Batteries for Q500R

[Burgerman]

That 9 months was 28 years ago...
I knew why. I was selling deep cycle batteries for years!

So now I get 3 or 4 times than.
I fitted bigger ones. 34 to 24BCI group swap. That reduced the daily discharge level. And reduced the current per Ah.
I fitted an anderson connector, and charged with a power supply instead. So now correct CV voltage and a COMPLETE charge!
Then I charged around half way through the day at 30A via anderson for an hour as I checked mail etc. Before going out in an evening.

So now, bigger Ah, better charge method, intermittent daily boost at high current in the day, and the 9 months want to 3 or 4 years. Of course the manufacturers will wave their finger at you as you are not doing what they said...

[emilevirus]

That's a lot of hassle just to keep your batteries healthy... Most people will just discharge their batteries until there's one led, charge & repeat. After a 8h sleep, the crappy mobility charger isn't even done...

[shirley_hkg]

https://www.wheelchairdriver.com/board/ ... 4&start=90

Lithium is cheap enough to NOT cherish it. (⅓ of pair of SLA).

I have made my top condition SONY 180Ah pack redundant, simply because new cells are cheap.

Those drop-in will still outlast your 500R.

Battery is consumables, expendable too.



Adjustable PSU is better than charger in charging via BMS. It lets you set the desired voltage to top it up through passive balance. Charger may not restart if battery is nearly full.

[Burgerman]

That's a lot of hassle just to keep your batteries healthy... Most people will just discharge their batteries until there's one led, charge & repeat. After a 8h sleep, the crappy mobility charger isn't even done...

No but to keep users "happy" the mobility chargers SAY they are!
Lead, especially AGMs are very sensitive to getting a very complete recharge. Gels less so, but it still makes them live longer.

Lithium lasts much longer than lead even if you dont get everything right. And CAN be charged super fast too. I charge hobby batteries at up to 8C if in a hurry. And discharge them full to empty in a 6 minute heli flight. Those batteries are 100C claimed. Those last around 30 flights before they swell and look dangerous.
I put one in my auto mower, same battery, and it worked for 18 months charge and cut twice a day. So charged and discharged twice a day. So 1000 cycles before the BMS screwed up and allowed 1 cell to get way too low and it started cutting out all the time after a few yards.

Lithium lifespan in thse two scenarios was wildly different. Both cases were charged and discharged well within the battery spec. 30 or 1000 cycles plus?

Lithium is very sensitive to being warm. To being full. To high charge voltages. To load (the biggest factor), to being stored full. To charge rates (that one doesent bother us) and to discharge level. MUCH more so than lead. And much more so than people recognise.

Lithium LOVES being cool. LOVES being between 30 and 80% full. Loves ently low discharge rates that are nowhere near the max allowed 1C rates. Try to be 0.2C dischare and 0.1C charge. All of these things conspire to change lifespan hugely.

As shirly says though. Lithium has now become so cheap it doesent matter much. Apart from the hassle of building a fresh pack. And the sudden failure or cell murder of BMS affecting reliability.

So its all really up to you want you do. Anything works! Its all a matter of how well, and of reliability.

[Burgerman]

That's a lot of hassle just to keep your batteries healthy... Most people will just discharge their batteries until there's one led, charge & repeat. After a 8h sleep, the crappy mobility charger isn't even done...

Because they are ignorant. Theres hundreds of posts on here about batts dying fast...

And how is setting a charger such as the ZXD correctly once, for reglar charging overnight. And charging sat at a PC as you are sitting there anyway a lot of trouble? Once configured it takes seconds, and extends battery life by 2 or 3 times. Also means you have an almost full batt when you go out in an evening.

[Potty]

Thanks all for the replys about the batteries and chargers.

While I'm in the progress of finding used rnet parts, I thought I'll try and program the VR2 controller(the Q500 has even more of a hovercraft feel to it!), I've read how to make a lead, ordered a cable/resistor/diode/xlr plug and that should be ok for me to make(I'm sorry to read about the loss of Woodygb, He seemed like a top chap!), but cannot find a link to the VR2 programming software(I only found the rnet one), does anyone have the link please?

Thanks again

[emilevirus]

put one in my auto mower, same battery, and it worked for 18 months charge and cut twice a day

That's Lipo or Lion though. Lifepo4 gets even more cycles. Lipo is more sensible to abuse. If you dont store them at 3.8v they swell. A lifepo4 cares being at 100% but not as much.
A 100Ah cell is rated for 4000 cycles which is waay more than a chair can even handle.
I get about 80km range on a 100Ah battery so that's 320,000 km for 4000 cycles!

[Burgerman]

That's Lipo or Lion though. Lifepo4 gets even more cycles. Lipo is more sensible to abuse.

Do you mean sensitive?
No its not. Its actually the other way around.
The lower the C rate the easier it is to hurt the cells through all the things they dont like.
LiPo is best for high currents.
Lithium ion as laptop/phone/tesla etc are best for energy density.
LiFePO4 are the least energy dense and the best cycle life but they dont like all the same stuff...

