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12VDC or DC-AC inverter?

Discussion in 'On the Road' started by MW1CFN, Feb 18, 2018.

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  1. KC0LDH

    KC0LDH Premium Subscriber QRZ Page

    Do, MW1CFN can you provide some details?

    What mode are you intending- FM, SSB and digital modes each have their own duty cycles, and therefore challenges.

    Is this A W/E shack that has all week to recover, or daily use?

    What rig? Some may require more thought in regard to voltage drop.

    How far will the battery be from the rig?

    Do you have access to surplus equipment? This may make an otherwise silly choice, very appealing.

    Do you have other secondary objectives? For example, do you use your batterys for anything else that would make sense to consolidate?
  2. MW1CFN

    MW1CFN Ham Member QRZ Page

    Very grateful for the very detailed responses, which at least provides me with some relief that a superficially simple question about a 'common' set of technologies is not quite so simple to answer as many would make out. In fact, I wonder if anyone has written a book about amateur solar power from the perspectives of a supplemental and sole power source? The RSGB constantly complains of a lack of new texts and authors, and the rapid progress in this field would provide ample opportunity for regular new editions...

    The MPPT controller advice is very useful, and I plan to obtain one of those to replace an existing PWM unit shortly. I have a 100W mono panel which is going in this week, which was selected on the basis of fairly low visual intrusion and windage (the mount has to be simple and unobtrusive, as well as immune to large farm animal interest and >80mph winds!) I am sticking with a '12V' battery, although the appropriate selection of a battery is quite a balancing act in itself, given the spread of expected lifetime/price/Ah/chemistry/structure/guarantee/weight (I have to carry things across very boggy fields!)

    I expect I will only use a maximum of around 40W pep on SSB, often less, and around 8W on digital. It's not a very demanding set-up, and it will be interesting to see, especially, how the battery behaves over time.

    Thanks again!
    Last edited: Feb 20, 2018
  3. KC0LDH

    KC0LDH Premium Subscriber QRZ Page

    I would consider a Capacitor near the radio to stabilize the voltage drop. The capacitor would allow the SSB mode to modulate at High loads, with lots of short duration current available. Many Power adapters (up/down- AC-DC etc...) are not able to adapt that fast unless specifically designed for radio use. Many battery technology's have high impedance, and lots of voltage drop internal to the battery.
  4. KD0CAC

    KD0CAC Ham Member QRZ Page

    " and it will be interesting to see, especially, how the battery behaves over time. "

    This is a wrong headed thinking , any battery you choose to use !! has specifications - they are not capable of " choosing " .
    So what you will be seeing - through the battery is how well designed / or not the system you choose to put together performs .
    This is the number 1 test of a system how long the battery survives the owner / or keeps going past normal warranted life , as an example , my last Trojan L16's had an expected life of 4 yrs. in the floor sweeper they were designed for , running an RV trailer with air conditioning , furnace , micro-wave etc. , my batteries lasted more than 12 yrs.
  5. MW1CFN

    MW1CFN Ham Member QRZ Page

    Here we go. It's never long before the trolling starts.

    Smoking isn't bad for you. I mean, my grandad lived until he was 90, and smoked 50 a day.

    Congratulations on making the specifications of your battery (expected lifetime) extend by three times. Makes you wonder why they don't specify them for that long in the first place.

    Apparently, many companies will only honour a guarantee for a deep cycle battery if it has never been discharged by more than 20%. I think that may qualify as a misuse of the normal expectations a reasonable person would have of the term 'deep discharge' - and the very high prices commanded for many of them.
  6. KD0CAC

    KD0CAC Ham Member QRZ Page

    Pointing out a primary fault in your thinking process , is not trolling , hopefully you can use planning with specifications and out perform , thinking that inanimate objets have some choice / or ability to vary ;)
    Getting the life I got from my last battery bank was in the specifications , my design made it work ,
    a few points that were part of my plans [ within spec. / understanding of my system ] was to build so that my consumption never took the batteries below 60% discharge , higher amperage charge produced by enough panels , a fully programable charge controller - that required info on battery chemistry , amp hr rating etc. , then also having enough panels to allow the charge controller to balance the cells - over charging , and finally - more to save the labor & eliminate the fumes - catalytic caps that recover the water from the gases in the cells .
    Again , its all about enough info / spec.s to get the best performance for the dollar .
  7. K7JEM

    K7JEM Ham Member QRZ Page

    I think you misunderstand the use of the verb "behave". There doesn't have to be a choice involved, and it can be an inanimate object. If you look up the word in the dictionary you will see that a definition given is very close to the way it was used in the post you quoted:

    Definition of behave
    intransitive verb
    1 : to act, function, or react in a particular way
    • He behaves like a child.
    • testing how various metals behave under heat and pressure
    Since the battery can act, function, or react in some particular way, his use of the word "behave" is correct. And the definition doesn't specify that any choice is needed or involved, or that the subject has to be an animate object. The battery will certainly behave differently under any change of conditions, and could last from less than a year to more than a decade.
    MW1CFN likes this.
  8. AI5DH

    AI5DH Ham Member

    Well three times longer than Warranty is an exception and would require exceptional care. For the record Best Practice for off grid solar is 20% DOD per day or 5 day reserve capacity and for good reasons. To start you should never ever allow a FLA battery to go below 50% DOD, so in practice that gives you 2-1/2 to 3 day operation before you need to shut down and run your generator. 3 days covers your butt for cloudy spells. Batteries have two life spans. 1 is cycle life vs DOD, and Calendar life

    What really matters from a user POV is the Warranty tells you what you can expect. One of the best battery manufactures out there is Trojan battery. Trojan's battery warranty and cycle life vary greatly. Warranty periods run as low as 1 year. The T-105 is under Trojan's Signature Line an dis a 18 month warranty and 600 cycles to 50% DOD. Now here is a twist there is also a Trojan SSIG 06-225 which is a T-105 formulated for Solar Signature line and carries 2 year warranty with 1200 cycles @ 50% DOD. Yet another T-105 variant called a SPRE 06-255 formulated for the Solar Premium Renewable Energy and carries a 5 year warranty at 1800 cycles @ 50% DOD. Although there is no T-105 variant in Trojans Industrial line up, the very popular L16 in 2, 4, and 6 volt versions carry a full 10 year warranty at 3500 cycles @ 50% DOD.

    Point I am making is you get what you pay for. More importantly the care you give to your batteries. If you are in the habit of hammering your batteries with deep discharges or heavy discharge rates, your battery is going to give up long before the warranty expires or cycle life is reached.
    MW1CFN likes this.
  9. AI5DH

    AI5DH Ham Member

    That is nonsense. Size your battery and wiring correctly, and voltage is not a problem. Keep max discharge rate to C/8 or less, and size the wires to 3% voltage drop and there are no problems. If you have to resort to adding gimmicks to stabilize voltage means you have a poor design you are trying to fix with gimmicks and tricks.
    MW1CFN likes this.
  10. MW1CFN

    MW1CFN Ham Member QRZ Page

    Thanks for all the comments. Happy to report that a 70Ah deep cycle battery, cheap waterproof, second-hand PWM controller and a 100W panel (during operations) are performing very well as a get-me-going system in early spring.

    There has been minimal cost outlay, essentially zero RFI (very weak pulses during light level changes only - no anti-RFI measures yet implemented), and on SSB, the system is keeping up well in still weak, spring light.

    For times when the shack is not in use, the battery is switched out of the 100W panel and into a 10W panel that does a fine job for this purpose.

    Altogether, no complications at all. Particularly liked the resorting to ordinary meaning of words and reference to a dictionary. Just like in Court!


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