Battery and solar help!

Hi guys, first post here. go easy on me!

I've been doing a lot of research on the web and lurking through archives here for help but everything is becoming fairly overwhelming in regards to choosing the right battery and solar panel for my Campervan build. Sorry in advance if this topic has been covered 1000 times!

I have a really old Engel upright fridge (1980-90's) around 55 liters but I cant find an amperage rating anywhere on it. I plan to run the fridge full time, a few interior LED lights at night and charge a laptop/camera via inverter every so often.

My wife and I will mostly be on the move, driving a few hours most days but if we do decide to pull up and camp for 2-3 days I would like to keep the fridge on.

Would a 100Ah battery in conjuction with a 180w solar panel do the trick? Or will I be looking at something a little more larger?

Most travelling will be done from Brisbane to Darwin during the winter months.

Cheers,

Damien



Back Expand Un-Read 0 Moderator

Reply By: Member - D&G SA - Saturday, Apr 05, 2014 at 08:44

Saturday, Apr 05, 2014 at 08:44
Are you thinking a small generator for those 2-3 days in one spot? It should be mainly sunny at that time of year (hopefully) but what if it is overcast?
AnswerID: 529855

Reply By: Crusier 91 - Saturday, Apr 05, 2014 at 08:51

Saturday, Apr 05, 2014 at 08:51
Just to put it in some perspective, my 120 watt solar panel from Rays Outdoors easily keeps up with my Waeco 60L and touring mates 60L Engel fridge/freezer which are both on 24hr's for up to a week with 3 x LED strips running for up to 6-8hrs at nights. We both run Century 100amph AGM's.
The fridges are in shade through out the day with plenty of circulation in day temps up to the high 30's with good solar days but the odd day being cloudy. Fridges mainly get opened more frequently towards the end of the day when its beer o'clock time.

The 180w panel should be more than enough.
I have a feeling that you would benefit more from a combo of a larger amph hr battery with a smaller sized 120w solar panel like mine.
AnswerID: 529856

Follow Up By: Crusier 91 - Saturday, Apr 05, 2014 at 08:57

Saturday, Apr 05, 2014 at 08:57
Just to follow up, we never let the fridges go empty, every time a beer comes out it is replaced with another, it helps the fridge maintain temps easier.
0
FollowupID: 812630

Follow Up By: Member - Billmoore1 - Saturday, Apr 05, 2014 at 09:20

Saturday, Apr 05, 2014 at 09:20
Love your way of thinking Cruiser

Lifetime Member
My Profile  Send Message

0
FollowupID: 812633

Reply By: Member - John and Val - Saturday, Apr 05, 2014 at 10:30

Saturday, Apr 05, 2014 at 10:30
Hi Damien... and Welcome!

Good questions, and they aren't new here! Suggest one more look on the web, our Electricity for Camping which may help.

The essential unknown in your case is the fridge's demand. In any setup the fridge will be by far the major consumer. To get a handle on your electrical demand you need to know that fridge demand. Suggest it's worth borrowing, or spending $20 on, a cheap multimeter (Ebay or Jayco) capable of measuring up to 10 amps. Once you know the fridge's current (amps) consumption, you'll need to determine roughly what proportion of the time the fridge compressor actually runs, to estimate its daily consumption.

Let's guess - hypothetically the fridge runs about 1/3 of the time, and draws 6 amps while running. That's an average of 2 amps so it's daily requirement is about 2 x 24 = 48 Amphours. Add say 2 Amphours for lighting and maybe 5 for the cameras, torches, laptop and you are looking at a total demand of about 50 - 60 Ah per day. That's all very hypothetical, but probably in the ballpark

That's half the capacity of your 100 Ah battery, and if the battery is to have a decent life span we'd prefer not to discharge it much further than that. When driving, your alternator can input some charge, though unlikely to deliver that total in a day's drive unless you have very heavy cabling, and/or a dc-dc charger (but that's another story). A 180W solar panel with MPPT controller, moved a few times a day to follow the sun will probably handle the daily total.

There are lots of factors to consider - we discuss them in Electricity for Camping .

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 529864

Follow Up By: neimad19 - Sunday, Apr 06, 2014 at 08:03

Sunday, Apr 06, 2014 at 08:03
Very in depth! Thanks. Those links are great.

