Solar panel plus alternator 24v system

tuggersbmx · Senior Member

Solar panel plus alternator 24v system

Jaahn · Guru

Hi smile

You are over thinking this. For some years I have had my solar connected to the start battery and a VSR that switches on the house battery second. Works well and the start battery is always charged either way. As I have a very large size cable running between the two batteries, the connections and the regulator and the VSR are near the house battery.

So the two batteries get charged whenever the engine runs and if it is stopped and the sun is shining the solar charges both. No thinking required.

Jaahn

PS just to be clear, as Terry will say soon ? you must have a solar regulator for your panel. What are the specs on the back of your "24V" panel ?

-- Edited by Jaahn on Wednesday 25th of September 2019 03:20:56 PM

T1 Terry · Guru

Just remember the 24v panel still needs a solar regulator mounted close as possible to the start battery. The other important thing is to keep the solar regulator away from the heat in the engine bay. Most quality regulators have internal temp sensing with a secondary port for a temp sensor probe. The internal sensor will over ride anything the external sensors says when it comes to heat because it has to protect itself, not just the battery. If it gets too hot it will just shut down, even hotter and it will fail completely.

T1 Terry

tuggersbmx · Senior Member

Hi guys, bit of a late response I was out of reception for a few days. My question is though, as I have a 24v system and only want to charge the starter battery from both alternator and solar, solar when parked. If the solar panel is putting out a higher voltage then the alternator won't the vsr just choose the solar even when driving? Do either of you have a drawing or plan you could put up so I can get a better understanding. The ones I've found are all plans of using the vsr to switch from house batteries and start batteries. I just want to use it for start batteries only. Cheers Mick

Jaahn · Guru

Hi Mick smile

Your reply is not late, some people never reply even after a dozen people give good replies !! So good for you biggrin

I did say you are over thinking it. Re-read my post. The charge will go where ever the voltage is lowest so it just does that from either source, and you set it up so the system feeds it where you want it.

What is your vehicle alternator regulator set to when the engine is running. Then what is your solar regulator set to when fully bulk charged. The highest will supply the current. No problems with that. The vehicle battery would normally fully charge quickly after starting so will not take much to top up.

Some newer VSRs will work both ways. I just fitted one, mainly for the switchable function for jump starting using the house battery. But my system is 12V, so you would need to look for a 24V VSR. A VSR is not a complicated device. It just senses the battery voltage of the primary system it is connected to, and then switches the secondary one on too when the voltage comes up and switches it off when it falls. It can be wired in either way and does not care ! I could draw something if you really need me too. hmm

This unit says bipolar switching. !! You could ask them for the instructions.

https://www.ebay.com.au/itm/Enerdrive-12V-140A-24V-140A-Dual-VSR-Relay/282569423992?hash=item41ca733c78:g:BYAAAOSwNT9dI8Wd&frcectupt=true

Jaahn

T1 Terry · Guru

With a solar regulator doing the job rather than a VSR if you only have to one battery, it will charge the battery to what ever the end of bulk charge is set whether the alternator is charging as well or not. In our '74 kombi, the solar often powered everything while the sun was out, so the alternator did very little work, but once the sun went down and the engine was still running, the alternator took over. Our Hino is 24v and wired very similar, just that the lithium start battery piggy backs off the house battery. When the solar is in full swing the alternator does nothing, but if the sun doesn't shine, the alternator takes over while we are driving.

T1 Terry

tuggersbmx · Senior Member

Once again sorry for the late reply. Organising a wedding and building a Nissan civilian from scratch to a motorhome is quite stressful but its all coming together now with power and charging ext. Thanks everyone for the info. From a basic understanding it seems if I buy a 24v vsr and install it so that both the alternator and solar regulator run through it then the vsr will choose the highest volts at any moment to charge the 24v system. So if I'm driving and the suns not out then it will choose the alternator. If its really sunny and the solar is putting out more Volta then it will choose the solar. If I turn off the vehicle and the suns still shinning it will choose the solar. I think I'm pretty sorted now.

