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gcrank1
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# Posted: 15 Jul 2024 10:02pm
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I have an old HEAVY rv converter (must go 24oz to the lb) that was 'on the shelf' when we bought this place.
Must be a Real transformer!
I don't know much....guess 120vac in and 'something dc' out. Most of the comments Ive seen regarding them is that some are worse than others even for Lead Acid batteries. My impression is that they aren't 'well regulated' and folks tended to leave then plugged into shore power too long?
Anyway....(am I bored?) Ive been wondering if I should splice a male ac plug on the input wire stubs and test the output wires for for no-load output, just like Ive done with the dedicated power supply I use for lfp recharging.
I'll look for an adjuster too and see if I can regulate the output volts.
I should be able to treat this like a 'power supply', right?
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Brettny
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# Posted: 16 Jul 2024 02:30pm
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I have a RV charger for may only 120v to 12v charging source. They are typicaly transformer based units. I have FLA bstteries.
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ICC
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# Posted: 16 Jul 2024 03:17pm
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@gcrank1
Even if the output voltage can be internally adjusted, my concern with an old converter would be whether or not the unit can control the voltage with sufficient precision to be useful and safe with LFP batteries. Many, maybe most of those old RV converters are very crude devices as lead-acid batteries were known to be quite forgiving as long as the electrolyte level was maintained.
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gcrank1
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# Posted: 16 Jul 2024 04:20pm
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If I was running on the 'edge' of high charging voltage; ie, imo 14.6v and it was +/- 1/2 to 1v Id be nervous, yes.
My normal is 14.0ish for lfp.
I'll have to look into that output voltage tolerance 
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Brettny
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# Posted: 17 Jul 2024 02:29pm
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My Iota 30a only charges to 13.7v.
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ICC
Member
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# Posted: 17 Jul 2024 06:27pm
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Quoting: Brettny My Iota 30a only charges to 13.7v.
And I just remembered that these pots that are used to fine tune the output voltage are often meant for a very limited number of adjustment cycles. They can easily be damaged, worn, if used frequently to adjust output.
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pabear89
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# Posted: 17 Jul 2024 06:58pm
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While the old ones have an adjustable baseline,
They do a good job of charging but lack the floating charge level the newer ones have.
It Will boil the battery if the is nothing pulling power from it. From the been there will a cooked battery files.
But if you're in need a of a quick charger for reg battery you don't wish to just jump it could be handy.
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travellerw
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# Posted: 17 Jul 2024 08:19pm
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Quoting: ICC And I just remembered that these pots that are used to fine tune the output voltage are often meant for a very limited number of adjustment cycles. They can easily be damaged, worn, if used frequently to adjust output.
This %100 true and good advice. These pots are not meant for continuous use.
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Steve_S
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# Posted: 17 Jul 2024 08:36pm
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I know that some of the older converters (1980's) were actually super solid, well made with seriously durable (if not basic) electrics. There was a few Vids on YT that showed people converting them to Bench Power Supplies and using some electronics on the front ends for fine tuning & tweaking. I dunno if it's of interest or not but could be a good project to "tinker" with.
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paulz
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# Posted: 17 Jul 2024 09:14pm
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This thread reminded me I have something kicking around in my shed too. Astron, 13.8 vdc, 37 amp. Sucker weighs 40 pounds! Where I got it, original use I have no idea. Never plugged it in, maybe a good Lfp charger?
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gcrank1
Member
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# Posted: 17 Jul 2024 10:58pm
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I think it could be, Paul, just run it like you have ben using the Meanwell and watch the tail-current to disconnect at full charge.
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paulz
Member
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# Posted: 18 Jul 2024 03:02pm
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I plugged it into the inverter, it’s working so far. 13.90v on the VOM unloaded. I’ll try it on a fla then a little 25ah lifepo4 sitting here.
We used to go by a place that gave away handicap stuff my wife could use, they also had a free junk table, that might be where I got it. Or the flea market..
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gcrank1
Member
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# Posted: 18 Jul 2024 06:09pm
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Im curious how many amps it will pump into a fairly depleted battery.
