Pulse and glide battery issue/ ideas needed

[Weather Spotter]

Had some electrical issues this week. One morning (5:45am) my headlights died during a coast and came back on with the bump start. I quickly changed my SG to show voltage (dropped off engine temps since i leave the grill 100% blocked right now). My voltage was 13.9-14.1 with the engine on. With it off it was at 12V and dropped to 10.0v and the headlights would die. I decided that my alternator was not running long enough to keep the battery charged or is that a ?

So after work I went two blocks to my local interstate battery location. Bought a charger to hard wire in with the block heater, and I am working on getting a deep cycle battery to add to my reserve capacity. I got a big deep cycle (13" long, 210 min reserve capacity) bit I am having a hard time finding a place for it. its too big for the nose cone and its too big (tall) to fit in the tail under the floor. I have a box for it and could put it in the cargo area but I want it hidden.
I am thinking of getting a smaller battery, any advice on battery's?

Will I hurt anything by charging one battery and having a second hooked up to the system?

Ideas on how to hook up the battery?
best cables to buy?
Can I use old jumper cables and splice/ join them to get the needed length?

By the way I was running a great trip MPG till I had to leave the engine on to keep my lights on

[JRMichler]

An RV battery isolator might help.

Or else just wire the two batteries in parallel to get the equivalent of one big battery. They are both lead acid, so have the same charge and discharge curves.

[Sven7]

Can't help you on the electrical front, but you could always hide the battery in an old suitcase or small chest. It'll just look like you're hauling cargo. Minitruck folks do this all the time to hide the rear axle.

[brucepick]

Hooo-boy, that's a lot of questions. I'm a man of many words, for better or worse, so here goes...

What you saw re. battery fading in a long coast - I saw the same thing last winter. Mine didn't drop quite as far as yours did, but would drop through the 11.x range and down into 10.x if I didn't re-engage the alternator by bump starting the engine.

I came up with a cheap + quick solution I liked for last winter, and then built a better one this past summer that I like even better. With the new setup I've successfully tested a driving range of 3 hours plus, WITH headlights running. About 6 hrs. driving without headlights, if I use each of my two batteries in succession, one after the other. I have switches that can do that.

My cheap + quick remedy for last winter was a second starter battery, not a deep cycle, about 2x the size of the Civic starter battery. It came out of a Jeep, we just had it in the garage so I put it to use. In other words, it was not a monster size, but bigger than the Civic starter battery. I hooked it in parallel with the under hood battery and could easily coast 1-2 miles with lights on. Starting was fine too, engine would crank over very easily with the two batteries in parallel. Both would get charged when the alternator ran, of course.

Generally they say do NOT put two batteries in parallel, and now that I've set up a pretty evolved deep cycle system, I have two and they're separated, not in parallel. I DEFINITELY wouldn't put two different type batteries in parallel, such as deep cycle and starting type. I also wouldn't parallel two nice new carefully selected batteries, it would be bad for both of them. One will always be "stronger", aka higher voltage, and will discharge into the other battery. You lose a lot of charge that way, due to the various inefficiencies of batteries charging each other. (RVs and boats use multiple deep cycle batteries, those are the folks who learned the lesson to not parallel them. Better to use one, then use another, etc. - or have them run separate devices.)

In my current system -
For the starter, and to power the headlights:
I use a WalMart marine deep cycle Group 29, installed in the trunk, left side, ~60 lb. It's rated 122 AH, but that's at only 1A draw. I figure it might be about 100AH at 10 or 20A draw. The headlights are powered via relays now, so that made it possible to power them from the battery of my choosing.

I estimate the car draws about 10-12A, and the headlights also draw 10-12A, so 20-24A when running with headlights. I've run the whole car with lights using just the WalMart deep cycle but I wouldn't want to do that regularly, driving about 2.5-3 hours daily - and in winter that's all with headlights on.

The rest of the car (not headlights + starter) runs off a 40AH lithium LiFePO4, 12.8V pack. It's rated to handle a 100A load, and is internally circuit-protected with 100A as a limit. In actual use, it can run car + headlights but only for about 30-40 minutes. The nominal 12.8V pack drops to 11.5 or so in such use, and I don't want to take it lower than that. When I first had the deep cycle setup, I had the old starter battery up front, just powering the starter. And the lithium ran everything else including headlights. If I needed the lights more than 40 minutes or so, I'd have to stop and switch the alternator back into the circuit and run everything off the starting battery, just like it was originally built. I didn't want to charge the 12.8V lithium pack off the alternator, it's not built for that job and I didn't want the alt to mess up the pricey lithium pack.

So with the 40AH lithium being the only deep cycle in the car, I felt a clear need for more battery capacity. Thus the aprox $90, 100AH or 122AH WalMart lead acid battery.

[brucepick]

quick and cheap hookups

I didn't want jumper cables, with those spring clamp points digging into lead posts being your "contact surface".

I set the battery on the floor in front of the passenger seat. Later I moved it behind that seat, on the floor. Was fine there all winter.

I got a couple lengths of grounded outdoor extension cord. 16 ga? MAYBE 14ga? One length for the positive cable, one for negative. Each had 3 conductors. I stripped the leads and clamped all three bared wire ends onto the positive terminal with a regular stainless hose clamp, the worm gear type. Other end went to the under hood battery where I put a ring terminal on it so I could get good contact there. I just passed the wire up out from under the hood, and through the door hinge area. So the door pinched it when it closed, no biggie.

I did the same thing for the negative side. I ran the 3-wire cable all the way up to the front battery or maybe to where its ground meets the car. I really didn't need to do that. In my new installation, I have one battery grounded to the seat's rear mounting bolt. You need a really big ring terminal for that but you can get them, in a real parts store or in a battery/electrical store if you're near a big city.

For my current setup with the two deep cycle batteries, I used 4 ga cable like you use for a high end car audio system. I do have a length of 6 ga in one part of the installation but I'd prefer 4 there if I hadn't felt pinched for money when I bought that cable. The 6 ga goes to the main fuse box, not to the starter and headlight system.

[JethroBodine]

The easiest way, in my opinion, is to get the biggest deep cycle battery that will fit in your current battery box. They last plenty long enough for daily/weekly commuting, and if you hardwire a charger in the car, plug it in every couple nights and no worries. This is what I'm in the middle of doing right now. I have the wiring harness, charger, and battery already. Weather protective door for the plug is the last piece of the puzzle.

[Weather Spotter]

the issues is that my battery location can take only one size bigger battery (smallest deep cycle). I am not sure that the 120 min of reserve is going to do me much more then the 100 min on my (new 6 months ago) starting battery.

would it be bad to wire up two identical deep cycles to add capacity?

[Quezacotl]

So, i understood the headlights drain you battery mainly.
Have you considered installing LED daytime running lights, and other lights also, and in dark times, switch the normal headlights on, and not to use the P&G?

I have same issues that the battery drains. I have started to reduce the electric load, little by little when i have time

[JethroBodine]

Two in parallel is ok, big rigs use up to 4 in parallel for starting.

[Daox]

Reserve time is a horrible calculation of actual capacity. If you USED that reserve time with your starting battery you'd kill it very quickly (as you've found out). The deep cycle is not going to be damaged by your deeper cycling due to P&G. Just top it off every night with the plug in charger and you'll be fine.

The only other way to get more capacity in the same area is go with a lithium setup. Or, you can add another additional lead battery in parallel which is going to take up room elsewhere as you've mentioned.