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qwakers

it was requested, so here it is, the race-lorry build!

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Ignore the solar b*ll*cks, expensive controller is never going to pay for itself, £20 eBay MPPT jobby would do you just as well.

Mind you, unless you're using a lot of electric the existing panel + any old controller should do fine. I see your fridge is gas so that's one big draw you don't have.

Been through all this with the ambulance, there is so much bullsh... in the solar world it's unbelievable.

Rule of thumb: your 100W panel will, on average, put 10W/hour into the battery over any given 24h period.

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This is the style I've used; if you're not wiring your loads through it you only need it rated to the panel's max output, so for your 100W panel a 10A one is plenty good enough unless you are friends with Elon Musk and he offers to launch the truck into the sun:

https://www.ebay.co.uk/itm/163251911524

On the ambulance we have 2 of your panel and 2 of these controllers, but we burn more electric because the fridge is 12v-only and the 2nd battery is relatively small.

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On 11/7/2018 at 6:49 AM, FridgeFreezer said:

Ignore the solar b*ll*cks, expensive controller is never going to pay for itself,...

Until the cheap price of carp cooks your battery or catches on fire and burns your truck to the ground.

Edited by Red90

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7 hours ago, FridgeFreezer said:

This is the style I've used; if you're not wiring your loads through it you only need it rated to the panel's max output, so for your 100W panel a 10A one is plenty good enough unless you are friends with Elon Musk and he offers to launch the truck into the sun:

https://www.ebay.co.uk/itm/163251911524

On the ambulance we have 2 of your panel and 2 of these controllers, but we burn more electric because the fridge is 12v-only and the 2nd battery is relatively small.

too high risk, most of them aren't mppt... ive already got a cheap pwm controller so if i upgrade i want to be sure what im getting...

 

 

 

 

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That guy in the video doesn't know the difference between PWM, MPPT, buck/boost regulation, and a hole in the ground... he also doesn't seem to understand the control schemes of any of the various controllers he tests.

MPPT controllers still use PWM to regulate the charge, MPPT is just a smarter control scheme and that STM32 micro is more than up to having an MPPT control scheme in it.

Anyway - I realise the cheap ones are cheap, but in response:

  • That's why our setup has many fuses (in & out of both controllers)
  • MPPT makes very little difference unless you absolutely must get every last bit of power out
  • Many of the expensive ones are not provably any better (they wax lyrical about them in the marketing but are light on technical deets)
  • I've had them apart and they're not horrifically badly made
  • They've worked fine for some time now
  • Given they're rated for 10/20/30A and your panel will never pass 5A, you've got a fair safety factor
  • These ones at least show you some vaguely useful info for your £20, expensive ones tend to have a couple of blinky LED's and that's it. £20 doesn't buy you a dashboard battery gauge these days.

If you weigh the difference between a £20 eBay one and a £200 CTEK, you might gain 10~20% performance with real MPPT (assuming the eBay one isn't MPPT) - for a 100W panel that's <24WH/day. If you really need that extra ~20%, spending some of the £180 difference on a bigger battery (or a pair of batteries) is going to be waaaay better value - every time you move, your alternator will dump way more juice back into the battery than your panel can manage, and with only lights, water pump and maybe a webasto to run even a small 100Ah battery will last days with a basic 100W panel + cheap controller topping it off.

 

dual_controllers.jpg

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im never going to spend 200 on a controller 😂

and id disagree that hes clueless, he might have got two points materially wrong but the one point he makes is that it IS missing componants that it HAS TO HAVE to make it mppt, so at best its a pwm, and at that price, an expensive one. the result of which, im happy enough with the £8 pwm controller already fitted!

if your setup works then great :D i was just mulling over the idea of changing to mppt, and have decided not to bother.

 

 

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No, he's wrong about exactly that - MPPT does not mean it would have ANY extra components, he's thinking of a buck/boost switch-mode power supply which is sweet-fa to do with MPPT.

MPPT is a fairly simple algorithm where the controller moves the "balance" of load on the solar panel to achieve peak power transfer into the battery (like changing gears to keep the engine in its power band), which his video does precisely NOTHING to prove in any of the odd ways he goes about his "tests".

The STM32 microprocessor fitted to the "cheap" unit is more than capable of doing MPPT stood on its head, and it would take longer to program the display routines into it than a basic MPPT routine.

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dso sunday i got a fair amount done on sunday

 

replaced the solar panel, now charges fine. remains to be seen if the controller prevents it discharging at night.

 

fitted the shower tray, the waste, and glued it down. just got the trim it out around the tray, fit the toilet and fit sink and shower head.

 

trimmed the corners of the walls to clean up the carpet edges, used black plastic angle and superglue. looks good from here :D

 

the old solar panel ocv was only 14v, the new one is 21v, so in low light levels it would pull down to 11v and thus discharge the batterys. the new panel doesnt, so all is well there. dont know weather thats a fault or just a carp panel.

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19 hours ago, bishbosh said:

Oi Mr Fridge, that's my avatar you've pinched! :hysterical::)

To be fair though at least we can now share the joke, ....... it was limited to those with 40/20 vision before:blink:

  • Haha 1

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On 11/13/2018 at 12:41 PM, bishbosh said:

Oi Mr Fridge, that's my avatar you've pinched! :hysterical::)

To be fair, it went walkabouts from XKCD in the first place...

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