Battery mod not working out?
 

I have installed an onboard voltage meter so I can monitor it live while I drive. I have a new lightweight deep cycle battery that seems to work fine. I charge it at night and in between runs with a plug in on board 1.5amp maintainer. My goal is to install an alt disable switch for short runs, such as my 22 mile round trip commute. Some observations and questions:

While in EOC during daylight the charge will sit at 12.5 volts and when I bump start it instantly jumps to 14.3 or 14.4. Back to EOC it drops to about 13.0 or 13.1 and then starts to descend to 12.5, getting there inside a minute, maybe less. Then it will sit stable at 12.5 volts.

Question is: that is quite normal, no? But doesn't it indicate that my alternator is coming on immediately upon bump starting, every time? If so, doesn't that mean that I won't really get the benefit of the deep cycle battery until I can disable the alt?

Yes your alternator is charging.

Yes that is about normal.

Yes you will have to disable the alternator by pulling the belt( if able to) or with a kill switch.

Your alternator is working less hard with a full charge to start with, so there is some benefit, and the deep cycle is more suited to this kind of use than a regular automotive starting battery.

You are moving along the same path that I am, but I have a few larger fish to fry before I get back to alternator work. I have the kill switch already working, but the old starting battery I have won't die.

Thanks for the response, hey. My old starting battery held on a long time too. In fact, it probably would still serve, but I got tired of it's occasional semi-failure and of kinda fearing a sudden complete failure at some point when I might really need it to work.

I tried a full alt disable late today--took off both the white cable and the 4P connector, leaving the belt in place. A test run was satisfactory. Over about 15 miles the volt meter showed a decline from the 12.5 to 12.1/12.3. LED brake and running lights probably help a lot, as did the maintainer, I'm sure.

I am at a loss as to a really good plan for the alt disable switch and how to integrate the 20w/1.5amp solar panel that will complete this mod.

I have a trip planned for tomorrow that I can't avoid and that I plan to do alt free... we'll see if I make it!

james

There should be a battery voltage feedback line separate from the thick high current line. What i would try is to build a circuit that keeps this line a couple volts above the actual battery voltage.

Simply unhooking it at the battery and and reconnecting it through a couple of NiMh in series might be enough, but you might want a more elegant solution that doesn't require you to keep them charged for the long run.

It almost sounds like the battery is never getting a full charge.
Your typical 40lb lead acid battery holds up to 2 kwh from 0 to a full charge and about 1kwh of useable power between 12.8v to 10.8v volts.

I charge a lot of batteries at work and that sounds pretty typical, where the voltage starts high and then drops once the battery starts to take on power.

I had a 1.5 amp charger for a long time, seemed to work ok for my car, but was useless for propery charging the large battery in my truck.
The problem is large batteries soak up 1 whole amp just to maintain when fully charged so at 14v realisticly you only have about 0.5 amps of useable charging power through out a good portion of the charging cycle.
To make sure your large battery is fully charged you want to get the voltage up to between 14.7 and 15 volts and make sure the battery is drawing no more than 2 amps, depending on size.
For charging real batteries you need a real charger.

I have some salvaged solar pannels and I am going to configure them for 22.5 volts for float charging the 12 volt battery in my truck. When I configured the panels for 15.7 OCV they could not push hardly any amperage through my half dead test battery.
From what I have found solar panels that put out any less than 17 or 18 OCV are useless for charging 12 volt batteries, they look cool but don't really do anything.

Running it yesterday afternoon without the alt, the car ran more smoothly. Batt only got down to about 12.1 volts. I'll experiment with running it lower today, closer to 11.0 maybe if the car shows no sign of operating difficulty. Sound reasonable?

My new battery is actually smaller than stock. I considered a smaller and a larger battery for a long time. For the sake of my weight reduction goals, I took the risk. I know it might not last or might not even workout, but I wanted to experiment. Both the maintainer and the battery mount nicely on the stock battery tray.

If I understand correctly, I should be fine. The panels I am considering have an optimum voltage of 18 volts. Did I understand correctly?

I am looking forward to your results on the use of Solar panels...

I would say anything over 12 volts is good when cycling it. Depending on load that means you likely have not gotten into the bottom half of its capacity.
You want to make sure that battery gets a good charge when the car is home. The deeper you cycle the battery the quicker it will die.

As long as your solar panel can build over 18 OCV in normal day light it should be good for charging. I believe about 17 volts is the cut off for effective charging.

The solar panel I would like to build for my truck has a target voltage in the 18.5 to 19 ocv range. If it turns out to build between 19 or 20 ocv I wont be sad.
The under load target is 14.5v @ 5 amps.

