Light Weight Battery

My car needs a battery and I'm thinking about buying two big Shorai s and putting them in parallel. that will give 70AHr and plenty of CCA. it will cost about 550 but they should last twice as long as a lead acid (which costs about 200 bucks for a good one). This would be 40lb weight reduction. Anybody done or seen this? What am I missing?

I haven't seen Shoai before, but I did just buy an Antigravity Battery (AG-H6-24-RS) for my car. It is 9.8lbs, but only 24Ah. However they have up to 60Ah as well. I bought it at 15% off earlier in December. https://antigravitybatteries.com/pro...tive/ag-h6-rs/ What sold me on them was the extensive amount of information provided by the owner, and Rennlist sponsor, over on this thread. He wasn't disparaging of others, just good information. It's older, so he's initially talking about a smaller non-stock size AG, but the newer one I got is stock size. https://rennlist.com/forums/991-gt3-...r-2-gt3-2.html Again, I don't know Shoai, but the above thread mentions alot of good questions to ask about lithium battery technologies. It seems that motorsports batteries, especially for motorcycles may not be as maintenance free since the users usually maintain everything between uses, especially if they allow the LiFePo to discharge below 10.5V, at which point they can become dangerous (fire hazard). That's not an issue for some but it depends on your level of comfort. This is why the Antigravity Batteries have an automatic sleep mode, and an appropriate Battery Management System for a typical car. But anyway, maybe read that thread for at least some good thoughts, then decide. BTW, my stock battery was 44.6lbs. The new AG was actually 9.13lbs (weighed on a kitchen scale). Savings of 35.5lbs

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Thanks. I was looking at the anti gravity batteries. A 40 AHr would run me 800 bucks. Two Shorais about 550. Shorai says they don't recommend configuring them in parallel but they wouldn't say why. For 550 I can barely rationalize it

I looks like two Shorais would actually be much less real amp hours than the 70 I quoted. I certainly like the ease of packaging of the anti gravity and the cut off feature

A general issue with batteries in parallel is load balancing. With minute differences is internals they can have slightly different internal resistance, or even just slightly different starting points, and therefore they will charge/discharge at different rates. Multi cell packs will have either a battery management system, that among other things will measure individual cells and contol the charge to each one appropriately, or cheap systems just have resistors that will bleed off excess current from higher voltage cells. I'm speculating a little, but I think that with different charge levels, and therefore slightly different equilibrium voltages, that when you turn the car (alternator) off, there could be a current loop just between the two batteries. That would cause excess heat and faster battery discharge. The discharge would be uneven, and the problem would grow worse as they discharge further. It seems it would be slow and just show up as a minir additional parasitic drain. But that's all theoretical, and I'd love for someone else with knowledge to weigh in. ​​​​​​

From ‘69 to ‘73, all 911s had two batteries in parallel so it’s probably not a problem. That said, I would just keep the regular battery. Saving weight in the front doesn’t really make sense in a 911 unless you pair it with a weight saving in the back.

If you are that close in price, I�d consider the Antigravity. You probably only need the small 24Ah one, as even that little guy probably has over 1,000 CAs.

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yeah thats my plan. thanks for the info.

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Hi Everyone, please keep in mind, we generally only recommend a 24Ah option for dedicated track set up vehicle as it's an extremely small capacity size. When you're ready to move forward dougn please feel free to reach out to us to see what we can do for you and we can go over best options for capacity based on vehicle set up and use. Best regards, Chad [email removed]

Why would I need more than 24 AHr? How long would 24 AHr crank an moderately sized engine?

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I'm sure that the 996 being a little older, has more parasitic draw when off than newer cars. Have you gotten any feedback on how long these batteries last without a charge on the 996? I have no problem putting mine on a charger when back in the garage, and I don't have any additional accessories, so I'm okay with the 24Ah that I got, but I'd be interested if you have any feedback so far. I'll report what I can once mine's hooked up. I have the Antigravity bluetooth battery monitoring device too, so I should get some good data on the draw down once installed.

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Because it not about starting the Car actually... that is easy for the Lithium Battery, you can go with a much smaller one and get it to turn the motor over easy. Its about Capacity and covering the Parasitic draw, and having a battery that would start in colder weather, or provide emergency lighting and extra starting power in the event the battery is drained and you have to crank a lot. People tend to think its only about the start, but it about Capacity, and 24Ah is quite small when you consider that people will sometimes put USB Chargers, Stereos and other items in their cars. We just want a slam dunk for a battery, and prefer not to have someone call us saying that the battery drains faster in their particular Car. Its just best to get a good capacity for your car unless you are racing in which case your on a closed course and won't come across being stuck out in someplace far away.

Quick question, I have an antigravity H6 40Ah battery in my 996, can I jump another car with a regular lead/acid battery? will it damage my antigravity battery? Thanks!

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Hi Gig replied to your DM on this question..but for anyone else wondering the same, the H6 can be used to jump another vehicle in same manner you would with any other vehicle car battery. After the vehicle being jumped is started you just want to be sure to disconnect in reasonable amount of time as you don't want to be charged two batteries of different capacities or chemical make up for long duration together. Best regards, Chad ([email removed])