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4 season RV solar system batteries in series or paralel? -12V or 48V

I want to plan a solar system for Mercedes Sprinter or other converted RV.

On the roof can be mounted 3x solar panels in my oppinion (+vents) for Medium Wheel Base (MWB) and 4x solar panelson a Long Wheel Base (LWB) or even Extended Long Wheel Base.

Similar is the simutation for Fiat Ducato, Citroen Jumper, Peugeot Boxer, Iveco Daily, VW Crafter.

Those solar panels, will have enough power to fill up 2x or 3x battery, probably gel or agm, with 100Ah or 200Ah ( depends on the budget) .


I suse at AT DIFFERENT car a vacum cleaner 1400W and with a 2500W not sinus inverter (not from Victron) It is very handy to clean up my car! Also used a 750W angle grinder, a 700 or 900W rotary hammer and so on. Now it seems I can't handle those devices that inverter which are using 1700W from pure sine wave and all this powered from my running engine : 14.4V and 55AH battery and a small alternator: around 90A. But it is just great to have tools to repair your car or do some mobile workshop jobs ocasionally.


I would like to use a coffe machie: around 1400W-2000W usually, maybe a washing machine 700-1200W, maybe ironing, instant cooking around 1500W , so 2000W sine wave it would be enough, but 3000W for sure and not need huge capacity, just around 3000Wh, that could hadle propably a pizza cooker too. At 12V battery it means: 3000 / 12 = 250A battery. ( but no less). So 4 x 200Ah for sure it is enough and 2 x 200 A h for sure not if I use a high end laptop min 8h /day ( around 640Wh/day)


The Mercedes Spinter has an option to buy it with 190A alternator, but about other vans I am not sure. 190A x 14.4V => 2736W charging power at max. To fill up the 3000Wh with losses propably it would take 1.5h, max 2h running on idle or drive mode, which is fine for me.


As we know in the winter we have fewer sunny days, and a lot less, fewer daily hours and even less usable hours for charging. Maybe 2 or 3h in a good day? And solar panels can have 10-15% of they max power, so I must use the alternator charging mode at the base. (3x solar, at 15% of 270W x 3h = 364Wh)

There are 2 possibilities on which I am hesitating: connect batteries in paralell: 12V or in series 36/48V?


If I do in paralell 3 or 4x batteires I have to do the same with solar panels, I think, but for sure I need to have battery balancer ( how many do I need and how much they will costs?). I am not sure how good are those batteries connection for 4-5 year for sure one of they will be weaker than others and we be an internal consumer. Havinig it in paralel I neep the 12V, but that means it is required to have wider cables, much more heat production and much more risk to fire. I know there are fuses and you know those can fail, like any electrical equipment. The advantage of paralel connection it would be easier to charge from the alternator.


If I do the connection of batteries in series I will have 36 or 48V and lot less Amper, lot less diameter of cooper wire needed to use, lot less heat, of course solar panels would come also in series. The backside of this now the alternator can't chage it, need a DC/DC converter from 12V to 36V or 48V. - which I don't know how much does it costs again. Other thing it is if I want to use a device projected for camping, hence 12V and in rare case 24V I can't, because I have 36 or 48V. For example a 12V water pump probaly is needed for sink or maybe others to fill up the water tanks.


I think that pure sine inverter of 3000W willl be an expensiever item, and for that should be easier to work from 36 or 48 compared to 12, hence should be cheaper again (with something.)


So how is better technically to connect those batteries in my case and which is cheaper with how much?


As I how I see the prices:

Victron Energy MultiPlus 3000VA 12-Volt Pure Sine Wave Inverter 120 amp Battery Charger: 1284 usd

Victron Energy MultiPlus 3000VA 24-Volt Pure Sine Wave Inverter 70 amp Battery Charger, UL-Certified: 1427 usd, so surprise: this is the expensiever one with a few percent.

(it seems this inverter has the charger part too!)


Victron Battery Balancer: 65 usd


Or should I use a 24V system instead of 48V? according to this: https://community.victronenergy.com/questions/41792/how-to-charge-a-48v-system-from-a-12v-vehicle-alte.html

Or simply use a different 230V generator and no solar panel at all? - https://www.eevblog.com/forum/chat/48v-alternatorgenerators-for-automotive-use-do-they-exist/


Somebody put an inverter to alternators and made from 12V the 230V and on that way charged the 48V: https://community.victronenergy.com/questions/71403/charging-48v-batteries-from-alternator.html

So many requests for 48V, I don't undertant why Vicron doesn't offer a solution! Should I make it? :)


I just found out it is a 6V battery with 240AH from Victron, connecting in series it will be 24V bus!

Even more: https://community.victronenergy.com/questions/76200/gel-agm-hybrid-batteries.html

Phoenix Inverterdc dc convertersBattery Balancer
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1 Answer
offroadflow avatar image
offroadflow answered ·

Whatever all your millions of details I honestly did not read, regarding to the batteries I'd connect all batteries in parallel SINCE YOU HAVE A 12V SYSTEM on board.

Else you need DC/DC converters and a lot of understanding about electronics.

Adapt with what you have...

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