Adding second battery - Fiberglass RV


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Old 07-19-2009, 07:12 PM   #1
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Trailer: Bigfoot 17 ft Center Bath
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Hi,

I have a bigfoot 17' tt and would like to add a second battery. I don't believe there is enough room on the tongue as there is a fiberglass cover over the battery/propane. Has anyone added a second battery to a bigfoot trailer or other?

Thanks

bill
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Old 07-20-2009, 11:15 AM   #2
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Bill,

Here is the link to my post for upgrading to two batteries.

Battery Upgrade

Topic Title: Bigfoot Battery Upgrade, Installing two Trojan 6 volt T145 golf cart batteries on tongue of trailer

Dean
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Old 07-20-2009, 09:10 PM   #3
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I'm not sure that there is enough room in the front "A" frame for two batteries on the Bigfoot 17. I think the larger Bigfoots have just enough extra size using smaller propane tanks (same 20lbs tanks found in the 17) to make this work. I carefully measured my 17 with the dropped tray two battery scheme in mind, and came up an inch or two short. While you may be able to shoehorn everything in, I don't think there would be enough clearance to remove the propane tanks with the cowl in place.
Perhaps someone who has actually accomplished this with their 17 foot will respond, as I ruled it out after measurement only.

You can, however, put a considerably larger single battery in the 17 by filling in the area between the propane tanks and the existing battery tray. This will allow enough room to fit a larger battery by shifting it's location rearward. Buy a large battery box and install a Trojan SCS225 130AH 12V deep cycle, or better yet, a Trojan J150 deep cycle or T1275 12V golf cart battery which are basically both the same battery with 150AH capacity. I used the SCS225 for the last six years and recently replaced it with a T1275. The T1275 (J150) has the same footprint as the SCS225 but is roughly an inch taller and will just fit in the same battery box. The T1275 (J150) is a heavy duty 12V true deep cycle designed for golf cart use, and will likely perform in a similar fashion to the 6V golf cart batteries as far as cycling is concerned, although with less total capacity.


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If you simply must have more capacity, I think it is possible to weld in a 4" dropped battery tray, and use something like the 12V Trojan J185H with 225AH capacity. This is a fairly expensive battery (http://www.staabbattery.com/product/J185H-AC.html) which weighs well over 120lbs. An enclosed battery box may out of the question or have to be fabricated to suite. If this battery was properly maintained, it would probably last 8 to 10 years, which might take some of the bite out of the initial cost.

Steve.
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Old 07-20-2009, 09:13 PM   #4
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Name: Michael
Trailer: 1993 Bigfoot 17 ftCB / 2011 Toyota Sienna
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Hi Bill;
I installed an AGM size 27 on the tongue and a 2nd AGM size 27 under the door side dinette seat.
It even helps balance as more heavy stuff is on the drivers side.
The power cable (8 gauge) runs across the dinette area in behind the wood trim and joins up at the Converter box.
If you do a search on my name, you'll see lots of stuff I did on my Bigfoot 17CB.
Lots of battery power now, including the Link 20 monitor system.
Good luck.
Mike

Quote:
Hi,

I have a bigfoot 17' tt and would like to add a second battery. I don't believe there is enough room on the tongue as there is a fiberglass cover over the battery/propane. Has anyone added a second battery to a bigfoot trailer or other?

Thanks

bill
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Old 07-20-2009, 09:40 PM   #5
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I've often thought that if I needed more capacity that I'll add solar charging abilities to my Scamp 13'. I bought a Trojan SCS 225 a couple of years ago and have been very satisfied with its performance. I just came back from a 10 day trip and only on the last morning did I notice that the water pump start to slow just a little. Since I converted all the lights to LED and cold-cathode fluorescent my typical trip of 3 nights consumes less than a 1/4 of the battery's capacity. Of-course if it gets dark earlier, then I consume more. Point is, the LEDs are really efficient.
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Old 07-20-2009, 09:59 PM   #6
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If your existing battery has been through several discharge/charge cycles, it will degrade and shorten the life of a new battery connected to it. It makes sense to wait until your battery needs to be replaced, and then buy 2 new ones, which should be identical in make/model. Also, it's preferable to use 2 6-volt batteries in series than 2 12-volts in parallel. This info comes from "Managing 12 Volts" by Harold Barre, and is just the tip of the iceberg.

