24v Coach float?

[Buffalo SpaceShip]

In a recent thread, there was some mention of 24v float charging for house and coach systems. Since my house system is 12v and totally separated (12v alt, 12v inverter/ charger), I need to maintain my new coach 8Ds this winter. And for the first winter since getting into bussing, I can keep the bus plugged in... and keep those 150# beasts in the bus.

Anyways, I need to purchase a little automatic charger/ maintainer for the coach side. I went to batterystuff.com and see a bunch of 24v chargers. Some are made for 12v batts in series (like mine), that can charge each batt separately. Or I could use a single-lead 24v charger that floats at 28v or so. Any pros/cons for these two distinct methods? I figure my coach alt. puts out a 24v nominal voltage that the batts use to charge themselves at 12v nominal. So floating batts this way seems OK in my mind... but I'm no expert. Here's a charger I'm looking at.

I could also move the cables to parallel them and just charge the set with a 12v charger... but would rather leave the batts "good to go". Imagine forgetting to switch 'em back and trying to start the coach on 12v. 

I could also pony up for a Vanner equalizer and use a 12v charger on it's leads... but probably won't do that right now. Eventually, I'd like to buy a mongo 24v inverter and use the coach alt. in parallel to charge house and coach side... but not anytime soon.

Any thoughts? Thanks,
Brian B.

[Lee Bradley]

I just bought a battery charger from this company. Very fast service.

I got this one http://www.batterystuff.com/battery-chargers/24-volt/5-9amps/CT-500-1.html

I wanted to maintain the batteries as seperate batteries so if one battery went bad it wouldn't effect the charging of the other battery.

[DavidInWilmNC]

Brian, I use Battery Tenders on my motorcycles, jet ski batteries, and rotate it around to all my other 'spare' batteries.  Here's one you might be interested in http://batterytender.com/default.php?cPath=11_4&osCsid=0e11888c931ecf78de3cc20995365ecd.  You can get a waterproof 12V / 5 amp (for each bettery) or a 24V / 2.5 amp model to cover them both.  I have a couple of these http://batterytender.com/product_info.php?products_id=4&osCsid=0e11888c931ecf78de3cc20995365ecd that I use around the house.  I'm thinking another two for the 8D starting batteries would take care of them.  Good luck and let us know what you decide to do.

David

[DrivingMissLazy]

Brian, I do not know why you think you have to keep them hooked up to a charger continuously. If the batteries are good they can sit several weeks, or months, with out any adverse effect. A few hours charge every month should be more than adequate and might be better for the batteries than the wrong charger hooked up continuously.
Richard

[Buffalo SpaceShip]

Fair enough, Richard. I was under the impression that starting batts will self-discharge about 8-10% per month. And I keep the house bank on float all the time, so I didn't see the harm in keeping the coach side "tended".

But I'll still need a 24v charger, though, unless I charge each batt separately, eh?

bb

[DrivingMissLazy]

That 8-10% per month is BS put out by one of the members of the board. I have never has a battery discharge even close to that amount unless there is a phantom load on it.

Be careful of keeping a charger on full time. Many of them will ruin a battery over time. and you can use two 12 volt chargers at the same time to charge your 24 volt system.
Richard

Fair enough, Richard. I was under the impression that starting batts will self-discharge about 8-10% per month. And I keep the house bank on float all the time, so I didn't see the harm in keeping the coach side "tended".

But I'll still need a 24v charger, though, unless I charge each batt separately, eh?

bb

[Lee Bradley]

This is what I saw published by a battery manufacturer:

A 3/4 charged battery is in no danger of freezing. Therefore, batteries should be kept at least 3/4 charged, especially during winter weather. The frequency of checking batteries depends greatly on temperature. The effect of temperature on self discharge for the average fully charged, new, conventional battery in good condition is approximately as follows:


At 100° F (37.8°C) .0025 Sp.Gr. per day
At 80° F (26.7°C) .001 Sp.Gr. per day
At 50° F (10°C) .0003 SG per day
A fully charged battery stored at 80° F (26.7°C) will take 30 days before it self discharges 25 percent. At 50°F (10°C) the time period increases to 100 days. This will give you an idea of how often a battery should be checked.

Some makes of batteries will have a higher and some a lower rate of self discharge. This depends on the method of manufacture and purity of materials used.

[82 MCI-9]

I just purchased the same charger that Lee Bradley just got. I just mounted it to the side wall of the battery compartment and plugged it in so far it works great no problems.