New Pending Battery Box Design

[Bill_VA]

As some of you might have been made aware of, FFR changed their chassis design a bit in mid-2017 and added a 3/4" brace above the new 2015 IRS mount, which is right where the FFmetal battery box would be mounted.

I've been mulling over ways of working around this, and I think I may be on to something.

Obviously I'd have to go with a smaller battery to design the box around. I took some measurements on JRcuz's car this weekend and it seems the limiting dimension is the depth of the box (front to back), which is 5 inches now between the new brace and the existing brace the boxes are riveted to. Plenty of room width and height-wise. So my quest is to find the best battery 4" deep or less, with enough Cold Cranking Amps (CCAs) to design the box around.

There are new lithium batteries out there, but their design rules them out in my book, mainly due to their inability to crank an engine longer than 10 seconds or so and then needing 30 minutes to recover. And if you run seat heaters, wipers, radio, etc., it just can't keep up. Would be great for a race car, but not a street car.

Keep in mind the specs of the typical battery the FFmetal box was made for, the Optima Red Top 34. Weighs in at a whopping 38 pounds, has 800 CCAs, and costs about $240.

Here are a couple of AGM contenders.


Braille B2317 (https://www.braillebattery.com/index.php/braille/product_batteries/b2317) (ad from Jegs (http://www.jegs.com/i/Braille-Battery/147/B2317/10002/-1)) Nice battery, only 17 lbs, 475 CCAs, around $200
Odyssey PC1100 (http://www.odysseybattery.com/extreme_battery_specs.aspx) (ad from Jegs (http://www.jegs.com/webapp/wcs/stores/servlet/SearchResultsPageCmd?Ntt=Odyssey+PC1100&requestYear=&storeId=10001&catalogId=10002&langId=-1&year=&make=&model=&submodel=&engine=&Nrpp=&No=&persistYmm=false)) Also nice, a bit heavier at 27 lbs, a little stronger at 500 CCA, around $247



I'd like to hear your feedback.

[alv69]

I run the braille battery in my rat rod truck with a 409 chevy in it and the first one held up for four years, am on the second one now.

[Erik W. Treves]

I have used XS Power Batteries D925 - XS Power AGM Batteries with great success and they are only $180 25#
as well as

XS Power Batteries S975 and it's $190 26#

[Bill_VA]

Erik, thanks but the S975 is a bit too big. Must be 4.5" deep (front to back) or less.

[Erik W. Treves]

I have also used the XS Power AGM Batteries S375 for my 347 289 FIA car without issue.

[TXdad]

That would be great. Once figured out, I would be interested. Any thoughts about small dual batteries, more complex, but opens up more mounting and battery type options?

[Bill_VA]

TXdad, I had considered using two Optima 6 volt Red Top batteries in series. There's certainly enough room for them, but the battery box would be about 22" long, and two batteries would cost about $386.

[rich grsc]

Don't need a battery box. :rolleyes:
79328

[CDXXVII]

I don't think I would go any smaller than the Braille B3121. I had to make my box smaller for different reasons and this one works great. Not sure if 5.2" is too wide though.

http://www.jegs.com/i/Braille-Auto/147/B3121/10002/-1?CAWELAID=1710623499&CAGPSPN=pla&CAAGID=44693592161&CATCI=aud-224375369591:pla-192430099271&CATARGETID=230006180039217211&cadevice=t&gclid=Cj0KCQiAv_HSBRCkARIsAGaSsrAdWQZG3vslQ59WkGjq 6GevRc365JTh3sG4J977SeOPxOP83G55nYwaAgIuEALw_wcB

[Papa]

Not too many choices in the depth range you are looking for. Here is a dimension chart I found:

http://www.batteryweb.com/bci.cfm

[Fugi]

Another issue to consider is a battery box built to fit either a number batteries or a battery that will be around for an extended period of time into the future. I've also looked at some "tractor" batteries which come in shapes that are wide and shallow, but who knows if they will be offered 5 years from now. Seeing the picture of the battery in the engine compartment from Rich GRSC, got me wondering if the rear battery box could be accessed from rear, where the trunk drops down above the gas tank, still be above the 3/4" brace, and put the battery on its side. I don't know how well a battery is built to handle the bumps, G Forces and such with it on its side.

