Hi Guys,
I have recently found out that my source for $70 70AH 2nd hand deep cycle batteries is not really as cheap as I thought! haha, I never like using the 2nd hand, but its what I can afford!
considering if I DIY Lithium Ion I might come close to the same price with respects to discharging my deep cycles to around 50%, captivity price wise would be similar and I would get 100% brand new!
I have read a few articles here and there and am a little scared with respects to charging them and how to go about it.. considering I am managing 2 strings of 6 ( 12 batteries with 2 lots of 6 batteries in Series for 24v...)
1 Deep cycle battery costs me $70 is's a 12v x 70A = 840Wh (40-50% (336-420 Watt Hours))
so speaking about capacity my banks total is
12 x 70A x 12v = 840Ah (approx 10 KwH)
with my level of discharge at 40-50% or so.. thats only 336-420Ah, (4-5 KwH) of usable power
so I have seen decent batteries for sale at 40 cells of 18650 for $60 + costs for circuits and holders etc
mathematically that is 4.2v * 3Ah * 40cells (504 Watt hours) vs the 336-420Watt Hours the deepcycle are doing
that would mean 40 cells x 10!! for my old capacity! 400 batteries! OMFG tho it's make expansions over time as building the batteries will take time haha
so you can see my excitement here with respects to high efficiency batteries, and using these cheap 18650 cells over brand new deep cycle batteries
we're talking $60 for 18650s vs $200 for new deep cycles,
with that out of the way comes the hard part.. how to I use the cells?
I would want 24v nominal! meaning 6 series cells 3.7-4.2 (22.2-25.2V)
I have seen a few battery protection circuits, and here is where I am really lost on connecting these!
this is a 15A 6cell circuit, I own one of this circuit already but have yet to use it..
**broken link removed**
now I have seen this following circuit which is way more exciting that it has a discharge terminal and separate charging terminal.. meaning possibly I can connect a few dc-dc converters to charge the strings independently?! tho I am unsure here, I would assume if I ran 4 of these protection boards, would I be able to have the outputs connected together?
this is a 50AMP output/ 15A Input circuit meaning I can make less battery packs if that makes sense
**broken link removed**
If I am thinking about this in the wrong way I hope to learn the right way, please make comments and advise for my possible new project!
Many Thanks
Shaun
EDIT: Sorry, I use the power for a small solar powered bungalow
I have recently found out that my source for $70 70AH 2nd hand deep cycle batteries is not really as cheap as I thought! haha, I never like using the 2nd hand, but its what I can afford!
considering if I DIY Lithium Ion I might come close to the same price with respects to discharging my deep cycles to around 50%, captivity price wise would be similar and I would get 100% brand new!
I have read a few articles here and there and am a little scared with respects to charging them and how to go about it.. considering I am managing 2 strings of 6 ( 12 batteries with 2 lots of 6 batteries in Series for 24v...)
1 Deep cycle battery costs me $70 is's a 12v x 70A = 840Wh (40-50% (336-420 Watt Hours))
so speaking about capacity my banks total is
12 x 70A x 12v = 840Ah (approx 10 KwH)
with my level of discharge at 40-50% or so.. thats only 336-420Ah, (4-5 KwH) of usable power
so I have seen decent batteries for sale at 40 cells of 18650 for $60 + costs for circuits and holders etc
mathematically that is 4.2v * 3Ah * 40cells (504 Watt hours) vs the 336-420Watt Hours the deepcycle are doing
that would mean 40 cells x 10!! for my old capacity! 400 batteries! OMFG tho it's make expansions over time as building the batteries will take time haha
so you can see my excitement here with respects to high efficiency batteries, and using these cheap 18650 cells over brand new deep cycle batteries
we're talking $60 for 18650s vs $200 for new deep cycles,
with that out of the way comes the hard part.. how to I use the cells?
I would want 24v nominal! meaning 6 series cells 3.7-4.2 (22.2-25.2V)
I have seen a few battery protection circuits, and here is where I am really lost on connecting these!
this is a 15A 6cell circuit, I own one of this circuit already but have yet to use it..
**broken link removed**
now I have seen this following circuit which is way more exciting that it has a discharge terminal and separate charging terminal.. meaning possibly I can connect a few dc-dc converters to charge the strings independently?! tho I am unsure here, I would assume if I ran 4 of these protection boards, would I be able to have the outputs connected together?
this is a 50AMP output/ 15A Input circuit meaning I can make less battery packs if that makes sense
**broken link removed**
If I am thinking about this in the wrong way I hope to learn the right way, please make comments and advise for my possible new project!
Many Thanks
Shaun
EDIT: Sorry, I use the power for a small solar powered bungalow