Charging gel batteries off-grid

[CosmickGold]

I have two -- nearly new -- large 12v gel batteries from an electric wheelchair that "bit the dust".  So would like to use these two monsters in my rig.

Currently, I'm looking for a way to charge them off-grid.  Data I've found says gel batteries must be charged slowly, at a lower voltage than other batteries, and NEVER be overcharged since overcharging will kill them. 

Since they charge slowly, and for a long time, that rules out asking someone to let me "plug in" for a few minutes.  It also means not using a gas generator "slowly" eating fuel all day and night.   Which seems to leave solar panels as the right charging source, since they will be slow, quiet, and waste no fuel.

Well, I've been looking at small solar systems for this purpose, but the ads just say they include "battery charger"; nothing about providing the special needs of gel batteries.  So that's where I'm stuck.

Anyone know of a low-cost, slow-charging, solar system, specifically tailored to the special needs of wheelchair gel batteries?

 

[highdesertranger]

hopefully someone will chime in. from what I have heard gel batteries are a poor choice for off grid systems. highdesertranger

 

[CosmickGold]

from what I have heard, gel batteries are a poor choice for off grid systems.

Thanks for the tip, that I might very well be barking up the wrong tree.
They seem mighty heavy to be lugged around everywhere I go, anyway.

Do you remember specifics of the WHY they are "a poor choice"?
Or perhaps, where you found that info?

 

[highdesertranger]

very temperamental with charging. highdesertranger

 

[CosmickGold]

OK.  I think I found some of the problems you were talking about at this SolarTown web page.

So really, I should forget about these gel batteries I own.  Instead, I believe I should get a battery that matches the one that starts my engine. Then I can simply turn on the rig's engine to charge them both from the alternator.  Won't take much gas to do so since their kind charges really quickly. I just need to install a solenoid to keep the batteries separated when the engine is off.

That's probably both the most simple -- and the most solid -- solution.
I do have the $350 charger for the gel cells, but it requires a 110v source!

 

[deadwood]

I would look up to see what the battery manufacturer has to say about charge rates for them. I have a Fullriver AGM battery and I always read how AGM's need to charged at a lower voltage then Lead Acid batteries. When I bought the battery I wanted to make sure I was charging it properly and when I looked up the spec's for it on the Fullriver website I was surprised to see that the bulk charge rate for my battery was 14.7 volts.

But that's what it takes to properly charge mine up and that is my setting. My float charge is 13.6 volts. I was able to find a setting on my charge controller that matched almost perfectly even though the setting was a default setting for Lead Acid batteries.

Once you find out what the manufacturer says is the proper charge voltage then you can figure out what you need to do to best charge them that way. It will give you a full charge and it will give you the max life out of the batteries.

 

[deadwood]

OK.  I think I found some of the problems you were talking about at this SolarTown web page.

So really, I should forget about these gel batteries I own.  Instead, I believe I should get a battery that matches the one that starts my engine. Then I can simply turn on the rig's engine to charge them both from the alternator.  Won't take much gas to do so since their kind charges really quickly. I just need to install a solenoid to keep the batteries separated when the engine is off.

That's probably both the most simple -- and the most solid -- solution.
I do have the $350 charger for the gel cells, but it requires a 110v source!

I just recently added a Voltage Sensing Relay to my van. I was using solar only in the beginning but found out on my first trip to the pacific NW that solar only is not enough. I found the VSR on amazon for about $90 and it was super easy to hook up. The relay opens automatically and closes when the voltage drops so there is nothing you need to do. Mine puts a lot of amp's into the battery very quickly while I am driving. I wish I would have hooked one up right when I built out my electrical.

 

[John61CT]

Nothing wrong with GEL batteries for off-grid use, if good quality and properly cared for they can last longer than AGM.

Key is getting mfg specs and adjustable charge sources. High amps is fine but keeping voltages within mfg spec is critical.

All decent solar sources let you customize the charge profile, some require an addon gadget for that.

Mains charger (shore power or genny) I recommend Sterling ProCharge Ultra or ProMariner Pronautic P, or if manually watching a quality adjustable power supply.

From alternator, use a Sterling DC-DC "BB" model.

All lead chemistries require 4-8 hours to fully recharge from depleted, which you should be doing at least a few times a week.

Off-grid I would either drive with a good Alt/VR setup, or a genny run, until bank is at 80-85% SoC, maybe as long as 4 hours depending on Amps available. Complete this stage by early AM, then let solar finish the lower amps "long tail" rest of the day.

Make sure to keep Absorb voltage until mfg spec endAmps, or .005C, .5A per 100AH bank size.