[Bill_VA]

Another issue to consider is a battery box built to fit either a number batteries or a battery that will be around for an extended period of time into the future. I've also looked at some "tractor" batteries which come in shapes that are wide and shallow, but who knows if they will be offered 5 years from now. Seeing the picture of the battery in the engine compartment from Rich GRSC, got me wondering if the rear battery box could be accessed from rear, where the trunk drops down above the gas tank, still be above the 3/4" brace, and put the battery on its side. I don't know how well a battery is built to handle the bumps, G Forces and such with it on its side.

Braille batteries have been around for a long time, I think it's safe to assume that they'll be around for a while more. Optima may go belly up tomorrow, never know. The AGM batteries can be mounted on their side. There is a fair amount of space under the floor, above the gas tank, but some guys like to do a drop trunk mod. Almost nobody has done any mods to the area above the diff where my battery box goes.

Good ideas though!

[edwardb]

Braille batteries have been around for a long time, I think it's safe to assume that they'll be around for a while more. Optima may go belly up tomorrow, never know.

You mean Optima Batteries, Inc., part of Johnson Controls, a 50+ billion dollar global conglomerate? They've been around a long time too and not going anywhere. I think you're safe designing for them too.

[cgundermann]

You mean Optima Batteries, Inc., part of Johnson Controls, a 50+ billion dollar global conglomerate? They've been around a long time too and not going anywhere. I think you're safe designing for them too.

Agreed - Optima sponsors so many motor sports events...

Chris

[Bill_VA]

My standard battery box is already designed specifically for an Optima battery. Now I'm looking to offer a much smaller box for new MK4's with the 2015 IRS rear. I need to target a single setup to offer. I'm not sure about making it for two Optimas in series - I need to talk to their techs.

[Fugi]

So it looks like there are two options for batteries that are common and likely to be around for the foreseeable future:
1. A smaller, less powerful (~500CCA) AGM battery (Braille B2317 or Odyssey PC1100) @ around $200-$250.
2. Install two Optima 6 volt Red Top batteries in series @ around $400 total.
I know that lots of guys have a very tight budget when building a roadster. However, if the owner is doing the IRS then I suspect that car is probably not going to be one where $200 more for a battery will be a major decision making factor.
I don't know what complexity would be added to the installation and maintenance by wiring the two 6v batteries in series, so that might warrant some discussion. Would there also be some cost.
The higher compression engined cars with IRS will probably want the higher CCA of the dual 6v. I also find that to be a worthwhile investment, should we ever find we need to start our car on a cold day.
I believe that battery technology will improve to the point where smaller batteries have all the CCA of the full size batteries today. So it would be a good idea to put a separator in the long box, so that if a single battery can get the job done only a minor change in wiring would be required. Actually, it might be a good idea to physically separate them anyway, for a number of reasons, not least of which is added structural integrity to deal with the G-Forces of racing or, God forbid, an accident.
So, unless there are some major downsides associated with the dual 6v option, I'm leaning that way, but am interested in reading opinions of others more knowledgeable than me (which is just about everyone, as I have yet to even achieve go-cart).
Vince

[mlewis]

Bill,

Looks like the 2x Optima 6v red tops check all the boxes. I don't think these is much downside with routing to batteries in series. I too would be interested to get some more input/opinion on this.

When do you think you will have a design and product available as I would like to incorporate this in my current build ?

Mark

[Bill_VA]

Yeah, Mark, I think that's the direction I'm heading. I ordered two 6V RedTops tonight to start the design. It'll be 3-4 weeks before they'll be ready to sell.