As a side note, you should never discharge the battery below 50% of its capacity, and plan on generally not charging to above about 80% (just occasionally to 100%). This means that most of the time, you have only about 30% of the battery's total capacity available between charges...

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Old 07-21-2009, 12:03 AM   #7
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Quote:
As a side note, you should never discharge the battery below 50% of its capacity, and plan on generally not charging to above about 80% (just occasionally to 100%). This means that most of the time, you have only about 30% of the battery's total capacity available between charges...

Don
Hi Don,
I fully agree with not discharging below 50% for best battery life, along with your other battery recommendations.
I am, however, interested in why one would only recharge to 80% with a multistage battery charger, other that it does take a long time to reach a true 100%. I monitor my battery with a Xantrex Link Lite, which takes Peukert's into consideration and both my Intellipower converter and my solar controller recharge the battery to 100% every time. Well, the solar not every time, depending on the conditions, but ideally, yes. Both charge methods incorporate multistage algorithms.

To avoid sulphation the battery should be subjected to a equalization charge occasionally, but this involves maintaining a lead acid battery at around 14.5 volts for several hours. This is effectively an attempt to charge the battery beyond 100%, which is not possible, but does help to remove sulphation and prolong battery life by ensuring all individual cells actually reach full charge.
I think most multi-stage chargers will ramp the battery quickly to 70 to 80% and then taper back the current to top the battery to near 100%. This will take quite a few hours, but the battery will end up near 100%, assuming it is in good condition. At this point the charger will enter the "float" mode maintaining the battery at around 13.2 volts.
The overall capacity of the battery will drop with age and number of cycles, but I think one is still charging to 100% of the remaining capacity.

Perhaps you could elaborate on the 80% figure? I do think that the use of a simple single stage charger probably would result in somewhat less than actual full charge, and will shorten battery life. Both very good reasons to use multi-stage chargers with equalization modes.

Steve.
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Old 07-21-2009, 12:58 AM   #8
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When we had our 13' Burro Mike mounted an extra battery tray to carry a spare on the front frame opposite the original, it was a good balance, but the Burro only had one propane tank, which was centered on the frame, so there was room. They were not connected, it was simply a way to carry a spare.

With the Escape, though we've bought a solar panel, it is not hooked up yet and Mike, having 'spare' consciousness, bought a spare battery to carry along - in the trailer while traveling, set in car when camping. A little awkward, but gives us the security of extra power if needed until solar is connected (our rural lifestyle has several uses for a deep cell battery so having bought an extra is never a waste). We've even stored it under the trailer when settled in, yes there is a risk of it being taken, but it really isn't visible.
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Old 07-21-2009, 09:07 AM   #9
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Trailer: Bigfoot 17 ft Center Bath
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Thanks everyone for their response. I think Steve is right about the room on a 17'. I too have took some measurements and it seems very tight. I didn't know there were bigger 12v batteries available but looks like a good option. Michael... very interested in the propane conversion to generator.

I guess I should back up my question a little. My wife and I are planning a trip in from ontario to alberta at christmas then heading south and want to be able to stay in the trailer while traveling and also do some skiing while out west. We have a 1500 series bigfoot (no heated tanks and no double pane windows). We would like to know how much battery power we would expect to use to run the furnace for 2 days in -15C (5F) temps (no tv running just the usual monitors and some lights). We're looking at keeping the trailer at 10C (50F) for sleeping and could use the stove in the morning to warm things up a bit.

Have any of you had experience in this?

Thanks

Bill
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Old 07-21-2009, 11:16 AM   #10
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Quote:
Hi Don,
I fully agree with not discharging below 50% for best battery life, along with your other battery recommendations.
I am, however, interested in why one would only recharge to 80% with a multistage battery charger, other that it does take a long time to reach a true 100%.....

....Perhaps you could elaborate on the 80% figure? I do think that the use of a simple single stage charger probably would result in somewhat less than actual full charge, and will shorten battery life. Both very good reasons to use multi-stage chargers with equalization modes.