T1 Terry · Guru

You still don't have a voltage regulator for the solar do you. You seem fixated on using the VSR yet you don't say that you have a second battery, just the start battery. Is there a problem if the solar charges the start battery even though the engine is running? The solar is still free right? Why not use it or a combination of both charging systems?

T1 Terry

Jaahn · Guru

Hi tugger smile

You still seem to have the incorrect idea of what you need and what will happen with a VSR. Terry asked if you have a regulator for the solar panels. Please answer that. The alternator has a regulator built in to control its voltage and the solar needs a regulator also.

The VSR does not choose the highest voltage source, it actually just allows two batteries to be connected together when suitable voltages are reached and switches them 'off' when the voltage falls. But you do not use the VSR to regulate anything going to the batteries. It is just a switch. hmm

Jaahn

Jaahn · Guru

tuggersbmx wrote:
Hi guys, bit of a late response I was out of reception for a few days. My question is though, as I have a 24v system and only want to charge the starter battery from both alternator and solar, solar when parked. If the solar panel is putting out a higher voltage then the alternator won't the vsr just choose the solar even when driving? Do either of you have a drawing or plan you could put up so I can get a better understanding. The ones I've found are all plans of using the vsr to switch from house batteries and start batteries.
I just want to use it for start batteries only. Cheers Mick

Hi Mick smile

Reading your post again I believe you do not have two battery systems. Just the bus starting batteries. If that is so then a VSR is not what you want. It has no place in a single battery system. It is not a regulator or controller but is just a semi automatic switch to joint two battery systems when the voltage is right.

If you are going to camp for more than a day then I would strongly advise that you have a seperate house battery system to run all the things you need, like lights, fridge, radio, phone charging etc etc. Put these all on the house battery and then have a properly designed charging system for that using your solar and the alternator. And a VSR. hmm

Jaahn

T1 Terry · Guru

In our Mazda 3500 motorhome, the house battery is also the starter battery but it is a 360Ah lithium battery so even down to 0% SOC (all 360Ah used) it still has enough left to start the 3.5ltr diesel engine. Unfortunately most 12v lead acid starter batteries do not have a lot of energy storage, they are designed to give out big amps for a short period and not a slow drain over a long period. They do have an RC rating in mins and this is how many minutes a brand new fully charged battery can deliver 25 amps till the voltage drops below 10.5v.
If you read the battery facts and myths here www.centurybatteries.com.au/getattachment/Technical-Support/Battery-Talk/CY103-2093-Battery-Talk-Newsletter-5_lr.pdf it explains that although the battery is rated with RC of so many minutes and even might have an Ah rating, they are not designed for deep cycle use and will not see a normal cycle life if frequently deeply discharged.

T1 Terry

-- Edited by T1 Terry on Wednesday 9th of October 2019 05:03:02 PM

tuggersbmx · Senior Member

Hi guys, so I'm ready to buy / install my vsr system. Finally finished most of my new fit out bit can't complete it until I have the wiring done. I saw the 24v dual vsr above but could someone please help with a diagrams of how to install. I'm still a little confused on how to wire in both the solar panel and alternator to the vsr. I've seen heaps of diagrams including just the alternator or solar wired to both the start and house batteries but not something explaining how wire up both. Any help would be greatly appreciated. Cheers Mick

Jaahn · Guru

tuggersbmx wrote:
Hi guys, so I'm ready to buy / install my vsr system. Finally finished most of my new fit out bit can't complete it until I have the wiring done. I saw the 24v dual vsr above but could someone please help with a diagrams of how to install. I'm still a little confused on how to wire in both the solar panel and alternator to the vsr. I've seen heaps of diagrams including just the alternator or solar wired to both the start and house batteries but not something explaining how wire up both. Any help would be greatly appreciated. Cheers Mick

Hi Mick smile

I have replied a couple of times and Terry also and I still do not know what you have or what you think you need. We asked some questions but no answers.

I cannot give any more advice on this basis because I would not be sure it would suit your circumstances.

Where to from here ?? perhaps some more communications from you might provide a way foward. Tell us exactly what you have, batteries, house and starter, solar panels information and your solar regulator. What loads you expect, fridge, lights etc.

