO4 (12.8V) smart battery for my camper van build house battery. Not because it is smart (or expensive), but because it has the smallest footprint (physical dimensions) of any 200Ah LiFePO4 battery on the market

I think the SOK 12v 206 amp hr battery is the same size.

Victron - 321 x 237 x 152 (I think the Victron needs an additional BMS.
SOK - 275 x 200 x 255

 

[cvollers]

You've got it!! Not sure if a Victron BMS works with this type of set up. A typical 4 cell BMS will have 5 small wires on it to manage individual cell voltages and keep them balanced.

I think a Victron BMS only works with a Victron battery?

I use Overkill BMS's and can monitor the batteries with the Overkill iphone App. This app shows both BMS's (I have 2 x 4 cell 12 volt batteries) and each individual cells voltage. Or I can use the Victron Connect app to monitor my shunt which shows the overall total charge of the battery bank.

I'll check Overkill out...thanks for the tip!

 

[cvollers]

I'll check overkill out...thanks for the tip!

Based on what I'm seeing in the Overkill BMS manual, the Victron Battery Protects (BP65) I was planning to use for load and charge protection most likely aren't necessary. The BMS will provide all the battery protection required and fuses will protect the loads. I will be using the optional switch as I was planning to do that with the Victron BMS.

 

[gregoryx]

Size was a factor in our decisions. We're running two of these units for the equivalent of ~680A @ 12VDC (20x10x7 per ~4kWh). A friend is running one of these for over 200A in 10x13x7.5 space. He ended up adding a second unit as well. Compared to the Victron (9.3x12.6x6 inches), they're pretty close but include the BMS, an on/off switch, and a fuse - all inside the enclosures.

SOK seems like the way to go now for the size and features (8x8x18). I really like the EG4-LL units... but they are larger. If you really want to save space, build your own as @CaptainUnderpants did - but recognize that the BMS and all the other bits and bobs (that are also not included with the Victron batteries) take up more space and increase the challenges.

If you're decide to build your own pack, I'd say Overkill is a great way to go. Rec-BMS is another option. Both of them have been integrated with Victron GX - meaning you don't need a smart-shunt as the BMS will communicate it's state natively - though you'd need to verify what features get pulled in and which don't. Personally, integration is the main reason I'd go DIY pack: to be able to communicate the /actual/ battery state up to the charging systems.

As you may have realized now, the Victron batteries are small because they're natively stupid; they depend on and require the external BMS to be smart (and to keep from burning them up, technically). But that allows them to be small compared to all the options that include the BMS and/or other features. You will ideally include fuses and/or circuit breakers and/or on/off switches for each battery for safety and diagnostic reasons. Much like the BMS, all of these things will take up space - and they'll take up more space and be more challenging to install if they're not integrated.

That last bit (fuses, breakers, switches) is one of the arguments in favor of using 24V storage: twice the voltage is half the amperage for the same power; meaning smaller gauge cable and fuses, switches, breakers, etc. If you'll be running an inverter with more than 2kW output, you might want to consider 24V. It requires adding a 24>12 converter, but that has the benefit of delivering steady voltage even as the lithium charge cycle pushes the actual voltage up higher than some devices want.

 

[jkmann]

I have been pretty stuck on using the Victron 200Ah LiFePO4 (12.8V) smart battery for my camper van build house battery.

I have four of the Victron 200Ah SmartBatteries. They use bluetooth to communicate with Victron Connect, so you have a lot of diagnostics for each battery without having to isolate it. I used the V.E.Bus BMS, which is tiny, and integrates directly with a multiplus, as well as providing the Allowed to Charge and Allowed to Discharge signals to other Victron components. If you have an all-Victron install the batteries integrate seamlessly.

 

[cvollers]

I have four of the Victron 200Ah SmartBatteries. They use bluetooth to communicate with Victron Connect, so you have a lot of diagnostics for each battery without having to isolate it. I used the V.E.Bus BMS, which is tiny, and integrates directly with a multiplus, as well as providing the Allowed to Charge and Allowed to Discharge signals to other Victron components. If you have an all-Victron install the batteries integrate seamlessly.

