Electrathon America Forum

etailleur · Newbie

Best batteries

Nitoragro · Senior Member

First off welcome to Electrathon! Where will you be racing at?

This is probably one of the hardest questions to answer but I will do my best.

I would say lead acid would be the easiest for a new team, and there are a near infinite types of legal batteries. What is in the rulebook are the only batteries you do not need to weigh. You could use a bunch of AA batteries and run your car like that, but please don't use a ton of AA batteries.

The most common type of lead acid battery used are the optima yellow top deep cycle battery. In Tampa red top was also used a few years back, which is a starter battery. However back in high school when I ran lead acid I never ran either of these types of batteries because of cost, they are around $200-$250 each and you would need 4 batteries, 2 for each set running 24v for $800-$1000. One good thing about these is if they are well taken care of they can last for years. One team here ran a set of yellow tops for 7 years.

I was a huge fan of Duracell 35-12, which were basically wheel chair batteries (link at the end), I made a battery tester so I could get the amp-hrs out of each battery. These are rated for 35 amp-hrs, however in Electrathon racing we draw a lot of power quickly, so i was only able to get 25-26 amp-hrs from each battery which is about 900 watt-hrs in a set, which is GREAT for electrathon. I was able to use these for 2 years before I graduated, I know you can use them longer, I just don't know how much longer. For these batteries you would need 6 batteries, 2 per set running 36v. So its about $540 for all 6.

I also used the mighty max 35-12 which worked well and were a bit cheaper, about $400 for all 6 (link also at the end). These did have a little less juice in them but they still worked great for me.

Another small bonus for using these 35-12 batteries compared to the yellow/red tops is they are about 4 lbs lighter

Unfortunately when I graduated I also left my battery testing notes at the school, so these numbers for power are just from memory and are not exact, but they are pretty close.

Best of luck and let me know if you have any more questions
Ryan

Duracell
www.batteriesplus.com/battery/sla-sealed-lead-acid/12/sladc12=35j

Mighty Max
www.ebay.com/p/Mighty-Max-Ml35-12-12-Volt-35-Ah-SLA-Battery/1725435082

Archer321 · Senior Member

What voltage does your motor and controller support? Most can handle a small range of voltages but even so there are limits. There's no need spending money on a set of batteries just to find out that you can't use them with your equipment.

etailleur · Newbie

Thanks guys for those replies. I have a good budget and what i understood is that even if they're expensive, yellow top would be a good choice ?

We plan to be on a race shortly but need to check so many thing before to be ready.

Thanks again for the answers.

Nitoragro · Senior Member

If you don't mind could you start a new topic on building your car and your first race? it would be really cool to see a new team getting started

Going off of what Archer said, most teams use the etek (24v-72v), ME0708 (24v-72v), or ME0909 (24v-48v) so these would all work for the batteries we are discussing. But you would need to do some research on what type of controller you would need.

If you have a good budget and don't mind spending extra then yellow tops are a safe and easy choice and you can do very well with them. The reason I personally picked to run those other batteries was because of our small budget, but I still did very well on them winning in my high school class, and tying for first in the southeast United States.

However there is one thing that all the best teams have gotten very good at, and its battery maintenance. Here in Florida we had a high school who bought a brand new set of yellow tops and DOMINATED in their first race, but by their 3rd of 4th race (about halfway through our season) they had trouble finishing a race. The problem was they would never charge their batteries until the night before the race, so they would leave them discharged for a whole month.

So what I did to keep my batteries racing were:
-After a race charge them that same night, i spent a few nights in hotels with my battery charger humming and red light blinking
-If my car ever died and I was going slow I would see where I was, if I knew I would finish near last I would just quit to save the batteries, if I thought I had a chance I would keep going

I bet there are more things people do to keep their batteries healthy, but with whatever LEAD ACID battery these things should keep you running very competitively.

If you do decide to do advanced batteries there are different rules for proper battery maintenance, these all are just for lead acid.

Zaine Stapleton · Senior Member

There is a flaw in the advance battery class. Based on the data of the battery manufacture, say for a lipo battery, if the total power output in watt hours shows to be only able to do 1250wh total you should be able to run a battery pack set regardless of weight. The writing for the rule doesn't make any sense, point being a lipo can't pull 1250wh without destroying the pack. You'd really run it until 80% capacity (1250*80%=1000wh total). This rule should be updated to better reflect the reality of what you can actually do with cerian batteries. If a driver chooses to run their pack past 1000wh then that's their problem if they ruin the pack.