Steve.

Steve,

Yes, it's because at 80% of capacity, the ability of the battery to accept amps is lowered, and it takes a long time to get to 100% from there. Of course, if you always have access to 120V, this doesn't matter, and once you're at 100%, the converter/charger will maintain a full charge while powering all of your 12V usage. But if you're relying on just the battery plus tow vehicle charge, and maybe also solar, you shouldn't expect to reach much more than 80% most of the time. It's possible to get a multi-stage charger for your tow vehicle alternator, but that's unusual, and still wouldn't increase the rate of charge, just protect the battery from gassing & sulfating. I guess it's possible to install a large enough array of solar panels to keep you at 100% and power your usage, but that's also unusual and I believe it would be very bulky and very expensive. And no matter how many amps you have available whether from solar or a multi-stage AC charger, once the battery is charged up to the 80% level, it will only accept a few amps, slowing down the process significantly. So just for practical reasons, it's best to count on only 30% of battery capacity being available, even though at times you can get more. (When first starting out with a full charge, for example, you have the full 50% available before recharging is necessary).
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Old 07-21-2009, 09:33 PM   #11
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Steve,

Yes, it's because at 80% of capacity, the ability of the battery to accept amps is lowered, and it takes a long time to get to 100% from there. Of course, if you always have access to 120V, this doesn't matter, and once you're at 100%, the converter/charger will maintain a full charge while powering all of your 12V usage. But if you're relying on just the battery plus tow vehicle charge, and maybe also solar, you shouldn't expect to reach much more than 80% most of the time. It's possible to get a multi-stage charger for your tow vehicle alternator, but that's unusual, and still wouldn't increase the rate of charge, just protect the battery from gassing & sulfating. I guess it's possible to install a large enough array of solar panels to keep you at 100% and power your usage, but that's also unusual and I believe it would be very bulky and very expensive. And no matter how many amps you have available whether from solar or a multi-stage AC charger, once the battery is charged up to the 80% level, it will only accept a few amps, slowing down the process significantly. So just for practical reasons, it's best to count on only 30% of battery capacity being available, even though at times you can get more. (When first starting out with a full charge, for example, you have the full 50% available before recharging is necessary).
Hi Don,
Thanks for the clarification, I thought it must have something to do with the extended top up time required for full charge. In the full sun I am able to easily achieve this with my relatively small 130 watt solar array , but I usually only pull down the battery 20 to 30 AH per day. I will see around 8 amps peak charge from my solar controller, and the amp hour meter indicates that the entire usage is replenished by the end of the day. The Xantrex meters also compensate for the fact that more amp hours have to be returned to the battery than have been used to return to full charge. Of course, poor weather or shade will spoil this happy situation.

Your point is a good one though, especially if you are recharging with your vehicle or even with a generator powering a multi-stage charging converter. It will be often impractical to run either long enough for full charge, as I have seen in practice. My converter will initially charge at 40 amps into a flat battery, and will accumulate AH quickly for the first few hours, but probably would take 8 hours or more to fully replenish the battery. I don't like running a generator unless absolutely necessary, so I only run it long enough to replace most of the AH and the charging current has tapered back to an amp or two. Generally, I only have to run the Honda for 1 to 2 hours every 2 or 3 days when the solar is compromised. The Link Lite meter is very handy in minimizing run times for the most AH returned, and deciding when to recharge.

In this case, I am also not realizing full charge, so your were correct in stating that a diminished charge could be expected. I guess it was just that personally I don't find that this is the case most of the time. Thanks again for the clear explanation.

Steve.
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Old 07-22-2009, 01:37 AM   #12
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As a side note, you should never discharge the battery below 50% of its capacity, and plan on generally not charging to above about 80% (just occasionally to 100%). This means that most of the time, you have only about 30% of the battery's total capacity available between charges.
Well . . . yes and no. Standard "flooded" batteries should not be discharged below 50% (12v) where the sulfation process starts to accelerate, with the sulfation process going faster as the voltage drops.

