Learn from A to Z diy battery construction

[bds70]

So I got some great information from one of my other questions. It led me to realise I need more information.
So is there a resource that takes a beginner from purchasing cells, to testing equipment required, to software to test, to understanding the whole testing procedure and what terminology is used and what it means etc.

I want to build a whole new set of batteries. I am constrained to 12v by equipment I already have. I have 2 sets of panels each feeding to their own MPPT. I have a 400amp fuse between battery positive and lynxx Distributor the right size mega fuses for both mppt's and 2 inverters. Each inverter is Victron 3000/12/120-50.

Currently I have 2 working 340ah lifepo4 batteries and one dead one. After lots of talk with the supplier I am hopeful of getting a full refund on that battery. This would give me the funds to make my own units.

I am looking at 280ah raw cells from Jenny Wu Docan which I am led to believe is a good supplier.

So if there is such a resource please can I be pointed to the right areas.

Cheers

 

[rodrick]

Watch all of Will Prowse‘s and Andy’s off grid garage videos on battery construction and testing and you should know what to do and if you get stuck on something rewatch the video or post here and there many here willing to help you out. The main thing is take your time and double check your work and a good dmm is invaluable

 

[bds70]

Watch all of Will Prowse‘s and Andy’s off grid garage videos on battery construction and testing and you should know what to do and if you get stuck on something rewatch the video or post here and there many here willing to help you out. The main thing is take your time and double check your work and a good dmm is invaluable

dmm?

 

[bds70]

I have spent the whole day watching vids and reading. I think my brain is on overload.
But.... Can anyone help me on this one.
2 x Victron smart solar MPPT 1 - 150/85 12v
2 - 150/100 12 V
Both going to the lynxx distributor.
Battery bank is going to be 3 X 320ah in parallel.
Inverters X 2 both Victron 3000w/12v.

If both inverters are working at peak, pulling 6000w (or close to) how big should each BMS be in those batteries?

 

[42OhmsPA]

dmm?

Digital multimeter.

I have spent the whole day watching vids and reading. I think my brain is on overload.

I know that feeling, the more you read and watch the more sense it makes. It all starts to 'click' over time.

But.... Can anyone help me on this one.
2 x Victron smart solar MPPT 1 - 150/85 12v
2 - 150/100 12 V
Both going to the lynxx distributor.
Battery bank is going to be 3 X 320ah in parallel.
Inverters X 2 both Victron 3000w/12v.

If both inverters are working at peak, pulling 6000w (or close to) how big should each BMS be in those batteries?

If you plan to pull 6000w I would go to a 48v system, 24v at minimum.
Become best friends with Ohms law...

 

[Steve_S]

Battery Packs in Parallel Share/Divide both Load & Charge.
Packs in Parallel can operate independently of the others. Any single pack can continue to operate should the others cutoff for any reason.

Try to match BMS' to be able to handle the capacity of the specific battery pack when possible. Keep in mind that LFP can discharge @ 1C and take 0.5C Charge. A 280AH Battery can deliver 280A for 1 Hour from Full Charge and can accept 140A for 2 hours to charge from 0% SOC.
For a 280AH Battery Pack, I would suggest at minimum a 200A capable BMS and given that you are Victron Outfitted, I would ensure the BMS can connect via CANbus for full management & control. There are a few BMS' that can do this.

Here is a link to my Basic LFP guide I wrote up a couple of years back.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

Also, I suggest you download & keep these two graphics handy...

-----

 

[Skypower]

Definitely reconsider just upgrading to a 48 volt system. If you’re going to go anywhere near the a sustained peak of your 6000 watt 12 volt system you are going to be stressing every part of the it. If you are only going to be anticipating 6000 watts as absolute momentary peak or maximum surge than it might be acceptable. A 200 amp continuous rated bms (JK ?) will do that, but why push it. My rule of thumb is to halve the rating for continuous duty. They barely get warm. So three 200 amp bms are totally safe for 300 amps combined total. If you try to pull the full 6000 watt power, your 400 amp fuse will go poof. With full load and efficiency losses you will be looking at around 700 amps. Your cables will need to be BIG. For comparison a 6000 watt load on a 48 volt system would be only about 135 amps.

