Blowing up the 2720???

I keep the 2720 in an enclosed garage. Is there any danger of an explosion from hydrogen build-up from battery charging - it is plugged in to my 110 outlet? Based on past threads, I assumed that the charger will stop charging at some point. ps - battery is on front frame.

You would have to have a very small garage ( TM would not fit) to get enough concentration of Hydrogen gas to cause any problems. If you are keeping in an area where you have power and plan to keep it plugged in, I prefer the Deltran Battery Tender. It is designed specifically to charge batteries in storage. It monitors the battery and accurately controls the charge. I use them on my Harley Batteries when in the garage and had an original battery start the bike after 9 years.

Your TM should have a 3 stage charger/converter which will switch automatically to trickle when the battery is full. And if ultra cautious like I am, you could add an external timer to your wall plug and attach the TM shore power to it. I charge mine for 8 or so hours a week.

Rumbleweed,

If you have two 6 volt batteries on a TM, do you put the Deltran Battery Tender on one or both of them? or do you have to have 2 of the battery tenders? Does the Deltran Battery Tender work with 6 and 12 volts?

If you have two 6V batteries, they are connected in series. As long as the two batteries are the same size and age, I would connect to the plus side of one and the negative side of the other just as the TM power is connected. You can get 6V tenders, but then you would need two. I prefer these over the 3 stage as trickle charging over long periods of time is not as good as charge when it is needed. The battery Tender will cycle automatically.

Thanks Rumbleweed,

That makes perfect sense. I like the idea of only one 12V tender as it would also be more versatile in my case because I could also use it on my TV etc.

Be aware that max current is 1A so it really isn't a charger. It is specifically designed to maintain a battery. It is great on any vehicle or equipment that is not used much.

[Bill]

Originally Posted by rumbleweed

I prefer these over the 3 stage as trickle charging over long periods of time is not as good as charge when it is needed. The battery Tender will cycle automatically.

Actually, there is a bit of a semantic problem that should be addressed here.

A cheapo trickle charger, like the ones you buy from Harbor Freight or WalMart for $5, push a constant current through the battery, whether it needs it or not. This trickle current is usually on the order of 1 amp, which is too much for a fully charged battery. At this charge rate, the battery will overcharge and boil out the water - not very fast, but it will happen, and it is a bad thing. This is what has given "trickle charging" a bad name.

At the other end of the spectrum is a true 3-stage battery charger. The 3 stages are called "bulk" (a high initial charge current to restore most of the charge), "absorption" (in which the remainder of the charge is added), and "float", which maintains the fully-charged battery in a fully-charged state. In the float stage, its primary purpose is to replace the internal discharge (self discharge) current that is present in every battery. To do this, the charger monitors the battery voltage. When the voltage begins to drop due to self-discharge, the charger turns on a small charge current to make up for it. When the battery is back in a fully charged state, the charger reduces the charge current to a level below the self-discharge. Progressive Dynamics, for example, says the following about their chargers.

Q: Does my Converter/Charger completely shut-off when the battery reaches full charge?
A: When the battery reaches full charge, the charging current of the converter drops down to between 20 and 25 milliamps [20 milliamps = 20/1000th of an amp]. Batteries will self-discharge at this low rate even when no other 12-volt current loads are present. The converter senses this current loss and automatically replaces this lost current to maintain full battery charge.

This function is sometimes called "trickle charging", but I hate to call it that, for the reason noted above.

As described, all of today's Battery Tenders monitor the battery voltage, too, and provide charge current when needed. However, the Battery Tender (just like the Progressive Dynamics unit) does not turn the current all the way off - it leaves some small residual current to make up for self discharge. In other words, it does the same thing that the Progressive Dynamics chargers do in the 3rd stage. As Dave mentions, it doesn't have a hearty first- or second-stage, and that's OK - it doesn't pretend to. It is intended to maintain an already-fully-charged battery.

The Battery Tender web site covers most of this at http://batterytender.com/resources/float-charging.htm, though they don't cover self discharge very well.

So at the bottom line, I hesitate to use the term "trickle charger" for any of these. And it is good to recognize that a Battery Tender is simply the 3rd stage of a true 3-stage charger. They are the same thing. And neither one is a "trickle charger".

Sorry for the lecture. Don't know how else to say it.

Bill

[rickst29]

The only "high-end" feature which my 2619's WFCO converter/charger doesn't do is an occasional anti-sulfonation cycle. (That's a short period of very high voltage, applied to fully charge batteries, once every 18-24 hours). The WFCO is a well designed, fully functional 3-stage charger. I just leave our TM plugged in, 24x7, whenever we're not on a trip, and the results have been perfect.

Some ultra-high-end chargers do provide a genuine 4th operating mode for anti-sulfonation, and my WFCO doesn't have this. Progressive Dynamics may have been the first to offer it. They call their implementation the "charge wizard", and their name for the anti-sulfonization mode is "Equalizing Mode Operation". Their computer does it as a jump from the maintenance trickle charge voltage (13.2V) all the way up to 14.4 volts, their "bulk charge" voltage, for a period of 15 minutes every 21 hours. From what I read, and I read it pretty carefully, the Deltran does NOT do anything like this.

(Another quick note: these "smart" chargers are switching mode by changing the Voltage, not by trying to manage the amps. A "proper" maintenance mode voltage for fully charged lead-acid batteries is right around 13.2V, and the trickle amps end up being whatever the battery accepts when the charger applies that voltage. (Unless the battery has gone bad, it will be very, very small, as Bill showed in the quote from the Progressive Dynamics FAQ.)

Bill did a GREAT job of explaining 3-stage operation, and TM's own charger/converter is a true 3-stage system, with 3 different charging voltages. Deltran has some confusing market-speak about initialization as "4th stage", but they're only doing the initial "sniff" of battery voltage and voltage loss under slight load- this is not a 4th mode of charging behavior, it's merely deciding which of the 3 operating stages to start start from. Deltran apparently includes a thermometer-based voltage adjustment algorithm, which WFCO might not have. This could allow it to generate higher charging voltages in cool temperatures, leading to more amps and faster charging. But in storage mode, this doesn't matter, and in bulk-mode charging, the huge storage capacity of a TM battery set will probably try pull in more amps than the Deltran is capable of dishing out-- so the "temperature optimized" voltage probably falls back down, and the WFCO might end up charging just as fast anyway.

Bottom line: If you don't have other batteries which would benefit from Deltran-managed charge maintenance, then it looks to me like a waste of money. (Sorry, Bob, if I'm right. Please DO post right back if you know of something I've missed in labeling purchase of the Deltran as a "waste of money" if used only to replace the TM's onboard converter/charger.) The onboard TM converter looks just as good for maintenance mode trickle charging, and it's already paid for, and it's already nicely stowed away inside the TM. Just plug the TM into wall socket and forget about it. Leave it connected, continuously, until your next trip.

The other downside of the Deltran is it can only push 1.5 amps. That means that it would take approx 66 hrs to put back 100 amp hours into a 200 amp hour battery pack that is 50% discharged. If you read enough most of the information recommends that you should try to charge at a rate of C/10 which in this case would be a 20 amp charger. If I remember correctly the WFCO unit is 15 amps which is close enough. The Deltran is really only for motorcycles, lawn equipment etc... Or to keep a charged battery charged.