DIY 100ah lithium battery

[ski3pin]

A couple years back a few members here built their own batteries by assembling lots of little cylinders. What would you use today? I saw this Will Prowse youtube -

Are these good ingredients? What are other options?

I'm not committed at this point but am curious enough to ask.

Thanks.

 

[Jack]

I built my LiFePO4 battery and have been very happy with it. 280Ah cost about $750. Since my Fleet front dinette has limited battery space, I needed to spend a lot of effort and time making a case for the cells that would fit in the battery compartment and have a reasonable way of maneuvering it. Making the case and mounting the batter management system takes the most time. You want a case that lets you maneuver the battery into and out of your battery compartment. Assembly and wiring and setting parameters takes a few hours. Balancing the cells takes another few hours. But there's no Amazon prime. Figure 30 to 40 days to get your cells and BMS.

Assembly is not complicated, but you should be knowledgeable and comfortable working with electricity. The major issue is the energy in the battery (any battery, for that matter). Short it out and and you risk serious fire and injury.

https://www.wanderthewest.com/forum/topic/20568-new-lithium-battery-%E2%80%93-some-assembly-required/?hl=%2Bsome+%2Bassembly+%2Brequired

$280 Ah is much more than we need except for one appliance. We are giving the ZeroBreeze Mark II 2000BTU A/C a try this summer. As our age has increased, our tolerance for temperature has decreased. We lived in St. Louis for 4 years some time ago and tolerated the summer temperatures there - and with a car without A/C. We now like to avoid temperatures that are above 85F for any length of time.

If you are looking to build a smaller capacity battery, google search the various RV/expedition forums for LiFePO4 DIYers to find sources for cells. For a modest bump in price and much shorter time, check out https://overkillsolar.com/ I think Will Prowse also has source links for a 100Ah battery.

 

[kmcintyre]

I've built one and posted a lot of info on where I got the "cells" and parts I used. It's really pretty easy. The hard part is the terminology and getting the settings right.

I've used mine on about 10 trips so far. No issues once I got the charging profiles dialed in and the DC-to-DC charger and BMS.

That Will Prouse video is still quite old. His videos, etc. are great. It's directly mainly for solar but still helps a lot to see his "reviews" and suggestions, tests.

 

[ski3pin]

I've built one and posted a lot of info on where I got the "cells" and parts I used. It's really pretty easy. The hard part is the terminology and getting the settings right.

I've used mine on about 10 trips so far. No issues once I got the charging profiles dialed in and the DC-to-DC charger and BMS.

That Will Prouse video is still quite old. His videos, etc. are great. It's directly mainly for solar but still helps a lot to see his "reviews" and suggestions, tests.

Searching back through topics here on Wander the West, I believe I've sorted out that this was your source and with two options, one you used for a 120ah battery -

3.2v120ah

and another option if I decided 100ah -

3.2v100ah

Am I correct? Thank you.

 

[rando]

I have been using my 150Ah DIY lithium (with 120 cylindrical cells) for going on 4 years now and it has worked wonderfully. If I were to do it again, I would use the 120Ah prismatic cells that are currently available at very competitive prices. These were not cost competitive 4 years ago.

Building the battery is very straightforward - but you need to respect the energy that is contained in the batteries. There are a few caveats:
1. You want to have a way to 'top balance' the batteries you purchase before you install them. This is usually done by connecting them all in parallel and charging them to 3.5V with an adjustable power supply. You may be able to get away without doing this, but omitting this seems to be a leading cause of future problems.
2. You want to clamp the batteries together, to prevent them swelling.
3. You should place some sort of insulator (eg 1/8" plastic sheet) between the cells. The metal cases are also the battery negative, so if you were to damage the blue heat shrink wrap, you risk shorting out the batteries and a fire. You should also cover the exposed terminals on the cells.
4. You need to set up your BMS correctly.

 

[kmcintyre]

Searching back through topics here on Wander the West, I believe I've sorted out that this was your source and with two options, one you used for a 120ah battery -

3.2v120ah

and another option if I decided 100ah -

3.2v100ah

Am I correct? Thank you.

Yes, I think that's correct but I used the 120ah version.