0
FollowupID: 812720

Follow Up By: Geoff H18 - Sunday, Apr 06, 2014 at 12:25

Sunday, Apr 06, 2014 at 12:25
Hello
I have read your link Electricity for camping which was great.

I have a couple of queries if you could help me please.

1.My Engel states 2.5 A(max), so if it is cycling at 50%
that would be 1.25A per hour therefore 30A over a 24hr period?

2. TV- 4.16A over say 2hr =8.4A per 24 hr?

3. Sat box- 2000mA over 2hr =?

4. Cpap running through 90W ac adapter which @24V ------3.75A say 8 hr =30A??? I have this plugged into a projecta 300 PS watt inverter.

I have 100 W solar panels with a PWM module feeding a 120 Ah AGM battery in a ARK box.I have another 100Ah batt which services the led lights etc in the van.
How much can I expect from these panel on a good day and what panel would I need, to replace and top up the batteries with this approx 80 Ah per day drain?

I thank you for your help and apologize to others for possibly re-hashing old material.
0
FollowupID: 812748

Follow Up By: Member - John and Val - Sunday, Apr 06, 2014 at 17:44

Sunday, Apr 06, 2014 at 17:44
Hi Geoff,

This does fit well under Damien's header, but if it expands as it well may, it may be better to start a new thread.

"1.My Engel states 2.5 A(max), so if it is cycling at 50%
that would be 1.25A per hour therefore 30A over a 24hr period?"

Your maths is indeed correct.

May I correct one thing though - many folk fall for this and it really irks after a while - An amp (A) is a measure of the rate of flow of electrical charge. ( It's actually a flow of one coulomb (6.241 x 10^18 electrons) per second, but let’s not get too hung up on the physics!) So --- we don't refer to amps per hour, any more than we'd refer to kph per hour. (I'm not being critical of you specifically, or aiming to prove I'm a boring pedant! but there are usually over 1000 people logged onto this site, and using incorrect expressions leads to lots of confusion. )

If your fridge is running about half the time, and draws 2.5A when running, then the average consumption is indeed 1.25A. The total demand we express in amphours (Ah), i.e. flow rate x time and so in 24 hours your fridge will call for 1.25 x 24 = 30 Ah.

Your TV - I suspect that it is running from a power adapter labelled 4.16A. If that's the case, then that's probably the maximum that the adapter can supply, rather than what the TV draws from it. I'd expect the TV to in fact draw less than the 4.16A, let's say 3A for 2 hours = 6 Ah.

The sat box. 2000mA = 2A. Again, I suspect the box itself draws less than that, probably about 1A rather than 2A, so in 2 hours that would be 2Ah.

The CPAP - I've recently been around the CPAP loop myself and am still looking for a human compatible system! The adapter is capable of delivering 90W at 24 volts. If it's the machine I think it is (Resmed), there is an alternative 60W adapter which will handle the pump plus humidifier, the 90W adapter being intended to also run a heated tube. If I'm right then you have some options - the pump itself will require a bit less than 30W, the humidifier (which can be turned off) will account for an extra 30W and the heated tube (also can be turned off?) another 30W. Each of those 30W loads corresponds with a current of 2.5A at 12 volts, plus 20% to account for inefficiencies in the inverter and power adapter. That comes to 3A, 6A or 9A. In 8 hours, 24, 48 or 72 Ah. The options to turn off the humidifier and heated tube are important!

Your 24 hour energy budget in rounded figures is
Fridge 30 Ah
TV and satbox 10 Ah
CPAP 25-75 Ah
plus a little (say 5 Ah) for lights, charging torches, phones, etc etc

If your battery is to have a decent life span it shouldn't be run down more than 2/3 of capacity and should be recharged asap. On that 2/3 basis, your 120Ah battery can deliver about 80 Ah. That's enough to handle the fridge and CPAP with humidifier but not heated tube.... and no TV!

How to recharge the battery? Under optimum conditions your 100W panel will provide almost 6 amps with your present PWM controller, or almost 7 amps with a MPPT controller. If we assume 7 hours of good sunshine per day, and keep the panel reasonably aimed at the sun, that's about 40 Ah per day with the PWM, about 10-15% more with an MPPT controller. You need at least 200W of solar capacity to meet your minimum requirements. To have any flexibility you also need to at least double your 120 Ah battery capacity. (It may be possible to make use of the other (100Ah) battery.) You could also provide some charge to the batteries from you vehicle - the balance between solar when stationary and alternator when driving needs further consideration.

