How much converter/charger is really needed?

[Bobbo]

I have a pair of NAPA 9824M Marine/RV batteries with a 20 hr rating of 79AH each, wired in parallel.

Is there, really, any advantage in going from a 45 amp (PD4645V) converter/charger to a 55 amp (PD4655V) converter/charger?

I know that bigger is ALWAYS better, and the cost is not much more, but, really, is there a real advantage?

If not, how many AH do you need to make the jump from 45 amps to 55 amps useful?

[MEXICOWANDERER]

Let me use another analogy...

"Spending eight dollars in fuel to drive across town to save four dollars because of lower pump price".

Rather than -argue- a point I pen examples.

When I argued a point that spending a hundred dollars in generator fuel to save eight dollars in battery lifetime gain was foolish no one seemed to "get it"

What seems to be the difficulty in understanding this. So and so manufacturing recommends... Of course they do. Reducing battery charge rate WHEN ON PUBLIC POWER does improve battery life. But the cost of generator and fuel does nor enter into the calculation according to the manufacturer. They want to make their batteries look as good as possible.

If a battery is charged at a rate that does not increase temperature as measured at the battery terminals then the rate is not excessive. For example

With BFL13's AGM batteries, he keeps mentioning that the manufacturer recommends some stated amperage maximum. He misses the point. Apply 14.4 volts charge rate right off the bat. If the batteries accept 45 amps, if they accept 145 amps without heating then this "MAXIMUM ABSORBSION ACCEPTANCE RATE" will save generator run time WEAR OUT and FUEL COSTS like crazy. i.e. it would be foolish to adhere to battery manufacturer recommendations. They "ASSUME" battery replenishment would be via public power. Generator charging is thirty times or more costlier than public power.

I written this thirty times on this forum recommending to IGNORE UTTERLY manufacturer's public power recommendations for maximum charge rate if you would take the time and measure battery post temperature. Do it with your finger. If the post becomes warm on a mild day, reduce charge rate. But never exceed VOLTAGE charge limits. Should I encounter a poster who says "I have chosen to" then that's a different story.

[pianotuna]

Bobbo,


What Mex is saying is that if you have shore power for charging, converter size doesn't matter much. If, on the other hand, a generator is being run, a device capable of high amperage charging is of benefit, and worth an upgrade.

Bobbo wrote:

OP here. When I am able to understand Mex's posts, I learn a lot. When, like this one, I don't have a clue what he is saying, I just go on and don't worry about it.

[Bobbo]

Cydog15 wrote:

MEXICOWANDERER wrote:
It all depends on the cost to recharge them

"I had my car detailed once a week for ten years. Look, the paint looks like new!"

$35.00 x 52 x 10. $18,500

Yes an exaggeration. But far less so when using gasoline than receiving a power bill. Start with the cost of a generator, then maintenance, then the cost of driving to go get fuel.

Black and White suddenly turns into various shades of gray.

When responding to somebody trying to learn something do you always respond like this for your peers or do you have any interest in the guys and gals wanting to learn? Seems to me nobody is allowed to learn anything in the tech forums. You will surly be told how stupid you are though. Never told how to get the basics.

OP here. When I am able to understand Mex's posts, I learn a lot. When, like this one, I don't have a clue what he is saying, I just go on and don't worry about it.

[Cydog15]

MEXICOWANDERER wrote:
It all depends on the cost to recharge them

"I had my car detailed once a week for ten years. Look, the paint looks like new!"

$35.00 x 52 x 10. $18,500

Yes an exaggeration. But far less so when using gasoline than receiving a power bill. Start with the cost of a generator, then maintenance, then the cost of driving to go get fuel.

Black and White suddenly turns into various shades of gray.

When responding to somebody trying to learn something do you always respond like this for your peers or do you have any interest in the guys and gals wanting to learn? Seems to me nobody is allowed to learn anything in the tech forums. You will surly be told how stupid you are though. Never told how to get the basics.

[MEXICOWANDERER]

It all depends on the cost to recharge them

"I had my car detailed once a week for ten years. Look, the paint looks like new!"

$35.00 x 52 x 10. $18,500

Yes an exaggeration. But far less so when using gasoline than receiving a power bill. Start with the cost of a generator, then maintenance, then the cost of driving to go get fuel.

Black and White suddenly turns into various shades of gray.

[wa8yxm]

I will add.. Even if you upgrade the batteries (Which I'd do on a replacement basis by the way. No need to pull good batteries out) UPGRADING the converter (and the wires to/from the batteires and the fuse or circuit breaker) only makes sense if you boondock and re-charge off Generator a lot. and then only if the Genny has the OOMPH..