If you dont store them at 3.8v they swell.

All lithium chemistries are hurt and try to swell more the greater the voltage and the higher the charge and discharge currents.

A lifepo4 cares being at 100% but not as much.

They have a greater cycle life, so it seems that way. But they swell exactly the same. But swelling is just the external look. The same chemical high degradation happens in cylindrical cells. And at high current use all the high cycle life quoted is while CLAMPED with high pressure between two metal plates. And at 0.2C discharge rates and at 0.1 charge rate. And at safe cool temperatures to 80% discharge.

A 100Ah cell is rated for 4000 cycles which is waay more than a chair can even handle.

A battery that has a 4000 claimed cycles will never get that unless:
Max 0.2C discharge (20A ON YOUR 100Ah batt)
Max 0.1A charge (10A on your bricks)
The cells are clamped together with a metal bracket with the correct tension. Without this you lose a lot of service life especially if you discharge at a rate 5x higher than the rated figure.
If the cells are not bounced up and down and held high while it balances...
And a few other reasons.

Tesla for e.g expect 5000 cycles from their cars pack. Because they rate the 135KWH battery as an 80kwh one. There electronics never allow your battery to charge to the 4.2V written on the Panasonic tesla 21700 cells. Likewise they never allow it to go below about 80% which reads as 0% in the car. And they use BIG packs with very low impedance, and water cool and heat the cells to protect them.


I get about 80km range on a 100Ah battery so that's 320,000 km for 4000 cycles!

[Burgerman]

tHATS Seems an awful lot from 100Ah. To do that you are at very least dischargging it way down below the 80% point and will get a quarter of the cycle life you would at expect at a safe 80% discharge. So that 4000 cycles is now about 1000. The 1000 will be reduced by your 29.2 volt charge and the BMS that takes a week to balance so the batt gets held high too long as well. So maybe 500 cycles.

Teslas 21700 cells get 5000 cycles in a car. But are rated at just 450 to 600 if all the capacity is used, 1200 cycles at 80% depending of the discharge rate. Which is why they dont...

Figures are guesswork but will be somewhere near if you do what you do.

[emilevirus]

So here's a study.... https://iopscience.iop.org/article/10.1 ... ab7900/pdf
If you cycle them very hard, 2.5v - 3.65v you still get more cycles than you could even use in a lifetime. The difference between that and 10% - 90% isn't even worth the hassle imo. Just cycle them and when they're dead just replace them! In 10 years we'll probably have a battery chimestry even better anyway.

[Burgerman]

Site wont let me in... But I have seen many studies. All of them contradict each other. I agree that it can happen hat they work well like that. But I have seen a lot of ruined and problematic packs too. I think that the quality of the cells is one of the biggest factors. The how shall we say, cheap supplies that we are able to buy as individuals, can be highly suspect. And theres rather a lot of low grade cells, made cheaply used in drop in bricks because $ is what its all about. The problem then is that they are hard to keep healthy with a typical BMS. Most of the testing you see is done with high grade cells that until recently were very hard to get at sensible prices. The ones coming from suppliers like Docan for e.g are way better quality, much lower impedance and stay balanced even if stored a year or so. But I also saw what happens when you take power too fast from A123 lifepof cells for e.g. They dont lose capacity much but they get high resistance and dont like powering anything. And those were top quality made in the USA originally. Although they are so cheap now that it doesent matter like it once did.

I got in, ste working. They are testing cylindrical high quality tiny cells. Thise are compressed to stop that expansion you get inside the casing. And are much higher C rate than what we use. Our cells are flat, layers that can gas and push apart. And swell. Even a few thousandts of an inch has a massive affect on internal resistance and is why all the rated figurs you see mandate a compressive force.

Let me find the specs for your 230Ah docan cells...

http://www.wheelchairdriver.com/doomed/EVE.pdf read carefully!
At 1C they MUST be clamped between 2 metal plates at the correct force or they go all bulged and knackered. We seldom reach 1C so it doesent matter much to us with 230Ah cells. But it really does when you put 100Ah 1C prismatics cells in a plastic box! I have seen this with my own eyes. This is one of the reasons that we fit 230Ah cells to begin with.

Its also why the old headway cells are fine at 80 or 100Ah. Those are 5C claimed, 10C pulse. Because they cant swell... Those make better addon packs. Or small packs.

*************


Under 300 kgf ±20 kgf initial compression force,
0.5 C / 0.5 C, 2.5 V ~ 3.65 V, Capacity retention≥
80%.

So usual charge and discharge testing was at HALF C and required manditory compression, to get 4000 cycles. And thats if you stop the charge at 0.05C at CV. On each cell. Or the 3.65V shortens lifespan. In a pack, while awaiting proper balance by a weak BMS or even a hobby charger so that never happens either! Thats an 11A cut off at CV. So this 4000 cycles is mythical in actual use. Thats why I charge at a kinder 3.55V as it takes a bit longer to balance and I aim for all balance done + 15 mins to equalise. Your (any) BMS doesent do that.