PV marine battery charging

System

WOW !!! :-D What a great site !!! Soooo much knowledge here that I believe could help solve my problem.

I have a fishing boat with trolling motor docked where there is no 110V. I try not to run my Lifeline AGM GPL-24T, 80ah trolling battery down more than 50% but it sometimes happens. It's a real PITA to pull it and haul it both ways for recharging after each trip! :x

From what I've read, I shouldn't expect much, if any, recharging of the battery when linked from the outboard's stator(alternator) since it is intended for maintenance of the starting battery only. Please help me design a PV system to be permanently mounted on a fixed southern facing, unshaded piling. I'd like to recharge to 100%, if possible, from 40ah draw down, as quickly as possible. I have sheltered under console space to mount a controller to prevent overcharge with total cable run of less than 20 feet. This is located in Wilmington NC USA.

This should be a snap for you guys but is a total 'thought I'd ask BEFORE I got myself in trouble" deal for me. Please recommend any sizes, suppliers and components you recommend. Thanks in advance for making this easy !!!!

Roderick

Re: PV marine battery charging

I'm not a battery expert, but there are folks here who definitely are.

Some questions: how long are you willing to wait to recharge your battery? There could be a lot of money to be saved if you are willing to charge it at a minimum rate. It hurts me to think of trying to charge such a battery at a maximum rate, and have the solar power wasted for the rest of the time.

Also, are there any security concerns at the site? Could you have a spare battery charging at the dock, ready to swap in, or is even that a pain? Any concerns about theft of solar panels?

Oh, and I know you said Marine, but is the location going to be exposed to salt spray (do glass windows turn white if not washed)?

System2

Re: PV marine battery charging

I hooked my friend up with some Hawker 6vf11 used batteries from the phone company for $42 each. They were $700 each new and are sealed AGM type and work Great! He puts it on a dolly and puts it in his car to charge it on the way back home with a charge controller just to be safe. These are rated @ 100 AH @ the 8 hour rate. They could be easily charged by solar too. There are more of these available from the local phone company here in Kansas City.

Let us know,

Skip

niel

Re: PV marine battery charging

i'm assuming the battery is at 50% dod when you say 40amps discharged so that would make it an 80ah battery. now this is a quality battery and can take an amp for an amp as told to me by the company. i doubt that you want to feed it 80amps or would have the room for enough pvs to deliver 80amps. having the room for mounting very many pvs and the cost of the pvs are the dominant determining factors for you. we like to tell everybody that a 5% rate of charge is good minimumly. that would be 5%x80ah=4amps. add some extra for losses and you could windup with 5amps as a good minimum goal for your charge rate. this is a 20hr charge rate so you may want to get 10amps or even 20amps to speed up the charge. those rates would be about 10hrs and 5hrs respectively. you can look over the panels our host sells and look for the 12v panels as those for other voltages will need an mppt downconverting controller to handle that higher voltage. the typical vmp rating of the 12v panels will be anywhere from 16.5v to 17.6v so if in doubt look that spec up. if the panel, which we call a pv, is over 130w it will be too high of a voltage spec. any pwm controller will work for you, but we also like to recommend that you obtain one that can use a battery temperature sensor and buy the sensor at the same time you get the controller. this will compensate for temperature variations and give your battery a proper charge. i hope this generalization helps you. any more questions feel free to ask.

crewzer

Re: PV marine battery charging

I have a fishing boat with trolling motor docked where there is no 110V. I try not to run my Lifeline AGM GPL-24T, 80ah trolling battery down more than 50% but it sometimes happens….

Please help me design a PV system to be permanently mounted on a fixed southern facing, unshaded piling. I'd like to recharge to 100%, if possible, from 40ah draw down, as quickly as possible. I have sheltered under console space to mount a controller to prevent overcharge with total cable run of less than 20 feet. This is located in Wilmington NC USA.

Scalez,

Correctly recharging an AGM battery such as your Lifeline requires a fair amount of time when the charger is in its absorb stage (three to four hours when starting from a 50% SOC), so, while “as quickly as possible” can influence the time spent in the bulk charging stage, the overall total will be anywhere from five to eight hours.

I’ll spare you all of the details, but I’ve no doubt that I can make the case for buying another 80 Ah battery and a “small” charging system, and then alternating batteries by using one while the other charges at the dock. A large system will cost a lot more money and not significantly reduce the required recharge period.

Assuming a south-facing panel tilted up ~19-20 degrees (latitude – 15 degrees), Wilmington’s average insolation from late spring, through the summer and into early fall is the equivalent of 5+ hours/day of “full" Sun. Sunny days will be better, cloudy days worse.