Many Hondas - our Gen 6 ones included - have an alternator cutout circuit that activates under certain conditions. The purpose of this is to increase fuel economy. When the computer cuts out the alternator, the unassisted battery voltage is what you will see on your gauge or meter Typically it drops fairly rapidly to 12.5V, and then drops slowly towards 12.0 as you drive. In my experience, I'll end up bump-starting the car to regain speed before it gets down to 12.0. After an engine restart it will run at 13.x for a few seconds, and then goes back into alt cut mode as long as all the conditions are met. I never learned yet, at what reduced battery voltage it goes back into full charging mode.

Conditions required for alternator cutout:
Battery not absorbing significant charge from the running alternator
- - That is, after an overnight sit and running the starter motor, the battery will absorb charge due to some charge depletion. The computer will detect the load on alternator and will NOT cut the alternator till the battery charging load reduces, due to the battery now having been recharged.
Car not in fuel cut mode. If you go into a coast with engine engaged, it will run the alt. at full voltage. At least you get something out of that coast.
Speed not above 50 mph. Engine rpms don't matter, just road speed.
Very low electrical load. Headlights on will take you out of alt-cut mode. Small corner lights only, fan on 1 or 2 (maybe), or radio (assuming no moster amp +/or subwoofers) will not take you out of alt-cut mode. Power windows will take it out of alt-cut mode. In all cases, when you stop using the device, alt-cut mode will come back within a second or two, as long as all other conditions are met.
Engine idling? I can't recall whether idling kicks it out of fuel cut mode or not. Easy enough to test that though, now that you know the rest of the logic map for this.

This is managed by a device known as the "ELD", the Electrical Load Detector. It's in the under hood fuse box, a low flat panel that doesn't look like a removable relay or fuse. Not really intended to be messed with, I'm told. I think if it goes bad you replace the whole fuse box. Failure mode is that voltage goes haywire, high and low voltage levels. not under true control.

Well I cycled it very deeply today with no sign of engine trouble. I drove 70-75 miles on a single charge (a lot of EOC time). As I neared home the voltage meter read 10.8 sometimes when the engine was on, but would jump back to 11.3 during EOC. I only did that to test max range. I do not intend to run the batt down like that often. I am optimistic that this mod will yield my highest tank yet, despite being deployed late in the tank. Will be fueling in two or three days and will know then.

Thanks, brucepick, for the tips about the alt... I wil check out my setup. I think this might be an HX advantage. My DX alt seemed always to be charging.

You might be on to something.

I have read that 10.8 is where you need to stop using the battery. I would up that to 11 volts even.

Is there any posibility you can put more solar power on your car?

Another good thing to know is the lower your system voltage goes the more amps out of your solar panel.
The panels I plan to build for my truck for example, the 6x6 cells I have should make a panel good for between 4 or 5 amps at 14.5 volts, but when the system voltage dropps off to 12 volts and less the amps from the panel should rise into the 5 to 6 amp range.
This is why I am wiring up those salvaged 0.4 amp float charging panels for 22.5 ocv, that way I get the whole 0.4 amps any time the sun is on them. I have tested them and they are good for holding battery voltage on 2 large truck batteries just over 13v.

This set up currently runs without the panels. Originally, I had thought I would install 100-120 watts on the roof, fill the whole area. That costs for the new, 2.5mm thick, cells I planned to buy. Now I am thinking minimum 20watts (min 1.5 amps) or maybe doubling that. Such a set up is more affordable and fits nicely on the aft portion of the roof. I may be able to aeromod the part that sticks up to look like one of those quasi, mini shark-fins. I want to run the radio or fan or both without radically depleting the battery on my daytime 22 mile commute.

This is very interesting. How are you wiring it up.

My salvaged panels that will be used for float charging are about 7.5 ocv at .4 amps each. I will just serries up 3 of them and wire them straight on to the batteries.
This mod will be very simple, I can do it all in an hour or so.

The high power panels will be glassless fiberglass backed panels custom made by me (they will be a much larger version of my float charger panels). I figure I will need about 40 cells in a stack. I can make the stack any size and shape I want as long as its some kind of square or rectangle.
I already have 1000 watts worth of raw 6x6 solar cells back home.
Edit:
I will likely wire up the high power panels with ether a charge controler or time delay. Any time the key is on and the sun is out the big panels will be sending power to the batteries. Just need to work out how I will cut power off.

The alternator disable its a great mod. I wouldn't have hit 70+ in the Paseo without it. Good luck with your best tank!

