Thread: Battery Woes

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Sorry for the long winded post, but here's the deal. Recall that I have one of the XS Power small AGM batteries, located up under the dash. After fighting hot starting problems all weekend in Springfield I came home and decided it could only be my crank fuel vs coolant temp curve, which leans out the crank fuel as the engine is hotter. This morning I went out, 84F coolant temp after sitting over night, and lit it off. My curve has values at 93F, 118F, 143F, 169F, 194F, 219F and then flatlines up to 320F (all coolant curves have the same range and breakpoints for consistency in adjustments). Brought it up to around 95F, shut down for five to ten minutes, and made very minor fuel adjustments to optimize the start at that temp - same thing up the range to 194F, stopping at each break point and thought I had it nailed. Let it sit for 1/2 hour or more, then was going to head up to get gas and check my trip mileage. Coolant was at 175F, unhooked the battery tender and the witch cranked and cranked, even with WOT to clear the fuel. Finally got it lit, but resorted to a little shot of ether for an easier ignition. At this point the battery was pretty well depleted, so I grabbed my jumper cables and hooked up my Jeep lead acid battery to the cables on the AGM battery.

With the jump, the starter cranks at least 1.5times faster than it ever has with the AGM, and the beast lit in two or three revolutions. With the jumpers hooked I made several starts at 192F coolant temp, and found that with a very small adjustment to lean out the crank fuel it would hit almost immediately, every time. This is telling me that my system voltage is dropping too low to provide a good hot spark, or maybe even too low to properly fire my injectors during crank. The answer may be to switch to a full size, lead acid battery, but that's a major issue for me as it would have to be in the trunk and I'm not going to do a shoddy install just to have it running.

I'm wondering if I may just have a bad AGM battery? Has anyone else running the small AGM's compared their crank speed and start with a bigger size lead acid battery? I'll be calling XS Power tomorrow, but thought someone here might have had experience to help me out?

Roger - I have to say that the Odyssey that we discussed in some detail a few months ago cranks my mild 302 exactly the same as the big Optima and maybe a little faster - but that's probably only desire. I started with a dry fuel system so had to crank a bit longer then normal and - it still cranked nicely, going through the start then stall routine several times while the fuel system filled and the engine warmed a bit

What's the voltage at the terminals, before, during and after a crank cycle? That should tell you the story and will probably be what XS will ask you

Dave,
With the battery at 13.07V (not at float voltage yet), it dropped to 10.85 and rebounded to 11.01 during crank, and this time it lit quickly. On shutdown the battery voltage was 13.05V, no significant drop in power which is not surprising given about three to four seconds of draw. It appears XS is going to want me to send my battery to them for a complete diagnostic check, to know for sure if the battery is weak, or if it simply does not have sufficient power for my needs. I'm to talk to a specific guy tomorrow and find the path forward.

Let us know the outcome ok? i have space constraints in a project and have been looking at the same battery.
Thanks, oj

Originally Posted by ojh

Let us know the outcome ok? i have space constraints in a project and have been looking at the same battery.
Thanks, oj

Both XS and Odyssey have good reputations - I had no problem with either, just found a better price for the Odyssey - and think Roger just got a weak one.
Space and weight saving is significant vs an Optima

Roger, I'm curious, how is the battery circuit wired, positive and negative from the battery are attached where?

Mike

Originally Posted by Mike52

Roger, I'm curious, how is the battery circuit wired, positive and negative from the battery are attached where?

Mike

Mike,
My battery is centered behind the dash mounted horizontally, terminals facing the seats. On the '33/34 there is a hollow "kickout" on each side of the firewall, and I have Moroso bulkhead connectors mounted there, penetrating the kickout, very nearly out of sight even from the front. The bulkhead consists of a solid 3/8" brass stud on each side, and a threaded plastic housing that penetrates the firewall/kickout panel and is retained with a "conduit hub nut". The positive and negatives from the battery go direct to the bulkhead on the inside of the body. In addition, on the positive battery terminal I have a #12 that feeds the ECU direct. Other hot feeds, like fan, fuse box, etc come off of the inner bulkhead connector - I moved the ECU feed to eliminate any cable drop, though the battery to bulkhead connections are only 18"(+) and 24"(-) long. On the (-) inner bulkhead there's a braided grounding strap that connects the (-) bulkhead to a body retaining bolt into the frame. On the outer end, the (+) goes direct to the starter, 12" away; and the (-) lands on a starter bolt into the bellhousing. I've seen it written that the (-) should terminate on a bellhousing bolt, but not a starter retaining bolt, but I've never understood how that makes any difference at all - one threads into the bellhousing, and the other into the block through the bellhousing.

