Unique Application

[Hedges]

We were using this battery connected in series to 24v and getting to 20+ mph https://www.vmaxtanks.com/V30-800-Deep-Cycle-High-performance-AGM-Battery-_p_46.html


Swapping out batteries or using capacitors are not permitted and all charging/running gear must be mounted on the kart as it runs. Panels and charging system.

OK, 2 of those batteries approaches allowed capacity.
It is meant for deep cycle cyclical use. You only care about a couple races. A battery optimized for automotive starting use, abused with near full discharge, may give better performance for your small number of races.

Seven of these in series for 84V, 700 Wh, 7 kW (under CCA conditions)?

ODS-AGM8E - ODYSSEY Battery

Powersport vehicles need a powerful battery that's built to take the constant pounding that comes with the territory, whether it's is on land, sea, or snow. The ODYSSEY battery can handle it. Featuring rugged construction and packed tightly with pure lead plates, the non-spillable AGM design...

www.odysseybattery.com

Power tool batteries, and batteries used for racing toys, may be more optimized for high current discharge rates than the other lithium batteries you see. Scooter batteries too, as someone mentioned. Known to catch fire, so provide some protection.

 

[florida cracker]

The LiFePO4 you linked to has 15 amps continuous capacity. I would expect the BMS to shut down if you try to run 100 amps continuous through it. Lead acid/AGM battery does not have a BMS.

Now I get to try to figure out how someone was running lifepo batteries and making it work last year, lol

OK, 2 of those batteries approaches allowed capacity.
It is meant for deep cycle cyclical use. You only care about a couple races. A battery optimized for automotive starting use, abused with near full discharge, may give better performance for your small number of races.

Seven of these in series for 84V, 700 Wh, 7 kW (under CCA conditions)?

ODS-AGM8E - ODYSSEY Battery

Powersport vehicles need a powerful battery that's built to take the constant pounding that comes with the territory, whether it's is on land, sea, or snow. The ODYSSEY battery can handle it. Featuring rugged construction and packed tightly with pure lead plates, the non-spillable AGM design...

www.odysseybattery.com

Power tool batteries, and batteries used for racing toys, may be more optimized for high current discharge rates than the other lithium batteries you see. Scooter batteries too, as someone mentioned. Known to catch fire, so provide some protection.

I do still have to charge these between heats with standard off the shelf Renogy Rover 60 SCC and the kids will literally be sitting next to the batteries.


I have learned through the past few days that y'all are a competitive bunch, lol

 

[Q-Dog]

Dakota Lithium claims some of their deep cycle Lithium batteries can also provide high starting amps. Maybe get in touch with them and see what they suggest?

 

[florida cracker]

Dakota Lithium claims some of their deep cycle Lithium batteries can also provide high starting amps. Maybe get in touch with them and see what they suggest?

Been online with them for a couple of days, they don't have anything this size that can do what I need

 

[Vigo]

The problem with Pre-built lithium batteries in the "36v but under 720wh" category is that everything will have far too small of a BMS to do 100a. Have you ever established what the actual current draw is during the race? It's possible the 100a condition basically doesn't exist outside of the first second launching from a dead stop. So you really have BMS problems here. I would guess that the rules do not distinguish between a battery and a cell, so you could probably just buy your own cells and use a large BMS to bypass this problem. They will look at the cells as '3v batteries' unless they really are 'smarter than that'? Can you clarify the rule on that?

 

[Quattrohead]

Discharge in series but charge them as 3 individual batteries, 1 charger per battery.

 

[Hedges]

He said he has to use a specific charger

Rover 60 Amp MPPT Solar Charge Controller

The Renogy 60A Wanderer MPPT Fee Controller is built with protection against reverse polarity, short-circuiting, getting too hot.

www.renogy.com

If 60A 48V is the max it does, use a 48V battery pack.
Do you have to carry that solar panel around on the top? Is it the only allowed charging source? Lose the weight if possible.

Bypass the BMS for discharge. Unless total Ah drawn exceeds capacity of cells and/or how much recharging, it isn't needed and just gets in the way.
Charging, you've got 20 minutes between runs, so no balancing is going to happen. Cell over-voltage is the only thing you need to consider.