Cheers Jaahn

tuggersbmx · Senior Member

Hi Jaahn,

Sorry for not providing more specific info.

I will do my best now to supply what i know.

I have a nissan civilian motorhome (1988) which I have refurbished the inside and done most of the new elctrical work.

I have 2 x 200w 24V solar panels 400w in total as they banked together for double the watts. They will be hooked up to a tracer regulator (30amp) and providing charge to the house batteries.

House batteries are 2 x 12v deep cycle agm batteries banked together for a 24v system (140ah and 170 ah) there will be 2 fuse boxes wired of that 24v bank - one 24v fuse box and a 12v fuse box (24 to 12v coverter installed before the fuse box)

I also have a 24V solar panel (100w) installed to charge the 24 volt bank starter batteries with a red arc 24 volt regulator (30amp i believe - came with the bus)

I am running 12v down lights throughout the bus, a 24 volt fridge, a 12v exhaust fan in the shower, a 12 or 24v outlet for TV, 1 x 12v pump for kitchen sink, 1 x24V pump for shower, plus a few additonal outlets for both 12v and 24V for any additonal requirements.

I installed the 24v solar panel to charge the start batteries (2 x century NS70) - solar panel to red arc regulator to the battery bank. Was working fine with the bus just sitting in the driveway but as soon as I start the bus and alternator kicks in the red arc reg goes into error mode ( due to sensing to many amps because of the alternator).

So I was hoping to set up a VSR to be able to provide an automatic chnage over between the alternator / solar panel. As in if im driving then alterantor is used to charge but when im parked the solar panel would be used - or whatever is providing the highest charge. (automatically) without having to use a isolator swith.

I hope this helps.

Mick

T1 Terry · Guru

tuggersbmx wrote:
Hi Jaahn,

Sorry for not providing more specific info.

I will do my best now to supply what i know.

I have a nissan civilian motorhome (1988) which I have refurbished the inside and done most of the new elctrical work.

I have 2 x 200w 24V solar panels 400w in total as they banked together for double the watts. They will be hooked up to a tracer regulator (30amp) and providing charge to the house batteries.

House batteries are 2 x 12v deep cycle agm batteries banked together for a 24v system (140ah and 170 ah) there will be 2 fuse boxes wired of that 24v bank - one 24v fuse box and a 12v fuse box (24 to 12v coverter installed before the fuse box)

I also have a 24V solar panel (100w) installed to charge the 24 volt bank starter batteries with a red arc 24 volt regulator (30amp i believe - came with the bus)

I am running 12v down lights throughout the bus, a 24 volt fridge, a 12v exhaust fan in the shower, a 12 or 24v outlet for TV, 1 x 12v pump for kitchen sink, 1 x24V pump for shower, plus a few additonal outlets for both 12v and 24V for any additonal requirements.

I installed the 24v solar panel to charge the start batteries (2 x century NS70) - solar panel to red arc regulator to the battery bank. Was working fine with the bus just sitting in the driveway but as soon as I start the bus and alternator kicks in the red arc reg goes into error mode ( due to sensing to many amps because of the alternator).

So I was hoping to set up a VSR to be able to provide an automatic chnage over between the alternator / solar panel. As in if im driving then alterantor is used to charge but when im parked the solar panel would be used - or whatever is providing the highest charge. (automatically) without having to use a isolator swith.

I hope this helps.

Mick

That makes life a bit easier to determine just what you need. Rather than a VSR to do the job you want, an SPDT relay will work much better. This relay complete with a plug base and wiring will make the job easy https://www.ebay.com.au/itm/12V-24V-40A-80-AMP-Automotive-Car-Truck-4-5-Pin-Changeover-Relay-Switch/163491311805?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D60048%26meid%3Ddb410100a8aa428d98649a13797f689c%26pid%3D100005%26rk%3D3%26rkt%3D12%26mehot%3Dpf%26sd%3D282962551488%26itm%3D163491311805%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

The battery positive goes to 30 (black heavy wire) solar output from the Redarc goes to 87a (centre heavy wire, blue in some photos and white in others) the alternator output goes to 87 (red wire). The small yellow wire goes to a power supply that only comes on when the ignition is on and the other small wire goes to the battery negative.

