Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Looking for the 'best' cell for a project.
#11
Alright after playing around with some numbers here is the conclusion that I come up with.

Note: This is strictly my opinion and by no means a firm conclusion. Others may chime in and make better recommendations and or come to a differnt conclusion.
 
Samsung INR18650- 30Q 18650 3000mAh 15A Battery
 
Here is the scenario.
 
 
If you use the full 51 Amps this pack can supply you an hour of power (lol kind of rhymes) less inverter and cable losses.
Obviously half of that 25.5 Amps you have 2 hrs.
Max charging is 4A X 17 = 68A for ≈ 70 min.
Has a whopping max continues discharge of 255A (Cabeling at that rate would be huge 1/0 anyway) in a 17p config.
Spec sheet of the INR18650-30Q
 
 
But all of that is just math.
You can plug in a INR18650-35E (3350mAh) with similar specs and get obviously more Ah which may compensate for your Inverter and cable losses giving you the true 1.5kWh you are looking for.  Although the recharge is not as fast. 4 hrs.
This cell can do spurts of 221A and 136A continues in a 17p config
 
 
Spec sheet of the INR18650-35E
 


Wolf
For Info Google Drive

Great ABB shunt breaker seller River City Industrial
Great prices and superb service.
 [Image: em2566%20(1)__19172.1521541365.jpg?c=2]

Not your average Wolf       
            Cool
Reply
#12
Wolf - thanks so much for taking the time to look into this for me.

I should have mentioned I am not tied to the parallel number of cells or physical size (so long as it doesn't get much bigger).

So with your suggestion I could simply do a 7s20p setup to reach 1.5kw, also raising the spread of the discharge and charge - it's actually a benefit of lower mAh cells I hadn't considered before now - with the 30Q it would actually keep my 30A charge current at the exact 'standard' spec.
The 30Q is bizarre in having a 600mA 'standard' discharge but a 14a max Huh (edit: I now realise 600mA is quite common discharge rate, even when the max is very high) . The cycle life is also measured at the max discharge of 14A, so one would assume the cycle life would be substantially better at 4-5A... but then why does the 35E have such a poor life cycle when discharged at 3.4A when I am guessing it is the same chemistry?

It's one of the things that attracted me to the Sanyo, it has a reasonable 'standard' discharge of 2A and a high max of 14A. It has no listed 'max' charge in the database, but the spec sheet graphs (including life cycle) they are charging at 1.65A - so pushing 30A to a 7s17p pack would only just be over this, and a 7s20p set up would allow for a 30A charge. In addition their cycle life testing it around this charge rate and at 6A discharge and has the battery at around 2200mah (66%) after 500 cycles (6A discharge, 1.65A charge)- to the Samsungs 60% at 250 cycles (admittedly at over double the discharge for the 30Q, but the 35E hits 60% after 250 cycles at 3.4A discharge)

Given the rapid discharge, the 30Q seems to, at a somewhat informed guess, at least compare to the Sanyo, you can imagine if you discharged it at 6A it might degrade at a similar rate. But the 35E really throws me for a loop, same company, i guess the same chemistry, a few more mA but with a really very poor cycle life at low charge and pretty low discharge. As there is no concrete info on the cycle life of the 30Q at lower discharge rates this makes me worry it would be just a bad as the 35E for cycle life. 

This is hurting my head  Big Grin 

This has made me properly look at the charge rate of the Sanyo however, I think I just didn't check it properly before. I'm really not averse to a 7s19/20p set up, it gets me more kWh (I can therefore downrate to 1.5kWh for further cycle life benefits) and means I'm within the data sheet charge and discharge specs.
Reply
#13
I am today changing my thinking a bit and now thinking I might go to a 48v system. This should allow me to still feed an inverter, but by reducing it to 29.7Ah I still get the 1.5kWh I was aiming for and I can charge it via a DC-DC buck (this one, over provisioned, capable of 96V20A CCCV).

This was driven by the fact that I realised at the lower voltage range of the batteries I would be sub 20v in a 7s setup. I have one pice of equipment that is 20v9a that I really want to be able to run, and I run it even when I am not running other high power gear, so it was either require an inverter for this item or go up to 48v.

I cant just add go 8s because my voltage range would then be outside that of most inverter input ranges, so it would either be another DCDC converter which I want to avoid, or go up to 48v.


I'm pretty close to having the plan in place now. Next step is putting together the whole thing for review in CAD.
Reply
#14
A quick bit of CAD I did today, helps me plan everything out and check that it's all set up correctly.

This is 8S14P now 14S9P

[Image: xad3D8k.jpg?1]
Reply
#15
14s8p? although The render shows 14s9p

later floyd
Reply
#16
(06-12-2020, 07:35 PM)floydR Wrote: 14s8p? although The render shows 14s9p

later floyd

Upside down and back to front, and then missing a number!

14S9P is what I meant.
Reply
#17
I thought so Smile
latter floyd
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)