Which Solar Regulator for AGM Batteries?

[aidancoughlan]

I am looking for a solar charge controller to regulate a 32W solar panel going into 2 * 110ah AGM batteries. I've been looking at 2 options

** MorningStar Sunsaver 10 amp ** $55 dollars
2 settings sealed, flooded
sealed regulation 14.1v, load disconnect 11.5v
flooded regulation 14.4v, load disconnect 11.5v

** MorningStar Prostar 15amp ** $94 dollars
3 settings Gel, sealed, flooded.
Gel, 14.0 regulation, 13.7 float, 11.4 load disconnect, 12.6 load reconnect
Sealed AGM, 14.15v regulation, 13.7v float, 14.35 equalisation, 11.5 load disconnect

From what I can gather, most people seem to use simpler regulators than either of these, so I am leaning towards the Sunsaver 10 - I've seen a reference suggesting to use this on the 'flooded' setting for AGM batteries, which surprises me.

Can anybody comment on this, or whether it is worth paying the extra 50 dollars for the Prostar model with the tailored AGM setting, and the 4-stage charging?
Also, if I ever added a Wind generator, would I need another regulator?


regard & thanks for any input,

Aidan.

 

[Anonymous]

I have the Morningstar Prostar 30 Amp (I have 360W of solar panels feeding 540 Ahr flooded lead acid). The actual voltages (on mine) are not as simple as the figures you have given. There is a 25 day calendar that remembers the history (so they say) and on the 'flooded' setting it says that it gives a 'vigorous' (14.9V) equalisation charge when required. It's all far more vigorous than I want given that we are on shore power at the moment, so the batteries never get discharged so I have set mine to the 'sealed' setting which has helped.

I have a BEP battery monitor and keep a close watch on the voltage as both the batteries and solar panels are fairly new. There are exactly the same issues with the engine alternator controller if you ever motor for long-ish periods, and the mains charger, if fitted.

The problem with AGMs is that they are sealed and contain very little water so if you overcharge them thereby overloading the mechanism that converts the H2 and O2 gasses back into water, the gasses vent off and the batteries dry out causing failure. If I had AGMs I would install a decent battery monitor (BEP or a Link, for example) and the best controls available. I think that my Morningstar set to the lowest setting (?'gel' or 'sealed') would be OK with AGMs.

 

[aidancoughlan]

Hi Lemain, many thanks for the input. I dont know why the figures I have are different - I got these from brochures on www.morningstarcorp.com/support. From browsing o nthe site, it seems they did a re-jig of the Prostar range some time ago, and introduced an extra setting for AGM batteries - I'll check on this again. I'm not sure why the Prostar does an equalisation phase with AGM batteries - I have read somewhere that AGMs dont need equalisation althoug it wont damage them. what you've said is enough to tip me towards the Prostar (higher of the two models I looked at), and maybe take a look at the Tristar which is the next one up.
I have a BEP monitor to be fitted also, so I hope this will help keep the new batteries in shape.

ps. you say "There are exactly the same issues with the engine alternator controller if you ever motor for long-ish periods, and the mains charger, if fitted."
- I have a Dolphin 15a 'smart' charger to install - I was under the impression this would handle charging of AGM batteries without killing them. I'm guessing you will have something similar - Is there still an issue, even with a smart charger?.
- I dont have a 'smart' alternator regulator (such as Adverc, Sterling,Balmar etc.) - would this overcome the issue of overcharging the AGMs when motoring for long periods? I was advised by Merlin that I dont need an alternator regulator since I am using a VSR, which I do not fully understand.

regards & thanks,
Aidan.

 

[Anonymous]

Hi Aiden,[ QUOTE ]
From browsing o nthe site, it seems they did a re-jig of the Prostar range some time ago, and introduced an extra setting for AGM batteries - I'll check on this again.

[/ QUOTE ]That would be the way to go; Morningstar are specialists and can be trusted, I think, although with batteries everything is a compromise so if you understand the technology and have the monitoring facilities (which you will have with the BEP) then it is nice to be able to fine tune according to your usage.

[ QUOTE ]
I'm not sure why the Prostar does an equalisation phase with AGM batteries - I have read somewhere that AGMs dont need equalisation although it wont damage them.

[/ QUOTE ]From my understanding of the technology, equalisation can be harmful if it results in gassing. Equalisation is the term given to describe forcing a charge into an already-charged battery to ensure that no individual cell is left uncharged. The inevitable consequence is gassing. In a flooded battery that means you have to add water, in a sealed battery of any kind the gasses should recombine as long as the rate of production does not exceed the capacity of the recombining system.

