Additional solar system & B2B for compressor fridge

I don’t have anything but I use a battery monitor to let me know what state my battery’s are in. I don’t really have big start up loads, highest is Eberspacher at around 6.5 amps, I don’t run a big inverter though, got a 300w jobby for occasional use if I want to charge MacBook but that’s it. Mine is just spread across the 24hr period
 
Oh, I was confusing myself :) I was thinking of the big 240 volt startup surge of the fridge, but the inverter would smooth that out a bit.

Yes, I kept watch of the voltage manually via the display and just cut down on consumption when low. The thing I was worried about was running the fridge overnight if the battery was low and waking up to a dead battery due to the fridge. Cheaper to cut the fridge off than have to replace the battery. Once you got to know what the fridge would use overnight, you could make the decision to turn it off if necessary.
 
Solar layout.png


Here's the layout I have now with the second system added. The red boxes are the leisure batteries. The front, existing one (A) under the passenger seat (it's LHD). The existing solar panels are in black. The skylights/vents in green. The new solar panels in blue.

I had thought to mount them on the front sloped section above the cab, so you could park straight into the sun for slightly better solar yield. The panels I use are about 1200x550mm (100 watt). There are some others about 1000mm square (150 watt) and 2 of them might go in that space on the front. Decided against it as it would look a bit ugly and I wasn't sure of the fit.

The Electroblock (EBL) is in the front right corner.

The existing solar controller is mounted on the side of the drivers seat base (between the seats). The display is next to the Truma control on the front wall of the wardrobe which is on the left of the vehicle between bathroom and desk.

The fridge is in the rear, right corner. I thought best place for the second leisure battery (B) is under the couch (sofa) seat. Run the solar cable down the wall behind the curtain and the solar controller and display up on the cupboards above or next to the original Hymer control panel above the rear door. Or I could put the solar controller down on the kick panel under the couch.

Main thing is the routing of cables. Solar -
1. 10AWG Solar panel cable from 2 panels on the roof to the controller. A double adaptor on the roof to join the 2 panels. I was thinking of putting another double adaptor under the couch, so I could have a lead to run outside through the locker door under the couch to the portable solar panel outside (if I need it). It might run through the gap when the locker door is closed or maybe it would need to be left open, or possibly some kind of socket under a flap on the outside wall?

2. Controller to leisure battery (B) cable.

3. Leisure battery (B) to inverter (also mounted under the couch).

4. 240 volt cable to fridge - can run through the cupboard, along the floor next to the rear door.

5. Solar controller to its LCD display - back along the solar cable route to wherever I choose to mount the display.

6. Leisure battery (B) - to chassis/body.


B2B charger -
This can be wired in various ways, one of which is to the EBL, but I'm not doing that as it's purpose is to charge the fridge leisure battery (B). I did toy with the idea of putting in a dual circuit with a switch so I could choose either leisure battery system to charge, but that's too complicated.

As this will be carrying 20-30A over about 3 metres it's going to need a hefty cables. I know I can get through to the starter battery (which is in the extreme front, right corner) under the dash in front of the passenger seat. The B2B has a display which I thought I might put near the drivers seat as it'll be on while driving. There's room to the left of the driver. I think I'll mount the B2B on the face of the cabinet the Electroblock is in (to the right of the passenger seat). Nope, needs to be closer to the leisure battery (B), so back under the couch.

1. 6mm (maybe 10mm) + cable from B2B through the firewall to starter battery + terminal.

2. 6mm cables (+&-) from B2B back to leisure battery (B).

3. LCD display cable from B2B to the display near the drivers seat (if it reaches).



Fuses (placed nearest the second item) -
1. 40A fuse between solar panels and controller. I use a circuit breaker which makes it easy to turn off the solar panels if required for work.

2. 40A fuse between controller & leisure battery +

3. 50A fuse between B2B and starter battery +

4. 40A fuse between B2B and leisure battery (B) +
 

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Personally I'd use 10mm2 cables rather than 6 they're not that bulky and the improvement in voltage drop will be significant at 20-30 amp flows.
 
Yes, probably. I was thinking I could just use excess 10AWG (6mm) solar cable, but maybe it's not the right sort of cable (besides the thickness).
 
Nothing wrong with the cable as such but area is king when charging. The panels are of course running at a higher voltage so currents are lower upstream if the controller.
The firm that must not be mentioned make the point that probably the thing that makes commercial B2B work is that they recommend large cables - which if used on their own with a relay would probably be just as effective!
Thin wall cables are just that.
 
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Will have to read your post again when meds have kicked in and it sinks in a bit. One thing if you are going to use a Votronic Duo and want to use the trickle feed to starter battery you can just run a cable from Bat II to starter + on the EBL, it does show that in instructions for the MPPT.

on mine in used the Votronic B2B and I could just cut in (piggyback) on the wiring to the EBL and just needed a cable to run leisure battery bank. A previous owner moved battery location from an outside locker to under one of the bench seats so apart from the spaghetti junction of cables they left it’s quite easy to add/modify thankfully.
 
The difference for this system is its separate from the existing setup, so not using the EBL. I already have the starter charge running from the existing Votronic. I won't change that unless I find the second setup has excess, so I could change the starter charging to it.
 
You could use the 1 amp trickle to go to the other leisure bank if you wanted. It takes that 1 amp off the total harvested though so depends where it’s most needed
 
Another battery option using lead carbon. Sounds ideal for leisure battery use - great cycle rate, fast charge, seems temperature tolerant (though I can't find any figures to state the effect of high temps on it), tolerates deep discharge well. Expensive, but not as high as Lithium. I'm not sure why Alpha are calling it an AGM battery as the manufacturers don't.

