[Benny Jahmin]

I have tested my home made 105ah lifepo4 battery to around 200amps with no issues. They are rated to 3c for short bursts.

What did it cost you to build?

 

[JFF45]

What did it cost you to build?

I was thinking that home made lithium batteries would make a good interesting thread on its own.

 

[Benny Jahmin]

I was thinking that home made lithium batteries would make a good interesting thread on its own.

Yeah I have been meaning to look into the topic a bit more. There is plenty on YouTube.

 

[Bond]

What did it cost you to build?

105ah Eve cells (brand new, not 2nd hand) =$86 each x 4 = $344
100 amp BMS = $110
Active cell balancer =$35
Battery box = $60
Cables and lugs = $10
Total = $559

280ah Eve cells $212.5 each = $850
200ah BMS with bluetooth = $140 or a locally sourced 350amp bms no bluetooth $180
Cell balancer $35
Battery box = $75
Cables and lugs = $15
Total for 280ah battery (22kg) = $1,115

 

[JFF45]

Just curious, what’s the weight of the 105ah?

 

[Bond]

Just curious, what’s the weight of the 105ah?

I think around 10kg.

 

[rgren2]

Where are the bits purchased from, I did a google search and there were lots to choose from?Be a bummer to buy ordinary bits.

 

[Bond]

Where are the bits purchased from, I did a google search and there were lots to choose from? Be a bummer to buy ordinary bits.

Cells are from a specific seller on Alibaba. She is the only one i have found to not have anything negative said about the quality.
Case is from a guy in Melbourne. His FB group FPV-POWER. Super Capacitor & Lithium Battery Supply to Australia. | Facebook
BMS is from here 3-4S - Shop Cheap 3-4S from China 3-4S Suppliers at JIABAIDA Official Store on Aliexpress.com But there are plenty to chose from.
Odds and ends are Jaycar and i have 3d printed a few small things like busbar guards etc.

A lot of info gained from here https://diysolarforum.com/

I have 4 x 280ah EVE cells new i their box if people don't want to wait for shipping.

 

[Benny Jahmin]

the twin 75s give me 130ish AH of deep cycling and 20ish AH reserved for cranking, the marine was like 60AH usable for deep cycling.

Do you have these isolated at all or just know from experience you will never use more than 130ah before needing to start the car again?
And what charger are you using?

 

[JFF45]

I’m trying to decide if it’s worth the risk buying a built unit from AliExpress. I’ve seen 280ah units for sub $1k.
Seller has good reviews, wide range of options and honest delivery time of early August.

 

[Bond]

I’m trying to decide if it’s worth the risk buying a built unit from AliExpress. I’ve seen 280ah units for sub $1k.
Seller has good reviews, wide range of options and honest delivery time of early August.

If its under $1000 then they HAVE to be used cells. Brand new A grade matched and batched cells are now around $250 each. Unmatched but still good quality can be had for around $210 plus postage.

 

[JFF45]

If its under $1000 then they HAVE to be used cells. Brand new A grade matched and batched cells are now around $250 each. Unmatched but still good quality can be had for around $210 plus postage.

They claim A grade cells. They have a wide range with 12v, 24v and 48v units.
I know everyone agrees that it can be hit & miss with AliExpress. This company does seem to get some good reviews.

 

[mikecooper422]

Do you have these isolated at all or just know from experience you will never use more than 130ah before needing to start the car again?
And what charger are you using?

Charges straight off the alternator and solar regs,

Load disconnect turns aux loads of at a voltage point which roughly indicates 20ah remaining

If you ever see the fridge go out, it's time to start the car or put the car on charge but that is rare given I have a fair bit of solar.

 

[Bond]

They claim A grade cells. They have a wide range with 12v, 24v and 48v units.
I know everyone agrees that it can be hit & miss with AliExpress. This company does seem to get some good reviews.


View attachment 542476

Everyone in china claims grade A but not many are. But they are probably still reasonable value. I wonder what size BMS.

 

[mikecooper422]

Ampacity is a silly american word that describes the current carrying capacity of a cable. Has nothing to do with the amp hour rating of a battery.
Your DCS battery is made in China and also has a ling long BMS inside it. The only aussie made lithium is dug out of our ground and sent to China for processing.
Personally I will keep my LiFePo4 batterys in boxes and not under the bonnet, use them to run fridges and lighting, which they are very good at, hook them up to solar blankets or dc dc chargers, and rely on the trusty Optima which will last for 10 years to do the cranking.

Ampacity to me means amp hours

CCA or current carrying capacity to me represents how much a conductor can carry.

This is what I know from being an electrician.

Almost everything is made in China, doesn't mean the Chinese aren't capable of making decent quality when asked to do so.

I believe the main things with the cells was the grade, A grade cells were a much better design then B grade which are found in lots of cheapies, from memory the A grades have some fail safes built in also in regards to fire/explosiin hazards.

 

[Bond]

Ampacity to me means amp hours

CCA or current carrying capacity to me represents how much a conductor can carry.

This is what I know from being an electrician.

Almost everything is made in China, doesn't mean the Chinese aren't capable of making decent quality when asked to do so.

I believe the main things with the cells was the grade, A grade cells were a much better design then B grade which are found in lots of cheapies, from memory the A grades have some fail safes built in also in regards to fire/explosiin hazards.

Grade A is a new cell that meets the specifications after testing and also had no physical damage. After that they can grade them however they like with B usually having some damage, not meeting amp hour rating, some physical damage and or being second hand. A lot of Lifepo4 cells come out of chinese EV's

 

[mikecooper422]

Grade A is a new cell that meets the specifications after testing and also had no physical damage. After that they can grade them however they like with B usually having some damage, not meeting amp hour rating, some physical damage and or being second hand. A lot of Lifepo4 cells come out of chinese EV's

Fair enough.

What was it about the design of the cells with the inbuilt pressure relief valve that I am thinking of and associating with grade A cells?

 

[Bond]

Fair enough.

What was it about the design of the cells with the inbuilt pressure relief valve that I am thinking of and associating with grade A cells?

Even the cheapies have pressure relief valves. They are pretty stuffed long before they are used and you can still get thermal runaway with them. Still a lot safer than Lithium Ion.

 

[mikecooper422]

Full trust in these old DCS units even after years of cape York corrugations and heat.

Only had the BMS turn off once when I parked it in the garage, left the fridge on and didn't plug it in to charge.

Once plugged into charge the BMS woke up again.

With either/any chemistry I think one of those capacitor type jump starter bricks would be a great backup for being remote.

Also to add that if I had pushed the car back out into the sun, the solar regs would have woke the BMS up and started charging it as well.

 

[Bond]

View attachment 542581

Full trust in these old DCS units even after years of cape York corrugations and heat.

Only had the BMS turn off once when I parked it in the garage, left the fridge on and didn't plug it in to charge.

Once plugged into charge the BMS woke up again.

With either/any chemistry I think one of those capacitor type jump starter bricks would be a great backup for being remote.

Also to add that if I had pushed the car back out into the sun, the solar regs would have woke the BMS up and started charging it as well.

Sounds great.

It just shows that the chemistry works well and with normal use should get a very long life. It would be interesting to see what they look like on the inside. With my pack i have lined the bottom with a foam mat and also placed 1mm clear plastic in between each cell and on the walls for some protection. Once in the case i have added a bit more foam to stop movement.