As you obviously appreciate Geoff, there's a lot to go into here. Usually the fridge is the main consumer, but adding CPAP adds a whole new dimension. You do need more battery storage and more charging ability. Maybe you might consider the Lithium batteries referred to by Alistair, but $$$$......

Hope that helps

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

1
FollowupID: 812779

Reply By: Member - Alastair D (NSW) - Saturday, Apr 05, 2014 at 10:30

Saturday, Apr 05, 2014 at 10:30
Damien,
I am sure that my reply will trigger criticism but it is intended to give you a rough guide not absolute.

When discharging lead/acid batteries (AGM or whatever) it is best to not discharge them below 60% as their lifetime is greatly shortened the lower you go. So a 100AH battery really only gives you 40AH if you want to be nice to them.

I have an old Engel like yours and it pulls 6A when running. Because the insulation is not as good as the new ones it typically runs approx 40% on. Obviously depends on the weather and the temp setting it is on. I have modified mine by adding some fans to cool the compressor and heat exchanger and it has made a big difference and the fridge is much more efficient.

By comparison the LED lights and laptop/camera charging will consume very little.

If the above is true then your fridge will consume approx 2.5AH for each hour of running. Taking the case when you are camped all day, then you will drain about 60AH from the battery. With the 180w solar panel at ideal full output you will get ~15A, allowing for cloud, shading, not perfect direction, panel losses, regulator inefficiency etc you may get half of this for say 8-10 hrs per day. Thus an input of say 75AH. On a good day you will get more, less when things are against you. Thus an excess of ~15AH over your draw down. All good it seems.

The good side is that when it is hot and your fridge works harder the panels will typically get more sun and more output. Make sure you keep them out of the shade and in the right direction.

If the weather is bad you are probably going to drain the 100AH battery down below the optimal 60% in 1 day. It will probably keep running for about 2 days before the low voltage cutout triggers - the old fridge does not have one so it will just keep dragging the battery down. The problem is if this happens too often the battery life will be really shortened.

So you can think in terms of having to replace your battery every couple of years to keep its capacity up or best to run 2 of them so with say 2 x 120AH units you could handle 3 bad days in a row without damaging your batteries. Keep the solar panel size up to the max you can comfortably manage/fit as this all helps when the sunlight is poor and keeps charging longer morning and evening.

Hope this helps and I am sure many will criticise what I have said but it broadly valid and you cannot be exact with estimates like this.

I have just switched to LiFePO4 batteries which though more expensive can be discharged to 20% without damage and recharge very easily. You do need some care with charging etc but I have ended up with a system that is much lighter, higher capacity and should last ~10 years.

cheers


AnswerID: 529865

Follow Up By: Member - Alastair D (NSW) - Saturday, Apr 05, 2014 at 10:32

Saturday, Apr 05, 2014 at 10:32
My post crossed John's and so some effort was wasted.
0
FollowupID: 812637

Follow Up By: Crusier 91 - Saturday, Apr 05, 2014 at 11:28

Saturday, Apr 05, 2014 at 11:28
Excellent explanation x 100, Alastair D, no info is ever wasted.
0
FollowupID: 812643

Follow Up By: Allan B (Member, SunCoast) - Saturday, Apr 05, 2014 at 18:34

Saturday, Apr 05, 2014 at 18:34
Good one Alastair.
Cannot imagine why anyone would take issue with it.
But tell us about your LiFePO4 batteries..... What capacity are they? What did they cost? What is the charging arrangement? Can you provide a link to their supply source please?


Cheers
Allan

Member
My Profile  My Blog  My Position  Send Message

0
FollowupID: 812686

Follow Up By: Member - Alastair D (NSW) - Sunday, Apr 06, 2014 at 08:18

Sunday, Apr 06, 2014 at 08:18
Alan,
I bought my batteries about a year ago from EVworks in Perth. Their primary business is electric vehicles but seem to have developed into a good source of LiFePO4 batteries and associated gear.

EVworks

I purchased from them as when I first started researching this option the principal of the company Tim Brunner answered my many questions with facts and figures and not hype. Their prices were quite good and seemed to have come down a bit since then. I suspect that they will continue to do so as the demand and usage of Li batteries increases.

The early Li batteries had significant problems but now the new variants seem stable, reliable and more a practical option.

