Wiring confusion and panel consideration

[Howmanygoes]

So auto electrical guru's

I had solar 100w on previously into my CTek 250sa.

I now have a new RTT coming which is prewired for 300w solar. The instructions say to ensure regulator can take 45v that a 300w panel produces

My previous cable was 4mm2 "solar"

I have some 6mm2 thin wall (53a) and planned to use this due to the run required.

My CTek has an input voltage, max open circuit solar panel voltage of 23v

So my questions

Will the 6mm be suitable without the extra insulation that the "solar" cable provides.

Will I need to buy a new mttp controller?

Should I choose panel first and work backwards.

Cheers in advance.

 

[goodoldboy]

Should I choose panel first and work backwards.

Size the battery first .Calculate your consumption & then think about how many days/ hours you would like in reserve without sun , driving or hook up A battery sized at 50% depth of discharge (DOD) will last a long time E.G. A high quality 150ah battery will give 1200 cycles. Having said that weight is a consideration .Also are you planning a long trip or just occasional use ?

Will the 6mm be suitable without the extra insulation that the "solar" cable provides

it's not the insulation it's the cross sectional area that counts. this link should be useful

My CTek has an input voltage, max open circuit solar panel voltage of 23v

... what you would expect in a system that's 12 V

Will I need to buy a new mttp controller?

On such a small system I wouldn't bother .The claimed high gains - up to 38 % - are calculated around a highly discharged battery and low temps , lees than 20C with full sun . Fully discharging the battery should be avoided (see above . the cycles Vs DOD scale isn't linear , an 80% DOD dramatically reduces the life of your battery ) . A 8 to 10 % is about average and unless you're in a rush to quickly charge it's not worth it IMO .
hope this helps

 

[Howmanygoes]

Thanks

I already have a 130ah AGM leisure battery, which runs,
Fridge, a few led lights, waterpump, compressor cb, rtt and a few USB sockets

I've been using this set up for about 18months supported by a 100w solar panel.

What I was considering doing, as I need to buy a new panel, is upscalling to cover future power demands and speed up rate of charging.

My question about cable was the use of non pv in the system, some YouTube say you must use pv/ solar cable. I agree cross section is key as is full copper or tinned copper.

The 23v max of my ctek unit appears to reduce the options on panel sizes to me, where as if I installed I.e. a victron 100/20 I would be able to use eg a 270w panel just keeping the ctek for the dc to dc capability.

 

[goodoldboy]

some YouTube say you must use pv/ solar cable

Good idea . This type of cable is UV safe and more resistant to high & low temps.With the short run it' shouldn't make much difference on price.A 100 W panel is a bit small for a 130AH battery as you'll see 8A max - if the panel is at the ideal angle & orientation .As for the DC -DC charger the amps might be the limiting factor not Volts.