Now earlier I quoted Xantrex
This is from Trojan (Battery folks) they suggest a 10% C/20 rate for longest battery life.

SO where as my OEM Interstates lasted 9 years.. Had I had a smaller converter they may have gone 10 or 11.. I'd not upgrade less you need it.

ALternative.. The original setup here I had and 80 anp converter (bit big for a pair of GC-2) and a 100 amp inverter/charger (2000 watts A/C or 100 amps DC) I upgraded the bank and when on shore power I used the converter ... Still do. but when boondocking used the 100 amp charger in the inverter for less Generator time. (I have over 500 amp hours of battery).

Worked great.. Till the inverter crapped at about 13 years of age. Now I have an 80 anp inverter/charger.

[Bobbo]

Thanks everybody. This is what I needed. I won't waste the effort to pull the 45 amp unit out. At least, not until (or unless) I change to a pair of GC2 6v jars.

[wa8yxm]

Ok this is from teh manual for my Prosine 2.0 Inverter/Charger

Maximum charge rate should be no more than 30% of the C/20 amp hour capacity. YOu said that your batteries are 79AH each (Group 24?) or 158 AH total

So 0.3 (30%) times 158 = 47.4 The 45 amnp is the proper converter. Bigger has no advantage save to the battery salesman.

NOW if you swapped those out for a pair of GC-2 in series. 220 anp hour give or take .3 times 220 = .66 So you could go up to 60 amps if you upgraded the wires.

[Matt_Colie]

Bobbo,

There is a lot that has been posted here and I am going to throw out another piece.

If you do not have a real battery monitor, don't do anything expensive. Now matter what you have available and far a charging, if the system won't handle it, it is a waste. So, look them up and install a Bogart or Victronic or other that can really tell you what is going on. These pretty much are essential to maintain a solar system anyway.

Very many times (too numerous to identify) I have found systems that did not have the cable to support the charging current that an owner had installed. Then, they call me because it does not do what they had hoped.

So, before you install more line charging capability, install a real monitor and see what it is capable of right now. You may need to add copper just to make what you have work as intended.

I did a whole lot of this stuff for sailors with performance cruisers (read retired race boats). Now that they wanted to be comfortable, the first thing that they wanted were better electrics.

Matt

[Cydog15]

Bobbo wrote:
Let me give you a little background. I ordered a PD4655V converter/charger. When it came, I installed it. I have been fat dumb and happy for the last 18 months with it. After 18 months, I found the box and discovered that when I bought it, they accidentally shipped a PD4645V by mistake. I am wondering if it is worth my while to pull out the 45 amp unit and install a 55 amp unit. One day, when these batteries die, I may go with a pair of GC2 6v units, or a pair of group 31 AGM batteries, but that will be years down the line as the batteries I have now were brand new when I installed the converter.

We do boondock a lot, and I have a 2000 watt Honda. I also currently have a single 80 watt solar panel on the roof, and am seriously considering adding 2 more of the 80 watt panels. That project is very likely to happen.

I agree there is not reason changing it out. If anything, I don't think there is measurable difference. As for your batteries, when it comes time and assuming you are going to stay AGM, Full River makes the 6 volt 220 AH in a group 27 case. There is something to be said for that. More people can get 6 volt that were limited by compartment size with the GC2. Smartest thing Fullriver ever did.

[BFL13]

I am sure Wets can take as many amps as they will "naturally" and not any more, so no harm done. But my 100AH AGMs specify a charging limit of "about 27 amps" and my 250AH AGM says no more than 100 amps.

So I am wondering if there is a difference there, and we should be careful what kind of batteries we are talking about.

[pianotuna]

At around 85% state of charge the most a 100 amp-hour battery can accept is about 12.5 amps. If voltage is increased, all that happens is gassing and heat.

[time2roll]

I would not hassle making the swap.

[BFL13]

Based on the furnace post, the batteries are already nearly dead.

"Fat dumb and happy" is equal to, "If it ain't broke don't fix it"

[Bobbo]

Let me give you a little background. I ordered a PD4655V converter/charger. When it came, I installed it. I have been fat dumb and happy for the last 18 months with it. After 18 months, I found the box and discovered that when I bought it, they accidentally shipped a PD4645V by mistake. I am wondering if it is worth my while to pull out the 45 amp unit and install a 55 amp unit. One day, when these batteries die, I may go with a pair of GC2 6v units, or a pair of group 31 AGM batteries, but that will be years down the line as the batteries I have now were brand new when I installed the converter.

We do boondock a lot, and I have a 2000 watt Honda. I also currently have a single 80 watt solar panel on the roof, and am seriously considering adding 2 more of the 80 watt panels. That project is very likely to happen.