I have a write up that I did if you'd like it. Just PM your email as I don't know how to post the entire thing here.

Kevin

 

[ski3pin]

Jack, kmcintyre, and rando thanks for the information!

 

[ski3pin]

An update. I put in an order through alibaba for 4 of the 120ah cells that member kmcintyre used. This was my first experience with alibaba. I received only one response from China suppliers. The cost was $43 a piece plus $114 to get it here making a total around $280. Prices are up. Add in a BMS and cost for a DIY is approaching the sale price on the Renogy battery and the SOK that Will Prowse gave favorable reviews. Note, these are both 100ah batteries.

I considered the SOK because it can be disassembled and parts replaced.

I'm going ahead with a DIY mainly for the learning experience and I like to understand how things work.

Thanks all for the information and insights.

 

[Stokeme]

I posted a thread about this dealer a few days ago. This video (link) also posted may be helpful in construction.

 

[Stokeme]

Why I love included internal Bluetooth w/BMS. Note ... there are many free Apple apps from other battery dealers. I have found several that work universally with both my batteries from 2 different (now defunct) companies. Some are basic, some are the latest, advanced tech. The graphics/format on some are impressive.

 

[kmcintyre]

An update. I put in an order through alibaba for 4 of the 120ah cells that member kmcintyre used. This was my first experience with alibaba. I received only one response from China suppliers. The cost was $43 a piece plus $114 to get it here making a total around $280. Prices are up. Add in a BMS and cost for a DIY is approaching the sale price on the Renogy battery and the SOK that Will Prowse gave favorable reviews. Note, these are both 100ah batteries.

I considered the SOK because it can be disassembled and parts replaced.

I'm going ahead with a DIY mainly for the learning experience and I like to understand how things work.

Thanks all for the information and insights.

I think you'll like them. It'll take a while to get them.
The next thing will be getting the app installed and figuring out all the settings assuming you got the bluetooth BMS.

I'm not sure what prices you see for those other battery packs on sale but you should be around $325 for your 120ah cells and BMS which is about what I have spent on AGM batteries.

Have fun!

Kevin

 

[Lunch]

Hey Ski3pin,

Just saw this thread. Will be following your DIY project. If successful, maybe we can work on the next one together. Remember that table top you helped me build? When Li-Polymer prices drop and life cycles increase, we can build another table top that also houses a LI-Po battery.

I was going to go the DIY route but was worried about the BMS. I was pretty confident about cell quality but not about third party BMS and BMS systems. Just too much at stake and I knew that I would always worry about it. I know lots of people have successfully incorporated these BMS' into their builds and I am happy for them. I guess I am just a little more risk averse.

I called up Battleborn and spoke with the chief engineer (well, I assume he was an engineer b/c he didn't usually talk to people). I asked him lots of technical questions about the cells and BMS and he answered them pretty quickly and with a lot of confidence. And he gave me a nice discount. Good enough for me.

Another decision factor was the resale value. Battleborn claims 3k-5k life cycles. It's common practice in the industry to understate battery service life (BB even recognizes the actual lifetime cycles will likely be higher on their webpage). I assume in their testing they discharged to 80% DOD (lower than I ever get) and charged faster than I do (0.3C on DC-DC and 0.4C on charger/inverter). So, maybe my battery will last even longer, say 6k cycles minimum. So, in theory, I could pull ~80 A every day for almost 16.5 years or, more realistically, 20 Ah about 70 times/yr for about a billion years. So, when a new battery technology leader emerges I will be first in line and will hopefully be able to sell my current BB.

BTW, I don't usually watch Will's vids (energy level is a little too high for me). But it was cool to see him dissect the BB and give it a positive review.

 

[lmwilco1]

Have you already ordered a BMS? I have an extra one you can have if you pay shipping. It is rated at 100A draw and has bluetooth.

Link to the BMS: https://batteryhookup.com/products/12v-lifepo4-smart-bms-w-low-temp-cutoff?rfsn=2267412.b1bf25

Louis

 

[ski3pin]

Have you already ordered a BMS? I have an extra one you can have if you pay shipping. It is rated at 100A draw and has bluetooth.