 

[bds70]

Digital multimeter.


I know that feeling, the more you read and watch the more sense it makes. It all starts to 'click' over time.

If you plan to pull 6000w I would go to a 48v system, 24v at minimum.
Become best friends with Ohms law...

I would like too, but having had the original fitout in my bus done by a company who decided 12v was the way to go, I am now sort of between a rock and a hard place. Too many 12v appliances to be able to financially change. Now I am more educated I know I was taken for a ride, in a way.

So unless I can drop a 48 or 24V output to 12v for those items I can't do it. What is really annoying is that apart from lights, roof extraction fans, water pump, macerating toilet, everything else is 240v, air conditioners, induction cooktop, fridges, hair dryers, front load washing machine & TV's .
Any suggestions gratefully received ?

 

[bds70]

Battery Packs in Parallel Share/Divide both Load & Charge.
Packs in Parallel can operate independently of the others. Any single pack can continue to operate should the others cutoff for any reason.

Try to match BMS' to be able to handle the capacity of the specific battery pack when possible. Keep in mind that LFP can discharge @ 1C and take 0.5C Charge. A 280AH Battery can deliver 280A for 1 Hour from Full Charge and can accept 140A for 2 hours to charge from 0% SOC.
For a 280AH Battery Pack, I would suggest at minimum a 200A capable BMS and given that you are Victron Outfitted, I would ensure the BMS can connect via CANbus for full management & control. There are a few BMS' that can do this.

Here is a link to my Basic LFP guide I wrote up a couple of years back.

Luyuan Tech Basic Lifepo4 Guide

This document was posted to the forum by Amy from Shenzhen Luyuan and written by Steve S. It was meant to be posted as a resource. Below is her description of the resource: Dear all friends in the forum, This file in the attachment was...

diysolarforum.com

Also, I suggest you download & keep these two graphics handy...

-----

Awesome, thank you. I have downloaded and off to study them. ?

 

[rodrick]

I would like too, but having had the original fitout in my bus done by a company who decided 12v was the way to go, I am now sort of between a rock and a hard place. Too many 12v appliances to be able to financially change. Now I am more educated I know I was taken for a ride, in a way.

So unless I can drop a 48 or 24V output to 12v for those items I can't do it. What is really annoying is that apart from lights, roof extraction fans, water pump, macerating toilet, everything else is 240v, air conditioners, induction cooktop, fridges, hair dryers, front load washing machine & TV's .
Any suggestions gratefully received ?

Check out the victron Orion products I have a couple of 24/12 70amp, in 48 volt 30 amp is max but these will give you different options

 

[Skypower]

I would like too, but having had the original fitout in my bus done by a company who decided 12v was the way to go, I am now sort of between a rock and a hard place. Too many 12v appliances to be able to financially change. Now I am more educated I know I was taken for a ride, in a way.

So unless I can drop a 48 or 24V output to 12v for those items I can't do it. What is really annoying is that apart from lights, roof extraction fans, water pump, macerating toilet, everything else is 240v, air conditioners, induction cooktop, fridges, hair dryers, front load washing machine & TV's .
Any suggestions gratefully received ?

Too easy!
The macerating toilet is the biggest 12 volt current draw. A high current 48 to 12 volt converter is too expensive, however a small charge converter to a small 12 volt battery would be much more efficient and easily power the “house” systems

 

[bds70]

Too easy!
The macerating toilet is the biggest 12 volt current draw. A high current 48 to 12 volt converter is too expensive, however a small charge converter to a small 12 volt battery would be much more efficient and easily power the “house” systems

Can you expand on the second part a bit more for me please.

 

[rodrick]

What he’s doing is taking a smaller dc converter and using it to keep a 12 volt battery charged and then you hook your 12 volt house equipment to the battery it will get recharged by the converter but the bigger loads are carried by the battery

 

[42OhmsPA]

I would like too, but having had the original fitout in my bus done by a company who decided 12v was the way to go, I am now sort of between a rock and a hard place. Too many 12v appliances to be able to financially change. Now I am more educated I know I was taken for a ride, in a way.

