GEL batteries and TOPOINT panels

Tonygreen

Greetings

I would appreciate your opinions on these 2 products:

1. Gel batteries (specifically DEKA MK)
2. Topoint solar panels (I noticed that NAWS is selling them, so my initial impression was that they may be good, since in the past NAWS had refused to sell low quality Chinese panels)

Thanks

BB.

Regarding GEL batteries, especially those made in the US (European GEL batteries can be "different")... In general, GEL batteries are designed to have a maximum of C₂₀ (5%) maximum rate of charge. If you charge them any faster, they can "gas" and develop permanent gas bubbles in the GEL--Which ruins the batteries.

For Solar power, 5% maximum rate of charge is pretty slow (low) charging rate given that we have a limited number of hours per day of available sunlight. In general, an off grid power system used daily does much better with a C₁₀ or C₈ (10% or ~13%) rate of charge for solar. Especially if the system is used in winter (few hours of sun per day).

-Bill

Tonygreen

BB. wrote: »

Regarding GEL batteries, especially those made in the US (European GEL batteries can be "different")... In general, GEL batteries are designed to have a maximum of C₂₀ (5%) maximum rate of charge. If you charge them any faster, they can "gas" and develop permanent gas bubbles in the GEL--Which ruins the batteries.

For Solar power, 5% maximum rate of charge is pretty slow (low) charging rate given that we have a limited number of hours per day of available sunlight. In general, an off grid power system used daily does much better with a C₁₀ or C₈ (10% or ~13%) rate of charge for solar. Especially if the system is used in winter (few hours of sun per day).

-Bill

BB

Thanks for editing my post. Accept my apologies.
Now, regarding those Topoint panels, anyone has used/installed them? Are they as good as my old Kyoceras? (9 years ago I paid $600 apiece for Kyoceras 140 watts!!!!!).
In addition, will AGM batteries tolerate faster/higher charging rates?

BTW: My intentions were to replace my flooded batts (5 years old) with gel or agm's, because I thought they lasted more. My flooded bats life span has been around 4-5 years. (Golf cart batts.)

BB.

No problem...

AGM batteries are a much nicer Lead Acid battery... Much higher discharge and charging current capabilities. No acid mist/hydrogen gas release (DURING NORMAL OPERATION).

However, AGM batteries tend to be 2x as expensive and probably last a couple years less than "similar quality" flooded cell lead acid batteries (maybe a typical 5-7 year life for well cared for AGMs--At least that is my guess, others please chime in). AGM's tend to be more sensitive to over charging (venting gasses/water that cannot be replaced/overheating and wearing out catalysts). And AGM batteries, being sealed, you cannot measure their specific gravity/state of charge.

If you want a "cleaner battery" with higher surge current capabilities, AGMs are certainly a very nice battery. I would not suggest them to a person going off grid for the first time, but since you got ~5 years from your golf cart batteries--You have learned a lot about the care and maintenance of lead acid batteries.

-Bill

Tonygreen

OK
Thanks again, Bill.

Tonygreen

I ended up buying 4 DEKA 8L16 to replace my aging golf cart battery bank.
I have emailed the company several times, to know the recommended charging rates. So far, no answers.

Can anyone tell me what are the optimum charging (bulk, absorbing, float, and equalization) rates for these batteries?

4 DEKA 8L16; 6 volts each, wired in series for a 24 volts bank. 370 amps each.
Outback MX 60 controller
Room temperature in the room where the batteries are located averages 88F from June until October.

Fisherguy

Does anyone know anything about Topoint Panels?
Did you find out anything Tony, I know they are pretty cheap and made in China.

BB.

You can search the forum for Topoint panels by going to Google and typing in:

• site:forum.solar-electric.com topoint

The "Site:" tag will limit searches to our forum here.

-Bill

waynefromnscanada

Tonygreen wrote: »

I ended up buying 4 DEKA 8L16 to replace my aging golf cart battery bank.
I have emailed the company several times, to know the recommended charging rates. So far, no answers.

