Benefits of Gel batteries

[Sunking]

Mike read this document carefully, it is important you understand it. Then ask follow up questions. Pay real close attention to voltages and settings. Your batteries should be voltage charged, not constant current charged. What that means to you is set Bulk, Adsorb, and Float to the same voltage and use temperature compensation as it will be very important in a hot climate.

[Gambia river lodge]

Hi all,
I only had chance to study these batteries spec for a few hours, on the face of it and with the restricted charge voltages they seem quite unsuited for solar, however as you study them more, you do start to think they are not so bad and maybe, JUST MAYBE most of us are so familiar with the flooded batteries, and how they peform, that these developments in batteries are dismissed before given an honest chance.
Just on the spec from what i have read (not always true, as i have found) just on the killer of flooded (Sulfation) they out perfom them many times over. I would suggest all you 'Die Hard' flooded guys, read ALL the info on the link SK posted.
OK that said, i need to look at my situation, reading the spec on my MPPT controller (PCM6048) which my manual refers to aa a SUNSTAR, it has a setting for Gel batteries, the two spec's seem to be linked, factory settings, Absortion max14.1v,spot on, for my Temp at my location using the afore mentioned link to Gasima, (could be reset to 13.8v for optimum)
Float charge 13.5v again, spot on, for my location. No charge available for equalisation when Gel batteries are selected, again spot on, so looking at the controller and the batteries, it all looks good, until, you factor in the real life scenario of TEMPERATURE, unless airconditioned (no chance for most OFF GRIDD) it is crucial to be monitored, (i do have A/C in Gambia as the Romans did, reasearch it and belive me it works, a small elec fan can be used but i still use CONVECTION), 'anyway' my controller (as do most mppt) they do have additional relays that can be used (along with a temp probe) to turn on appliances such as fans is a MUST.
Need some input here SK, if read this as i have, maybe your initial thoughts on 'current' has changed, two points raised in the link are, my batteries 8ggc2 show a charge for 3.5 hours of 80amps!! also at optimum volts of 13,8 NO LIMIT ON RECHARGE CURRENT.
Maybe this is what has always been overlooked with these batteries, it seems to me if you have the panels and the controllers you can, not only have the additional consumption of safe discharge, but the vast saving of battery life without Sulfaction killing your batteries.
OK reading my previous post, with 48 of these Gel batteries and looking at the charge currents what can i do with the 108 x 200w panels and charge controllers.
Thanks Mike.

[Gambia river lodge]

Hey Mike,
Just read your addition (i wish i could do that) if you are going to apologise for your mistake, at least be honest and say "i never read it properly", not a problem for me and most others i think !! You have to remeber that most people reading these post, just glance at them and never look back, so your addition has been overlooked by many, I am new to these forums, and yes i have my own issue's i have to deal with, however i do understand that many 'NEWBIES' like me, are looking for solutions.
Many thanks Mike.

[Sunking]

OK Gambia let's back up a second. First I will say Deka (East Penn) makes a quality product, but keep in mind you are reading the manufactures material, and they tend to sugar coat things. I also believe you are misinterpreting some of the information you are reading.

Gel Cells do have some distinct advantages:

• They will not spill acid even if turned on their side or the case ruptures. This is a great thing for small tight spaces like emergency egress lighting and UPS systems contained in a cabinet.
• The recombine their hydrogen and oxygen to make water. This makes it unnecessary to check or add water and thus less maintenance. Again something you want in emergency egress lighting, cameras, security systems, or anyplace where it is really inconvenient to do so.
• Because they are sealed, normally they do not give off hydrogen fumes. This allows then to be installed in really tight places with no or poor ventilation.
• The gel electrolyte stabilizes and isolates the battery plates and grids against shock and vibration. A good thing to have in something like a plane, train, automobile, or machinery with a lot of movement and vibration.

On the flip side they have some huge disadvantages:

• Their plates have to have calcium added to the lead, and the plates have to have to be thin a spongy in order for them to recombine hydrogen and oxygen to make water. That is great for a starting battery where you need to deliver high burst currents, but horrible for cycle life. Then multiple spongy plates erode quickly when cycled vs thick heavy plates of true FLA batteries. So this means shorter life span or number of cycles.
• They are extremely sensitive to over charging, and MUST be charged much more slowly with a constant voltage taper current charge. That is great in something like a UPS or emergency lighting system that use float chargers and rarely used. If you charge then too fast, they will vent and dry out the gel leaving cracks and voids which are permanent damage.
• You cannot check the specific gravity, equalize them, or check/add water.
• They are also very sensitive to heat and prone to thermal runaway. They do not play well in high temperature environments. So extreme care and temperature compensation must be used.

So the bottom line is if you are using a RE system and need the benefits of a gel battery, use an AGM as they have the same advantages but none of the disadvantages of gel, plus AGM is less expensive.

