Charging cab / engine battery from Solar panel.

barryd

barryd

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Im having cab battery woes at the moment despite a new Bosch cab battery being fitted in August last year. I think my current style of motorhoming might be adding to the problem. Battery is going for testing next week as is the alternator is it was flat after two weeks sat on the front with it connected. Generally I disconnect it when parked up for some time but often when away in the van we drive from A to B and then stay in one spot for several days or sometimes several weeks. The scooter does all the miles so my concern is maybe the battery is never getting enough charge from the engine.

In the summer we have loads of solar charge though and the MPPT controller often shuts down by mid morning so what would be a simple method of putting in a splitter to top up the cab battery from time to time? Its an old van, 1996 Peugeot Boxer Kontiki 640. A job for an auto sparky I presume. I dont want to spend a fortune as I am not sure how much longer we will keep the van.
 
What Mppt solar controller are you using? I have the type Trev keeps telling us all about, and it has an additional feed that goes to the engine battery that supplies it with plenty enough volts and amps. Perhaps yours does too and can be simply hooked up?
 
I use one of these, easy peasy to fit and works a treat!
037D9C6F-7BA7-443D-BFEE-3959889CDD0C.jpeg
 
SimonM said:
What Mppt solar controller are you using? I have the type Trev keeps telling us all about, and it has an additional feed that goes to the engine battery that supplies it with plenty enough volts and amps. Perhaps yours does too and can be simply hooked up?
Click to expand...

PCM2012. Its the one a fair few on here I think installed years ago. Its brilliant. The main issue would be routing cables. No way ill be able to do it.

MPP Solar Inc » PCM2012/3012 Series

www.mppsolar.com www.mppsolar.com



 
Can you follow and do this, middle is relay with a switch, you can wire from regulator or direct from battery to battery with heavey cable if you require a jump start, a 200ah relay is then required, other wise a small relay and lite cable will do fused at each end.
200ah relay.png
 
barryd said:
Im having cab battery woes at the moment despite a new Bosch cab battery being fitted in August last year. I think my current style of motorhoming might be adding to the problem. Battery is going for testing next week as is the alternator is it was flat after two weeks sat on the front with it connected. Generally I disconnect it when parked up for some time but often when away in the van we drive from A to B and then stay in one spot for several days or sometimes several weeks. The scooter does all the miles so my concern is maybe the battery is never getting enough charge from the engine.

In the summer we have loads of solar charge though and the MPPT controller often shuts down by mid morning so what would be a simple method of putting in a splitter to top up the cab battery from time to time? Its an old van, 1996 Peugeot Boxer Kontiki 640. A job for an auto sparky I presume. I dont want to spend a fortune as I am not sure how much longer we will keep the van.
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Simplest place to fit whatever solution you fit is by the Split-Charge system (be it B2B or Relay) as at that point you will have access to Starter +ve, Leisure +ve and a common -ve.

You then have options of a Battery Maintainer (the best option for an automated Fit & Forget solution) or a manual switch to make the connection between the two batteries. You would have to remember to disengage this before starting the engine and make sure it has fuse protection so they blow on the times you forget to disengage it.

Personally I am on the "fit and forget" team as I would never remember to remove the wire or flip the switch.
 
So long as you don’t want to use the leisure battery to give a boost to the starter when actually starting, a relay like the Durite one above or the Cyrix from Victron can be connected at the point where the two positives are side by side on the onboard charger. This what I’ve done and even in winter the starter battery never got below 12.5v without hook up.

Cheers

H
 
Thanks folks but sorry, I'm completely lost with this. Sounds like an automatic system would be best though. What I want is for the solar only to switch to the cab battery once the leisure batter is fully charged but I am unsure what and how I fit that to my existing MPPT controller and completely lost as to how that is then cabled to the battery terminals under the bonnet.
 
None the wiser Kev.

Presumably there is a connection from the alternator to both the cab battery and the leisure battery as it charges both. There is even a meter in the back lounge that shows the current charge of both batteries on a rocker switch. Is it this cabling that needs to be used to reverse a charge through one of these splitter devices?

I think I am wasting everyones time here. Its not straight forward by the sound of it. Which means taking it to an approved motorhome electrician of which I know of none near here. Might be easier just to explore an easier isolation method.
 
No all you do it take a 4mm2 wire from plus to plus with fuses where needed and job done, you pull the fuse before starting the engine, but if you forget it just blows so you carry spares, I fitted a cheap illuminated switch near the ign lock so I could just turn it off, works fine.
 
I lied, first time I did it was on the Laika, I added a LED flashing display in and when the switch was on it lit the display up so it looked like part of the alarm system.


1678897766096.png
 
Pudsey Bear said:
No all you do it take a 4mm2 wire from plus to plus with fuses where needed and job done, you pull the fuse before starting the engine, but if you forget it just blows so you carry spares, I fitted a cheap illuminated switch near the ign lock so I could just turn it off, works fine.
Click to expand...

Take a 4mm wire from where to where though? From the MPPT controller all the way to the cab battery with a fuse in the middle? Surely you need two wires. Positive and negative.

The way I see it in my head is you have the panel, then the controller and currently there are two wires coming out of the controller into the battery. What I think needs to happen (Again in my head) is the two wires coming out of the MPPT controller that did go to the battery now need to be connected to one of these devices mentioned and from that one set goes to the leisure battery one one set to the Cab battery and the new device detects which one needs charging or its capable of prioritising leisure first, then cab. If my thoughts are correct how the hell do you wire all that? Even if I was capable of running two sets of 4mm cable from the back wardrobe to the engine bay and battery would there not be too much voltage drop over that distance? Anyway, no way I could do it.
 
Pudsey Bear said:
from one battery to the other, the drawing explains it all just click the link I posted.
Click to expand...

Right so you wire two cables from the leisure battery back to the cab battery with a fuse you have to take out each time you start the van? That sounds bonkers and a recipe for disaster. Its also a shed load of cabling.

Revert to plan B I think. Just find a better way of isolating the cab battery when I park up.
 
ONE cable they are both already earthed so about 5 meters I'd guess, costs £20 tops if you get gold plated fuse holders, it is dead simple and Barry proof.

why isolate it, when you can charge it? and it will still go flat anyway.
 
barryd said:
None the wiser Kev.

Presumably there is a connection from the alternator to both the cab battery and the leisure battery as it charges both. There is even a meter in the back lounge that shows the current charge of both batteries on a rocker switch. Is it this cabling that needs to be used to reverse a charge through one of these splitter devices?

I think I am wasting everyones time here. Its not straight forward by the sound of it. Which means taking it to an approved motorhome electrician of which I know of none near here. Might be easier just to explore an easier isolation method.
Click to expand...
It is honestly very straightforward.
 
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