See: http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/13748.txt

This suggests you’ll need a PV module rated @ ~17 V x 8 A = 136 W STC. You might be able to get by with a single 130 W module (i.e., Kyocera 130), but a pair of 85 W modules wired in parallel (170 W total) would probably be better (i.e., Kyocera 85’s)

See: http://store.solar-electric.com/kc-120.html
And: http://store.solar-electric.com/kysokc85wa12.html

The Morningstar SunSaver 10L or Prostar 15 charge controller will work with either of the module suggestions above.

See: http://www.morningstarcorp.com/
And: http://store.solar-electric.com/pros15solcha.html
And: http://store.solar-electric.com/ss-10l.html

You should be able to connect both batteries to this system to keep them charged up while you’re away. As mentioned, don’t overlook security concerns, and don’t forget fuses between the PV module and the controller, and between the controller and the battery!

HTH,
Jim / crewzer

System2

Re: PV marine battery charging

BINGO !!!!! :-D This is sooooooo cool ! I knew it would be an easy solution for you guys but it has taken awhile to find this site. I've posted this same sort of question to several marine and boating forums without nearly as much valuable response.

eargasm :The second battery option sounds very doable but the load is 12v and weight is a concern in all things related to boats. AGMs, even used, at less than $0.50/amp hour is incredible. Do any of the UPS phone banks use 12v batteries? Ya know of any in SE NC???

roderick: Sadly, theft is a concern everywhere today. In my case it would require considerable effort to steal a piling top mounted panel but the second battery could be a target tho, thankfully, I'm remote. The salt enviroment is not bad here but semi-annual maintenance or after storms would be required.

niel and crewzer: Great points! The single 85w with the PV j box mounted controller looks like the deal with a second battery. My only concern would be matching the recommended charge volts with the controller presets. :? Realistically I would only need the quick(1 day) recharge occassionally as I can't fish every day. When that was in the cards I could swap batteries at the dock!

Thanks to everyone !!! I beleive this puts me on the right track. The next question will be for a installation in the totally offgrid location of Bocas del Toro, Panama ! :-D

niel

Re: PV marine battery charging

scalez,
please reread this as the recommendation is for two 85w pvs and i agree with crewzer's statement.
"This suggests you’ll need a PV module rated @ ~17 V x 8 A = 136 W STC. You might be able to get by with a single 130 W module (i.e., Kyocera 130), but a pair of 85 W modules wired in parallel (170 W total) would probably be better (i.e., Kyocera 85’s)"

System2

Re: PV marine battery charging

I'm such a newbie at this!

niel : Well, duhhh! I guess it is a common newcomer's mistake but I did the dumbies mental leap to crewzer's 'small' charging system of the single 85w/4a pv with second battery. You already told me I needed 5a minimum for the 80ah battery.

Okay, so now it is obvious that my original post of 'as quickly as possible' would cost bunches in pv dollars. The 170w(double 85w) pv setup with mount looks like $1200 or more. We're now getting into the range of cost to run power to the dock without the monthly minimum. What would a 'small' charging system and longer charge time look like. The pv cost easily offsets the additional battery costs.

Also, please help me with the MPPT / PWM thing. Either way it would appear that we'd be getting only 14.2 - 14.4 v(the recommended charge voltage) x 8a = 114STC. Is that correct?

crewzer

Re: PV marine battery charging

scalez,

The 130 W system is the small system. Anything smaller would probably take more than an average day to recharge the 80 Ah battery.

MPPT controllers are not cost effective in small systems. Since PV voltage drops as the ambient temperature increases, there's often not much "extra" voltage available in the summer for an MPPT controller to convert to additional charging current. My recollection is that previous discussions had found that MPPT controllers become cost effective when the PV array size exceeds ~350 W STC.

STC specs are based on a lab test simulating a PV cell temperature of 25 C (77 F). For this occur in the real world, ambient temperature would have to be ~-10 C F (~14 F) -- something you'll likely never experience in Wilmington.

The absorb / PWM voltage from a PWM controller will be ~14.4 V when the battery is 77 F. Assuming good insolation and module alignment, the output current from the KC-130 will be a bit over 7 A. Coulombic efficiency (Ah out / Ah in) of AGM batteries is typically 98% or better, so the ~7 A (mid-day) from a "small" 130 W STC system should be able to meet your recharge requirement during an above average sunny day.

HTH,
Jim / crewzer