 

[BuddyGMan]

720 Watts is perfectly 36 volts and 20 ahr.
This seems like e-bike batteries to me.
The issue is the BMS. Most are set to about 20 -30 amps continuous and 50 -70 amps peak.
So instead of buying a 20 ahr pack, buy multiple smaller ones to put in parallel.

This parallel idea might be even better on a 36 vdc power tool battery.
You want one built in 36 volts, so you don't have to worry about putting BMSes in series.
They are already made for highish current.
What if you take 5 4 ahr batteries (or some other combination of 20 ahr) and put them in parallel? (Other than the $500 to $1000 in batteries.)
The current out of each battery and connector is split, so no huge current from one battery.
The issue to work out is if the BMS is in the pack (IE protection from too low of a voltage) or not (no limit to the output current, but could damage the battery if discharged too far).

Charging becomes a custom solution with as much power as possible being put back in. (Can you AC charge?) Remember that most of these brands have 4C fast chargers, so the batteries can take thsi. You would just be building (really buying) your own.
Suggest one in this series, as it can be customized for voltages and profiles. Meanwell NPB

NPB-1700-MEAN WELL Switching Power Supply Manufacturer

MEAN WELL is one of the world's few standard power supply mainly professional manufacturers, covering 0.5 to 25,600W products are widely used in industrial control, medical and other fields, in line with international safety certification, short delivery of spot inventory.

www.meanwell.com

Battery adapters for power tools:

Collections

terrafirmatechnology

terrafirmatechnology.com

Thoughts on these ideas?

 

[justgary]

I have learned through the past few days that y'all are a competitive bunch, lol

You should see us with Cub Scout Pinewood Derby Cars!

All of these questions are coming at you because you started a second thread and not very many people bothered to follow the link to the other thread and read the background.

Again, I don't think series use of your batteries will matter at all. You aren't going to unbalance them in a few hours, and you can rebalance them in parallel after the race. Find something that can source the current you need and ignore the "no series" warning.

 

[ejfluhr]

The rules just say the battery must be sealed by the manufacturer. Why not use a quality li-nmc ebike 48v like this?

48V 14.5Ah Downtube Battery

48V 14.5 Ah Downtube Battery with NCR21700A Cells, 40A BMS, Reention Casing, ST3 Charge Port. UN38.3 Certified for Shipping, Individually Discharge Tested at Grin to Ensure Capacity.

ebikes.ca

40A BMS at 48v would be good for 1900+W of power. There is a 36v-19Ah battery also, but that could only get to 1400+W output. I actually run that battery on my own 500W ebike. If you need more power output, perhaps parallel 2 half capacity batteries...e.g. up to 3800W output.

I didn't see the rules require LiFePO4, but maybe I missed it?

 

[Invisibilianone6288]

In any kind of motorsport, the first thing you always do is look at the vehicles that are currently winning, and try to figure out why.

Second thing is read the rules very carefully, and unless it says a thing definitely cannot be done, and it seems like it may give you an advantage, test the idea out and see.

A silly example:
The rules might say it has to have four wheels. So you figure that four wheels in a diamond configuration might offer better aero.
Aero may be much more important than cornering speed, or maybe not.

If you win with something a bit odd, everyone will bitch and complain, but the rules did say four wheels, and if has four wheels, you just laugh !
Try to think outside of conventional solutions if you can.

Maybe one bright idea in twenty might work, but one radical idea might be enough, if its really good.

Sounds like you've heard of Smokey Yunick...?

 

[florida cracker]

To answer a few questions so far:

Lifepo batteries are not required, I wanted to try them to get the added available capacity if I was going to move up to 36v to the motor (3 batteries in series would have to be less ah available) and this seems to have opened up a can of worms as you can't find a 12v lifepo battery, they are all 12.8v and come with BMS that limits discharge amperage. May have to abandon this idea, will see precisely after we re-wire it to 36v using batteries we have on hand and see just how many amps it takes to run the speeds we want to run. And no, custom battery packs are not permitted and neither is swapping batteries between heats.