I bought 8 160AH 3.2v cells and configured them as a 320AH 12v battery, ie 4 parallel pairs of cells in series. This actually typically gives a battery of 13.2v under load. If you look at the following link you can see that the discharge curve for these batteries is remarkably flat and they drop off very quickly when near the limit.

Graphs

I have spent quite a lot of time reading and playing with the batteries and have now got a good feel for them. I have built a microprocessor based data logger and cell monitor which will become a permanent part of the install. Not necessary but just part of the fun of playing with technology.

In practical terms the batteries hold their charge very well, love to provide high current, which is why the electric vehicle people use them, and charge quickly if you do it right. The big difference to lead acid is that the charge/discharge curve being flat means they provide an ideal energy source and they accept almost full current right up to about 95% SOC at which point the voltage rises fast. You must terminate the charge ideally around 3.8v per cell and certainly before 4.2v otherwise they will be damaged. This is quite easily done and most existing chargers can be used with a little care.

Smart chargers with auto reconditioning, desulphating cycles etc must not be used unless you can turn it off.

I will not go on but am happy to provide more info if you send me a member message.

In summary my cells and bit to go with them cost about $1800. This gives me 320AH nominal but a real 260AH if I go to ~20% SOC which can be done with no penalty on life. Their total weight is 60Kg.

My AGM alternative was to use 2 x Lifeline 255AH batteries to give about the same usable capacity going to 50% SOC. The weight was about 140Kg and cost about $2300. I know I could go for cheaper AGMs but I want reliability and a decent lifetime. I consider I am way ahead as I can expect a 10 year life from the Li batteries if I treat them well.

One aspect of the Li batteries that is good but presents a hazard is that their ability to provide high current means you must ensure good insulation against shorts. Whilst a lead acid will provide a big flash these batteries are in a different league. They just love to discharge !!

Happy to answer any questions via member msg.

cheers
1
FollowupID: 812725

Follow Up By: Allan B (Member, SunCoast) - Sunday, Apr 06, 2014 at 08:52

Sunday, Apr 06, 2014 at 08:52
Many thanks for that Alastair. You gave me just what I was wanting.
My current pair of 110Ah AGM's are still holding up but I will start researching Li's ready for when they inevitably fail.
As an electrical engineer I understand about the need for fault-current limitation and take your advice onboard.
And thanks for your member msg invitation. I may have questions as I research and plan.

With regards
Cheers
Allan

Member
My Profile  My Blog  My Position  Send Message

0
FollowupID: 812729

Reply By: Member - Frank P (NSW) - Saturday, Apr 05, 2014 at 10:37

Saturday, Apr 05, 2014 at 10:37
Damien,

Here's my stab at your power budget:

Engel Land says your fridge will pull between 0.5 and 3.3 amps when running. Let's assume the worst to account for hot days - that is it pulls 3.3 amps whenever it's running, and assume a 50% duty cycle. That's about 40 amp-hours a day. And that will depend on how often it is opened and re-stocked. It's probably on the low side.

Lights - say 1.5 amps for 5 hours a day, = 7.5 amp hours

Charge a laptop off an inverter - a bit hard, this one. If the laptop's power brick is 90 watt (common) and the laptop battery is flat it may start out pulling about 7.5 amps, tapering off as the battery charges. So lets say an average of 5 amps for 3 hours to charge the battery, = 15 amp hours. (I'm not sure about this, there are so many variables - battery chemistry, charger design, etc - so if anyone has better info please feel free to follow up). Running it off the inverter there will be inefficiencies, say 15%, so round the amp-hours up to about 17.5.

Charging the camera battery via the inverter - another amp for 3 hours.

Total for laptop and camera on the days you do it = 20.5 amp hours.

So your total on the days you charge your toys would be 40 + 7.5 + 20.5 = 68 amp hours.

On other days it would be 47.5, call it 50 amp hours.

If you accept the 50% discharge rule as being the optimum compromise between practical battery useage and longevity, then on most days a 100 amp-hour battery would be fine. I think it would be acceptable on the odd laptop charging days to take the extra 20.5 amp hours out as well.

Solar Charging:
Batteries are not 100% efficient. You need to put more amp-hours in than you take out to fully charge them, about 20% more. So on the days you pull 68 amp hours out you will need to generate about 82 amp-hours, and on the other days about 60 amp-hours.

