question

kubas2021 avatar image
kubas2021 asked

Wiring advice on solar and alternator powered system


Hello,


I would like to ask for second eyes on my van electricity setup, which I’ve been relying on for 2 months.


I’m planning to rewire my electrics according to the hand-drawn diagram (as to gain more space in the van). That involves moving the 2 batteries and their chargers to the engine bay (back of the van) while consumers (incl. phoenix inverter) will be in front of the car (4-5m away). Here are the data, I would be very grateful for any advice and help!


Alternator:

Capable of 70Ah output


Batteries:

  • 75Ah lead acid starter battery
  • 95Ah gel battery from Ective (max charge current 17A, float voltage 13.6-13.8V)


Cytrix-ct 120A:

  • When home battery is at 60% (i.e. discharged by 40%), I get the following data. This is the max rate of discharge I am achieving after cloudy days with weak solar.
  • 14.2V charge voltage
  • 35A upon startup, going down to 20-25A after alternator warms up
  • When battery is at 100% rate of charge, it still takes about 5A while driving. Battery monitor showed max battery voltage of 14.6V (result of alternator + MPPT)


100/20A MPPT charger:

100W flexible solar panel (achieved 64W max)

using gel battery charging preset (14.1V absorption, 13.8V float)


The consumers:

  • 500W Phoenix Inverter (used mainly to power 60W laptop)
  • DC consumers (LEDs, USB chargers, 50W fridge)


The current system raises the following concerns which I would like to address in the future system:

  • Charging gel battery with too high current from the alternator (which goes down as the battery is topped up) - how big of a problem is this for the life span of the battery?
  • Possible overcharging of gel battery when it’s at 100% (i.e. 14.2V at 3-5A even when battery is full)?


Finally, 2 questions regarding the future system:

  • Use Orion-Tr battery to battery charger or is Cytrix-ct a good enough solution which won’t have a drastic effect on the lifespan of the battery?
  • Should Phoenix Inverter have its own dedicated cable runs (positive+negative connected directly to battery) or is it OK to connect it to a positive bus and negative to car chassis? Most diagrams have dedicated cables for phoenix inverters hence my question.


Many thanks in advance, Jakub


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MPPT ControllersPhoenix Inverterorion-tr smartCyrix Battery Combinerwiring diagram
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2 Answers
Jake avatar image
Jake answered ·

The current system raises the following concerns which I would like to address in the future system:

  • Charging gel battery with too high current from the alternator (which goes down as the battery is topped up) - how big of a problem is this for the life span of the battery? This is a rather big problem for battery life. Over/undercharging will damage the battery alot faster then you think. Victron DC-DC Smart charger to fix this.
  • Possible overcharging of gel battery when it’s at 100% (i.e. 14.2V at 3-5A even when battery is full)? there is likely a 3-5A load being drawn at all times hence the "Charge", easy way to check is make sure turn off charge sources and see whats happening to the battery (voltage drop or if you have a wattmeter/BMV somewhere in the system.


Finally, 2 questions regarding the future system:

  • Use Orion-Tr battery to battery charger or is Cytrix-ct a good enough solution which won’t have a drastic effect on the lifespan of the battery? pushing too much current into the battery is a big problem. best to with the Orion.
  • Should Phoenix Inverter have its own dedicated cable runs (positive+negative connected directly to battery) or is it OK to connect it to a positive bus and negative to car chassis? Most diagrams have dedicated cables for phoenix inverters hence my question. this will mostly be a personal opinion type answer, but running the negative back to the battery would be the preference. youve got high currents & multiple charge/discharge devices. I my opinion the risk is lower with the dedicated negative.
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Hi Jake, thank you so much for taking your time for the detailed answer. It all makes much more sense now and I’ll follow your advice :) Dedicated cables + DC DC charger

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kevgermany avatar image
kevgermany answered ·

Go with a dedicated negative.

The alternator is overcharging the house battery, once fully charged voltage should be reduced. Car alternators don't do this. So yes, drop the relay for an Orion.

Look at cable sizes. The inverter feed should be sized for full load (50A). And full load for sustained periods will kill the battery. If I read it correctly, you only have a 4mm cable from battery positive. You'll get a high voltage drop and even with a 35A fuse, risk overheating the cable.



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Thank you so much for the answer! I will go with the DC DC charger despite the cost :)


As for the Phoenix… Sorry if my schema wasn’t clear, the cable will be 10mm thick and 4metres long. Hence my question about a dedicated negative.


So I will run dedicated positive/negative cables to Phoenix and another set for the other consumers - is this the preferred solution?


The 12/500 Phoenix has 3x35AMP fuses so I should go for a 35AMP fuse??

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