Battery mod not working out?

[oil pan 4]

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.

[California98Civic]

Originally Posted by oil pan 4

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?

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.

Originally Posted by oil pan 4

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 is very interesting. How are you wiring it up.

[oil pan 4]

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.

[Daox]

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.

[California98Civic]

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.

Originally Posted by Old Tele man

...what "brand" deep-cycle battery are you using? And, what do *they* say about low-voltage "threshhold" under load? Typically, the manufacturer will specify a MAX-MIN cycling voltage that will optimize the battery "longivity/life."

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.

[oil pan 4]

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.

[California98Civic]

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.

Originally Posted by oil pan 4

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.

[oil pan 4]

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.

[jakobnev]

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.

[California98Civic]

Originally Posted by jakobnev

Did you miss my earlier post?

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

Originally Posted by jakobnev

~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)

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