Bounder price for their lithium battery!

[fishinjunky]

I got a quote from Bounder for their 100ah lithium battery. They want 4200$ for a 100ah lithium battery

Bm how many 230ah lithium batteries could you build for 4200$ ?

I just don't understand where the huge expense is for Bounder to justify a 4200$ price tag for 100ah lithium

[emilevirus]

I just built mine 230Ah for $500.
Also, 100Ah just isn't enough for a Bounder. Unless they use higher C cells?

[Burgerman]

Its about 350 uk pounds for high quality 230Ah cells. That are actually 244Ah. So thats, £1.40 per Ah. So 100Ah is £140.

So just divide your 4200 dollars by £140.

Currently £140 is 176.4 dollars.

So... 4200 divided by 176.4 is exactly 27.9 100Ah lithium batteries.

But you need to add the cost of a good BMS to the battery as well. So add 40 dollars?

So thats 176 dollars for the battery and 3800 dollars for the bloke who assembles it...

[emilevirus]

But I really wonder how they can get away with 100Ah. Before receiving my 230ah cells, I put 100Ah battery in my bounder to try it out. It wasn't enough. Voltage was sagging. It's enough for my other chair because it pulls 10A avg and 50A max. A Bounder pulls 30A avg and 100+A peak. A 100Ah can't handle that UNLESS they use lower resistance cells.

[Burgerman]

I just built mine 230Ah for $500.
Also, 100Ah just isn't enough for a Bounder. Unless they use higher C cells?

Expressos Bounder 100Ah with its bms etc was showing its age after the 2nd years summer at around 80Ah left in it. Because using it like a phone battery with high discharge levels and charging at 3.65V and worse per cell, plus high intermittent c rates spikes on discharge (steps, curbs, turn in place, ramps etc) kills them as fast as lead. Done properly, with 230Ah expect 20 years plus.

[emilevirus]

Also when I received my Bounder, Linx was set to cut power to half at 25.2v and shutdown at 24.5v. If they set it that way I suppose they use high discharge rate cells? My 100Ah Amazon battery was fully charged and it was triggering that warning instantly.

[Burgerman]

Yes but "amazon battery" is the warning sign...

Heres the problem. Theres no actual definitions or tech spec for C rate. In china every cell is rated way above what makes sense. They sell them like cameras and megapixels or chinese torches with rediculous quoted lumens, or 10,000000 volt stun guns. All of these try to outdo each other.

Its like this.

Theres battery impedance. That determines the volt drop under load. And the lifespan of the battery. Theres no point where it is 0.5C 1C or 2C or 10C or 30C etc. Theres a slope. This slope just means that the higher the discharge or charge rate is the shorter the lifespan.
The same applies to charge voltage, and to discharge voltage.

So to kill a lithium fast use a too small pack. So you already get most of the following without even trying! And eat up the charge cycles fast too. Charge to 3.7V. Discharge to 2.5V. USE 100% of its capacity like a phone. Charge and discharge at high rates. And store it empty or full. And leave it someplace warm. You might get a week or a year depending on the exact combination and battery quality and initial impedance.


Or do the opposite. Use the CENTRE 70% as much as possible. Use a LARGE battery. So that you can charge it less often. And use up less cycles. When you do charge full, maybe every 10 cycles, keep below 3.6V say 3.55V and do NOT keep it sat at that voltage while a weedy balancer tries to balance it for hours. Use something with a rapid balancer like a hobby charger. Dont use the last 20% on discharge. A large battery already means low C rate discharge... Dont store full! Keep it away from heat. It will still be as good as new in 20 years time. Provided it was decent quality to begin with. EV or A+ genuine cells like the 230Ah ones we are currently using for less than the price of lead.

Any combination of this will all work. How long a battery lasts depends on all of this. But the differences are not minor! A year? Or several decades. Lithium just wants to sit unused at half charge. But we need to use it. C rate exists. Because of impedance. Dont look at advertiser simple figures.

Look at test data.

Mine EXACTLY match the cell number code. And manufacturer test data for my actual cells.
Resistance is all important, and capacity measured on PL8 was within better than 1% of the claimed 244Ah capacity on the 4 cells I bothered to measure.

It doesent matter if they claim .5C 1C or 3C just look at impedance per Ah. 0.22of a mOhm here. Its the only way we can compare. @ half charge.
So under 2mOhm for a full battery.
Compare to a SET of MK gel 74Ah at 8 to 9mOhm only when fully charged.

[emilevirus]

Yes I get that but it all depends what cell they use. Docan sells 3C 100ah cells with an impedance of under 0.2mOhm. So technically as good as our 230Ah, no?

[Burgerman]

For current. Quality? Maybe. But we are using impedance to determine current capability. As a proxy. But theres really a bit more to it. Its usually safer to go big! Especially as high C rate cells only help in one of the reasons that cells die. Because If its smaller Ah you are then discharging deeper for every trip. And charging more frequently. So doing 2 other things that kill them off faster.

[emilevirus]

You can't fit 230Ah in a drop in replacement though. So then what? Most people won't DIY a battery pack. I actually had quite a few people ask me. If you're a heavy user, your lead bricks last 6-12 month. Is it ok to recommend them a drop in replacement? They're cheaper than lead anyway so I think so. Only must is to get one with a programmable BMS to remove all protections and while we're at it, decrease UVP to 3.58v. On mine it was set to 3.75v stock!

[Burgerman]

I know all this thats why for years I tell people that drop in replacements are or can be very unreliable for a bunch of reasons and problematic in various ways and can leave you stranded too. And they dont last as they are overworked for lithium. Lead is robust. Lithium isnt.
And why I always say that if you understand enough to use a drop in successfully, then you might just as well do it properly anyway. And get 20 year or more battery service, 5x the range, for half the price of lead.

Fitting a drop in replacement throws away most of the massive gains in longevity, range, etc. In many cases adds unpredictability and potential not getting home ssues...

>>>Most people won't DIY a battery pack.

Well frankly thats teir problem. I want to be a millionair. But sometimes you have to put a bit of time or learning or work in if you want the same results out as you now get. And reliably. Knowledge is power. Most of this planet do not want to learn. Cant be bothered. But thre are some things you cant just buy. Well you CAN like bounders crappy 4200 dollar 100Ah lithium...

To be at the cutting edge in a wheelchair sadly requires a little effort. Theres not a single lithium drop in that I consider worth the effort. You may gain a little bit more range, at the cost of reliability. Unlike lead they dont degrade gradually. They fail while you are out for many reasons. My drill just did it. My auto mower did it 3 times. I have a dell laptop battery here that shows 100% full. Wont run the laptop. It died in the pub with a full battery. Its why I dont much like BMS.

[martin007]

So then what?

There are only two options.
1- Reflect, fight, and move forward.
2- Garlic and water.

I have been fighting for 43 years; I was born sick.
Everything has a solution, except death.