batteries 4

Do yourself a favor and check out this website.

http://manmrk.net/tutorials/RV/phred/phredex.html

Some great information about batteries and 12v systems in easy to understand form. Phred has other "poop sheets" on the website on a myriad of other subjects including inverters. Good luck, and listen hard about the 6v "TRUE" deep cycles like the Trojan. As Phred says, best bang for the buck. I have used them for about 25 years.

Bob

sushidog wrote:

but it seems that charging them too slowly can hurt their life too.

I see that claim thrown around very infrequently; so infrequently that I personally find it suspect.

If true, I'm pretty sure that it would be the first battery type ever produced that suffered from being charged at a healthy rate but "too slow".

AGM types just recently made their way into the deep cycle market and I doubt there is enough real life experience to have evidence one way or the other. In "normal" automotive use, they typically last 7 years or more......so it might be a while before we get any real life experience with longevity.

You didn't miss a thing, Dakota98. I was merely suggesting that the OP could get the same amount of ahs (600 at 12v) by getting $510 worth of cheapo GC-2s, putting the savings into a reasonable solar charging system so he wouldn't have to wait a week between uses for his bank to recharge, but would always have freshly charged batteries waiting for use. Not only that, but the Lifelines he chose (or cheaper AGMs as I mentioned) would never recharge to capacity but would eventually degrade over time as AGMs (or even FLAs, for that matter) need more than the amperage that one 150 watt panel could supply. Great minds think alike. ;)

Chip

sushidog wrote:
You are correct, Dakota that a 150 watt panel is woefully inadequate. However 6 Sam's club GC-2 FLA golf cart batteries will produce 600 ah at 12v for only $510 or thereabouts. Now if AGM's were chosen the cost would be closer to what you suggested at around $1,400. Still, point taken.

For every 100ah in batteries the rule of thumb is about 100 watts of solar is needed. With the price of solar dropping, I'd use a little more than that to get the most out of expensive batteries.

Chip

Maybe I've missed something, but the OP stated that he was considering four Lifeline gpl-6ct batteries & according to what I found online they run in the neighborhood of $400 each.

You are correct, Dakota that a 150 watt panel is woefully inadequate. However 6 Sam's club GC-2 FLA golf cart batteries will produce 600 ah at 12v for only $510 or thereabouts. Now if AGM's were chosen the cost would be closer to what you suggested at around $1,400. Still, point taken.

For every 100ah in batteries the rule of thumb is about 100 watts of solar is needed. With the price of solar dropping, I'd use a little more than that to get the most out of expensive batteries.

Chip

sushidog wrote:

At 10 amps max. (assuming 5+ hrs of sunlight/day with flat mounted panels) a 150 watt panel can replace 50 amp/hrs/day. So if you had a 400 ah battery bank and discharged it to 50% in a single day, it would take at least 4 days of charging in perfect conditions, with no cloud or shade to recharge them. In the winter, or with partial cloud cover of real world conditions, we are looking at at least a 5-6 days recovery time when the batteries cannot be used. If a 600 ah bank is needed then it would extend the recharge time 50% more to 7-9 days. I don't think over a week of charging to replace the energy used in a single day would be acceptable performance to most folk, how about you?

And that's to just replenish the amps already used & without any load on the batteries during that time.

I can't grasp the concept of spending $1600 on batteries & maybe $200 or so on what appears to be an inadequate means to charge them.

Vulcan Rider wrote:

sushidog wrote:
150 watts of solar eliminates AGM type batteries as you won't have a high enough charge rate,

That depends on the average load and how much of the sunlight day there will be little or no load.

A solar array capable of delivering 10 amps would be more than adequate to maintain or recover the charge with AGMs......if they are not drained dead and enough time ensues.

The effective charging rate and necessary charging voltage is not THAT much different with AGMs. If it was, they would not be an appropriate choice for such a wide range of applications......and they ARE.

At 10 amps max. (assuming 5+ hrs of sunlight/day with flat mounted panels) a 150 watt panel can replace 50 amp/hrs/day. So if you had a 400 ah battery bank and discharged it to 50% in a single day, it would take at least 4 days of charging in perfect conditions, with no cloud or shade to recharge them. In the winter, or with partial cloud cover of real world conditions, we are looking at at least a 5-6 days recovery time when the batteries cannot be used. If a 600 ah bank is needed then it would extend the recharge time 50% more to 7-9 days. I don't think over a week of charging to replace the energy used in a single day would be acceptable performance to most folk, how about you?

According to the Concord Sun Extender AGM battery manual on page 19 it states: "For repetitive deep cycling applications (deeper than 50% DOD), chargers should have an output current of at least .2C (20 amps on a 100 AH battery). If the output current is less than this value, the cycle life of the battery can be negatively affected."
http://www.sunxtender.com/pdfs/Sun_Xtender_Battery_Technical_Manual.pdf

Trojan also uses the same .2C minimum. This means that the recommended charge rate for a 400 ah bank that is deep cycled (according to both Trojan and Concord) is 80 amps.

I don't remember where, but I seem to remember a .15C figure being bragged about from one AGM manufacturer. Still, that means that to deep cycle a 400 ah bank one would require at least a 60 amp charge rate for max battery life. Of course if your battery bank is shallow cycled (less than 30%) then much lower charging rates can be used. But why buy a deep cycle battery if you don't plan to deep cycle it?

I know AGMs can be charged 3 times faster than a typical FLA, but it seems that charging them too slowly can hurt their life too.

Chip

thanks people
i have initially decided (initially i say) on (4) lifeline gpl-6ct batteries - maintained occasionally (maybe a week at a time) by a folding 150w 10a solar generator by overlandsolar.com -- i tried to figure max load (even a fireplace i wouldn't be using in the woods) and i come up with a charge time of about 18 hrs. - i realize that my estimate on watt draw is not real life but where do you draw the line
am i crazy on my choices or what
thanks for the input

Also, remember when changing batteries you must replace all the batteries at the same time! If you have one "bad" battery and only replace it, the weakest battery left will bring all the others, including the new one down to its level! when purchasing batteries the ideal purchase would be batteries with sequential serial numbers, probably will not happen but try and get batteries manufactured in the same run. Good luck.

sushidog wrote:
150 watts of solar eliminates AGM type batteries as you won't have a high enough charge rate,

That depends on the average load and how much of the sunlight day there will be little or no load.

A solar array capable of delivering 10 amps would be more than adequate to maintain or recover the charge with AGMs......if they are not drained dead and enough time ensues.

The effective charging rate and necessary charging voltage is not THAT much different with AGMs. If it was, they would not be an appropriate choice for such a wide range of applications......and they ARE.