AGM and Gel Cells resist sulfation, so you can discharge them to 30 (AGM) to 40 (Gel Cell) percent, 11.7 to 11.9 volts (respectively). AGM cells can actually be fully discharged to 10.5 volts (0% charge remaining) then re-charged without developing significant sulphation damage. That sort of treatment even just once will kill a flooded or gel cell battery.

Charging is trickier. Flooded and AGM cells can be charged at a fairly high rate and voltage until they reach 80% capacity, after which the battery charge rate needs to be reduced to avoid damaging the battery. Gel cells have to be charged at a slower rate, period, or little bubbles form in the gel that permanently compromize the battery.

More advanced charge controllers are programmed with a three (or more) stage charging system that maximizes the charge rate for a set interval, then backs off to 14-point-something volts (the decimal varies from manufacturer to manufacturer), then drops down to "float charging" at 13.6 or so volts to keep the battery at 100% charge. Some have jumpers that set the appropriate behavior for flooded vs AGM batteries.

Cheap controllers are simple on/off switches that shut down when the battery reaches 80-90% charge.

Fancy controllers do the multi-stage charge thing, but have battery temperature sensors that help them better optimize the battery's charging cycles. Some have de-sulphation cycling that can extend a battery's lifetime. For the most part I'd rather spend my money on more LEDs or battery capacity than on these extra controller features.
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Old 07-22-2009, 01:53 AM   #13
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To avoid sulphation the battery should be subjected to a equalization charge occasionally, but this involves maintaining a lead acid battery at around 14.5 volts for several hours. This is effectively an attempt to charge the battery beyond 100%, which is not possible, but does help to remove sulphation and prolong battery life by ensuring all individual cells actually reach full charge.

Perhaps you could elaborate on the 80% figure? I do think that the use of a simple single stage charger probably would result in somewhat less than actual full charge, and will shorten battery life. Both very good reasons to use multi-stage chargers with equalization modes.
Actually the best desulfination chargers use short pulses of 20+ volts at carefully timed intervals to take advantage of the lead sulfate crystal's structure and get it to break up. As for the 80% figure, batteries are pretty good at finding unused parts of the lead plates to store incoming charge on until they reach 80% capacity. After that the battery takes longer and has to work harder -- which means it generates heat -- to store the incoming charge. Charge controllers know that excess heat is a battery's worst enemy, and monitor the battery's voltage, temperature, and/or specific gravity (a measurement of how much acid is in the battery water) to figure out what charging rate would work best at any given moment.

My old 50-watt panel could easily get my Optima AGM battery from 40 to 90+ percent charge on a sunny day. Now I have a second 55 watt panel it can go from 20 or 30 percent to 100 on almost any day.
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Old 07-22-2009, 11:28 AM   #14
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We have a 1500 series bigfoot (no heated tanks and no double pane windows). We would like to know how much battery power we would expect to use to run the furnace for 2 days in -15C (5F) temps (no tv running just the usual monitors and some lights). We're looking at keeping the trailer at 10C (50F) for sleeping and could use the stove in the morning to warm things up a bit.

Have any of you had experience in this?
Bill,
There are so many factors to consider. But, I know it helps when people respond with their experiences, so here is ours:

We own a 21 foot Bigfoot with the winter package, which includes the dual pane windows. We camp each year at Rocky Mountain National Park during the rut and experience weather like you are describing. We sleep with the inside temperature in the high 50’s and turn the heat up in the morning until comfortable (high 60’s) and keep it there most of the morning until we leave for our day activities, then turn it back up in the evening.
The fan on our heater draws 8 amps while running, so the amp hour usage can quickly add up over a 24 hour period.

We have a Xantrex Links 20 to monitor power usage. We use LED lighting, watch an occasional movie, power laptop for school work, run fantastic fans in summer and heater fan in winter. Our summer usage is between 10 ahr to 40 ahr per day and our winter camping varies even more depending on the outside temperature, but will often be around [b]40ahr.

Our solar can provide up to 60ahr of charge during the summer months, but just keeps up with our needs in the winter.

So, if you're looking for a guess, because that is all it is, then I guess your usage will be between 20ahr and 45ahr.

[b]Note: One should not try to heat the trailer with the stove. There should be warnings about this in the owner’s manual and on the stove.

I hope this helps, Dean
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