BTW, as a general rule, 11.5V is the lowest you should take your battery if you're planning on deep cycling it a lot. This ensures that it lasts more cycles than if you take it down lower.

It seems possibly to work
 

64.09mpg on my fill tonight is a new high--slightly better than 63.83 mpg on my last tank. But I only implemented this battery/alternator mod in the last 150 miles. For those last 150 miles the trip mpg was 64.5 (adjusted for UG over count). And half of that driving was in far less than ideal stop and go traffic that is highly unusual for me to have to deal with. I think the next tank could score at least 67 mpg and maybe 70 in my normal driving routine.

Great questions. I have an Odyssey PC625 deep cycle 13.2lbs battery. I bought it because it had slightly better reserve and cranking than the slightly heavier PC680. I made an odd choice, I know. Most guys go for bigger and heavier deep cycles. It is an experiment. I am willing to risk the cost of the battery.

Odyssey says 12.8 volts is full charge, that 12.5 is 75%, 12.2 is 50%, and 11.9 is 25%. "To get long life" from the battery, Odyssey says, it should be kept near full charge. Yesterday I ran it way down to 11 volts. Odyssey says a small charger like my 1.5 amp unit will not be able to fully recharge the battery after a full discharge. Was 11.0 a full discharge? Maybe not since the car was still running. What do you think?

Tips on how to get it back to a full charge if my charger can't do it tonight? Just reconnect the alt and idle the engine a while? Other options short of buying a bigger charger?

I'd much appreciate constructive suggestions. EDIT: AFTER CHARGING ALL NIGHT, 7pm until now, 438am, the battery is fully recharged, 100%+ ... so I may conclude that depletion to 11.0 was not full discharge.

If you have any doubt you didnt get a full charge it might be a good idea to run the alternator for part of the drive if you can.
An ampmeter could tell if the battery is drawing alternator power for charging. You could use an amp meter to see if the battery got charged at night. You could give the battery some alternator power and if it soaks up every amp the alt puts out then you know it didn't get charged the night before.
At that point about all you can do is run the alternator and lose some fuel milage or get a bigger charger.

How much did that battery cost?

I am thinking that little deep cycle battery could hold around a half kilo watt hour of use able capacity so its going to want quite a bit of power.
The battery may not be able to get a full charge off a normal 14.4 to 14.5 volt starting battery charging electrical system. I have never thought about charging hard cycled deep cycle battery on a normal car system.

I don't consider my 44lb starting batteries full until they are at 15.1 or 15.2 volts and drawing less than 2 amps. A smaller deep cycle like that should be full around 15.2 volts drawing under an amp.

charging well
 

Looks like you were writing the below while I was editing last night's post with the update that the battery reads 13.5 on the steering-column-mounted voltmeter. Since the manufacturer calls 12.8 full charge and recommends exceeding it by 8% regularly... I think I am there. But you had also commented earlier that my alt, when engaged, seemed to be behaving as if it never "thought" the battery was fully charged. I think you are right... what is the threshold at which the alt considers the battery too low. I'll bet anything below 12.8? So this deep cycle has design features that confuse the parameters of the alt's design? Interesting.

Anyway, you ask how much the battery cost: $114 and then about 12 more on post adapters. It was an odd choice... but if it works in my application, I'll be very happy for having risked the cash to have gotten the alt delete without sacrificing my weight-reduction goal of under 2000lbs.

The term "full charge" is a little tricky.
That means the voltage the battery retains after it has been sitting for 4-8 hours (depending on the mfgr.) with no loading or charging and at a temperature of 70-72'F.

"what is the threshold at which the alt considers the battery too low"
I can't say for sure how your system works, but it likely adhears to general starting battery charging guide lines. If I was going to make an alternator system that cycled on and off to save fuel I would set the on voltage for any time voltage dipped below 12 to 12.2 for more than a minute and off after maintaining 14.5 for about 10 minutes. Also have the alt run for at least several minutes on every start up.
Also your deep cycle battery should maintain higher voltage even as the battery power is consumed. For example lets say 12.4 volts on a starter battery could mean its 90% charged while 12.4 on a deep cycle could mean its 75% charged.
Unless your battery gets real warm it should never develope more than 12.8 volts on its own, after its had time to sit for a few hours.

