Plugged into 15amp for storage

[jeffem62]

Almost a little scared to ask due to being told to read the manual. Here goes, we have had the 2021 Dynamax Force 34KD for about 7 days now. Read the manual but can not find anything definitive. When plugged into shore power is it charging my Chassis Batteries (Start Batteries)? Or should I buy a Battery Tender?

 

[Twinboat]

Buy a cheap mult-tester and then you can find out if yours does, most newer models do.

Lug it in, wait a half hour and measure the voltage at the batteries. Anything over 13 volts means it's charging.

 

[chrisski]

If it charges on 30 amp or 50 amp, it will charge on 15 amp.

I’ve measured converts at 90- 150 watts depending on how much charging they do. A typical RC converter will charge at 10 amps, about 140 watts max, well within a a 15 amp plugs limit of 1400 watts constant.

 

[jjscsix]

Almost anything with a converter charges the battery. I guess I cant 100% guarantee yours does, but feel pretty certain it does.

 

[KyDan]

Almost anything with a converter charges the battery. I guess I cant 100% guarantee yours does, but feel pretty certain it does.

Just a note for clarification- He's asking about a Dynamax and specifically
asking about whether the engine cranking battery is charged when plugged
into shore power- or in this case 15 Amp shore power.
I would think the house batteries would be charged for sure but the
engine battery??
This is a very make model specific question.

 

[Aussieguy]

your house battery should get charged by the converter
as others mentioned measure voltage with a meter
at rest (no charging for 20minutes) ... 12.8
while charging 13.6v

starting battery do the same voltage measurement
let the house battery get fully charged and then test the starter battery
IF in doubt... attach a small battery maintainer to the starter battery ... get power from one of the RV 120v outlets .

 

[Mike134]

Just a note for clarification- He's asking about a Dynamax and specifically
asking about whether the engine cranking battery is charged when plugged
into shore power- or in this case 15 Amp shore power.
I would think the house batteries would be charged for sure but the
engine battery??
This is a very make model specific question.

Most likely NO! Think about it power can flow both ways, if the shore power could charge the cranking battery, then boondocking with no power would drain the cranking battery.

 

[bclemens]

The Correct Answer is "YES", with an asterisk.

ALL motorhomes will typically have a device that pairs the house and chassis batteries when needed.

Reading the owners manual is a bit generic. The better tools, are the component manuals located here. https://forestriverinc.help/#/dynamaxrv/guide/2021/1372-force/browse/component-manuals

Under Electrical, you will find the "Battery isolation manager". That manuals explains what is going on. https://forestriverinc.help/#/dynam.../content/publication-16-en_us-multiple-709236

Now, having said that, 15A outlet is NOT that much power. If you have everything shut off (breakers), then it is enough to charge the batteries. if you are trying to run the fridge and/or A/C, probably not enough. If you have Firefly multiplex, you can use the touchscreen to alter the incoming power and it will balance some of that for you based on the total power, or you can adjust the charging % so the charger is taking all of the juice.

 

[Aussieguy]

yet some battery managers in motorhomes will allow charging the starter from shorepower


adding a small maintenance charger from the 120v to starter battery can be done if you are going to store the RV for a long period

short periods... couple of weeks
Fully charge all batteries before storing and then disconnect all the batteries (disconnect each negative)
lead acid self discharge is about 5% so it will take about 10-20 weeks to drain the battery

study what YOUR battery requires for storage

 

[Chuck_S]

Simply disconnecting the batteries will prevent deep discharges. Disconnecting as in pulling (or switching) the Negative cable.

But it's easy to find out if the starting battery is being charged by the converter:

Ignition off.
Camper plugged into shore power.
Let it sit week and then measure the starting battery voltage while still connected -- the one under the hood. If it's in the 13v+ range it's being charged by the camper. Conversely if it's below 12.6v it isn't. That $6 multimeter you sometimes get for free at Harbor Freight is all the technology you need.

I use an inexpensive battery tender on my Summer car while she sits in the garage waiting out winter weather. Motor vehicles have parasitic power draws for things like the alarms and radios. My camper and boats come out of hibernation at roughly 50% charged level just by switching the battery completely off. Camper battery switches leave things like the propane detector permanently wired by code so these devices remain hot unless you pull the negative cable.

-- Chuck

 

[KyDan]

Most likely NO! Think about it power can flow both ways, if the shore power could charge the cranking battery, then boondocking with no power would drain the cranking battery.

Not if there is a battery isolator (diode) in there.

 

[Chuck_S]

A $100,000+ motor home should have have a battery isolator. $100 if you don't have one.

Something less exotic like a Off-1-Both-2 battery switch will work too. Maybe $50 for this but you gotta manually switch it.

-- Chuck

 

[jjscsix]

Just a note for clarification- He's asking about a Dynamax and specifically
asking about whether the engine cranking battery is charged when plugged
into shore power- or in this case 15 Amp shore power.
I would think the house batteries would be charged for sure but the
engine battery??
This is a very make model specific question.

My bad. I HATE when that happens

 

[jeffem62]

Thanks for all the reply’s everyone. I stored it today for the next three weeks. I turned off the switch next to the drivers seat and plugged in the 15 amp shore power. Will test batts when i get back. On the display it did flash it was charging just does not specify what. I don’t have a firefly. Maybe for the winter months I think a battery tender also just to be safe.

 

[vlamgat]

And remember, its quite possible that even if you power down all the devices, and switch off all the power with the provided switches, your I/C will still pull power from the batteries directly and that will flatten them in 2 weeks, maximum. So disconnect the +ve lead from your inverter to get to a zero discharge.

 

[Rob0702]

15 Amp Storage

Replying to jeffem62 - I got tired of using an electric cord to plug into 15 amp when unit is stored. Plus, it kept tripping the GFCI in the garage. So I invested in a 20 amp solar panel trickle charger that sits on the ground, and keeps the battery maintained when you're not using your rig. One suggestion: If your unit is equipped with a battery disconnect switch, turn off power to the unit so that only the battery is being charged, and power is not being diverted into the camper.


https://a.co/d/1aPsN47

 

[RobbieH]

A $100,000+ motor home should have have a battery isolator. $100 if you don't have one.

Something less exotic like a Off-1-Both-2 battery switch will work too. Maybe $50 for this but you gotta manually switch it.

-- Chuck

Neither my $120,000 Super C nor my $300,000 Monaco Safari had anything on the coach that charged the start battery. I ignored it on my Super C, on the Monaco I installed this:
https://www.rvupgradestore.com/15-Amp-Starting-Battery-Charger-Maintainer-p/amp-l-start.htm

They also make a smaller one called Trick-L-Start

They can be a lifesaver for those who full-time and stay at a single place for an extended time.

Both coaches had a way to use the generator's batteries as start batteries if needed, but I was having issues with those running down too. And it seems that the deep cycle house batteries did not like starting my big Caterpillar.

 

[Flybob]

The Correct answer in Post # 8 by BClemens. He is Mr. Dynamax at Forest River.