Recommendation for New Batteries?

crewzer · September 2005

It’s time for me to replace my original experimental bank of six various Group 27 12 V 115 Ah flooded-cell deep-cycle batteries. After hundreds of cycles, wide temperature extremes (<20 F to >100 F), a few very deep discharges, age mismatches (2 are >3 yrs. old, 2 > 2 yrs. And 2 > 1 yr), different manufacturers (2 are Johnson, 4 are Exide), various degrees of mechanical abuse (the original two survived >10K miles on the tongue of my camper), countless experiments with various chargers (Xantrex TC 10, TC 20+, Morningstar PS-30M, Outback MX-60), and other variations of cruel and inhuman punishment, their capacity has faded. In fact, the oldest two are essentially useless and I’ve disconnected them from the other four. However, for a total investment of $360, I can’t complain.

I’d like opt out of the nastier aspects of battery maintenance (checking electrolyte levels and SG, adding water, equalization charges, risks of sulphuric acid, etc.), so I’ve pretty much decided to go with AGM batteries for the next phase of experiments. I’m looking to build a 12 V bank of between 500 Ah and 600 Ah. Options include:

Concorde Sun Xtender PVX-1040 {12 V, 104 Ah (24 hr rate)} – Group 27, six each
Concorde Sun Xtender PVX-2580 {12 V, 258 Ah (24 hr rate)} – Group 8D, two each
Deka / East Penn Sea Mate 8A27M {12 V, 92 Ah (20 hr rate)} – Group 27, six each
Deka / East Penn Sea Mate 8A4DM {12 V, 198 Ah (20 hr rate)} – Group 4D, three each
Deka / East Penn Sea Mate 8A8DM {12 V, 245 Ah (20 hr rate)} – Group 8D, two each

I understand that AGM’s are sensitive to correct charge- and float voltages. I have the remote BTS to provide for temperature compensation, and I can program the correct baseline ABSORB and FLOAT voltages into my MX-60.

I’d be interested in anyone’s experience, comments, suggestions and/or recommendations about these batteries or similar models (i.e., Concorde Lifeline). Any comments regarding pro’s and con’s of six batteries in parallel (Group 27’s) vs. just two (8D’s) or three (4D’s) in parallel are also welcome.

Thanks, all!
Jim / crewzer

niel · September 2005

Re: Recommendation for New Batteries?

hi jim,
guess it's time to take that big leap. i am familiar with concorde and not the other. i would suppose you have visited both websites and made comparrisons that way. i am not sure of cost differences between the 2 either, but i am quite sure that you will be happy with an agm type battery system. the concorde requires 3.75mv/degree c compensation which my sb50 does not accomodate as they allow for 2mv and 5mv. you will also find that the voltage on an agm battery is slightly higher than the standard lead acid battery when at rest. you also will not need the big eq voltages anymore and charge voltage for the concordes are actually lower than standard lead acids. 14.1-14.4v.
generally it is better to have fewer large capacity batteries than many smaller paralleled so i'd go with the 8d types. this is also slightly cheaper to do this way. i never regretted going agm excepting i hessitated due to the initial cost of it. as you know i had batteries from walmart like the ones you had. i did better with the agms and i'm glad i did it.

Frank · September 2005

Re: Recommendation for New Batteries?

I have Concorde 6V AGM's and like them a lot. Actually (depending on your loads) you'll typically get slightly better A-Hrs out of two 6-volts than one 12-volt (due to the Peukert effect)(sp?). If your loads aren't too large I'd agree with niel's recommendation of 12 volt batteries (simpler wiring I guess). My bank consists of 3 string of 4 batteries each (660 A-Hr @ 24 VDC). They're expensive but maintenance free.

rplarry · September 2005

Re: Recommendation for New Batteries?

I have used both agm and gel and have had good experience with both, no real difference. You won't go wrong either way.
Larry

crewzer · October 2005

Re: Recommendation for New Batteries?

Decisions, decisons...

