Mixing AGM and Lead Acid batteries

[donradcliffe]

What's mssing from your description is the amp-hr capacity of the AGM batteries. If you are connecting batteries in series, your bank capacity will be the least of the batteries.

[CSY Man]

. mssing from your description is the amp-hr capacity of the AGM batteries. If you are connecting batteries in series, your bank capacity will be the least of the batteries.

Damn, so sorry.
I thought I posted a picture of the data sticker for the AGM batteries.
Perhaps it did not stick.
Will go back and try again.

Edit: check the Nr. 12 posting, all the numbers should be there.

[btrayfors]

Originally Posted by CSY Man

.....

The problem with buying another wet golf cart battery is that a new one will burn out in 90 days as it accepts a charge much better than the old ones in the same bank.
Or so the experts told me......

Hogwash! Your so-called "experts" are blowing smoke! That makes no sense at all. So long as the correct charging VOLTAGES are maintained, no harm will come to the new battery and it will not "burn out in 90 days".

Think about it: an AGM golf cart battery -- used or not -- will accept a charge much faster than will your flooded golf cart batteries. That doesn't mean it will "burn out".

Of course the real answer is to stop messing around, forego a few dinners with the old lady, and fork out the $800 for eight new flooded golf cart batteries.

Were it me, I'd go for the Crown red-top CR-235. You can find them for about $100 each. They are made in the U.S. by a very experienced factory, and they are robust, industrial-strength batteries which should last you quite a while.

Bill

[CSY Man]

.

Of course the real answer is to stop messing around, forego a few dinners with the old lady, and fork out the $800 for new flooded golf cart batteries. Were it me, I'd go for the Crown red-top CR-235. You can find them for about $100 each and they are robust, industrial-strength batteries which should last you quite a while.

Bill

Easy to spend somebody else's money isn't it?

Old and new batteries charge at a different rate, not sure it is a good idea to mix 'em.
For now I will see how this combo works with used AGM batteries mixed with used Trojan T-105s.
Again, just buying time here and hate to throw away good batteries just because some guy on the internet said I should..

[osirissail]

Originally Posted by DefinitelyMe

Absolutely DO NOT open up AGM batteries to 'check the electrolyte level'. First off, if you have good ones they come with at least a 5-year, sometimes 10-year warranty. Tampering with them in such a fashion will void this warranty. Second, AGM batteries are pressurised in the factory. The contents are under pressure, and unscrewing or otherwise removing the caps will release this pressure with, at best, bad consequences (preventing re-combination of gaseous water during charging. The high pressure favours re-combination) and at worst blowing sulphuric acid all over the place and blinding you.

I don't know where you get your information from but the AGM batteries that I use are NOT pressurized and opening the valve access has no effect on the battery whatsoever. It is possible that your AGM's are different than mine but I doubt it as generally here in the USA the AGM's popularly sold these days are all made in China.

You can purchase top of the line batteries from USA vendors but the price differential is astronomical and what with - IMHO - cruisers tending towards "cheap" when buying stuff the "popularly" sold AGM's are more common and they are not pressurized - at least not mine. I have taken them apart (opened the valve cap) and been able to observe inside the battery and see the fiberglass sheets and plates and refilled the electrolyte. That has had the effect with my AGM's of extending the life from a couple / three years to almost a decade.

So "different strokes for different folks" as the saying goes. If the AGM was "over-volted" during charging because you did not use the best "intelligent" charging regulators, you would definitely end up with a "pressurized" battery - until the valve opened to dump the pressure. You would also end up with low electrolyte levels and warm or hot batteries.

Bottom line, AGM's generally have the ability to last longer (you get more cycles per battery) than ordinary lead acid batteries. But how you treat and take care of them can make the difference between getting those extra cycles or not. So whether AGM's are "cost efficient" is the subject of considerable debate. Investing in the equipment necessary to enable AGM's to last their maximum cycles can be expensive. Add those costs to the extra cost of the AGM itself and if you do the math, you will probably find out that you can buy several sets of old fashioned deep cycle liquid lead acid batteries for the cost of an AGM complete set-up. In fact, when I did the math I found that I could buy and replace the old style batteries over a time span almost double the best AGM advertised life-span.

