Upgrading brings questions

damon
damon Registered Users Posts: 11 ✭
in Off Grid Solar & Battery Systems #1
Hi everyone,

I have been living on a sailboat and sailing in Central & South America for seven years. I have two Kyrocera 120w panels and two Kyrocera 130w panels for a total of 500 watts. These are wired in series to the Outback MX60 charge controller and stepped down for my 12 volt system. I also have a Honda eu2000i generator for running a battery charger when its necessary. The rest of my system is changing.

Batteries - Currently a single bank of six Trojan T105 batteries wired for 12vdc totaling 645 amp hours that are four and a half years old. Always watered and never discharged more than 50%. I'm happy with the life I got out of them. One battery shorted (once cell shorted) two weeks ago so I'm actually running off four T105s right now. I should note that the Trojans appear to be bulging a little but I'm not sure how I could have over charged, at least not aware of how right now. New batteries are on order and will be shipped to me here in Panama in about three weeks. They are six Rolls EHW220 six volt batteries so I will have a bank of 660 amp hours.

I sold my Freedom 15 inverter charger (1500w/75amp) and my Link 2000 battery monitor and have just finished installing a Magnum MS2012 inverter charger (2000w/100amp) and Magnum's RC50 remote panel. I decided to change out the Freedom unit as it's max output on my Honda generator was 60 amps, with the Magnum I got 92 but have it turned down to 70 amps max out for the new batteries. The Magnum seems to be working well and does put less of a load on the Honda. One thing I do not like about the Magnum is that if it is turned on and sees more than 12.8vdc on the batteries it will just go straight into float mode. I'm not sure I like this. If it is say 2pm and if my solar panels are putting in 25 amps but the batteries are only at 13 vdc, I may want to run the generator and the Magnum to charge the batteries up, but because the solar panels put a voltage greater than 12.8 on the battery I can't charge using both solar and the Magnum. So I guess if I want to charge during the day with the Magnum I'll have to turn off my panels, energy wasted (we don't run the generator at night so as to keep the anchorage quiet).

An Outback Mate2 and Flexnet DC has been ordered and will be my new battery monitoring system, the Mate2 will also connect to the Outback MX60 via a hub. The Link 2000 works fine but I like the array of information available on the Flexnet such as time since the batteries were last full, hi/low for the day, 128 day history and so on. I also like that I can have up to three shunts so I'll be able to monitor the panels, battery charger and loads independently as well as combined as a whole system.

The Rolls batteries are expensive and I hope to do what is appropriate to make sure I can get 7 to 10 years (or more) out of them. So here are my questions;

Rolls recommends that the maximum bulk/absorption current be 15% of the six hour capacity. The six hour rating for the EHW220 is 163 so for my bank that would total 489 and the 15% rate for that would be 73.5 amps. I can adjust my Magnum to 70 or 80 amps. But other sources say that charging at C10 or C15 is okay, that would be 66 to 82 amps. I'm thinking that I should probably follow the manufacturer's recommendation and stick with a maximum of 70 amps. What do you think?

For absorption time Rolls recommends the formula 0.42*C20/I where I is the average absorption current. So that would be about 5.5 hours. But Magnum recommends 2 hours of absorption time. I know that the Rolls have thicker plates and will probably need to be charged a bit longer but 3.5 hours is a big spread between what Rolls recommends and what Magnum recommends. I don't want to under charge but I don't want to over charge either.

The average battery temperature on the boat here in Panama is about 89 degrees F and I will follow Roll's recommended bulk/absorption voltage of 14.1 and float of 13.1 for the higher temperature here.

Oh, I have my MX60 set at 14.2 for bulk/absorb and 13.2 for float. No BTS on the MX60. Right now there is no history showing the MX60 was ever in float mode but that seems to make sense as I use more than I replenish until I turn on the battery charger.

I typically consume about 140 amps per day. My solar panels will produce between 90 to 150 amps per day depending on cloud coverage but I would say a good average this time of year is 100 amps and with inefficiency that probably means about 85 amps back into the battery so my true consumption per day would be about 55 amps. By day three I am usually down 150 to 175 amps and will turn on my Honda to power the Magnum and recharge to 80 or 90 percent. Once a month I recharge to 100%. If I"m motoring my 70 amp alternator does a good job charging and depending how far I'm going I can be at 100% by the time I set anchor. From January to May my panels will produce 150 amps and my wind generator will produce about 75 amps per day, so I always have a surplus.

I have a new hyrdometer shipping my new batteries too (old one broke).

Anyway, does all this sound right as far as settings go? Any suggestions on changes to ensure a good long battery life?

Thanks,

Damon
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Upgrading brings questions

    If you want opinions you can have mine. It's free, and worth every penny of the price. Canadian.

    I think you're making a big mistake not having a remote temp sensor for the MX60. I also think you don't have enough panels for the Trojans, and they probably would still be going if you had. There's not enough panels for the Surrettes either. You spend a lot of time running the gen? Do you really need that big a battery bank?

    Buying a MATE & such to monitor the batteries is an expensive solution if you're not using an Outback inverter to make full use of the integrating possibilities.

    I wouldn't have bought the Surrettes. They've gone off my "good list" of late due to several problems with them shipping dead units.

    I think you'll like the Magnum inverter, though.

    I also think you should have asked before you spent the money. :roll:
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  • damon
    damon Registered Users Posts: 11 ✭
    #3
    Re: Upgrading brings questions

    Thanks for the feed back.

