DIY Lithium Packs, Proposal and Discussion

Midwestdrifter

Engineer In Residence
I have been considering a DIY LiFe battery pack for my van. Something in the 200-400AH range @ 12V.


Quality cells seem to be available from CALB, Fortune (frey) etc. A user over on ExPo recently ordered 16 100ah cells factory direct from Frey. Only $1600 delivered, and came with factory test reports.
https://expeditionportal.com/forum/...tteries-vs-drop-in-replacements.198005/page-4

I have an existing electrical system consisting of Outback inverter, Solar CC, Mate, and FlexnetDC battery monitor. This system is not super configurable (unlike Victron), but it can be programmed to charge lithium batteries suitably.


My major needs to build a diy pack, are monitoring system with cell voltage and temp monitoring. One that can trigger a pack disconnect. Likely a gigavac latching relay, or their high efficiency NO relays (0.3A at 12VDC).

Anyone have a suggestion for a reasonably priced BMS that can provide temp and voltage disconnect? I don't need remote monitoring or a fancy screen, just a last case safety system.

Balancing would be nice, but is not required. If I feel its necessary, one of these 4s balance boards would do the trick.

The Orion Jr BMS would meet my needs, but is pretty pricey at ~$550. It has lots of functionality that I don't need. Regardless the BMS must have programmable setpoints. I could rely on the active balance boards, and just use a pack level disconnect, but that creates a single failure point that is not protected.


A pack heater would just be a ~100w silicone heating pad with electronic standalone thermostat, and mechanical overtemp protection.


This would yield a pack with much higher peak current than the drop-ins with solid state relays. Though the trojan units with normal relays would be about the same. Those are around 1k per 100AH. $1600+$700 in materials would yield a 400AH pack with much higher rates. If a cell fails, it can be replaced without trashing the whole pack.

The primary goal is for this to be the last pack this van will ever need. I don't want to be dependent on some untested (though likely reliable) electronics buried in a 1000$ battery. I don't want the complexity and issues that come from having 2-4 parallel BMS. The Tesla modules are nice, but I don't want to completely rework my electrical system for 24VDC.
 
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Midwestdrifter

Engineer In Residence
Looking at other options, I found this utility oriented stand-alone BMS. 475$ plus wiring harness. Can handle up to 12 cells. Passive balancing up to 300mA, 4 contactor driver circuits, and 8 temperature probes. A built-in ethernet port can be used to program the unit, and the software seems quite flexible, if a bit difficult to learn.

It also has a modbus and CANbus2.0 ports...

https://nstore.nuvationenergy.com/c...low-voltage-bms-battery-controller-12-channel
https://www.nuvationenergy.com/site...-Low-Voltage-Battery-Controller-Datasheet.pdf
 

Midwestdrifter

Engineer In Residence

owner

Well-known member
My ghetto $5 paralleled balance boards have been working really well on my 40Ahx4 DIY bank . They have been called into action a few times to cut the pack voltage when I have left something switched on accidentally. They have run 100A+ loads several times (way more than I envisaged), and have been charged at 80A+ at times.

And i have now checked the balance yesterday (after a full season of use/abuse) with an external balancer, and they were all still very close voltages - within 0.006V.
https://www.ebay.com.au/itm/12V-100...Battery-Protection-Circuit-Board/292915687394
 
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bcman

Member
I bought CALB cells through Electric Car Parts Company in Salt Lake City and picked them up from the distribution center in Southern CA. I also bought from ECPC a HousePower MiniBMS from CleanPowerAuto, which is now defunct as the owner went to work for Lithionics. I've been happy with the HousePower BMS, although it has some shortcomings. It has protection for over- and under-voltage, and will top balance. On the other hand, voltages are not configurable, and there's no temperature protection. I ended up installing a Victron BMV-702 with temperature sensor and VE.Direct Non Inverting Remote On-Off Cable to shut off charging sources below freezing temps.

ECPC has a few BMS options, including a house brand that seems like it provides temp control, as well as an optional connection for charging sources (for over-voltage, only shuts off charging sources, not loads). The documentation is ambiguous about cell balancing. And I don't think voltages are adjustable.

ANother one I've looked at is Electrodacus. BMS, battery monitor, and MPPT solar controller all in one. May not be as cost effective for you since you have those components already, but might be an affordable option for someone building up a house electrical system from scratch.
 
If you get the process ironed out, you can build me a lithium bank when I get back from South America!!!
 