[ QUOTE ]
...what you've said is enough to tip me towards the Prostar (higher of the two models I looked at), and maybe take a look at the Tristar which is the next one up.

[/ QUOTE ] I think it would be worth considering, though check to see what you get. Some of the Moningstar controllers are the same as cheaper ones but with a display. If, like me, you have a BEP on the instrument panel and have mounted the controller in the engine room, the display is a total waste of money.

[ QUOTE ]
I have a Dolphin 15a 'smart' charger to install - I was under the impression this would handle charging of AGM batteries without killing them. I'm guessing you will have something similar - Is there still an issue, even with a smart charger?.

[/ QUOTE ]
Is this the mains charger? If so, then yes, I have an 80A Mastervolt. I have to fiddle with the dip switches to get the charge voltages the way I want them (13.3V on float, 14.4 for an hour after the charge is complete) though the Mastervolt has a fixed timer at 5 hours or so, not one. However 'smart' the charger if you understand the technology it is best to tell it what you want it to do - that will vary according to what you are doing with the boat i.e. mainly shore power, no shore power, or shore power in evenings only.

[ QUOTE ]
- I dont have a 'smart' alternator regulator (such as Adverc, Sterling,Balmar etc.) - would this overcome the issue of overcharging the AGMs when motoring for long periods? I was advised by Merlin that I dont need an alternator regulator since I am using a VSR, which I do not fully understand.

[/ QUOTE ]. First, VSRs. It's terribly straightforward, actually. Old fashioned systems having more than one battery bank used to be charged by blocking diodes - the diodes were to allow current to flow into both batteries as if they are one big bank, while stopping current from flowing out of both batteries together when off charge. The VSR - Voltage Sensitive Relay - switches all the batteries together in parallel to make one big bank, when charging but the relay drops out when the charging stops, leaving you with dedicated batteries (engine, House 1, House 2, etc.).

As for the alternator regulator, you will have a regulator - it is part of the alternator. Smart controllers such as ADVERC and Sterling override the standard regulator and if you wish you can wire the smart controller in such a way that if it fails you can go back to the standard regulator, manually or automatically. Sterling tell you how to do this. The VSR isn't really an issue with the choice of alternator controller although it is true that with a VSR you will get a more powerful charge than with blocking diodes this is because diodes drop 0.7V across them on full load and that power is lost. You can achieve the same thing by putting your battery switches to 'Both' when you are motoring then you don't need a VSR (remember, all the VSR does is to connect the batteries together when you are charging).

I haven't fitted a smart alternator control to my new boat although I had a Sterling on the old one and was delighted. I do have a new Sterling on board ready to fit if I feel like doing so. However, I have a 6kVA generator which we use a couple of hours a day plus 360W of solar plus quite a healthy charge from the engine so I may never bother. My standard alternator controller keeps the volts pretty high - over 14.5V - and I wouldn't want that on for three days if I was motoring if I had gels, sealed or sealed AGM. With flooded, you can always top-up with water. I suggest you keep an eye on the voltage and the charging current. If the current is very low then there isn't a lot of risk of gassing.

David

 

[andy_wilson]

Do you need a regulator?

32W = 2.66 Amperes (MAX) into 220 Ah of battery capacity.

In the real world, you are not going to have the panels at the optimum angle, AND facing the sun for all the daylight hours.
Neither are the daylight hours going to provide continuous sunshine in your neck of the woods.

Charging will be at best 1% of battery capacity, for a small part of the day.

Are the panels reverse flow protected to prevent discharge over-night? If so, forget a regulator, just wire in parallel and forget about it.

 

[ccscott49]

Re: Do you need a regulator?

I agree with Andy, as long as the panels are self discharge protected, with that battery capacity and that size panel, foprget a regulator, the other guy is talking about 360 watts of solar panels!! Not 32 watts.

 

[Anonymous]

Re: Do you need a regulator?

[ QUOTE ]
I agree with Andy, as long as the panels are self discharge protected, with that battery capacity and that size panel, foprget a regulator, the other guy is talking about 360 watts of solar panels!! Not 32 watts.

[/ QUOTE ]Be carefull, it isn't quite as simple as that. In practice the solar panels will be connected at the same time as the mains charger or engine alternator. The open circuit voltage of even a small 12 solar panel is nearly 20V, so given a fully-charged battery, wired to a mains charger that is switched on, there will be 32 Watts of power available to form gasses in the batteries. That is not insignificant.

