Converter Questions

[JDHarrin]

Just swapped out two NAPA Size 27 FLA house batteries for two Duracell 31 AGM batteries. We already see a dramatic difference in the batteries in the RV - the lights are much brighter, etc. Now I'd like to upgrade the converter and I'm looking at the Power Max multi-stage systems. A couple questions. These come in a multitude of amperages - 15, 35, 45, 55, 60, 75, 85, 100, 120 Amps. My two new batteries are rated at 210 amps. What criteria do you use to chose which converter to buy? In all the videos I've watched, they've been in the 45-60 amp range. Second, what's the difference between the PM3 and PM4 series converters? I don't see anything on their website that compares the two. Anyone have any background on this hardware?


JD

[tinglett]

Did you make a decision of which way you are going? I've got a similar situation with a couple LiFePO4 batteries and have ordered a Power Dynamics (not PM) charger to replace my WFCO. I'll start a thread on that when the stuff arrives.

[Bobn1957]

The amperage of the converter correlates to the charging current and the total house load with the lights, fans and pump on. That said upgrading to a multi-stage charger is a good idea.

[al1florida]

A 45-55 amp charger is what you should use. That provides a max charging current of about 25% of the total AH capacity of your battery bank.

[al1florida]

I believe the PM3 and PM4 refer to the number of charging steps.

The three main charging steps are: Bulk, Absorb and Float. The fourth would be the equalize mode used to help de-sulfate the battery plates for longer battery life.

I was not able to locate a manual for the chargers to verify the above info.

[al1florida]

BTW, if you are going to dry camp for more than overnight or just for a couple of days and then back on shore power you must have a good battery monitor such as the Trimetric or Victron.

Best Battery Monitors for RV's, boats,off-grid cabins, vanlife

https://www.victronenergy.com/batter.../bmv-712-smart

Without the battery monitor you are flying blind on just how far you have discharged your batteries and how close to full you have gotten the batteries when charging. If you take your batteries down to 50%-60% full it takes many more than just an hour our so of charging to get them to 100% full. If you run your batteries down below 50% full you greatly shorten the battery life. Just using a voltage check to see the state of charge is just an approximation and can be quite a ways off of the actual SOC.

[tinglett]

Originally Posted by al1florida

Without the battery monitor you are flying blind

I can't agree more! While my wife and I are still "noobs" at this, we've found it very, very difficult to have a clue where we were at without a monitor. What a night and day change to have one!

I started with a cheapo $20 bayrite, but it's difficult to use as you only learn how much power (in watt-hours) you use. You can't track both charging with discharging easily, and tracking the battery's remaining capacity is even more difficult as you have to accommodate inefficiencies rather than do a simple subtraction. I eventually got a Victron BMV-712 and my is it nice to have! There is a bluetooth-only variant if you don't want to try to install anything into a control panel.