Solar or Wind???

finding41 · Mar 6, 2014

Thanks Maine Sail. I was looking for that info too.
I've got a 6v battery question....
I have a chance to get used electric golf cart batterys. Used one year inside a factory carts. They get swapped out for new ones every year by the cart company that looks after the maintenance. The cart company sells these battery's cheap ($25/) to people in trailer parks for there electric carts. (My mom recently moved to a trailer in the woods... I'm told they get 3-4 years out of them.)
What should I look for in a used battery? How can I test it with my meter that doesn't have a load test function?
Am I crazy to think I can charge 4 6v battery's with a 100w solar panel and have them kept up for a week of cruising? I have shore power for charging for about 18 hours one day a week.

willsnow · Mar 7, 2014

i know that batteries in series need to be the exact same make/model/age/condition or one will draw from the other. maybe if they are the exact model and everything, you could do a load test and make sure they are in the same condition?

walt · Mar 8, 2014

here has been my experience with serial or parallel batteries. With parallel batteries, if you charge or put a load on the batteries, you don’t know which battery is either providing or taking the charge. If both batteries are close to the same, you likely get similar currents in each battery – but you really don’t know. If you keep the water level in both batteries always topped off, two batteries in parallel should work fine. But if the water in one battery starts to get a little low, you can have the water loss accelerated by the other battery and then you have a problem. Just watch the water and likely no problem.

With series batteries, the current in each battery will be identical. One battery can’t draw down the other. Either charging or drawing on the batteries has identical current flowing in each battery. However, if one of the two batteries is weak, the entire series is degraded by the weak link.

I’ve had both series (2 six volt) and parallel (2 12 volt) and prefer the 6 volts because its been my experience that the identical current in each battery ends up requiring less water maintenance. My experience is only with wet cell. My two 12 volt batteries always in parallel lasted about 2 or 3 years before they were just trash, my two 6 volt batteries in series is going on I think 4 now and show no signs of aging that I can tell.

Finding, I think your plan would work just fine. I don’t know if you plan to just make those four 6 volt batteries into one big bank or two separate batteries with an A/B switch. I like just one battery bank myself with a charge monitor so I always know exactly the state of that single battery. Four golf cart batteries plus the 100 watt panel would be a serious overkill for most people who don’t have a fridge but overkill also means you have lots of margin. Lots of margin means you can tolerate dumb things - and I always do something dumb sooner or later. You should do an “amp hour” budget, I know a lot of people on this forum can help with that.

This is an old discussion.. but my opinion is that some of you sure would benefit from a charge monitor. This is a single instrument that tells voltage, current but it also keeps track of current multiplied by time - which really is the bottom line on how much of the battery charge you have used. If you have a small system, a charge monitor generally lets you get by with less solar panel for example since you know exactly where you are at any time. Having a charge monitor has generally caused me to reduce the size of solar panel Im using as exactly knowing the battery state means you need less margin (now mostly just use a 10 watt panel to trickle charge the golf cart battery). Or with a high power system with a fridge where the fridge can wipe out your battery in a few days, you also know where you are at any time and can compensate. It is much more of a hassle to try and get this same info with just a voltage measurement since you have to let the batteries relax (no load or charging) for a relatively long time to get an accurate measurement and temperature will also change the voltage... ends up being a hassle to be accurate. With the charge monitor, press a button and you get a display of exactly where you are at amp * hour wise. You also get this reading without shutting off any loads or charging that is going on - which is convienent.

If anyone did want to look at the charge monitor option, this is the one I have - its worked fine
http://www.xantrex.com/power-products/power-accessories/linklite-battery-monitor.aspx

If I were buying again, I would go with this one - cheaper, little better specs. http://www.jamestowndistributors.com/userportal/product.do?part=136429&engine=adwords!6456&keyword=product_ad&type=pla

Fernando Martinez · Mar 8, 2014

Hi JQ,

My CPAP has a power supply that that goes from 110 to 12V which plugs to the unit. I took the 12V side cable and installed a male/female 12V outlet/socket. When I head out to the boat I disconnect the 12V plug from the outlet and leave at home the whole power supply. On the boat I then plug the 12V male plug to my on board 12V outlet. I would have used a separate 12V power cord to not touch the factory power cord but the powerplug that goes on the unit didn't look standard so I went ahead to mod the factory cable. I hope this makes sense.

Best regards,

Fernando

Kestle · Mar 8, 2014

Fernando Martinez said:
Hi JQ, My CPAP has a power supply that that goes from 110 to 12V which plugs to the unit. I took the 12V side cable and installed a male/female 12V outlet/socket. When I head out to the boat I disconnect the 12V plug from the outlet and leave at home the whole power supply. On the boat I then plug the 12V male plug to my on board 12V outlet. I would have used a separate 12V power cord to not touch the factory power cord but the powerplug that goes on the unit didn't look standard so I went ahead to mod the factory cable. I hope this makes sense. Best regards, Fernando

My Dad uses a CPAP machine, and I'd like to take him on some overnight sails. Could you tell me the make and model if yours?

