Weighty problem? 2 batteries on tongue?

[k0wtz]

my 40ft eagle bus had 2 of those big 8ds I would get 1 year out of them of course warranty 1 year.

so one time for grins I bought 2 of the largest 12v car batteries walmart carried they had a 5 year warranty I never had a problem starting the 8v71 diesel or the huge cat generator someone had put in there. the generator ran 2 13,500 ac units on top.

I didn't try to start the bus up in extreme cold though. those 8v71s didn't have glow plugs or any starting help except ether I suppose!

ap greens in mexico mo had battery powered fork lifts to move huge stacks of fire bricks around. I never understood how this could work I saw it in our grocery stores running little pallets around!

I know one bad cell can wreck everything!

bob

[floyd]

Originally Posted by John in Santa Cruz

if you want to run 2 12V batteries in parallel, they should both be identical, bought at the same time, wired together in parallel with short heavy gauge wires, and always charged and discharged together. if you do this, they stay pretty equivalent for their life, and your charger will just see them as one 12V battery with double the AH rating.

if you connect different 12V batteries in parallel, the stronger one discharges into the weaker one, and its never happy.

IMHO, 2 6V batteries in series is the ideal choice, as all the current goes through both of them.

It works best to hook the charger to the ground on one battery and the power to the other in a 2-12V combo. This helps prevent cascading and actually provides a more even charge. That's just fleet experience more than logic.

[Gerry]

Got a start on installing the new controller and wires through the floor and out to 1 battery on the tongue.
I did run the two charging wires out to battery compartment so if in the future I want to add a battery it will be there.
I was also installing new LED side markers so jumping from one job to the other slowed me down a bit.
Should have it all done soon and hope it works here in Maine were we do not have to many campgrounds with full sun on the sites.
We'll see.
Thanks for all the input.
Been thinking about this jump to solar for about 4 years and the deal I got on the panel and all the wires and controller was so good I couldn't say no.

[Franswa]

there are so may variables to play with....you have just acquired a new hobby and it's a fun one!

as in Maine, here in BC we have LOTS of CGs that are in the shade most if not all the time....for that you could pick up a smaller, portable panel that you could put out a ways from the trailer when parked in the shade....as a rule of thumb a smaller panel angled directly to the sun will generate as much power as a rooftop twice its size (wattage).....

that second wire you have installed on spec could be used for that...just connect to the "panel" terminal on controller and install a plug at the tonge end...easy to do

I run 70W on the roof and a 40W "deployable" as described above....kinda covers all the bases... cheers, F

[Raz]

Originally Posted by floyd

It works best to hook the charger to the ground on one battery and the power to the other in a 2-12V combo. This helps prevent cascading and actually provides a more even charge. That's just fleet experience more than logic.

What's cascading? It's not term I'm familiar with in regard to batteries. By making the connection as you suggest you know that both batteries are in the circuit. A lose connection will produce no output. I can't think of any other benefit.

While having the batteries matched is the ideal, I wouldn't worry too much if they're not, as long as both are "healthy" and the same group. In charging, the current will divide as required. Resting they will reach an equilibrium.

[Timber Wolf]

Somebody above posted $400 for lithium batteries, I would like to see that as these bad boys: https://battlebornbatteries.com/shop...cycle-battery/ are a grand plus. But two of them replacing the two 6V wet batteries on the tongue of my Scamp would effectively nearly double my capacity while halving the weight. That is a win-win, but for ten times the cost!

[rbryan]

Originally Posted by Timber Wolf

Somebody above posted $400 for lithium batteries, I would like to see that as these bad boys: https://battlebornbatteries.com/shop...cycle-battery/ are a grand plus. But two of them replacing the two 6V wet batteries on the tongue of my Scamp would effectively nearly double my capacity while halving the weight. That is a win-win, but for ten times the cost!

Not only costly, but way fewer amp hours than a pair of wet cell 6V GC2s. Going from 232Ah down to 100Ah? Not for me.

[Franswa]

while it's still a stretch...money wise...

232 vs 100 is really like 116 vs 90 (useable)...from what I've read

won't be long...quality control will get better, price will go down.....

Way back when some people used to say they'd never fly on a plane without propellers too!

[floyd]

Originally Posted by Raz

What's cascading? It's not term I'm familiar with in regard to batteries. By making the connection as you suggest you know that both batteries are in the circuit. A lose connection will produce no output. I can't think of any other benefit.

While having the batteries matched is the ideal, I wouldn't worry too much if they're not, as long as both are "healthy" and the same group. In charging, the current will divide as required. Resting they will reach an equilibrium.