Solar panels are not 100% efficient either, and to get the best from them an MPPT solar regulator is recommended.
Collyn Rivers article here on this site says to expect only about 70% of the nominal output of the panels. And also, lets work on his example of about 5 peak sun-hours a day. (That doesn't mean just 5 hours of sunshine. A peak sun-hour (PSH) is a standard measure of solar light intensity. The intensity is not uniform throughout the day, even on a clear day with full sunshine, and the 5 PSH takes account of that. It's covered in the Rivers article.)

Using those figures, your 180 watt panels will generate on average 70% of that, about 125 watts, about 10.5 amps at 12V. With 5 peak sun hours you'll get about 52 amp-hours a day. Not enough to fully re-charge even a non-laptop day with solar alone, you'd have to rely on topping off with the vehicle or generator. That may be adequate if you plan on driving most days with just the occasional 2 or 3 day stop.

With a bit more maths you can figure that to be generator-free on your non-laptop days 240 watts of solar will keep you reasonably self sufficient, depending on how you use your fridge and how much actual sun you get. On your laptop-charging days you'll be a bit behind. You may make it up over the next day or so if there's plenty of sun, or run the genny or tug.

That's my take on it - hope it helps

Cheers


FrankP

Lifetime Member
My Profile  My Blog  My Position  Send Message
Moderator

AnswerID: 529866

Follow Up By: Member - Frank P (NSW) - Saturday, Apr 05, 2014 at 10:40

Saturday, Apr 05, 2014 at 10:40
And my post crossed John's and Alistair's, so again, some effort wasted.
FrankP

Lifetime Member
My Profile  My Blog  My Position  Send Message
Moderator

0
FollowupID: 812639

Follow Up By: Member - Alastair D (NSW) - Saturday, Apr 05, 2014 at 11:08

Saturday, Apr 05, 2014 at 11:08
However in our various ways we have come up with similar numbers and suggestions thus proving it is not an exact science but broad estimates are useful. Unplanned teamwork !!!!!!!!!
0
FollowupID: 812641

Reply By: Member - John and Val - Saturday, Apr 05, 2014 at 11:56

Saturday, Apr 05, 2014 at 11:56
Alistair and Frank

Clearly just another instance of great minds thinking alike!!

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 529871

Follow Up By: Member - Frank P (NSW) - Saturday, Apr 05, 2014 at 17:28

Saturday, Apr 05, 2014 at 17:28
Thank you John and Alastair :-)

I'm not sure Alastair will be happy having his mind cast in the same light as mine, but hey, if we have been of any help, then we have served a purpose.

I'm a little concerned that some posters have come up with a seemingly definite figure of 6 amps or so for the fridge when it's running, whereas the apparently authorative website I looked at said 3.3.

6 amps makes a considerable difference to my estimation, and reinforces Bantam's opinion that 200amp-hours of batteries are needed.

Damien really needs to measure the current drawn by his fridge and either get back to us or substitute his figures in our calculations. I'd be interested to know what the real figure is.

Cheers
FrankP

Lifetime Member
My Profile  My Blog  My Position  Send Message
Moderator

0
FollowupID: 812680

Follow Up By: Member - Alastair D (NSW) - Sunday, Apr 06, 2014 at 08:28

Sunday, Apr 06, 2014 at 08:28
Frank,
The 6A comes from measurement not data sheets. It was this figure when running when I bought the fridge in 1972 and is the same now. Many of the manufacturers quote average currents, so if the fridge typically runs 50% of the time they will cite 3A average.

My new Bushman fridge is similar and I measured the current when I bought it.

cheers
0
FollowupID: 812728

Reply By: The Bantam - Saturday, Apr 05, 2014 at 12:10

Saturday, Apr 05, 2014 at 12:10
The maths have been worked many times before.
To keep up with pretty well any fridge run as a fridge with any sort of reliability, 200Ah of battery and arround the 200Ah of solar pannel is about the lower limit.

The 180watt pannel is probaly close enough, but you need to at least double the battery storage capacity to 200Ah ish.

OH and make sure the cabling is adequate and you have a good regulator.

cheers
AnswerID: 529874

Follow Up By: The Bantam - Saturday, Apr 05, 2014 at 12:12

Saturday, Apr 05, 2014 at 12:12
That second line should read 200watts of solar.
0
FollowupID: 812646

Reply By: neimad19 - Saturday, Apr 05, 2014 at 22:50

Saturday, Apr 05, 2014 at 22:50
Wow thank you all so much for the in depth replies! I can already see that joining this forum has been a valuable decision.

