Please advise: solar/grid charging questions

[California98Civic]

I need a new battery this week. I killed my current deep cycle battery thinking too much about its weight and not enough about its discharge capacity. It is rapidly weakening now, after just 6 months. I need advice.

I own this Odyssey charger: Odyssey Ultimizer 12 Volt 6 Amp Battery Charger: BatteryMart.com.

I want to buy this Odyssey battery: Odyssey PC1200 Battery. Odyssey says the battery needs a minimum current of 6amps, which mine supplies. I imagine it will take me longer to recharge the battery, which leads to my first question: (1) how long will it likely take to fully recharge the new battery with the the 6amp charger?

My Civic stock alt puts out as much as 70amps and my meter usually reads 14.3v max when charging. That's twenty amps higher than the largest charger Odyssey sells for its batteries and .2volts lower than Odyssey's recommended charging voltage, so my second question is (2) will my alt likely damage the battery?

Lastly and less urgently, I am planning in the future for 100w or 120w flexible monocrystalline solar cells on the roof. This set fits on the roof: 100W/18V Thin Film Monocrystalline Flexible Solar Panel - Portable-solar-panel,folding-solar-charger,flexible-solar-panel,Thin-film-solar-panel,Solar-garden-light,solar-landscape-light,LED light,solar-battery charger Chinese Manufacturer and Exporter. The last question then is (3) what charge controller would you recommend for the panel, given that the Odyssey battery likes to charge at 6+ amps and a minimum 14.5v?

[drmiller100]

looks like the battery is DESIGNED to be used in an automobile, so I'm sure it would be fine being charged by your Honda's alternator.

And, I'm sure it would be fine being charged by the solar panel as well. The solar panel is not much amperage really, but I guess every little bit helps.

Lets look at the numbers for a second.

14 volts at 70 amps is 1000 watts.
the solar panel is 100 watts PEAK.

Lets say your car uses 30 amps for computer, fuel pump, and all the stuff normally. That is about 1/2 horsepower.

Lets say your charging system is 50 percent effiicent, so that means you are saving 1 horsepower.

For every hour of driving, that means you are using one horsepower hour, which is 2544 btus of energy. Gasoline has 110,000 btus, engines are about 24 percent efficient.

So, each hour you don't run your alternator you save 1/10 of a gallon of gasoline.

Lets say gasoline is 5 bucks a gallon, so that is 50 cents an hour.

How many hours per year do you drive? Lets say 20,000 miles, averaging 40 miles per hour, that is 500 hours, or 250 bucks per year.

[drmiller100]

I think you'd be money ahead to set up a relay to where the alternator only charges when the your foot is on the brake pedal, or when the voltage drops below some set number - maybe 12.0 or something.

[California98Civic]

Originally Posted by drmiller100

I think you'd be money ahead to set up a relay to where the alternator only charges when the your foot is on the brake pedal, or when the voltage drops below some set number - maybe 12.0 or something.

Thanks Dr. Miller for your point about the alt and the design of the battery. That's what I thought people would say, but I wanted confirmation. I understand about the relay you mention too. And I considered it. But I rarely use my brakes with the car running. I have an alt cutoff switch, partly thanks to your input. I want to run the alt very rarely if at all and charge from the grid and the sun. I figure it might be worth $120/year to me to run this way if I can learn to do it properly. I intend to drive this car for many years more (11 years already).

I'm not looking for "money ahead" from each mod. I am motivated by the learning and the experience and seek only to more or less break even on the mods/hypermiling in total, over time. Separately, learning to maintain and repair the car myself is part of the deal and saves me cash. Next to payments on a new used car, this is cheaper, more entertaining, and more interesting.

Anyone have a recommendation for a charge controller? I really need that. And how might I wire it alongside the grid plug-in supplied by the Odyssey on-board charger?

[Ryland]

First bit of advice from me is never buy a solar panel that has a 3-5 year life span with a one year warranty! standard warranty with PV panels is 25 years so anyone who only gives a year warranty is not expecting their product to last!

For a solar charge controller something pretty basic like Sunforce 60012 7 Amp Charge Controller, Solar Charge Controller | Toolfetch should work just fine, that is just one of the first ones that I found... or http://www.kencove.com/fence/solar+c...GoogleProducts is weather proof, but your charge controller should be inside a building out of the weather if possible, unless you were planing to put the PV panels on the car... if that is the case then you can take the rated output and cut it by 1/3 to 1/2 because it's most likely going to be laying flat getting 1/3 to 1/2 of the energy/sun, because unless you live on the equator the sun is never straight up.

