I’ve got a small campervan , is a Toyota Alphard converted , long story short , the conversion people are basically butchers , they wired up the fridge to the main battery and this morning I found the battery flat .
Does anyone have any experience with battery protections ? I found something on Amazon but doesn’t look like able to deliver 20A .
I would build one but the Van is shared and I can’t afford to fuck this one up.
Lead acid battery voltage drops as it discharges and then starts going up again as you kill the battery.
So all you need is a cemos compariter with a bit of positive feedback and a voltage ref to disconnect the battery before you hit secondary discharg
My idea was that if the battery goes down once , then it will need a manual override to restart , do, it doesn’t matter if the voltage comes back , without human intervention cannot restart.
But again , I would love to find a ready made solution , because I share the van with non technical people , something that can be replaced if broken .
I can’t find my h&s training manual but the cut off voltage should be about 11 v
It should be noted that most batterys dont do the primarily discharg thing so much any more
As soon as the voltage comes back up its normal to let the contact er back in as the charger shood be abel to carry the load .
let me think about it and will come up with something
Easy use that model to release a nvr
Add a realy and a button to thst module and you are good to go
Can you stick a solar panel on the roof to trickle charge the battery?
We don’t do that EU solar nonsense anymore.
This is England if it its not coal powerd its unpatriotic
I thought about it but I would need a power inverter , and the system is complicated by itself.
All of this without counting the aerodynamic pressure , you get it wrong and after 40 miles per hours the panel finishes like the Shuttle Columbia…
Are you putting in a second battery for the fridge etc?
No inverter required.
That could be any load
Put it in a window
It is there , but the two are connected in parallel.
That is not going to help if someone leave the fridge on all night.
Yes it will . i will have to show you when I see you with a drawing
Normaly done with a split charging
Yes, you need a battery isolator, or split charging relay. There are a million off the shelf units built for this purpose, choice depends on alternator output etc… Take a look at this:
Either way the fridge should be wired to the leisure battery and not the starting battery.
I have built my own campervan before from scratch so dealt with all these 12v issues. I also have a VW T25 Westfalia now, if you want someone to take a look at how it is setup, let me know next time you bring it to the space!
Cheers,
Andy
That would be great , first I have to find how the F take the battery out from his housing 
As Andy says you need a split charge system with a second, ‘leisure’ battery. However, if it is a very modern vehicle with stop/start and regenerative braking then it gets even more complicated.
I’ve always wired my vehicles with a simple 1-2-both-off type switch.
Simpler and more rugged, plus I can start from the leisure battery if I need to, just charge the main battery first if it’s only a short run.
Easier wiring too.
Plus you can isolate the battery if you ever need to.