AGM not reaching full charge.

Submitted: Sunday, Apr 17, 2022 at 14:01
ThreadID: 143564 Views:7610 Replies:12 FollowUps:37
This Thread has been Archived
Have 3 120Ah AGMs in parallel in a caravan. All OEM installation. Batteries are about a year old and have been run down to 10V a couple of times. Now it doesn’t seem to matter how long I charge for via solar or car Anderson plug the charge is battling to get up to 12.1 or 2 and doesn’t seem to have any guts. I haven’t been in a caravan park on along time and mostly relying on solar panels on roof of van. I am wondering if the batteries need to go thru a full charging cycle with the 7 stage smart charger with on shore power to get them cleaned up and back up to capacity. Cheers Kirk
Back Expand Un-Read 0 Moderator

Reply By: Peter_n_Margaret - Sunday, Apr 17, 2022 at 14:23

Sunday, Apr 17, 2022 at 14:23
It is important that AGMs are fully charged on a regular basis.
Failure to do that may have wrecked them.
The solar should be able to do as good a job at that than any 240V charger, if you have sufficient and its voltages are appropriately set.
I don't own a 240V charger.
OKA196 motorhome
AnswerID: 640220

Reply By: Frank P (NSW) - Sunday, Apr 17, 2022 at 14:28

Sunday, Apr 17, 2022 at 14:28
You might get them back if you do as you've suggested. But if they've been undercharged for a long period they might never regain full capacity.

How much solar do you have?

And re the Anderson, more info needed to be able to assess what's been happening. Eg, does the tug have one of those so-called "smart" charging systems?

What voltage under load is at the Anderson?

What sized cables to the Anderson in the car and from the Anderson to the van battery?

Are you using a dc-dc charger?

EDIT: Peter posted while I was writing. That would be the worst outcome and, sadly, quite likely from what you've told us.

Lifetime Member
My Profile  My Blog  My Position  Send Message

AnswerID: 640221

Follow Up By: Kirk L - Sunday, Apr 17, 2022 at 14:57

Sunday, Apr 17, 2022 at 14:57
Thanks frank. Yeah the Anderson is all good and has been fine. Nothing has changed. I’m thinking as Peter said maybe I haven’t been nice to the batteries by giving them a full charge regularly enough. I have had a period of time where I had shade for a major part of the day and batteries have gradually gotten down. I’ll try either running the tenser for the full 6 hours or whatever it is for the charger to do it’s full thing or book onto a caravan park and do same. I have read that to rejuvenate them I could run completely flat and then charge from there or put another fully charged battery in parallel and charge thru that one. Just Utube stuff. There is also a record button on the charger I might try but manual says that’s 4 hours. So yeah just maybe needs more time.
FollowupID: 919309

Follow Up By: Frank P (NSW) - Sunday, Apr 17, 2022 at 15:27

Sunday, Apr 17, 2022 at 15:27
You mentioned a "tenser" as a charger. Did you mean "Battery Tender"? If so, how many amps does it deliver? For your 360Ah system a 40 amp multi-stage charger would be ideal, though 20 amps would do.
Some of those Battery Tenders only deliver a couple of amps which would be useless in your situation.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919310

Follow Up By: Kirk L - Sunday, Apr 17, 2022 at 15:54

Sunday, Apr 17, 2022 at 15:54
Typo. It was supposed to be genset. Run that or plug into shore power and let charger do a full cycle and see if it can bring them up. There is a recon button on charger too, but I think it does that automatically if needed. I have 300W of solar but as I said I think it’s more the batteries not taking charge because I haven’t given them a good charge for a while and I guess they have “ memory”.
FollowupID: 919311

Follow Up By: Frank P (NSW) - Sunday, Apr 17, 2022 at 16:06

Sunday, Apr 17, 2022 at 16:06
No, they don't have "memory" but they will degrade if not regularly charged to 100%. The symptoms are even though the batteries are fully charged (ie the charger has gone into float), when you put a load on them they just don't last like they used to.

I wouldn't run them down to zero as you metioned earlier, nor would I add a 4th, good, battery. Just get the charger on to them and run it until it has finished.

