3 day off grid electrics and fridge?

[Dellmassive]

1. With B2B chargers who are some 30a, 40a or 50a?is this to cover the combined current from alternator and solar? Or do some vehicles put out a higher current from the alternator?

- bigger charging amps means you can charge bigger battery banks, or charge the battery's faster - especially lithium. the number is the MAX the charger can delivery.

for example a 20A DC-DC charger will charge a battery at 20A MAX - but the vans Alternator is 140A/180A max.

++

For SLA / AGMs its recommended to go for 10-20% capacity for charge rate.

so for a 100Ah AGM battery look for 10-20A charger . . . (10-20%)

BUT . . . if your running your camper loads ontop then add this too. . . so if you van is using 10A for camper loads, add that ontop of the battery charger amps.

so 10-20A for charging Plus 10A for camper loads = 20-30A dc-dc unit.

you you dont do this you loads will use power and reduce the charge available to the battery meaning it will take longer - in the above case twice as long.

++

each charger (combined) works differently, regards to max power share, some will prioritise the PV solar (Redarc), some will be a 50/50 split (Renogy) . . . others will just mix the two (CTEK) - but only up to the MAX the charger can deliver.

 

[Dellmassive]

Do I need the same cables as VSR.

- yes/no

you need the cable and fuse set that is suitable for the charger / VSR with a 50% margin (best practice) . so if you are looking at a 20A charger - then get a cable set capable of running twice the power . . so 40A cable set.

you can then down rate the fusing to protect the cable set at say 30A

...


so for a 20A charger,

get cable set for 40A max,

fuse at 30A,


........


that will give you best performance and be long lasting without stressing the install,

 

[Absolut5]

Some T5.1s have smart Alternators.. best to check first

 

[Dellmassive]

2. Will an MPPT or any of these B2B's tell me the charge state of the battery or do I need more kit for that? Ideally I'd like to be able to see the draw of the compressor fridge.

- no,

you need a battery monitor for that . . . . there is no way of the charger knowing the battery SOC.

some will give a rough idea based on the battery voltage . . . but its a rough guess and wont tell you what your fridge is drawing . .


look at the current shunt style battery monitors.


OR


get a lithium battery that has that feature built in . . .

eg:






..


more info here:

Battery Monitoring -- How I Done It --

Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...

www.t6forum.com

.

 

[Dellmassive]

Some T5.1s have smart Alternators.. best to check first

very true. . . the late T5`s with stop/start feature smart Alts

 

[Dellmassive]

example shunt style monitors:

SmartShunt - Victron Energy

The SmartShunt is an all-in-one battery monitor, only without a display. Your phone acts as the display. The SmartShunt connects via Bluetooth to the...

www.victronenergy.com

https://amzn.to/33zCbtC

...

500A Battery Monitor with Shunt/Sampler (Coulomb meter)

Renogy 500A Battery Monitor is able to monitor the amperage flowing out of the battery bank and will give an accurate state of charge reading on the LCD screen.

uk.renogy.com

Renogy 500A Battery Monitor, High and Low Voltage Programmable Alarm, Voltage Range 10V-120V and up to 500A, Compatible with 12V Lithium Sealed, Gel, Flooded Batteries: Amazon.co.uk: Electronics & Photo

Shop Renogy 500A Battery Monitor, High and Low Voltage Programmable Alarm, Voltage Range 10V-120V and up to 500A, Compatible with 12V Lithium Sealed, Gel, Flooded Batteries. Free delivery and returns on eligible orders.

amzn.to

...

CAMWAY Battery Monitor 8-100V 0-350A Voltmeter Ammeter Voltage Current Meter Backlight Waterproof Auto Car Motor Boat Caravan RV Motorhome,etc : Amazon.co.uk: Automotive

CAMWAY Battery Monitor 8-100V 0-350A Voltmeter Ammeter Voltage Current Meter Backlight Waterproof Auto Car Motor Boat Caravan RV Motorhome,etc : Amazon.co.uk: Automotive

amzn.to

 

[Scottiec33]

@Dellmassive @Absolut5 Thank you so much. Unbelievably helpful in such a quick time with answers I've haven't been able to find so far. Feel confident to crack on now.

 

[Skyliner33]

@Dellmassive @Absolut5 Thank you so much. Unbelievably helpful in such a quick time with answers I've haven't been able to find so far. Feel confident to crack on now.

This is the help @Dellmassive and others offer. Maybe consider becoming VIP member, small price for the effort and time put in with help and advice

 

[Scottiec33]

This is the help @Dellmassive and others offer. Maybe consider becoming VIP member, small price for the effort and time put in with help and advice

Done!

 

[Phil_G]

Sorry to repeat this but we see frequent requests from people who are on a very limited budget and usually the first recommendation is an expensive B2B like a Ctek 250 etc. It must be discouraging to be told that its absolutely necessary to spend another £300, and that nothing else will do. Our personal situations differ widely, you only have to look at the mountain-bike section to see that
But leisure battery charging can be done on a budget.
For around a tenner you can buy a 60 amp ideal diode from ebay, Bangood, AliExpress etc - an 'ideal diode' is effectively a diode with no voltage drop.
Its a high-current mosfet which switches fully on or fully off according to which direction the current is trying to flow. As you'd expect with a diode, it prevents the leisure battery from providing starter motor current, whilst allowing charge current from the alternator in the other direction.
A much better solution than a relay at a fraction of the cost.

Similarly you dont need an MPPT controller if you're on a tight budget. Yes, under most conditions they perform better than (wrongly-distinguished) PWM controllers (mppts also use pwm). I say under most conditions, at low light when the solar panel voltage is down to say 15v most MPPT controllers would have switched off, whereas a 'PWM' keeps some currrent flowing right down to the battery voltage. Again a cheap 'PWM' controller gets you going and is really very easy to swap out as & when budget permits.
Again, sorry for the repeat.
Cheers
Phil

 

[Pedro20001]

I would consider one of these which you just connect to your leisure battery as required. I have one and it’s brilliant.

100 Watt 12 Volt Foldable Portable Solar Suitcase Monocrystalline with Waterproof Charge Controller (G2 Version)

Renogy 12V 100W Portable Solar Panel is an entire solar power system incorporated into a single, compact package with a waterproof charge controller.

uk.renogy.com

Thats good to hear, I've just bought one today