jrnymn7 wrote:
BFL13 wrote:
Read it and weep. No converter will do this. Some chargers will.
http://pdf.wholesalesolar.com/battery-folder/charging_instruction_2011_2.pdf
I have been using PM converters as chargers for a few years now. We are off grid at a seasonal site from mid-April to end Sep. What lets us do that is solar plus using the gen and charger as required when it is cloudy and solar can't keep up.
I modified my 100amper so instead of dropping to 13.6 as soon as it gets the batts to 14.6, it stays at 14.6. So it now is no good as a converter, but the trailer already has a perfectly good converter for when on shore power.
I did have some trouble with the 100amper blowing its in-rush thermistor but it turned out that was due to using it as a stand alone charger. I had rigged a set of heavy jumper cable clamps to it for connecting and it turns out you need to clamp on first, then start the unit. If that conks out your gen because it is not warmed up and you restart the PM right away after the gen is restarted, the PM will blow that thermistor from not waiting long enough for it to cool--maybe half an hour.
Anyway, once that all got sorted out, I really like my modified PM100 for a fast charger followed by solar the rest of the day. The solar controller is now the key to success where it can get the batts to 15v or so, which meets the battery spec.
If all you have when off grid is that un-modified PM75 you are always going to be in trouble. I recommend you leave it un-modified and get a VEC1093DBD to use as well. After the 75amper drops to 13.6, disconnect that and clamp on your 40amper VEC and let it finish the job. It goes to 14.8 ( and that is temp comp!)and stays there. If you stay out more than a couple weeks doing 50-90s, then you absolutely need solar, since after several 50-90s in a row your bank will have lost a bunch of capacity and may not even get you through one night anymore. Then you are stuck until you can get shore power and a few days to do a "recovery episode" so you can go off-grid again.
yes, it looks like solar is an absolute necessity for me, seeing as i boondock continuously for months at a time. as i have said, i very rarely have shore power at my disposal. and i have found the high voltage portables tend to boil my batteries, and do not kick into float mode, which is supposed to be the whole point of a "smart" charger, is it not?
so i find myself right back to having to figure out when the bank is fully charged, and i know of no other way than measuring the SG every time i charge... at least until i figure out my bank's specs. for even with the VEC1093DBD, will i be able to rely on it to tell me when the bank is truly full??? i've been using a "peak performance" 40amper (among others) and it has not met my needs, and i just can't imagine any other portable doing a better job.
the whole reason i went with the pm4b was the lower voltages, thinking this would be better for my batteries, but many here say that a higher voltage is better. in an effort to shorten charging time, i thought higher amps were the key, not higher voltage. and the fact that my batteries can sustain close to 12.8 v for weeks at a time when not in use tells me that a 13.6 v charge should suffice, provided the charge duration is ample... no pun intended :)
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Edit: the Vector chargers (now B&D) are not like the "others" They will not ever boil your battery. Yes they do not get to "true full" when first saying "FUL" That will be at about 97% SOC same as other chargers that are "automatic" and shut down by themselves. As soon as you see that FUL the first time-sometime later, it doesn't matter how long-push the Equalize button (poke a nail in the hole for that) and now let it run till ot says FUL again. Look Ma, no hands! :) Check SG. If not there, run that E again until it says FUL again. My batts get there (to baseline SG, my target) usually after two runs these days. (on shore power of course, no hope of doing this stuff on a gen in any decent timeframe)
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Smk is correct in that with your charger you get to near 80% SOC by the time it drops to 13.6 so shut it down then if on gen. That leaves you doing 50-80s which is ok as long as you don't need that extra 10% to get through till next day. 50-80s is often seen in how- to- do- it blurbs as a recommended way to do a few days off grid. Agreed. It takes another hour or so of gen time to do that 80-90, so it is foolish to not stop at 80 if you don't need to go to 90.
You just have to get it into your head that the batts need to get to 100% (means 15v or so) every so often, say every two weeks if being deep cycled and not fully recharged as when doing 50-80s or 50-90s.
OTOH it happens that if you are on solar and have the same daily AH use as when doing 50-90s you end up doing more like 80-97s instead daily as long as the sun shines ok. (There's the rub!) This operating zone of 80-97 is completely different in that now you can go for a long time without having to get to 100%.
Your progressive loss when doing 50-90s is horrendous, but now your progressive loss doing 80-97s is hardly any (but there is some---so still try to do 100% every two months at least--every month is better)
How can 80-97s (17%) be the same AH as 50-90s (40%) ? Aha! Solar! in the afternoon once the batteries are nearly charged the solar can run things above just for battery charging. So you can do some extra "free" AH without it counting against your 17%.
But now you say, how much solar do I need so my batts get charged in mid afternoon so I can take advantage of the free solar before sundown? Aha again! It can all be calculated to a fair approximation as long as you know:
-Your latitude
-Time of year
-Daily AH usage
-Size of battery bank in AH
And BTW you will ask, "Which solar controller can I get that will have adjustable set-points for Absorb and Float so I can get the batts to where I want in the daylight I have at that location at that time of year?"
Aha some more! :)
