Inverter Generator and 12v deep cycle batts

[reckfield]

I have an 89 Alpenlite trailer that has the original converter. I have two group 27 deep cycle batteries connected in parallel that I use in the trailer. I would like to know how best to charge the batteries while boon docking? I could hook the inverter gen to the shore line power cable. But, I'm thinking I would be much better off to connect a 25amp charger directly to the two batteries in the trailer, leaving the battery connections to the trailer in place or should I disconnect those while charging with the 25amp? From what I have read, the converter will never get the batteries up to charge as the converter will go into maintainance mode around 12.5 or less if using the shore line to the converter with the inverter gen. Thank for your help.

[time2roll]

reckfield wrote:
The existing Converter is a MagneTek model Tu-740-2 with AC input of 7.3 amps and DC output of 40 amps.

If you are inclined to replace it I recommend a PD9245.

You will need to check your wiring size to the battery to go bigger and the batteries are not going to charge much faster anyway by going 60 or 80 amps.

[rvsatek]

You converter/charger from 89 vintage rig were not very good chargers. For example: If you had 40 amp converter from 89 it will provide you rig with 40 amps of power but will only charge at 6 or 7 amps at best. So yes an external charger would be best.

[MrWizard]

moved from technology corner

[wa8yxm]

The answer depends on many factors.
1 What converter is in teh RV? Magnetek 6300 UPGRADE Progressive Dynamics 9245 Well... Other than perhapd a biggert unit (IE 9260 which woudl be the proper MAX size for those batteries) there is no upgrade.

(60 amps is about your maximum recommnded bulk charge, however for most Lead Acid battery type a SLOWER charge is better (longer overall lire).

Many other make and models are also very good... So if you have a good 3-Stage charger in the RV.. That is the best way to charge.

Alsok if you replace thse Group 27's (next time they need replacement)( with a pair of GC-2 in series you get about 20% more total capacity and over twice the useable capacity and quite possibly longer battery life.

[reckfield]

The existing Converter is a MagneTek model Tu-740-2 with AC input of 7.3 amps and DC output of 40 amps.

[valhalla360]

You are confusing two different things.
- The amp rating is the maximum each can put into the battery bank. The larger one will put more into the bank.
- As lead acid batteries approach 80-90% charge, they will accept less charge, so modern smart chargers dial back the amps they are trying to dump in. Trying for force more amps in won't gain you anything and can cause problems.

Built-in or stand-alone doesn't matter.

Better chargers will use multiple stages that also vary the voltage based on battery needs.

[Lwiddis]

“I would like to know how best to charge the batteries while boon docking?”

Think outside the box. Think something new. Think solar.

[time2roll]

If you have a 25 amp charger you should plan to use it. Put it right on, no need to disconnect.
If spending money I recommend you should upgrade the on-board converter.
Post the existing converter model for best answers.

[MrWizard]

me i say use both
plug in the shore cord
and an extension cord for the battery charger
use both, and while you are at it you will have 110v for the TT duplex outlets for charging cellphones etc..

[theoldwizard1]

If you are confident that the charger built into your converter is doing a good job charging your batteries, then continue to just plug the generator into the shore power outlet.

If that is the original converter, I suggest you upgrade it to a modern one that has "smart" battery charging.

[Bill_Satellite]

What amp rating does your current converter have? I would suspect it it much higher than the 25 amp charger you are considering connecting but I am wrong.....a lot!

[old_guy]

I use a charger with my batteries and they get up to full charge faster than the TT electrical cord