Battery Choices

[Ferrino]

What batteries are popular for road-based 7s, these days? I see the Odyssey PC680 is still available - still a good, reliable choice? Thanks.

[Nick OTeen]

I've had a PC680 in my Caterham for eight years and it's still going strong.

[pksurveyor]

Walmart Jetski battery.

[Kitcat]

I have always joked that my Odyssey PC 680 was the only part of my Caterham that I hadn't replaced. But it finally died (to be replaced by another one). So now it's the frame basically:).

[waltermitty]

You can save about 10 lbs by running a lithium battery. I'm running one in the Birkin and also in the Van's RV-4. The PC680 weighs around 14 lbs and the lithium around 4.

[Ferrino]

You can save about 10 lbs by running a lithium battery. I'm running one in the Birkin and also in the Van's RV-4. The PC680 weighs around 14 lbs and the lithium around 4.

 

Which model lithium battery are you running and what is the compromise?

[waltermitty]

I am running a Ballistics in the Birkin. The company went tits up so I went to a Deltran with similar capacity and size in the airplane, https://www.amazon.com/Supersmart-Lithium-Battery-8-0AH-480CCA/dp/B07JV8X181/ref=sr_1_1?dchild=1&hvadid=78340318644571&hvbmt=be&hvdev=c&hvqmt=e&keywords=btl24a480cw&qid=1596803704&sr=8-1&tag=mh0b-20. I found that battery cheaper on ebay. The upside of lithium is they hold a charge for a very long time, they are much lighter and have slightly higher voltage. The downside is that they are more expensive. The Birkin is has been on the road for a year and about 3,000 miles with no problems. The one in the RV-4 cranks a high compression Lycoming IO-360 (360 ci). I actually replaced a PC680 in with the Deltran in the airplane.

[JohnCh]

I also have a Ballistic that replaced a PC680. After about 3 years of use, the battery started to have an occasional issue holding a charge for more than 2-3 weeks and was proactively replaced given Ballistic was having a sale at the time. That second Ballistic is still going strong more than 5 years later, but it is kept on a conditioner in the winter when the car sees intermittent use.

 

It's interesting to have a battery that is easily picked up with just two fingers, yet is capable of starting the car after it's sat outside overnight in mid 30F weather. When this battery eventually dies, another Lithium unit will replace it. I'm a convert.

 

-John

[Pokey]

EarthX ETX680. Roughly the same dimension of a PC680 so you can use in the same case, but is much lighter and has all of those great characteristics of a lithium battery like holding a charge for a long time.

[KnifeySpoony]

EarthX ETX680. Roughly the same dimension of a PC680 so you can use in the same case, but is much lighter and has all of those great characteristics of a lithium battery like holding a charge for a long time.

 

What case do you use for the 680? Is there an aftermarket solution, or do you have to fab it up? I'd like to go with a light battery on my upcoming build but not sure what the best/easiest solution is.

[Croc]

For the Odyssey PC680 there are a couple of case options

 

http:// SRX_PC680_BattHoldDown / Vertical Horizontal Mount [sR] Battery Hold Down Tray Battery Box Mount for PC680 Odyssey Mounting Bracket https://www.amazon.com/dp/B08D84BXD9/ref=cm_sw_r_cp_api_i_A3ZlFbTGWAWVF

 

or

 

Odyssey Battery HK-PC680 Hold Down Kit https://www.amazon.com/dp/B0045G4VZK/ref=cm_sw_r_cp_api_i_X5ZlFbB9TJESE

 

 

If the Earthx is the same size as the PC680 then these cases should work.

[ashyers]

Here's another one:

 

https://www.speedwaymotors.com/Micro-600-Sprint-Racing-Battery-Box-for-Odyssey-PC680-Battery,83562.html

[Pokey]

What case do you use for the 680? Is there an aftermarket solution, or do you have to fab it up? I'd like to go with a light battery on my upcoming build but not sure what the best/easiest solution is.

 

I'm using an inexpensive case EarthX sells, BB-MU, but there are a lot of choices that fit both the EarthX "E" size and the PC680. In many cases you will wind up shimming with foam supplied with the battery. The ETX680 needs about 3/16" on either side, and I believe that for the PC680 the shimming is front to back to account for the tapered shape of the battery. One thing to be mindful about is some cases allow battery removal only from the top, whereas others also allow removal from the front. The other option is to use one of the hold downs like Croc and Ashyers mention.

 

For what it is worth, I personally would not have spent the extra money to save that much weight. I've used lithium batteries in off-road racing motorcycles and for that application the weight savings was important to me, but for me and the Seven the real benefit is (sadly) being able to leave the battery unattended for long periods. I just sold a motorcycle that sat for five years with no tender on the battery and it still cranked.

