Computer on the Wasp

[Bongolia]

Evening all..
I want to run a small Summvision cyclone mini pc in the Bongo, it has a voltage input from the mains transformer of 12V @ 1 amp.
I need to know what precautions I should take in order not to cook it!
I am thinking that I cannot just run it fused straight off the battery.
Any pointers gratefully recieved.

[g8dhe]

Quite correct!
12 volts is just a "common" voltage used for many goods (along with 5 volts, 3.3 volts etc) the conjunction with people thinking that cars run from 12 volts can lead to some very sorry results The voltage range for car supplies can be from 10 volts to 15 volts with some massive power spikes thrown in for good measure !

You may be best using the mains power supply that I suspect it comes with which will give the required regulated 12 volts, and then either use it from the mains EHU connection or use an inverter to go from the car "12 volts" up to 230 vac mains. I suspect for such a small PC the power requirements might well be quite small most likely well less than a 100 Watts for which there are quite a lot of choices to choose from like for instance https://amzn.to/2MsDRbv - this isn't my usual recommendation but going from 12 volts car to 12 volts regulated can be a problem as sometimes you need to boost the voltage and at others reduce (buck) the voltage which makes for added complexity, hence its easier and cheaper to use standard devices rather than specialist answers!

[mikeonb4c]

Thats interesting Geoff. Am I right in saying you're only discussing direct power supply connections? I bought a 12v cigarette socket lead off ebay for my laptop. Is this safe to use? I'm imagining the lead charges the battery from which the device draws power, so that the battery offers buffering to voltage spikes, but i'm no leccie so would welcome correction.

Bongolia - great to see you on here. I'd been wondering how progress was going with the Wasp. Is it now sorted and on the road?

[g8dhe]

Most Laptops don't use 12 volts they range from 18-23 volts so you get a mains power pack with them to go from 230 vac to the required dc voltage, or you buy an inverter that takes 12 volts dc input and either a fixed or adjustable output voltage to suit your machine, a lot come with "tips" that match the right socket and set the voltage at the same time for the specific laptop;

Devices like the above are designed to handle the wider range of voltages 10-15 from the car and also can handle the spikes to much higher voltages.

Laptop designs vary but normally the incoming power at 18-23 volts dc supplies the computer directly and also charges the battery, the battery doesn't normally act as a buffer, once the internal circuitry sees that power from the external source has gone or is insufficient then it will bring the battery on-line as well. The reason for this is that lithium batteries need to be carefully charged, the internal battery temperature is measured and the charging voltage set accordingly as well as current limiting taking place, if the charger is also supplying the computer power as well it can't tell the difference between what current is being used to charge the battery and what is being used by the computer itself.

This is the same problem with using "smart/intelligent" battery chargers for supplying the internal 12 volts around a van as well as charging the battery. The intelligent chargers can't tell what is going to the battery and what is being used to run the internal lights / TV / phone chargers and everything else plugged into the 12 volt sockets! Hence they can get themselves in the wrong mode when you turn on/off devices. When a Smart charger is first switched on it starts by watching the voltage on the charging leads, without supplying any power, it then decides what voltage battery you have 6/12/24 (in some cases) when the voltage is stable after a couple of seconds it then turns on charging using the correct voltage level, normally with a Maximum charging current limit set according to the rating of the charger itself, it then monitors the voltage across the battery and starts a timer as well, once the voltage on the battery starts to rise it will limit the voltage according to the initial voltage so for as "12 volt" battery it will set a max voltage of 14.4 volts it then supplies power at less than the current Max and voltage Max for either a given period typically 8 hours or until the battery voltage wants to rise above the Max limit, at that point its "intelligence" assumes that it has reached about 80% of full charge, it then continues to charge for 1/5 th of the time it took to get to that point, this is the levelling charge which gets the battery and all of its cells to the a fully charged state at the end of this time period it drops the voltage to 13.6 volts or a low current level around about 0.2-1.0 Amps this is the float charge stage, which can continue indefinitely. You can now see that if not all the current is going to the battery itself but is being used to run a radio/tv/dvd/lights in the van the charger has no idea about this, it just thinks the battery needs to charge for longer, then if you turn the TV etc off the voltage suddenly goes up and the levelling charge starts to take place accept the timing is now totally wrong at this point the charger can be said to have a negative intelligence

[mikeonb4c]

Wow! Now THAT is an answer. Thanks Geoff and v interesting and thought provoking indeed to read how so called intelligent chargers (don't!) work. Maybe there's something to be said for lead acid batteries and simple chargers (with a human using some sense over when to disconnect)?

[Bongolia]

Well now I know. I feel a bit uneasy about stepping up the voltage with an inverter just to bring it back down with a charger/adaptor, I see on that link 12v regulator although these are 30w items if I could source something with a higher wattage would they not do the trick?

Mike. Wasp has been on the road and in regular use up and down the M20 since Feb. The interior is not fitted out yet as it has been used for building materials and carting furniture.
I ended up spraying it with Black (actually looks very dark brown when next to the other panels) aerosols. Not the best but gets it usable. No major issues at all so far apart from odometer not working, a cracked screen and a bit of vibration around 60ish but goes at higher speeds.What I do need is a Bongo friendly garage to sort out the slow ATF and fit a new tent anyone know of one near Rye or along the coast I dont mind a drive?

[mikeonb4c]

Well now I know. I feel a bit uneasy about stepping up the voltage with an inverter just to bring it back down with a charger/adaptor, I see on that link 12v regulator although these are 30w items if I could source something with a higher wattage would they not do the trick?

Mike. Wasp has been on the road and in regular use up and down the M20 since Feb. The interior is not fitted out yet as it has been used for building materials and carting furniture.
I ended up spraying it with Black (actually looks very dark brown when next to the other panels) aerosols. Not the best but gets it usable. No major issues at all so far apart from odometer not working, a cracked screen and a bit of vibration around 60ish but goes at higher speeds.What I do need is a Bongo friendly garage to sort out the slow ATF and fit a new tent anyone know of one near Rye or along the coast I dont mind a drive?

Great to hear the Wasp is on the road, and with so much bodywork sorted here's hoping the rest gets brought up to scratch ok. Cant immediately think of a Bongo breakers down that way - might need a trip to somewhere like Bongo Spares. Apart from the usual diy servicing, new motors are what sorted my AFT, but not cheap.