[Fugi]

Bill, We (actually meaning Richard Oben), has been working on the wiring; laying out harness and such for our car. We have a rolling chassis (IRS), gas tank in now, so it is much easier to see where a drop box like you are describing would fit. Frankly, I'm really not sure. There does not appear to be 22" between the tank mounts or between the 3/4" braces for the IRS below the new brace. I can post some pictures if you like or send them via email or text.

For what it is worth, Richard is not a fan of the dual 6v battery idea.

I will let Richard respond with his perspective.
Vince

[Bill_VA]

Here's a visual. I got the batteries tonight and have begun the mockup (current 12V box in photo). Probably closer to 20.5"
http://www.humtech.com/4bill/IMG_2380a.gif

Not sure what would possibly be the hangup with two 6V batteries in series. Same AMPs, voltage, etc as one 12V. You can even charge them as a single unit.

[cv2065]

Any update to this thread? Was disappointed to find out that the current FFMetal rear battery box won't fit with the new FFR design. Thanks!

[Bill_VA]

My fabricator, the one FFmetal has used for 13+ years, seems to be a lot backlogged, but is hopeful to get some prototypes to me soon. It's a painful process for me waiting, but it is what it is. Please be patient if you can.

[initiator]

Charging two batteries in series can end up with the batteries being at different charge levels. Each battery charges at a slightly different rate even when new. One can end up overcharged while the other is undercharged, but since they're connected in series, the overall voltage looks correct. The overcharged battery will wear out faster, even if it's lead-acid. The Optima batteries are AGM, which is more sensitive to overcharging.

You see this problem in LiPo drone batteries, where several small batteries are connected in series. To overcome the problem, you use a 'balance' charger where each cell is given the correct charging voltage. That would take special wiring and a 6V charger in this case.

If both 6V batteries are exactly the same age and use history, it might not be a big problem. I wouldn't mix and match battery types or ages, though.

[frankb]

X2 on what Initiator said about battery ages when using battery packs of two or more. However, golf carts, electric vehicles, battery backup systems, etc. have been using multiple batteries in series almost forever. When using battery packs of multiple batteries, the charger is the key to proper charging. Most golf cart chargers start with a high rate of charge and gradually taper to low charge rate as do most normal chargers. The difference is that golf cart chargers (or chargers designed for battery packs) finish with a long (3-4 hr) "float" or "equalizing" charge (low rate). As long as your charger is programmable, or has this equalizing feature, you will be fine.

[initiator]

I understand a special charger is needed for AGM batteries, since they want to charge slowly. Maybe that will be enough to accomplish the 'float' charge frankb suggests.

Using the right charger is fine for initial charge and coming out of storage, but every time the car is started the battery goes through a small discharge/charge cycle. The alternator is your charger, and it doesn't have special charging profiles that I'm aware of - just pumps as much current as your battery will accept at the alternator's voltage level.

To be clear, I don't know if this issue would actually cause a noticeable reduction in life or other problems as the batteries age. I'm very careful in how I treat energy storage devices, so this is not a path I personally would take without special electronics to charge the batteries individually.

[Fugi]

A friend built a box for me out of steel, that I painted and bolted to the frame. Then I fabricated a piece of aluminum into brackets to hold them in place. Thus far it starts the car just fine (about 10 miles of go carting).

[miller7448]

The 12V battery has 6 "cells" connected in series. The 6V has three cells in series. Agree with comments about being same age and model, but other than that should be no problems. Electrically it is identical. Looks like a great modification! (EE and used to work for Johnson Controls many years ago)

[Brian76]

Resurrecting this thread and wondering if any battery box kits are available yet?

[Bill_VA]

I wish I had better news. I'm at the mercy of my metal fabrication shop. I'm forever hopeful that we'll have something soon.

You all will be the first to know when they're ready.

[tonywy]

I just have to say this as a tid bit of info. I have a Optima Red Top date code 12/05 and still cranks over a hot big block...