DIY LiFePO4 battery system for Camper Conversion

[Tiktaalik]

Hi Everyone!

I just joined the forum and I am relatively new to solar so I thought I’d jump into the deep end right away and build a DIY LiFePO4 System for the Camper Conversion of a Mercedes 814DA that I purchased recently.

Just to give a bit of reference, the van is the older, big brother of the sprinter van with a GVWR of 16,500 lbs and the electrical system in the van itself is 24v.

I’d love to get everyone’s feedback of my thoughts so far so that, hopefully you can steer me in the right direction.

I am considering 8-12 200Ah cells that I would assemble, balance and configure into my own DIY power bank.. Judging from Will’s LiFePO4 DIY video, 8 cells seems to be the max before you have to start configuring things a bit differently. If I decide on 10 cells, would you then arrange the system in two sets of 5 that then join together at some point? What would be the best way to configure a 10 cell LiFePO4 power bank?

There will be 1-2 fans and an AC installed on the roof but the roof is pretty big so there should still be room for 1000 - 1200w worth of solar, roughly guessing.

I definitely want the ability to also power the LiFePO4 power bank with the vehicles 24v alternator. If that means replacing the stock alternator with a marine alternator I’m ok with that or if there is room I would install a second marine alternator that is dedicated to the power bank.

The vans electrical system will remain 24v so I thought that for simplicity’s sake to also have the solar system be 24v with a step down to 12v for certain accessories like phone chargers.

Any tips, advice or thoughts on where I am headed so far? Any recommendations for how to configure this system, what 200Ah cells to get, etc?

Thanks!

 

[Dr Mark]

Sounds like a very interesting project. Looking forward to hearing about your progress. I did not built my 24V battery.

 

[Positronium]

For 25.6V nominal LiFePO4 system you need 8 cells in series; I am uncertain why you would need 10 or 12. You can go for 100A 8s BMS from Overkill Solar which includes Bluetooth module.

8s BMS 100a LifePo4 with M6 Threaded Terminals – Overkill Solar

overkillsolar.com

Batteryhookup.com has same BMS but sells Bluetooth module separately.

If you can wait for shipping try looking at the same BMS model 8s LiFePO4 100A UART from Aliexpress.

59.85US $ 10% OFF|7s 8s 24v Li Ion Or Lifepo4 Smart Bluetooth Bms With Uart Communication 80a Or 100a Constant Current Intelligent Pcb Software - Integrated Circuits - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

For 1200w of solar with 24V battery you will need a 50A Solar Charge Controller to two smaller ones.

For circuit protection buy DC breakers and fuses from reputable brands like Eaton Bussmann, Blue Sea Systems, or Carlington (MidNite Solar or Outback Solar).

Blue Sea Systems Class T fuses

Blue Sea Class T Fuses 250A to 400A

Heavy duty Class T Stud Mounted Fuse with a an extremely fast short-circuit response. For use with Blue Sea 5502 Fuse Block (not included).

powerwerx.com

Blue Sea Systems Class T fuse block

Blue Sea 5502 Class T Fuse Block with Insulating Cover 225 to 400A

Heavy Duty fuse system recommended by most inverter manufactures for high speed response to short circuits, includes clear insulating cover.

powerwerx.com

Eaton Bussmann DC Breakers link:

Eaton Bussmann 285 Series Resettable Circuit Breakers Surface Mount up to 150A

These high-amp, Type III circuit breakers are typically used in automotive auxiliary and accessory circuits for trucks, buses, RVs and marine applications. High-amp circuit breakers also have applications in battery charger systems and DC audio systems.

powerwerx.com

Panel Mounted unpolarized MidNite Solar DC Breakers link:

MidNite Solar MNEDC Circuit Breakers 150VDC

Shop now for MidNite Solar MNEDC Circuit Breakers 150VDC.

www.stellavolta.com

Polarized Din Rail Mounted MidNite Solar DC Breakers link: (typically used for PV circuits)

MidNite Solar MNEPV Circuit Breakers 150VDC 1-Pole

Shop now for MidNite Solar MNEPV Circuit Breakers 150VDC.

www.stellavolta.com

Any AC loads? I am assuming Air Conditioner. Companies are starting to bring 24Vdc air conditioners to market. You might want to look into them as you could have savings in not having an inverter or a smaller less expensive one.
Other in the forum have suggested this 24V inverter charger.

Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now!

www.electriccarpartscompany.com

There are also all in one units. This is a 24V one from Growatt

Best Price 24V Growatt SPF 3000TL LVM – 3kW 120Vac Stackable Inverter 2kW MPPT Charge Controller Split Phase 120V/240V capable with two or more units – Special – Watts247 Wholesale

watts247.com

Do you only need an AC charger? This 120V AC charger can do 37.5A for 24V.

https://www.amazon.com/AIMS-Power-CON120AC1224DC-Converter-Battery/dp/B07N1K43NQ/ref=sr_1_2?dchild=1&keywords=Aims+24V+charger&qid=1617494800&sr=8-2

This Victron 24V charger is quite good.

https://www.amazon.com/Victron-Blue-Smart-Charger-Waterproof/dp/B07TKN76V7/ref=sr_1_2_sspa?dchild=1&keywords=Victron+24V+charger&qid=1617494999&sr=8-2-spons&psc=1&smid=ACEM1DTDODKXX&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzUVRKSDI0S09MMEFFJmVuY3J5cHRlZElkPUEwMTQwODQ3M0FMTFZHWkg2MEVDOSZlbmNyeXB0ZWRBZElkPUEwMDIyMzE3MzlEMTdNM0RKNUhMUSZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

 

[ultrakiev]

Sprinter always has room for an axillary alternator; check CW Mill or BSI manufacturer for aux bracketing systems. Ten cells sound like a weird configuration...

 

[Tiktaalik]

Thanks for all those product links!

Yes, I'm definitely a little confused in terms of how to configure the size (output) of LiFePO4 battery bank. How much output does an 8 cell 24v system generally provide? What if I want more output than those 8 cells have to offer? Is the only option then to build two eight cell banks? When buying off the shelf LiFePO4 batteries it seems that you can buy as many, and make the array as large as you like. Why then can you only have 8 cells max in a DIY system? Your patience with my inexperience and confusion is appreciated.

 

[Tiktaalik]

Sprinter always has room for an axillary alternator; check CW Mill or BSI manufacturer for aux bracketing systems. Ten cells sound like a weird configuration...

Even though the 814DA is not a sprinter, there should be room. It's the one on the far right in this image.

 

[ultrakiev]

For 25.6V nominal LiFePO4 system you need 8 cells in series; I am uncertain why you would need 10 or 12. You can go for 100A 8s BMS from Overkill Solar which includes Bluetooth module.

8s BMS 100a LifePo4 with M6 Threaded Terminals – Overkill Solar

overkillsolar.com

Batteryhookup.com has same BMS but sells Bluetooth module separately.

If you can wait for shipping try looking at the same BMS model 8s LiFePO4 100A UART from Aliexpress.

59.85US $ 10% OFF|7s 8s 24v Li Ion Or Lifepo4 Smart Bluetooth Bms With Uart Communication 80a Or 100a Constant Current Intelligent Pcb Software - Integrated Circuits - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

For 1200w of solar with 24V battery you will need a 50A Solar Charge Controller to two smaller ones.

For circuit protection buy DC breakers and fuses from reputable brands like Eaton Bussmann, Blue Sea Systems, or Carlington (MidNite Solar or Outback Solar).

Blue Sea Systems Class T fuses

Blue Sea Class T Fuses 250A to 400A

Heavy duty Class T Stud Mounted Fuse with a an extremely fast short-circuit response. For use with Blue Sea 5502 Fuse Block (not included).

powerwerx.com

Blue Sea Systems Class T fuse block

Blue Sea 5502 Class T Fuse Block with Insulating Cover 225 to 400A

Heavy Duty fuse system recommended by most inverter manufactures for high speed response to short circuits, includes clear insulating cover.

powerwerx.com

Eaton Bussmann DC Breakers link:

Eaton Bussmann 285 Series Resettable Circuit Breakers Surface Mount up to 150A

These high-amp, Type III circuit breakers are typically used in automotive auxiliary and accessory circuits for trucks, buses, RVs and marine applications. High-amp circuit breakers also have applications in battery charger systems and DC audio systems.

powerwerx.com

Panel Mounted unpolarized MidNite Solar DC Breakers link:

MidNite Solar MNEDC Circuit Breakers 150VDC

Shop now for MidNite Solar MNEDC Circuit Breakers 150VDC.

www.stellavolta.com

Polarized Din Rail Mounted MidNite Solar DC Breakers link: (typically used for PV circuits)

MidNite Solar MNEPV Circuit Breakers 150VDC 1-Pole

Shop now for MidNite Solar MNEPV Circuit Breakers 150VDC.

www.stellavolta.com

Any AC loads? I am assuming Air Conditioner. Companies are starting to bring 24Vdc air conditioners to market. You might want to look into them as you could have savings in not having an inverter or a smaller less expensive one.
Other in the forum have suggested this 24V inverter charger.

Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now!

www.electriccarpartscompany.com

Do you only need an AC charger? This 120V AC charger can do 37.5A for 24V.

https://www.amazon.com/AIMS-Power-CON120AC1224DC-Converter-Battery/dp/B07N1K43NQ/ref=sr_1_2?dchild=1&keywords=Aims+24V+charger&qid=1617494800&sr=8-2

This Victron 24V charger is quite good.

https://www.amazon.com/Victron-Blue...3MzlEMTdNM0RKNUhMUSZ3aWRnZXROYW1lPXNwX2F0ZiZh

http://

Do you have a link for 24V A/C by any chance?
Most of the truly 12/24V DC compressor very small one. For a 12/24 A/C it will be built in high voltage inverter most likely. Price will be much higher then AC 110V model. DC compressor is not widely available and very expensive.Personally I would go with old school 110V Dometic or Waeco roof top unit and good quality DC-AC 3500-5000W inverter.