Link to the BMS: https://batteryhookup.com/products/12v-lifepo4-smart-bms-w-low-temp-cutoff?rfsn=2267412.b1bf25

Louis

Louis, thank you but mine arrived weeks ago. That is a very kind offer and I appreciate it.

 

[ski3pin]

Hey Ski3pin,

Just saw this thread. Will be following your DIY project. If successful, maybe we can work on the next one together. Remember that table top you helped me build? When Li-Polymer prices drop and life cycles increase, we can build another table top that also houses a LI-Po battery.

I was going to go the DIY route but was worried about the BMS. I was pretty confident about cell quality but not about third party BMS and BMS systems. Just too much at stake and I knew that I would always worry about it. I know lots of people have successfully incorporated these BMS' into their builds and I am happy for them. I guess I am just a little more risk averse.

I called up Battleborn and spoke with the chief engineer (well, I assume he was an engineer b/c he didn't usually talk to people). I asked him lots of technical questions about the cells and BMS and he answered them pretty quickly and with a lot of confidence. And he gave me a nice discount. Good enough for me.

Another decision factor was the resale value. Battleborn claims 3k-5k life cycles. It's common practice in the industry to understate battery service life (BB even recognizes the actual lifetime cycles will likely be higher on their webpage). I assume in their testing they discharged to 80% DOD (lower than I ever get) and charged faster than I do (0.3C on DC-DC and 0.4C on charger/inverter). So, maybe my battery will last even longer, say 6k cycles minimum. So, in theory, I could pull ~80 A every day for almost 16.5 years or, more realistically, 20 Ah about 70 times/yr for about a billion years. So, when a new battery technology leader emerges I will be first in line and will hopefully be able to sell my current BB.

BTW, I don't usually watch Will's vids (energy level is a little too high for me). But it was cool to see him dissect the BB and give it a positive review.

Mr. Lunch, I expect the chief engineer at Battleborn was very pleased to speak with someone with your credentials, expertise and background.

I have all the components now except for the cells.

I'd be happy to play with electricity with you. Anytime!

But first off, you two need to tag along with Julie and me on a Death Valley area adventure in the winter.

 

[ski3pin]

An update -

I have assembled my first DIY lithium 12v battery with 4 3.2V 120ah cells using xiaoxiang 4S 120A Li-ion BMS. I followed the overkill solar directions. I've top balanced successfully and then connected the BMS and final assembly. I have this issue - the cell voltage measures 13.6V at the cell terminals but through the BMS at the final terminals the voltage is 11.9V. The android BMS app confirms battery voltage is 13.6V. I've double checked the balance wires and overall assembly and can find nothing. What I'm I missing, what should I look for?

This morning I redid each crimped connector on the balance leads and the push connector is fully seated with no change to the low voltage issue.

A few photos of the project.

 

[rando]

Your BMS is probably off. When you first connect the cells, it doesn't know what the SOC is so it may assume it is too low and turn off. Configure it through the app, and then either force it on through the app, or charge the pack for a bit, which will turn it on. It will take a while to sync up the BMS.

PS Very nice job on your pack!

 

[ski3pin]

Your BMS is probably off. When you first connect the cells, it doesn't know what the SOC is so it may assume it is too low and turn off. Configure it through the app, and then either force it on through the app, or charge the pack for a bit, which will turn it on. It will take a while to sync up the BMS.

PS Very nice job on your pack!

Thanks Rando! I put a charge on the battery last evening - 14.4V until the DC unit's amps were near .0 and then disconnected. I checked the battery this morning and the voltage is still low - the same as above - through the BMS.

When you say "a while" above, how long to sync up the BMS.

For anyone who enjoys data, here is what the BMS app is showing -

 

[rando]

That is a different interface than the one on my BMS, however everything looks to be in order and the battery and BMS seem to be in sync ie the battery is fully charged with a 13.6V resting voltage and the BMS thinks the battery is fully charged.

Silly question, but have you tried loading the battery? Apply a load to the output and see what the voltage is.

 

[ski3pin]

Not a silly question, Rando. I was at the point in the build process to do a capacity test of the battery - a la Will Prowse - when I discovered the discrepancy in voltage at the final terminals. I will hook it up today to see what happens.

Thanks for your time in looking this over. I appreciate it.