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ryan-mulligan avatar image
ryan-mulligan asked

Alternator and solar charging system problem

I have recently added a Victron BlueSolar MPPT 75 /15 and Victron 140W 12V Mono Solar panel to my existing campervan installation. Unfortunately the system appears to have some problems with the leisure battery not charging fully and then performing erratically. I am unclear as to what is happening, what I have done wrong and how to correct it. Help would be appreciated please!


It's a simple, relatively cheap installation as shown below in the schematic. The leisure battery (Expedition AGM 115Ah) is charged from the starter battery using a Votronic VCC 1212-30 battery to battery charger. The loads include a 48W fridge, diesel heater, LED lights, USB chargers and 12v outputs. I calculate the maximum daily load at about 55Ah.

I have recently added solar to allow me to power the system without starting the engine. I calculated that 140W should be sufficient.

I am now finding the following problems:

- the leisure battery never seems to get fully charged - the voltage fluctuates greatly when only a light is turned on. This never happened previously.

- the battery seems to discharge quickly.

I have not used the 'Load terminals', is this a problem? Is it possible that the B2B charger and MPPT chargers 'confuse' eachother as each thinks the battery voltage is higher than reality due to the other charge source? Is it possible that my battery is damaged and is the problem, how do I check this?


Sorry if this is all very obvious and basic but it's all voodoo magic to me. Thanks for your help


screenshot-20220909-221719.png

alternatorsmart solar charging behaviour
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2 Answers
Rob Fijn avatar image
Rob Fijn answered ·

Hi ryan-mulligan, in my calculation... You do not have enough Solar panels.

When using 48Watt for 24h/day (actually fridge has a duty cycle), but you have other loads as well. I come to 262Wp of Solar.

But the best is to invest in a Battery monitor. This is always good to have.

Hope this helps.

Rob

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kevgermany avatar image
kevgermany answered ·

To add.

Solar panels rarely give full rated output. This is achieved under standard conditions that equate to strong sunlight with the panel pointing directly at the light source. When flat on the roof of a campervan, and in less than ideal conditions such as cloud, shading by trees, low sun in winter, a lot less than max can be expected. Battery SOC also affects it. AGM over 80% slows down charge rate. On my camper, I see close to 100% in the middle of the day in the south of Germany. But I'm lucky to get 50% in the UK.

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