So unless I can drop a 48 or 24V output to 12v for those items I can't do it. What is really annoying is that apart from lights, roof extraction fans, water pump, macerating toilet, everything else is 240v, air conditioners, induction cooktop, fridges, hair dryers, front load washing machine & TV's .
Any suggestions gratefully received ?

Good advice from @rodrick ans @Skypower above.

I would also look into splitting the systems.

 

[OffGridForGood]

I agree with others, you should consider 48v system.
Look into selling the 12V equiment while it is still 'new'.
As a general rule, 12v up to 2kW, 24v up to 4kW, 48v above these. I feel if you upgrade now, rather than some day in the future, it will be less painful.

Currently I have 2 working 340ah lifepo4 batteries

If you parallel a battery with similar capacity, it is easier to keep all three in near balance. ie trying to parallel the 280 with the 340 may work but since you are planning a DIY pack, why not use 2s 170Ah cells = 340Ah. (or 2s 160 = 320, close enough).
Do you know what cells are in the two 'working 340Ah batteries'? If you match the same cells and Internal Resistance (IR) it will be easier to keep all three in near balance during use.
Building DIY packs is (in my experience) a lot of fun. Just how much money it saves is not as clear. Going with purpose built cases (like Seplos) makes it easy and a nice finished product, however the parts & tools may cost nearly the same as a finished pack. Do your own reseach to confirm.

 

[JJJJ]

Another possible option is to go with 24v. There are dc to dc converters which can take you to 12v. Wires will be smaller and less expensive than 12v. If you are DIY you can later switch to 48v with same wiring although would need to upgrade inverter charger and BMS. With changes in technology things should continue to improve and get less expensive

 

[Skypower]

We would split the system into several other systems for marine. A forward bank would handle the winch and bow thrusters and the rear would handle the stern thrusters. Each bank had its own charger(AC) and DC charge controller. This offered redundancy, no surges on the midship main bank and no need for long humongous cables.

 

[bds70]

Another possible option is to go with 24v. There are dc to dc converters which can take you to 12v. Wires will be smaller and less expensive than 12v. If you are DIY you can later switch to 48v with same wiring although would need to upgrade inverter charger and BMS. With changes in technology things should continue to improve and get less expensive

I think I am stuck. Apart from the 12v appliances I think I forgot to mention both the inverters are 12v. The mppt's are not a problem, they are software configurable, but to move to the better voltage I would have to sell both inverters and hope I got enough to buy maybe one new 48v one.

Problems problems. I will find a solution.

 

[rodrick]

I think I am stuck. Apart from the 12v appliances I think I forgot to mention both the inverters are 12v. The mppt's are not a problem, they are software configurable, but to move to the better voltage I would have to sell both inverters and hope I got enough to buy maybe one new 48v one.

Problems problems. I will find a solution.

Remember it’s a journey not a race keep researching stuff on the forum and asking questions you will get there it just takes time

 

[bds70]

Can you expand on the second part a bit more for me please.

Would this be the sort of suitable converter?

I agree with others, you should consider 48v system.
Look into selling the 12V equiment while it is still 'new'.
As a general rule, 12v up to 2kW, 24v up to 4kW, 48v above these. I feel if you upgrade now, rather than some day in the future, it will be less painful.


If you parallel a battery with similar capacity, it is easier to keep all three in near balance. ie trying to parallel the 280 with the 340 may work but since you are planning a DIY pack, why not use 2s 170Ah cells = 340Ah. (or 2s 160 = 320, close enough).
Do you know what cells are in the two 'working 340Ah batteries'? If you match the same cells and Internal Resistance (IR) it will be easier to keep all three in near balance during use.
Building DIY packs is (in my experience) a lot of fun. Just how much money it saves is not as clear. Going with purpose built cases (like Seplos) makes it easy and a nice finished product, however the parts & tools may cost nearly the same as a finished pack. Do your own reseach to confirm.

Due to the weight of 16s cells as one battery, it would be just about impossible for me (I am 70) to be able to get it into or out of the bus solar locker.

BUT, if I was to build either 4 12v units or 2 24v units then join them in series, apart from the extra cost of having multiple bms, would that be a feasible solution to getting 48V?