Thread: AGM Battery Charging

I looked into that a bit, not being any kind of expert I should add, and concluded the best way was to separate two batteries with a battery controller (a Traxide in my case), so one is being charged by the alternator to run the vehicle and, when its charged, the controller links the two together. The Traxide allows some of the charge in the starting battery to be drawn on to run the fridge, so I effectively have about `1.4 batteries.
I can use the solar panels to directly charge the second battery, without affecting the charging of the first battery by the alternator.
Charging the house battery by both the alternator and the solar at the same time sounds a bit likely to cause problems.
Incidentally, don't your solar panels have a regulator to prevent overcharging?
Be interested to know what others think.

Originally Posted by pjlhat

Hi Tim
Revisiting my origial post about charging AGM Batteries. I do not wish to use my cranking battery at all for the compressor fidge I have installed in my slide on Trayon camper so no need for the SC80 12v controler.
What I have is the alternator charging two 100amph AGM house batteries through a 30 amp circuit breaker. I also have a stand alone 120 watt folding solar panel with what appears to be a built in regulator, plus two 80watt panels mounted on the the roof of the Landrover un regulated that I manually control with an isolating switch depending on the battery voltage that I have metered. Un able to test the batteries for specific gravity, my battery supplier tested the batteries with some fancy gear and said they were about 50% and that the above set up was not charging the house batteries?? that panels and alternator would be working against each other!! The batteries are new but I am unable to get 3 days of fridge power even with the solar units helping out as sun permits.

Any advise would be greatly appreciated, thanks for your time.
Peter

Before I installed the Matson DC-DC charger I found the charge from the vehicle was not charging the battery in the camper enough while I was driving with it plugged into the trailer plug and the Engel fridge was running off the AGM battery, maybe because of voltage drop down the wiring to the trailer battery. The Matson bumps the charge up to 20 amps while the engine is running. The Engel fridge is running off the battery in the camper, but cycles on and off. Now it seems to work fine.

Hi Peter, We have a similar setup to you on our OKA. ie. two roof mounted solar panels and a separate vehicle battery(s) and two house batterys. I had a portable fold up panel of 140 watts but no longer use it was unnecessary.


I assume you have a compressor type fridge (eg. Engel/Waeco) and not one of the power hungry 3 way type fridges ? Whilst these can be quite good on gas they are murder on batterys and not suitable for prolonged use on batterys.


I would suggest you have another look at Tims circuit in post 4 with particular regard to the cable size and the 50 amp breakers.


I am assuming you have relay switched the power from the alternator to the house battery so as to isolate it from the vehicle battery which is good but when you say the relay is powered from the alternator light I guess you mean it's activated from either the ignition or the alternator pulse output to the tacho ?? ie. engine running = relay operated, engine off = relay off ?


Assuming the above I'd suggest you diode the 80 watt panels (if they're not already) for their protection and connect them to a suitable solar controller. I'd replace your relay with at least a 50 amp rated change over relay using Tim's circuit with the relay replacing the SC80 which as you say you don't need. I'd connect the output of the solar controller to the normally closed side of the relays change over contacts and the alternator output/vehicle battery to the normally open side of the change over contacts. The centre contact goes to the house battery.


This configuration allows the vehicles alternator to charge the house batterys when the engine is running with automatic change over to the vehicle mounted panels when the engine is off.


This is the configuration I have and it works very effectively for us. A variation we have is a simple switch in the operate path of the relay so that the solar panels can be connected to the house battery only and it's not switched to the alternator when the engine starts. I built this in as an option but haven't used it as the system worked fine as it was from day 1. Another variation I built in was a second relay to isolate the solar panel output from the solar reg when the house battery charging source was the alternator, but I don't know if this is really necessary.


You mention that your portable panels "appear to have a built in regulator", which is a bit of a worry. From my experience the stuck on the back regulators are usually of very low quality, indeed if you have one.
Whilst I'm merrily spending your money , why not buy two regulators the same ? one for the roof mounted 160 watt and one for the 120 watt portable panels. This way you would be able to fault find/swap if need be as long as both regs were both rated at a min of 160 watts.


The portable panels reg could be left mounted in/on the camper with a suitable plug to connect the panel directly to it. For good results it is best to have the portable panels solar reg as close to the house battery as possible.


Check that the chassis earths of the batterys and appliances are all good. Is there a separate earth connecting the trayon to the Landy chassis ?


As I said at the start we have this setup (with a few extras) on the OKA and it works fine for us.




Deano

Originally Posted by pjlhat

that panels and alternator would be working against each other!!

Hi Peter and I don't know why an EXPERT would tell you that having power from an alternator and a solar regulator feeding into the same battery would work against each other.

