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paulz
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# Posted: 13 Oct 2022 12:52pm
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Well shoot, it's October, overcast, sun is low in the sky and my summer of solar excess has ended. Time to pull out the generators and chargers. We were OK until my wife got used to the electric coffee maker and big screen TV.
I grabbed this Astron 50A power supply from the firehouse sitting on the shelf, came out of a rig. It's a beast, 40 lbs.! Giant iron core. Has a voltage adjustment, 12-15vdc. Going to try it out today but curious if MSW generator is bad for it?
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Nate R
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# Posted: 13 Oct 2022 01:27pm
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So you want to use this as a battery charger from a generator?
What's a MSW generator? Inverter type?
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paulz
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# Posted: 13 Oct 2022 01:35pm
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Yes. Modified sine wave, non inverter.
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Nate R
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# Posted: 13 Oct 2022 02:15pm
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What generator are you using? Most produce a pretty clean sine wave, actually....
Even so, I'd think that old school regulated power supply with a iron core transformer would be fine....
-Nate
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paulz
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# Posted: 13 Oct 2022 02:45pm
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I'm going to use an Onan RV generator, 7kw, and your right, it does put out a clean sine wave. I forgot I tested it with the cheap oscilloscope I got last year (see thread)
https://www.small-cabin.com/forum/8_10929_0.html
But it uses a lot of LP and is probably overkill for 50A a 12V, I can never understand the calculation. I have a 1,400W gas generator I want to try, it's sine wave isn't as good (last photo I think on that thread). If it will do the 50A it would be a lot more efficient, I think.
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paulz
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# Posted: 13 Oct 2022 03:39pm
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OK I tested it with the Onan, fine. Now I have the little Honda going and it's working fine, though it's only charging about 20A since the batteries are pretty well up and the solar is putting out 25A.
Thanks Nate.
Wife's watching TV and drinking coffee, lol.
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paulz
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# Posted: 13 Oct 2022 05:14pm - Edited by: paulz
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So this power supply is about 4 times the size and 10 times the weight of the Meanwell power supply I used last winter, which is 40A. This is what it looks like inside, no giant iron.
What is the difference and why use one over the other?
EDIT: Ok, I remember, one is switched mode, one in linear. Now I just have to read up on that.
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travellerw
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# Posted: 13 Oct 2022 05:59pm - Edited by: travellerw
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That Meanwell is a modern switching power supply. It uses advanced circuitry to "chop up" the power, then smooth it back out at the desired voltage (in layman's terms).
That other power supply looks like and old school bridge rectifier and transformer design. Rectifies the AC to DC, the runs it through a step-down transformer. (or possibly the other way around)
While both can be used as battery chargers, that is not the primary purpose of either. Battery chargers usually contain circuitry to provide the best algorithm for a certain type of battery (bulk, absorb, float for FLA, bulk and float for LFP).
If I was powering devices and electronics that needed clean DC power regardless of what the AC line is doing, then the Meanwell is the winner. However, if you are charging a battery, both will probably work equally as well. The Meanwell will probably be more efficient though. On the other hand, the only way you could probably kill that old power supply would be with a hammer!
Another thought... You can use both (its really no different than using 2 solar controllers). Then you get 90A of charging.. Vroom Vroom. Just set the top voltage on one of them to be .2V lower than the other. Once the batteries reach that voltage, all the current will come from the charger with the higher voltage, until they reach its voltage.
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paulz
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# Posted: 13 Oct 2022 06:18pm - Edited by: paulz
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Thanks Trav, was hoping you'd see this. I was just reading up on it, good chart of the differences here:
https://en.wikipedia.org/wiki/Switched-mode_power_supply
What's sticks out is the low efficiency of the linear one. I expect they used it in the fire truck for reliability and low ef noise or whatever you call that.
i'm not looking to fully charge my bank or do any floating etc., just give it a boost at times when it's low. Good to know I could use both together, the 7kw generator could do it and the batteries even more, just need bigger cables. I checked today and was losing almost half a volt between the power supply and the bank.
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gcrank1
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# Posted: 13 Oct 2022 06:50pm
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I kinda like the idea of being able to hammer in amps to a bat bank IF the bat chemistry/type can take that much C-rate; mostly because I dont like having a gen running more than necessary. And when necessary it would be nice to have it do as much as possible.
Id use as small a gen as possible to accomplish all of it.
If I used 40Ah out of my lfp 100Ah bat in one 'day' it would be nice to have it all topped up in less than an hour vs 2+hours with a 20amp charger. I wouldnt even need the sun that day.
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travellerw
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# Posted: 13 Oct 2022 07:09pm
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Quoting: paulz What's sticks out is the low efficiency of the linear one. I expect they used it in the fire truck for reliability and low ef noise or whatever you call that.