Also, I think 300 watts of solar is a bit skinny for your 360Ah battery pack.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919313

Follow Up By: Kirk L - Sunday, Apr 17, 2022 at 16:16

Sunday, Apr 17, 2022 at 16:16
Thanks frank. As usual great advice. I’ll get some more guzzlene and run genset and give a good charge.
FollowupID: 919314

Follow Up By: Frank P (NSW) - Sunday, Apr 17, 2022 at 17:09

Sunday, Apr 17, 2022 at 17:09
"Recon" /"Rejuvenation" ...

If that means a "desulphate cycle" where a high frequency voltage is applied to the battery for some hours (mine goes for 24 hours if selected) than that should be ok. It is designed to deal with young, soft deposits of sulphation. Sulphation hardens over time if left unattended and once that happens there is no removing it.

If it means " equalisation" where a low current is applied to the batteries until they come up to a high voltage (around 16, +/-) then that will only add to the problem. Make sure the button on your charger does not start an equalisation cycle.

I trust you have your charger set to AGM or that it can auto detect the battery type. Dunno how that's done, have to trust the manufacturer I guess.

Good luck.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919315

Reply By: Member - peter g28 - Sunday, Apr 17, 2022 at 16:47

Sunday, Apr 17, 2022 at 16:47
I agree with the previous posts AGM's hate to be under charged or sit for long periods in this type of SOC for they can sulphate. Hopefully by getting onto a decent 7 stage charge with a desulphating may get some capacity back..but for how long until this trouble comes back one knows.
It may be a case that you have lost 20% capacity of your battery battery bank and with a bit of due diligence you could work around this.
Adjunct to this you could start researching and budget for a transition over to a lithium system for your future power needs in your caravan.
AnswerID: 640222

Follow Up By: Kirk L - Sunday, Apr 17, 2022 at 17:10

Sunday, Apr 17, 2022 at 17:10
Exactly right. I already approached itec about lithium’s. They recon I need 3 120s as I have now at $999 each. Sale price $899. I thought a little less in lithium’s would do the job as they are quick to charge. I also read that current chargers are ok then that the AGM chargers will ultimately reduce life of them. It’s a huge science with a wealth of differing opinions. I thought I had a fair idea in my initial post but you guys have backed that theory up.
FollowupID: 919316

Reply By: Greg W22 - Sunday, Apr 17, 2022 at 17:33

Sunday, Apr 17, 2022 at 17:33
Are the charging circuits connected to the batteries properly.
Positive to the first battery and earth
to the last.
AnswerID: 640223

Follow Up By: qldcamper - Monday, Apr 18, 2022 at 04:20

Monday, Apr 18, 2022 at 04:20
That has little to no affect on charging, the tiny amounts of resistance in the cables is for all intensive purposes non existant at low currents. Maybe a different story with high discharge currents of hundreds of amps but other than that a facebook myth perpetuated by armchair experts.
Before you come back with all the googled facts and figures that you probably dont understand do the maths, actually look up the cable manufacturers specs and apply ohms law to it and see for yourself how much difference it would make on low load applications having an extra couple of feet of decent size cable in one battery circuit.
FollowupID: 919323

Follow Up By: Greg W22 - Monday, Apr 18, 2022 at 06:30

Monday, Apr 18, 2022 at 06:30
Apparently it does have a big affect on charging currents. As the full charge in not flowing through the 3 batteries. If the charger is connected in parallel then only the 1st battery is taken the full current. Its got nothing to do with ohms law (resistance). The charging current has to flow through all the cells.Ive seen many ruined batteries that have been wired incorrectly. So I'm making no assumptions here. Apparently I've been an electrician for over 42 years and worked in the rv industry 12 years. So I'm sure I know what I'm talking
FollowupID: 919324

Follow Up By: Kirk L - Monday, Apr 18, 2022 at 11:16

Monday, Apr 18, 2022 at 11:16
Really hard to tell without delving deeper. There are a lot of other black wires running off the earth side of the batteries but there are no extra wires running from pos of first battery or beg last battery but it may be connected in somewhere else.
FollowupID: 919327