[Sunking]

OK reading my previous post, with 48 of these Gel batteries and looking at the charge currents what can i do with the 108 x 200w panels and charge controllers.

I got to think about that one a while.

[Gambia river lodge]

Thanks for the replies,
I understand exactly what you are saying SK, the whole design of a system using Gel becomes allot more technical and has very narrow margins for error, in my case i have no choice unfortunatly, and any saving i may have gained through less maintenace has probably double the time in monitoring.
I am rather confused with the charge rates of Gel batteries, i understand the critical levels of voltage rates and temperatures which can certainly increase with high capacity charging but i am reading rates as high as C2 can be acceptable, that seems a bit scary!! but what are the safe limits with all other components being available?
Thanks Mike.

[Sunking]

but i am reading rates as high as C2 can be acceptable.

Where are you reading that? Only batteries I know of that can be charged at a C2 rate are some NiCd, NiMh, and some Lithium's. There is no lead acid chemistry I know of that could withstand a 30 minute charge rate.

[Gambia river lodge]

Ok you love to educate me, i thought that the 'C' rate was the Ahr/charge current, obviously not!! The site i was reading is from Mastervolt gel batteries, who state, A Gel battery can be charged at 50% of the Ahr rate; 12v 200ahr gel battery can be charged at 100amps.
Thanks Mike.

[Sunking]

OK it is pretty simple C in the charge rate = Amp Hour Capacity of the battery. So lets say you have a 100 AH battery and you want to charge it at C2 means 100 x 2 = 200 amps in 30 minutes. I think you meant C/2 which means 50 amps in my example or the 2 hour rate. Gel Cells need to be charged at C/20 or less. So for that 100 AH battery example would be 5 amps or less.

Now keep in mind I an speaking generically across the board. If I were you I would call a Deka rep and ask them what is the maximum charge rate they recommend for your model of battery. It will be expressed as C/X, not CX

[Gambia river lodge]

Thanks SK,
my supplying dealer here in the UK no longer deals with Deka, i can call them direct would you have any idea of time difference there?
I have also been studying there spec sheets form the link you posted, for these batteries 8ggc2, they list them in thier charging guide which seems to completley disregard the C/20 charge rate.
From 100% discharge to 90% charge they list;
3.5 hrs @ 83a charge rate, 6hrs @ 42a charge rate and 13hrs @ 17a, plus additional time to get to 100%.
Knowing i have 6.5hrs of charge time and a battery bank of (idealy) 720ahr and accepting i would not go below 50% of capacity, that would give me a charge rate of min 55a C/13.
Is there a way to factor in the addition 10% to reach full capacity?
Many thanks Mike.

[Sunking]

i can call them direct would you have any idea of time difference there?

From England -5 hours this time of year.

I have also been studying there spec sheets form the link you posted, for these batteries 8ggc2, they list them in thier charging guide which seems to completley disregard the C/20 charge rate.

That is why I said call a Deka rep and get the scoop for your battery model number. You have an extreme amount of money tied in in those batteries, it is worth your time to get it right. Would hate to see you replacing them in 6 months.

FWIW net time get either AGM if maintenance free is important to you, but in that heat I would opt for a Rolls FLA 4000 or 5000 series. For 1/3rd the price you paid you could have had a solid 5 to 10 year battery.

[Gambia river lodge]

EPM_gel_charging2[1].pdf

Hi SK, i have the charging spec from Decka which has confused me even more, The Bulk Stage 1 states, 30a per 100ahr C20 !! Any idea's
Thanks Mike.
P.S Off to Gambia in 8hrs

[AfricanEnergy]

Lots of mis-information flying around here, it seems. We have been using Deka gel batteries in Africa for over 10 years. They have outlasted any other brand we've tried. Gel is a perfectly good technology and is the original sealed deep cycle technology. We would only use an AGM in a very rapid (1 - 2 hour) recharge. C/20 refers to a capacity rating, not the re-charge rate. With a temperature sensor, you should be able to charge up to 20% of the C/20 rate or higher. I suspect the problem is to do with sizing - can you tell us your array size, battery voltage and controller? Also, what are your depth of discharge settings and the charge settings on your controller? Are you completely standalone? And yes, it is hot and sticky in the Gambia, but you are doing good to get an average of 5 hours. Remember that all that humidity has an impact on insolation.

[AfricanEnergy]

Just saw yours saying "Hi SK, i have the charging spec from Decka which has confused me even more, The Bulk Stage 1 states, 30a per 100ahr C20 !!"

In other words, you can charge at up to 30% in bulk. If you had SK's 1000 ah battery, you could hit it with 300 amps bulk stage charging. The C/20 would refer to the 1000 ah rating of the battery. It would have a higher rating at c/100. But that is a discussion for another day....

[russ]

African Energy posting out of Atlanta, GA?