Rv/Marine 12V batteries--Technical info needed

[john59]

I did some research on adding amp hours to our 5'r.

In the RV is a Deka DP24, 12V, 65 amp battery (based on 20 amp hrs). The batterty tested 100% on all cells with a battery hydrometer

I bought and matched another Deka DP24 (tested 100% all cells) again, tested with a battery hydrometer and hooked them up in parallel.

Here are my questions:

Question a) Does this screw up the (I call them idiot lights) inside the trailer on the control panel. Not the black, grey, fesh water lights, but the battery charge capacity lights, i.e 99%, 75%, 65% and R.

We went dry camping for 2 nights to Washington DC. We ran the DC lights, fans and the gas heater for a little bit, the hot water (gas) and the water pump--on and off as needed.

I kept checking the idiot battery charge capacity lights and they did drop to 75%. Checked again and it was 99% with no charging. These numbers did jump back and forth between 75% and 99%. Again with no charging.

Can these lights be trusted or am I missing something ?????? Do I need another way to measure capacity (beside the hydrometer). Maybe the light fluctuation is normal or maybe it is not.

Question b) If the batteries are drawn down (say to 65% or R), will they charge back up to 99%, on the control panel idiot lights, on my truck alternator while tied together in parallel ???????????

Input/thoughts would be greatly appreciated.

john

 

[Pirate-Jeff]

The lights are only checking the voltage not how many amps are in the batteries. When batteries sit for a short time the voltage will increase a small amount after the load is removed. If the voltage was border line at 75/100 percent on your meter that would explain the increase on your panel.
That meter is reading a 100% charge at 12.8 volts and 12.6 volts as 75% . You want to test the amps so get yourself a load tester. I saw this one at harbor freight tools in Lancaster this past Friday it will test the voltage and the remaining amps in the batteries.

Think about it like a garden hose:
Voltage = Pressure
amperage = volume, or how much work it will do and for how long

http://www.harborfreight.com/100-amp-6-volt-12-volt-battery-load-tester-90636.html

Depending on how your 5'er is wired the truck can charge both Batteries on a long trip. Also remember that deep cycle batteries take longer to charge than regular car batteries and deep cycle batteries like to be charged at low amperage say 10 amps or less.

If you are worried about leaving something on and killing both batteries, get yourself a disconnect switch. that way you can disconnect or use just use battery #1 or# 2 or both

 

[john59]

Jeff thanks for the info (U DA BESTIS).

PS: The Lmouths are starting to really turn on in our community pond.

I changed some of the #s in my first thread post---Not 100, 75, 50, 25 %, actually they are 99%, 75%, 65% and R. I assume R means "you better charge right now".

What do you expect ??? Being a former Accountant accounts for some errors, being old (I meant to say mature) is another part, but the inborne genes of a Fisherpeeple and exageration accounts for most of it.

Thanks, john

 

[john59]

Jeff thanks for the info (U DA BESTIS)---I did learn from my bass boat. I had two 105 amp deep cycles. One to start the gas kicker and one for the trolling motor. I could switch the starting to back-up the troller, if needed (this was rare)---At home I had an 8 amp slow charger---The batteries lasted 13 years. They were independent and not hooked up parallel.

PS: The Lmouths are starting to really turn on in our community pond.

I changed some of the #s in my first thread post---Not 100, 75, 50, 25 %, actually they are 99%, 75%, 65% and R. I assume R means "you better charge right now".

What do you expect ??? Being a former Accountant accounts for some errors, being old (I meant to say mature) is another part, but the inborne genes of a Fisherpeeple and exageration accounts for most of it.

Thanks, john

 

[big kahuna1]

I hvae actually heard that alot of toy haulin boon dockers have changed to 6 volt (golf cart bateries) batteries in tandem. They claim they do a better job and will last longer. Don't know if it is true or not.