That is one big advantage of linear power supplies, because they don't "chop up" the power (no switching) they produce little to no RF interference. It doesn't mess with VHF or HF radio frequencies. However, they are only about %60 efficient.
However, I suspect that the fire truck used it because that was all that they could get back then. Switching technology was around but VERY expensive until around the year 2000ish. Modern designs have mostly eliminated the RF interference and the efficiency gains are really attractive. I'm guessing that Meanwell has an efficiency around %87 or higher. But... If you have lots of power and care more about reliability, then the linear one wins (fewer parts, simpler parts, parts less susceptible to overheating).
If you have both this year, then you are going to be pretty setup!
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paulz
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# Posted: 13 Oct 2022 08:46pm
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Quoting: gcrank1 I kinda like the idea of being able to hammer in amps to a bat bank IF the bat chemistry/type can take that much C-rate; mostly because I dont like having a gen running more than necessary.
No doubt there. My batteries can take 70A each, and I have four. However, as an absentminded goober, I'm a little nervous around that much juice. I can't count how many times, despite staring right at the terminals, I've hooked up batteries backwards. Cutting my teeth on automotive electrical, it was pretty hard to get injured with the low voltage, although I did learn about disconnecting the negative terminal first by grounding the wrench off the plus side and blowing a battery up in my face. I'd like to think, hope that with the cabin electrical I've learned to be more patient and thoughtful.
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paulz
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# Posted: 14 Oct 2022 09:01am
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But, as I remember, no matter how many amps you throw at the batteries, they will only accept so much depending on SOC. I don't think I've ever seen my LFPs take everything charger was rated at. Never had them down below 3.00 volts.
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gcrank1
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# Posted: 14 Oct 2022 10:29am - Edited by: gcrank1
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Ive had my lfp take full amps from the Meanwell you sent me. Yes, it was well down to the lower knee.
I had to crank the volts up to about 14.4, iirc watching my ammeter.
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paulz
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# Posted: 14 Oct 2022 09:22pm
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What gauge and how long are your jumper cables?
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gcrank1
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# Posted: 14 Oct 2022 10:16pm - Edited by: gcrank1
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10ga. fine wire with ring terminals about 2 feet long.
With the bat at the lower knee, pretty well depleted beyond running anything but light duty led lights or usb charger (ie, wont run a small fan any length of time) it is ready to take full 'rated' C-rate charging (more than the MW PS can do).
With a good vom and ammeter hooked up at the bat I set it at maybe 13.8v but the amps were less than the MW is rated for (iirc, 40a @ 12v) so I started turning up the v setting. At about 14.4 it topped out the amps (bat is spec'ed to a top of 14.6v) I kept my eye on the meters, at about 2.5hrs charging time the amps dropped way off; I let it charge another 15min or so and pulled the plug.
Ive done this with both my 'rated at' 100Ah lfp bats and get A Lot of running hours off of them (so good I stopped charting usage). My initial 'load testing' indicated they both are giving me pretty much a Useable 100Ah. If a 40Amp PS recharges in 2.5 hrs thats 100 back in.
Reading up on lfp's over at diysolarforum.com it seems one is better off/safer to discharge deeper than to overcharge. Im trying to stay 'between the knees' and never, Never, NEVER overcharge (ie, do Not depend upon the BMS to shut it off on the high end, if it fails imagine the Damage to the cells). Dont assume the bat manufacturer used a high-end BMS; Not likely!
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paulz
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# Posted: 15 Oct 2022 02:16pm - Edited by: paulz
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10g wire sounds small but I looked it up and for that short a run is says 40A is OK. Old car alternators that were 40A had that size I believe. New cars much larger.
Spent yesterday and last night in the city after doctor appointments. Must not have gotten much sun at the cabin, bank didn't charge as much as I had hoped, wife is planning on watching the baseball playoffs all day. I'll be playing with chargers and generators...
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gcrank1
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# Posted: 16 Oct 2022 10:30am
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Or am I remembering the MW output wrong? Its been long enough since I did the last recharge that my mind is slipping a gear.....
Since the MW is 12 or 24v does it do 40A@12V/20A @24V or the other way around?
Anyway, I do the vom AND an ammeter hookup at the bat to read the 'delivered' volts and amps so I can catch the amps drop at 'the top'.
If I dont mind it taking longer to do that (like charging at home on the grid) using the lower voltage setting on the MW (resulting in lower amps delivered) makes for a more gentle charge cycle. That may be a good thing.
Nice thing about LFP is that they dont need the Lonnggg absorb stage at the end like LA. Get em to the 'high knee' and that is all they need. Pull the plug and put em in service.
Or, lets say you deplete an LFP down to the lower knee but dont have the time to recharge fully before needing to put into service. Do that repeatedly with LA and you kill em. Take a 'low' LFP and only recharge to 50%, NO problem; do it over and over, its ok. Catch up with a full charge whenever you can.
