I'm planning on upgrading the old (loud, single-stage) converter in my '98 Coachmen class C to a PD 9200 series unit, and am trying to figure out what size to get. I'll probably be doing a little boondocking from time to time, mostly overnights rather than extended stays, so within reason faster charging would be a positive.The current house battery is a single 12V battery of uncertain provenance and capacity. I'm thinking I'll be replacing it with a pair of golf cart batteries which I think will fit in the tray, though I haven't yet pulled out the tape measure to verify. (It's inconveniently cold in Vermont to be mucking about with such things.)Is there any operational difficulty in having a multistage charger that's "too large" for the battery? Intuitively, I would not expect problems, since as I understand it they're basically acting as current-limited constant voltage supplies (albeit with various voltages for the various stages). The charge rate should therefore just be limited to what the battery will accept, correct?The obvious drawbacks are a higher initial cost for the converter and possibly for larger wiring to for the increased current capacity. I won't be limited by generator capacity.Currently, I'm leaning towards the 9270 (70A) model. The difference in cost between the 45A, 60A, and 70A models is comparatively nominal. Jumping up to higher capacities is more costly, and would also entail upgrading the AC circuit the converter is on (it's a 15A circuit presently) so I very likely won't go higher.Thoughts? Suggestions?

As I have pointed out many times, Hoover Dam can be connected and as long as voltage is controlled there is nothing to worry about.You do not boondock a lot and when you do it's not for long periods of time. The max charge acceptance of a group 24, 10-3/4" long battery is around 40-amps. Six cells of golf car allows 80+ ampere max charge rate. 50% acceptance for the GC220s would be 40+ amps.If you wish to power lots of hotel load plus charge batteries at max rate then the converter must be even larger capacity. A 60-80 amp unit. Most folks recharge batteries when hotel loads are low in daylight.Basic calculation reveals a 50-ampere converter to be of rational capacity. Most converters come up short voltage wise charging the final 10%. Your boondocking will be too short a time for this to be an issue. Hope this helps.

If T105s are in your future, Trojan recommends a 10 to 13% rate, so 23.2 to 30.12 amps should be the minimum amperage charger you get, assuming the converter will be powering no loads whilst charging in the Constant current/bulk mode.As Mex says you can certainly go bigger. I regularly hit my group 31 130 AH flooded battery with 41 amps. It can take a lot more than that when depleted. If you got an hour to run a generator to charge a depleted battery, do you want it to replace 30 amp hours or 60?Hint, it's 60.Also, Trojan recommends 14.8v Absorption voltage. PD only does 14.4v.Iota will do 14.8vPowermax will do 14.4v, but will do 14.6v if bought from bestconverter.com.Powermax also sells the adjustable voltage stageless converters. Nothing Automatic. You can hold Absv for a week if you desire( or forget), or boost voltage in to the mid 15's for an EQ cycle.Or set it to 13.2v when your batteries are charged or you have all the time in the world to recharge.These adjustables are nice as one can hold the battery manufacturer recommended absorption voltage for as long as required to max out Specific gravity, and hold it higher to get the most out of the time you have to run the generator.All the other Automatic 3/4 20 stage options are premature floaters, for fear of overcharging and greedy lawyers.

At best converter in the PD converter section it states that a 14.8 volt converter is coming soon. I would wait for that. 70 amps would be good. Make sure that the converter is mounted close to the batteries with proper wire size and you will be set.

The 3 PD 9200 series converters are different sizes. This may or not be important to you. The 9260 can be put in the same space as the Magnetek/Paralax converters while the others are bigger.The PD 4600 series is designed to replace the Magnetek/Paralax converters.

Converter size should be 30% of battery bank C/20 Amp hour capacityExample, 100 amp hours (C/20 rate) = 30 amp converter (so a 35 is what you would get cause,, Well, 35 you can get)Battery size Type and capacity chart (Recommend upgrade by the way)Type is "most common in RV use"Group 24 Marine Deep cycle 75Group 27 Marine deep cycle 95-100Group 29 Marine Deep cycle 100-105Group 30 marine Deep Cycle 130GC-2 (6V) DEEP CYCLE 210-230 amp hours (You use two in series, voltage goes up (12) Amp hours remain the same) This is the recommended upgrade to if they fit.A GC-2 fits a Group 24 tray but is tallerTotal your amp hours (IE: A pair of GC-2s would be perhaps 220, multiply by 0.3 and you get 66 amps. So a 60-70 amp converter is good.

Sizing a replacement converter | Good Sam Community

grizzzman
Explorer
Mar 03, 2015
At best converter in the PD converter section it states that a 14.8 volt converter is coming soon. I would wait for that. 70 amps would be good. Make sure that the converter is mounted close to the batteries with proper wire size and you will be set.
landyacht318
Explorer
Mar 03, 2015
If T105s are in your future, Trojan recommends a 10 to 13% rate, so 23.2 to 30.12 amps should be the minimum amperage charger you get, assuming the converter will be powering no loads whilst charging in the Constant current/bulk mode.

As Mex says you can certainly go bigger. I regularly hit my group 31 130 AH flooded battery with 41 amps. It can take a lot more than that when depleted.

If you got an hour to run a generator to charge a depleted battery, do you want it to replace 30 amp hours or 60?

Hint, it's 60.

Also, Trojan recommends 14.8v Absorption voltage. PD only does 14.4v.

Iota will do 14.8v

Powermax will do 14.4v, but will do 14.6v if bought from bestconverter.com.

Powermax also sells the adjustable voltage stageless converters. Nothing Automatic. You can hold Absv for a week if you desire( or forget), or boost voltage in to the mid 15's for an EQ cycle.

Or set it to 13.2v when your batteries are charged or you have all the time in the world to recharge.

These adjustables are nice as one can hold the battery manufacturer recommended absorption voltage for as long as required to max out Specific gravity, and hold it higher to get the most out of the time you have to run the generator.

All the other Automatic 3/4 20 stage options are premature floaters, for fear of overcharging and greedy lawyers.
MEXICOWANDERER
Explorer
Mar 03, 2015
As I have pointed out many times, Hoover Dam can be connected and as long as voltage is controlled there is nothing to worry about.

You do not boondock a lot and when you do it's not for long periods of time. The max charge acceptance of a group 24, 10-3/4" long battery is around 40-amps. Six cells of golf car allows 80+ ampere max charge rate. 50% acceptance for the GC220s would be 40+ amps.

If you wish to power lots of hotel load plus charge batteries at max rate then the converter must be even larger capacity. A 60-80 amp unit. Most folks recharge batteries when hotel loads are low in daylight.

Basic calculation reveals a 50-ampere converter to be of rational capacity. Most converters come up short voltage wise charging the final 10%. Your boondocking will be too short a time for this to be an issue. Hope this helps.

Forum Discussion

Sizing a replacement converter

About Technical Issues

Related Content

converter replacement

replacing converter?

Replacing Converter

Replacing converter

Converter Replacement