Wow. That’s a $8K+ electrical system just for the battery bank. I wasn’t planning to go all Victron (just partial Victron) so the benefits of the seamless integration most likely would have been lost. Sounds like you have a great system.

 

[cvollers]

You've got it!! Not sure if a Victron BMS works with this type of set up. A typical 4 cell BMS will have 5 small wires on it to manage individual cell voltages and keep them balanced.

I think a Victron BMS only works with a Victron battery?

I use Overkill BMS's and can monitor the batteries with the Overkill iphone App. This app shows both BMS's (I have 2 x 4 cell 12 volt batteries) and each individual cells voltage. Or I can use the Victron Connect app to monitor my shunt which shows the overall total charge of the battery bank.

I'm all in with the prismatic cell option. Here is what it looks like in our PowerSlide drawer with the Overkill BMS mounted to the drawer divider wall. I think I'll still use the Victron shunt with their smart battery monitor. Blue Sea main battery switch. The blue box is the Xantrex inverter/charger. The gray box is the Blue Sea SafetyHub which gets positive from the switch and the inverter/charger (200A fuse) then distributes to a fuse block off the drawer. A 250A terminal fuse will be located at the battery main positive terminal (to the left on the battery). Not shown are the myriad smaller wires needed to make all this work.

 

[CaptainUnderpants]

Nice work. SketchUp? Since it is going to be put in a box, you may not really need the compression plates. I watched one video where the cells were compressed and then wrapped with a tape that had some structure to it. This will certainly save some money.
Here are some resources for you.
OGSolar Compression Plates - I had these powder coated (In SoCal - Specialized Coatings in Huntington Beach - They did an amazing job). Before powder coating I drilled two holes in the upper flange for carrying straps and inserted 4 rivnuts in the upper flanges as well to secure a lexan cover.
Tap Plastics - Cut to size - You will want to use Lexan, as this won't crack when you drill holes.
Bolt Depot - Threaded Stainless Rod - I went with metric threaded rod. You might find it cheaper if bought locally. This was then covered with 1/4" tubing.
Overkill Solar - 12v 4s without wires - This is rated at 120a continuous charge or discharge. I have read that 200 amps peak is not a problem as well. So this will probably work with your inverter. I would suggest the 60 amp Renogy charger for best bang for the buck.
Temco Industries - I bought all of my wire, crimp fittings and crimping tools from Temco. Good quality, good prices and quick delivery.
Power Supply - You may want one of these to top balance your cells.
Docan Power 304 Cells - I would recommend these cells. I would also recommend ordering from US Stock. I ordered from China and it took 45 days, which is just a very long time when you are anxious to put things together. Plus the differential isn't as much when you factor in shipping.
Cell Separators - This is what I used to separate the cells. Unfortunately min order is 10. There are plenty of other cheaper alternatives.

 

[njvagabond]

tape that had some structure to it

I think it is called Kapton tape.

 

[CaptainUnderpants]

I think it is called Kapton tape.

I did use Kapton Tape for preventing any arc's or shorts by covering terminals. It is clear yellow / orange in color. This tape is very flexible and has no fibers in it, therefore unable to hold compression. Maybe something more like this Scotch Shipping Strapping Tape.

 

[njvagabond]

FWIW - two things I liked a lot about the SOK batteries are the metal case and crush space clearance in the design. No doubt it increases the size.