The design is with the ignition off the solar feeds through pin 87a to pin 30 and to the start battery. When the ignition is on, the circuit through the two small wires will activate the relay and switch the contacts to 87, from the alternator to 30 going to the battery.

The problem the Redarc is having is it can see a second charging source on the target battery that it can not control so it thinks there is a problem with itself that it can not disconnect the solar.

A better choice would have been a DC to DC charger that also has a solar input. These things are not very efficient at converting all the solar, but they will automatically switch between one supply and the other. Maybe use the solar controller to keep the house battery charged.

T1 Terry

tuggersbmx · Senior Member

Hi Terry,

Thanks for the response and that does seem like a simple solution to my problem.

Regarding the DC to DC charger, are you saying that that would be a better option rather than the SPDT relay as the SPDT wont convert solar effieciently?

So if I connect the wires up to the SPDT the red arc reg will still regulate the power through to the SPDT? and then the same output from the SPDT would go to the battery?

Would your preference to go with the DC to DC charger?

Sorry to asak so many questions but im on a big learning curve when it comes to finer details of all the wiring for power. Ive learnt a lot so far but keen to understand more.

Cheers.

Mick

Jaahn · Guru

tuggersbmx wrote:
Hi Terry,
Thanks for the response and that does seem like a simple solution to my problem.
Regarding the DC to DC charger, are you saying that that would be a better option rather than the SPDT relay as the SPDT wont convert solar effieciently?
So if I connect the wires up to the SPDT the red arc reg will still regulate the power through to the SPDT? and then the same output from the SPDT would go to the battery?
Would your preference to go with the DC to DC charger?
Sorry to asak so many questions but im on a big learning curve when it comes to finer details of all the wiring for power. Ive learnt a lot so far but keen to understand more.
Cheers. Mick

-----------------------------------------------------------------------------------------------------------------------------------------------------------

Hi Mick smile

Thanks for providing the information. Terry has given you a cheap easy solution to your problem. Perhaps you do not see exactly what he suggested to do with the SPDT relay. It is a changeover relay and you can wire it as suggested, so normally the solar regulator will go through it to the start battery. But when you switch the engine on, the relay switches over to the alternator to charge the start battery. The solar is switched off. That is a cheap easy answer. Note you will need to select these options to order that relay; 24V, 80 Amp, 5 pin. Good price !

In my opinion the system is a bit messy and I would not use one panel to charge the starter battery and then have two others to charge the house batteries with two seperate regulators. But it will work OK with Terrys relay.

I believe that Terry is suggesting that the system would be less messy with a DC to DC charger but that is an expensive option and not really simpler.

A VSR is not the correct unit to use for switching the charging to the start battery the relay is correct for that job.

However as set up currently and also with the relay your house batteries will never be charged by the engine alternator. I think that is not using all your options to keep your house batteries charged.

Good luck jaahn

tuggersbmx · Senior Member

Hi Jaahn, Thanks again for your response. Both yourself and terry have helped me quite a bit. What would you do in this scenario to get the best charge to both the start and house batteries. I haven't permanantly wired anything up as yet as I'm still working through all the cabling for all my lights ect back to the fuse boxes. Definitely open to suggestion's. Cheers. Mick

T1 Terry · Guru

Personally, I'd wire all the solar through the one controller and to the house batteries. Link the start battery to the house battery via an VSR or even just a simply diode so the house battery will keep the start battery charged but not excessively drain the start battery if the house battery gets low.
With my system, the solar controller (Plasmatronics Dingo) can control a relay that links the start battery and house battery together as long as the house battery above 13.6v. This way the house battery keeps the start battery charged enough to start the engine yet disconnects if the house battery drops below 13.6v stopping the start battery from being drained.
Another option, there are DC to DC chargers on the market that will allow some reverse charging from the house battery to the start battery so it keeps it topped up, but it mainly uses the alternator to charge the house battery when the engine is running.

