Solar charging

[Blue Moon]

My van is fitted with solar on the roof and 2 batteries under the drivers seat. When I check the status of the batteries through the solar controller app it shows only one charging (as per pic). I've asked the dealer and they tell me that's how it's wired. Charging both batteries simultaneously. Is that correct or have they skimped on the instal. This sort of stuff is all witchcraft to me.

 

[Phill D]

The low charge could be because the batteries are fully charged however, the second battery is showing no voltage and no charge so are you sure they are connected together.

 

[IRHP]

If the 2 batteries under your seat are leisure batteries that are wired in parallel then they act as one battery. They will always both be at the same voltage.

 

[BouncyBoatFolk]

Is it two battery banks, leisure and starter ? What controller does it have and how's it configured?
Mike.

 

[Blue Moon]

If the 2 batteries under your seat are leisure batteries that are wired in parallel then they act as one battery. They will always both be at the same voltage.

That’s how I’ve been told they are wired and that that the is correct way but I’d like to add an inverter to one of the batteries for the rare occasion I’m off grid and need to top up my ebike battery. By doing this will the inverter take its power from one battery of both? Can the controller be wired so it shows the state of each individual battery. As I said this is a dark art to me and I’m sure you’re all more clued up than me.

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[BouncyBoatFolk]

Might need some photos of the battery bank showing as much detail as possible. Is it a Fiat van?

 

[Tombola]

That’s how I’ve been told they are wired and that that the is correct way but I’d like to add an inverter to one of the batteries for the rare occasion I’m off grid and need to top up my ebike battery. By doing this will the inverter take its power from one battery of both? Can the controller be wired so it shows the state of each individual battery. As I said this is a dark art to me and I’m sure you’re all more clued up than me.

Both batteries need to be connected so in fact operate as one. Charge as one and discharge as one.

If you take a pic showing as much detail.as you can we will advise.

 

[golly]

My van is fitted with solar on the roof and 2 batteries under the drivers seat. When I check the status of the batteries through the solar controller app it shows only one charging (as per pic). I've asked the dealer and they tell me that's how it's wired. Charging both batteries simultaneously. Is that correct or have they skimped on the instal. This sort of stuff is all witchcraft to me.

View attachment 786379

I have a similar charge controller with the app. It has the ability to charge bothe leisure and engine batteries but I have it just charging the leisure batteries and have a battery master to keep engine battery charged. This is my app screen just now

 

[golly]

Battery 1 and battery 2 dont refer to your 2 leisure batteries. Battery 1 is the readings from your leisure batteries, if the controller was so wired the reading shown on battery 2 would be youe engine battery.

 

[Blue Moon]

Thanks for that Golly, does that mean if the engine battery was wired to the controller that my solar would keep that topped up?

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[golly]

It should give a trickle charge to your engine battery (battery 2) .I changed my setup as my leisure batteries are lithium and my engine battery AGM . Whether it would make any difference being different types of battery I dont know but a battery master is so easy to fit [Broken Link Removed] I went for that option.

 

[BouncyBoatFolk]

Thanks for that Golly, does that mean if the engine battery was wired to the controller that my solar would keep that topped up?

That's the principle, though it's only about a 1amp charge, but enough to easily keep a starter battery topped up.
It could be it's never been connected, can you post a photo of the controller wires up, that will show instantly.
Mike.

 

[autorouter]

Thanks for that Golly, does that mean if the engine battery was wired to the controller that my solar would keep that topped up?

Generally the engine battery doesn't need a lot of charging. When you arrive at your destination, or back home, after a drive the engine battery will be fully charged. It only needs a small trickle charge to keep it topped up, and maybe to make up for the small drain from the alarm etc. So a trickle charge output from the solar controller will be quite sufficient.

 

[autorouter]

I’d like to add an inverter to one of the batteries for the rare occasion I’m off grid and need to top up my ebike battery. By doing this will the inverter take its power from one battery of both? Can the controller be wired so it shows the state of each individual battery.

The two leisure batteries wired together will act as if they are one big battery. The two positives will be directly connected with a wire link, and so will the two negatives. Connecting the batteries in this way means that their voltages are always equal, and there is no benefit in measuring the two battery voltages separately, so nobody bothers.

If you connect an inverter to a positive and negative, it will take power equally from both batteries. A small inverter (500W or less) can be easily wired into the batteries, and you plug the ebike charger into the socket on the inverter. You will want to switch the inverter off when it's not being used, because it takes a small drain from the batteries even with nothing plugged in. Most of them have a switch to power it off, and if it's located in an inaccessible position then some can have a remote switch that can be put in a more convenient position. The best position for the inverter is close to the leisure batteries, to keep the battery wires as short as possible.

Wiring a larger inverter is a bit more involved, especially if you want it to power some of the existing sockets of the motorhome without causing problems.

 

[Blue Moon]

Thanks autorouter and others for the explanations. I now understand how its wired. I've a couple more questions:

1, my solar controller has spare contacts for a 2nd battery. I gather now these can be used to connect to my engine battery and give it a trickle from the sun, when available. What size cable should be used and should it have an in-line fuse?

2, my ebike battery is 625w, what size inverter would be ok for this. The 2 batteries fitted are 95ah AGM's.

Thanks all

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[Tigger-Tim]

2, my ebike battery is 625w, what size inverter would be ok for this. The 2 batteries fitted are 95ah AGM's.

We need a bit more information. Look at the back of the charger and see how many amps (or watts) it draws.