I do have a decent multi meter but I'm not sure how to go about checking the Amps of the fridge, any ideas?. I had another look today but couldn't see any Ah rating. There was an old worn sticker on it and I'm guessing that used to be the fridge power details.

So after reading the replies, it looks like buying a 150-200Ah battery will put me in the safe zone for running the fridge 'off grid' for a few days.

I've found a Mppt solar charger on ebay that looks decent so this will be used to charge the batteries, which brings me to another question - Can I still charge from the car alternator AND the solar panel at the same time? Would I hook up the feed from the alternator to the the solar input on the Mppt or straight to the battery?

AnswerID: 529907

Follow Up By: Crusier 91 - Sunday, Apr 06, 2014 at 07:14

Sunday, Apr 06, 2014 at 07:14
You should install a "redarc isolator" to stop fridge battery drawing power from your start battery.
The solar should be hooked up directly to the fridge battery. I still disconnect solar at night because the MPPT controller still draws power from the battery, its not much but when we are in one spot for a few days every bit counts.
1
FollowupID: 812714

Follow Up By: Crusier 91 - Sunday, Apr 06, 2014 at 07:23

Sunday, Apr 06, 2014 at 07:23
Rays outdoor 120w Powertech solar panels come with a built in charge controller, plenty of leads, Anderson plugs and padded bag@ $600.
I was lucky enough to purchase a brand new one from a retired bush tour operator for $300. I has never let me down in 3 years.
1
FollowupID: 812716

Follow Up By: Member - 178 - Sunday, Apr 06, 2014 at 07:39

Sunday, Apr 06, 2014 at 07:39
I have installed a Ctek 250s Dual for that purpose right beside 2nd Bettery which is far away from start battery and it can charge from both sources separately or indivually,has a MPPT controller built in and isolates the main battery. bit Xy but redarc have a similar unit but even more expensive.
1
FollowupID: 812717

Follow Up By: Crusier 91 - Sunday, Apr 06, 2014 at 07:40

Sunday, Apr 06, 2014 at 07:40
Not sure if this is relative info for you,
The way you use the fridge is important in preserving battery power.
A empty fridge or near empty fridge will use more power than a full fridge.
Try not to load your fridge with many food items that are at room temps at one time, for example beer.

1
FollowupID: 812718

Follow Up By: Crusier 91 - Sunday, Apr 06, 2014 at 08:16

Sunday, Apr 06, 2014 at 08:16
Here's what looks to be a good battery set up using the Ctek as 178 has mentioned
http://youtu.be/Hy0j6hifJJM
0
FollowupID: 812723

Follow Up By: Crusier 91 - Sunday, Apr 06, 2014 at 08:21

Sunday, Apr 06, 2014 at 08:21
The ultimate set up
http://youtu.be/igSw_wqNWMc
0
FollowupID: 812726

Follow Up By: Member - John and Val - Sunday, Apr 06, 2014 at 09:38

Sunday, Apr 06, 2014 at 09:38
Damien,

re "Can I still charge from the car alternator AND the solar panel at the same time? Would I hook up the feed from the alternator to the the solar input on the Mppt or straight to the battery?"

Yes you can charge from both simultaneously, but.....

As Cruiser mentioned you need switching in the engine bay to disconnect the feed to the trailer when the engine isn't running, otherwise your cranking battery will be delivering power to run the household. Cruiser's Redarc isolator is one such and a good one. The supply from the alternator should be fed directly to the battery, not connected to the input of the solar controller. (By directly I really mean via a fuse. A fuse should ALWAYS be fitted right at any battery to provide protection.)

The Ctek charger mentioned is a combination dc-dc charger and mppt solar controller in the one box. My understanding is that it does not provide both functions simultaneously, so, while everything can be left connected, you won't get the benefit of both sources.

My preference, to get the benefit of both sources simultaneously, would be to use a dedicated MPPT controller for the solar, and initially a direct feed to the battery from a controller in the engine bay. If this proves inadequate, I'd increase the size of the cabling from up front and probably add a dc-dc charger close to the trailer battery. The extra battery recommended by Bantam would also be a very high priority. The discussion above regarding Lithium batteries is very relevant too ---- All of this stuff provides excellent opportunities for spending money!

Cheers

John
J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein

Lifetime Member
My Profile  My Blog  Send Message

0
FollowupID: 812731

Sponsored Links

Popular Products (13)