Follow Up By: Greg W22 - Monday, Apr 18, 2022 at 14:09

Monday, Apr 18, 2022 at 14:09
It seems like your batteries have never been charging properly. All charging circuits battery chargers,solar,andos need to flow through all the batteries. So you get full charging current to all the cells. It seems only one battery has been charging and eventually it's been completely drained. The plates could be damaged in all the batteries now. Does your van not have a shunt ? Having wires come off all the batteries is a rough job. This wouldn't affect the load as it would draw current evenly off each battery. But when it comes to charging circuits you can't just connect them anywhere. What i would do is disconnect all 3 batteries and with a decent battery charger 20 amp plus. Is charge each battery individually . This way you could find out if you batteries are still ok.As has been mentioned you would be better with more solar power. What size fridge you have and any inverters you have .? This will give you a good idea of ow much solar you will need to to replenish your batteries. Or you could keep your solar but wire in a battery charger.
FollowupID: 919328

Follow Up By: Kirk L - Monday, Apr 18, 2022 at 14:27

Monday, Apr 18, 2022 at 14:27
Thanks Greg. The system has been working fine up until recently. It’s an MDC caravan and I would assume it all should be wired correctly. Have 1000w inverter but that is off. I can normally drive and get to camp with full charge of 13.7 V. I think just lately I have been in a lot of shade and haven’t fully charged batteries for too long. I’m running a recon cycle on the charger now and they seem to be improving. I’ll report back in a few days when I get some more fuel for genset and give them a full charge.
FollowupID: 919329

Follow Up By: qldcamper - Monday, Apr 18, 2022 at 18:30

Monday, Apr 18, 2022 at 18:30
Be wary of who you take advice from, get an opinion from a professional who is actually looking at your set up and not someone who is guessing and doesnt really understand the basics.
Id be careful paying much attention to someone that says current flow has nothing to do with OHMS law or resistance.
FollowupID: 919333

Follow Up By: Croc099 - Wednesday, Apr 20, 2022 at 23:36

Wednesday, Apr 20, 2022 at 23:36
Sorry Greg but you've forgotten what you may have learned 42 years ago. The first battery certainly does not take the full current. In parallel, the charging current will be distributed to all three batteries inversely proportional to their internal resistance and that of the connecting cables in accordance with Kirchoff's Law.
FollowupID: 919352

Reply By: 2517. - Sunday, Apr 17, 2022 at 19:28

Sunday, Apr 17, 2022 at 19:28
Realistic you need 600 watts of solar,there is a good article on the forum about solar.
AnswerID: 640227

Reply By: Member - Cuppa - Sunday, Apr 17, 2022 at 20:34

Sunday, Apr 17, 2022 at 20:34
Your mention of 12.v or 12.2v rings warning bells for me. If your batteries were being properly charged they should see 14.4v or 14.5v every 24 hours when in fulltime use. This requires sufficient charging resources. Having reached that voltage they will drop to a float voltage of between 13.3v to 13.8v. If they have only ever got up to 13.something they have never been properly charged & this is likely the cause they are failing prematurely. 12 months is a very short life. I recently replaced my 3 x120Ah batteries. They were almost 10 years old. I only have 425w of roof mounted solar, but also have a 40amp Dc to Dc charger. Throughout their life the lowest voltage they ever saw was 12.3v & that was only on one occasion. 12.5v early in the morning before first light was the 'norm'.
See 'My Profile' (below) for link to our Aussie travel blog, now in it's 5th year.

My Profile  My Blog  My Position  Send Message

AnswerID: 640230

Reply By: qldcamper - Monday, Apr 18, 2022 at 04:27

Monday, Apr 18, 2022 at 04:27
You may have a faulty battery, it does happen thats why there is a warranty period.
Charge them, then seperate them and let sit disconnected over night then check the voltages in the morning, they should all be pretty close to the same.
With multi battery set ups it is handy to have a DC clamp meter so you can actually see where the current is going to and coming from, pick them up cheap on ebay these days.
AnswerID: 640233

Reply By: Member - McLaren3030 - Monday, Apr 18, 2022 at 09:20

Monday, Apr 18, 2022 at 09:20
Hi Kirk,

As someone else has mentioned, no where near enough solar capacity for the battery capacity. A good rule of thumb is that for every battery amp you have, you need double the watts of solar capacity. This applies equally for both AGM & LiFePo4 Batteries, but is more important with AGM’s due to there slower charging rate.