Can anyone tell me what are the optimum charging (bulk, absorbing, float, and equalization) rates for these batteries?

4 DEKA 8L16; 6 volts each, wired in series for a 24 volts bank. 370 amps each.
Outback MX 60 controller
Room temperature in the room where the batteries are located averages 88F from June until October.

Solar charging info from the manufacturer is found here: http://www.mkbattery.com/documents/6427Renewable%20Energy%20Charging%20Parameters%20Rev%204.pdf

drift211

Hello Bill,

I am new and learning about batteries. Could you please explain the C_20, C₁₀, C₈ rating relating to the maximum rate of charge.

BB. wrote: »

In general, GEL batteries are designed to have a maximum of C₂₀ (5%) maximum rate of charge.

BB. wrote: »

In general, an off grid power system used daily does much better with a C₁₀ or C₈ (10% or ~13%) rate of charge for solar.

BB.

For our foru₂₀m--When we talk about the battery's Amp*Hour capacity--We use the 20 Hour Discharge Rate --- Basically if you discharge a battery from 100% to 0% state of charge-- I.e.,

• 5 amps * 20 Hours = 100 Amp*Hour capacity.

That is the "real" C₂₀ that we talk about here... If you discharge a lead acid battery faster (for example a 10 hour or 5 hour discharge rate), the apparent Amp*Hour capacity of the battery bank is less (rest of capacity is wasted as heat and chemical process inefficiency).

Then there is the Rate of charge... Some folks here like the C_x as a quick way to talk about rates:

• C_x = C * 1/x
• C₂₀ = C * 1/20 = C * 0.05 = C * 5% rate of charge (where "C" is the 20 hour rated capacity of the battery bank)
• C₁₀ = C * 1/10 = C * 0.10 = C * 10% rate of charge
• C₈ = C * 1/8 = C * 0.125 ~ C * 0.13 = C * 13% rate of charge
• C₅ = C * 1/5 = C * 0.20 = C * 20% rate of charge

For flooded cell deep cycle lead acid batteries, 5% rate of charge is the minimum for proper recharging. 10% is a good nominal number (and some battery mfg. use it as the "minimum" rate of charge). And C/8 or ~13% tends to be about the maximum before batteries can overheat (is also still relatively efficient charging).

20% to 25% rate of charge can be done (frequently with AC mains or Gensets), but you need to monitor the battery bank temperature and, for a genset, you can use the higher rate of charge for 80% or lower State of Charge--As you get over ~80-90% state of charge, you need to pull back on the current (or use absorb set point for charging) to "bulk charge" the battery quickly and fuel efficiently.

Each battery chemistry/type has its own "optimum" range of charging currents.

Does that help?

-Bill

drift211

Thanks Bill,

So let me see if I understand this correctly.

A C₂₀ battery that had a 50% charge would 6 hours to charge up to 80%.
A C₁₀ battery that had a 50% charge would 3 hours to charge up to 80%.

BB.

"It depends" is always the answer with batteries...

Just to do this in round numbers... The C₂₀ capacity of our mythical bank is 300 Amp*Hours at 12 volts.

Nominally, we recommend that daily loads (dark days, over night, etc.) discharge around 1/4 or 25% of the banks capacity. You do this for 2 days, and you get to 50% State of Charge (used 150 AH of the 300 AH battery bank). Yes, you can discharge down to 20% state of charge (80% discharged)--But the battery life (number of cycles, aging, etc.) will usually suffer with Lead Acid chemistry batteries.

So, now to recharge--Forgetting that "fast" charge rates are less efficient than "slow" charge rates, a good rule of thumb to estimate charging time is:

From 20% to 80% state of charge, anything from 5% to 20% or so rate of charge is fine. If you have a 10% rate of charge (300 AH battery bank charging at 30 AH) will

• 300 AH * (100% - 50%) = 150 AH consumed

For the 50% to 80% state of charge "recharging":

• 300 AH * 0.30 (or 30%) charging = 90 AH
• 90 AH / 30 Amps "bulk charging" = 3 Hours

Then for the 80% to 100% state of charge, that is the "absorb phase"... The battery charger is holding a "fixed" charging voltage of ~14.7 volts (or whatever you have programed). And that will take from ~2 to ~6 hours to complete (2 hours if the battery was 80% SOC, closer to 4-6 Hours if battery was 50% SOC or lower level of charge).