Thanks all,
Jim / crewzer

Brock · October 2005

Re: Recommendation for New Batteries?

I am getting to this same point. Probably next year, so I want to know what you get, from where and how you like it. I had been leaning towards L16's, but now I am re-thinking that...

For me it’s hard to justify double or almost triple times the cost for how much longer life? I understand there is less or no maintenance and likewise less mess and danger. Am I missing anything else? My current bank of Trojan T 125’s are almost 7 years old and after load testing them they are about 75% of rated, but likely on their way out. And I wasn’t nice to them for the first couple of years, until I found this board

System2 · October 2005

Re: Recommendation for New Batteries?

Hey Brock, re the L-16's. I got 6 a year ago and for me, they have worked great - so far.
Have 660 watts total GE PV's and my own PWM regulator. Two stage, + manual eq. Also have a Hornet, but it contributes very little, practically nothing from June to October.
The liquid level hasn't yet droped enough to bother adding water, it's still hanging around the level of the bottom of the fill tubes. They have been running my little Sanyo 12 volt fridge, 2 radios, CF lights, 3 of which stay in all night, so my 89 1/2 year old mother can see to get up around at night and this computer, as well as the Sears auto washer, a load a day and sometimes I make "solar" bread, using the iverter to power the breadmaking machine. So, I think they have had a good workout. However, during the 6 months of winter, their use will be reduced, we just don't get that much sun in winter. I've been pushing the sustem, using a lot more power than I need, just to learn it's limits. I've been quite impressed, I must say. But then again, we had lots of sun this summer too.

System2 · October 2005

Re: Recommendation for New Batteries?

Wayne, Crewzer,

Sorry for this misdirection, Wayne - how do the Hornets do from November to April?

Back to the subject.. I was talking to some folks recently and they said the Trojans were the better choice and that they seem to last quite a bit longer than rated. Provisions, of course

Jerry O.

crewzer · October 2005

Re: Recommendation for New Batteries?

Decisions, decisions...

Thanks, Gents.
Jim / crewzer

System2 · October 2005

Re: Recommendation for New Batteries?

GarrettCoMD wrote:

Wayne - how do the Hornets do from November to April?
Jerry O.

To be honest, I don't yet know. I have it installed at the cottage on the lake, and we are only there 5 month of the year. I take it down for the winter and soak it with Rust Check to preserve it from corosion.
However, our Municipal Government has had a study done and Oct to about June, the wind is sufficient for wind powe in our area.
Another thing, across the lake, a friend (yes, I do have one) also has a hornet, situated in a much better location than mine and it does much better.
One other thing, both are used on 12 volt systems, his is a 12 volt unit, but I was told to go with a 24 volt unit, since it would start charging at a lower wind speed. Well, it's true, it does start charging at a somewhat lower wind speed, and puts out an amp or two, but the drawback is that when the wind speed is higher, the blades are so overloaded by the mis-match, that they operate in semi stalled mode, never coming up to anywhere near the revs of the 12 volt unit across the lake and the output stays very low. I think the most I've ever seen it put out as about 5 amps.
5 amps X 12 volts =60 watts. A far cry from the so called 800 watts it was toted as being rated for.
In high wind, I can sometimes hear a bit of a whisper from mine, while the 12 volt unit pumps out power roaring like an angry banshee, to the point where I back off to a "safe" distance. Seriously it scares me. In that kind of wind, I expect a blade to break off, or contact the tower any second, while my 24 volt unit gently and quietly trickles out a couple of amps at best.
Since the lightening damage this summer, I removed the blown rectifer from the unit and ram a 3'rd wire doen the pole, giving 3 phase ac, which I rectify just before the regulator. What I intend to try (if I ever get time) is use 3 autotransformers, to step down from 24 volts to 12 volts and see what happens. I expect to see the miss-match vanish , the speed come up and start generating some power in stronger winds. I may well have to learn to sleep with the howl of a banchee, but know my neighbours won't like that at all.
Sorry to be so long winded, but this is about wind power, isn't it. LOL

crewzer · October 2005

Re: Recommendation for New Batteries?