Midwestdrifter

Engineer In Residence
If you get the process ironed out, you can build me a lithium bank when I get back from South America!!!
Sure, I've got 2-3 options I am slowly fleshing out. 18 months from now is probably a good time line, as I've got a 4x4 conversion to iron out.
 

Midwestdrifter

Engineer In Residence
Circling back to this.

Here is a rough breakdown. I will reuse most of my existing gear, shunt, fuses etc. This will yield 400AH @12V nominal. Discharge at 400A, and charge at 200A if necessary. Pack will have BMS controlled heaters and an insulated box (removable lid/vent for warm weather?). Pack will have a single master disconnect contactor, which will be emergencies only. There will be a visual caution and audible alarm output on the BMS. The orion BMS has extensive self checking routines, including redundant temp sensors, and it will drop out and alarm if the voltages from all the inputs don't jive. If it locks up and goes dead the system will drop the main contactor. The charge sources will all be configured to absorb for a short period then end the charge. Except the alternator. I already have a ACR, which can be manually controlled. So I will just wire that to the charge control output of the BMS.

Code:
Item	                  Qty	 Cost 	Total
Orion Jr BMS	        1   	 $450 	 $450 
100AH Frey Cells	16	 $100 	 $1,600 
Blue Sea 7713 Contactor	1	 $200 	 $200 
Cell connectors/fuses	1	 $200 	 $200 
Heating pads	        2	 $100 	 $200 
Box materials/Insulation  1	 $100 	 $100 
		Grand Total	 $2,750
Cost wise I am about 1000$ under 4x battleborne drop-ins. I do have direct access to the BMS, and I can fix things if they break. Its not a huge gain over the drop-ins for cost.
 

OrioN

2008 2500 170" EXT
Circling back to this.

Here is a rough breakdown. I will reuse most of my existing gear, shunt, fuses etc. This will yield 400AH @12V nominal. Discharge at 400A, and charge at 200A if necessary. Pack will have BMS controlled heaters and an insulated box (removable lid/vent for warm weather?). Pack will have a single master disconnect contactor, which will be emergencies only. There will be a visual caution and audible alarm output on the BMS. The orion BMS has extensive self checking routines, including redundant temp sensors, and it will drop out and alarm if the voltages from all the inputs don't jive. If it locks up and goes dead the system will drop the main contactor. The charge sources will all be configured to absorb for a short period then end the charge. Except the alternator. I already have a ACR, which can be manually controlled. So I will just wire that to the charge control output of the BMS.

Code:
Item	                  Qty	 Cost 	Total
Orion Jr BMS	        1   	 $450 	 $450 
100AH Frey Cells	16	 $100 	 $1,600 
Blue Sea 7713 Contactor	1	 $200 	 $200 
Cell connectors/fuses	1	 $200 	 $200 
Heating pads	        2	 $100 	 $200 
Box materials/Insulation  1	 $100 	 $100 
		Grand Total	 $2,750
Cost wise I am about 1000$ under 4x battleborne drop-ins. I do have direct access to the BMS, and I can fix things if they break. Its not a huge gain over the drop-ins for cost.
Is your "Single Master Disconnect Contactor" the same BS 7713?
 
Circling back to this.

Here is a rough breakdown. I will reuse most of my existing gear, shunt, fuses etc. This will yield 400AH @12V nominal. Discharge at 400A, and charge at 200A if necessary. Pack will have BMS controlled heaters and an insulated box (removable lid/vent for warm weather?). Pack will have a single master disconnect contactor, which will be emergencies only. There will be a visual caution and audible alarm output on the BMS. The orion BMS has extensive self checking routines, including redundant temp sensors, and it will drop out and alarm if the voltages from all the inputs don't jive. If it locks up and goes dead the system will drop the main contactor. The charge sources will all be configured to absorb for a short period then end the charge. Except the alternator. I already have a ACR, which can be manually controlled. So I will just wire that to the charge control output of the BMS.

Code:
Item	                  Qty	 Cost 	Total
Orion Jr BMS	        1   	 $450 	 $450 
100AH Frey Cells	16	 $100 	 $1,600 
Blue Sea 7713 Contactor	1	 $200 	 $200 
Cell connectors/fuses	1	 $200 	 $200 
Heating pads	        2	 $100 	 $200 
Box materials/Insulation  1	 $100 	 $100 
		Grand Total	 $2,750
Cost wise I am about 1000$ under 4x battleborne drop-ins. I do have direct access to the BMS, and I can fix things if they break. Its not a huge gain over the drop-ins for cost.
Looks like you've done your homework. As you get more into the project, it would be helpful to get an idea of the labor cost involved if a layperson, like me, had to pay someone for a bank like this. I haven't studied lithium much, but I'm assuming I'd have the bank built. I could most likely install the bank once it was built. The labor will be the deciding factor of built vs. drop in.
 

