Solar panel controller concerns

System

My goal is to use solar power to actively charge and maintain a 12v AGM deep-cycle battery that I'm using to power a trolling motor.

Here's the info from the battery manufacturer that I'm puzzling over:

If the controller outputs a constant current, even in a fully charged battery, it is ok if the voltage is 13.2-13.8v, 1 amp max. If the voltage or current is higher there is a risk of overcharging and damaging the battery.

If the charger goes into "sleep mode" when the battery is fully charged, we recommend that the charger "wakes up" at or above 12.6v.

I currently have a Sunforce 7 Amp charge controller that doesn't leave the 'charging' state. The 'charged' light never comes on, which gives me the impression that it's constantly sending 13 to 14.1 volts to the battery whenever the sun is shining. Which I'm pretty sure is a bad thing. This controller is not a PWM controller (doh!).

Does anyone know what battery voltage this controller is looking for to determine if the battery is fully charged?

I'm considering getting the entry-level SunGuard controller to replace it, which sounds like a much better unit. However, as I understand it, the SunGuard controller sends 14.1 volts to the battery, which is more than the 13.2-13.8 volts recommended by the battery manufacturer, once the battery is charged.

Is there a controller that will send the correct (13-ish) voltage to the battery once it is charged?

Is it safe in terms of battery longevity to leave either of these controllers attached to the battery year round?

Thanks!

Jeff

2manytoyz

Re: Solar panel controller concerns

Actually, the better charge controllers bump the Voltage up to ~14.4V during the peak of the day. Furthermore, they can also equalize the battery(s) typically once per month automatically, which is ~15V.

Here's the datasheet for my charge controller, which shows the various voltages used during each stage of charging: http://www.morningstarcorp.com/en/support/library/PS2.DAT.Datasheet.01.EN3.pdf

A battery sitting on a grid powered trickle charger can actually kill the battery in a year. Learned this the hard way. What can happen is stratification of the battery fluid. The acid/water can separate somewhat, causing uneven battery chemistry across the plates. I reseached this topic after my battery died.

When the battery is brought up to a higher charge rate, or eventually to a higher voltage (with a small array), the batteries will gently bubble, causing the solution to mix. It's much healthier for the batteries. This is different than overcharging and boiling a battery.

Each day the sun is shining brightly, my ProStar controller brings my bank up to 14.2V. A check of the specific gravity of each of the cells shows they are fully charger equally.

Also keep in mind that this higher voltage only occurs during the peak of the day. Most of the day, the voltage is lower.

Here's the small solar panel I installed on my boat: http://2manytoyz.com/solarcharger.html

Dapdan

Re: Solar panel controller concerns

toyz,

you need to realise that he is quoting the manu recommendation for a vrla type battery. so he should not equalise is as you had mentioned. he would need a controller that he can adjust the bulk voltage setting so he does not exceed the manufacturer's recommended voltage.

for your battery, bud, you are going to need a good CC that you can adjust the bulk voltage and float settings. If you want to leave it on all year round it would be recommended to get one with a battery temp sensor so that it make adjustment on bulk and float setting all through the year and you should be good.

According to your quote the manufacture is advising you of the float voltage (13.2-13.8v). You are going to need a recommended bulk voltage(for 12v agm it is usually between 14.1 and 14.4 depending on manu recommendations)


Cheers...
Damani

Windsun

Re: Solar panel controller concerns

The 14.2 to 14.4 volts that the Morngingstar controls go into when the see that the battery is full is not steady, it is PWM - I have seen new AGM's with very low self discharge only pulse for 1-2 seconds every several minutes.

While most of the highe end controllers have flooded/gel/agm settings, most are quiite a bit more than the standard controllers, and it simply does not make sense to buy a $200 controller for a $150 battery to get an extra month or two out of it.

mike95490

Re: Solar panel controller concerns

AFIK, the sunforce / http://www.amazon.com/gp/product/B0006JO0XI /
is a $30 controller, with no usable specs listed.
http://www.sunforceproducts.com/prodinfo/manuals/SunforceSolarManEng.pdf
the manual only says the 14.2V disconnect voltage.

I would not place a lot of hope in this product, but am glad your AGM battery still works.

Look for a controller that has settings for AGM batteries, and preferably has 3 stages of charging.

With AGM, you do not need to worry about electrolyte stratifaction, as it's not a concern in AGM styles. What's a concern, is that you do not try to equalize the battery, as that is generally BAD for AGM.

System2

Re: Solar panel controller concerns

That's for all the feedback!

I bought and installed the SunGuard controller. It seems like a really high-quality product. I like that it does not have indicator lights built in, so i won't know what it's doing and be tempted to overthink it.. I'm going to leave it attached to my 15 watt solar panel and battery all summer and hope for the best.

If anyone wants a good deal on a Sunforce "chinese junk" controller, lemmie know. :-D

Thanks again,
Jeff