So IMHO, AGM's only make sense when you are cruising in areas where you do not have access to reasonably priced replacement deep cycle liquid lead acid batteries. To each their own . . . .

[CSY Man]

Good info from everybody, thx.

Did a test run today and sadly, the AGMs are dragging the old fashioned lead acid batteries down.
Since I bought them used, without any warranty or history, I can't complain.
Took a chance and kind of lost.
Only $60.
The boat can still be used every day and the range right now is 1.5 hrs.
With fresh batteries, it should be 15 hrs, according to Duffy Boat anyways.
Cut that in half for a good 6-7 hrs at 4-5 knots.

If this was my sailboat and the house bank, I would not mess around with used stuff, always went first class and never had a problem and never had to call for help or a tow.
This little toy boat hovever is different, I'll run the batteries way down with safety and comfort still being maintained, all the way down to 1/2 he range.
Or I will check with Costco tomorrow, a smoking hot deal on 8 Golf Cart Batteries could be the ticket. Or next week...

[osirissail]

While roaming around the www for battery information I came upon this little website and some very interesting information on how to get optimum life/performance from battery banks consisting of multiple batteries.

In order to get the best and most uniform "drawdown" (for lack of a better word) of each battery the connections of the battery cables appears to have a significant effect. Wire them up in what "seems" to be a logical way to get your working voltage does not appear to be the best way to get the maximum available life from each battery in the bank.

So check this out - - - SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

P.S. as to availability of the different batteries on the market - worldwide - - I have found in the Caribbean that the Trojan T-105's are the most popular batteries and generally can be had "down-island" for somewhere in the neighborhood of $100 per battery. Not bad for a 225Ah battery although you need 2 of them to get 12 volts and for the OP's application on a Duffy Electric Boat many more. ** That Duffy E.Boat really looks nifty, see the photo attached.
http://www.duffyboats.com/boatimages...012_July_2.jpg

[CSY Man]

Well, I stopped messing around and bought 8 New batteries yesterday.
Deka, 230 amp hours. (Slightly more than the T-105s)
Got a good price at $73.95 each with the old batteries as trade-in.
Lots of work to install. Cleaned each cable terminal with a powered wire brush to make darn sure there would be a good connection. (A couple of the batteries had 6 terminals)
Took 6 hours total with clean-up.
Should be good now and will go for a test ride in 1/2 hr after having charged all night.
Costco's Interstate Batteries was $84 plus $15 if you did not have the old ones for trade-in.
Used Dekas in the past for house and start batteries on my CSY 33 sailboat.
Got 5 years on the first set and 6 years on the next. Good batteries for sure.
The old Trojans on this boat was 3.5 to 4 years old and they could have been abused before I got the boat, not sure.

[osirissail]

Seems I always have more suggestions - do what you want it them. - -
Since you spent some significant time cleaning the terminal posts to make sure you will have a very good connection - there is one additional step I do to help keep the terminals clean in the salt water laden air. And that is get a bottle of liquid electrical tape from West Marine or Home Depot or someplace similar. Then after everything is connected paint the battery connectors and terminal posts with the liquid electrical tape. The stuff is basically a black or white liquid rubber-tar like paint that will cover over everything and keep the corrosion away (the white powder that accumulates around the battery terminals). Goop is on over and under the connections to keep air and fumes away from the terminals. It will dry and should you need to disconnect the terminals use a pen knife or razor knife to split open the liquid electrical tape and the terminal is easily removed.

[CSY Man]

Aye Osiri:

Good idea, but too late.
I already covered the terminals and connectors with petroleum jelly to keep corrosion and moisture away.
Shoukd be good to go for the next 5 years.
Hopefully.