I've never put an amp meter on an alternator but my alternator on my Honda Civic I think has a 40 or 50 amp fuse, after all you want a lower amperage fuse then what the alternator is going to burn out at and I suspect that at just over 70amps your alternator is going to start to smoke and burn up.

[oil pan 4]

I am considering using a morning star controller and a time delay shutoff to solar charge LiFePO4 batteries. The morning star charge controllers are all set up for solar charging deep cycle lead acid batteries.

[California98Civic]

Originally Posted by Ryland

For a solar charge controller something pretty basic like Sunforce 60012 7 Amp Charge Controller, Solar Charge Controller | Toolfetch should work just fine, that is just one of the first ones that I found... or Solar Charge Controller - 10 amp Programmable is weather proof, but your charge controller should be inside a building out of the weather if possible, unless you were planing to put the PV panels on the car... if that is the case then you can take the rated output and cut it by 1/3 to 1/2 because it's most likely going to be laying flat getting 1/3 to 1/2 of the energy/sun, because unless you live on the equator the sun is never straight up.

The kencove manual shows that their controller can be programed for three stage charging according to the type of battery, sealed, gel, etc... That's interesting. Even though it's not programmable, probably the Sunforce controller does some form of three stage charging too, correct?

Do you really think I'll only get a third of the rated output from a solar panel on the roof of my car? I mean, it would depend on time of day, right? In the winter, weaker output all day, but in the summer, there should be several hours of high sunlight. Parking the car at work all day would probably fully recharge a lightly discharged battery, no?

[hawk2100n]

Originally Posted by California98Civic

The kencove manual shows that their controller can be programed for three stage charging according to the type of battery, sealed, gel, etc... That's interesting. Even though it's not programmable, probably the Sunforce controller does some form of three stage charging too, correct?

Do you really think I'll only get a third of the rated output from a solar panel on the roof of my car? I mean, it would depend on time of day, right? In the winter, weaker output all day, but in the summer, there should be several hours of high sunlight. Parking the car at work all day would probably fully recharge a lightly discharged battery, no?

1/2 to 1/3 of rated output on the solar panel is about right. You are fighting physics with it mounted to the roof, seeing that the roof is slightly curved and not normal to the sun's rays. The output of the panel can be mapped as a the cosine of the angle of the panel to the sun's rays. 0 deg is head on and full output with it moving towards 0 current as you tilt it away. A lot of time the sun wouldn't get higher than 45 degrees which is .707.

Can you charge the battery with less than 6 amps? Would a trickle charge hurt it? If no then go for it!

[Ryland]

Originally Posted by California98Civic

Do you really think I'll only get a third of the rated output from a solar panel on the roof of my car? I mean, it would depend on time of day, right? In the winter, weaker output all day, but in the summer, there should be several hours of high sunlight. Parking the car at work all day would probably fully recharge a lightly discharged battery, no?

To get the full out put from a solar panel you have to point it at the sun, the sun is not straight up! a 45 degree angle facing south is a decent compromise but if you can adjust the angle for the seasons then you will see an increase in your output as well, with a tracker that fallows the sun over the course of the day you tend to see an increase in your output by about 30% over not having a tracker, if you can change the angle of the panels over the course of the season you again, see an increase in output, lay the panels flat, put them away from the sun or partly shade them and you might still see an output but no where near the rated output.
This is why you don't see electric car makers putting solar panels on the vehicle, but instead say to put them on the roof of your house, that and they should last 50+ years on the roof of your house, your car is not going to be around that long.

[oil pan 4]

Originally Posted by hawk2100n

1/2 to 1/3 of rated output on the solar panel is about right. You are fighting physics with it mounted to the roof, seeing that the roof is slightly curved and not normal to the sun's rays. The output of the panel can be mapped as a the cosine of the angle of the panel to the sun's rays. 0 deg is head on and full output with it moving towards 0 current as you tilt it away. A lot of time the sun wouldn't get higher than 45 degrees which is .707.

That is why I use 22+ volts (panel in sun with no load) to charge a 12 volt battery.
Normally 17 to 18 volts (panel in sun with no load) are used.