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paulz
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# Posted: 16 Oct 2022 01:11pm - Edited by: paulz
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i'm genny charging right now, planning a big Sunday of TV. No solar charging yet today. I have two Meanwells in parallel (of course), set at 14.2, with separate 110 plugs. Bank was at 13.1 when I started, with one MW plugged in it 28A incoming. Plugged in the other MW, still 28. Right now it's at 13.4 and 26 coming in, again no change using both. So I'm surmising that's all they will accept, unless the 6' 6awg cables aren't sufficient.
Pretty sure I have seen 40A out of them at the 12v setting when I was initially testing.
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gcrank1
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# Posted: 16 Oct 2022 02:37pm
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Iirc the LFP's typically settle at 13.3ish even if they read higher right off the charger. By the time mine hit 13.0 there really isnt a lot of beans left and they quickly drop so Im thinking that 13.0 is at the top of the lower knee?
So, most of the Ah's are in that .3 volts, but its A Lot of Ah's!
That 28A thing is why I waited until mine were well down so I could get a sense of what the MW ould really pump out and what the the bats could take. Since your bat is taking 28A tells me that it is not down at the bottom.
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gcrank1
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# Posted: 17 Oct 2022 11:46pm - Edited by: gcrank1
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I was just over at diysolar again checking lfp charging parameters. Maybe I had missed this before....and now it makes sense?, but IF your 12v lfp bat 'settles' to whatever voltage, lets say 13.4, it doesnt make any sense to charge it any higher. Sure, at a higher charge setting it will read higher than that, then it drops back down and stabilizes. No real usable Ah's of consequence in any 'surface charge' above the settle voltage so why stress the bat. I believe any voltage reading above the settle voltage 'burns off' quickly once you put the bat under load anyway.
So now I get to do a recharge again and NOTE the settle voltage of each bat (Frog Tape and Magic Marker this time!). But NO rush like with LA, I can let these sit at 13.1 all winter if I want.
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paulz
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# Posted: 21 Oct 2022 11:13am - Edited by: paulz
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Quoting: gcrank1 so I started turning up the v setting. At about 14.4 it topped out the amps (bat is spec'ed to a top of 14.6v)
I'm doing some reconfig this morning, including moving the Meanwell inside the cabin. Will be harder to get to the voltage adjuster. I took it down from 14.6 to 14.2 recently but wondering if I should crank it back up. I know recent advice was to only charge to 14.2 but as long as I monitor to stop charging when the bank is at 14.2, what's the harm if the charger is set to 14.6? As you know it does seem to increase the amps.
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gcrank1
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# Posted: 21 Oct 2022 12:07pm - Edited by: gcrank1
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The harm is when you forget, and if you are like me you have forgotten something critical, and the top charge of LFP is Critical. Let it go on too long and bloating/bursting/etc happens to those cells!
Fwiw, Ive been known to burn something on the stove while prepping something else on the kitchen counter.
Dont want that cooking to be my LFP's.
That said, you are right, cranking up the volts will raise the amps the MW puts out. The question becomes,"how important is it that you get a smidge faster recharge?".
I truly believe we can bank on the advice of Steve_S.
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Steve_S
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# Posted: 21 Oct 2022 01:06pm
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RohOh I have been "invoked LOL...
Take a 12V/100AH LFP Battery which discharges @ 1C / 100A for 1 hour and can take charge at 0.5C / 50A for 2 hours.
IF you push 50A at it, it will take it ! BUT that also pushes the Charge Input to the max and IF the cells are not "perfectly matched" at roughly 3.350-3.400 per cell they will begin to deviate and the cursed "Runner Cells" which will rise in voltage faster than the others and will often hit the BMS Cutoff Point and stop taking charge as the BMS hits HVD and disconnects (like it should). IF you have marginal or tired (worn) cells the sweet spot is around 0.3C / 30A.
General Exceptions are Really Good Quality Batteries like Battleborn, Valence Batteries, Rolls Surette LFP, Volthium, Relion, Enerwatt, Simplify etc. NB These are ALL UL, CSA & ETL Certified, and all use premium components & Matched cells. BUT quite $$$$ as well.
Basically, 13.8V (3.450Vpc)-13.9V (3.475 Vpc) will keep you safe n sound without instigating runners, provided you are not pushing the Amp Rate to the max.
Also if you have batteries in Parallel, remember that they will split & share the Charge & Discharge and they do so proportionately relative to their capacity. IE: a 100AH & 200AH in parallel, the 100 will take less amperage while the 200 will take more during charge. The same applies to when they are discharging UNTIL both batteries reach the low end of the Working Voltage Range, pending on BMS & Setup the 200 may try to back charge the 100 to keep the bank even (that's a waste).
