opnspaces
San Diego Ca
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Campinfan wrote:The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....or 4 6 volts which would effectively give me 2 12 volts. I hope that clears it up. If all things were even....I would have 4 x 12 volts @100 minutes a piece (just pretending here) so that would give me 400. If each 6 volt was 100, I would only have 200 because I know in series only the volts double not the amps but then they would be partially in series so then I would have the equivalent of 2 12 volt batteries @ 100 a piece for a total of 200. So it seems the 12 volt battery is a better idea until I think about how much lower you can drain the 6 volts.
Correct to a point until you look at real life. Typically unless you want to spend $400 per 12v you will find most 12v batteries are 75 to 90 ah. A typical 6 volt is 200 to 220 ah, so...
12v @ 75ah x 4 = 300ah or 4 x 90 = 360ah
You are correct that the 6v in series doubles only the voltage so
Two 6v @ 200 ah = 200ah. Four 6v at 200ah = 400ah.
Two 6v @ 220ah = 220ah. Four 6v at 220ah = 440 ah.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton
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wa8yxm
Davison Michigan (East of Flint)
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Campinfan wrote:The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....
With 4 of either I have to ask what size
GC-2 are about the same "Footprint" as Group 24 but taller.
So a box that fits 4 Group 24 (300 ah) would fit 4 GC2 Over 400AH
A box that fits 4 Group 31's (about 500 AH) would fit six GC-2's (or nearly 700 AH)
Plus the difference in minimum state of charge levels make the GC-2s way way better
Add to that the "Economy of scale" The GC-2 being the single most produced lead acid battery is of course the lowest price per watt hour.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times
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Campinfan
Washtenaw County, Michigan
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Thank you Chris! I really wont be boondocking. I am just thinking I will use it when we are driving and want the fridge to run. I have never had a MH before so I am a newbie in this arena. My current rig is a fiver with a residential fridge and that was new to me too. I have had numerous trailers with gas absorption fridges and just ran them off propane as we drove to our destination. So I may be asking some really dumb questions...lol
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2016 F 350 FX4 4WD,Lariat, 6.7 Diesel
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pianotuna
Regina, SK, Canada
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Campinfan,
The only dumb questions are the ones you don't ask.
Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp-hours of Telcom jars, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.
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Campinfan
Washtenaw County, Michigan
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So Pianotuna, are you basically telling me that I could get a DC to DC charger and then that would take the starting (chassis) batteries and use them to charge the house batteries? And of course the alternator would recharge the starting batteries.
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SJ-Chris
San Jose, Ca
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Campinfan wrote:So Pianotuna, are you basically telling me that I could get a DC to DC charger and then that would take the starting (chassis) batteries and use them to charge the house batteries? And of course the alternator would recharge the starting batteries.
The chassis batteries do not charge the house batteries. It is the chassis's alternator that charges everything (chassis battery, and house batteries if you have a DC to DC charger).
-Chris
San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs
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Campinfan
Washtenaw County, Michigan
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Thank you all, I am learning a lot. I ways thought my coach batteries recharged as I was towing. That is problem the root of my problem with my current rig. I was draining the batteries too low as I was running the fridge and driving long distances.
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valhalla360
No paticular place.
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Campinfan wrote:The reason why I say four of either is because I would have room for 4. That is why I have the question of 4 12 volts which would give me 4 times the amps of one....or 4 6 volts which would effectively give me 2 12 volts. I hope that clears it up. If all things were even....I would have 4 x 12 volts @100 minutes a piece (just pretending here) so that would give me 400. If each 6 volt was 100, I would only have 200 because I know in series only the volts double not the amps but then they would be partially in series so then I would have the equivalent of 2 12 volt batteries @ 100 a piece for a total of 200. So it seems the 12 volt battery is a better idea until I think about how much lower you can drain the 6 volts.
OK, I see a lot of folks responding are messing up on units and it's causing confusion (ie: someone suggested starting batteries have 3-5times the amp-hours for 30 seconds...which makes no sense).