 

[Blue Moon]

We need a bit more information. Look at the back of the charger and see how many amps (or watts) it draws.

Im guessing 4amp??

 

[Tigger-Tim]

The critical one is the mains draw, which is 1.5a, so about 350w. So a 500w inverter would be plenty.

 

[Blue Moon]

The critical one is the mains draw, which is 1.5a, so about 350w. So a 500w inverter would be plenty.

Thank you. Any recommendations?

 

[Revolvor]

Thank you. Any recommendations?

This what I am hoping to fit.

Victron have a good reputation for Pure Sine Wave inverters.

Victron 500W Inverter

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[Blue Moon]

Renorgy UK have this.
Too big?
Over spec for my needs?

 

[autorouter]

my ebike battery is 625w,

I think that will be 625 watt-hours (Wh). The charger output is 36V 4A, so its power is 36 x 4 = 144W. So it will take about 625 / 144 = 4.3 hours to fully charge it from flat, or half of that if it's down to 50%.

What size cable should be used and should it have an in-line fuse?

It's only a couple of amps, so a thin cable would be OK. In general it's best to use a minimum size of 1.5mm sq. for any wire in a vibration-prone environment like a motorhome, and that wire is quite OK for up to 15A. It needs an inline fuse near the battery, and a 5A fuse would be about right I think. Wire sizes are usually given as the Cross-Sectional Area (CSA) in millimetres squared, rather than the diameter. Although by coincidence 1.5mm sq wire is about 1.5mm diameter.

Choosing the inverter size is a trade-off. A minimum size will do what you want now, and will have minimum no-load drain and maximum efficiency. However you may want to run other larger items in the future. But an inverter bigger than 500W needs careful thought, whether your batteries can handle the load, and you can recharge them from solar or while driving. An inverter of 1000W to 1500W is a popular addition, to run a hair-dryer, coffee machine or microwave for example.

 

[Tigger-Tim]

Assuming we're talking about the cable from the battery to the inverter to carry 350W, the cables will be taking 350/12 = 29 Amps.

If we size the cables for 500W, that'll be 42 Amps.

Yes, a fuse is a very good idea.

 

[Russell's Dad]

Just to add re the controller. That looks like a PV Logic app you are using. If so then if you wire the second set of terminals on the Solar controller to your starter battery then this will show as battery 2. Battery one will continue to be your 2 leisure batteries. The solar controller will then charge whichever battery needs charging most and then switch to the other battery. It provides the same level of charging to the starter battery and leisure battery.
You might find that you have a DC to DC system fitted in your van to keep the starter battery topped up. If so then this provides a trickle charge to the starter battery from the leisure battery and makes the requirement to attach the starter battery to the solar controller mostly redundant. Your dealer should be able to tell you if this is the case.
I think this may be the instructions for your Solar Controller

PV LOGIC MPPT PRO CONTROLLER USER MANUAL

View and Download PV logic MPPT PRO user manual online. SOLAR CHARGER CONTROLLER. MPPT PRO controller pdf manual download.

www.manualslib.com

 

[autorouter]

Assuming we're talking about the cable from the battery to the inverter to carry 350W, the cables will be taking 350/12 = 29 Amps.

If we size the cables for 500W, that'll be 42 Amps.

Yes, a fuse is a very good idea.

To avoid any confusion, I was talking about the wire from the solar controller trickle-charging the starter battery, answering this question:

1, my solar controller has spare contacts for a 2nd battery. I gather now these can be used to connect to my engine battery and give it a trickle from the sun, when available. What size cable should be used and should it have an in-line fuse?

For the inverter wires, the size depends on the length, which is why I said it's a good idea to locate the inverter very near the batteries. For 2m wire lengths, a 46A current will need 10mm sq wire to keep the voltage drop within 3%. For 1m wire length, you can use 6mm sq. The fuse size could be the next one up from 50A, maybe 60A or 75A.

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[Blue Moon]

Thanks again everyone
I've jumped in, bought a 1000w inverter with remote switch and run decent cables from it to the 2nd battery. This is in a seat box behind the drivers seat so the cable run is short. Nothing connected yet as I'm waiting to borrow a heavy duty cable crimper from a friend. I'm going to add a 100amp inline fuse on the pos + side, is this ok?
Whilst running those cables in I also ran a couple to the starter battery for the 2 spare terminals on my PV Logic solar controller to add a trickle to the starter battery. Would a 20amp fuse be ok for the pos+ on this run. Again nothing connected yet.
Thanks again

 

[Blue Moon]

All cables duly connected.
Went with a 20amp fuse for the solar to starter battery and did the final connection when the sun went in so the panel wasn't generating any power in case of a surge, if it's possible, not sure, am I being over cautious. Both batteries showing as connected on my MPPT App.
Put the ring terminals on the battery cable to the inverter, omg, how hard are those crimping tools to use? Very big, very awkward in a small seat box. Anyway, all sorted, very satisfying to see it finished with exception to the inline fuse. Is 100amp ok for a 1000w inverter?

 

[Tigger-Tim]

Good work. I'd expect 100A to be fine, especially as you'll only be drawing less than 500W

 

[Blue Moon]

That's great thanks. I'll fit the fuse tomorrow, test the 240v output is ok with my ebike chargers before I start cutting holes on the seat box for the remote switch and separate 13amp socket.
This forum is brilliant now some thoughts on my next project
Thanks again

 

[Revolvor]

All cables duly connected.
....... Is 100amp ok for a 1000w inverter?

As long as the cable is rated to more than 100 amps.