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phatmatt avatar image
phatmatt asked

Victron MPPT 100/20 and Lithium Battery

Hi all, I have a Victron MPPT 100/20 that, if im not mistaken has a max 20A charge current. I have to replace some end of life 12v Lead Acid batteries for my caravan , so I thought I would bite the bullet and get a 200ah Lithium Ion battery rather than 2 100ah lead acid batteries. I have done some research and I know that the 100/20 can charge LIthium Batteries and my caravan solar set up can provide enough voltage to meet the voltage charge requirements of the Lithium battery (14.6v+). However, I am confused by many of the Lithium battery specs that state that a 200ah Lithium battery has a charging current of around 45A-50A. Does this mean that my solar set up and MPPT100/20 controller wont produce enough charging current? I also looked at a 100ah Lithium battery and that has a charging curent of 23A, does that also rule out even a 100ah Lithium battery?

I dont quite understand these terminologies (charging current etc) so would appreciate some expert insight before spending best part of £1K on a battery if its not suitably chartged by my solar set up and Victron charge controller.

Many thanks

Matt

MPPT ControllersLithium Batterysolar
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3 Answers
snoopv avatar image
snoopv answered ·

Hi phatmatt.

You had 200ah lead acid capacity (2x 12v 100ah in parallel).
Depends how deep you like to discharge your new batteries, but up to 75%-80% DOD is realistic for Lithium batteries.
So if you replace it with one 100 - 150 Ah you have about the same amount of energy available.

Charging a 100 Ah Lithium Battery (discharged to 20% SOC) with your 20A MPPT at full solar power results in a charge time of approx. 5-6 hours.
If you mount bigger battery you have more energy stored but also charge time for a full charge increases. If you choose an even bigger battery (e.g. 200 Ah) you might not be able to fully charge it in one (sunny) day if it was discharged far enough. That's it.


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phatmatt avatar image phatmatt commented ·
@SnooPV thanks for the response much appreciated.
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pwfarnell answered ·

The charge currents listed are from the point of view of maximum current rather than necessary current. The only thing to watch out for with a lower charging current is the battery SOC will be higher at the end of bulk phase so you should set a lower absorption voltage or have a shorter absorption period or ideally end absorption on tail current.

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phatmatt avatar image phatmatt commented ·

@pwfarnell thanks for the response much appreciated.

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Herb avatar image
Herb answered ·

You should be fine as lithium batteries are much more efficient that lead acid batteriss.


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