two batteries

[rasp]

if you wish to take a look at electric golf carts or other electric transportation they run batteries in parallel, some use two six volters in series and several pairs of these in parallel. caterpillar uses two 12 volters in parallel and then another pair in series to get 24 volts.

where i work the emergency diesel fire pump is wired wire a series parallel combo of 12 volt batteries, if it were a bad idea then the insurance company would not allow it.

must be a lot of uneducated folks out there.

A lot of these situations the batteries would be on a float charge the majority of the time, even the golf carts would go out for a round and then get plugged back in at the end of the day, their capacity would be greater than what could be expected to be used in a day. I don't think in any of these situations the batteries would get charged and then run close to flat and then charged again etc. And I bet the insurance company has a maximum life on the ones running the pump and they have to be replaced regardless at a set interval, certainly computer battery backup ones do.

Basically I think it comes down to maintenance, if the batteries are high capacity, sit on a float charge most of the time and are well looked after they should last a longtime regardless of how many are hooked together. If you have two batteries, drain flat, charge, drain flat, charge etc then one will drop off quicker than the other and have a detrimental effect on the other.

One thing I've always wondered about is what about batteries like the little 9V ones that are basically multiple batteries wired together (AAAA size inside I think) they come in rechargeable and last for ages, is this whole thing different with NICad and NiMH batteries etc?

Cheers
Steve

batteries for the starter on the diesel emergency pump get checked on a regular basis and are changed out when they do not meet requirements. this does not have to do with age but condition of the battery itself.
they do, get all changed when one goes bad as it normally signals the end of life is around the corner for the rest.

[brian_bp]

One thing I've always wondered about is what about batteries like the little 9V ones that are basically multiple batteries wired together (AAAA size inside I think) they come in rechargeable and last for ages, is this whole thing different with NICad and NiMH batteries etc?

Most of the discussion here seems to be about potential issues with batteries in parallel, but those multi-cell batteries (such as the common 9V) are a set of cells in series (6 cells for a nominal 9V, either AAAA in a "six-pack" or rectangular cells in a stack).

Every little device I've had with disposable or NiCd or NiMH batteries place them in series, except one flashlight. It's a Stanley MaxLife 369, and it has three AA in series in each leg, but it will operate with any number of legs filled with cells, so the legs must be in parallel (which makes sense since these little LED units are usually 3-cell). The extra 3 or 6 cells are just there to extend operating time. I haven't used it enough to know how effectively it uses the battery capacity.

There are lots of detail differences, but similar issues of balancing cells in a battery system exist in both lead-acid and other chemistries, and there are issues in both series and parallel configurations.

For an extreme example of stringing cells together, the Tesla Roadster (no, I don't have one of those) electric car uses 99 groups of cells connected in series, with each of these groups containing 69 cells in parallel. 99 in series is not surprising for a battery pack driving a car (hybrids now routinely have this sort of setup)... but 69 cells in parallel in each group? I guess parallel is manageable in a lithium ion system.

[evilme28]

Thanks for all the advice guys. I think since I am comming at this completely green I'll just start with one large battery and go from there. I plan on building another trailer next summer a bit larger and with more bells and whistles so I may wait to go with two till then. For now I'll just run the high watt stuff at campgrounds where I can plug in.

[Alphacarina]

if you wish to take a look at electric golf carts or other electric transportation they run batteries in parallel

must be a lot of uneducated folks out there.

Golf carts are typically 36 volts - They run six of the 6 volts 'golf cart batteries' all connected in series

Lead acid powered car conversions are usually 96 to 144 volt arrays, again with all the cells in series, not parallel. Lithium Ion powered cars are another animal all together - I assumed this was a discussion about paralleling lead acid batteries

Some diesel trucks do have two heavy duty 12 volt lead acid batteries in direct parallel - My Dad had an F-250 which came that way from the factory. After buying new batteries for it every 18 to 24 months, he had me convert it to a pair of 6 volt golf cart batteries connected in series. My brother still owns that truck now some 20 years later (it's a 1986) and the pairs of golf cart batteries always last 5 years or more

As I said, you can parallel lead acid batteries if you want to and you don't care how long they (don't) last - It's just not a recommended practice . . . . and anyone electrically educated will tell you so

Don

[Larwyn]

if you wish to take a look at electric golf carts or other electric transportation they run batteries in parallel

must be a lot of uneducated folks out there.

