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izzy010568 avatar image
izzy010568 asked

LifePO4 doens't get to absorption on solar

We have a Victron EasySolar 24/1600 with an MPPT 100/50 in our truck. We have 600w of solar on the roof and 400ah of Chinese LifePO4 (made up of 4 x 200ah 12v batteries wired in series then parallel to make 2 x 24v banks).

Unless we use shore power, we are unable to get to more than around 26.8v. One day at the height of summer last year after driving for about 5 hours (we also have an Orion fitted) we managed to reach absorption.

Absorption voltae is set at 28.4v per manufacturers instructions, and float at 27v.

We recognise that the solar on the roof is inadequate and imbalanced with the battery bank (long story about why and not really relevent) so have been looking at fitting more solar. This is proving difficult because of space.

We run a fridge, a couple of macbooks, toilet fan, water pump - the usual van stuff. So we thought that we would disconnect two of the batteries, i.e. one of the 24v banks. We expected to reach absorption, but still only got to around 26.8v by the middle of the day, with the solar pulling in around 250w (1.5kwh in the day). We're in southern Spain in early Feb.

We're now totally confused and are wondering if we maybe have another issue. My question is really whether 600w of solar is sufficient to fill 200ah 24v batteries, or do we have another problem somewhere? Could there be an issue with the MPPT? We don't even know where to start troubleshooting this.


EasySolar All-in-One
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2 Answers
jeanmarie avatar image
jeanmarie answered ·

In case you are unable to load more the batteries, it usually means that the consumption is higher than the production.

Now you have to investigate what are the daily consumption and production to determine if my guess above is correct or not.

You can also check after your daily production to see if it is consistent with the installed power. In theory 600W, flat, a sunny day of February you should get above 2kWh, if not then it could mean you have an issue with one of your panel.

And with such a production, to refill totally your almost 10kWh of LFP batteries, keep in mind you will need several sunny days


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kevgermany avatar image
kevgermany answered ·

Disconnecting one pair of batteries simply means the loads are handled by the remaining pair, so no surprise that charging behaviour didn't change.

You either need to reduce consumption or increase supply.

If you can, shut the inverter off unless it's needed. In any case unplug all phone/laptop chargers unless you're charging. The standby draw is significant.

Switch AES on in the inverter with a min load setting of about 30W. Otherwise AES won't work, unless you're on old firmware.

If your alternator can handle the load, add an extra Orion or two in parallel.

Let the fridge run warmer.

Consider swapping the panels for ones that give better performance under low light levels. I think these were from Panasonic, but they went out of production and rights have been sold to another company who are/have restarted production, I can't remember more.

I've a very similar setup to you. In winter, no loads, the panels will barely keep the batteries charged with no load on the system, inverter off.



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