I visited the Solar Decathlon on the Mall in Washington, D.C. today. The power sheds of four of the eighteen entrants were readily accessible, and a couple were staffed by very knowledgeable students. Here’s a run down of their battery configurations:

Wash State: Concorde Sun Xtender AGMs, 2 V size ??, 24 V bank
Cal Poly: Trojan AGMs, 12 V size 8D, 48 V bank
Univ of PR: Deka Gels, 12 V size 8D, 48 V bank
(#4): Deka AGMs, 12 V size 8D, 48 V bank

All VRLA, and lots of size 8Ds… hmmm…

System2 · October 2005

Re: Recommendation for New Batteries?

GarrettCoMD wrote:

Wayne - how do the Hornets do from November to April?
Jerry O.

An update on the Hornet.
Well!! Today we had some of the highest wind since last Winter. gusts to almost 100 km/hr. And that thing ROARED at times and I saw it putting out almost 30 amps during those gusts.
If it had been matched to a proper 24 volt load, instead of the 12 volt load, I would expect the output to be well over 60 amps, perhaps 70 or 80? I don't know.
Remember it's a 24 volt unit loaded down to 12 volts, causing a severe mis-match, resulting in the blades running in semi stalled condition, which is far from efficient..

crewzer · October 2005

Re: Recommendation for New Batteries?

I have often wondered why use twice as many 6 volt batteries rather than 12 volt btteries. It takes more than twice the capitol investment what with twice as many batteries, additional cables connecting the batteries, twice the space for batteries.

Battery voltage is only 1/2 of the equation, so to speak. You also need to consider the batteries capacity in Amp*hours, or Ah.

For example, a single 6 V golf cart battery might be rated at 6 V and 225 Ah. Two batteries in series would be good for 12 V and 225 Ah. A single Group 29 battery might be rated for 12 V and 120 Ah. Two of these batteries wired in parallel would be good for 12 V and 240 Ah. The two different pairs would perform similarly.

Does this help?

Regards,
Jim / crewzer

System2 · October 2005

Re: Recommendation for New Batteries?

So why have twice as many batteries (6v) and get a little less amp hours than 12v?
You would need more cables to connect the batteries and double the storage space.

crewzer · October 2005

Re: Recommendation for New Batteries?

6 V battery example: 2 batteries at 225 Ah in series = 12 V at 225 Ah. Assuming 50% DoD, that's ~112 usable Ah.
12 V battery example: 2 batteries at 120 Ah in parallel = 12 V at 240 Ah. Assuming 50% DoD, that's ~ 120 usable Ah.

Both examples use two batteries and offer similar specs. How does the the 6 V battery example translate into "twice as many batteries"?

??
Jim / crewzer

Brock · October 2005

Re: Recommendation for New Batteries?

Along those same lines, if you want say a 225 amp bank at 24v. That would take 4 6v batteries giving you a total of 12 cells to check and water. Now if you go with even a 112 amp 12v battery, that will also take 4 batteries, but now you have to check and water 24 cells since each cell is 1/2 the size. Both banks would be close in size and weight.

Some really large batteries are 1000 amps at 2v and you just keep adding them in series to get the voltage you want. The other advantage is if a cell goes bad it is one cell and not 6 as would be the case with a 12v battery.

crewzer · October 2005

Re: Recommendation for New Batteries?

So... Deka / East Penn AGM's are available locally (well, sort of locally). Big 4D's (12 V, 198 Ah) are $220, and bigger 8D's (12 V, 245 Ah) are $260. All fresh with same mfr dates. Not bad...

8) But, these particular versions are equipped with automotive-style battery posts...

hmmm..... :?

