Battery deal

[rana]

This just popped up again and took a second look at the specs... I wonder how they do their math??

182 reserve minutes, but also says 105ah @ 20 hour. When I calculate 182 minutes @ 25 amp draw I come up with 75ah @ 20.. not 105.

2 would get you 75 usable amp hours for $168. 2 - 6v "big box" true deep cycle batteries would give you 220ah or 110 usable for $170 and would have a longer lifespan.

[clr]

Does any one have a good suggestion to where I may be able to buy the "big bob" 6v golf cart batteries. The only big box that seems to sell them is Costco and I life in central Illinois with no Costco. Sams club has some 6v batteries but they are not well rated by customers. Thanks for the help.

[pgandw]

Originally Posted by Yarome

This just popped up again and took a second look at the specs... I wonder how they do their math??

182 reserve minutes, but also says 105ah @ 20 hour. When I calculate 182 minutes @ 25 amp draw I come up with 75ah @ 20.. not 105.

The total available charge is smaller when the discharge rate is higher. 25 amps for 182 minutes is rougher on the battery than 5.25 amps for 20 hours.

Fred W

[doneuald]

so I guess my question is How long will this battery last if the draw is 1.08 amps?
My cpap is rated for 1.08 amp/ hour
Don
PS until it dies doesn't quite cover it when the DW gets woken up at 3 am form me snoring when it dies! ; )

[doneuald]

the battery I'm using is a Exide stowaway deep cycle 27MDCST
675 marine cranking amps/ 182 minutes reserve capacity/ 105 amp hours @20 hrs
Just trying to understand what the numbers mean
Don

[bikendan]

Originally Posted by doneuald

the battery I'm using is a Exide stowaway deep cycle 27MDCST
675 marine cranking amps/ 182 minutes reserve capacity/ 105 amp hours @20 hrs
Just trying to understand what the numbers mean
Don

If the battery has a CCA rating, it's NOT a true deep cycle battery.

[boondocking]

Originally Posted by doneuald

the battery I'm using is a Exide stowaway deep cycle 27MDCST
675 marine cranking amps/ 182 minutes reserve capacity/ 105 amp hours @20 hrs
Just trying to understand what the numbers mean
Don

At a 105 amp hour rating you would have about 52 usable amp hours before the battery should be recharged. (52 divided by 1.08 = 48.14) So you would have roughly 48 hours of run time for the cpap.

[doneuald]

Now the next question to charge the battery can I run my generator with a battery charger at 6 amps to charge it for 8 hours or hook it to the solar panel with my Trojans to charge it
I was told not to mix types of batteries because the maintenance free will charge before the Trojans therefore the Trojans will not be fully charges

[boondocking]

You are right, it is not a good idea to try charging batteries that have different charging parameters.
A 6 amp charger will not bring a 50% depleted 105ah battery up to 100% charge in 8 hours. Get yourself a 15-20 amp 3 stage charger and you should be good to go.

[doneuald]

So as it stands I used the battery on Tuesday night and Wednesday morning it read 12.83 volts
Have used it wed, thurs, Friday nights and it now reads 12.68 volts so I have to say the Cpap is not drawing what the manufacturer said or the battery is doing very well and can still be used for a couple of more days before needing a charge

[boondocking]

That's great !
Looks like you will maybe need to charge it every 4-5 days.

[doneuald]

If it works out I should get 6 nights out of it, it's only running the Cpap at this point so it should be alright

[Brentf]

Are you using the humidifier/heater on the Cpap? Some of the CPAP's shut the heater and humidifier off when on 12 volt. Without that you are pretty energy thrifty and your marine/ Rv 'deep cycle' will give you a year or two.

Next time you replace your battery find a golf cart place and get a 12 volt Trojan, 150 amp. It will give you a long life and lots of reserve power. I've used marine deep cycle batts for years and they just seem to die after 2-3 years. The Trojans hang on twice as long, which not only cuts the price in half but the pain of replacing in half. What good is saving a few bucks when you have to drive into town and spend that savings on gas.

[doneuald]

I have the humidifier but don't have it turned , the jumper packs I was using only run 3 days max and only lasted one season. Going by cost I'm trying to wire the Cpap into the trailer supply because when at the cg I have two Trojan t105's supplying the trailer and they're charged with solar so this is I hope temporary . So far the deep cycle has lasted 4 nights and should go two more without charging, we'll see
Don

[doneuald]

Update, the battery lasted 6 nights altogether, as it stands
I fully charged the battery and used it tuesday night before taking the readings Wednesday morning
The load was a resumed s9 elite cpap that draws 1.08 amps at 12 cm of water column no humidifier
Wed morning voltage was 12.83 volts
Thursday morning voltage 12.77 volts
Saturday morning voltage 12.73 volts
Monday morning voltage 12.66 volts
So as far as I can tell this battery should last at least a week before recharging
If anyone has different results please let me know
Don

[Brentf]

Good to know, thanks