T1 Terry

tuggersbmx · Senior Member

Thanks Terry for the response.

hmmmmm. seems like theer are more options a better ways to hook everything all up than I was thinking.

Can you please send a link to the VSR that would be suitable and even a link to the Diode?

I think that this way would be the best solution now as i understand a lot more.

from my understand and as above, it would be best to link all the solar panels I have together as a 24V system and run that to my my tracer regulator (which i have realised is 40Amp) and then link them all to the house batteries with a VSR from the house batteries tot he start batteries.

would there be any issues still with the alternator sending charge to the start batteries whuile driving? would any current then run from the start batteries to the house batteries causing the tracer reg to go into fault?

Cheers again guys.

Mick

T1 Terry · Guru

The MPPT controller is always going to be a problem if it senses a secondary charging device on the target battery. There are some units that will work with more than one charging device on the target battery, but it might be a bit big for where you want to install it www.ebay.com.au/itm/MPPT-60A-solar-charge-controller-regulator-12v-24v-48v-selectable/131439833421
To link the 2 batteries with a VSR you can program try this www.autoelec.com.au/brand/intervolt/ as far as diode, there are lots of split charging diode things about but to just trickle charge the start battery you could use something like this www.solar4rvs.com.au/votronic-standby-charger

T1 Terry

Jaahn · Guru

tuggersbmx wrote:
Thanks Terry for the response.

hmmmmm. seems like theer are more options a better ways to hook everything all up than I was thinking.

Can you please send a link to the VSR that would be suitable and even a link to the Diode?

I think that this way would be the best solution now as i understand a lot more.

from my understand and as above, it would be best to link all the solar panels I have together as a 24V system and run that to my my tracer regulator (which i have realised is 40Amp) and then link them all to the house batteries with a VSR from the house batteries tot he start batteries.

would there be any issues still with the alternator sending charge to the start batteries whuile driving? would any current then run from the start batteries to the house batteries causing the tracer reg to go into fault?

Cheers again guys. Mick

Hi Mick smile

I agree that I would put all the solar onto the house batteries through one regulator. Just check the panel are all about the same voltage.

I have run a Tracer and a Victron MPPT reg with alternator charging also on two MHs and not had any problems, using a relay and using a VSR. I suggest you use a VSR as it is automatic.

I would not use a diode as a very large one is required to avoid burning it out in all circumstances. (however I do have a 200AMP one in the shed !)

Jaahn

-- Edited by Jaahn on Friday 18th of October 2019 09:13:53 AM

-- Edited by Jaahn on Friday 18th of October 2019 01:43:02 PM

T1 Terry · Guru

I'm guessing the only requirement is to stop the start battery going flat when camped up for a while, so something like this au.rs-online.com/web/p/rectifier-diodes-schottky-diodes/0193048/ mounted on a heatsink like this www.jaycar.com.au/heatsink-to-suit-sy4084-sy4086/p/SY4085 would do the job and keep the two battery voltages within about 0.7v of each other stopping a serious current rush yet hold the house battery at a slightly lower voltage than the start battery when the alternator was charging and with a bit of luck the MPPT controller won't freak out or just stop charging because it senses the battery is already fully charged.

The adjustable VSR is dual flow so at a certain voltage the circuit could be opened and I think this works for both the lower and upper voltage at either side, that way the house battery could be isolated from the start battery if the house battery voltage got too low but also once it reached a certain voltage so it didn't freak out the MPPT controller. That way the start battery would be connected to the house battery as long as the house battery was above say 12.4v and below say 13.6v. That would keep the start battery charged enough to start the engine each time yet allow the alternator to return it to what ever the alternator's output voltage was regulated at yet still give some capacity from the start battery to the house battery if needed. It would need at least 4 AWG cable and maybe even 2 AWG cable to reduce voltage drop while allowing a decent current to flow.
You can only get away with this because the house battery is close to the start battery, the voltage drop would be to much in the long cable run involved between a tow vehicle and a caravan.

T1 Terry

Aus-Kiwi · Guru

Fitting a VSR saved me anxiety big time . I always have enough battery to start engine . (Or generator) with decent 7 stage battery charger .