I only get to connect my fancy over priced charger to starting batteries, I cant be sure what the fine details of deep cycle charging look like. I do know starting batteries will charge and discharge fast and hard enough to burn them selves up if the power or the load is there.
I am thinking that the deep cycle could trick the charging system on your car into believing the battery is charged when its not. Becaues I have herd that deep cycle batteries charge and discharge slower than starting batteries at the same voltage and on the same loads.
We know that Deep cycle charges run at higher voltage than a normal car alternator system. I believe the normal charging voltage on a starter batt charger (plug in unit) is the same as a deep cycle charger (a little over 15 volts), but the deep cycle chargers have an added feature. An "equalizing cycle", where they push the battery voltage up to 18 volts and cook the cells a little so they all get a chance to take on an equal amount of capacity. I would always use the equalizing cycle after other people ran the batteries in my tugs I use to take care of way down to the point where they would just crawl along.

Did you miss my earlier post?

~3.5v extra on the feedback line wold allow you to drain the deep cycle to 11v and then the alt would come online to maintain that charge level. (not charge the battery beyond that tho)

That would allow you to charge at home, and drive around without alt-load until the bat was almost empty, and still not risk draining the bat too much.

I did miss it
 

Yes I did, sorry. It's interesting too.

I have to admit that this is a bit beyond my familarity and knowledge right now. I'm still an "apprentice" perhaps a "journeyman" ... I have no "masterpieces" in me yet. Between this and your other post it seems to me you are recommending a second set of batteries to trick the alt into staying off until a designated voltage low is reached, triggering the alt to turn on and recharge all the batteries, then shut off. What size batteries are the NiMH ones you suggest and how would I identify the feedback line (yes, that's how green I am... I am unfamiliar with the feedback line). Thanks!

BTW, just got my best run to work yet, possibly 10% over my previous high even though that was on a warm summer day and this was a misty cool fall morning.
james

It is working quite well now. I installed a better battery maintainer yesterday and drove with it for the first full day today. It is 6amps (instead of 1.5) and designed for the deep cycle motorcycle battery I have adapted. Total weight for battery and maintainer is under 16lbs. I was able to run today without the alternator at all and still stay in good fully-charged down to about 60% capacity range. Current tank is likely a third straight new high MPG. It is at 64.4mpg this time (even though ambient temps are lower, nights are longer, and work has been requiring more early morning and after dark commuting). With the alternator totally off all the time now, I think this tank average may climb during the last 150 miles of my normal 600 mile range. I'll post a writeup of what I have done as soon as I can.

You are spinning the alternator but have cut exciter power right to get your gains correct?
If you picked up about 4% with the alt spinning at no load, that is good.
I think I could pick up 2 or 3 times that with out spinning the alternator in my truck. I expect big gains from a mod like this since the coolant pump is is now electricly driven.
35mpg with a huge truck could be possible.

That's right. The belt is still hooked-up. The electricals are disconnected (easily reinstalled in under 1 minute on the roadside if needed). I have seen quite a bit of discussion here about where the biggest gains come from, unbelting or just disconnecting the field wiring. I was persuaded by the guys arguing that the major source of drag comes from powering the alt., and that it is basically freewheeling otherwise. The powering of the magnetic field to
generate electricity produces most of the drag on the engine, they say.

If you look in my trip log, at the "Aliso" run, beginning in the last few days you will see evidence of what this mod seems to be doing in a high load driving situation. If the log and my estimates are reliable--and it's not really scientific, though quite methodical--I appear to get at least 10% gains on this run.

I have begun to believe that the gain is greater where the engine load is higher: on the freeway and climbing. My "Aliso" run has significant climbing, from near sea level to maybe 500 feet in maybe 5 miles.

There should be two wires from the alternator to the positive battery terminal. The thin one should be the feedback line.

can you please elaborate on how to do this fake input, I too am a total noob with electronics
thanks for your input:D

I have to try this for sure.
My salvaged float charger panels will go on first.
I have gotten word my trucks batteries I installed back in 2007 have likely bought it from sitting for the last 8 or 9 months. It could be time for optima deep cycle batteries.

Problem! :(

Although I'm hovering between 66.5 and 67.5 mpg and hardly use the alternator in daylight, I wonder if the battery mod is damaging the fuel system. Three or four times I have run the voltage down to under 12. Most of the time the voltage is between 12.1 and 12.7. Now I seem to have fuel flow problems. The car hesitates and testing suggests the hesitancy is not not dependent on battery voltage, bump-start fuel pressure loss, throttle position, load, engine temp, or engine speed. I know the fuel pump is electrical. Have I damaged my fuel pump with my weird alternator optional set-up?

