Old Charger - New Batteries - Shade Tree Mechanic

[LowGear]

I know there are many of you out there that can sneeze a better answer than I could calculate if given a couple of days of research on google.

I'm replacing six 6 Volt batteries with three 12 Batteries.  Both were and are in series to produce 36 volts.  The motor is a 53 Amp - 36 Volt unit.*

I have the original 36 volt charger that came with the golf car and hope to use it on the electrified upgraded Polaris ATV.  It's a Lester from Lincoln, Nebraska.  It puts out 36 Volts at 25 Amps via a timer.

The first set of R&D batteries are going to be Costco Deep Cycle Marine units or ?.  If testing is encouraging the second set will be Trojan 1275s.  $225 vs $630.

Should I be shopping for another charger?

Recommendations requested.

Comments are always welcome.

Casey

*  Yes I do know that I've reduced the mass of the batteries by around 50% even with the Trojans but I'm reducing the vehicle weight by even more and it won't have to go 2 or 3 miles between charges. 

[WStayton]

Casey;

  More info on the charger is required to make an intelligent recommendation.

  Do you have any idea what its out put curve looks like?  What Vdc does it actually charges at, etc., etc.

  The short answer is that, since it was supplied by the guys who made the cart, if it errs, it PROBABLY errs conservatively since burning-up/boiling-dry batteries isn't a good way to sell golf carts!

Regardz,

Wayne Stayton

[mike90045]

What was the amp spec on the old 6v batteries ??


I suspect that the 12V (100A) batteries will have less capacity than the 6V  (200A) and that your range will be reduced.

   Batteries should be charged at no more than 13% of their capacity - 100A battery, 13A charger, for longest life.

[Tom Reed]

A battery charger with a fixed timer does not sound to great for maintaining the batteries at full charge. A good 3 stage charger will get you the max range and better battery life.

[LowGear]

mike90045:

Thanks for that rule of thumb.  Its in my pocket.  I'll check the amp rating on the batteries and divide 10% of that into the 25 Amp output posted on the label.  Does this sound valid or at least safe?

Tom: 

Thanks for the input.  I'm cheap and this one is paid for.  If it doesn't work I'll be back for recommendations on a replacement 3 stage charger.  Are they expensive?

Casey

[LowGear]

So here I am.  Glazie eyed in front of the batter display at Costco.  12 Volt Deep Cycle Marine (would I dare use them if they weren't marine) $85 batteries.  750 Crank and 160 Reserve.  And now I'm looking at the Trojan site (T-1275s are about $250 here on the island) and get the attached spec sheet.

The electric motor is rated at 36 Volt - 53 Amp.  Total running an hour between charges would seem like a long days hard use at this time.  And these are all short <10 minute runs with at least that amount of time between rides. 

How much better are the Trojans than the Costco? 

How do the specs compare or do they?

Will the Costco batteries give me a fair indicator of what to expect from the machine?

Casey

[Thob]

160 reserve is the number of minutes the battery can supply a 25 amp load before going below 10.5 volts.   The Trojan T-1275 is rated at 280 minutes at 25 amps, so it has 1.75 x the capacity.  Note that the Trojan gives you more data, it is rated at 102 minutes at 56 amps.  This rating tells you that the Trojans will run your 53 amp motor for a little over 102 minutes.  As you draw more current, batteries become less efficient.  In other words, power is lost heating the battery at higher current loads, so you don't get a linear result.  These numbers, however, reflect using 100% of the capacity of the battery, which will quickly destroy the battery.  You'll get a lot longer life from the battery by only discharging 20-50% of it's capacity.  You'll also get longer life by charging it immediately after use.

The big difference in the batteries is how long they will last, which you can't really tell from the numbers.  The Costco battery is designed to sell at the cheapest price; the Trojan is designed to last many years in actual service.

Here's a page with some info:

http://www.marine-electronics.net/techarticle/battery_faq/b_faq.htm

I like the quote on the page - "only the rich can afford cheap batteries".

[LowGear]

Hi Thob,

Another readable website.  They are so scary.  This one and mike90045s http://www.smartgauge.co.uk/batt_con.html will make me be dangerous for the next six months.

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Does anyone know anything about the Trojan http://cgi.ebay.com/48v-48-Volt-Golf-Cart-Battery-Watering-System-precedent-/370534837421?pt=LH_DefaultDomain_0&hash=item564598ecad units.  This one is used at $99 and they're $200 new.  Whilst thou take the hour to pull the batters out and check their water every 45 days or so or whilst thou wait for a failure or severe loss of power as a maintenance protocol?  Rule three: don't rat yourself out - no matter!  But does anyone have experience with this system or other automated watering systems?

Casey

[Mad_Labs]

I have a very similar fork lift charger. If yours is like mine, there is a timer with two current settings. Using it one MUST be mindful, as it will overcharge the batteries. I think in many industrial situation they don't care as much about battery life as being ready to go in the morning. As to cheap batteries, I often have this feeling that a larger bank of cheaper batteries may last longer than a smaller bank of good batteries, as long as you have the ability to maintain the charge on the larger bank. I have no evidence to back that up. In any case, I think your idea of trying it out on some cheapies first is sound.

Jonathan

[LowGear]

Thanks Mad_Labs,

Cranky stuff like appropriate sprocket sizing and cable routing can be accomplished just as accurately with $85 batteries as can be done with $250.  You gotta love that Costco return program on batteries.  And then some stuff is more fun to build than operate.

Unfortunately I'm on The Dark Side, Seattle, for the next month so progress on Franky (short for Frankenstein) will be relegated to dreaming planning.

I'm negotiating with the battery auto-filler seller on Ebay.  http://www.ebay.com/itm/370534837421?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649  Do any of you have real world experience with such a system? 

Casey