Brendan_Smith · Veteran Member

Hey Zaine,
No doubt those with direct experience will reply reasonably shortly, but in my outsider's experience in reviewing results, the combination of 1kWh for all chemistries, and further mass allowance for pack densities, appears well-sorted and appears to give an even playing field already.
Choosing an advanced chemistry already gives a distinct weight advantage but causes some loss of peak power output against a cold-cranking battery cell; the loss in power available at low charge states is merely another trade-off.
Further modifying from the 1kWh rule for individual chemistries would mean redefining allowances as battery technology / cell design changes and would prove to have diminishing returns.
Having said that, perhaps put a proposal into the Rules are for deliberation?

ProEV · Senior Member

Zaine,

It is very tough to get 800 whrs from a lead acid pack. I think new battery yellow tops tested out around 720? Dave Cloud is the only person who has been able to barely break 1,000 whrs and that required special heating and charging. So setting the Max manufacturers spec of 1,000 whrs means that if you want the best life for your advanced batteries, run them to 80% and get a highly competitive 800 whrs. Or if you are rash, try and get the manufacturer rated capacity which is 1,000, not 1,250.

As I said in another thread, I would love to see an inexpensive black box that we could set to a specific WHR setting cut off, since all types of batteries we have raced with, die much sooner when discharged completely.

Zaine Stapleton · Senior Member

Funny, because when I used to run Red tops I could easily get close to 1100wh out of my batteries. When I made the switch to Yellow tops, I could get 943wh or close to 1000wh out of mine. I'm very maticulous with my batteries and how I run them. In terms of LiPO packs, it's actually harder to get 1000wh out of them. Like you can pull 1000wh from them no problem, but it comes down to the track, how many cars are on the course, and how often do you come up on traffic? I now know how to run them and make the most from them for the race in McMinville, Oregon this weekend (Aprio 20th). The bigger thing is how to keep it a a 1C rate while still being effective, safe, and being efficient at the same time.

Zaine Stapleton · Senior Member

Going on ten years of racing (yes, that is how long I've been racing electrathon cars for) and figuring this stuff out, you learn quite a bit from doing this Along with all the tricks and tips too.

Zaine Stapleton · Senior Member

Plus also too, depending on how far you run LiPO batteries down, sometimes you don't need to recharge them. When checking the cell voltages on them it down to say 3.80v per cell roughly (plus or minus 0.05 volts) you might not have to charge them back up. LiPO batteries like 3.80v for a storage charge. Lead-acid on the other hand you have to charge them back up after a race. I'm meticulous with my batteries, since besides the motor and controller; batteries are the most expensive thing that go onto a car. Once a race was over with, I always got the batteries out of the car and got them back on the charger. If you leave any type of lead-acid battery discharged for too long, the cells will get crystals on the battery plates and make it harder to charge them back up. That's why with flooded car batteries or golf cart batteries you do a equalizing charge on them to break up the crystals. AGM batteries are different more of you just get them recharged and typically keep them around 13.6v for storage charging, which is also rhe same for when you are chargig up for a race, eitherb13.6v or 14.8v is whatbIve found to be the best. And warming up lead-acid batteries to 110 degrees F makes them run better. For storage, you can take them off and leave them off the charger for a few months and let then drop to 12.6v or so. But lead acid batteries don't really hold s charge to well. I use Iota chargers and have a IQ4 hooked up to it to keep the batteries fresh, once a week thr charger jumps it up to 14.2v or so and leaves it here for a few hours then drops it back down to 13.6v.

ProEV · Senior Member

Zaine,

Wow, 1,100 Whrs is the highest pack capacity I have ever heard reported. That is impressive. Shannon Cloud gave 42+ as their best which is 1,008+. (How much plus is open to speculation)

Back when I was running lead acid, I was a regular race winner with a pack capacity of less than 700 Whrs. I only had one pack, so a fast recharge between races warmed the pack and I got about 10% higher capacity the second race.

Did you measure 1,100 in a static test or racing? How were you tracking your Whrs? Were you using any special charging routine?

Archer321 · Senior Member

Yes, all good questions. I await the reply... (Always interested in learning something new (and I'm still running lead-acid))