Mate, that is pure fiction and the 'EXPERT' that told you that might be an expert at paining fences but they sure as hell know nothing about auto electrical charging systems or how to charge batteries.

From what you have posted, and as I have already pointed out, your charging problems sound like they are being caused by grossly undersized, and any EXPERT should have picked this up in the first place.

You need to sort that out before you do anything else.

Next, it is actually an industry standard to have power from an alternator and a solar regulator feeding into the same battery, and it does not cause any form of problems.

Last but not least, you need a solar regulator on that 80w solar panel on the roof of your land rover because if you forget just once, you will cook your batteries.

An 80w solar panel can force the terminal voltage of any form of lead acid battery to over 17v and if this is left unchecked for a while, just a few hours, you will permanently damage the battery.

Originally Posted by drivesafe

..................................An 80w solar panel can force the terminal voltage of any form of lead acid battery to over 17v and if this is left unchecked for a while, just a few hours, you will permanently damage the battery.

Even worse when there's two of them




"...................................... plus two 80watt panels mounted on the the roof of the Landrover un regulated ............................"




Deano

[QUOTE=DeanoH;2324316]Hi Peter, We have a similar setup to you on our OKA. ie. two roof mounted solar panels and a separate vehicle battery(s) and two house batterys. I had a portable fold up panel of 140 watts but no longer use it was unnecessary.


I assume you have a compressor type fridge (eg. Engel/Waeco) and not one of the power hungry 3 way type fridges ? Whilst these can be quite good on gas they are murder on batterys and not suitable for prolonged use on batterys.


I would suggest you have another look at Tims circuit in post 4 with particular regard to the cable size and the 50 amp breakers.


I am assuming you have relay switched the power from the alternator to the house battery so as to isolate it from the vehicle battery which is good but when you say the relay is powered from the alternator light I guess you mean it's activated from either the ignition or the alternator pulse output to the tacho ?? ie. engine running = relay operated, engine off = relay off ?


Assuming the above I'd suggest you diode the 80 watt panels (if they're not already) for their protection and connect them to a suitable solar controller. I'd replace your relay with at least a 50 amp rated change over relay using Tim's circuit with the relay replacing the SC80 which as you say you don't need. I'd connect the output of the solar controller to the normally closed side of the relays change over contacts and the alternator output/vehicle battery to the normally open side of the change over contacts. The centre contact goes to the house battery.


This configuration allows the vehicles alternator to charge the house batterys when the engine is running with automatic change over to the vehicle mounted panels when the engine is off.


This is the configuration I have and it works very effectively for us. A variation we have is a simple switch in the operate path of the relay so that the solar panels can be connected to the house battery only and it's not switched to the alternator when the engine starts. I built this in as an option but haven't used it as the system worked fine as it was from day 1. Another variation I built in was a second relay to isolate the solar panel output from the solar reg when the house battery charging source was the alternator, but I don't know if this is really necessary.


You mention that your portable panels "appear to have a built in regulator", which is a bit of a worry. From my experience the stuck on the back regulators are usually of very low quality, indeed if you have one.
Whilst I'm merrily spending your money , why not buy two regulators the same ? one for the roof mounted 160 watt and one for the 120 watt portable panels. This way you would be able to fault find/swap if need be as long as both regs were both rated at a min of 160 wa

Thanks Deano, Yes I use the ignition light to activate the relay to charge the house batteries and yes we replaced th

Originally Posted by drivesafe

Hi Peter and I don't know why an EXPERT would tell you that having power from an alternator and a solar regulator feeding into the same battery would work against each other.

Mate, that is pure fiction and the 'EXPERT' that told you that might be an expert at paining fences but they sure as hell know nothing about auto electrical charging systems or how to charge batteries.

From what you have posted, and as I have already pointed out, your charging problems sound like they are being caused by grossly undersized, and any EXPERT should have picked this up in the first place.

You need to sort that out before you do anything else.

Next, it is actually an industry standard to have power from an alternator and a solar regulator feeding into the same battery, and it does not cause any form of problems.

Last but not least, you need a solar regulator on that 80w solar panel on the roof of your land rover because if you forget just once, you will cook your batteries.

An 80w solar panel can force the terminal voltage of any form of lead acid battery to over 17v and if this is left unchecked for a while, just a few hours, you will permanently damage the battery.

Is that also true for AGM batteries?

[QUOTE=DeanoH;2324316]I assume you have a compressor type fridge (eg. Engel/Waeco) and not one of the power hungry 3 way type fridges ? Whilst these can be quite good on gas they are murder on batterys and not suitable for prolonged use on batterys.


Thanks Deano,
I will take a while to digest all the info and may come back for some clarification latter.
Yes I do use the ignition light to activate the relay and yes we have replaced the Gas fridge with a wako 90 litre compressor fridge.
Thanks again.