Series/Parallel BMS issues

[Randal Barrett]

Most lithium batteries cannot be used on most off grid systems because their built in BMS will damage their own batteries with series/parallel configurations. BattleBorn and a few others can be series/parallel with some having limits on number of paralles banks. BattleBorn says unlimited.

Some are still stating that lithium have a 80% to 90% percent draw down limit. This may be true on build your own prismatic or poorly designed lithium batteries with built in BMS, But is not true with BattleBorn and other well designed batteries! You get 100% of stated amp hours with BattleBorn! It will not hurt the battery to go to shut off voltage of 10v! When building your own prismatic batteries and adding your own BMS, yes you will lose some of the stated amp hours.

 

[b.james]

Keep in mind the cycle figures offered are from the manufacturers. Personally I don't know of anyone who can say they have been using the same LFP battery for any more than 4 years . One who claimed 7 years turned out to have blown them up and replaced them after about 4 years . So we just don't know as yet.

I would be interested to hear from anyone who has had them continually in use for longer than 4 years , not sitting idle for great periods of course.

 

[Randal Barrett]

BattleBorn has done extensive testing along with some other reputable companies. I trust BattleBorn. 10 year warantee, 8 year full replacement. They have been in business long enough to know and their batteries are actually lasting longer than stated. Just imagine having 80% to 95% of original usable amps after 10 years depending on usage of course. Most systems do not draw down batteries fully each day.

 

[b.james]

Hey?

their batteries are actually lasting longer than stated

Can you explain how that is? Where you get that from?I have not seen anything going back much past 4 years? and would be very interested to see that.
Its easy here to just say stuff but can you back it up?

 

[svetz]

Can you explain how [batteries last longer than stated] ? Where you get that from?I have not seen anything going back much past 4 years?

In the Battle Born warranty they guarantee to be X% after Y years/cycles, similar to solar panel warranties. But at the end of that time they should still work, just not have the capacity they did - same as solar panels. Most manufacturers datasheets only show life to 80% and they look something like this:

You can see from the curve the inflection change around 3200... the degradation starts to increase; but it's not magically going to stop at 80%. A lot of it has to do with how batteries degrade. Lead Acid for example degrades through sulphation and material "shedding" off the plates. At 80% it's ready to nose-dive shortly thereafter.

Battle Born and other companies use accelerated testing and understand the characteristics of the LiFePO4 chemistry; so the data doesn't have to go back to far to get a good feel for real world conditions.

The whole "2nd life battery" community is based on the lithium not nose-diving; and there's an availability of them as most companies recycle them after 80%. While there's potential that those batteries have a lot of miles left them, there's also risk as some may have been hard used. The 2nd life community is pretty careful about testing and ensuring every cell is properly fused to avoid mishap.

You can find things like this reference from the internet: and numerous real world accounts of 1000s of cycles beyond the 80% mark.

But take the overly optimistic graphics like the one above with a grain of salt. For every battery that makes it to 10,000 cycles, there are a hundred that didn't. Mostly is has to do with the C-Rate they were used at.

Hope that helps!