If you are saying that you could dispense with a regulator and only plug the panel into the system when you need it, then yes, you could do that, and in effect you become the regulator. But it'll damage the batteries if you forget to unplug the panel. AGMs are not tolerant of overcharge - flooded would be less of a problem.

 

[aidancoughlan]

Re: Do you need a regulator?

Hi Lemain,
Many thanks for the detailed response. Seems like the 'smart' aspect of the mains charger will protect the batteries when under charge on shorepower, and a smart alternator regulator would do the same to protect them while motoring for longer periods.
I thought the comment about equalisation not damaging AGM batteries was a bit suspect for the same reason you mention - this makes perfect sense to me, and I have heard this line of reasoning before. (The original, probably not correct source was at http://www.windsun.com/Small_Systems/rv_solar_faq.htm)

Andy and Colin, thanks for the different point of view. I've a lot of respect for "the other guy"s input (lemain) from several past posts and this one, but this gives me something to think about as well. The particular panel I am thinking of is a Unisolar USF-32 flexible panel, primarily to be unrolled while the boat is unattended on a mooring, so I could act as regulator as Lemain suggests myself by unplugging it while motoring or on shore power, which will probably be my normal practice since it is not a 'permanent' mounted panel.

However, as far as I can gather, there is still the possibility that a fully charged battery left on the mooring with 32W panel input for several weeks may overcharge the batteries - and I am concious of the effect on AGM batteries, hence this post. (and I've read previous posts from different sources have suggested a rule of thumb that anything over around 10% of the battery capacity should require a regulator. ie. 100ah battery => anything over 10w panel needs regulator)

Also, the reason I am thinking of a 10-15 amp regulator instead of a 4amp say is to provide for adding some more panels in future, which would increase the need for a regulator.

I think I'll read up a bit more on the Prostar as suggested, and I might run this past my battery supplier to see what they suggest - I'll post if I get any usefull responses. Some day technology will be such that batteries will come with a built-in regulator, each tailored to the exact battery type!

 

[halcyon]

[ QUOTE ]
First, VSRs. It's terribly straightforward

[/ QUOTE ]

Slight simplification,, They can allow engine to charge service battery, or service battery to charge engine from say solar panel, provide link starting for engine from service battery, include power lockout to isolate an inverter to maintain minimum battery level, provide reserve power supply, include switching and regulation for solar panels / wind generators, with twin engines provide alternator redundancy, allow both alternators to charge a service battery, charge 2 / 3 / 4 battery banks, all from one unit.

Ref AGM batteries were back to how to charge them again, as some quote constant voltage charging, which means a simple top end regulator is all that is needed and multistage is not required. A case of check with your battery manufacture and see what there prefered charge sytem is.

Brian

 

[Anonymous]

[ QUOTE ]
Slight simplification,, They can allow engine to.............

[/ QUOTE ]Those functions have nothing to do with the 'voltage sensing' part of it. All the 'voltage sensing' does is to determine whether there is charging potential available and, in the simplest case, switch the batteries in parallel. Any other functions are ancilliary and specific to a particular system. It would be a shame if people got the idea that these things are so involved that they could never understand them - they are very simple and a keen amateur could design and make his own with parts from Maplin. Indeed, he might be well advised to do so.

 

[aidancoughlan]

Re: Which Solar Regulator for AGM Batteries? - think I\'ve found it

In case anyone else is looking for a solar regulator for charging AGM batteries, and is concerned about the exact voltages - it seems to me (after quite a bit of searching) that the Xantrex range provide the best flexibility.

In my case, the voltages they suggest in http://www.xantrex.com/web/id/61/docserve.asp for AGM's Bulk (14.1v)and Float(13.5v) match the recommendations from my Trojan batteries exactly, and seem allow you to 'tweak' the voltage settings manually. (The morningstars float at 13.7v, unadjustable)

Most other regulators I found did not have specific AGM settings, suggesting that you set them to 'lead acid' or 'sealed' which may approximate to the settings required by AGM batteries in general, and none had adjustable voltage point settings (ie. set your own to suit your particular battery manufacturers recommendations).

So there it is. I will probably go for the C12 (12amp) which seems to be the cheapest, and is big enough for my needs.

ps. Thanks for all the input so far. After weighing it up, I have decided to buy a regulator, but if I am overlooking something and making a mistake in the choice, please let me know!