Best non-lithium battery technology

Hi Instructables community! I am looking for any insight / suggestions regarding what battery technology (non-lithium) that offers the best specific energy (MJ/Kg), preferably rechargeable and reliable. My research led me to looking to consider rechargeable alkaline batteries, given data on wikipedia (the BEST source ;)  ) but are these even manufactured? I cannot find any place to buy them.

BACKGROUND:
I am in need of this for the design for the solar car team at UVa, as the BMS (Battery Managment System) mandates a backup battery that is separate and any lithium technology is not allowed.

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Yonatan249 months ago

Why not Lithium? Not even LiFePO 4?

-max- (author)  Yonatan249 months ago
IDK. My guess is for safety.
Yonatan24 -max-9 months ago

I believe LiFePO 4 is puncture, fire, and overvoltage, undervoltage safe. I'm not 100% sure, but you should ask...

-max- (author)  Yonatan249 months ago

WHile looking at the regulations, I just noticed that primary lithium cells are not explicitly prohibited. In says you can't use any lithium based secondary cells.

So I think that is going to be the best choice moving forward.

If you can use lithium cells for the primary than there is little to worry anyway.
I checked some of these battery packs for the E-bikes and some come in 48V and offer 20 or more AH at a weight that seems to be total joke compared to normal battery types.
Even a decen laptop battery can have more weight than those.
Downside is a quite hefty price tag on them, about twice compared to standard Li-Ion packs of same voltage and AH rating.

As for the backup:
I have my 4WD fully set up with all the things I need and don't really need, including a dual battery system.
Last year I replaced the secondary battery with a deep cycle type of modern design and I don't regret it a single bit.
Compare what you need in AH and how much weight you would get with stadrady technology like SLA batteries.
Than have a look at the new deep cacly 4WD batteries for coamparison of weight and AH rating - you might be surprised that you can get more power and less weight with these new ones :)
The cells are not made with plates in the traditional way but instead as rolls with a thin fabric seperator.
They have less weight and far longer run times with a wider discharge rate than normal deep cycle batteries.
Cranking power is bad though but if you don't need more than 20A they will be more than good enough.

As a last resort you can try the cheating way as they did here last year.
One team found a loophole in the rules and regulations noticing that fuel cells are not mentioned anywhere at all.
So as their backup for cloudy periods and to boost the small main battery they used a fuel cell running on a bottle of hydrogen and oxygen.
They borrowed the cylinders for the race from a company specialised in high pressure containers made from carbon fibre.
Both bottles together were under 2kg empty - that is including the valve and all....

-max- (author)  Downunder35m9 months ago

Not sure if SLA will be the way to go, do you have ones that can exceed 200 WH/Kg? If so then I am damn impressed!

Forgot to mention:
Rechargable alkaline batteries are just normal alkaline batteries.
It is the charger that gives them a new life, I have one that recharges standard alkaline batteries and it works fine although you never get the full capacity back and with ever recharge it gets a bit lower.

Interesting, reminds me of the problem I had with my portable radio:

Alkalines - No. They pollute and are expensive.

Regular rechargeables - No. 1.2V Is too low.

Nickel zinc rechageables something like that - 1.6V, maybe too high, will probably stay at 1.8V when fully charged, so they might ruin it. (Also expensive on eBay)

Solution: ask your grandpa if he has another radio ;)

Well, last time I checked Lead Acid batteries are around 40Wh/kg.
NiCd batteries slightly below the Lead Acids.
Li/Ion batteries bring around 130Wh/kg.
So with Li/Ion out of the race for the backup, what are YOU thinking of that would not cost an arm and a leg?
But if money is no problem you might want to check Lithium Thionyl Chloride batteries.

petercd9 months ago

Whats wrong with Ni-Mh?

What voltage and capacity do you need?

+1

2+
NiMh are the next best thing.
They are a bit fuzzy and want to be properly charged and dis-charged only to a certain level but that's a job for the controller.
Size is good too with many available option so placement of the packs should be easy too.

When they have these solar races here I sometimes take a sneak peak in the newpapers to check some pics of the winners.
Years ago someone made it into the finals running on battery packs for cordless drills.....

-max- (author)  Downunder35m9 months ago

A pathetic 0.155 MJ/Kg for the high capacity 2800mAH ones? Is this really the best that technology has to offer!? Wikipedia specifies alkaline rechargeable batteries as having 0.5MJ/Kg.

My pizza has 2 orders of magnitude more energy compared to NiMh!!!! :P

You're only running a data backup battery !

-max- (author)  steveastrouk9 months ago

It also required to power the BMS for 5 hours, as well as driver and battery bank cooling fans. NiMh from my understanding are pretty inefficient with charging as well, something I forgot to consider.

Put some proper numbers on the parameters, and see what's sensible.

If the vehicle weighed a tonne, then a 1kg SLA isn't going to be a big problem for example.

If you consider MJ/L then SLA is also a good choice.

-max- (author)  steveastrouk9 months ago

We are allowed a limited amount of weight for the main battery bank, but I see no mention of the limit of the size of the supplementary battery ;) There are restrictions as to what it can power, however. Regulations do permit primary cells to be used, of which are allowed to be replaced.

MJ/L is basically of non-importance.

So how many Ah do you NEED ?

-max- (author)  steveastrouk9 months ago

All of them XD

IDK yet, I am just googling around to figure out what the best thing is. If there really is nothing better than NiMh, then fine. I just hate those ones.

I did find a few things regarding "potassium ion" and "sodium ion" batteries, but I guess they are a bit experimental still.

Better might mean "affordable", and SLA would work very well for that. Does this backup battery have to be permanently carried ?

-max- (author)  steveastrouk9 months ago

Given that the team spent $14,000 for a motor, I don't think cost is that much of an issue.

Until you put some proper capacity parameters on it, your just guessing. If the MAIN backup battery was a car battery, you could use alkalines to hold the electronics up while you change to the backup.

-max- (author)  steveastrouk9 months ago

And a strobe light in the case of a fault condition.