Voltage:
- By wiring them in series, you add the voltages (ie: 2 batteries at 6v puts out 12v power.
- by wiring them in parallel, the voltage stays the same (ie: 2 bateries a 6v put out 6v power.
Amperage: For house loads, it's all but irrelevant unless running a big inverter. Amperage (typically shown as CCA~Cold Cranking Amps) is usually of concern for starting an engine. No harm in using a starting battery to start a engine but for the same size battery bank, a deep cycle will have fewer CCA.
Amp-Hours: This is a measure of the amp draw times the duration in hours. If you pull 8amps for 10hours ~80 amp-hr. It's important to understand that to use it correctly, you have amp-hr @ X volts.
Watt-Hours: If you are comparing batteries of different voltages, it's often better to convert t watt-hr. Watts = volts *amps. So 12v @ 10amps = 120watts. If you draw that for 10hr, you will use 1,200w-hr.
Once catch is how fast you deplete the battery will impact how many amp-hr (or watt-hr) the battery will put out. This is why 5 minutes cranking a truck engine will kill a 70amp-hr battery. Theoretically, 500amps for 5 minutes will use just over 40amp-hr but the battery likely won't crank the engine anymore. (look up the phuerket effect if you want more details).
So let's take your example of 4 12v Group 27 batteries vs 4 6v golf cart batteries wired for 12v:
- The 12v batteries will have around 90amp-hr each. Since you aren't changing voltage, you can multiply to get the total amp-hr ~ 360amp-hr total.
- The 6v batteries will have around 220amp-hr each but when you merge 2 to get 12v power, the amp-hr stays constant. Since you are combining 2 sets of 2, you wind up with 440amp-hr total (importantly @12v)
440amp-hr is significantly more tan 360amp-hr and hence why the 6v batteries are preferable.
Another way to calculate it is watt-hr:
- 12v @ 90amp-hr * 4 batteries = 4,320w-hr
- 6v @ 220amp-hr * 4 batteries - 5,280w-hr
You also get a little boost from the phuerket effect mentioned above as you are drawing at a slower rate (relative to the battery bank size) with the 6v.
Someone suggested it's OK to take the bank down to 20%...if you immediately start charging, it's only minor damage but if they will sit at 20% for hours, yes it does degrade the batteries.
PS: Lithium is very deferent in that they are largely unaffected by taking them down as low as 10%. This allows you to get away with a smaller battery bank in terms of amp-hr for the same usage. It does come with some catches in terms of management and proper charging or you can ruin an expensive set of batteries easily...but it's getting better.
Tammy & Mike
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valhalla360
No paticular place.
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Campinfan wrote:Thank you all, I am learning a lot. I ways thought my coach batteries recharged as I was towing. That is problem the root of my problem with my current rig. I was draining the batteries too low as I was running the fridge and driving long distances.
Properly set up, the alternator should be charging both starting and house batteries...no guarantee it's properly set up and often the charging line to the house battery bank is woefully inadequate. If you are drawing 20amps and only 6amps is getting from the alternator to the house bank, you will be running the house battery bank down...just question of if the bank can sustain the loss before you get into a campsite and hooked up to shore power.
Keep in mind, an old battery bank may only have a fraction of the original amp-hr rating.
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pianotuna
Regina, SK, Canada
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Properly set up is not possible unless you wish to buy a special purpose alternator. Or add a diode type device to the existing alternator.
The computer in the engine "looks" at the starter battery voltage. When the starter battery has recovered--charging is scaled back. Once that happens there is little or no charging of the house bank.
A dc to DC takes the incoming voltage and boosts it to an acceptable voltage for charging the house bank.
My dc to DC charger does a maximum of 20 amps. That works out to less than 5 amps per battery.
Because I have a larger than usual bank, I chose to set the output voltage of the dc to DC at 14.7 volts. Don't do this unless you have researched what the ideal charging voltage is for the house bank.
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