Battery of Choice, Opinions vary!

System

Hey guys, i had originally planned on using a trojan t-105 for my battery banks when i first dreamed up this idea some time ago, after checking out some other forums and other places i was wondering if anyone had any opinons on batteries that might be available now that werent then.

Im planning on running a 48vdc system if that means much.

It would be interesting if anyone does the number crunching to know what other batteries offer in the range of power provided per cost of the battery perhaps there is a chart somewhere i missed, link it if you know of one

niel

Re: Battery of Choice, Opinions vary!

there are 3 main types being used in solar applications and they are:
1> standard lead acid
2> gel
3> agm
the 1st one is like the trojans you were considering. the 2nd and 3rd are sealed. the gels aren't as capable as the standards as they must not be overcharged or discharged heavily because of them being sealed. now the agms or absorbed glass mat have a kind of a mix of the 2 previous battery type features. they still don't tolerate an overcharge, but charge and discharge capacities are higher than gels. a big plus has been the efficiency in charging this type of battery as it generally receives a charge with about a 90% efficiency and other types about 80% speaking in general. what this means is it takes less energy to charge them than another battery type and this is an important feature for those with high priced pv system where each watt of produced power is at a premium.
the drawback to agms are a higher initial cost and smaller waranty period for the agms. do note that agms can last everybit as long as many of the standard lead acids, but i feel they are so unforgiving due to overcharge conditions that manufacturers are reluctant to give longer guarantees for them. i've had mine about 4-5 years now if i remember right.

n3qik

Re: Battery of Choice, Opinions vary!

I would go 1> standard lead acid or 3> agm. I have seen very few Gels go past 5 years in age. I have gone with Optima yellow top AGM for my system. I don't water plants so you can bet I will not water batteries!!

If you are going off-grid with large batteries, the Trojan's are the way to go. If you are going a small hybrid system like mine, then AGM's would be better.

crewzer

Re: Battery of Choice, Opinions vary!

There are pro's and cons to each battery type. Tell us more about your plans (array size, battery bank capacity, location, grid interactive or off-grid, etc).

More later,
Jim / crewzer

Mangas

Re: Battery of Choice, Opinions vary!

After a lot of research during the planning stages of my off grid system, I decided on Standard Trojans. During this design process, I called the factory and they walked me through the trade offs.

They came highly recommended, heavy duty and trouble free.

As far as wet cel, I don't mind watering them only twice a year (or less). Rightly or wrongly, I feel I'm in control of the system's primary component.

Jim, Niel and the other pros will give you good navigation.

System2

Re: Battery of Choice, Opinions vary!

well i didnt think that much consideration into gel cells were even being placed now a days, its mostly been AGM's or lead acid. I personally was looking for something that was a bit less maintenance then monthly, maybe wouldnt mind 3-4 month periods of maintenance.

Regardless AGM's are nice too but often costly and not worth the amperage they provide?

Mangas

Re: Battery of Choice, Opinions vary!

The water miser caps we installed very substantially reduced the need to water our batteries. I think they're well worth the investment.

Like I said, we do it only twice a year with plenty cel fluid reserve.

mike95490

Re: Battery of Choice, Opinions vary!

Mangas wrote: »

The water miser caps we installed very substantially reduced the need to water our batteries.

Do those still need to be removed before equalization ?
(too much O & H overheats the catalyst)

Mangas

Re: Battery of Choice, Opinions vary!

My understanding is with the Hydrocaps they need to be removed (I don't have them). Check with Jim or Niel.

A couple of time a year, I unscrew the yellow bayonet Watermiser caps when topping up the batteries. I use an automotive type distilled water filler bottle which automatically stops the flow when the cel is full. It works great, easy with no mess. Otherwise the Watermisers remain on the batteries 24/7. Infrequent watering has been a pleasant surprise.

mike95490

Re: Battery of Choice, Opinions vary!

OK, what's the difference between
Watermiser caps
and
Hydrocaps.
One has a catalyst to recombine O & H. What's the other one do ?

Mangas

Re: Battery of Choice, Opinions vary!

The Watermisers reduce water evaporation somehow. Don't ask me how.

I think they help the batteries retain fluid by the way the caps are constructed. I have three per battery x 64 batteries. A lot of caps but they work.

If you run a search on them, you can get more info.

lamplight

Re: Battery of Choice, Opinions vary!

i also have t-105's, going on 4 yrs now (wow!) no probs, no watermisers but thy are sounding good. in summer i refill the batters every couple months in summer, not at all through winter as i dont get as many absorbs. brock here has agms and the description of how little (relatively) current it takes to charge them sold me. i will most definitely get them next time if budget allows. thats the thing with the t-105s: you get the most bang (amp hours) for the buck, but theres that labor (watering) tradeoff.

kc8adu

Re: Battery of Choice, Opinions vary!

favorites here are east penn/deka agm
also sold as mk here.
i have several 8d mk agm that are 9 years old and used heavily.
no signs of positive plate growth yet and still good runtime.
beware of ANY batteries from china.
i service wheelchairs/scooters and the china batts are junk.
failures in 2 months are common and runtime dropping like a rock in 2-4 also common.