I dont think you have. the reason is that you control DC motors with voltage and you control AC motors with hertz. so with the car being DC the pump will just run slower. the best way to check is to hook up a fuel pressure gauge on the fuel line and start the car. then do it again with the alternator hooked up. you should not see that much of a drop. check manual for the min-max fuel pressure for your ride.

They should be ok.
Most auto parts will operate with 8 or 9 volts DC.

You may need to change the fuel filter.

A loaded down DC motor is more likely to burn itself out running at a lower voltage. This is why electric motor systems have an undervolt alarm.

Many thanks guys. I have some reassurance, two more strategies to figure out my problem, and an excuse to buy a tool! I like it.

my question is why dont you go with two of the batteries and put them in parallel? cost?? maybe?

Not cost. But there were two reasons. First, a desire to fit the battery and its charger into the former battery's space in the car rather than relocating. Second, it is part of a general program of shaving weight in small measures across multiple places. That weight program has shaved nearly 250 lbs for a car that started at 2262lbs and that is driven heavily through pulse and glide techniques. This battery mod removed 12 pounds, without losing enough CCA to start the engine. It is a motorcycle battery, but my 1.59cc four cyl Civic is not all that much more than a motorcycle in some ways. That's especially true because I reduced electrical loads so much: CD player replaced with a battery-operated mp3 player, LED bulbs, HID headlamps. Night driving kills the battery still. And I have a little more I can do to reduce electrical load.

If I had two like batteries in-line, would the ability of my Odyssey 6 amp charger to fully recharge both batteries be reduced?

That battery charger would charge 2 deep cycles no problem as long as they had enough time.

I think maybe my alternator is dieing, and I wonder if the low voltage in the deep-cycle battery is a culprit. Sometimes, my voltmeter will show under 12volts and yet the alternator does NOT turn on. Other times the voltmeter shows momentary charging but then the alt appears to cut-out again. Looks like a bad alt maybe. I need to test it tomorrow. But I wonder if I over taxed the alt with this deep-cycle battery? Anybody had that experience?

You could only over tax your alternator if you allow it to charge up a severely discharged battery. However you are running a small capacity battery so that should pick up voltage faster causing the amp load on the alt.to decrease before it overheats. Who knows what exactly is going on?

I would put a regular battery in there, hook up an accurate voltmeter and go for a ride,monitoring the voltage. Turn on lights too to make sure it works.

If it's still acting up and all your connections are good you can call it an alternator. (maybe the PCM or ECM or ECU whatever Honda calls it can also manipulate the alt. but I would not go there yet)

I recently tested a voltmeter in my car and discovered weird things. (94 mazda protege 1.8L manual SOHC). When I take off with a cold engine,the alternator will not charge regardless of electrical load until I'm about 3-4 miles down the road! (morning or evening).
When it starts charging or coolant temp is beyond a certain point,I can do "regen" key off if I let the clutch out and the engine rpm hits at least about 2000 rpm the alt. WILL charge all the way down to very low rpms like 15 mph in 4th gear for example. Full output regardless of electrical loads! This is confirmed by three different volt meters and an ammeter. Weird!

Back to your case,your alternator might be just going out regardless of your mods!
Barna

I have also seen odd charging behavior by the ghost in the machine. But testing today at the battery posts with engine off, engine warm and idling, and engine idling with extra elect load showed normal operating ranges for the alternator. What could cause intermittent (one time only) high voltage DTCs in the coolant temp sensor, Electric Load Detector, O2 sensor, and MAP sensor each? Could the battery mod have effected the electric load detector in a way that is creating voltage spikes?

I don't think so (voltage spikes)!
However in general, low voltage conditions will cause all electronic equipment to go nuts.So knowing what you are doing,I would not pay much attention to the codes. If I wanted to diagnose them,I would reinstall the original battery,clear the codes and drive the car to see who's back if any codes come back!
Barna

Yeah you dont want to unhook the battery with the engine (and alternator) turning.
I have seen alternators put out over 20 volts when the battery was unhooked and with little to no load.
I had one alternator put out 48 volts at no load but it worked fine when installed into the electrical system.

Well... alternator passed test as did battery... but my ignition coil just failed a test, and an ICM/igniter "input test" from the manual also points to a failed coil. But here's the kicker: testing as soon as the coolant reached running temps indicated the coil was fine when I tested it a few weeks ago. The coil seems to fail only after the distributor gets hot after 15 mins or so of driving. Hahaha!! I am hoping this solves it, but I'll test the ICM and the spark itself once I have the coil replaced.

BTW, honda-tech's moderator RonJ@HT is guiding and querying me via a thread their. Great know-how and advice there. Hope this is the beginning of the end of my running problems...