Golf carts are typically 36 volts - They run six of the 6 volts 'golf cart batteries' all connected in series

Lead acid powered car conversions are usually 96 to 144 volt arrays, again with all the cells in series, not parallel. Lithium Ion powered cars are another animal all together - I assumed this was a discussion about paralleling lead acid batteries

Some diesel trucks do have two heavy duty 12 volt lead acid batteries in direct parallel - My Dad had an F-250 which came that way from the factory. After buying new batteries for it every 18 to 24 months, he had me convert it to a pair of 6 volt golf cart batteries connected in series. My brother still owns that truck now some 20 years later (it's a 1986) and the pairs of golf cart batteries always last 5 years or more

As I said, you can parallel lead acid batteries if you want to and you don't care how long they (don't) last - It's just not a recommended practice . . . . and anyone electrically educated will tell you so

Don

Well, I'll be.............
Shore wish I had me one of them edumefications so I could be smarter than all them thar engikeners what builds them thar diesel pickem-up truks..... Looks like if'n I was smart enuf I could save me a whole bunch on batteries. No wait my cousins batteries must be dum too they is still a workin................
I really do apreciate them babies in cowboy hats tellin me how to do stuff rite tho..........

[madjack]

...amazingly, 99% of the BS that has to be censored on this site, starts right here in the electrical section...no matter what kinda of "hat" ya wear(or not), BE COOL...PLEASE...it does take two too fight...remember that as well......

In electrical applications, many things are done many different ways...the only thing that really matters is if it works for the intended application and is SAFE...and remember to just HAVE FUN........
madjack

[S. Heisley]

Putting things back on the electrical "curcuit":

After 4 years, I just had to replace my lawnmower batteries. (They didn't die because they wore out from use, they died because of an electrical short in the recharger.) That may sound like a joke; but, the reason I write about it is because the lawnmower uses two 12 volt batteries, wired together, one to the other. (Yes, they are on the charger most the time.)

The important point in this is that the mechanism came with a warning to never let the batteries run all the way down to "empty". I don't know why that would make a difference. Maybe someone on the forum can explain that one and/or if that information is needed in our off-grid camping situations?

Thanks!

[rasp]

Putting things back on the electrical "curcuit":

After 4 years, I just had to replace my lawnmower batteries. (They didn't die because they wore out from use, they died because of an electrical short in the recharger.) That may sound like a joke; but, the reason I write about it is because the lawnmower uses two 12 volt batteries, wired together, one to the other. (Yes, they are on the charger most the time.)

The charger may not be able to handle the load that a completely discharged battery would require. plus Cycle Life of a battery is a measure of how many charge and discharge cycles a battery can take before its lead-plate grids/plates are expected to collapse and short out. The greater the average depth-of-discharge, the shorter the cycle life.

The key to battery life no matter how you wire your batteries, is to use the proper battery for the job at hand, maintain fluid level in the cells, maintain the specific gravity of the electrolyte, follow the manufacturers recommendations on discharge/ recharge. Most battery manufacturers advocate not discharging their batteries more than 50% before re-charging them.

Batteries are typically built for specific purposes and they differ in construction accordingly. There are two applications that manufacturers build their batteries for: Starting and Deep Cycle.

* Starter Batteries are meant to get combustion engines going. They have many thin lead plates which allow them to discharge a lot of energy very quickly for a short amount of time. However, they do not tolerate being discharged deeply, as the thin lead plates needed for starter currents degrade quickly under deep discharge and re-charging cycles. Most starter batteries will only tolerate being completely discharged a few times before being irreversibly damaged.
* Deep Cycle batteries have thicker lead plates that make them tolerate deep discharges better. They cannot dispense charge as quickly as a starter battery but can also be used to start combustion engines. You would simply need a bigger deep-cycle battery than if you had used a dedicated starter type battery instead. The thicker the lead plates, the longer the life span, all things being equal. Battery weight is a simple indicator for the thickness of the lead plates used in a battery. The heavier a battery for a given group size, the thicker the plates, and the better the battery will tolerate deep discharges.
* "Marine" batteries are sold as dual-purpose batteries for starter and deep cycle applications. However, the thin plates required for starting purposes inherently compromise deep-cycle performance. Thus, such batteries should not be cycled deeply and should be avoided for deep-cycle applications unless space/weight constraints dictate otherwise.

[Dale M.]

When all the techno speak is said and done, bottom line is get two matched batteries, connect them in parallel, get quality charger and keep "system" charged a float voltage when not "in use" and you will probably be a "happy camper" with all the confusion behind you....

Dale

[Alphacarina]

When all the techno speak is said and done, bottom line is get two matched batteries, connect them in parallel, get quality charger and keep "system" charged a float voltage when not "in use" and you will probably be a "happy camper" with all the confusion behind you....

Agreed

So long as they can spend 99% of their lifetime on a trickle charger, you're in good shape. If you store your teardrop away from a power source and can't keep them on a charger, disconnect them so they're not in parallel while they sit . . . . or they won't last any longer than they do in dem dere pickem up trucks

Don

[rasp]

Batteries discharge on their own. The Self-Discharge rate can be 8-40% per month. This is why flooded lead-acid batteries should be in use often or left on a trickle-charger. If not, Sulfation occurs.