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paulz
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# Posted: 19 Jul 2024 05:59pm - Edited by: paulz
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I stuck an fla, the ‘new’ old one I was barking about a month ago, in the golf cart. It’s been sitting on a solar panel but averages a bit over 10v when disconnected. Surprisingly it turned over a few seconds but no start. Then I put this charger behemoth thing on there, volts jumped up to 13 and the cart fired up after two minutes. My amp meter showed a bit over 6 but I don’t think it’s trustable, no sparking at the terms when clipping on. Doesnt amps really depend on what the device (or battery in this case) wants?
I’ll leave that charger on all day and see what happens. Fire extinguisher at the ready,
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travellerw
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# Posted: 19 Jul 2024 08:46pm
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Quoting: paulz Doesnt amps really depend on what the device (or battery in this case) wants?
Volts are potential, Amps are pulled to equalize that potential (at least with batteries). So yes a battery pulls what it can depending on its internal resistance and other factors.
6A seems completely within reason and may not actually spark.
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gcrank1
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# Posted: 19 Jul 2024 11:50pm
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That seems like low amps to me for a bat that was sitting at 10v (actually well dead for a 12v bat) on a converter that big. My guess is that what pumped in during those couple min. at 13v gave it enough surface charge to start the cart. Bet the bat can't hold a charge.
Btw, when you went to start you didn't have the power supply still on did you?
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paulz
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# Posted: 20 Jul 2024 01:12am
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This battery still acts odd. I just went out there, showed 12.6 with no charging for most of the afternoon. Oh boy! But turn the key, just a couple clicks. Voltage back down to its usual 10.1. Swapped in its regular batt, vroom! I have no doubt it will quickly start the cart if I charge it, but it just won’t hold. Back to the core pile again.
I agree the charger should be capable of supplying more amps. I just don’t have any other weak Flas here at the moment, not ready to risk an Lfp.
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gcrank1
Member
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# Posted: 20 Jul 2024 05:35pm - Edited by: gcrank1
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Ive reconsidered the 'low amps' from the converter.
Its a converter, not a battery 'charger' per se.
It is intended to take the shore 120vac and turn it into camper/boat 12vdc for relatively low voltage stuff and pump 'some' amps back into the house battery. That amps feed cannot be too much because there is likely nothing in the converter to prevent overcharging and destroying a battery bank when left on 'too long'.
Ive read more than a little about how those old converters have boiled out lead acid batteries and that charging a depleted battery is not quick.
On some rv forums Ive seen lots of recommendations for folks to upgrade them to a more modern design.
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paulz
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# Posted: 20 Jul 2024 11:29pm
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The DC out on this one has big terminals, easily handle 60 amp. This winter when the solar dies out I’ll swap out a Meanwells and see.
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ICC
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# Posted: 21 Jul 2024 03:19am
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Quoting: gcrank1 On some rv forums Ive seen lots of recommendations for folks to upgrade them to a more modern design.
Yes. The old RV converters were/are, IMO lousy when connected to lead acid batteries. They could not put out enough current to be an effective charge if the batteries were low and at the same time had no charge cutoff to prevent serious overcharging and eventual destruction of the battery. I know because I killed the coach battery in my first RV many years ago.
Quoting: paulz ’ll swap out a Meanwells and see
Any charger that did not have sufficient control for safely charging the somewhat forgiving lead-acid batteries is not going to be safe connected to an LFP battery. If you are going to try to manually watch the voltage and terminate the charge before the LFP os damaged I believe you are setting yourself up for an eventual failure. Why take a chance on damaging batteries you paid money for?
Just my thoughts.
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paulz
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# Posted: 21 Jul 2024 04:25am - Edited by: paulz
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What I have, Astron RS-50A, is not advertised as a battery charger. It is marketed as a ‘Liner Power Supply’
https://www.astroncorp.com/linear-desktop
What I (and gcrank) use now for off solar charging are Meanwell power supplies, carefully monitored of course. In addition I, at least, have the Valence BMS in case it ever came to that.
There may indeed be a difference in the Aston and Meanwell power supplies, and I certainly have no need to try the swap. Thanks for looking into it and please let me know if there is indeed a difference.
https://www.mouser.com/ProductDetail/MEAN-WELL/SCN-600-15?qs=RzyoSnN9rS1YLCzWuDCj5g%3 D%3D
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