Also, you stated that you have run them down to 10 volts on more than one occasion, this will certainly shorten their lifetime. At 10 volts, they are basically at 0% SOC, or dead flat. AGM’s really do not like to be taken down below 50% SOC, the more often they are taken below this, the shorter their lifespan. They are much “happier” at around 75% SOC. 75% SOC is around 12.3 volts, 50% SOC is around 12.0 volts.

Whilst I am certainly not an Auto. Elec. or even a 12 volt expert, personally I think you may have permanently damaged your batteries, and I doubt you will be able to “recover” them.

Certainly if you prefer and do a lot of “off grid” camping, LiFePo4 batteries with an appropriate charger and appropriate solar capacity is the way to go. As far as “drop in” LiFePo4 batteries are concerned, personally, I am not convinced that without an appropriate LiFePo4 charging profile, your LiFePo4 batteries will last as long. When spending around $2,500 on LiFePo4 batteries, another $300 or so to look after them seems like a good investment to me.

As far as LiFePo4 battery brands are concerned, Renogy seem to get very good reviews, are generally cheaper than ITechworld at around $800, I have seen them on special at $699 for a 100 amp battery.


Lifetime Member
My Profile  My Position  Send Message

AnswerID: 640237

Follow Up By: Kirk L - Monday, Apr 18, 2022 at 09:33

Monday, Apr 18, 2022 at 09:33
Thanks for that. Good information. The longer I have this van the more or a piece of rubbish I think it is. It starts with M and already have a consumer complaint about them. I bought the van with last of my money thinking it would do me many years not. Looks like I’ll need to start saving. Cheers.
FollowupID: 919325

Reply By: qldcamper - Tuesday, Apr 19, 2022 at 04:34

Tuesday, Apr 19, 2022 at 04:34
If the batteries are about a year old they should come back to at least a useable state even if they have a reduced capacity, if they are unrecoverable which I doubt try doing a warranty claim, if nothing else the company you approach will test them properly.
AnswerID: 640246

Reply By: Member - LeighW - Tuesday, Apr 19, 2022 at 10:56

Tuesday, Apr 19, 2022 at 10:56
If your charger can't get them above 12.1V you need to look at why, possible causes:

Charger not working properly
Your taking out more than the charger can put back in
A faulty battery or batteries.

First thing I would do is stop using the system as trying to diagnose what's going on with a limited charging ability whilst still using the system which is just going to complicate things. You then need to separate the batteries and charge them individually to check they will accept and hold a charge.

Once you have that sorted out then you need to look at your charging setup as you would appear to have insufficient charging capability to meet your needs if your letting the batteries get down to 10V

Having various black leads connected to the negative sides of the batteries probably means the installer didn't install a busbar for the negatives. As long as the loads aren't high you can probably get away with leaving it as it is.

Lifetime Member
My Profile  Send Message

AnswerID: 640251

Follow Up By: Kirk L - Thursday, Apr 21, 2022 at 17:58

Thursday, Apr 21, 2022 at 17:58
I believe the system is fine. It’s been ok for a year. I just had a long period of cloudy days and parking under trees etc and was too lazy to hook up genset and give them a good charge. I have leant on heat that AGMs need to be kept topped right up regularly which I neglected to do for a week or two. I ran genset the other day for as long as my fuel lasted and they came up to 13v however driving all day again today they are only up to 12.2 again. As soon as I get to camp tomorrow I will do a full charge on them and see if they come up to speed. If not mdc are doing a warranty claim. It’s all original MDC factory installation so should by rights be fine but not necessarily.
FollowupID: 919354

Follow Up By: Frank P (NSW) - Thursday, Apr 21, 2022 at 21:01

Thursday, Apr 21, 2022 at 21:01

A successful warranty claim may get you a new set of batteries, but unless the under charging is fixed you new batteries will face the same fate as the old.

