CHARGERS ... rant for comments and advice. When I got my 29 there was two solar cell trickle chargers in the window which had ruined the old house battery. There was about 5 Amp Hours left out of the 80 it was born with. The starter battery was brand new because the solar cell trickle charger had killed it before the sale. I analyzed and recharged my batteries with a charger from Hobby King - they do 10A easily and will tell you all kinds of stuff about the battery. But they are not automatic and hauling out all the wires every time was irritating. So I went and got the cheapest Genius GEN2 Mini charger (2x4A) and put it in. The idea was that it would charge the batteries overnight from a reasonable discharge of perhaps 40Ah. That ought to keep the brand new AGM battery healthy for a long time It works. When I connect the shore power I get two red lamps and after a short while the starter battery lamp goes green - and next day the AGM is always green. I have LED light in the cabin, so the 4A top up charge does wonders when I am just puttering in the boat at shore power. Now, being a nerd tinkerer I decided to get the old lady (1972) some brains. I got a LTE/4G wireless router and an Intel DN2820FYKH NUK computer, both running off 12V. The NUC is a little 2.4GHz Dual Core, $150 PC which uses about 10W running Windows 7 or 8 full blast. Thats 1A. The router is another amp. The NUC will be hooked up to all the NMEA sources and play switchboard, map display and serve GPS to my iPad. I can afford to have 20W going full time in the boat. It will be and so on. Then it struck me .. what if the boat starts leaking? Its idiotic that the bilge pump would drain the battery in 20 hours if the boat has shore power. The bilge pump would use 4A while the toys use 4A and in 20 hours, I would have 2 ropes pointing into the water and a very wet boat brain. I decided to get a proper 12V shore power and purchased a din rail isolated supply. Ding. $100. Then I needed fuses, terminals, cable glands, 4 gauge and 2 gauge wire, a shunt so I could measure my power consumption... and of course a very nice waterproof armored Pelican case for all the din rail gear. Ding. $120. Ding. Then of course the Pelican case turned out to be too small .. and I needed to come up with a FET based power combiner, that would allow house power switches to feed off the power supply IF the battery was low. Thats a proto PC and a 20A schottky diode is $20 and a cooling plate is $8 and .. Ding. I had successfully invented the rear wheel. As it turns out, it is MUCH more efficient to just put a larger charger in. Having form 25 batteries in my boat (which probably needs to be revised) I only have about 80Ah capacity and should therefore not charge with much more than 20A. The AGM batteries can take about 40% of their rating in AH, allowing them to be charged in 2.5 hours. Normal wet batteries are better off at half that. What I did NOT realize is that my old wet battery probably was in jeopardy due to my low amperage charger. I have designed several chargers in my time, but mostly for gel cells and LiPo. One of my chargers is presently used in the ISS for charging space suits. Space is not friendly to acid batteries, especially not upside down ones, so I managed to avoid their finer details. It turns out wet batteries gather sulphate sludge at the bottom. If they are charged vigorously, the heat and gas bubbling will stir the acid and dissolve the sulphates ... while filling up the cargo hold with the highly explosive Browns Gas of course, just to add to the fun. AGM batteries re-absorb the hydrogen and oxygen, making it back into water. They have a lot less problems with gas. So I went and read up on all the various chargers. Some swear by the ones that have a fan in them because they dont overheat ... but others like the completely sealed, potted versions. I am with #2. I have made lots of electronics for deep sea diving suits and if its not potted, it dies. I have seen what my boat can do with plain copper wires, thank you. If the charger has a 90% efficiency and can run 40A@12V, its only 48W of heat it has to get rid of at peak charge, so I dont think its a real problem with new chargers. Most chargers will do a 3 stage charge. 1) Bulk. Just pump in all it can take until voltage reaches 14.5V. 2) Absorption. Constant voltage = 14.5V, current decreases. 3) Float. Lower the constant voltage to 13.5V. That unfortunately is not too far off what the trickle chargers that were originally in the boat did. I noticed that my Genius GEN2 Mini makes a lovely little click when it goes green. That means it turns off the charging altogether and waits for the battery to get under a set threshold ... which spurs it to do another Absorption cycle. This gently massages the battery, which is EXACTLY what it likes. I have further heard that the units from NOCO also, every 24 hours, initiates a full analysis and charge cycle to make sure the battery is re-conditioned if there is a problem. There are alternatives to just upscaling to a GEN2 or GEN3 from NOCO. The local Steveston Marine has Promariner and Powermania chargers, which both have power factor correction and high efficiency. The PowerMania M220 for instance is fully sealed, but it only has the 3-stage charge cycle. They have really good prices on those ones. What I consider dangerous is that the PowerMania will direct all 40A to ONE battery if the other one is fully charged. Its great if you are in a hurry, but small batteries may not like that kind of charge rate and there is nothing that can be done to reduce it. The GEN2 has max 20A on each channel with no redirect. I hear Xantrexs star is falling a bit - which is sad, Xantrex is a local Vancouver company and I know one of the original owners, Johan Dooyewert. Nice man. He has left, though. I think it is going to be the 20A GEN2 or GEN3 for my purpose. The batteries will love me and I can take the Pelican case back. The nerd gear will go into another waterproof case and I got a fully sealed and potted 10A voltage stabilizer (8-24V in, 12.0V out, 10A) off eBay for a ridiculously low sum. Then I can keep the 12.0V specs and not have to worry at night. I am of course not in any way associated with NOCO, but I kinda like what they do. Tomorrow I will give their engineers a call and hear a few details.The manual is very unsatisfactory for a nerd. I need to know the dirty secrets - and I will report here, if they dont stick me an NDA. Initially I thought their chargers were a low end product and all the fancy ones with displays etc. were much much better... but I have changed my mind, I think. This may be the way to go.
Posted on: Wed, 15 Oct 2014 05:21:28 +0000
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