A lot of truck batteries which were wired in parallel, have the positive and negative connections both on the same battery. It would seem irrelevant but when the truck is started frequently and driven short distances, the effect is that the "main" battery gets most of the recharge first. As a result, the second battery gradually over many starts, looses charge until the truck is run long enough to completely charge the main battery which when full will start to "cascade" the charge into the deficit which was formed over time in the second battery.
The effect is gradual, but real, real enough that I found the second battery commonly needed replacement while the main battery remained in service. The problem was solved by doing as described in my previous post.
I think that the minor benefit is worth it.

As you say, the batteries should equalize when at rest, but theory and practice don't always produce the same results.(bumblebees can't fly!)

This effect doesn't occur on "over the road " trucks which usually run long enough with each start to completely replenish both batteries. This would be true as well for those house batteries which see constant charging with long periods of light or no load.

[Gerry]

I do not plan to mount the panel on the roof but keep it mobile and the 20 foot leads that came with it I am hoping it will be fine. Plan to go on a 2 week trip not 25 miles away and see how it will work. I am sure that the wife will have the furnace going at night and a roof fan going during the day so it will get a work out for sure.
I also do not want to have to baby sit the panel during the day. When I go on a trip I want to leave it chained to a tree and go out sight seeing.
I know there is a risk of theft but, what-cha-gonna do. Insurance is the only answer.

[rbryan]

Originally Posted by Franswa

won't be long...quality control will get better, price will go down.....

Way back when some people used to say they'd never fly on a plane without propellers too!

My objection has nothing to do with a fear of adoption or an aversion to change. I do hope the prices go down as the manufacturing capacity and technology improves. My beef was simply cost.

[Raz]

Originally Posted by floyd

A lot of truck batteries which were wired in parallel, have the positive and negative connections both on the same battery. It would seem irrelevant but when the truck is started frequently and driven short distances, the effect is that the "main" battery gets most of the recharge first. As a result, the second battery gradually over many starts, looses charge until the truck is run long enough to completely charge the main battery which when full will start to "cascade" the charge into the deficit which was formed over time in the second battery.
The effect is gradual, but real, real enough that I found the second battery commonly needed replacement while the main battery remained in service. The problem was solved by doing as described in my previous post.
I think that the minor benefit is worth it.

As you say, the batteries should equalize when at rest, but theory and practice don't always produce the same results.(bumblebees can't fly!)

This effect doesn't occur on "over the road " trucks which usually run long enough with each start to completely replenish both batteries. This would be true as well for those house batteries which see constant charging with long periods of light or no load.

Things don't just happen. There's always an explanation. The only way I can explain what you are describing is if there was a significant resistance between the terminals. If that were the case then the connection you suggest would certainly solve the problem.

Edit: More correctly it would solve the problem of unequal charging. The diagonal connection allows for symmetrical charging, both batteries see the same charging path. But it doesn't address the resistance issue. Contrary to what many believe, resistance in a charging circuit does not cause voltage drops but rather controls the charging time. With the one battery connection, resistance between the first and second battery will produce a different charging time for each. Assuming the wires are properly sized, reducing corrosion would go along way to encourage optimum charging. Easy to do when only two batteries are involved. Not so much when you've got fifty to worry about.

[Gerry]

Cascading wouldn't be a factor in my case as the controller would charge each battery in turn. If I was to hook my batteries in parallel and I believe that I would do as said and charge as one huge battery with POS wire from charger onto one battery and NEG on post of other.

[Timber Wolf]

Originally Posted by rbryan

Not only costly, but way fewer amp hours than a pair of wet cell 6V GC2s. Going from 232Ah down to 100Ah? Not for me.

If what I see on their site is correct their "GC2 replacement" batteries are actually 12V. So, two of them at 12V and 100ah would be 200ah. Most of which should be continuously usable versus not wanting to go below say 50% on the wet cells (half 225 = 112.5ah). Anyway, I am usually not an early adopter of new technology, but this battery stuff is pretty interesting if it can get in the reasonable ($$$$) range. I am not in space vehicle mode where I throw NASA money at a problem to save space and ounces.

What I really, really want is a large flat battery. Make it the floor, or under the floor of a trailer. All the weight is down low and evenly distributed over the axle(s). Perfect! Except I hear lithium batteries sometimes spontaneously combust.

[floyd]

Originally Posted by Raz

There's always an explanation... it would solve the problem of unequal charging.

You got it!

[k0wtz]

I don't want batteries inside my trailer

bob

[Franswa]

I knew the cost was your objection (and mine at the moment)....I just threw that last comment as in: progress marches on...always

Gerry, because of the relatively large size of a 100W...I assumed you were permanently mounting on the trailer roof......one guy here some time ago had another take on your situation....he made a rack on the roof of his TV to carry the panel (with patch cord to trailer tonge)......if a place for the 100W inside your trailer is hard to come by you could go that route too.....and charge while on the road as well (I tend to move everyday so it is a consideration for me...might not be for you).....as I said before there are TONS of possibilities to fit just about every use/situation.....have fun, F