If you're driving all day and the van batteries only get to 12.2V then I venture to suggest there is something wrong with your tug to van charging system. You said earlier you think "the Anderson" is ok, but I'm sorry, I think it is not.

I don't think you've said exactly what charging equipment you have.

Do you have a dc-dc charger? If so, what brand? What model? What amps?

When you run the genny it will be powering a mains charger. What brand mains charger? What model? How many amps?

Same questions for your solar charger - brand, model, amps?

With that info we can get a better picture of your setup and can perhaps offer more advice (should you want it).


Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919356

Follow Up By: Kirk L - Friday, Apr 22, 2022 at 08:30

Friday, Apr 22, 2022 at 08:30
Frank I’m seeing a sparky this morning. As I said the system was ok before o let the batteries get a little low. Yesterday after driving I had the 12.1 but after a bit of sun maybe up to 13 somehow. I think the problem is in the batteries just not accepting charge. Anyway maybe one is faulty. I’ll know soon. Cheers.
FollowupID: 919361

Follow Up By: Member - McLaren3030 - Friday, Apr 22, 2022 at 08:43

Friday, Apr 22, 2022 at 08:43
Hi Kirk,

Good luck with the warranty claim. I do not think it will be honoured if you have let the batteries get down to 10 volts. That would be considered unto be caused by in appropriate use, and not covered under a warranty claim.

You have admitted yourself, that you parked in the shade under trees, did not fully charge when you had the chance, all this is your fault, and not faulty workmanship with regard to battery construction. No offence intended.

Certainly having your charging systems (vehicle/solar/240volt) checked by a competent Auto. Elec. is the way to go, he should be able to advise you of an appropriate path forward.


Lifetime Member
My Profile  My Position  Send Message

FollowupID: 919362

Follow Up By: Kirk L - Friday, Apr 22, 2022 at 14:40

Friday, Apr 22, 2022 at 14:40
Got batteries check by auto spark this morning. They are OK but appears that as many of you have said the charging system is inadequate. Fine for optimal conditions but when the going get tuff they can’t keep up unless run for much longer of coarse. He said that at 12 v they are pretty much flat which surprised me. Batteries are a science and I have learnt a bit here thanks to you guys. I will make sure they are kept above the 12v from now on. Good ole M.. ! Thought I paid good money to get top of range but all cheap Chinese garbage. Just about every bit of gear has failed so far.
FollowupID: 919370

Follow Up By: Frank P (NSW) - Friday, Apr 22, 2022 at 17:22

Friday, Apr 22, 2022 at 17:22
Keeping them above 12V is not enough!! 12V is about 50% charged. If they never get above that they will continue to deteriorate.

You need to charge to 14.2 to 14.4 as often as possible.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919375

Follow Up By: Zippo - Friday, Apr 22, 2022 at 18:09

Friday, Apr 22, 2022 at 18:09
Kirk, Frank asked a number of very relevant questions above. Answers to those may reveal the underlying issue and the way forward.

Some simple ones:

- do you have a DC-DC charger or simply a direct tug battery connection?
- does the tug have a so-called "smart alternator"?
FollowupID: 919378

Follow Up By: Kirk L - Friday, Apr 22, 2022 at 18:59

Friday, Apr 22, 2022 at 18:59
I have answered those questions by saying my system is inadequate. That’s all I needed to know. I cannot afford to rebuild the caravan. And besides I have no idea what a tug is and you are the first i heard of it. I’ve had enough and will have to deal with what I have best I can. I used all my money to buy this piece of shit and after my marriage left me with the shirt on my back I’m done. Thanks again.
FollowupID: 919381

Follow Up By: Frank P (NSW) - Friday, Apr 22, 2022 at 20:16

Friday, Apr 22, 2022 at 20:16
Sorry we couldn't help you, Kirk.

We could have given you some ammo to help with a fix, but without knowing what your setup is we cannot.

Good luck and safe travels.