We are not limited to any specific charger but we do presently have the Renogy Rover and it seems to work well doing what we need it to do. We have 6 x 175 watt Renogy flexible panels powering this thing and they were putting out the amps just fine. All charging equipment has to be carried aboard kart.

Race consists of two heats starting at 30 minute intervals (run 3.76 miles first two heats) for fastest time and next two heats run 30 min as many laps as possible then sit for 30 minutes to charge for final 30 minute run.

power management is the key to doing well

 

[400bird]

Lifepo4 is safer, but your requirements sound like a perfect fit for "standard" lithium, such as NMC. Such as a bike battery. Outside of the news stories, these aren't unsafe. Think of how many power tool batteries are sitting around in garages, not on fire.

They are typically more power dense (both weight and volume) and support higher current draw and charging. If you are really pushing them to 300 amps and want to recharge in 20 minutes, you'll need to cool them, but a little muffin fan would probably suffice.

Oh, and you should look into tilting the entire cart to increase solar output, there is likely a noticeable improvement to be gained there depending on race time and your location. Between races, just park the cart 90° to the sun and pick up the side away from the sun and block it up. Even if it's "just for a tire rotation" or something. There's some easy charging capacity for you.

 

[ejfluhr]

I looked up the motor ME0909 specs, and it is rated for 12v-48v, up to 4800W. Since you have been running 24v SLA, you are only using max of 2400W continuous.
From my experience on ebikes, I doubt you are running 2400W all the time...the cart would reach unsafe speeds pretty quickly. It's would help to data-log the power draw, e.g. if the motor controller reports how much power it is applying, at min have the kids demo-run around and write down the min-mean-max of what they see.

I'm voting for 48v ebike batteries. Seems like they would also charge faster than SLA.

 

[justgary]

Link to last year's rules found by digging around in his other thread:

https://www.fgcu.edu/cas/centers/whitaker/files/sunchase/SunChase23RuleBook.pdf

 

[justgary]

It's would help to data-log the power draw, e.g. if the motor controller reports how much power it is applying, at min have the kids demo-run around and write down the min-mean-max of what they see.

I agree with this. Knowing the time history of the current draw would help a lot.

 

[florida cracker]

I guess what I am asking is if anyone knows of an off the shelf lithium battery that can run an electric motor at 40-60 amps and be recharged at a higher rate as well.

Am I asking for something nobody makes??

I will be able to get somewhat accurate current draw as soon as the Wrestling team gets my space cleared back out, lol

 

[justgary]

I guess what I am asking is if anyone knows of an off the shelf lithium battery that can run an electric motor at 40-60 amps and be recharged at a higher rate as well.

Am I asking for something nobody makes??

I will be able to get somewhat accurate current draw as soon as the Wrestling team gets my space cleared back out, lol

The catch is that you are asking for a 20 Ah battery with a 3C rating. Most LFP is rated at 1C or less. Other lithium technology has the rating you want. The good news is that you don't also expect it to last 6,000 cycles, so pushing the rating a bit might be ok.

 

[400bird]

Many 100 ah batteries can support 100 amps (or 50) but that's well outside your design limits.

Have you looked at ebike batteries? NMC can often do 5c or higher, that should ld easily fulfill your needs

 

[Vigo]

So i finally saw the rule about ‘open cell’ or custom batteries, so disregard that.

As far as finding low Wh batteries with high current potential, ive just realized that lifepo4 ‘powersports’ starter batteries are now down around $40 for the smallest ones. I just bought one to try. They are rated in single digit Ah but are rated for 150-500 cranking amps. I can licture a setup of ~36v in 3s2p with 3 tiny ‘starter’ batteries of 2-4ah in parallel with another string of 3x 14-16ah batteries which will have 15-20a continuous discharge limit. The two strings of batteries will have different characteristics but it should work out that the ‘combined’ instantaneous and continuous amp ratings can support your system, with the larger batteries and smaller batteries staying very well balanced to each other (for the race) due to treir low IR. Downside is thats a $300 pack at the cheapest, vs running a single 3s pack with an ‘insufficient’ continuous amp rating for $150ish.