Battery Charger with Auto Cut off

Hello
I have this charger: **broken link removed** and a solar battery bank made of these batteries: https://www.osibatteries.com/p-1052-enersys-powersafe-sbs-60-sealed-lead-acid-battery-120v-510ah.aspx connected in a way to get 24V 200Ah.
I know that this charger is not suitable for charging these batteries but that is the only one I got at this moment. So since it doesn't have a cut off at certain voltage I have found a diagram to a circuit that is designed for that but only for 12V: **broken link removed**

My question is: Is there a device that I can connect between my charger and batteries that has the features for a 24V system and that can cut off the charger at 27,6V when the batteries are full?
Thank you very much...:smile:

What you need is a current limited constant voltage stabilizer, which takes in the voltage from the solar cells and drops it to the magic 27.6V. It should be current limited or if the batteries get flattened overnight the charging current the next morning will not be excessive.
Frank

chuckey said:

What you need is a current limited constant voltage stabilizer, which takes in the voltage from the solar cells and drops it to the magic 27.6V. It should be current limited or if the batteries get flattened overnight the charging current the next morning will not be excessive.
Frank

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Hi chuckey, sorry if I didn't mention it before but I have already a solar charger: https://www.ebay.co.uk/itm/310857447913?_trksid=p2060778.m2749.l2648&ssPageName=STRK%3AMEBIDX%3AIT but now I need to use my grid charger when there is no sun. So, can you please give me a link to this kind of current limited constant voltage stabilizer that can handle my charger with 24V/15A?
Thnx

SunnySkyguy said:

The 2S4P array of 8x 12V,50Ah indeed gives you 24V,200Ah capacity. This requires automatic CC,CV and FV with load balancing. For a single system estimate the cost to be between 1$ and 3$ per watt-hr storage capacity depending number of life charge cycles expected and consumed.

Your battery is listed as $322 which is 12V, 51Ah or 612Wh or 2$/Wh. , but I do not see any specs for charge cycle life.

You should expect the electronics to be only 10-20% of the total cost with all features included.

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Thnx Sunny, I'm not much in the techtalk. Can you please tell me if it is possible to use my cheap Einhell charger paired with some -of the shelf-ready to buy- electronic device to protect these batteries from overcharging or can I throw it away?

The 2S4P array of 8x 12V,50Ah indeed gives you 24V,200Ah capacity. This requires automatic CC,CV and FV with load balancing. For a single system estimate the cost to be between 1$ and 3$ per watt-hr storage capacity depending number of life charge cycles expected and consumed.

Your battery is listed as $322 which is 12V, 51Ah or 612Wh or 2$/Wh. , but I do not see any specs for charge cycle life.

You should expect the electronics to be only 10-20% of the total cost with all features included.

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No reason why you can't use that small charger. A full charge may take 24hrs. Then check float voltage after current drops near zero.

Look carefully at the instructions for your Einhell charger. Does it have an automatic taper setting? This prevents overcharging (assuming the unit is of any quality to speak of).

From the looks of it, by itself it should charge your battery. Set it to 24V. Plug it into 230 VAC.

Its specs state it will deliver 10A (effective) to a 24V battery. A charge session will take several hours.

It's a good idea to keep an eye on it. As the battery rises to 28.8 V, charging current should decline.

However if it is still sending full current, then you must stop charging by disconnecting it.

I would not expect it to indicate a certain voltage at which it cuts off. The battery chargers which I have worked with, all detect battery voltage via internal circuity. Their meters indicate amperes, but not volt level.

As you have a

30A-MPPT-Solar-Panel-Regulator-Battery-Charge-Controller-12V-24V-With-LCD-USB-PK (MPPT), then at night just replace the solar panel input with that of the battery charger. This way you only have to configure one device.
Frank

There are two specs

Tortoise
24V:7.0Aeff./4.7Aarithm

@60% efficiency use 4.7 arithmetic mean thus 200Ah =42hours.

Hare
24 V:10 A eff. / 6.8 A arithm
200Ah means 20hrs min. , 30hrs more likely

To Brad: Here is the inside of the charger. I think it is very basic and I have not found any automatic taper setting so it could come to chuckey's idea trying to connect it to the solar controller.. :wink:



To Frank: Do you think that it is ok to set the charger to 24V quick or slow?

To Sunny: Were your estimates based on a 50% or 80% empty battery?

Once again thank you all for your recomendations. I think I will put a voltmeter on that charger to monitor the voltage.:wink:

The circuit with 3 trimpots is where you look. Two have red wax on top.

SunnySkyguy said:

The circuit with 3 trimpots is where you look. Two have red wax on top.

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But, that red wax is on a ordinary screw that holds the 220V wires in place. There are no trimpots here. :-|

Ok bad eyes on photo. This looks like an unregulated charger. You must add a series regulator or simply put the AC on a timer. The SOC can be estimated from V @ 100mA load between 11.5 and 12.5 , I think or thereabouts.