Lifetime Member
My Profile  My Blog  My Position  Send Message

FollowupID: 919382

Follow Up By: Kirk L - Friday, Apr 22, 2022 at 20:23

Friday, Apr 22, 2022 at 20:23
Thank you very much frank. I know what the fix is and I can’t afford it. You helped me enormously. Unfortunately I’m on the bones of my arse and when my little money finishes so will I. Cheers. Kindest regards mate.
FollowupID: 919383

Follow Up By: Member - McLaren3030 - Saturday, Apr 23, 2022 at 08:43

Saturday, Apr 23, 2022 at 08:43
Hi Kirk,

Sorry for your troubles, just wish there was something more we could do to help. Even one extra solar panel would be of benefit if you could afford it.


Lifetime Member
My Profile  My Position  Send Message

FollowupID: 919387

Reply By: 1392 - Saturday, Apr 30, 2022 at 13:27

Saturday, Apr 30, 2022 at 13:27
Hi Kirk,
Sounds like you are experiencing 'information overload' on battery charging.
I have come across the same issue you are experiencing on a couple of occasions and many times the issue is related to having 2 or more batteries in parallel.
If one battery has one crook cell (eg sulphated or dry) then it will exhibit a higher voltage due to high internal resistance when being charged. This higher voltage will be detected by the charger and the charger then believes that the battery is approaching the gaseous stage or full charge and will reduce the charge rate. Under this scenario, none of the batteries will ever be fully charged.
A test you can do is to charge each battery individually, Do that by disconnecting the other 2. You need to disconnect all the load (fridge , etc). Charge each battery separately until they reach full charge (14,4V) before putting them all back into service at the same time. If one battery reaches full charge in a short time (compared to the other 2), it probably is toast.
AnswerID: 640390

Follow Up By: Kirk L - Saturday, May 07, 2022 at 19:09

Saturday, May 07, 2022 at 19:09
Yes a bit overwhelming. You say charge batteries separately. Someone else says charge up then separate overnight. It’s really difficult when living in the bush. May need to go to a caravan park and plug in to allow the full cycle of the charger rather than stopping it half way all the time as I think is is the main issue. Keeping a generator running all day. I can hook up a 300 w solar panel
Thru Anderson plug on caravan but I’m
Pretty sure this then goes thru a dc/dc charger. Don’t batteries only take charge at a certain rate? So by doubling my solar input how will this help. Will batteries take all this or does it just give more charging when sun isn’t as bright? Sparkly did say batteries seemed fine. I have run the generator for 6 hours the other day until had no fuel left. Voltage came up to 14.4 and showing absorb stage on charger. The when gen stopped it dropped to about 13 so just not sure I don’t need to keep charging but seems to take forever. Like I said maybe a caravan park and charge overnight and then get more solar watts to keep up there.
FollowupID: 919509

Follow Up By: 1392 - Sunday, May 08, 2022 at 14:15

Sunday, May 08, 2022 at 14:15
I understand your difficulty out in the bush. Definitely presents some challenges at times.
1. Connecting a solar panel to the Anderson connector on your caravan may or may not work. If, as you say, there is a DC-DC charger in that circuit, it may not even operate at all. A DC-DC charger is looking for an input voltage below 12V from a smart alternator. Modern vehicles incorporate a smart alternator that will charge the engine start battery up to full capacity, then shut down to around 9V. This reduces the parasitic load (via the alternator drive belt) on the engine thereby reducing fuel consumption. The DC-DC charger will start charging when it senses the voltage from the alternator drop and then take the low volts from the alternator and boost its output via an internal inverter up to the required voltage to charge your auxilliary batteries.
I assume the 300W solar panel has a charge regulator attached to it. I suggest you try connecting the solar panel regulator output directly to the battery, even if it was just a temporary connection to see if it works - making sure you get the polarity right!!
2. Batteries have an optimal charge rate based on their AH capacity but will take anything you can give them for a short period. Battery temperature is the limiting factor in most instances when over-charging. So no, batteries do not, in practical terms, only take charge at a certain rate. Your 300W solar panel will, in all probability, not deliver 300W output. What will limit the output of your solar charging system is the efficiency of the panel; regulators capability; ambient temperature (affects the solar panel); amount of solar radiation (from the sun) actually hitting the panel i.e angle and direction of the panel in relation to the suns position and your location (if your are in Launceston the suns rays travel further through the atmosphere compared to you being in Darwin). Clouds etc make a big difference so it is my philosophy that you cannot have too much solar!
3. If you had the battery bank get to 14.4V and then changed to the absorb rate with battery volts at around 13V - that sounds pretty normal to me. What it does not indicate, however, is what capacity your batteries have. The fact that hey have been into deep discharge (if that is true) then the probability is you will have lost some capacity. You will not correct any loss of capacity by adding a 4th battery - that would be throwing good money after bad.
It appears that you have the batteries up to their maximum capacity if you can get up to 14.4V at boost charge and maintain around 13V on absorb or float charge. That is as good as it will get for you.
Hope this helps.
FYI, I use 2nd hand household solar panels on my vehicle roof (1 off) and camper trailer (2 off) to charge the auxilliary battery in the back of the ute and house batteries in the camper. These panels have a much higher output voltage (around 42-44 volts) so require a higher voltage regulator such as Victron Energy 75/15. This will take up to 75 volts in and deliver 15 amps out. Cheap and simple. The household panels are strong (withstand hailstones) and very cheap on Gumtree. The big advantage is that you can have long extension leads so that you can place the panels out in the sun away from shade and not suffer the same voltage drop issues that the low voltage auto panels suffer.
FollowupID: 919519