I have an Inverter/Charger than can push up to 100A @ 24V, Solar Controller can push 79A @ 24V, and a Hackster Charger which is 2 Meanwell S600-12's (50A) that are paired together (Meanwell knock offs but the same thing). I have pushed 200A Charge at my bank and that was at the time 908AH and was interesting to test that and watch what happened.
Re Meanwell type power supplies:
Even though they can push 50A if the battery is filling up and resistance increases the Amps taken will drop accordingly BUT the meanwell will start to get quite warm and it will start to Buzz (quietly) which is NOT Good !
Hope it helps, Good Luck.
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paulz
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# Posted: 22 Oct 2022 09:42am
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Thanks Steve.
I'm still unclear on the relationship between volts, as measured at the power supply unloaded, and what the batteries actually see. For example, most of the wall worts I have played with for various uses all measure over their, or their associated device's rated voltage, a 12V might measure 15 when measured unloaded. Same with car battery chargers, or the car itself which will measure 14+ volts. So what happens if the voltage is 20, even though the amps may be very low? As long as the battery itself never exceeds what is considered safe (14.2 or whatever).
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gcrank1
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# Posted: 22 Oct 2022 10:30am
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Paul, I wonder if your bats need to be 'top-balanced' since they were used and now you have used em a lot more? Ive read at diysolar that some folks are periodically top balancing; maybe that gets the 'runners' and 'dogs' closer together so there isnt a HVD or LVD prematurely from the rogues.
Iirc it means doing each bat separately, taking up to that top voltage, discon and let settle for a day then repeat?? The settling lets the dogs catch up with the runners and reducing the delta.
Again, I defer to Guru Steve 
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paulz
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# Posted: 22 Oct 2022 10:56am - Edited by: paulz
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I checked them earlier this week, they plug into a laptop with Valence software. All 16 cells were equal. The batteries have built in BMS, and I think balancing is included, I have seen them go through it when I had the laptop plugged in.
Had to postpone my reconfig yesterday, need another circuit breaker. Still just wondering about turning up the MW to 14.6 and getting more amps into the bank quickly and less generator run time. Believe me, I keep a close watch on battery voltage when the genny is running, can't wait to shut it off.
Had to brew coffee yesterday, bank was not that strong so I ran the coffee make directly off the generator. 1,400W genny and the coffee maker draws 1,500 but somehow it did it and wasn't struggling, 15 minutes. I think that might be the new plan with the limited solar now. Rest of the cabin still OK on just solar.
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gcrank1
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# Posted: 22 Oct 2022 11:34am - Edited by: gcrank1
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Thats how I run, my big inverter died and I havent replaced it, just run the little, quiet inv/gen when I need the big power (usually briefly used); ie, small microwave, brew pot, vac cleaner. The bats run the 300W psw inverter which has been enough for the lighter load stuff. If/when it dies I will probably get a 500W though, the self consumption is so similar so why not have the extra capacity.
When I did my last recharge off the MW I took it up high, just to see, and monitored it Very Closely! In use that bat seemed to give me maybe 2 more hours over our standard usage (it is so hard to tell without a coulomb? counter). We only run one 100Ah bat at a time so I have developed 'a feel for it'. As I mentioned before, I think that 'extra', if it is such, burns off quickly; my head tells me it isnt worth the trouble to do/monitor/etc. It kind of defeats the purpose of LFP.
Maybe think of it like this, with the old school LA we were used to we stayed in the upper 30% of charge for long bat life, only went to 50% occasionally and had HAD to recharge asap for the bat health/life. Even IF your LFP's are old and tired you are getting way more usable Ah's/Watts out of them and Don't have to keep them always recharged full asap.
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paulz
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# Posted: 22 Oct 2022 01:56pm
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Quoting: gcrank1 I mentioned before, I think that 'extra', if it is such, burns off quickly; my head tells me it isnt worth the trouble to do/monitor/etc.
Right, but I'm not looking to charge to a high voltage, just to get from high 12s to 13.4 or so in a shorter amount of time to save gas and generator run time.
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Steve_S
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# Posted: 22 Oct 2022 01:56pm - Edited by: Steve_S
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@Paulz, I would NOT worry too much about the Valence Batteries as the cells they use are premium Matched & Batched, plus you have the app and can see they are behaving properly.
As for 14.6V (3.650Vpc), you not gaining anything other than stressing the cells. Be conservative & cause less stress by charging to a max of 14.0V (3.500 Vpc)
BTW: LFP will always settle to the working range, it's just the chemistry.
Even with a Meanwell type charger, if it's 50A output, as the Resistance in the batteries increases the less amps they will take till they are Saturated. "EndAmps"
100AH X 0.05 = 5A EndAmps/Tailcurrent. I don't remember what size batteries you have.
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