If you see this point is reached very early in the afternoon, then next time don't need the dino juice to run so long, obviously depends on conditions. A good Battery Monitor can help you get familiar with the patterns to get better predicting.

None of the above is unique to GEL, just that normal cheaper charge sources are factory set to the other more common chemistries, and GEL is just more easily seriously damaged by abuse.

 

[Spaceman Spiff]

John61CT beat me to it with a more complete answer while I was looking at my Morningstar TS-45 Operator's Manual.  Since you already have the batteries you might as well use them.  The Morningstar manual says you can charge GEL batteries and gives limited instructions on settings.  But getting the manufacturer's settings is sound advice.

 

[John61CT]

Don't assume the canned profile settings match your model batts.

Best to get charge sources that allow fully user customizable setpoints. You want flexibility choosing a different chemistry in the future.

That sort of infrastructure may last longer than your vehicle, while banks are relatively short-lived consumables.

Especially if second-hand.

 

[CosmickGold]

I just recently added a Voltage Sensing Relay to my van. I was using solar only in the beginning but found out on my first trip to the pacific NW that solar only is not enough. I found the VSR on amazon for about $90 and it was super easy to hook up. The relay opens automatically and closes when the voltage drops so there is nothing you need to do. Mine puts a lot of amp's into the battery very quickly while I am driving. I wish I would have hooked one up right when I built out my electrical.

This sounds important, as well as simple.  But had never heard about it.  Info online explained:

Relay is engineered to help protect equipment operating ... within an upper and lower range against equipment burnout and brownout conditions. As long as the monitored voltage remains between the adjustable Over Voltage and Under Voltage settings, the internal relay stays energized. If the monitored voltage falls outside this range, the relay will drop-out.

What is it protecting?
Where do you wire it in?
I see a lot of VSRs on eBay, so which model did you buy?
My guess is that it protects everything that runs off the house battery, from both low battery AND the high charging voltage. So it must go between battery and ALL applications.  But that it does NOT affect the connection between house battery and engine battery, which is a solenoid closed circuit while driving, and open when parked.  Am I right?
PS --  I'm really glad you told me about this, deadwood.  I had not even thought of such problems or needs.

 

[deadwood]

This is the one I got on Amazon. I can't speak to it's reliability but it got good enough reviews that I decided to give it a try.

https://www.amazon.com/Smart-Batter...pID=51JYwSwicbL&preST=_SY300_QL70_&dpSrc=srch

It was pretty easy to install. It basically connects the starting battery to the house battery. I had some 6gauge wire made up to connect it all. One wire goes to the starting battery positive. One wire goes to the house battery positive with the VSR in the middle. There is also one negative wire to run to ground. I ran that one to my negative bus bar so that my battery meter can read the amps coming in.

For safety I did run the wire through a 100 amp fuse on both sides as close to each battery as I could get. If something were to ever go wrong or if I was in an accident I want the fuse to blow to protect the system and the van. This fuse is more worst case scenario but I wouldn't install without it.

As for what the VSR protects. It protects the starting battery from being run down while you are using your house battery to run your electronics in the back. When the van starts the batteries are separated. No voltage can go between them. When the starting battery gets to 13.4 volts the relay will see that and open up. As soon as that happens the amps start flowing to the house battery to give them a lot of amps while I'm driving. When I turn the van off or if my starting battery drops to 12.9 volts the VSR sees this as well and will close. That way while I am using my electricity in the back there is no way to run down my starting battery and maybe leaving me stranded.

The VSR gives me a lot of amps to fill my battery while driving but will never get my batteries fully charged though. That's what my solar panel will do. I can get charged up to 80-85% a lot quicker with the VSR and then the solar will do it's thing and get me the rest of the way.

I will say that I was very interested in the Sterling b2b charger. But they are expensive and I wasn't sure how much I really needed one. If the VSR works to put the amps in and the solar tops me off I will be happy with this system. It's still new and I'm still testing it out to see how well it will work. So far it looks to work really well but I need to try it when I'm not getting too much sun to see if it will all keep up. For $80 bucks and some wire and fuses this set up cost about $100 and was easy to install.

One other thing I read about the VSR. It will open in either direction. There are times that I might leave town for a few weeks at a time and leave the van parked. My solar does do a great job at charging my house battery. But the VSR will also see that my house battery is getting above 13.4 volts. When this happens it should open the relay and then my solar will actually be sending some volts to my starting battery to keep that fully charged as well. I'm not sure how often this will happen but it is nice to know that I most likely won't be coming back to a dead starting battery.

