Planning Battery Upgrade--Need advice

[doc73]

I thought the batteries need to be matched.. Both new or the old one would kill the new.

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[Kenny kustom]

Originally Posted by doc73

I thought the batteries need to be matched.. Both new or the old one would kill the new.

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That's how I have always done it..
When I put duals in my jeep, I even matched the build lot.


2008 F350 CCSB V10
2016 Sabre 36QBOK

[Rbertalotto]

Thanks Kelly....I have room for one more 140w panel that I might add if I find myself running out of juice or using more amps.

The TV I bought uses a 12V "Wall Wart" converter. So I just hook it up to the 12V in the trailer without an inverter. I was at BestBuy and all the less than 32" Invicta TVs are 12V wall wart models. They even have a 32" with built in DVD that runs off 12V for $179!

I have a Xantrex 1000 watt inverter wired into the system but I only use it for the vacuum cleaner. Haven't found a good 12v vacuum cleaner yet. I've not tried the micro wave through the inverter yet.

[Blackhat6mike]

I believe you will need a larger inverter to run your microwave unless it is a very small unit. Most standard sized microwaves need 1200-1500 to start and 1100 to run. You can cook your magnatron if you under voltage it for long. Be very careful.

[Tom48]

Originally Posted by pgandw

Couldn't agree more. I had 2 size 24 12V in parallel. For some reason, and unknown to me, the converter 30 amp fuses (to the battery) blew. In desperation, I put a 10 amp charger I had on the batteries - it would not handle both at once. So I recharged one battery at a time, but did not get them exactly equal, or one battery had failed (unknown to me).

When I hooked up the 6 gauge parallel wires, the wires promptly melted their insulation and glowed cherry red. The off-gasing of the lesser charged battery had flames at the glowing wires and at the vent at the battery cell cap. With electrician's pliers (gripped on the rubber coating) I cut the wires, which put the fire out.

I replaced with two 6 volt golf cart batteries from Costco ($150 for both). 116 AH available instead of 80AH from the 12V batteries, no risk from unequal battery charges. A lot less expensive than I expected. The batteries were a perfect fit for my existing battery box. And yes I added one of those marine shut-off switches to isolate batteries from camper when desired/needed.

Since our A-frame is set up for long weekends, and not extended stays, I feel much more confident with the golf cart 6 volt setup. I have more capacity, and easier to maintain. If for some unlikely reason one of the batteries dies, we go home earlier on the weekend - the same as if we ran out of propane or water.

Photos to follow.

Fred W
2014 Rockwood A122
2008 Hyundai Entourage (minivan)
camping Colorado and adjacent states one weekend at a time
last trip - last weekend, 4 days in Lincoln, Nebraska

Here is my spin on RV/TT BATTERIES

So, much of what is said makes no sense to me, but the conclusion that 6 v GOLF CART BATTS are better, seem solid.

Everyone I know who has gone 6 volt is more than happy. Yes two 115 Amp 12v batts would be 230 amps, while Trojan T-105 at 220 each will each be just 220. 230 is more than 220, bUT What would it take to do that???? Two Group 31 may make 230 amps, but the length of that battery would prevent two from fitting on most TT battery rails, while most 6v batteries have the same footprint as the original, cheap, Group 24 batts and they are just a bit taller..

The Golf Cart batteries are TRUE deep cycle batteries and will last through many more discharge/recharge cycles than Car Batteries and the Duel purpose or Marine 12 volts we commonly see, are not really true Deep cycle batts and will not last as long as Golf Cart or TRUE DEEP CYCLE BATTS.

Remember as you calculate your needs that a fully charged 12 volt (or two 6's) sits at about a static 12.8 volts when fully charged and off the charger, (maybe a bit higher brand new) and when you use them down to a no load static voltage of 11.9 to 12.0 volts, you have used 50% so if you have 220 (brand new) amps you are down to 110 left.

Most "experts", that I have read, say that any time you take batteries below 11.9v (no load static voltage) you are putting AGE or undesirable WEAR on them. At 10.5 volt static no load voltage they are 100% discharged or all 220 amps GONE. Past that point you are probably doing permanent irreparable damage and you ought to start saving for new ones.