 

[ultrakiev]

Even though the 814DA is not a sprinter, there should be room. It's the one on the far right in this image.

Oops, I didn't pay attention. Sprinters is just so common for conversions..

 

[Tiktaalik]

Oops, I didn't pay attention. Sprinters is just so common for conversions..

No problem! Indeed they are. There's only 3-4 of these in the US right now. I'm not too worried about adding/replacing the alternator. That part I'm more familiar with.

 

[G8trwood]

Cells will be in multiples of 8 for your 24 volts. Whether 1 or more packs of 8S, or running parallel and in series 8S2P

 

[Tiktaalik]

Cells will be in multiples of 8 for your 24 volts. Whether 1 or more packs of 8S, or running parallel and in series 8S2P

Got it! The Cells themselves do come both in 100Ah and 200Ah configurations, right?

 

[GSXR1000]

Thread 'Just ordered Lifepo4 prismatic cell 3.2V 280Ah lithium lifepo4' https://diysolarforum.com/threads/j...smatic-cell-3-2v-280ah-lithium-lifepo4.14955/


I made 12v 560AH 7.3kwh battery... move the bus bars and you will have 24v 280AH 7.3kwh battery.
for AC I would say think about mini split... mounting a pain but much better for battery in surge amps and watt hour usage....

 

[GSXR1000]

how I would set up my 12v system

 

[GSXR1000]

as far as your vehicle battries can't be tied together... you can't mix lead acid and Lifepo. you will need 24v to 24v charger

 

[Positronium]

Do you have a link for 24V A/C by any chance?

I haven't looked into them, I merely have seen other forum members mention them. Did a quick search and I found this listing on Ebay. Some that I saw would not have both A/C efficiency and price. This is what I could quickly find that had both. Costs about double what a comparable 120V AC mini split would cost.

Home Mini-Split Air Conditioners for sale | eBay

Get the best deals on Home Mini-Split Air Conditioners when you shop the largest online selection at eBay.com. Free shipping on many items | Browse your favorite brands | affordable prices.

www.ebay.com

If you are knowledgeable enough the 120V mini split can be hacked to run on DC, most what I have heard convert 120V AC to 48V DC. I can't elaborate more as I have not looked into it. Or know if any work with 24V DC.

 

[G8trwood]

Got it! The Cells themselves do come both in 100Ah and 200Ah configurations, right?

Yes among others.
Read a bunch of the fact stuff as well as some of the info on marine systems. This will give you a better perspective on how the systems and cells work as well as how to protect your investment and yourself.

Good luck and great looking project. Looks like a Mog and a sprinter had a love child

 

[ultrakiev]

I haven't looked into them, I merely have seen other forum members mention them. Did a quick search and I found this listing on Ebay. Some that I saw would not have both A/C efficiency and price. This is what I could quickly find that had both. Costs about double what a comparable 120V AC mini split would cost.

Home Mini-Split Air Conditioners for sale | eBay

Get the best deals on Home Mini-Split Air Conditioners when you shop the largest online selection at eBay.com. Free shipping on many items | Browse your favorite brands | affordable prices.

www.ebay.com

If you are knowledgeable enough the 120V mini split can be hacked to run on DC, most what I have heard convert 120V AC to 48V DC. I can't elaborate more as I have not looked into it. Or know if any work with 24V DC.

The link is for drain pump.

 

[Tiktaalik]

@Positronium

Newbie question:

So if I assemble eight of the 100Ah 3.2v Cells from Overkill Solar what will be the total output capacity?

Is the math as simple as 800Ah total?

 

[Tiktaalik]

http://

Do you have a link for 24V A/C by any chance?
Most of the truly 12/24V DC compressor very small one. For a 12/24 A/C it will be built in high voltage inverter most likely. Price will be much higher then AC 110V model. DC compressor is not widely available and very expensive.Personally I would go with old school 110V Dometic or Waeco roof top unit and good quality DC-AC 3500-5000W inverter.

Dometic CoolAir RTX 2000 - Truck and campervan parking cooler, 2000 W, 24 V

Dometic CoolAir RTX 2000 - Self-contained and battery operated truck and campervan roof parking cooler. Highly efficient: only 9.5 A consumption in Eco mode. Can be installed in existing roof hatch and with a maximum tilt of 20°.

www.dometic.com

 

[Tiktaalik]

Yes among others.
Read a bunch of the fact stuff as well as some of the info on marine systems. This will give you a better perspective on how the systems and cells work as well as how to protect your investment and yourself.

Good luck and great looking project. Looks like a Mog and a sprinter had a love child

Thanks! I laughed out loud when that read that because its true. I have a soft spot for boxes on wheels.