Edited August 9, 2020 by Pokey

[Pokey]

Thought it might be helpful to post the dimensions of both the EarthX 'E' size case and the Odyssey PC680 case (information from the respective manufacturers' websites):

 

EarthX 'E' 6.5 L x 3.1 W x 6.6 H

PC680 7.15 L x 3.0 W x 6.65 H

 

And the weight:

 

EarthX ETX680 - 3.9 lb

Odyssey PC680 - 15.4 lb

 

If I remember correctly, EarthX has at least one other option that would work in this application that weighs less and has a smaller case, but I wanted to stay with a form factor that would allow for using the Odyssey too if needed.

[Ferrino]

Thanks for the feedback and suggestions. LiFePO4 appears to be a bit of a minefield. Despite being known as the safest lithium chemistry, I have seen examples of exploded cells and meltdowns which make me a bit nervous. I'm sure most of this is down to "operator error", but it makes you think.

 

I'm trying to stay in the sub-$200 price range, so the Battery Tender/Deltran offering is interesting ($200, 8Ah, 4 lbs). How about Shorai? They have a unit on Amazon for $172 that weighs in at 3lbs and is also approx 8Ah: https://www.amazon.com/Shorai-Lithium-Power-Sports-Battery/dp/B0088JGV2Q

 

Also: is there a unified definition of "CCA"? For example, the Odyssey PC680 has a CCA of 170. The Deltran is 480. The Shorai is 315. Given the PC680 is the gold standard for lead acid, should I assume that these LiFePO4 choices are as good at starting in cold temps?

[Sean]

Given the PC680 is the gold standard for lead acid...

 

It seems to be the most popular SLA choice, but I have always preferred the PC625 over the PC680.

[Pokey]

Thanks for the feedback and suggestions. LiFePO4 appears to be a bit of a minefield. Despite being known as the safest lithium chemistry, I have seen examples of exploded cells and meltdowns which make me a bit nervous. I'm sure most of this is down to "operator error", but it makes you think.

 

I'm trying to stay in the sub-$200 price range, so the Battery Tender/Deltran offering is interesting ($200, 8Ah, 4 lbs). How about Shorai? They have a unit on Amazon for $172 that weighs in at 3lbs and is also approx 8Ah: https://www.amazon.com/Shorai-Lithium-Power-Sports-Battery/dp/B0088JGV2Q

 

Also: is there a unified definition of "CCA"? For example, the Odyssey PC680 has a CCA of 170. The Deltran is 480. The Shorai is 315. Given the PC680 is the gold standard for lead acid, should I assume that these LiFePO4 choices are as good at starting in cold temps?

 

I can't recall ever having a problem with the Shorai brand, but my experience has been in motorcycles only.

 

I'll let others more knowledgable compare and contrast CCA and PCA of lead acid to lithium, but my experience is that lithium doesn't crank as well when temperatures are cold, but rather than go from cranking slowly to dead battery they do the opposite - as you crank the battery warms and things get better not worse. Again, just experience and not theory, but lithium batteries can be had with an ample CCA/PCA that are quite small, the sacrifice being AH. But I wouldn't think we need AH so much in a Caterham because of the lack of accessories.

 

The big differentiators between lead acid and lithium are price, weight and how long they hold a charge without load. And if you are willing to sacrifice AH you can also have a smaller form factor.

[JohnCh]

Greg, one tip with cold starts on a Lithium battery: turn on the headlights for about 10 seconds before attempting the start. This puts some heat in the battery prior to engaging the starter motor and was recommended by the manufacturer of my battery. It seems to work well in mid 30F weather.

 

When I researched Lithium batteries several years ago, it became apparent that you can't easily compare specs with SLA or AGM batteries. First, the discharge properties are very different. A SLA can be discharged about 30% before voltage starts to fall off, the AGM about 50%, and the Lithium about 80% (some claim up to 95%). This means that although a Lithium battery may have a lower AH rate than an AGM, the actual usable capacity could be higher. e.g. AGM rated 15 AH may have 7.5 AH available (15 x 0.5) whereas a Lithium rated at 10 AH may have 8 AH available. Second, the CCA test was developed for lead acid batteries and can't be safely completed by a Lithium. This page has a good explanation, but the short version is Lithium batteries can't discharging that fast without going bang. I've read that because of this, CCA ratings for Lithium batteries are either extrapolations or pure fabrication. PCA may be a different story since that is a 5 second test.

 

 

-John

[Ferrino]

Thanks John. It's confusing because some lithium battery manufacturers have taken it upon themselves to list a "lead equivalent" Ah rating on their batteries. So it makes it hard to compare with, say, an AGM, which has a better discharge profile than SLA. Often they will list the actual capacity in terms of W/Hr, which you can then translate into the actual A/Hr.