PLH+C Series-Pure Lead Carbon Battery

Advanced pure lead carbon battery, long life and high performance
www.leoch.com www.leoch.com

www.alpha-batteries.co.uk

12v 100AH Leoch Pure AGM Lead Carbon PLH+ C100 Deep Cycle Leisure Battery NCC Class A - Alpha Batteries

12V 100Ah Ultra Deep Cycle battery for multiple applications – from Leoch’s Pure Lead Carbon series. Features • Pure Lead […]
www.alpha-batteries.co.uk www.alpha-batteries.co.uk

Found a test comparing it to Lithium and lead acid
 
Isn’t it carbon Dave it running? If so they are very heavy I believe so check that if Wright May be an issue
 
31kg for a 100Ah, a few kg heavier. Not so bad if you think of it in terms of 'kg per usable Ah'.
 
wfdTamar said:
31kg for a 100Ah, a few kg heavier. Not so bad if you think of it in terms of 'kg per usable Ah'.
Click to expand...
Think Dave’s are twice that weight so may be some other type
 
Very impressive demonstration of the difference tilting can make with low sum even in quite "watery" light.
 
How much you got up there Jeff, I am currently getting 1.3/1.5 amps off my 300w?
 
Exwindsurfer said:
Thought I’d make use of the sun now .the panels where flat on roof and putting 3amps in so I decided to tilt them up and got this View attachment 52085View attachment 52086
Click to expand...
Have you got any kind of safety strap that will stop a big gust pushing the panels over fully vertical and just over?
I would be very nervous personally of having a near-vertical "solar sail" with just a pair of struts keeping it in position :oops:

EDIT. I just made out a wire in the middle! Phew :D
 
wfdTamar said:
Another battery option using lead carbon. Sounds ideal for leisure battery use - great cycle rate, fast charge, seems temperature tolerant (though I can't find any figures to state the effect of high temps on it), tolerates deep discharge well. Expensive, but not as high as Lithium. I'm not sure why Alpha are calling it an AGM battery as the manufacturers don't.

PLH+C Series-Pure Lead Carbon Battery

Advanced pure lead carbon battery, long life and high performance
www.leoch.com www.leoch.com

www.alpha-batteries.co.uk

12v 100AH Leoch Pure AGM Lead Carbon PLH+ C100 Deep Cycle Leisure Battery NCC Class A - Alpha Batteries

12V 100Ah Ultra Deep Cycle battery for multiple applications – from Leoch’s Pure Lead Carbon series. Features • Pure Lead […]
www.alpha-batteries.co.uk www.alpha-batteries.co.uk

Found a test comparing it to Lithium and lead acid
Click to expand...
Lead Carbon (PbC) Batteries are still AGM Batteries :)

I think they are a good choice for RV installations, especially off-grid type users as unlike standard Lead Acid they are ok sitting at a PSOC (Partial State of Charge) for a good length of time, unlike standard Lead Acid batteries which should be recharged to full as soon as possible after use which is often not possible.

They also seem less impacted by temperature variation then 'normal' Lead Acid (You could compare the data for the Northstar Blue+ PbC's in this PDF for 20C and 25C - https://www.northstarbattery.com/media.ashx/nsbbluebatterydischargetables.pdf ).
For the above Blue+ batteries, the temperature co-efficient (adjusting the CV charge voltage as the temperature changes) is less than the Lead Acid default as well, which reinforces that they are less affected.
I've just working through some charging data at the moment as it happens, but I have not seen amazing fast charge rates approaching what can be done with Lithium though, and the "super fast charging to 90% in under an hour" Leoch quote I would be doubtful of (assuming the starting point is 50% SoC). The charging pattern I see is still what a Lead Acid battery demands (which makes sense as PbC batteries are still Lead Acid batteries).
On a recent test my bank took 4.5 hours to go from 50% to 90%, and the last 3.5 Hours (from 67% to 89%) were not limited by the output of the 120A charger (i.e. in Absorption/CV mode and taking less than the charger could provide), which is why I would take the Leoch claim with a pinch of salt - although the PbC's will accept a higher rate of charge than standard Lead Acid, that is definately true :)


Interesting test from Loughborough University, although I don't think the authors fully understand how batteries are actually rated in their discussion point? They run a battery at the C2 rating and then say it doesn't "come close to delivering its nominal capacity" and using the C10 rating as that nominal capacity, rather than comparing against the correct C2 capacity rating. (As an example, the NSB 100FT Blue+ PbC Battery when used at C2 is quoted as having a capacity of 83Ah)
The comment from the authors is akin to saying a cars MPG when driven at 100MPH 'does not come close to the nominal economy' when that nominal economy is one derived when driven at 62MPH)


nabsim said:
Isn’t it carbon Dave it running? If so they are very heavy I believe so check that if right May be an issue
Click to expand...
wfdTamar said:
31kg for a 100Ah, a few kg heavier. Not so bad if you think of it in terms of 'kg per usable Ah'.
Click to expand...
Yup, they are not light by any means. I got my Batteries from Phil when he decided to change to LiFePO4 Lithium Batteries.
My bank of PbC's are 207Kg for 3 x 210Ah(@C10) - so pretty comparable in Kg/Ah at 33Kg/100Ah to the Leoch 100Ah at 31Kg

Overall, the Lead Carbon battery is a good choice albeit at a significantly higher initial cost outlay.
 
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