What size converter charger should I get?

[tasslehawf]

Our vintage travel trailer doesn't currently have one, but it came with a marine battery that's rated at 85 Amp/hours. The smallest converter chargers I'm seeing are 35 amp. Is this small enough?

[harold1946]

Sam Spade wrote:

harold1946 wrote:

Mrkoje asked you for a link supporting what you stated, where is it ???

I=E/R That's my link.

How many people fuse their battery banks ????

Thought so; If one makes statements that can not be supported, accept by precision guesswork then it does not exist.

Don't have a clue, but the ones that are aware of what a catastrophic failure can do will add one if the coach builder did not.
I would make a wild guess that most are not many even aware what one does or where it should be located.


bighatnohorse had a failure earlier this month and it blew off the top of a single battery in a string of two. No other damage was done, not even to the second battery in the string.

A fuse is much cheaper than replacing anything that could be damaged.
The monies, RV or life you save may be your own.

The old adage still hold true, (ignorance is bliss) have a blissful day.

[Sam_Spade]

harold1946 wrote:

Mrkoje asked you for a link supporting what you stated, where is it ???

I=E/R That's my link.

How many people fuse their battery banks ????

[harold1946]

If the battery bank is properly protected with the correct catastrophic fuse it goes nowhere.
Mrkoje asked you for a link supporting what you stated, where is it ???

[Sam_Spade]

harold1946 wrote:

Batteries connected in parallel are no more susceptible to thermal runaway than those connected in series or series/parallel.

Really ??
Pray tell where does the current GO when you suddenly have a healthy 12 V source capable of delivering say 300 amps is connected in parallel to one with a couple of shorted cells producing only 8 volts and maybe 200 amps ?? 100 amps will go somewhere. Where will it go ?????

If connected in series.....NOTHING HAPPENS except your power supply is weak.

If connected in parallel, way MORE than nothing happens.

Discussions like this just proves the adage about everybody having an opinion......and most of them stink.

[MEXICOWANDERER]

OP? Are you there?

[harold1946]

red31 wrote:
mrkoje

they pull numbers out the sky and when question say ' shut up ', the nature of forums. This thread has nothing to do with parallel or 12v vs 6v, but it pokes its ugly head out!

will have to wait for the links you requested 😉

Don't look for any links supporting any of it. There are none.
Batteries connected in parallel are no more susceptible to thermal runaway than those connected in series or series/parallel. 12 volt batteries are no more susceptible than 6 volt.
Deep cycle batteries are available all across the US in both 6 and 12 volt.
I would also like to see any credible link stating that 6 volt batteries are superior to 12 volt.

PS: Those interested in learning more about the care and feeding of batteries, I suggest reading "The 12 volt side of life" parts 1&2. For more technical information go to www.batteryuniversity.com
A wealth of knowledge is available.

[red31]

mrkoje

they pull numbers out the sky and when question say ' shut up ', the nature of forums. This thread has nothing to do with parallel or 12v vs 6v, but it pokes its ugly head out!

will have to wait for the links you requested 😉

[Sam_Spade]

mrkoje wrote:
So again - please let the 1000s of RVers know how they are setting themselves up for disaster!

To the OP - I am sorry for the thread hi-jack. I know that your original question has been answered already.

If you are really sorry you will just STOP.

Nobody claimed there would be a disaster.....unless a cell in one completely shorts out which is rather rare.

The fact is that you won't quite get the capacity that you might expect. Other than that, and the tiny chance of a short, there is nothing wrong with doing it.

Two 6's in series is better because:
Deep cycle 6's with higher capacity are easier to find, generally last longer and won't cause a disaster if one or two cells shorts out. That's it.

The original "sky is falling" wording was a bit off base but your response likewise could have been more factual and less argumentative.

Chill please.

[mrkoje]

Sam Spade wrote:

mrkoje wrote:
So then wouldn't 4 6vs in a series parallel suffer the same fate?

Yes very likely.
I suspect it would take longer and not be as pronounced but that is just a guess.

So then when the other member Matt stated:

Matt_Colie wrote:
Please do not parallel 12V jars. Even if they were side by side on the assembly line, by the end of the third week, they will not like playing in parallel. If you are lucky, you end up with capacity * 1.7. It will more likely be 1.5.

And you stated:

Sam Spade wrote:
If the two are not perfectly matched, part of the capacity of the stronger one will be expended trying to charge the weaker one. And when charging, the weaker one will sap off more of the charge.
And if one should fail completely, disaster can occur.

The disaster is rare and I think his 1.7 estimate is closer until they get really old but 6 Volts in series really are better.

So then wouldn't by your own account also need to say the same for having 4 6v batteries in a series parallel? In fact then wouldn't you also have to recommend not connecting 6v together in such a manner or end up with a 1.5-1.7x capacity or in the disaster that you mentioned?

Fact is hundreds if not thousands of RVers connect their 2+ 12v deep cycle batteries in parallel. There are also quite a few RVers that have multiple batteries 4+ in the battery banks that connect either with parallel or series or a combination of both depending on their configuration.

My question from the start was for Matt to explain why he said "Please do not parallel 12v jars .. they will not like playing with each other .. etc .."

To be clear - It is not advised to connect any batteries together when they are not identical types/ages etc. We're not talking about connecting a 12v grp24 with a 27 or 1 12v with 2 6v. Same battery next to each other on the assembly line as Matt said.

I have not found one spec sheet from any manufacturer to suggest that it would be ill advised to do so. So again - please let the 1000s of RVers know how they are setting themselves up for disaster!

To the OP - I am sorry for the thread hi-jack. I know that your original question has been answered already.

[red31]

ain't solar float great!

[Sam_Spade]

smkettner wrote:
and then let them sit disconnected on the concrete for a week.

Why do you mention concrete ?

We aren't doing to have that "concrete discharges batteries" discussion are we.....please not.

[Sam_Spade]

mrkoje wrote:
So then wouldn't 4 6vs in a series parallel suffer the same fate?

Yes very likely.
I suspect it would take longer and not be as pronounced but that is just a guess.

[time2roll]

Sam Spade wrote:
If the two produce different voltages, they will be "fighting" each other.

There is no fight. The battery that has a higher resting voltage simply discharges to the level of the other and then they just sit peacefully.

Go ahead and equalize two identical batteries (that have been used in parallel) at the same time and then let them sit disconnected on the concrete for a week. Measure the resting voltages to quantify the difference. Post your results.

For the OP: 35 amp is fine for 1 to 4 batteries.

[mrkoje]

So then wouldn't 4 6vs in a series parallel suffer the same fate?