Sumner · Mar 8, 2014

Kestle said:
My Dad uses a CPAP machine, and I'd like to take him on some overnight sails. Could you tell me the make and model if yours?

Most of these are 12 volt and come with the 110/120 to 12 volt brick. If his doesn't plug directly into the wall check the brick and see if it has a 12 volt output. If so there should be a cable avaiable with the 12 volt plug on one end and the plug for the CPAP on the other.

We have two Respironics, one about 5 years old and the other new (system 1) and they both run on 12 volts. The older is about 1 1/2 amps without the humidifier going (I only need that in the dry west). They both have 12 volt plugs with cords as accessories,

Sum

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JonnyQuest · Mar 8, 2014

+1. Mine is a Philips Respironics and runs on 12v, but has a power brick to step down from the 110vac house current. Not sure if mine came with the 12 v plug but it can be ordered for the unit.

Regards

JQ

Maine Sail · Mar 10, 2014

walt said:
I’ve had both series (2 six volt) and parallel (2 12 volt) and prefer the 6 volts because its been my experience that the identical current in each battery ends up requiring less water maintenance. My experience is only with wet cell. My two 12 volt batteries always in parallel lasted about 2 or 3 years before they were just trash, my two 6 volt batteries in series is going on I think 4 now and show no signs of aging that I can tell.

This really has little to do with series or parallel and more to do with battery type/design. A 6V battery is simply a better built battery and a better cycling battery.

Any 12V G-24, 27, 31 etc. are really not so much a true "deep cycle" but an adapted for use "deep cycle". More of a label/sticker than a reality...

Trojan for example states their 12V marine SCS deep cycle batteries, at 50% DOD, are rated at just 600 cycles. Their 6V GC2 golf car batteries, like the T105, are rated at 1200 cycles! Of course these are lab numbers and you'll never see that in the real world, out of either series. You will see longer life out of 6V golf cart batteries vs. 12V in the same application however when given the same treatment. Even when 6V GC2 batts are placed in series/parallel they still outlast 12V batteries...

That Trojan rating is double the cycle life, per Trojan Battery.... Deka / East Penn / West Marine (all the same batteries) claim 350 lab cycles for 12V deep cycle and 700-1000 for GC2, again, more than double.

Other brands building cheaper/price point 12V "deep cycle marine batteries" will do even less cycles than East Penn, Trojan or US Battery. The two best 12V deep cycle marine batteries out there, for G-24, 27 & 31, are the Trojan SCS and the US Battery DCXC. Personally I feel the US Battery DCXC is the dominant 12V deep cycle battery, but still not a GC2 6V..

In the real world, where I work, most 12V batteries never even make 125-150 cycles before death. It is usually the owner who murders them...

When I do seminars I open them up by asking a series of questions about boat use; How many weekends? How many over nights? Do you know how deeply you discharge? Do you take week vacations? Multiple weeks? How much time at a dock vs. anchor when off crusing? etc. etc. etc.. We write all these down on the white board. I then move into; How long do your batteries last...? We then break this down by averaging the cycle life. People are always shocked at how few cycles they actually do before they have murdered their batteries..... The last seminar I did we came up with an 84 cycle average.......! Boats with 6V almost always get better and longer life when these questions are asked..

The thicker plates, case design, case height etc. do make differences. A 6V GC2 battery has 3 cells and weighs 66 pounds vs. the 12V G-31 battery having 6 cells and weighing the same. Which battery has the thicker plates, the one with 3 cells or the one with 6 cells?

While I don't see the 50% differences in the "real world", I do see 20-40% longer life "on average" out of true deep cycle golf car batteries vs. 12V "marine style" batteries. The biggest factor in any of these batteries is the owner. The owner has the most control over how long batteries last and no one ever hits lab numbers, in the real world.....

walt · Mar 10, 2014

My experience was party due to just the different battery types but it was also due to series vs. parallel.

A somewhat common thing to happen with wet cell parallel batteries is that one of the two batteries will use a LOT of water and the other battery will use very little water. I had this happen and was only charging with a 20 watt solar panel. Both batteries were same model, brand, date code, purchase time and had a "balanced" hook up.

The 12 volt battery that had the big water loss was REALLY trashed. The other one probably still had some life but regardless, I changed to the two six volt batteries.

Now that I have the two six volt series batteries, I tend to check the water about the same as before (which is not nearly often enough) and both batteries pretty much always have the same (and small) water loss.

Note that a normal 12 volt battery is simply 6 cells in series. Two 6 volt batteries is also 6 cells in series..

Francois · Mar 10, 2014

2 X 6 volt vs 1 X 12 volt

TaZ_Izzy said:
WOW!!!! thnkx for the link!!!

