Please advise: solar/grid charging questions

[California98Civic]

Originally Posted by oil pan 4

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.

Okay thanks guys. Now I am learning something (I hope). I get the point about the angle of the sun and output. Maybe that's best. I want to change the house over to solar anyway. But this mod was for portability of a power source that was not the alternator. It is true that a mere trickle charge will likely damage my new battery. I don't want to go much under 6 amps.

Oil Pan 4: I don't understand how a 22+ volt open circuit panel would solve the problem of amperage, though maybe that's not the problem you're proposing to solve. When I run 24 volts and 100 watts through an Ohms law calculator I get amps at 4.166666666666667, which is still quite a lot under the 6 minimum I probably should guarantee (for the life of the new battery).

This seems like it would be a misguided project, and that the home panels are the better project.

[oil pan 4]

My little panels put out about .4 amps max, they keep the batteries in my truck nice and topped off. When I check the batteries they are usually sitting around 14 volts.
But I have 2 really big truck starting batteries to disapate that current.

I have never heard of problems from slow charging batteries.
If you charge them too slowly to the point where they don't get a full charge before using them again that would create problems.

[brucepick]

California98Civic,

If you get the Odyssey PC1200 battery it won't be supported by their 6A charger that you have. Their chargers page indicates you need at least the 25A charger. ODYSSEY Batteries - Chargers I spoke with Kathy at Odyssey several times; their batteries "like" higher amps and also a bit higher voltage than standard lead acid. You might be willing to wait for a charge to complete but the battery won't do as well, long term.

I really suggest you avoid lead acid and look into a LiFePO4 battery similar to what I got. The main reason is that with lead acid, you can only use 20% of the capacity if you don't want a short lifespan (for the battery). That turns a nice 50 AH battery into a not so nice 10AH battery.

With lithium, you can use 80% of capacity and still have about 2000 charge/discharge cycles. More if you discharge it less than that. So my 40AH battery can serve as a 32AH battery and that's pretty decent.

The only caution on that is that it's my Lithium's output is limited to 100A by the "PCM", protection circuit module. It might not be enough to power the starter. The 100A limit is just for battery protection. You do need the PCM if you don't have a full blown Battery Management System, to keep the cells balanced. Again, that's for longer battery lifespan. I got around the 100A limit by keeping the main old lead acid battery in the circuit, wired to the charger. Or you could have a bypass jumper going straight to the battery, eliminating the PCM. The PCM would still function normally but would let the starter have the juice it needs. The pack I got will actually handle 400A load, and even more short-term.

Good luck with it all,
Bruce

[California98Civic]

Originally Posted by brucepick

California98Civic,

If you get the Odyssey PC1200 battery it won't be supported by their 6A charger that you have. Their chargers page indicates you need at least the 25A charger. ODYSSEY Batteries - Chargers I spoke with Kathy at Odyssey several times; their batteries "like" higher amps and also a bit higher voltage than standard lead acid. You might be willing to wait for a charge to complete but the battery won't do as well, long term.

I hear you. I emailed and called and so far have not been in direct contact with Kathy. Not her fault, just stuff getting in the way. I did purchase the PC1200, and it should be here today. Last Sunday, the old battery suddenly took a turn for much worse and is collapsing completely. I need my car (it's my DD). So I couldn't afford to think about options any longer, though your ideas sound very interesting and I'm hoping to get to keep following your experience and progress. As for the charger, I have been on the fence about it. Odyssey's site designates a larger charger for the PC1200, but its descriptions of what the 25amp charger does and how it works and what the 6amp charger does and how it works are identical. The only difference seems to be the amperage, which leaves me with the sense that time and depth of discharge are the real factors that matter. I called again a while ago and left a message. But I figure if I only discharge this new battery 20% before recharging 10-14 hours each night, and if I hit the battery with a two engine-off DFCO 14.3 volt 30+ amp charging glides during my commute, I should get a full charge into it. I'll keep you posted on how Kathy answers my questions when I get to speak with her. If she confirms your concerns as affirmatively, I'll probably cave and get the bigger charger too.

Thanks as always! -j