When you buy them, charge them full and have a solar system or charging schedule that will keep them from routinely running below 11.9 volts, no load static voltage during use and they will last for years longer than most expect.

The GUY WHO SAID RUN THEM DOWN AND CHARGE THEM UP A COUPLE TIMES to get them grooved in or what ever, is PROBABLY just WRONG. Sounds like a guy wanting to sell you more batteires sooner rather than later

[Tom48]

Originally Posted by Rbertalotto

Thanks Kelly....I have room for one more 140w panel that I might add if I find myself running out of juice or using more amps.

The TV I bought uses a 12V "Wall Wart" converter. So I just hook it up to the 12V in the trailer without an inverter. I was at BestBuy and all the less than 32" Invicta TVs are 12V wall wart models. They even have a 32" with built in DVD that runs off 12V for $179!

I have a Xantrex 1000 watt inverter wired into the system but I only use it for the vacuum cleaner. Haven't found a good 12v vacuum cleaner yet. I've not tried the micro wave through the inverter yet.

WOW, very nice looking install. How far is the run from the batteries to the inverter. Ours is a 2000 watt Pure Sine Wave Samlex looking similar to that one. It is about 3 ft of run to the batteries and fuses at 200 amps. It runs our little 1000 watt RVmicrowave no problem or my wife's hair dryer or her curling iron; while it charges all the toys. I ran a remote on off control, with volt meter and visual load meter. Turn if off when not in use as it runs 1.5 to 2.0 amps no load amperage when turned on. Yes our TV/DVD player is 12 v too.

[Rbertalotto]

The run from the batteries to the inverter is less than 18 inches. You want to keep this run absolutely as short as possible. I used four gage wire with 150 amp circuit breaker. From the inverter I have two sets of dedicated receptacles. One in the electric closet you see above and the other in the trailer. As I stated I tend to use just about everything at 12 V so I use the inverter very infrequently .

[Witch Doctor]

Originally Posted by bob caldwell

Harbor Freight sells Load checkers.

I bought the load checker from Harbor Freight cost around 21.00 bucks on sale, It is a lot easier for me then pulling a battery and taking it to Napa for a load test. It will give you all kinds of information, plus the important load testing. Never knew about them until Camaraderie told me it. So X's 2 Bob, and thanks Cam. They were just on sale last week.

[Ramblin Recks]

Originally Posted by Klipstr

The poster that suggested a very detailed power consumption study is spot on: you can't know what you need until you know what you need (that in honor of Yogi Berra).

The key to successful solar implementation on an RV is in two parts: understand your usage so you can size your batteries and thus your array and make dang sure you wire it all properly using the correct wire sizes everywhere. The most common mistake in installation is wire that is too small for the runs used resulting in insufficient voltage at the batteries during charging. The whole system becomes a waste for want of a buck or two more in wire.

X2....Could not agree more.

[camaraderie]

Originally Posted by Tom48

Here is my spin on RV/TT BATTERIES


Remember as you calculate your needs that a fully charged 12 volt (or two 6's) sits at about a static 12.8 volts when fully charged and off the charger, (maybe a bit higher brand new) and when you use them down to a no load static voltage of 11.9 to 12.0 volts, you have used 50% so if you have 220 (brand new) amps you are down to 110 left.

Most "experts", that I have read, say that any time you take batteries below 11.9v (no load static voltage) you are putting AGE or undesirable WEAR on them. At 10.5 volt static no load voltage they are 100% discharged or all 220 amps GONE. Past that point you are probably doing permanent irreparable damage and you ought to start saving for new ones.

Tom...while I agree with your overall assessment for this situation..I do want to correct a couple of minor errors of fact. FULL charge on a static (i.e. disconnected for 24 hours after charging to eliminate surface charge) is 12.73 ....not 12.8 which reflects a surface charge and does NOT give you knowledge that you have indeed reached a full 12.7. It simple tells you that the battery has not yet reached static state. You may be at less than 12.7 once the SC is wiped out which could be indicative of incomplete charging OR loss of battery capacity.