Zoomyn

Member
Beware specifying heater power - if those cells are about ~5 pounds of Li Fe Po and various salts etc they do not need the same energy as we'd imagine water would require...

Example is 80 pounds in water would require 240w constant input for one hour to be heated 10°F --- but those 80 pounds in concrete would only require a constant 42w heat input...

http://chuck-wright.com/calculators/watts.html <--- amazing little energy units conversion with a few real world examples...
 

Midwestdrifter

Engineer In Residence
Looks like you've done your homework. As you get more into the project, it would be helpful to get an idea of the labor cost involved if a layperson, like me, had to pay someone for a bank like this. I haven't studied lithium much, but I'm assuming I'd have the bank built. I could most likely install the bank once it was built. The labor will be the deciding factor of built vs. drop in.
I will let you know. There is significant labor with making the harness and bolting everything up, making a box, etc.

Beware specifying heater power - if those cells are about ~5 pounds of Li Fe Po and various salts etc they do not need the same energy as we'd imagine water would require...

Example is 80 pounds in water would require 240w constant input for one hour to be heated 10°F --- but those 80 pounds in concrete would only require a constant 42w heat input...

http://chuck-wright.com/calculators/watts.html <--- amazing little energy units conversion with a few real world examples...
Yes, I am aware that lithium has a lower specific heat than water. I ran through the calcs previously. Regardless the primary controlling factor in the heaters output is the box insulation and the temps I want to operate it in. Basically I start with a wattage that will keep the pack warm at that temp. Then I will add enough extra power to warm the pack from ambient in an hour or two.

Have you looked at the following, 420ah for $2700 + shipping + heating pads?

https://www.pikavo.com/batteriespv/batteriespv/4-lion-bundle-420ah-53kwh

Sent from my iPad using Tapatalk
I am seeing 3,600$ on that link.

Thus is the issue with the drop ins. They have minimal history (that brand is shorter than many), and the lifetime warranty has yet to be tested. Plus they are a black box. If they have a failure, which is modestly possible over 5+ years of service, the only remedy is warranty replacement, or hacking them apart. With regards to that specific battery, there is no monitoring, no bluetooth, no status LED. With 4x in parallel, I would have no warning when one dropped out, and in fact I would have no way of knowing that only 3 were providing all the current.

My biggest issue is that all these drop-ins use an internal FET based disconnect/relay/contactor setup. These generate significant heat, and are the primary source of failures. I much prefer a physical contactor, or at least something I can replace in the field, like a drop-in board or something like that.

Anyways, not trying to knock drop-ins, but there are definite downsides for my application. Of course having 4x batteries provides some redundancy, so I could get over the multiple parallel BMS/black box issue. But the lack of longer history is a stopping point currently. Maybe when a specific brand has 50k units in service for 5 years?

I do like the higher level of flexibility provided by access to the BMS
 
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I will let you know. There is significant labor with making the harness and bolting everything up, making a box, etc.
Thanks MWD. New info since our last chat. I completed a major propane mod that allowed me to eliminate the existing 80# fixed underslung LP tank just behind/under the driver. This creates a great space to build a battery/utility compartment and bolt it up using the same holes/brackets as the tank.

Your comments about the benefits of building a bank for international overlanding make sense to me.
 

gltrimble

Well-known member
I am seeing 3,600$ on that link.

Thus is the issue with the drop ins. They have minimal history (that brand is shorter than many), and the lifetime warranty has yet to be tested. Plus they are a black box. If they have a failure, which is modestly possible over 5+ years of service, the only remedy is warranty replacement, or hacking them apart. With regards to that specific battery, there is no monitoring, no bluetooth, no status LED. With 4x in parallel, I would have no warning when one dropped out, and in fact I would have no way of knowing that only 3 were providing all the current.

$2700 with $900 coupon code per above link for the 105 ah Lion Safari battery. They do have LED status indicators, BMS, and are fairly easy to disassemble per a Youtube review of their earlier 90/100 ah battery. The same reviewer felt the internal components were high quality. I like the fact that they are compact (group 24) and only 23 lbs compared to 30+ lbs for the Battleborns (also available for discount from same supplier).

However, my biggest concern is lack of history as you mentioned. How long will the company be around to warranty the battery. A number of forum members have purchased these batteries so hopefully there will be some feedback in the coming months.



Sent from my iPad using Tapatalk
 
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