Follow Up By: Kirk L - Sunday, May 08, 2022 at 16:02

Sunday, May 08, 2022 at 16:02
Thanks for that. Explains it pretty well my car is a 2002 patrol so no smart alt but it does charge from the car. I was thinking of trying the panels on the Anderson plug and if no good maybe wire up a separate Anderson direct to batteries. I haven’t bought a panel yet but vicroads do a 300 w fold up one which would be easier to store and handle but will have to be moved around to suit the sun which is no big deal really. I will also try other suggestions and certainly try a full over night charge when I can. I haven’t been able to find a wiring diagrams but might try contacting MDC who don’t like me much after all the warranty claims etc. anyway thanks. I have something to work on now and have a fair idea what I need to do.
FollowupID: 919521

Follow Up By: 1392 - Sunday, May 08, 2022 at 16:56

Sunday, May 08, 2022 at 16:56
MDC you say? Just looked up their specs and some of the MDC's use a 'Projecta IDC25' DC-DC charger. I have one in my vehicle (as well as the Victron solar regulator) and the IDC25 has a vehicle alternator input (in your case I presume that would be via the Anderson plug at the drawbar) and a solar input connection. Check to see if your DC-DC charger is this model. If it is, there are a couple of things you need to check =
1. What type of battery is it set for? The IDC 25 has different settings for 4 types of Lead Acid battery chemistries - Gel; AGM; Wet; and Calcium. You can access the instruction handbook at the web address below. If it is set for the wrong chemistry, that will affect both solar input and vehicle charging. N.B. You cannot charge with solar via the vehicle Anderson connector if you have this model!
2. If it is the IDC25 check the wiring into the charger and look for wiring connections as follows -

Alternator Input Cable (Red) 8mm2 (8 B&S) .... from vehicle Anderson plug.
Solar Input Cable (Green) 8mm2 (8 B&S) .... solar connector located somewhere in the caravan?
Output Cable (Brown) 8mm2 (8 B&S) ... POS connection to the batteries.
Common Ground (Black) 8mm2 (8 B&S) .... NEG connection to the batteries.
Ignition Override (Blue) 1-1.5mm2 ... may or may not be connected.
External LED (Pink) 1-1.5mm2 ... probably not connected.

The wires you are looking for are the 2 x green cables. If these 2 cables are not connected to any external wiring, you do not have any external solar connection. If the 2 green wires have external wiring connected to them, you need to follow the wiring to find out where they go to/are terminated. This is where you need to connect your solar panel input.