My last thought on the VSR: I don't think using just the VSR would be enough to properly maintain my house battery. My Fullriver battery calls for a bulk charge of 14.7 volts. I don't think the relay will be passing though enough voltage to get me fully charged. But it does a fantastic job of getting a lot of amps in quickly so that solar can then take over and put the higher voltage in and slowly get me up to 100%. Neither one alone is really enough for my system. But working together I think the VSR and the solar complement each other so well that I will be using this battery setup for years to come.

 

[John61CT]

There is one main function of a VSR, aka ACR or "combiner".

Connect or isolate two circuits, one with the vehicle stuff and Starter battery, the other with House (aka Auxiliary) bank and loads.

When a charge current appears (usually sensing either circuit, aka "dual sense", a higher voltage) then close (or join, combine) the two, charging is shared.

When voltage drops (charging stopped) then open / isolate, disconnect, so House loads don't draw Starter SoC down.

That's it.

If you need Cranking currents to cross the device (self-jumpstarting) you need high amps capacity.

This is the best one ​ https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

Will last longer than your vehicle, never break.

There are also ignition relays and DCDC chargers, different approaches for different needs.

Originally "isolators", based on one-way diodes were used, now basically replaced by the above.

 

[DLTooley]

Using an inverter to power your existing charger is a bit redundant, but if you already have the inverter definitely worth trying. If you don't have one comparing to programmable solar charge controllers would be in order. This sounds like a great project to put your solar/12v electrical knowledge to a test.

 

[CosmickGold]

[font=Verdana, Arial, sans-serif]DLTooley[/font]
[font=Verdana, Arial, sans-serif]Using an inverter to power your existing charger is a bit redundant, but if you already have the inverter definitely worth trying. If you don't have one comparing to programmable solar charge controllers would be in order. This sounds like a great project to put your solar/12v electrical knowledge to a test.[/font]

John61CT

Where do you get this stuff?
Not "a bit redundant" but looney toons inefficient.
Feel free to experiment with science projects and report observed results in your own thread, but please don't lead even less experienced newcomers into dead-end paths just based on "well that might be interesting" speculation.

Hmm.  Well.  This is my thread, and I wasn't at all unhappy with what Tooley said.  It was food for thought.

By "redundant" (which I just looked up and found it means "unnecessary repetition in expression") I assumed he meant converting the gas engine power to AC in the alternator, only to convert it to pulsating DC through the alternator's diodes, to then convert it to stored chemical energy in the engine battery, to convert it again to 60 AC in the inverter, to convert it once more to DC charging voltage in the battery charger, to convert it to chemical energy again in the house battery, to convert it to light by the simple flip of a switch.  "Ta da!"  So simple  

Further, I think his idea of "putting my electrical knowledge to a test" is a great idea, lest I find myself alone in the wilderness where the call of the "Oh No" bird echos helplessly through the trees, accompanied only by the sounds of other birds, for miles and miles....

 

[GotSmart]

I have four Fullriver sealed AGM running on a Renogy Commander/tracer System.  These are FIVE years old and running strong. 

Setting up a Solenoid for boost charging while driving long distances is a great idea. 

Those canned responses about only getting solar in during a few hours is garbage. It starts out slow, then builds in intensity then gradually drops off. That is why those useless you tube videos never agree with each other. A cloud a mile up changes your readings. Numbers constantly change.  The proof comes in from the system working.   I am currently using panels that show potential from the moon.  The type of panel makes a huge difference. 

Fact. You need twice the amount of panels in the PNW as in Quartzsite to collect the same amount of energy. Denver has a much greater power potential than LA.

 

[CosmickGold]

Thanks, GotSmart. I had wondered why the panels seemingly required direct sunlight, or wouldn't charge at all. Glad to know it's a sliding scale. You said it depends on the kind of panel. Really? What are the different kinds? (... and prices for them.)

I mean, from memory; not asking you to go look things up.

 

[John TF]

Buying good quality , brand name products , is the start , especially if you are not familiar what your doing .
Buying the cheapest stuff off Amazon / where ever , can work , if you know more about all this stuff .
The good stuff will allow for a programable charger , some times [ in this case ] you have to find one that allows for multiple charging sources .

 

[GotSmart]

Thanks, GotSmart.  I had wondered why the panels seemingly required direct sunlight, or wouldn't charge at all.  Glad to know it's a sliding scale.  You said it depends on the kind of panel.  Really?  What are the different kinds? (... and prices for them.)

I mean, from memory; not asking you to go look things up.

First thing you need to know is gathering advice on the internet from unproven sources is dangerous. 

I will send you a PM