Roger, I remember seeing the pic in your build thread showing the battery mounting location, a very nice idea. My main interest was the negative side of the electrics, as you know well, grounds can be a major contributor to gremlins, especially in a ‘glass car and I was curious what methods you used. As usual you give lots of thought to the solutions. I also don’t understand the logic of terminating the negative run at the bellhousing bolt vs the starter mounting bolt. I’ve always used the starter bolt, especially in hard start situations, simply due to electricity likes the path of least resistance and that gets the ‘juice’ straight to the starter.

I hope you solve your problem soon, hopefully Nathan will be of help tomorrow.

BTW, with the technology and benefits of AGM batteries, I would never go back to a regular lead acid battery again. JMO

Mike

Wonder what kind of load is on the battery with ignition power and fuel pump up. Consider this FI and its components require a bit more static juice then a carb with a mechanical fuel pump. Then add the starter load and you just might have a battery that is not up to the job.

I think that if you could graph the little battery you might find that the line would be heading south at a faster rate then a full size battery. There is a reason that the majority of the cars have the larger platform, it could just come down to the physics and in this case size just could be a factor.

You said it spins over faster jumped that could be telling you something. Ground to starter or bell housing got to agree I cannot think of a good reason that would matter.

It probably has something to do with what is called back emf. As the starter spins it creates a magnetic field around the case and the reasoning is probably the manufacturer doesn't what that to in any way to flow back towards the battery. I would have used at least 8 gauge and mounted it to the frame if possible.

Originally Posted by NTFDAY

It probably has something to do with what is called back emf. As the starter spins it creates a magnetic field around the case and the reasoning is probably the manufacturer doesn't what that to in any way to flow back towards the battery. I would have used at least 8 gauge and mounted it to the frame if possible.

Ken,
I appreciate the input, but everything I've ever seen says the negative cable goes to the block, then you ground the block to the frame with strap or cable. My Jeep has a split negative cable, with one bolted to the side of the block, and the second to the firewall (not the frame). I've got a ground strap going direct to the frame from the bulkhead connector, and the cable then going from that same point to the engine block. I really don't think it's a ground problem, but then I could be wrong.

Roger, I've done it both ways, but I agree as I would bet than one of the cells in the battery is weak.

No answers yet, but just got off the phone with Byron at XS (Nathan's out on holiday). After a lengthy discussion on the history we agreed that the only way to really know for sure if this battery is right for the application or not is for them to do a full diagnostic check on it. It's heading their way in today's mail, so we should have an answer by weeks end. If it's a capacity issue then I'll be looking at reworking my trunk to tuck a bigger battery into the corner, or worst case moving the gas tank over a few inches to make room. Fingers crossed that my S680 is weak under load, and a new one will fix the problems.

I run mutiple grounds on a loop, a #2ish at the engine block and to a stud welded near the battery, and make a loop with #10 wire. I ground each cylinder head as well and share that ground direct to the ignition.
I do everything possible to get everything at the 'same potential' esp with modern electronics. When i carry a hot wire to a termination i carry its' ground right along with it - just like you'd wire your house.
I use more wire than most, but wire is cheaper than fixing problems in a few years.

Originally Posted by rspears

No answers yet, but just got off the phone with Byron at XS (Nathan's out on holiday). After a lengthy discussion on the history we agreed that the only way to really know for sure if this battery is right for the application or not is for them to do a full diagnostic check on it. It's heading their way in today's mail, so we should have an answer by weeks end. If it's a capacity issue then I'll be looking at reworking my trunk to tuck a bigger battery into the corner, or worst case moving the gas tank over a few inches to make room. Fingers crossed that my S680 is weak under load, and a new one will fix the problems.

My guess - you'll have a new one 'in the mail' 15 minutes after your old one arrives at XS