Various little questions...

RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
So it's (almost) the start of another month and I'm looking at my next round of toys for the solar system. :D I had a few questions that perhaps some here can answer - or at least give their opinion! ;)

First, I'm going to buy a battery monitor. I've heard all the raves about the Trimetric, but wondered if that's *the* one to get, or just one of the more affordable ones? I am also considering the Xantrex LinkLITE, and perhaps / possibly the Outback Power Flexnet system monitor (since I have an Outback FM-80, and will probably keep going with them as I expand). But is the Outback one usable standalone, or does it require the Mate? (I don't have that yet.) At some point I am going to work on computer monitoring everything (another hobby - I do building automation systems for a living) so the Mate will eventually be on the list...

Second, what about the battery caps? I have Trojan T-105+ batteries with the flip-top caps. I see NAWS has water-misers and hydro-caps, and have read the difference between the two. On the one hand, less watering sounds great, but on the other hand my bank has been in for a couple months now, and I just checked the levels and they are the same as they were when I got them! I'm not pushing a ton of amps into them (indeed, the highest charge rate I can manage is 55A from the AC charger, and I have a 660AH bank - so a little low perhaps anyway) so just how much water would those caps save? And would I see enough benefit from the hydro-caps to justify the cost? (My initial interest in those was the reduction - elimination?!? - of hydrogen gas. The battery bank is in my garage. But then you have to take them off for equalization...)

I'm also considering two more panels. I currently have two KD135GX-LP panels, 135W STC. On a sunny day (which, naturally, have been sparse since I put them up!) they *handily* recharge the bank well before the end of the day. There have only been a few days other than totally overcast ones that I could have used the extra capacity as far as completing absorption. But I keep comparing the bank size (660AH) with charge rate (17A typical, 20A max) and keep reading here and elsewhere that I really ought to be up closer to 66A to be "right". is there really a problem with a charge rate that's a low percentage of capacity, as long as it manages to charge the bank? (I know equalization could be an issue - the plan there is to charge the bank with the AC charger, then let the panels equalize.)

I'm almost certain to eventually get the extra panels (have space on the racks already, just waiting for them). But I'm wondering if I'd be better off with them sooner rather than later...

A note to describe my system, it's more of a "hobby" system. I'm a ham radio operator, so it's configured 12V and primarily just runs the ham bench and associated lights/computers. The house is on the grid, this system is standalone. (It also has an Air Breeze turbine that provides more entertainment to me than power to the batteries - my house is in a bad location for wind! - but it does provide a little extra charging.)


  • icarusicarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Various little questions...

    I love my Tri-metric,,, it gives me most of the info I need at a reasonable cost.

    With the charge currents you have,,, I think your water usage is not going to be enough of an issue to warrant special caps,,, although they would be nice.

    As for your charge rate,,, 5-13% is a recommended average, but if you are not drawing down very much,, being a bit under isn't going to hurt,, as long as you keep the batteries full every couple of days.

    More panels are always welcome,,, it seems that there is always a use for more. (If anyone has extras feel free to send them to me).

    As a hobby system, you get the great chance to play with various configurations and changes and see what works for you and what doesn't.

    Good luck,

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Various little questions...

    that's a nicely sized battery bank for ham.:D i can't comment on the battery caps as i have no experience with them. i'm sure others will comment on that aspect as they have in the past and you could also search the forum on that subject.
    you say you charge with 55a into 660ah and that's good. 55/660=8.33% charge rate and will do fine for the bulk charge. the pvs will deliver at peak 15.26a and represents a 2.31% charge rate by itself and will be fine for topping off the charge. even running the 2 together would give 70.26a and dividing that into the 660ah bank gives about a 10.65% rate of charge so no overcharge rate will be present with both charge sources going at the same time. i don't think i could have done any better in selecting components to work optimally. any additional pvs could help in the base charge for when no utility ac is present 2% is quite low, but watch the % when both sources are present at the same time. 3 135s would give a max of 22.89a. with the 55a from the charger that gives 77.89a and dividing by the 660ah battery bank is still under the 13% top end rate as it is at 11.8%. a 4th pv will still be safe too at 12.96% and may be ideal for you as the charge from 4 of those pvs will be 30.52a and will represent a 4.62% charge rate. it is under the 5% we usually specify, but it can bulk charge the bank given more time whereas 2 will probably not do much for a bulk charge.
    btw, the higher charge rates could boil the electrolyte more making more maintenance, but i don't forsee any nightmares in not having special caps. up to you.
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Various little questions...

    Actually, I don't normally run the AC charger. It's only used if it's heavily overcast so the panels aren't doing anything. The real reason I bought it is to be able to charge the bank from my generator (Honda EU2000i) should the power go out and I'm relying on the bank for more than usual (lighting, refrigerator). That's about the most the generator can handle continuously.

    The two panels are able to bring the batteries back up to full - switching to float charge - all by themselves at this point. I've been pretty careful with the loads, though, to make sure I don't draw the batteries down much. Most days the FM80 shows 60-65AH total, the first day I had it running it managed 100AH!

    Icarus, being able to play is exactly why I went with the setup I have. Grid tie sure is a cool-sounding idea, even now I could make use of the "wasted" power after the bank gets charged by letting other things in the house use the surplus. But I figure it wouldn't be near as much fun since I could just randomly mix-n-match and try things out thanks to the regulations and inspection requirements...

    Niel, it is definitely a nice size for ham use. I was surprised to find I already have a use for that much too. I am also a scanner buff, so have a couple radios that stay on 24x7 plus a small computer that logs weather station data, serves up that info, and will eventually be logging the solar system. It was a bit surprising the first time I added up total AH for even a relatively small 24x7 load - it adds up quick!
  • RandomJoeRandomJoe Solar Expert Posts: 472 ✭✭✭
    Re: Various little questions...

    Well, the computer geek in me took control! :p

    After much more reading, and finding the communications protocol manual for the Outback Mate, I just had to have it! ;) So I got the Outback gear - DC monitor, three shunts and the Mate - which took most of my budget for this round of toys and meant I wasn't getting two more panels. But I did manage to squeeze in ONE more!

    I look forward to having some fun writing a program (yet another hobby of mine...) to log and manipulate data from the Mate. In fact, that one capability was largely what caused me to go with Outback. I had already chosen another system some time ago, until I read they wouldn't release the protocol to talk to their gear. It's nice to not just find the specs but a whole manual available on Outback's website! :cool:
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