The total charging time will be, approximately:

• 3 hours + ~4 hours = ~7 hours (plus or minus) to reach 100% State of Charge

The battery will be full when the specific gravity no longer rises (using a hydrometer), or when you see the charging current that has been falling from ~30 amps to ~3 amp (or even 0.3 amps for newer flooded cell/AGM/GEL type batteries) and the charging current stops falling (the "tail" of the charging current will be around 1% to 0.1% of the Battery Bank AH capacity)... That is 100% state of charge for the battery (if the battery is stable at 2% or more current, you are either charging at too high of current or the battery is near failing and should be replaced).

There are lots of other pearls of wisdom (like don't try for 100% SOC every day... >90% SOC once or twice a week is fine. Don't let lead acid batteries "sit" at below ~75% State of Charge or they will quickly begin to sulfate/die. And there are other charging scenarios---Such as run the batteries 50-80% state of charge daily, and recharge >90% SOC once a week, or once vendor says every 4 weeks, or so).

-Bill

PNjunction

I'm going to take a second look at MK/Deka Gel, even though I am an agm user and am well aware of the usual gel limitations especially for solar.

But like all things that improve, it seems that the common C/20 rate does not seem applicable to MK/Deka Gel.  What I see is similar to a conventional lead-calcium agm (not pure lead type) of about .3C max charge rate.

Absorb HAS to be temp compensated between 13.8 and 14.1 absorb.  I can do that.  I'd probably set for 14.0v personally.

And unlike cheap ups-style agm's that have anywhere from 8-14 mOhm of internal resistance, these seem to have about 4.5 mOhm.  Enersys/Odyssey and Optima pure-lead have about 2-3 mOhm IR, so they are not THAT bad and good enough for solar charging.

I need to do more research since *these* gel's don't seem to need to be handled any differently than most conventional agm's, other than staying within a smaller absorb charge window.  If they truly had more cycle life, then I'm even more interested.

So perhaps as long as one is just a bit more precise (ie, taking reliable voltage measurements *at the terminals*, temp comp, and not hitting them with more than 0.3C, then perhaps these have broken the rules established by earlier, junkier gel's.  But like there are junk agm's out there with high IR, other gel's may have not moved beyond the 1970's either.

With a narrow window of CV absorb, I can see where the latitude for problems is lesser than an agm, say with a large series / parallel bank that is severely unbalanced.

I'm going to to do more research on it, but I have to say that if an MK/Deka Gel passed my way, I'd give it a shot since I have the ability to maintain it.

jcheil

I use the 220/225w Topoint Panels, I have 39 of them. Never had any issues. They are however out of business (or in bankruptcy I think). But that doesn't matter IMO. You can't expect anyone to be in business 25 years from now anyways. Look at Evergreen and BP Solar. Never thought they would be out of business. And from what I have seen, unless you physically damage the panel, it's gonna pretty much last forever to some degree.

They always produce near their rated output (based on conditions) and in the cold months of Florida (40-50 degrees) they even put out more than rated. The reason you are seeing a lot of them for good prices is that they made something like 30MW of panels for some proposed installation in the NorthEast and then the project got cancelled. So they have been dumping them at great prices. Something like 1/2 of the panels were already in the US and shipped to the east cost. Those are getting harder to find now. The other 1/2 is on the west coast. There are plenty of those available. They started out as 220w panels, but the last batches were 225w panels.

I have a local supplier here in Florida that sells the 225w panels for around $185 each. But he said east coast availability was getting scarce and shipping from the west coast was prohibitively expensive.

But all in all, great panels IMO.