All of the above only holds true if you have the IDC25!
FollowupID: 919522

Follow Up By: 1392 - Sunday, May 08, 2022 at 17:11

Sunday, May 08, 2022 at 17:11
Sorry, there may only be 1 x green cable from memory. This would be the Solar POS. Read the manual if in doubt.
FollowupID: 919523

Follow Up By: 1392 - Sunday, May 08, 2022 at 17:24

Sunday, May 08, 2022 at 17:24
And more (having flashbacks now) the IDC2 has its own internal solar regulator so if you connect your solar panel to the green (POS) and black (NEG) wires, you need to do so without your solar panel regulator (i.e. wire direct to the solar panel before the regulator). Otherwise, just wire the output of your existing solar regulator to the battery direct.
FollowupID: 919525

Follow Up By: Kirk L - Sunday, May 08, 2022 at 19:45

Sunday, May 08, 2022 at 19:45
Wow that’s a bit over my head at the moment. I’m a fitter by trade lol
Thanks so much for your time. I will analyse and look into it all. When I first started out deep cycle batteries were Ron flat and recharge. Now AGMS another science. At the end of the day they are bo different. You have to look after them. Not sure about lithium yet but presume you can run those flat and recharge like a phone ?
FollowupID: 919527

Follow Up By: Member - McLaren3030 - Monday, May 09, 2022 at 09:48

Monday, May 09, 2022 at 09:48
Hi Kirk,

If looking at portable solar panels, the folding solar blankets take up much less space when folded, and are much lighter than solid panels.


Lifetime Member
My Profile  My Position  Send Message

FollowupID: 919530

Follow Up By: Kirk L - Monday, May 09, 2022 at 11:26

Monday, May 09, 2022 at 11:26
Yep that’s what I was thinking and can easily throw in can when packing up. Cheers.
FollowupID: 919533

Follow Up By: 1392 - Monday, May 09, 2022 at 11:58

Monday, May 09, 2022 at 11:58
Well Kirk, if you have learnt something about deep cycle batteries it is that you cannot run them flat. There isn't a lead acid, alkaline or lithium battery that you can run flat without some loss of capacity or creating a secondary problem (as in lithium).
Your phone (computer, tablet, etc) using lithium cells has 'battery management' software that continually monitors the state of charge (SOC) of the battery. When the battery has discharged to the point where it has exhausted the useable battery capacity, it shuts the device down to prevent over discharge and consequent battery damage.
Likewise, when charging, the battery manager monitors how much energy is put back into the battery to prevent over charging which can also cause some problems - like explosion and fire!
If you are considering Lithium for you caravan, the most important item to consider is the manager/charger. Lithium batteries are expensive and so are the manager/chargers. Lithium batteries can be extremely dangerous if they are used beyond the manufacturers specified limits so that is why it is imperative that a competent manager/charger be utilised.
I have Lithium Iron Phosphate batteries and a Redarc battery manager in my camper. The batteries save a bit of weight and the Redarc manager adds a shit load of complexity to my 'escape capsule' (the camper). I am not convinced that the cost and complexity of this arrangement outweighs the benefits of simplicity and a bit of extra weight of a lead acid battery arrangement.
My escape capsule is my life support system when out in the never-never. I have had the Redarc let me down twice now and had to limp home earlier than desired to facilitate repairs. Never ever had that experience with any other camper with AGM batteries.
FollowupID: 919534

Follow Up By: Kirk L - Monday, May 09, 2022 at 12:09

Monday, May 09, 2022 at 12:09
Thanks again. Just got broken bracket on my genset welded up free of charge by some good guys in Broome so had a win for a change. Anyway yes I’ll stick with the AGMS for now and be more vigilant on charging. Probably won’t be till I get to cairns that I can get any solar panels tho. See you on the road.
FollowupID: 919535

Reply By: Kirk L - Wednesday, Jun 15, 2022 at 09:42

Wednesday, Jun 15, 2022 at 09:42
Hi guys. Purchased a 300w regulated folding panel and have wired direct to batteries and all seems fine. Even being cloudy the batteries are fine and getting full charge now. Thanks again for all advice and help.

Ps. Just broke the chassis on my patrol. On Savannah way and hit a dip a bit hard. Was only doing 60 but it got me. Also have had a huge blowout and have destroyed several alloy rims and have swapped all to steel with a few new tyres so bank balance is now very low. Hopefully a few minutes of luck from now on. Happy travels.
AnswerID: 640882

Sponsored Links