Sulfation refers to the process whereby a lead-acid battery loses its ability to hold a charge after it is kept in a discharged state too long.

[S. Heisley]

Wow! I've just had my brain "recharged" and I've been "enlightened"!

Seriously, fellow campers, thanks a bunch for all that information! You can bet I'll put it to good use.

[Alphacarina]

Batteries discharge on their own. The Self-Discharge rate can be 8-40% per month. This is why flooded lead-acid batteries should be in use often or left on a trickle-charger.

AGM batteries self discharge at closer to 2% per month. I use Optimas and they recommend that it's perfectly OK to leave them sitting for a year and still expect them to start whatever they are hooked to

Flooded Lead Acid batteries self discharge a little faster, but even 10% per month would be on the higher end of the scale - I hope you got a real good buy on those 40% ones

Leaving them on a charger can be beneficial . . . or not. If they are to be hooked to any charger 24/7 then it needs to be either computerized (capable of measuring the battery and regulating itself accordingly) or else he charger needs to be designed for the batgtery bank it will be attached to. Trickle charging rates for non-smart chargers should be on the order of one tenth of a percent of the battery capacity - That means a 100AH battery needs a 100ma charger and a 60AH would need a 60ma charger

Your typical 'el-cheapo' trickle chargers usually have an unregulated output of about one amp . . . . or ten times the safe amount for a 100AH battery and leaving one of those hooked up 24/7 will actually shorten the life of your battery as compared to just leaving it sit and then giving it a correct maintenance charge once every 6 months or so

I have more batteries laying around than most folks - 2 boats, (one with 4 golf cart batteries) a travel trailer, 3 motorcycles, a garden tractor, 3 cars and a very seldom used truck . . . . and I don't leave any of them hooked to chargers 24/7 because I want the longest life possible from my batteries . . . . and because 10 trickle chargers would probably cost me $10 a month to run. I do maintain my batteries by periodically charging them, but I don't leave any of them connected to chargers 24/7

Most of my batteries are fairly old - More than half of them are 5+ years old and one of the Optimas is 11 years old. The golf cart batteries in the boat are 6 years old

Leaving any battery sit discharged will indeed speed up it's sulphation . . . . but boiling the electrolyte with a 1 amp 'trickle charger' will kill it even faster

If you're someone who prefers to leave a charger connected 24/7, be sure you buy a charger specifically designed for this . . . . and not one of the $10 Harbor Freight models

Don

[wlooper89]

Lawryn,

I fully agree. The main question for camping without shore power is ampere hours rather than one-or-two batteries, although the method of connecting the two batteries is also very important. In my case the space where I wanted to put a battery is limited and I opted for one large one. It is a Fullriver FR31 and rated at 110 AH, deep cycle AGM. Weighing in at 78 lbs it is a bit difficult to handle. My solution was to install a block and tackle attach point in the ceiling of my garage. For stronger persons and stronger backs that would not be necessary.

In the case of a teardrop builder with space for two batteries, it might be more economical to use two, although I have not researched this. I do like the AGM deep cycle type for use in a compartment with other electrical gear because the AGM batteries are less likely to give off combustible gases. For my installation I still plan to vent the battery box that is within the electrical compartment to outside even though the battery is AGM.

Bill

[Alphacarina]

If you have the room . . . . and if you can tolerate the weight, the biggest bang for the buck in deep cycle batteries is a pair of 6 volt Golf Cart batteries wired in series to give you a single 12 volt battery bank

For about $130 to $140 you get a 200AH battery which will outlive most other conventional deep cycle batteries 2 to 1. They are very robustly built, designed for heavy duty service and the have extra room at the top so that you have less chance of exposing the plates as the water evaporates. It's not uncommon to get 700 deep cycles from them and with proper care they could last you 6 or 7 years

There are a dozen different brands but the best of the conventionally priced ones is the Trojan T-105. For comparison purposes, their 200AH is about double the 105AH you get from Group 27 sized deep cycles or the 75 to 80AH group 24 sized batteries and a pair of the golf cart batteries is infinitely more practical than a pair of the 24 or 27 sized 12 volt batteries in parallel . . . . and as I mentioned earlier, they will also outlast them by a factor of 2 to 1 or greater

You cannot beat the practicality of the AGM batteries (Optimas and the like) but to get you 200AH from 2 or 3 AGM's you're going to spend double or triple what you would for a pair of golf cart batteries. I use a single Optima but I also spent $129 for a 20 watt solar panel to back it up . . . . mostly because I can't deal with the weight of the golf cart batteries in my very small Little Guy

Don