 

[cvollers]

Nice work. SketchUp? Since it is going to be put in a box, you may not really need the compression plates. I watched one video where the cells were compressed and then wrapped with a tape that had some structure to it. This will certainly save some money.
Here are some resources for you.
OGSolar Compression Plates - I had these powder coated (In SoCal - Specialized Coatings in Huntington Beach - They did an amazing job). Before powder coating I drilled two holes in the upper flange for carrying straps and inserted 4 rivnuts in the upper flanges as well to secure a lexan cover.
Tap Plastics - Cut to size - You will want to use Lexan, as this won't crack when you drill holes.
Bolt Depot - Threaded Stainless Rod - I went with metric threaded rod. You might find it cheaper if bought locally. This was then covered with 1/4" tubing.
Overkill Solar - 12v 4s without wires - This is rated at 120a continuous charge or discharge. I have read that 200 amps peak is not a problem as well. So this will probably work with your inverter. I would suggest the 60 amp Renogy charger for best bang for the buck.
Temco Industries - I bought all of my wire, crimp fittings and crimping tools from Temco. Good quality, good prices and quick delivery.
Power Supply - You may want one of these to top balance your cells.
Docan Power 304 Cells - I would recommend these cells. I would also recommend ordering from US Stock. I ordered from China and it took 45 days, which is just a very long time when you are anxious to put things together. Plus the differential isn't as much when you factor in shipping.
Cell Separators - This is what I used to separate the cells. Unfortunately min order is 10. There are plenty of other cheaper alternatives.

This is super helpful…thanks! Yes, SketchUp. I use it for all my designing/planning. Sometimes I even get lucky and find the 3D component model in their Warehouse. When I don’t, I just DIY it.

I’m going to need the compression plates as the box it is going in will be quite a bit larger than the battery.

 

[GotDiesel?]

I think that with some of the stories that I have been seeing about fires caused by lithium batteries, this whole idea of mashing together components to make a battery seem like risky business. Maybe some of the ideas here are valid and have safety as a primary consideration. But, there is no way I would want to see my whole van conversion transformed into a lump of molten metal because I thought I was smarter than I really am.

I went with a Victron system and 400Ah of their lithium batteries because I hoped that their engineering offered the best shot at trouble free energy storage. I still can find time to worry about the runaway battery fire. So....that's just me, I guess.

 

[CaptainUnderpants]

I think that with some of the stories that I have been seeing about fires caused by lithium batteries, this whole idea of mashing together components to make a battery seem like risky business. Maybe some of the ideas here are valid and have safety as a primary consideration. But, there is no way I would want to see my whole van conversion transformed into a lump of molten metal because I thought I was smarter than I really am.

I went with a Victron system and 400Ah of their lithium batteries because I hoped that their engineering offered the best shot at trouble free energy storage. I still can find time to worry about the runaway battery fire. So....that's just me, I guess.

I think you are confusing some of the original Lithium batteries with the newer LiFePO4 batteries which are much more stable.
https://relionbattery.com/knowledge/how-are-lifepo4-batteries-safer-than-other-lithium-batteries

From BatteryStuff.com
Lithium-Ion is LiCoO2, or Lithium Cobalt Oxide. In this chemistry, the oxygen is not strongly bonded to the cobalt, so when the battery heats up, such as in rapid charging or discharging, or just heavy use, the battery can catch fire.

The LiFePO4 batteries are the safest type of Lithium batteries as they will not overheat, and even if punctured they will not catch on fire. The cathode material in LiFePO4 batteries is not hazardous, and so poses no negative health hazards or environmental hazards. Due to the oxygen being bonded tightly to the molecule, there is no danger of the battery erupting into flames like there is with Lithium-Ion. The chemistry is so stable that LiFePO4 batteries will accept a charge from a lead-acid configured battery charger. Though less energy-dense than the Lithium-Ion and Lithium Polymer, Iron and Phosphate are abundant and cheaper to extract so costs are much more reasonable. LiFePO4 life expectancy is approximately 5-7 years.

Both your Victron and the proposed DIY batteries use LiFePO4 chemistry. This is the big factor in safety. Fuses, a quality BMS, properly sized wire and quality crimps are likely your second line of defense. The pretty blue plastic Victron case will only add to the toxic fumes should your van catch on fire. 😊 Not knocking the pretty blue, it's on most of my electronics.