Yet another battery charger question...lol

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dacflyer
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Yet another battery charger question...lol

Post by dacflyer » Tue Nov 10, 2020 5:02 am

Ok, so I have ordered parts for the 1st charger i mentioned that i'll be rebuilding.
But now i have a different charger of what i actually need.
I acquired 2x Lestermatic II 24v 25A chargers. They need some TLC< but they are otherwise working.
I had to put new cords on them and DC connectors.
These chargers are designed for FLA batteries, but i am wondering if they can be modified for SLA.
the charger is supposed to cut off once the batteries have reached full charge. But it's too much for SLA batteries,
So i need to figure out if i can modify anything on the board...
Has anyone done such a thing to these chargers ?
I called up Lester, But they didn't want to help me.

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Janitor Tzap
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Re: Yet another battery charger question...lol

Post by Janitor Tzap » Tue Nov 10, 2020 9:26 am

Hmmm...............

Sealed Lead Acid type batteries, {SLA} are not as tolerant to over charging, or under charging as the Flooded Lead Acid type batteries{FLA}.

Thus, you need a circuit that will stop the charge at the preset voltage level, and come back on when it drops to a set voltage level.
Here's a circuit that should do the job.
https://www.homemade-circuits.com/3v-45 ... c-battery/

As for the Lestermatic II 24v 25A chargers.
See if you can find the Model Numbers on them, and then do a search for the operation manual.
May turn out you don't have too do any modifications to them.
:wink:


Signed: Janitor Tzap

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dacflyer
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Re: Yet another battery charger question...lol

Post by dacflyer » Thu Nov 12, 2020 5:59 am

I might have to resort to a different circuit... I was hoping to just modify the board that's currently in there.

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Re: Yet another battery charger question...lol

Post by haklesup » Thu Nov 12, 2020 2:27 pm

What's inside? By the looks of it from ebay ads, seems like just a transformer, rectifier, fuse and ammeter. Certainly can use that as the unregulated front end to an add on circuit if you need V or I cutoff. Simplest mod might be to run the output through a relay contact and control the coil with some sort of level detector circuit. If the battery is not critical and you are not trying to maximize lifetime, then just intermittent charge with a timer may be sufficient to keep it in a ready state. I doubt you are taking about modding a SMPS charge circuit which would require a schematic to even discuss. A smart charger is just a regulated power supply with specific regulation requirements. If you have a big transformer you have the most expensive part of a linear supply.

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dacflyer
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Re: Yet another battery charger question...lol

Post by dacflyer » Tue Nov 17, 2020 10:51 am

This unit ( model 19740 Lestermatic II )
It has a control board in it.. It cuts the battery off once it's full.. But this would overcharge AGM / SLA Batteries.
And yes i am trying to maximize the battery life.
These batteries are on one of my solar projects. I only need it if there's more than 2 days with out sun.
Right now, i am only charging it up for a few hours til the voltage is up..
I may try to search for a charge controller board, something i can program...
and have that control the secondary of the transformer, I have plenty of heavy duty relays. Some can handle 150A to 500A

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Re: Yet another battery charger question...lol

Post by haklesup » Tue Nov 17, 2020 11:43 am

Certainly no shortage of Solar compatible or other charge controllers on ebay or Amazon for under $100

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Re: Yet another battery charger question...lol

Post by dacflyer » Wed Nov 18, 2020 5:41 am

I have a good charge controller, but there are times when there's a few days with lousy or no sun, So this is when i need to use a charger for a while, like over night.. I got these chargers for free, so I'd like to try and use them if i could..
I seen this on ebay...

https://www.wish.com/product/xh-m602-di ... &share=web

.
Screenshot_2020-11-18 XH-M602 Digital Control Battery Lithium Battery Charging Control Module Power Supply Module Charging [...].png
Maybe i can use it.. Only issue is, they only have 220V units, not 120v, So I'll have to change the transformer which is easy to do.

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Re: Yet another battery charger question...lol

Post by haklesup » Thu Nov 19, 2020 1:52 pm

Its not unreasonable that the charger you have has a resistor divider that sets a threshold for a comparator you can adjust but without a schematic or even a photo, its pure speculation.

If you keep looking, I'm sure you can find a 120V version, sometimes the graphics in ebay ads don't match the voltage of products advertised on the US site. The charger you have likely has lots more current than this small module.

This one can be used with your 24V charger as the input, this way you can get the high current benefit from what you have and use this is a secondary regulator output stage.
https://www.ebay.com/itm/XY-L30A-DC-6-6 ... SwxWFe~PRF


As long as you have a switch of some sort to toggle between solar charging and line charging then you shouldn't have a conflict. I'm not sure what would happen if the outputs of both tried to charge the battery together, it might work if the AC charger is always a little lower but that seems improper. Do you intend to manually swap over or use a photodetector and delay timer to operate the switch*. Seems like that's more complex than the charger circuit.

*detector output drops below threshold then it allows a timer to start counting, when it reaches a set count, it switches over to AC. Also might want to detect battery voltage and time of day to disable the switch when you don't want it to toggle. Seems like a good job for a uController with 2 A/D channels and 8 IO pins. Not a high BOM cost but lots of development time

questioning why you don't just let the solar run dry and then switch over to utility AC like most systems. Charging the battery by AC will undoubtedly be less efficient than directly powering the AC loads with utility power. I guess this makes sense if the solar system is limited in what you power with it to some lights especially if they are low voltage and you don't use an inverter, then there is no AC option to switch to.

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Re: Yet another battery charger question...lol

Post by dacflyer » Fri Nov 20, 2020 4:21 pm

The unit i showed you just controls the turning on/ off the primary of the transformer... but i could let it control another relay for higher input current.
If i did get it, i could change the transformer on it from a 220v to a 120v. i think i did that with something else before.

as for a solar conflict. the charger is direct to the batteries, not going thru the solar controller. so it's not an issue..

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