I'd also note that an 11.9 STaTIC voltage is LESS than 50% charge (closer to 35% and you are doing damage to you cycle life by discharging to this level. You can see all this from the Trojan chart below which is handy for all size batteries. You can also see that discharging a wet cell battery to 35% (65% discharge) instead of 50% costs about 25% your battery life cycles. While cycles are different for every battery...the curve for all wet cells is quite similar.

I'd also note that the 24 hour wait period to eliminate surface charge is temperature dependent and reflects ROOM temperature. If it is 95 degrees...12 hours will be enough...if it is 35 degrees...you might have to wait a week.

So...I continue to recommend a REaL battery monitor for those who boondock for their is NO other reliable way to see your actual state of charge WHILE camping and using equipment and charging mechanisms. Victron and Trimetric make good ones for the price of ONE premium battery.

[boondocking]

I believe Tom is right about the voltage of a fully charged set. I was curious so I checked my (2) 6v batterys that I fully charged 5 days ago and they read 12.81v. This was checkrd with a $400 Extech meter, so I know it is accurate.

[camaraderie]

I would suggest you still have some surface charge. There is not ONE battery mfr. who sez wet cells are 100% at 12.8+
I don't doubt your measurements.
Trojan 12.73V
Deka 12.6V
Interstate 12.66V

Easiest way to get an actual state of charge is a hydrometer. (1.265=100%) if you don't want to invest in a true monitor. But ya have to check each cell.

[boondocking]

OK, thanks. It is good to see that my 4 yr old 6 volters are still in really good condition that they are holding a surface charge for this long.

[brooklyncowgirl]

A brief update. We installed the new battery. I drained the old battery down to the charge level of the new battery and connected the jumper cables. After a couple of hours of waiting to see if any worst case scenarios that could result from two batteries of different age being linked happened, I checked the charge again and found that they were now equal and that there was no excessive heat or other indication that things were not going well. At that point we connected the trailer positive and ground cables and we were back in business.


The two batteries seem to be playing well together. It's been four days now and I've checked the charge daily. The charge is dropping as expected from the load from the background trailer systems and occasional use of lights, etc. but at roughly half the rate than before the second battery was added.


The verdict. So far so good.


Next step will be to buy one of those Trimetic monitors so I can stop having to take the lids off the battery boxes each morning then onto planning a solar system that will meet our needs for the big trip we're planning on when we sell the house.


Thanks to all of you for your input. You've all been very kind to a couple of thick headed newbies.

[boondocking]

Good to hear everything is working for you.
If you don't want to spent big money on a Trimetric monitor get one of the these.

http://goo.gl/BJx3aS

A lot cheaper and works like a charm.

[camaraderie]

That monitor does NOT measure state of charge on the battery system, amp hours used by the coach, CURRENT use of amps by the coach. It cannot do so because there is no shunt from the battery and it is not designed to do so.
It is fine for monitoring a solar panel(s) and what is happening with it but not the in/out net to the entire system or resulting battery bank SOC. You get what you pay for and if you plan to boondock ...you need a real monitor that takes account of everything IMO.

[boondocking]

That's all I ever do is boondock.
It does tell me the real time SOC, real time amps being used and real time % of capacity.
Works just fine for me.

[camaraderie]

If there are any negative wires attached to your batteries that do NOT attach to your monitor...and ONLY your monitor attaches to your batteies...then what you think you are getting is NOT what you're getting. Given the size of the screws on the monitor...I can guarantee that you are not monitoring what I said in the post above.
You cannot possibly be measuring true state of charge... you cannot possible be measuring true amps being used. You cannot tell how much longer your can run off your batteries before needing a charge and you cannot tell when they are Full during charging. Sorry...but enjoy your readouts if you like em...the Trimetric will pay for itself.

[boondocking]

It does tells me the voltage and amperage that the solar panels are producing.
No it doesn't tell me present amps being used or the SOC or % of capacity while the batterys are being charged. It does tell me that stuff when the batterys are not being charged, when I de-activate the cutoff switch for the solar panels.
It gives me all the info I need while boondocking.

[Ramblin Recks]

Voltage, current, and temperature all affect SOC. If voltage is related to battery state of charge, you have to compensate for voltage variation due to current movement through the battery not just when a battery is at rest.
That is great your setup is working for you, you understand your usage and capacity.