    I didn't put a BTS on the MX60 because at peak sun I will have about 30 amps coming from the charge controller but the voltage usually never exceeds 13.6 vdc. Using a thermal temperature gun the batteries are still at 89 degrees F so I didn't think it was necessary. The Outback dealer in David, Panama has one in stock so I might have him add it to my order.

    The reason I didn't get the FX2012MT is two fold. First it was $3200 from the only Outback dealer here in Panama. All his prices are well over Outback's suggested retail and I just wasn't going to pay that price. The Magnum 2012 was $1525, tax and shipping included from the dealer in Panama City. The other reason is that the installation location wouldn't accommodate the physical size of the Outback, no problem with the Magnum.

    I wanted the Mate2 and Flexnet DC to monitor the battery bank. These items I didn't think were too expensive considering I could bring them back from the states in my luggage. I do like how much more sophisticated it is over the Link2000 I had. Oh and the sale of the Link 2000 here in Panama actually covered the cost of the Mate2 and Flexnet, not a bad trade.

    We went with the Rolls batteries because they were actually cheaper than the Trojans and because of their rated life cycles. The Trojans T105s can be had here locally in Panama but are about $280 each plus tax and shipping to Bocas del Toro. The Rolls EHW220 was $240 each including shipping from Miami, duties and customs. Had the Trojans been cheaper I would have gone that way but since I could wait a few weeks the Rolls sounded like a good deal.

    I'm happy with my 500 watts though I agree that it might be too small for a 600 AH battery bank. But unfortunately one of the limitations of a small boat is space. If I could find a place for just one more Kyrocera 130 I would go buy it tomorrow. We don't run our Honda very often. We do have a wind generator but I didn't include that in my first post as wind is not always consistent.

    When the trade winds are blowing and the sun is shining we can go weeks on end and sometimes months without having to run the Honda for the battery charger. From January to April or May we can easily produce over 200 amp hours a day, well over our consumption of 140. Its a nice feeling. From October to the end of December it is rainy season and very cloudy but a little bit of rain. During this time we can go three days, sometimes four before having to run the Honda. If we're moving around between anchorages we'll motor if quarters are tight, this will replace our Honda running. The rest of the year we have decent sun and can go four to seven days before having to charge up with the Honda.

    All in all I don't think we're too bad off. But again I agree, if I could get just a wee bit more solar. Maybe one day sails and canvas will have impregnated solar cells.

    What I'm most interested in is charge times an voltages based on my usage, ambient temperatures of 85 to 90 degrees and any other feed back. Again, thanks for your input!!

    Damon
    www.sv-bruadair.blogspot.com
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  • damon
    damon Registered Users Posts: 11 ✭
    #4
    Re: Upgrading brings questions

    After some more thought I think you're right about the RTS for the MX60. There are those four or five months out of the year where do reach absorption voltage and so it should be temperature compensated. Thanks for the suggestion, will put one on order.


    Damon
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #5
    Re: Upgrading brings questions

    In my (novice) opinion getting the absorption time wrong is choosing between the lesser of two evils:
    1. Too long and you heat the batteries up unnecessarily, increasing watering demand and reducing life expectancy slightly. This is one reason why a BTS is so essential.
    2. Too short and you chronically undercharge them = sulfation death in short order.

    Of the two, I'd choose 1 as the effects on battery life are much less than 2. So you could choose a longish absorb time, say 4 hours, then monitor the charge on an average day and time how long it takes for the batteries SG to stop rising. Add 20 minutes to this as a safety margin and set it as your new absorb.

    If Rolls recommend 73A as the maximum allowed charging current for the batt, then you could set your charger at anything less than that. Remember it's the maximum, you don't have to reach or even approach it.

    Again, this is my novice opinion, but your charging regime of constant charging to 80-90%, but never reaching 100% except once a month is an issue. I would try and reach 100% at least once a week!

    How often do you perform EQ charges?
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  • damon
    damon Registered Users Posts: 11 ✭
    #6
    Re: Upgrading brings questions
    stephendv wrote: »
    Of the two, I'd choose 1 as the effects on battery life are much less than 2. So you could choose a longish absorb time, say 4 hours, then monitor the charge on an average day and time how long it takes for the batteries SG to stop rising. Add 20 minutes to this as a safety margin and set it as your new absorb.

    Excellent suggestion

    stephendv wrote: »
    If Rolls recommend 73A as the maximum allowed charging current for the batt, then you could set your charger at anything less than that. Remember it's the maximum, you don't have to reach or even approach it.

    Agreed
    stephendv wrote: »
    Again, this is my novice opinion, but your charging regime of constant charging to 80-90%, but never reaching 100% except once a month is an issue. I would try and reach 100% at least once a week!

    Rolls recommends (in their owner's manual) that for batteries being operated in the 50 to 80% range that they be charged to 100% at least once a month. I agree that more often would be better. We don't sit in one spot at anchor very often and move around when we can. That usually involves some motoring especially in and around so many reefs so while not a planned event we probably do charge to 100% more often than once a month. The reason I stated once a month is that is a planned event, usually on the first of each month.
    stephendv wrote: »
    How often do you perform EQ charges?

    With the Trojan T105s we equalized every four to six weeks as per their recommendation based on our usage. We have friends on another sailboat that bought their T105s the same time we bought outs (same pallet). The equalized their T105s maybe once a year. They got less life and less performance.

    Thanks again for your input.
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