System2 · October 2005

Re: Recommendation for New Batteries?

crewzer wrote:

6 V battery example: 2 batteries at 225 Ah in series = 12 V at 225 Ah. Assuming 50% DoD, that's ~112 usable Ah.
12 V battery example: 2 batteries at 120 Ah in parallel = 12 V at 240 Ah. Assuming 50% DoD, that's ~ 120 usable Ah.

Both examples use two batteries and offer similar specs. How does the the 6 V battery example translate into "twice as many batteries"?

??
Jim / crewzer

crewzer,

Your example clears it up for me. Thank you. You need 2 six volt batteries to make 12 volts at 112 Ah but, you only need 1 twelve volt to get 120 Ah. This seems to use twice as many batteries and more cables.
You will have to excuse me as I am a thick headed German/Dutch kid (62 y/o) trying to figure this out before I hook up the pieces I have already.
I live in Wrightwood, CA. and we have power outages quite often due to drunks knocking down power poles. I want to have backup power just in case.

Thanks for your patients ( even though I'm not a doctor, I need more patients.)

Jerry (the Naughty Pines) Engelen

niel · October 2005

Re: Recommendation for New Batteries?

in general there is nothing wrong with using 6v or even 2v batteries to make your bank up with. you do have to interconnect them(pain) and as for any battery if one part goes bad, it all goes bad technically because you don't want to have batteries of differing ages. in seeing how they usually charge more for the batteries broken down into smaller voltages to make up the 12v counterparts with similar current rating i feel it's easier, better, and more cost effective going with the largest batteries available that won't need as much interconnections.

System2 · October 2005

Re: Recommendation for New Batteries?

niel wrote:

i feel it's easier, better, and more cost effective going with the largest batteries available that won't need as much interconnections.

My feelings exactly, thank you.

Jerry

crewzer · October 2005

Re: Recommendation for New Batteries?

Jerry,

No problem! my dad's family emigrated from Holland/Germany in the late 18th century, and we're still producing thick-headed offspring! :-o Wrightwood, eh? Gorgeous area, but a bit shakey at times!

Take care,
Jim / crewzer

System2 · October 2005

Re: Recommendation for New Batteries?

I'm only two blocks from the San Andreas Fault here in Wrightwood. :-o

crewzer · November 2005

Re: Recommendation for New Batteries?

I purchased and installed four Deka / East Penn size 4D AGM batteries last Saturday. They all have a "K5" date stamp, indicating they were manufactured in October, 2005. 8-) Each battery is rated at 12 V and 198 AH (20 hour rate). Normalizing for four of these batteries and my typical loads, the 12 V bank's 48 hour rate spec is 847 Ah based on a 17.63 A load. For simplicity, I'll refer to the new bank as an 800 Ah.

I decided on these batteries for the following reasons:

AGM. These batteries promise to be low maintenance and a low acid-spill risk. I’ll still have to check electrical connections, BTS adhesion and for venting, but good-bye watering and equalizing. The combination of a lower charging voltage and the elimination of equalizing routines should slightly improve charging efficiency.

Size 4D. The four batteries just fit into my battery box. Surrettes and other L-16’s are too tall. I also considered eight Deka GC2 AGMs (same size as T-105’s), which also would fit into the battery box, but their total rated capacity (748 Ah) is ~ 4.5% less than the 4D combination.

Cost. The base price for the four batteries was $880, or $1.11 / Ah -- a 17% premium over the Surrette 460's, but not bad for AGM's. Additional direct costs were 5% state sales ($44), battery post adapter hardware ($33) and $20 for gas to pick them up from the warehouse. All in all, not bad for a nice set of AGM batteries. The base price for the eight GC2’s would have been $928, or $1.24 / Ah – almost 12% more than the 4D’s. Shipping costs for the Surrette's wouldn't have been trivial.

Flexibility. The four 4D’s can be hooked up in parallel for 12 V, in series / parallel for 24 V, or series for 48 V. My present system in 12 V, but the future system will be either 24 V or 48 V, so this set might be a good “starter battery set” for a GVFX-based system.