Without a doubt the 2 six volt option gives you a lot more power (amp hrs) than the single deep-cycle 12 volt. Keep in mind a 12 volt battery is fully charged at 12.8 volts & that is where the chargers start limiting to keep from overcharging. Six volt battery is full at 6.3 volts for a total of 12.6 volts and a regular 12 volt charger does not know this & tries to get it to the 12.8 volts so if left for long periods unattended you tend to overcharge with the resuklting evaporation of the acid letting the battery run dry

- just a word of caution. Small solar panels (normally under 10 watts) do not need a controller.

Maine Sail · Mar 10, 2014

Francois said:
Keep in mind a 12 volt battery is fully charged at 12.8 volts & that is where the chargers start limiting to keep from overcharging. Six volt battery is full at 6.3 volts for a total of 12.6 volts and a regular 12 volt charger does not know this & tries to get it to the 12.8 volts so if left for long periods unattended you tend to overcharge with the resuklting evaporation of the acid letting the battery run dry - just a word of caution.

This is untrue. Charging voltages vary slightly by brand but within a brand 6V & 12V voltages are usually identical and only vary based on chemistry not voltage. Trojan for example wants to see 14.6V - 14.8V for absorption for either 6V in series for 12V, or 12V..

Francois said:
Small solar panels (normally under 10 watts) do not need a controller.

This is a myth, if you leave the panels connected and unattended.. A 10W panel can EASILY cook a 225Ah bank of batteries. Had that exact scenario happen to a customer..

Maine Sail · Mar 10, 2014

walt said:
My experience was party due to just the different battery types but it was also due to series vs. parallel.

A somewhat common thing to happen with wet cell parallel batteries is that one of the two batteries will use a LOT of water and the other battery will use very little water. I had this happen and was only charging with a 20 watt solar panel. Both batteries were same model, brand, date code, purchase time and had a "balanced" hook up.

The 12 volt battery that had the big water loss was REALLY trashed. The other one probably still had some life but regardless, I changed to the two six volt batteries.

Now that I have the two six volt series batteries, I tend to check the water about the same as before (which is not nearly often enough) and both batteries pretty much always have the same (and small) water loss.

Note that a normal 12 volt battery is simply 6 cells in series. Two 6 volt batteries is also 6 cells in series..

Walt,

You perhaps had.

A contaminated battery
A bad battery
Two different batteries (not as uncommon as you would think with battery distributors who private label. I have two "identical" batteries, according to the labels, in my shop right now that are not even the same brand let alone type..)

I service hundreds of batteries in parallel configurations and only in rare circumstances related to the above scenarios do I see varying electrolyte consumption..

Today I just checked SG, watered & equalized four Trojan SCS 225's (12V Group 31's) in parallel. They are 5 years old and all took identical water as they have for the last three years..

The more common scenario is a single cell or two cells that use more than the others. This happens in both series and parallel banks..

I still prefer series when possible, but parallel causes me no more or no less issues..

walt · Mar 20, 2014

The video showed a car being started using a capacitor - which was cool.

However...

The capacitor value was 350 Farads and if charged to 13 volts, holds a charge of 4550 coulombs (coulombs is a unit of charge).

Amp * hour is also a unit of charge and when the charge of the capacitor shown in that video is converted to amp hours,

The capacitor charged to 13 volts only has 1.26 amp*hours of charge.

Compare that to a group 24 battery which has something like 80 amp hours of charge.. Ie, a typical group 24 battery holds over 63 times as much charge as the capacitor shown in that video.

The battery is also much easier to use as its voltage stays relitively constant as it provides charge. The capacitor voltage is proportional to the charge left.

Maine Sail · Mar 20, 2014

walt said:
The video showed a car being started using a capacitor - which was cool.

However...

The capacitor value was 350 Farads and if charged to 13 volts, holds a charge of 4550 coulombs (coulombs is a unit of charge).

Amp * hour is also a unit of charge and when the charge of the capacitor shown in that video is converted to amp hours,

The capacitor charged to 13 volts only has 1.26 amp*hours of charge.

Compare that to a group 24 battery which has something like 80 amp hours of charge.. Ie, a typical group 24 battery holds over 63 times as much charge as the capacitor shown in that video.

The battery is also much easier to use as its voltage stays relitively constant as it provides charge. The capacitor voltage is proportional to the charge left.

The reason that works is because it takes very little Ah capacity to start a motor but a lot of inrush or short duration pulse current. I suspect if you tried that a second time it would not muster the oomph to do it again..

My buddy Bruce used to be the rep for the Race Cell Nano-Start batteries and these batteries are far smaller than that capacitor "bank". Unfortunately they were too expensive and did not sell well so the company dropped them but a batteru that would fit in the palm of your hand would easily start a Yanmar 3YM.. Bruce is a two-time Vendee guy and sold lots of these to hard core racers who demanded light weight..

I actually started a 3YM three times in under five minutes with this little beast.. Wighed less than the battery lugs......

timebandit · Mar 27, 2014

I personally do not like 2, six volt batteries . The reason being that if one battery fails you no longer have 12 V. I prefer two, 12 volt batteries with a battery switch.