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harrywilliams1 avatar image
harrywilliams1 asked

Is the charge current doubled when connecting two batteries in parallel?

I am installing a basic 12V off grid system into a van. I want to charge two 100ah AGM batteries (wired in parallel) from solar as well as from the starter battery when the engine is on.

I am using a 370W panel (https://www.solarheroes.com.au/wp-content/uploads/2020/11/AU_Datasheet_HoneyM_DD08M08II_2020C.pdf), so was going to use 100/30MPPT.

Then was planning to use an Orion 12/12 9 for charging from the starter battery.

However, the battery I was planning to use (https://www.jaycar.com.au/medias/sys_master/images/images/10049096351774/SB2560-manualMain.pdf) has a max charge current of 25A, recommended 10A.

Therefore, I wanted to know if the charge current doubles when you connect two batteries together in this way. If not, do I need to find batteries with a higher charge current?

Also if you notice any poor choice of devices please let me know!

battery chargingorion-tr smartstarter battery
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2 Answers
Alexandra avatar image
Alexandra answered ·

@harrywilliams1

If one battery is 10A then two means [the battery bank can take] 20A of charging.

Just be aware that the Orion 12 12 9A is a converter and so does not have three stage charging. If you are using it to boost battery charge that is ok, but longer period of runninwill mean battery overcharge which is bad for them.

Maybe add a way to tell battery SOC as well.

Needing or wanting batteries with a higher charge or discharge rather depends on your use. If you can individually connect them to a bus bar rather than daisy chain them.

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elvis avatar image
elvis answered ·

Not sure I fully understand the question. The Orion 12 12 9A will only put out 9 Amps continuously. With two batteries in parallel to charge, It will be cut in half not doubled.

If you are talking about the Charge current applied from solar with two batteries in parallel, It will be cut in half not doubled. If your MPPT produces 20A into the 2 batteries, it will be felt as 10A into each battery (Assuming same SOC).

If you are asking, Does the max capability to accept a charge double with 2 batteries connected in parallel, then as described above the answer is Yes. As in, can two 10 amp max charge current batteries in parallel be charged with 20 amps. Yes

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