Several of you on this site and over at Outback invested a fair amount of time and energy in developing your analyses and suggestions, and I deeply appreciate your efforts. While some may not agree with my decision, all of you contributed to the process, and I believe I did ultimately benefit from your experiences and recommendations.

Thanks, all!
Jim / crewzer

Frank · November 2005

Re: Recommendation for New Batteries?

FWIW, the other reason to consider multiple 6V or even 2V cells in lieu of 12 volt batteries is Peukert Factor. A-Hr capacity is somewhat a function of rate-of-discharge i.e. a 220 amp-hour battery is only 220 at the 20 hr rate or 11 amps. If you discharge at 22 amps the battery may only be good for 200 amp-hours i.e. something less. Multiple batteries are typically taxed lower (ex. two 6 volt versus one 12 volt) so aren't effected as much.

I think this is the theory (at least the way I understand it). If your loads are smaller I don't think it's that big a deal. We've got 12 6-volt Concorde AGM's in 3 strings of 4 each (24 VDC) and it seems a good arrangement for us. I'm hoping to get 7-8 years out of these but I would consider 8D's as a replacement...

System2 · November 2005

Re: Recommendation for New Batteries?

Crewzer,
Did you make any changes to the default settings on your mx60 for charge volts? float volts?
I have a BTS on AGM batteries and have the default settings for AGM's. I am not real clear on how to change settings or if I need to. Any help please.
TP

crewzer · November 2005

Re: Recommendation for New Batteries?

I set my MX-60 as follows for my new 12 V 800 Ah AGM battery bank (Nov. 8, '05 update... I'm still fine tuning the settings):

Absorb: 14.5 V reference to 77 Degrees F. Measurement at the batteries is ~14.30 V
Float: 13.4 V reference 77 F. Measurement at the batteries is ~13.35 V
Voltage offset: 0 V
Absorb Timer: Min 30 mins, Max 3 hours
Absorb End Amps: 12 A (~1.5% of 800 Ah capacity).
Temp Comp: Limit; Lo = 14 V, Hi = 15 V
Equalization: Auto EQ disabled

HTH,
Jim / crewzer

System2 · November 2005

Re: Recommendation for New Batteries?

Frank wrote:

FWIW, the other reason to consider multiple 6V or even 2V cells in lieu of 12 volt batteries is Peukert Factor. A-Hr capacity is somewhat a function of rate-of-discharge i.e. a 220 amp-hour battery is only 220 at the 20 hr rate or 11 amps. If you discharge at 22 amps the battery may only be good for 200 amp-hours i.e. something less. Multiple batteries are typically taxed lower (ex. two 6 volt versus one 12 volt) so aren't effected as much.

I think this is the theory (at least the way I understand it). If your loads are smaller I don't think it's that big a deal. We've got 12 6-volt Concorde AGM's in 3 strings of 4 each (24 VDC) and it seems a good arrangement for us. I'm hoping to get 7-8 years out of these but I would consider 8D's as a replacement...

I don't see how this plays in. If you have fewer cells, like in a 6x2V system, you draw much more power from each cell than if you have an equal size bank with parallell 12V batteries. So if the cells are 6x as large, you draw 6x as much power from each. Peukert should be identical ?

Brock · November 2005

Re: Recommendation for New Batteries?

Looking at Trojan, if you have a 6v battery and a 12v battery of the same physical size, the 12v battery will have a lower AH per cell and a lower overall wattage. This is because of the extra material and space used to have twice as many smaller cells and while the walls between the cells don't take up a lot of room it does add up.

So typically for the same physical size you will get more overall wattage out of the same size battery if the voltage is lower or it has fewer cells in it.

If you aren't worried about space or weight, then this isn't an issue.

Typically 6 volt batteries are made with thicker larger plates, which handle deep cycling better, but are not as good at CCA (cold cranking amps) or very heavy short loads. Most "marine" batteries have thinner plates with a better CCA, but give up overall ah for the CCA. They fall somewhere between and automotive battery and a true deep cycle battery.

crewzer · November 2005

Re: Recommendation for New Batteries?