System2

Re: Battery of Choice, Opinions vary!

so ultimately, lead acid (cheaper per amp, but you have to water them more.) Is it agreed then if all batteries came with the recomb caps that it would be the better way to go? Heres something to consider, the cost of the caps + battery divided by the amps would be the number to work from.

As a pose to AGM's which require very little maintenance, but are a bit more costly per Ah provided.

Aside from those 2 things noted would there be much more to consider when choosing lead-acid to AGM's?

What was it you were saying lamplight about the relative charge required to charge an AGM as a pose to lead-acid and how does that figure into a PV system? sorry but im hoping to make the best informed decision i can, you've all been just super patient and so informative, thank you kindly.

crewzer

Re: Battery of Choice, Opinions vary!

Other “flooded-cell vs. AGM” factors to consider are number of charge/discharge cycles (cost per cycle), and recharging efficiency. Cost per cycle can be hard to nail down due to so many variables.

VRLA (AGM and gel) batteries are generally more efficient than flooded-cell models. The energy efficiency (Wh out / Wh in) of VRLA’s is typically ~90%, vs. ~80% for flooded-cell models. The corresponding coulombic efficiency (Ah out / Ah in) is ~98% vs ~90%.

The efficiency issue is important because, everything else being equal, it means that a smaller (and therefore cheaper) PV array is required to recharge the batteries.

Here’s a link to an old but hopefully related discussion on another forum: http://www.outbackpower.com/forum/viewtopic.php?t=848

HTH,
Jim / crewzer

lamplight

Re: Battery of Choice, Opinions vary!

which is why i will likely go with agms once my t105's die (Even though they may not last as long as a t105, yet another issue to consider)- its encouraging to hear someone running agms for 9 yrs though. that would be like getting a 10% increase in total power available to me just by switching batteries. ..ive yet to invest in water misers which i might still do. so assuming i might get almost as much lifetime from agms the 2 variables left to consider: are the cost savings greater by saving on 10% on less pv needed, or would you save more with lower upfront battery cost. hard to answer especially since we dont know exactly how long the batteries will last.

crewzer wrote: »

VRLA (AGM and gel) batteries are generally more efficient than flooded-cell models. The energy efficiency (Wh out / Wh in) of VRLA’s is typically ~90%, vs. ~80% for flooded-cell models.
The efficiency issue is important because, everything else being equal, it means that a smaller (and therefore cheaper) PV array is required to recharge the batteries.

crewzer

Re: Battery of Choice, Opinions vary!

See this NAWS link for more info on Hydrocaps and Water Misers: http://store.solar-electric.com/hydrocaps.html

HTH,
Jim / crewzer

lamplight

Re: Battery of Choice, Opinions vary!

thanks crewzer, thats all i needed to by my water misers fially: about $80 for my 6 t105 batteries that should reduce my watering maintenance a bit - yet another factor to consider when considering flooded vs vrla.

PhilS

Re: Battery of Choice, Opinions vary!

lamplight wrote: »

thanks crewzer, thats all i needed to by my water misers fially: about $80 for my 6 t105 batteries that should reduce my watering maintenance a bit - yet another factor to consider when considering flooded vs vrla.

If you needed any more reason, realize that the Water Misers will be transferred to your next set of batteries at no expense. Mine are on their second set of batteries because they don't seem to 'wear out'.

Phil

System2

Re: Battery of Choice, Opinions vary!

so for anyone who likes to just read the short version, heres what i've learned on the recap.

AGM/Gel have higher initial cost but a gain in efficiency, which might require a smaller pv array to charge, however these reductions in pv array might be offset by the length the battery lasts (like if you have to replace several AGM's every few years.)

Flooded cell have maintenance which can be often and regularly and have a lower initial cost but likely a much longer life if used properly. The maintenance of topping off the batteries can be offset by using hydrocaps or water misers. Flooded cells in some cases also have a better Ah per $ ratio although again this is offset by possibly needing a larger array of pv's to keep them charged properly.

I've learned alot guys, feel free to recap on anything i missed or correct me where im wrong. Thanks to you all for being so informative.

niel

Re: Battery of Choice, Opinions vary!

there isn't any evidence that an agm battery's lifespan is necessarilly shorter than that of a standard lead acid battery when properly charged.