Peukert Capacity, Peukert Equation, Peukert Exponent and Peukert Factor are not common terms, but we commonly see them in action when dealing with batteries.

Let's consider a typical Group 27 12 V battery as an example. Key typical specs are 20 hour capacity = 105 Ah and RC = 160. The 20 hour spec says the battery will deliver 110 Ah / 20 hours = 5.25 A for 20 hours at 77 F (25 C) until the battery's voltage under load drops to 10.5 V. RC = 160 means that the battery will sustain a 25 A load for 160 minutes at 77 F (25 C) until the battery's voltage under load drops to 10.5 V. The math now suggests the battery's capacity would be (25 A x 160 min) / (60 min/hr) = 66.67 Ah.

So, which is it? 105 Ah or 66.67 Ah? Peukert's Law, which basically states that a battery's capacity is temporarily decreased as its load is increased, explains this behavior. I posted a something of a tutorial on this subject a while back, and I see if I can find it to post again.

An important factor in determining and/or comparing battery capacity is to normalize loads for various battery configurations. For example, a single 12 V, 110 Ah battery should be able to deliver 5.5 A for 20 hours (5.5 A x 20 hrs = 110 Ah). Two of these batteries in parallel should be able to deliver 11 A for 20 hours (11 A x 20 hrs = 220 Ah). However, assuming a Peukert Exponent of ~1.27, the battery pair should be able to supply the original 5.5 A load for ~48 hours -- an effective capacity of 265 Ah.

HTH,
Jim / crewzer

System2 · December 2005

Re: Recommendation for New Batteries?

Jim/crewzer,
Back in Nov. you made the following post,

I set my MX-60 as follows for my new 12 V 800 Ah AGM battery bank (Nov. 8, '05 update... I'm still fine tuning the settings):

Absorb: 14.5 V reference to 77 Degrees F. Measurement at the batteries is ~14.30 V
Float: 13.4 V reference 77 F. Measurement at the batteries is ~13.35 V
Voltage offset: 0 V
Absorb Timer: Min 30 mins, Max 3 hours
Absorb End Amps: 12 A (~1.5% of 800 Ah capacity).
Temp Comp: Limit; Lo = 14 V, Hi = 15 V
Equalization: Auto EQ disabled

HTH,
Jim / crewzer

Have you done any more fine tuning? Are things looking about right?
I'm still a little puzzled with temperature compensated values.
I have had to use my charger and the temp. compensated numbers seen lower than the mx60 numbers. It's hard to tell because lack of sun so not getting the real picture.
Tp

crewzer · December 2005

Re: Recommendation for New Batteries?

tp,

My current settings are as follows:

Absorb: 14.3 V reference to 77 Degrees F. Measurement at the batteries is ~14.25 V
{I reduced voltage drop in the battery cables by increasing cable size and changing cabling configuration to eliminate a redundant circuit breaker. The batteries are fairly cold these days (52 F), and the MX-60 boosted ABSORBING voltage to an indicated 14.7 V today.}
Float: 13.4 V reference 77 F. Measurement at the batteries is ~13.35 V -- No change.
Voltage offset: 0 V -- No change
Absorb Timer: Min 30 mins, Max 2 hours
Absorb End Amps: 8 A (~1% of 800 Ah capacity).
Temp Comp: Limit; Lo = 14 V, Hi = 15 V
Equalization: Auto EQ disabled

Battery performance is very good at the moment, so I'm pretty happy with these settings. Time will tell if I've got 'em right...

I'm still a little puzzled with temperature compensated values. I have had to use my charger and the temp. compensated numbers seen lower than the mx60 numbers. It's hard to tell because lack of sun so not getting the real picture.

Tell us more and we'll see what we can do to help.

HTH,
Jim / crewzer

Recommendation for New Batteries?

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